diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 49052d375d..8bcf0d0ca3 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -81,7 +81,7 @@ jobs:
 
       - name: Remove OpenTelemetry dependencies on unsupported PHP versions
         if: ${{ matrix.php.version == '7.2' || matrix.php.version == '7.3' || matrix.php.version == '7.4' || matrix.php.version == '8.0' }}
-        run: composer remove open-telemetry/api open-telemetry/exporter-otlp open-telemetry/sdk --dev --no-interaction --no-update
+        run: composer remove open-telemetry/api open-telemetry/exporter-otlp open-telemetry/sem-conv open-telemetry/sdk --dev --no-interaction --no-update
 
       - name: Set phpunit/phpunit version constraint
         run: composer require phpunit/phpunit:'${{ matrix.php.phpunit }}' --dev --no-interaction --no-update
diff --git a/UPGRADE-5.0.md b/UPGRADE-5.0.md
index 578ffaaaaa..92a1f90bc5 100644
--- a/UPGRADE-5.0.md
+++ b/UPGRADE-5.0.md
@@ -21,6 +21,39 @@ $logger->pushHandler(new \Sentry\Monolog\LogsHandler());
 
 To continue sending Monolog records to Sentry issues instead, use `Sentry\Monolog\LogToSentryIssueHandler` for log messages or `Sentry\Monolog\ExceptionToSentryIssueHandler` for exceptions.
 
+### Hub APIs Removed
+
+The Hub API has been removed. This includes:
+
+- **Removed classes and interfaces:**
+  - `Sentry\State\Hub`
+  - `Sentry\State\HubAdapter`
+  - `Sentry\State\HubInterface`
+
+- **Removed methods:**
+  - `SentrySdk::getCurrentHub()`
+  - `SentrySdk::setCurrentHub()`
+
+The SDK now exposes runtime state directly through `SentrySdk`, global helpers, and `Scope`:
+
+```php
+// Before (4.x)
+\Sentry\SentrySdk::getCurrentHub()->configureScope(static function (\Sentry\State\Scope $scope): void {
+    $scope->setTag('feature', 'checkout');
+});
+
+// After (5.0)
+\Sentry\configureScope(static function (\Sentry\State\Scope $scope): void {
+    $scope->setTag('feature', 'checkout');
+});
+```
+
+Use `SentrySdk::getClient()` for the active client, `SentrySdk::getGlobalScope()` for process-global data, and `SentrySdk::getIsolationScope()` for the current runtime isolation scope. Use the capture helpers such as `captureMessage()`, `captureException()`, and `captureEvent()` to send events.
+
+Use `configureScope()` to mutate the current isolation scope, `withIsolationScope()` to run code with a temporary forked scope, and `startTransaction()` to start manual tracing instrumentation.
+
+`SentrySdk::init()` no longer returns a Hub instance. It now returns `void`.
+
 ### Metrics API Removed
 
 The entire Metrics API has been removed as it is no longer supported. This includes:
diff --git a/analysis-baseline.toml b/analysis-baseline.toml
index 2c30c8e024..bb9bc9876e 100644
--- a/analysis-baseline.toml
+++ b/analysis-baseline.toml
@@ -1368,18 +1368,6 @@ code = "possibly-invalid-argument"
 message = '''Possible argument type mismatch for argument #1 of `Sentry\StacktraceBuilder::buildFromBacktrace`: expected `list<array{'args'?: array<array-key, mixed>, 'class'?: class-string, 'file'?: string, 'function'?: string, 'line'?: int, 'type'?: string}>`, but possibly received `array<array-key, mixed>`.'''
 count = 1
 
-[[issues]]
-file = "src/State/Hub.php"
-code = "mixed-operand"
-message = "Right operand in `<` comparison has `mixed` type."
-count = 1
-
-[[issues]]
-file = "src/State/Hub.php"
-code = "possibly-null-operand"
-message = "Left operand in `<` comparison might be `null` (type `float|null`)."
-count = 1
-
 [[issues]]
 file = "src/State/Scope.php"
 code = "impossible-condition"
diff --git a/composer.json b/composer.json
index c545b0bbcf..cce2f1ddb8 100644
--- a/composer.json
+++ b/composer.json
@@ -37,6 +37,7 @@
         "nyholm/psr7": "^1.8",
         "open-telemetry/api": "^1.0",
         "open-telemetry/exporter-otlp": "^1.0",
+        "open-telemetry/sem-conv": "^1.27",
         "open-telemetry/sdk": "^1.0",
         "phpstan/phpstan": "^1.3",
         "phpunit/phpunit": "^8.5.52|^9.6.34",
diff --git a/mago.toml b/mago.toml
index f8b021c004..b4534de5de 100644
--- a/mago.toml
+++ b/mago.toml
@@ -10,3 +10,8 @@ excludes = [
 
 [analyzer]
 baseline = "analysis-baseline.toml"
+ignore = [
+    { code = "no-value", pattern = "DebugType::getDebugType" },
+    "impossible-condition",
+    "redundant-logical-operation",
+]
diff --git a/src/Client.php b/src/Client.php
index 2bb80c7307..9255639e54 100644
--- a/src/Client.php
+++ b/src/Client.php
@@ -10,7 +10,7 @@
 use Sentry\Integration\IntegrationRegistry;
 use Sentry\Serializer\RepresentationSerializer;
 use Sentry\Serializer\RepresentationSerializerInterface;
-use Sentry\State\Scope;
+use Sentry\State\IsolationScope;
 use Sentry\Transport\Result;
 use Sentry\Transport\TransportInterface;
 
@@ -140,7 +140,7 @@ public function getCspReportUrl(): ?string
     /**
      * {@inheritdoc}
      */
-    public function captureMessage(string $message, ?Severity $level = null, ?Scope $scope = null, ?EventHint $hint = null): ?EventId
+    public function captureMessage(string $message, ?Severity $level = null, ?IsolationScope $scope = null, ?EventHint $hint = null): ?EventId
     {
         $event = Event::createEvent();
         $event->setMessage($message);
@@ -152,7 +152,7 @@ public function captureMessage(string $message, ?Severity $level = null, ?Scope
     /**
      * {@inheritdoc}
      */
-    public function captureException(\Throwable $exception, ?Scope $scope = null, ?EventHint $hint = null): ?EventId
+    public function captureException(\Throwable $exception, ?IsolationScope $scope = null, ?EventHint $hint = null): ?EventId
     {
         $className = \get_class($exception);
         if ($this->shouldIgnoreException($className)) {
@@ -176,7 +176,7 @@ public function captureException(\Throwable $exception, ?Scope $scope = null, ?E
     /**
      * {@inheritdoc}
      */
-    public function captureEvent(Event $event, ?EventHint $hint = null, ?Scope $scope = null): ?EventId
+    public function captureEvent(Event $event, ?EventHint $hint = null, ?IsolationScope $scope = null): ?EventId
     {
         // Client reports don't need to be augmented in the prepareEvent pipeline.
         if ($event->getType() !== EventType::clientReport()) {
@@ -208,7 +208,7 @@ public function captureEvent(Event $event, ?EventHint $hint = null, ?Scope $scop
     /**
      * {@inheritdoc}
      */
-    public function captureLastError(?Scope $scope = null, ?EventHint $hint = null): ?EventId
+    public function captureLastError(?IsolationScope $scope = null, ?EventHint $hint = null): ?EventId
     {
         $error = error_get_last();
 
@@ -277,13 +277,13 @@ public function getSdkVersion(): string
     /**
      * Assembles an event and prepares it to be sent of to Sentry.
      *
-     * @param Event          $event The payload that will be converted to an Event
-     * @param EventHint|null $hint  May contain additional information about the event
-     * @param Scope|null     $scope Optional scope which enriches the Event
+     * @param Event               $event The payload that will be converted to an Event
+     * @param EventHint|null      $hint  May contain additional information about the event
+     * @param IsolationScope|null $scope Optional scope which enriches the Event
      *
      * @return Event|null The prepared event object or null if it must be discarded
      */
-    private function prepareEvent(Event $event, ?EventHint $hint = null, ?Scope $scope = null): ?Event
+    private function prepareEvent(Event $event, ?EventHint $hint = null, ?IsolationScope $scope = null): ?Event
     {
         if ($hint !== null) {
             if ($hint->exception !== null && empty($event->getExceptions())) {
@@ -339,7 +339,8 @@ private function prepareEvent(Event $event, ?EventHint $hint = null, ?Scope $sco
 
         if ($scope !== null) {
             $beforeEventProcessors = $event;
-            $event = $scope->applyToEvent($event, $hint, $this->options);
+            $globalScope = SentrySdk::getGlobalScope();
+            $event = $globalScope->merge($scope)->applyToEvent($event, $hint, $this->options);
 
             if ($event === null) {
                 $this->logger->info(
diff --git a/src/ClientInterface.php b/src/ClientInterface.php
index 5d511519f7..8aa245b709 100644
--- a/src/ClientInterface.php
+++ b/src/ClientInterface.php
@@ -5,7 +5,7 @@
 namespace Sentry;
 
 use Sentry\Integration\IntegrationInterface;
-use Sentry\State\Scope;
+use Sentry\State\IsolationScope;
 use Sentry\Transport\Result;
 
 interface ClientInterface
@@ -23,38 +23,38 @@ public function getCspReportUrl(): ?string;
     /**
      * Logs a message.
      *
-     * @param string         $message The message (primary description) for the event
-     * @param Severity|null  $level   The level of the message to be sent
-     * @param Scope|null     $scope   An optional scope keeping the state
-     * @param EventHint|null $hint    Object that can contain additional information about the event
+     * @param string              $message The message (primary description) for the event
+     * @param Severity|null       $level   The level of the message to be sent
+     * @param IsolationScope|null $scope   An optional scope keeping the state
+     * @param EventHint|null      $hint    Object that can contain additional information about the event
      */
-    public function captureMessage(string $message, ?Severity $level = null, ?Scope $scope = null, ?EventHint $hint = null): ?EventId;
+    public function captureMessage(string $message, ?Severity $level = null, ?IsolationScope $scope = null, ?EventHint $hint = null): ?EventId;
 
     /**
      * Logs an exception.
      *
-     * @param \Throwable     $exception The exception object
-     * @param Scope|null     $scope     An optional scope keeping the state
-     * @param EventHint|null $hint      Object that can contain additional information about the event
+     * @param \Throwable          $exception The exception object
+     * @param IsolationScope|null $scope     An optional scope keeping the state
+     * @param EventHint|null      $hint      Object that can contain additional information about the event
      */
-    public function captureException(\Throwable $exception, ?Scope $scope = null, ?EventHint $hint = null): ?EventId;
+    public function captureException(\Throwable $exception, ?IsolationScope $scope = null, ?EventHint $hint = null): ?EventId;
 
     /**
      * Logs the most recent error (obtained with {@link error_get_last}).
      *
-     * @param Scope|null     $scope An optional scope keeping the state
-     * @param EventHint|null $hint  Object that can contain additional information about the event
+     * @param IsolationScope|null $scope An optional scope keeping the state
+     * @param EventHint|null      $hint  Object that can contain additional information about the event
      */
-    public function captureLastError(?Scope $scope = null, ?EventHint $hint = null): ?EventId;
+    public function captureLastError(?IsolationScope $scope = null, ?EventHint $hint = null): ?EventId;
 
     /**
      * Captures a new event using the provided data.
      *
-     * @param Event          $event The event being captured
-     * @param EventHint|null $hint  May contain additional information about the event
-     * @param Scope|null     $scope An optional scope keeping the state
+     * @param Event               $event The event being captured
+     * @param EventHint|null      $hint  May contain additional information about the event
+     * @param IsolationScope|null $scope An optional scope keeping the state
      */
-    public function captureEvent(Event $event, ?EventHint $hint = null, ?Scope $scope = null): ?EventId;
+    public function captureEvent(Event $event, ?EventHint $hint = null, ?IsolationScope $scope = null): ?EventId;
 
     /**
      * Returns the integration instance if it is installed on the client.
diff --git a/src/ClientReport/ClientReportAggregator.php b/src/ClientReport/ClientReportAggregator.php
index 8045a51b2b..454b0ba267 100644
--- a/src/ClientReport/ClientReportAggregator.php
+++ b/src/ClientReport/ClientReportAggregator.php
@@ -5,7 +5,7 @@
 namespace Sentry\ClientReport;
 
 use Sentry\Event;
-use Sentry\State\HubAdapter;
+use Sentry\SentrySdk;
 use Sentry\Transport\DataCategory;
 
 class ClientReportAggregator
@@ -35,15 +35,13 @@ public function add(DataCategory $category, Reason $reason, int $quantity): void
         $category = $category->getValue();
         $reason = $reason->getValue();
         if ($quantity <= 0) {
-            $client = HubAdapter::getInstance()->getClient();
-            if ($client !== null) {
-                $logger = $client->getOptions()->getLoggerOrNullLogger();
-                $logger->debug('Dropping Client report with category={category} and reason={reason} because quantity is zero or negative ({quantity})', [
-                    'category' => $category,
-                    'reason' => $reason,
-                    'quantity' => $quantity,
-                ]);
-            }
+            $client = SentrySdk::getClient();
+            $logger = $client->getOptions()->getLoggerOrNullLogger();
+            $logger->debug('Dropping Client report with category={category} and reason={reason} because quantity is zero or negative ({quantity})', [
+                'category' => $category,
+                'reason' => $reason,
+                'quantity' => $quantity,
+            ]);
 
             return;
         }
@@ -64,11 +62,11 @@ public function flush(): void
         $event = Event::createClientReport();
         $event->setClientReports($reports);
 
-        $client = HubAdapter::getInstance()->getClient();
+        $client = SentrySdk::getClient();
 
         // Reset the client reports only if we successfully sent an event. If it fails it
         // can be sent on the next flush, or it gets discarded anyway.
-        if ($client !== null && $client->captureEvent($event) !== null) {
+        if ($client->captureEvent($event) !== null) {
             $this->reports = [];
         }
     }
diff --git a/src/Integration/AbstractErrorListenerIntegration.php b/src/Integration/AbstractErrorListenerIntegration.php
index a8894a7e29..9b1cc8a0dd 100644
--- a/src/Integration/AbstractErrorListenerIntegration.php
+++ b/src/Integration/AbstractErrorListenerIntegration.php
@@ -5,24 +5,26 @@
 namespace Sentry\Integration;
 
 use Sentry\Event;
+use Sentry\EventHint;
 use Sentry\ExceptionMechanism;
-use Sentry\State\HubInterface;
-use Sentry\State\Scope;
+use Sentry\State\EventRecorder;
+use Sentry\State\IsolationScope;
+
+use function Sentry\withIsolationScope;
 
 abstract class AbstractErrorListenerIntegration implements IntegrationInterface
 {
     /**
-     * Captures the exception using the given hub instance.
-     *
-     * @param HubInterface $hub       The hub instance
-     * @param \Throwable   $exception The exception instance
+     * @param \Throwable $exception The exception instance
      */
-    protected function captureException(HubInterface $hub, \Throwable $exception): void
+    protected function captureException(\Throwable $exception): void
     {
-        $hub->withScope(function (Scope $scope) use ($hub, $exception): void {
-            $scope->addEventProcessor(\Closure::fromCallable([$this, 'addExceptionMechanismToEvent']));
+        withIsolationScope(function (IsolationScope $scope) use ($exception): void {
+            $scope->addEventProcessor(function (Event $event, EventHint $hint): Event {
+                return $this->addExceptionMechanismToEvent($event);
+            });
 
-            $hub->captureException($exception);
+            EventRecorder::captureException($exception, null, $scope);
         });
     }
 
diff --git a/src/Integration/EnvironmentIntegration.php b/src/Integration/EnvironmentIntegration.php
index c404216ea9..adf4f6a53a 100644
--- a/src/Integration/EnvironmentIntegration.php
+++ b/src/Integration/EnvironmentIntegration.php
@@ -24,7 +24,7 @@ final class EnvironmentIntegration implements IntegrationInterface
     public function setupOnce(): void
     {
         Scope::addGlobalEventProcessor(static function (Event $event): Event {
-            $integration = SentrySdk::getCurrentHub()->getIntegration(self::class);
+            $integration = SentrySdk::getClient()->getIntegration(self::class);
 
             if ($integration !== null) {
                 $event->setRuntimeContext($integration->updateRuntimeContext($event->getRuntimeContext()));
diff --git a/src/Integration/ErrorListenerIntegration.php b/src/Integration/ErrorListenerIntegration.php
index a4b95c2ba7..fa33cd2a0c 100644
--- a/src/Integration/ErrorListenerIntegration.php
+++ b/src/Integration/ErrorListenerIntegration.php
@@ -33,24 +33,22 @@ public function setupOnce(): void
         ErrorHandler::registerOnceErrorHandler($this->options)
                     ->addErrorHandlerListener(
                         static function (\ErrorException $exception): void {
-                            $currentHub = SentrySdk::getCurrentHub();
-                            $integration = $currentHub->getIntegration(self::class);
+                            $client = SentrySdk::getClient();
+                            $integration = $client->getIntegration(self::class);
 
                             if ($integration === null) {
                                 return;
                             }
 
-                            $client = $currentHub->getClient();
-
                             if ($exception instanceof SilencedErrorException && !$client->getOptions()->shouldCaptureSilencedErrors()) {
                                 return;
                             }
 
-                            if (!$exception instanceof SilencedErrorException && !($client->getOptions()->getErrorTypes() & $exception->getSeverity())) {
+                            if (!$exception instanceof SilencedErrorException && ($client->getOptions()->getErrorTypes() & $exception->getSeverity()) === 0) {
                                 return;
                             }
 
-                            $integration->captureException($currentHub, $exception);
+                            $integration->captureException($exception);
                         }
                     );
     }
diff --git a/src/Integration/ExceptionListenerIntegration.php b/src/Integration/ExceptionListenerIntegration.php
index 18e7afc757..c86ff02bb2 100644
--- a/src/Integration/ExceptionListenerIntegration.php
+++ b/src/Integration/ExceptionListenerIntegration.php
@@ -20,16 +20,14 @@ public function setupOnce(): void
     {
         $errorHandler = ErrorHandler::registerOnceExceptionHandler();
         $errorHandler->addExceptionHandlerListener(static function (\Throwable $exception): void {
-            $currentHub = SentrySdk::getCurrentHub();
-            $integration = $currentHub->getIntegration(self::class);
+            $client = SentrySdk::getClient();
+            $integration = $client->getIntegration(self::class);
 
-            // The client bound to the current hub, if any, could not have this
-            // integration enabled. If this is the case, bail out
             if ($integration === null) {
                 return;
             }
 
-            $integration->captureException($currentHub, $exception);
+            $integration->captureException($exception);
         });
     }
 }
diff --git a/src/Integration/FatalErrorListenerIntegration.php b/src/Integration/FatalErrorListenerIntegration.php
index 3cc0566688..e4b53c279c 100644
--- a/src/Integration/FatalErrorListenerIntegration.php
+++ b/src/Integration/FatalErrorListenerIntegration.php
@@ -22,20 +22,18 @@ public function setupOnce(): void
     {
         $errorHandler = ErrorHandler::registerOnceFatalErrorHandler();
         $errorHandler->addFatalErrorHandlerListener(static function (FatalErrorException $exception): void {
-            $currentHub = SentrySdk::getCurrentHub();
-            $integration = $currentHub->getIntegration(self::class);
+            $client = SentrySdk::getClient();
+            $integration = $client->getIntegration(self::class);
 
             if ($integration === null) {
                 return;
             }
 
-            $client = $currentHub->getClient();
-
-            if (!($client->getOptions()->getErrorTypes() & $exception->getSeverity())) {
+            if (($client->getOptions()->getErrorTypes() & $exception->getSeverity()) === 0) {
                 return;
             }
 
-            $integration->captureException($currentHub, $exception);
+            $integration->captureException($exception);
         });
     }
 }
diff --git a/src/Integration/FrameContextifierIntegration.php b/src/Integration/FrameContextifierIntegration.php
index 8e55a97278..b7ea13b401 100644
--- a/src/Integration/FrameContextifierIntegration.php
+++ b/src/Integration/FrameContextifierIntegration.php
@@ -41,7 +41,7 @@ public function __construct(?LoggerInterface $logger = null)
     public function setupOnce(): void
     {
         Scope::addGlobalEventProcessor(static function (Event $event): Event {
-            $client = SentrySdk::getCurrentHub()->getClient();
+            $client = SentrySdk::getClient();
 
             $maxContextLines = $client->getOptions()->getContextLines();
             $integration = $client->getIntegration(self::class);
diff --git a/src/Integration/ModulesIntegration.php b/src/Integration/ModulesIntegration.php
index affe1e062b..9e5ee8c164 100644
--- a/src/Integration/ModulesIntegration.php
+++ b/src/Integration/ModulesIntegration.php
@@ -26,10 +26,8 @@ final class ModulesIntegration implements IntegrationInterface
     public function setupOnce(): void
     {
         Scope::addGlobalEventProcessor(static function (Event $event): Event {
-            $integration = SentrySdk::getCurrentHub()->getIntegration(self::class);
+            $integration = SentrySdk::getClient()->getIntegration(self::class);
 
-            // The integration could be bound to a client that is not the one
-            // attached to the current hub. If this is the case, bail out
             if ($integration !== null) {
                 $event->setModules(self::getComposerPackages());
             }
diff --git a/src/Integration/OTLPIntegration.php b/src/Integration/OTLPIntegration.php
index e5e04ef8e2..184d55b50f 100644
--- a/src/Integration/OTLPIntegration.php
+++ b/src/Integration/OTLPIntegration.php
@@ -56,8 +56,7 @@ public function setupOnce(): void
         }
 
         Scope::registerExternalPropagationContext(static function (): ?array {
-            $currentHub = SentrySdk::getCurrentHub();
-            $integration = $currentHub->getIntegration(self::class);
+            $integration = SentrySdk::getClient()->getIntegration(self::class);
 
             if (!$integration instanceof self) {
                 return null;
@@ -193,9 +192,6 @@ private function getLogger(): LoggerInterface
             return $this->options->getLoggerOrNullLogger();
         }
 
-        $currentHub = SentrySdk::getCurrentHub();
-        $client = $currentHub->getClient();
-
-        return $client->getOptions()->getLoggerOrNullLogger();
+        return SentrySdk::getClient()->getOptions()->getLoggerOrNullLogger();
     }
 }
diff --git a/src/Integration/RequestIntegration.php b/src/Integration/RequestIntegration.php
index db123b0198..98aa4ccb3e 100644
--- a/src/Integration/RequestIntegration.php
+++ b/src/Integration/RequestIntegration.php
@@ -103,15 +103,13 @@ public function __construct(?RequestFetcherInterface $requestFetcher = null, arr
     public function setupOnce(): void
     {
         Scope::addGlobalEventProcessor(function (Event $event): Event {
-            $currentHub = SentrySdk::getCurrentHub();
-            $integration = $currentHub->getIntegration(self::class);
+            $client = SentrySdk::getClient();
+            $integration = $client->getIntegration(self::class);
 
             if ($integration === null) {
                 return $event;
             }
 
-            $client = $currentHub->getClient();
-
             $this->processEvent($event, $client->getOptions());
 
             return $event;
diff --git a/src/Integration/TransactionIntegration.php b/src/Integration/TransactionIntegration.php
index 1ed22d7538..13c7bfe51c 100644
--- a/src/Integration/TransactionIntegration.php
+++ b/src/Integration/TransactionIntegration.php
@@ -24,10 +24,8 @@ final class TransactionIntegration implements IntegrationInterface
     public function setupOnce(): void
     {
         Scope::addGlobalEventProcessor(static function (Event $event, EventHint $hint): Event {
-            $integration = SentrySdk::getCurrentHub()->getIntegration(self::class);
+            $integration = SentrySdk::getClient()->getIntegration(self::class);
 
-            // The client bound to the current hub, if any, could not have this
-            // integration enabled. If this is the case, bail out
             if ($integration === null) {
                 return $event;
             }
diff --git a/src/Logs/LogsAggregator.php b/src/Logs/LogsAggregator.php
index 0fa66b7fcb..4bd2c5e77a 100644
--- a/src/Logs/LogsAggregator.php
+++ b/src/Logs/LogsAggregator.php
@@ -6,10 +6,11 @@
 
 use Sentry\Attributes\Attribute;
 use Sentry\Client;
+use Sentry\ClientInterface;
 use Sentry\Event;
 use Sentry\EventId;
 use Sentry\SentrySdk;
-use Sentry\State\HubInterface;
+use Sentry\State\IsolationScope;
 use Sentry\State\Scope;
 use Sentry\Util\Arr;
 use Sentry\Util\Str;
@@ -40,8 +41,10 @@ public function add(
     ): void {
         $timestamp = microtime(true);
 
-        $hub = SentrySdk::getCurrentHub();
-        $client = $hub->getClient();
+        $isolationScope = SentrySdk::getIsolationScope();
+        $client = SentrySdk::getClient($isolationScope);
+        $globalScope = SentrySdk::getGlobalScope();
+        $scope = $globalScope->merge($isolationScope);
 
         $options = $client->getOptions();
         $sdkLogger = $options->getLogger();
@@ -70,7 +73,7 @@ public function add(
             $formattedMessage = $message;
         }
 
-        $traceData = $this->getTraceData($hub);
+        $traceData = $this->getTraceData($isolationScope);
         $traceId = $traceData['trace_id'];
         $parentSpanId = $traceData['parent_span_id'];
 
@@ -85,20 +88,18 @@ public function add(
             $log->setAttribute('sentry.sdk.version', $client->getSdkVersion());
         }
 
-        $hub->configureScope(static function (Scope $scope) use ($log) {
-            $user = $scope->getUser();
-            if ($user !== null) {
-                if ($user->getId() !== null) {
-                    $log->setAttribute('user.id', $user->getId());
-                }
-                if ($user->getEmail() !== null) {
-                    $log->setAttribute('user.email', $user->getEmail());
-                }
-                if ($user->getUsername() !== null) {
-                    $log->setAttribute('user.name', $user->getUsername());
-                }
+        $user = $scope->getUser();
+        if ($user !== null) {
+            if ($user->getId() !== null) {
+                $log->setAttribute('user.id', $user->getId());
+            }
+            if ($user->getEmail() !== null) {
+                $log->setAttribute('user.email', $user->getEmail());
             }
-        });
+            if ($user->getUsername() !== null) {
+                $log->setAttribute('user.name', $user->getUsername());
+            }
+        }
 
         if (\count($values)) {
             $log->setAttribute('sentry.message.template', $message);
@@ -159,20 +160,23 @@ public function add(
         $logs->push($log);
 
         if ($logFlushThreshold !== null && \count($logs) >= $logFlushThreshold) {
-            $this->flush($hub);
+            $this->flush($client);
         }
     }
 
-    public function flush(?HubInterface $hub = null): ?EventId
+    public function flush(?ClientInterface $client = null, ?IsolationScope $isolationScope = null): ?EventId
     {
-        if ($this->logs === null || $this->logs->isEmpty()) {
+        $logs = $this->logs;
+
+        if ($logs === null || $logs->isEmpty()) {
             return null;
         }
 
-        $hub = $hub ?? SentrySdk::getCurrentHub();
-        $event = Event::createLogs()->setLogs($this->logs->drain());
+        $isolationScope = $isolationScope ?? SentrySdk::getIsolationScope();
+        $client = $client ?? SentrySdk::getClient($isolationScope);
+        $event = Event::createLogs()->setLogs($logs->drain());
 
-        return $hub->captureEvent($event);
+        return $client->captureEvent($event, null, $isolationScope);
     }
 
     /**
@@ -186,9 +190,9 @@ public function all(): array
     /**
      * @return array{trace_id: string, parent_span_id: string|null}
      */
-    private function getTraceData(HubInterface $hub): array
+    private function getTraceData(IsolationScope $scope): array
     {
-        $span = $hub->getSpan();
+        $span = $scope->getSpan();
 
         if ($span !== null) {
             return [
@@ -197,28 +201,18 @@ private function getTraceData(HubInterface $hub): array
             ];
         }
 
-        $traceData = null;
-
-        $hub->configureScope(static function (Scope $scope) use (&$traceData): void {
-            $externalPropagationContext = Scope::getExternalPropagationContext();
-
-            if ($externalPropagationContext !== null) {
-                $traceData = [
-                    'trace_id' => $externalPropagationContext['trace_id'],
-                    'parent_span_id' => $externalPropagationContext['span_id'],
-                ];
-
-                return;
-            }
-
-            $traceData = [
-                'trace_id' => (string) $scope->getPropagationContext()->getTraceId(),
-                'parent_span_id' => null,
+        $externalPropagationContext = Scope::getExternalPropagationContext();
+        if ($externalPropagationContext !== null) {
+            return [
+                'trace_id' => $externalPropagationContext['trace_id'],
+                'parent_span_id' => $externalPropagationContext['span_id'],
             ];
-        });
+        }
 
-        /** @var array{trace_id: string, parent_span_id: string|null} $traceData */
-        return $traceData;
+        return [
+            'trace_id' => (string) $scope->getPropagationContext()->getTraceId(),
+            'parent_span_id' => null,
+        ];
     }
 
     /**
diff --git a/src/Metrics/MetricsAggregator.php b/src/Metrics/MetricsAggregator.php
index a4a3aef3e4..f4519da1c4 100644
--- a/src/Metrics/MetricsAggregator.php
+++ b/src/Metrics/MetricsAggregator.php
@@ -5,6 +5,7 @@
 namespace Sentry\Metrics;
 
 use Sentry\Client;
+use Sentry\ClientInterface;
 use Sentry\Event;
 use Sentry\EventId;
 use Sentry\Metrics\Types\CounterMetric;
@@ -12,8 +13,7 @@
 use Sentry\Metrics\Types\GaugeMetric;
 use Sentry\Metrics\Types\Metric;
 use Sentry\SentrySdk;
-use Sentry\State\HubInterface;
-use Sentry\State\Scope;
+use Sentry\State\IsolationScope;
 use Sentry\Tracing\SpanId;
 use Sentry\Tracing\TraceId;
 use Sentry\Unit;
@@ -51,60 +51,54 @@ public function add(
         array $attributes,
         ?Unit $unit
     ): void {
-        $hub = SentrySdk::getCurrentHub();
-        $client = $hub->getClient();
-        $metricFlushThreshold = null;
+        $isolationScope = SentrySdk::getIsolationScope();
+        $client = SentrySdk::getClient($isolationScope);
+        $globalScope = SentrySdk::getGlobalScope();
+        $scope = $globalScope->merge($isolationScope);
+        $options = $client->getOptions();
+        $metricFlushThreshold = $options->getMetricFlushThreshold();
 
         if (!\is_int($value) && !\is_float($value)) {
-            if ($client !== null) {
-                $client->getOptions()->getLoggerOrNullLogger()->debug('Metrics value is neither int nor float. Metric will be discarded');
-            }
+            $options->getLoggerOrNullLogger()->debug('Metrics value is neither int nor float. Metric will be discarded');
 
             return;
         }
 
-        if ($client !== null) {
-            $options = $client->getOptions();
-            $metricFlushThreshold = $options->getMetricFlushThreshold();
+        if ($options->getEnableMetrics() === false) {
+            return;
+        }
 
-            if ($options->getEnableMetrics() === false) {
-                return;
-            }
+        $defaultAttributes = [
+            'sentry.environment' => $options->getEnvironment() ?? Event::DEFAULT_ENVIRONMENT,
+            'server.address' => $options->getServerName(),
+        ];
 
-            $defaultAttributes = [
-                'sentry.environment' => $options->getEnvironment() ?? Event::DEFAULT_ENVIRONMENT,
-                'server.address' => $options->getServerName(),
-            ];
+        if ($client instanceof Client) {
+            $defaultAttributes['sentry.sdk.name'] = $client->getSdkIdentifier();
+            $defaultAttributes['sentry.sdk.version'] = $client->getSdkVersion();
+        }
 
-            if ($client instanceof Client) {
-                $defaultAttributes['sentry.sdk.name'] = $client->getSdkIdentifier();
-                $defaultAttributes['sentry.sdk.version'] = $client->getSdkVersion();
+        $user = $scope->getUser();
+        if ($user !== null) {
+            if ($user->getId() !== null) {
+                $defaultAttributes['user.id'] = $user->getId();
             }
-
-            $hub->configureScope(static function (Scope $scope) use (&$defaultAttributes) {
-                $user = $scope->getUser();
-                if ($user !== null) {
-                    if ($user->getId() !== null) {
-                        $defaultAttributes['user.id'] = $user->getId();
-                    }
-                    if ($user->getEmail() !== null) {
-                        $defaultAttributes['user.email'] = $user->getEmail();
-                    }
-                    if ($user->getUsername() !== null) {
-                        $defaultAttributes['user.name'] = $user->getUsername();
-                    }
-                }
-            });
-
-            $release = $options->getRelease();
-            if ($release !== null) {
-                $defaultAttributes['sentry.release'] = $release;
+            if ($user->getEmail() !== null) {
+                $defaultAttributes['user.email'] = $user->getEmail();
+            }
+            if ($user->getUsername() !== null) {
+                $defaultAttributes['user.name'] = $user->getUsername();
             }
+        }
 
-            $attributes += $defaultAttributes;
+        $release = $options->getRelease();
+        if ($release !== null) {
+            $defaultAttributes['sentry.release'] = $release;
         }
 
-        $traceContext = $this->getTraceContext($hub);
+        $attributes += $defaultAttributes;
+
+        $traceContext = $this->getTraceContext($isolationScope);
         $traceId = new TraceId($traceContext['trace_id']);
         $spanId = new SpanId($traceContext['span_id']);
 
@@ -112,47 +106,46 @@ public function add(
         /** @var Metric $metric */
         $metric = new $metricTypeClass($name, $value, $traceId, $spanId, $attributes, microtime(true), $unit);
 
-        if ($client !== null) {
-            $beforeSendMetric = $client->getOptions()->getBeforeSendMetricCallback();
-            $metric = $beforeSendMetric($metric);
-            if ($metric === null) {
-                return;
-            }
+        $beforeSendMetric = $options->getBeforeSendMetricCallback();
+        $metric = $beforeSendMetric($metric);
+        if ($metric === null) {
+            return;
         }
 
         $metrics = $this->getStorage($metricFlushThreshold);
         $metrics->push($metric);
 
         if ($metricFlushThreshold !== null && \count($metrics) >= $metricFlushThreshold) {
-            $this->flush($hub);
+            $this->flush($client);
         }
     }
 
-    public function flush(?HubInterface $hub = null): ?EventId
+    public function flush(?ClientInterface $client = null, ?IsolationScope $isolationScope = null): ?EventId
     {
-        if ($this->metrics === null || $this->metrics->isEmpty()) {
+        $metrics = $this->metrics;
+
+        if ($metrics === null || $metrics->isEmpty()) {
             return null;
         }
 
-        $hub = $hub ?? SentrySdk::getCurrentHub();
-        $event = Event::createMetrics()->setMetrics($this->metrics->drain());
+        $isolationScope = $isolationScope ?? SentrySdk::getIsolationScope();
+        $client = $client ?? SentrySdk::getClient($isolationScope);
+        $event = Event::createMetrics()->setMetrics($metrics->drain());
 
-        return $hub->captureEvent($event);
+        return $client->captureEvent($event, null, $isolationScope);
     }
 
     /**
      * @return array{trace_id: string, span_id: string}
      */
-    private function getTraceContext(HubInterface $hub): array
+    private function getTraceContext(IsolationScope $scope): array
     {
-        $traceContext = null;
-
-        $hub->configureScope(static function (Scope $scope) use (&$traceContext): void {
-            $traceContext = $scope->getTraceContext();
-        });
+        $traceContext = $scope->getTraceContext();
 
-        /** @var array{trace_id: string, span_id: string} $traceContext */
-        return $traceContext;
+        return [
+            'trace_id' => $traceContext['trace_id'],
+            'span_id' => $traceContext['span_id'],
+        ];
     }
 
     /**
diff --git a/src/Monolog/BreadcrumbHandler.php b/src/Monolog/BreadcrumbHandler.php
index 29e166671b..9fd3538bf6 100644
--- a/src/Monolog/BreadcrumbHandler.php
+++ b/src/Monolog/BreadcrumbHandler.php
@@ -11,33 +11,26 @@
 use Psr\Log\LogLevel;
 use Sentry\Breadcrumb;
 use Sentry\Event;
-use Sentry\State\HubInterface;
-use Sentry\State\Scope;
+use Sentry\SentrySdk;
+use Sentry\State\BreadcrumbRecorder;
+use Sentry\State\IsolationScope;
 
 /**
- * This Monolog handler logs every message as a {@see Breadcrumb} into the current {@see Scope},
+ * This Monolog handler logs every message as a {@see Breadcrumb} into the current {@see IsolationScope},
  * to enrich any event sent to Sentry.
  */
 final class BreadcrumbHandler extends AbstractProcessingHandler
 {
     /**
-     * @var HubInterface
-     */
-    private $hub;
-
-    /**
-     * @param HubInterface $hub    The hub to which errors are reported
-     * @param int|string   $level  The minimum logging level at which this
-     *                             handler will be triggered
-     * @param bool         $bubble Whether the messages that are handled can
-     *                             bubble up the stack or not
+     * @param int|string $level  The minimum logging level at which this
+     *                           handler will be triggered
+     * @param bool       $bubble Whether the messages that are handled can
+     *                           bubble up the stack or not
      *
      * @phpstan-param int|string|Level|LogLevel::* $level
      */
-    public function __construct(HubInterface $hub, $level = Logger::DEBUG, bool $bubble = true)
+    public function __construct($level = Logger::DEBUG, bool $bubble = true)
     {
-        $this->hub = $hub;
-
         parent::__construct($level, $bubble);
     }
 
@@ -66,7 +59,8 @@ protected function write($record): void
             $timestamp
         );
 
-        $this->hub->addBreadcrumb($breadcrumb);
+        $scope = SentrySdk::getIsolationScope();
+        BreadcrumbRecorder::record(SentrySdk::getClient($scope), $scope, $breadcrumb);
     }
 
     /**
diff --git a/src/Monolog/ExceptionToSentryIssueHandler.php b/src/Monolog/ExceptionToSentryIssueHandler.php
index b2e7abeb6b..5173631d56 100644
--- a/src/Monolog/ExceptionToSentryIssueHandler.php
+++ b/src/Monolog/ExceptionToSentryIssueHandler.php
@@ -9,26 +9,21 @@
 use Monolog\Logger;
 use Monolog\LogRecord;
 use Psr\Log\LogLevel;
-use Sentry\State\HubInterface;
-use Sentry\State\Scope;
+use Sentry\State\EventRecorder;
+use Sentry\State\IsolationScope;
+
+use function Sentry\withIsolationScope;
 
 /**
  * This Monolog handler will collect monolog events and send them to sentry.
  */
 class ExceptionToSentryIssueHandler extends AbstractHandler
 {
-    /**
-     * @var HubInterface
-     */
-    private $hub;
-
     /**
      * @phpstan-param value-of<Level::VALUES>|value-of<Level::NAMES>|Level|LogLevel::* $level
      */
-    public function __construct(HubInterface $hub, $level = Logger::DEBUG, bool $bubble = true)
+    public function __construct($level = Logger::DEBUG, bool $bubble = true)
     {
-        $this->hub = $hub;
-
         parent::__construct($level, $bubble);
     }
 
@@ -44,7 +39,7 @@ public function handle($record): bool
             return false;
         }
 
-        $this->hub->withScope(function (Scope $scope) use ($record, $exception): void {
+        withIsolationScope(function (IsolationScope $scope) use ($record, $exception): void {
             $scope->setExtra('monolog.channel', $record['channel']);
             $scope->setExtra('monolog.level', $record['level_name']);
             $scope->setExtra('monolog.message', $record['message']);
@@ -61,7 +56,7 @@ public function handle($record): bool
                 $scope->setExtra('monolog.extra', $monologExtraData);
             }
 
-            $this->hub->captureException($exception);
+            EventRecorder::captureException($exception, null, $scope);
         });
 
         return $this->bubble === false;
diff --git a/src/Monolog/LogToSentryIssueHandler.php b/src/Monolog/LogToSentryIssueHandler.php
index 18dd6eab61..2866d32afb 100644
--- a/src/Monolog/LogToSentryIssueHandler.php
+++ b/src/Monolog/LogToSentryIssueHandler.php
@@ -11,8 +11,10 @@
 use Psr\Log\LogLevel;
 use Sentry\Event;
 use Sentry\EventHint;
-use Sentry\State\HubInterface;
-use Sentry\State\Scope;
+use Sentry\State\EventRecorder;
+use Sentry\State\IsolationScope;
+
+use function Sentry\withIsolationScope;
 
 /**
  * This Monolog handler captures log messages as Sentry issues.
@@ -23,11 +25,6 @@ class LogToSentryIssueHandler extends AbstractProcessingHandler
 
     private const CONTEXT_EXCEPTION_KEY = 'exception';
 
-    /**
-     * @var HubInterface
-     */
-    private $hub;
-
     /**
      * @var bool
      */
@@ -36,9 +33,8 @@ class LogToSentryIssueHandler extends AbstractProcessingHandler
     /**
      * @phpstan-param value-of<Level::VALUES>|value-of<Level::NAMES>|Level|LogLevel::* $level
      */
-    public function __construct(HubInterface $hub, $level = Logger::DEBUG, bool $bubble = true, bool $fillExtraContext = false)
+    public function __construct($level = Logger::DEBUG, bool $bubble = true, bool $fillExtraContext = false)
     {
-        $this->hub = $hub;
         $this->fillExtraContext = $fillExtraContext;
 
         parent::__construct($level, $bubble);
@@ -70,7 +66,7 @@ protected function doWrite($record): void
 
         $hint = new EventHint();
 
-        $this->hub->withScope(function (Scope $scope) use ($record, $event, $hint): void {
+        withIsolationScope(function (IsolationScope $scope) use ($record, $event, $hint): void {
             $scope->setExtra('monolog.channel', $record['channel']);
             $scope->setExtra('monolog.level', $record['level_name']);
 
@@ -88,7 +84,7 @@ protected function doWrite($record): void
                 }
             }
 
-            $this->hub->captureEvent($event, $hint);
+            EventRecorder::captureEvent($event, $hint, $scope);
         });
     }
 
diff --git a/src/NoOpClient.php b/src/NoOpClient.php
index 364b6073e3..acf238b0de 100644
--- a/src/NoOpClient.php
+++ b/src/NoOpClient.php
@@ -6,7 +6,7 @@
 
 use Sentry\Integration\IntegrationInterface;
 use Sentry\Serializer\RepresentationSerializer;
-use Sentry\State\Scope;
+use Sentry\State\IsolationScope;
 use Sentry\Transport\Result;
 use Sentry\Transport\ResultStatus;
 
@@ -54,22 +54,22 @@ public function getCspReportUrl(): ?string
         return null;
     }
 
-    public function captureMessage(string $message, ?Severity $level = null, ?Scope $scope = null, ?EventHint $hint = null): ?EventId
+    public function captureMessage(string $message, ?Severity $level = null, ?IsolationScope $scope = null, ?EventHint $hint = null): ?EventId
     {
         return null;
     }
 
-    public function captureException(\Throwable $exception, ?Scope $scope = null, ?EventHint $hint = null): ?EventId
+    public function captureException(\Throwable $exception, ?IsolationScope $scope = null, ?EventHint $hint = null): ?EventId
     {
         return null;
     }
 
-    public function captureLastError(?Scope $scope = null, ?EventHint $hint = null): ?EventId
+    public function captureLastError(?IsolationScope $scope = null, ?EventHint $hint = null): ?EventId
     {
         return null;
     }
 
-    public function captureEvent(Event $event, ?EventHint $hint = null, ?Scope $scope = null): ?EventId
+    public function captureEvent(Event $event, ?EventHint $hint = null, ?IsolationScope $scope = null): ?EventId
     {
         return null;
     }
diff --git a/src/SentrySdk.php b/src/SentrySdk.php
index 9adce8c282..8145c82695 100644
--- a/src/SentrySdk.php
+++ b/src/SentrySdk.php
@@ -6,8 +6,8 @@
 
 use Sentry\Logs\Logs;
 use Sentry\Metrics\TraceMetrics;
-use Sentry\State\Hub;
-use Sentry\State\HubInterface;
+use Sentry\State\GlobalScope;
+use Sentry\State\IsolationScope;
 use Sentry\State\RuntimeContext;
 use Sentry\State\RuntimeContextManager;
 
@@ -19,9 +19,9 @@
 final class SentrySdk
 {
     /**
-     * @var HubInterface|null The baseline hub
+     * @var GlobalScope|null The process-global scope
      */
-    private static $currentHub;
+    private static $globalScope;
 
     /**
      * @var RuntimeContextManager|null
@@ -36,47 +36,45 @@ private function __construct()
     }
 
     /**
-     * Initializes the SDK by creating a new hub instance each time this method
-     * gets called.
+     * Initializes the SDK by binding the client to the global scope and resetting
+     * the current local runtime state.
      */
-    public static function init(?ClientInterface $client = null): HubInterface
+    public static function init(?ClientInterface $client = null): void
     {
-        if ($client === null) {
-            $client = new NoOpClient();
+        if ($client !== null) {
+            self::getGlobalScope()->setClient($client);
+        }
+        self::$runtimeContextManager = new RuntimeContextManager();
+    }
+
+    public static function getGlobalScope(): GlobalScope
+    {
+        if (self::$globalScope === null) {
+            self::$globalScope = new GlobalScope();
         }
-        self::$currentHub = new Hub($client);
-        self::$runtimeContextManager = new RuntimeContextManager(self::$currentHub);
 
-        return self::getCurrentHub();
+        return self::$globalScope;
     }
 
-    /**
-     * Gets the current hub. If it's not initialized then creates a new instance
-     * and sets it as current hub.
-     */
-    public static function getCurrentHub(): HubInterface
+    public static function getIsolationScope(): IsolationScope
     {
-        return self::getRuntimeContextManager()->getCurrentHub();
+        return self::getCurrentRuntimeContext()->getIsolationScope();
     }
 
-    /**
-     * Sets the current hub.
-     *
-     * If called while an explicit runtime context is active, the hub update is
-     * scoped to that active context only. Otherwise, it updates the baseline
-     * hub used by the global fallback context and future contexts.
-     *
-     * @param HubInterface $hub The hub to set
-     */
-    public static function setCurrentHub(HubInterface $hub): HubInterface
+    public static function getLastEventId(): ?EventId
     {
-        $wasSetOnActiveRuntimeContext = self::getRuntimeContextManager()->setCurrentHub($hub);
+        return self::getCurrentRuntimeContext()->getLastEventId();
+    }
 
-        if (!$wasSetOnActiveRuntimeContext) {
-            self::$currentHub = $hub;
+    public static function getClient(?IsolationScope $isolationScope = null): ClientInterface
+    {
+        $client = ($isolationScope ?? self::getIsolationScope())->getClient();
+
+        if (!$client instanceof NoOpClient) {
+            return $client;
         }
 
-        return $hub;
+        return self::getGlobalScope()->getClient();
     }
 
     public static function startContext(): void
@@ -148,18 +146,13 @@ public static function flush(): void
         Logs::getInstance()->flush();
         TraceMetrics::getInstance()->flush();
 
-        $client = self::getCurrentHub()->getClient();
-        $client->flush();
+        self::getClient()->flush();
     }
 
     private static function getRuntimeContextManager(): RuntimeContextManager
     {
-        if (self::$currentHub === null) {
-            self::$currentHub = new Hub(new NoOpClient());
-        }
-
         if (self::$runtimeContextManager === null) {
-            self::$runtimeContextManager = new RuntimeContextManager(self::$currentHub);
+            self::$runtimeContextManager = new RuntimeContextManager();
         }
 
         return self::$runtimeContextManager;
diff --git a/src/State/BreadcrumbRecorder.php b/src/State/BreadcrumbRecorder.php
new file mode 100644
index 0000000000..d3bfe25a4b
--- /dev/null
+++ b/src/State/BreadcrumbRecorder.php
@@ -0,0 +1,44 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Sentry\State;
+
+use Sentry\Breadcrumb;
+use Sentry\ClientInterface;
+use Sentry\NoOpClient;
+
+/**
+ * @internal
+ */
+final class BreadcrumbRecorder
+{
+    private function __construct()
+    {
+    }
+
+    /**
+     * Records the breadcrumb on the given scope if the client configuration allows it.
+     */
+    public static function record(ClientInterface $client, IsolationScope $scope, Breadcrumb $breadcrumb): bool
+    {
+        if ($client instanceof NoOpClient) {
+            return false;
+        }
+
+        $options = $client->getOptions();
+        $maxBreadcrumbs = $options->getMaxBreadcrumbs();
+
+        if ($maxBreadcrumbs <= 0) {
+            return false;
+        }
+
+        $breadcrumb = ($options->getBeforeBreadcrumbCallback())($breadcrumb);
+
+        if ($breadcrumb !== null) {
+            $scope->addBreadcrumb($breadcrumb, $maxBreadcrumbs);
+        }
+
+        return $breadcrumb !== null;
+    }
+}
diff --git a/src/State/EventRecorder.php b/src/State/EventRecorder.php
new file mode 100644
index 0000000000..cd417ed6aa
--- /dev/null
+++ b/src/State/EventRecorder.php
@@ -0,0 +1,109 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Sentry\State;
+
+use Sentry\CheckIn;
+use Sentry\CheckInStatus;
+use Sentry\ClientInterface;
+use Sentry\Event;
+use Sentry\EventHint;
+use Sentry\EventId;
+use Sentry\MonitorConfig;
+use Sentry\NoOpClient;
+use Sentry\SentrySdk;
+use Sentry\Severity;
+
+/**
+ * @internal
+ */
+final class EventRecorder
+{
+    private function __construct()
+    {
+    }
+
+    public static function captureMessage(string $message, ?Severity $level = null, ?EventHint $hint = null, ?IsolationScope $isolationScope = null): ?EventId
+    {
+        $isolationScope = $isolationScope ?? SentrySdk::getIsolationScope();
+
+        return self::captureWithScope(SentrySdk::getClient($isolationScope), $isolationScope, static function (ClientInterface $client, IsolationScope $captureScope) use ($message, $level, $hint): ?EventId {
+            return $client->captureMessage($message, $level, $captureScope, $hint);
+        });
+    }
+
+    public static function captureException(\Throwable $exception, ?EventHint $hint = null, ?IsolationScope $isolationScope = null): ?EventId
+    {
+        $isolationScope = $isolationScope ?? SentrySdk::getIsolationScope();
+
+        return self::captureWithScope(SentrySdk::getClient($isolationScope), $isolationScope, static function (ClientInterface $client, IsolationScope $captureScope) use ($exception, $hint): ?EventId {
+            return $client->captureException($exception, $captureScope, $hint);
+        });
+    }
+
+    public static function captureEvent(Event $event, ?EventHint $hint = null, ?IsolationScope $isolationScope = null): ?EventId
+    {
+        $isolationScope = $isolationScope ?? SentrySdk::getIsolationScope();
+
+        return self::captureWithScope(SentrySdk::getClient($isolationScope), $isolationScope, static function (ClientInterface $client, IsolationScope $captureScope) use ($event, $hint): ?EventId {
+            return $client->captureEvent($event, $hint, $captureScope);
+        });
+    }
+
+    public static function captureLastError(?EventHint $hint = null, ?IsolationScope $isolationScope = null): ?EventId
+    {
+        $isolationScope = $isolationScope ?? SentrySdk::getIsolationScope();
+
+        return self::captureWithScope(SentrySdk::getClient($isolationScope), $isolationScope, static function (ClientInterface $client, IsolationScope $captureScope) use ($hint): ?EventId {
+            return $client->captureLastError($captureScope, $hint);
+        });
+    }
+
+    /**
+     * @param int|float|null $duration
+     */
+    public static function captureCheckIn(string $slug, CheckInStatus $status, $duration = null, ?MonitorConfig $monitorConfig = null, ?string $checkInId = null, ?IsolationScope $isolationScope = null): ?string
+    {
+        $isolationScope = $isolationScope ?? SentrySdk::getIsolationScope();
+        $client = SentrySdk::getClient($isolationScope);
+
+        if ($client instanceof NoOpClient) {
+            return null;
+        }
+
+        $options = $client->getOptions();
+        $event = Event::createCheckIn();
+        $checkIn = new CheckIn(
+            $slug,
+            $status,
+            $checkInId,
+            $options->getRelease(),
+            $options->getEnvironment(),
+            $duration,
+            $monitorConfig
+        );
+        $event->setCheckIn($checkIn);
+
+        self::captureWithScope($client, $isolationScope, static function (ClientInterface $client, IsolationScope $captureScope) use ($event): ?EventId {
+            return $client->captureEvent($event, null, $captureScope);
+        });
+
+        return $checkIn->getId();
+    }
+
+    /**
+     * @param callable(ClientInterface, IsolationScope): ?EventId $capture
+     */
+    private static function captureWithScope(ClientInterface $client, IsolationScope $isolationScope, callable $capture): ?EventId
+    {
+        if ($client instanceof NoOpClient) {
+            return null;
+        }
+
+        $eventId = $capture($client, $isolationScope);
+        SentrySdk::getCurrentRuntimeContext()->setLastEventId($eventId);
+
+        return $eventId;
+    }
+}
diff --git a/src/State/GlobalScope.php b/src/State/GlobalScope.php
new file mode 100644
index 0000000000..7483b22d6d
--- /dev/null
+++ b/src/State/GlobalScope.php
@@ -0,0 +1,20 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Sentry\State;
+
+/**
+ * The scope holds data that should implicitly be sent with Sentry events. It
+ * can hold context data, extra parameters, level overrides, fingerprints etc.
+ */
+class GlobalScope extends MutableScope
+{
+    /**
+     * @internal
+     */
+    public function merge(IsolationScope $scope): MergedScope
+    {
+        return new MergedScope($this->scopeData->merge($scope->scopeData), $scope->getSpan());
+    }
+}
diff --git a/src/State/Hub.php b/src/State/Hub.php
deleted file mode 100644
index e9132531e0..0000000000
--- a/src/State/Hub.php
+++ /dev/null
@@ -1,425 +0,0 @@
-<?php
-
-declare(strict_types=1);
-
-namespace Sentry\State;
-
-use Sentry\Attachment\Attachment;
-use Sentry\Breadcrumb;
-use Sentry\CheckIn;
-use Sentry\CheckInStatus;
-use Sentry\ClientInterface;
-use Sentry\Event;
-use Sentry\EventHint;
-use Sentry\EventId;
-use Sentry\Integration\IntegrationInterface;
-use Sentry\MonitorConfig;
-use Sentry\NoOpClient;
-use Sentry\Severity;
-use Sentry\Tracing\SamplingContext;
-use Sentry\Tracing\Span;
-use Sentry\Tracing\Transaction;
-use Sentry\Tracing\TransactionContext;
-
-/**
- * This class is a basic implementation of the {@see HubInterface} interface.
- */
-class Hub implements HubInterface
-{
-    /**
-     * @var Layer[] The stack of client/scope pairs
-     */
-    private $stack = [];
-
-    /**
-     * @var EventId|null The ID of the last captured event
-     */
-    private $lastEventId;
-
-    /**
-     * Hub constructor.
-     *
-     * @param ClientInterface $client The client bound to the hub
-     * @param Scope|null      $scope  The scope bound to the hub
-     */
-    public function __construct(ClientInterface $client, ?Scope $scope = null)
-    {
-        $this->stack[] = new Layer($client, $scope ?? new Scope());
-    }
-
-    /**
-     * {@inheritdoc}
-     */
-    public function getClient(): ClientInterface
-    {
-        return $this->getStackTop()->getClient();
-    }
-
-    /**
-     * {@inheritdoc}
-     */
-    public function getLastEventId(): ?EventId
-    {
-        return $this->lastEventId;
-    }
-
-    /**
-     * {@inheritdoc}
-     */
-    public function pushScope(): Scope
-    {
-        $clonedScope = clone $this->getScope();
-
-        $this->stack[] = new Layer($this->getClient(), $clonedScope);
-
-        return $clonedScope;
-    }
-
-    /**
-     * {@inheritdoc}
-     */
-    public function popScope(): bool
-    {
-        if (\count($this->stack) === 1) {
-            return false;
-        }
-
-        return array_pop($this->stack) !== null;
-    }
-
-    /**
-     * {@inheritdoc}
-     */
-    public function withScope(callable $callback)
-    {
-        $scope = $this->pushScope();
-
-        try {
-            return $callback($scope);
-        } finally {
-            $this->popScope();
-        }
-    }
-
-    /**
-     * {@inheritdoc}
-     */
-    public function configureScope(callable $callback): void
-    {
-        $callback($this->getScope());
-    }
-
-    /**
-     * {@inheritdoc}
-     */
-    public function bindClient(ClientInterface $client): void
-    {
-        $layer = $this->getStackTop();
-        $layer->setClient($client);
-    }
-
-    /**
-     * {@inheritdoc}
-     */
-    public function captureMessage(string $message, ?Severity $level = null, ?EventHint $hint = null): ?EventId
-    {
-        return $this->lastEventId = $this->getClient()->captureMessage($message, $level, $this->getScope(), $hint);
-    }
-
-    /**
-     * {@inheritdoc}
-     */
-    public function captureException(\Throwable $exception, ?EventHint $hint = null): ?EventId
-    {
-        return $this->lastEventId = $this->getClient()->captureException($exception, $this->getScope(), $hint);
-    }
-
-    /**
-     * {@inheritdoc}
-     */
-    public function captureEvent(Event $event, ?EventHint $hint = null): ?EventId
-    {
-        return $this->lastEventId = $this->getClient()->captureEvent($event, $hint, $this->getScope());
-    }
-
-    /**
-     * {@inheritdoc}
-     */
-    public function captureLastError(?EventHint $hint = null): ?EventId
-    {
-        return $this->lastEventId = $this->getClient()->captureLastError($this->getScope(), $hint);
-    }
-
-    /**
-     * {@inheritdoc}
-     *
-     * @param int|float|null $duration
-     */
-    public function captureCheckIn(string $slug, CheckInStatus $status, $duration = null, ?MonitorConfig $monitorConfig = null, ?string $checkInId = null): ?string
-    {
-        $client = $this->getClient();
-
-        if ($client instanceof NoOpClient) {
-            return null;
-        }
-
-        $options = $client->getOptions();
-        $event = Event::createCheckIn();
-        $checkIn = new CheckIn(
-            $slug,
-            $status,
-            $checkInId,
-            $options->getRelease(),
-            $options->getEnvironment(),
-            $duration,
-            $monitorConfig
-        );
-        $event->setCheckIn($checkIn);
-        $this->captureEvent($event);
-
-        return $checkIn->getId();
-    }
-
-    /**
-     * {@inheritdoc}
-     */
-    public function addBreadcrumb(Breadcrumb $breadcrumb): bool
-    {
-        $client = $this->getClient();
-
-        // No point in storing breadcrumbs if the client will never send them
-        if ($client instanceof NoOpClient) {
-            return false;
-        }
-
-        $options = $client->getOptions();
-        $beforeBreadcrumbCallback = $options->getBeforeBreadcrumbCallback();
-        $maxBreadcrumbs = $options->getMaxBreadcrumbs();
-
-        if ($maxBreadcrumbs <= 0) {
-            return false;
-        }
-
-        $breadcrumb = $beforeBreadcrumbCallback($breadcrumb);
-
-        if ($breadcrumb !== null) {
-            $this->getScope()->addBreadcrumb($breadcrumb, $maxBreadcrumbs);
-        }
-
-        return $breadcrumb !== null;
-    }
-
-    public function addAttachment(Attachment $attachment): bool
-    {
-        // No point in storing attachments if the client will never send them
-        if ($this->getClient() instanceof NoOpClient) {
-            return false;
-        }
-
-        $this->getScope()->addAttachment($attachment);
-
-        return true;
-    }
-
-    /**
-     * {@inheritdoc}
-     */
-    public function getIntegration(string $className): ?IntegrationInterface
-    {
-        return $this->getClient()->getIntegration($className);
-    }
-
-    /**
-     * {@inheritdoc}
-     *
-     * @param array<string, mixed> $customSamplingContext Additional context that will be passed to the {@see SamplingContext}
-     */
-    public function startTransaction(TransactionContext $context, array $customSamplingContext = []): Transaction
-    {
-        $transaction = new Transaction($context, $this);
-        $options = $this->getClient()->getOptions();
-        $logger = $options->getLoggerOrNullLogger();
-
-        if (!$options->isTracingEnabled()) {
-            $transaction->setSampled(false);
-
-            $logger->warning(\sprintf('Transaction [%s] was started but tracing is not enabled.', (string) $transaction->getTraceId()), ['context' => $context]);
-
-            return $transaction;
-        }
-
-        $samplingContext = SamplingContext::getDefault($context);
-        $samplingContext->setAdditionalContext($customSamplingContext);
-
-        $sampleSource = 'context';
-        $sampleRand = $context->getMetadata()->getSampleRand();
-
-        if ($transaction->getSampled() === null) {
-            $tracesSampler = $options->getTracesSampler();
-
-            if ($tracesSampler !== null) {
-                $sampleRate = $tracesSampler($samplingContext);
-                $sampleSource = 'config:traces_sampler';
-            } else {
-                $parentSampleRate = $context->getMetadata()->getParentSamplingRate();
-                if ($parentSampleRate !== null) {
-                    $sampleRate = $parentSampleRate;
-                    $sampleSource = 'parent:sample_rate';
-                } else {
-                    $sampleRate = $this->getSampleRate(
-                        $samplingContext->getParentSampled(),
-                        $options->getTracesSampleRate() ?? 0
-                    );
-                    $sampleSource = $samplingContext->getParentSampled() !== null ? 'parent:sampling_decision' : 'config:traces_sample_rate';
-                }
-            }
-
-            if (!$this->isValidSampleRate($sampleRate)) {
-                $transaction->setSampled(false);
-
-                $logger->warning(\sprintf('Transaction [%s] was started but not sampled because sample rate (decided by %s) is invalid.', (string) $transaction->getTraceId(), $sampleSource), ['context' => $context]);
-
-                return $transaction;
-            }
-
-            $transaction->getMetadata()->setSamplingRate($sampleRate);
-
-            // Always overwrite the sample_rate in the DSC
-            $dynamicSamplingContext = $context->getMetadata()->getDynamicSamplingContext();
-            if ($dynamicSamplingContext !== null) {
-                $dynamicSamplingContext->set('sample_rate', (string) $sampleRate, true);
-            }
-
-            if ($sampleRate === 0.0) {
-                $transaction->setSampled(false);
-
-                $logger->info(\sprintf('Transaction [%s] was started but not sampled because sample rate (decided by %s) is %s.', (string) $transaction->getTraceId(), $sampleSource, $sampleRate), ['context' => $context]);
-
-                return $transaction;
-            }
-
-            $transaction->setSampled($sampleRand < $sampleRate);
-        }
-
-        if (!$transaction->getSampled()) {
-            $logger->info(\sprintf('Transaction [%s] was started but not sampled, decided by %s.', (string) $transaction->getTraceId(), $sampleSource), ['context' => $context]);
-
-            return $transaction;
-        }
-
-        $logger->info(\sprintf('Transaction [%s] was started and sampled, decided by %s.', (string) $transaction->getTraceId(), $sampleSource), ['context' => $context]);
-
-        $transaction->initSpanRecorder();
-
-        $profilesSampleSource = 'config:profiles_sample_rate';
-        $profilesSampler = $options->getProfilesSampler();
-
-        if ($profilesSampler !== null) {
-            $profilesSampleRate = $profilesSampler($samplingContext);
-            $profilesSampleSource = 'config:profiles_sampler';
-        } else {
-            $profilesSampleRate = $options->getProfilesSampleRate();
-        }
-
-        if ($profilesSampleRate === null) {
-            $logger->info(\sprintf('Transaction [%s] is not profiling because neither `profiles_sample_rate` nor `profiles_sampler` option is set.', (string) $transaction->getTraceId()));
-        } elseif (!$this->isValidSampleRate($profilesSampleRate)) {
-            $logger->warning(\sprintf('Transaction [%s] is not profiling because profile sample rate (decided by %s) is invalid.', (string) $transaction->getTraceId(), $profilesSampleSource));
-        } elseif ($this->sample($profilesSampleRate)) {
-            $logger->info(\sprintf('Transaction [%s] started profiling because it was sampled.', (string) $transaction->getTraceId()));
-
-            $transaction->initProfiler()->start();
-        } else {
-            $logger->info(\sprintf('Transaction [%s] is not profiling because it was not sampled.', (string) $transaction->getTraceId()));
-        }
-
-        return $transaction;
-    }
-
-    /**
-     * {@inheritdoc}
-     */
-    public function getTransaction(): ?Transaction
-    {
-        return $this->getScope()->getTransaction();
-    }
-
-    /**
-     * {@inheritdoc}
-     */
-    public function setSpan(?Span $span): HubInterface
-    {
-        $this->getScope()->setSpan($span);
-
-        return $this;
-    }
-
-    /**
-     * {@inheritdoc}
-     */
-    public function getSpan(): ?Span
-    {
-        return $this->getScope()->getSpan();
-    }
-
-    /**
-     * Gets the scope bound to the top of the stack.
-     */
-    private function getScope(): Scope
-    {
-        return $this->getStackTop()->getScope();
-    }
-
-    /**
-     * Gets the topmost client/layer pair in the stack.
-     */
-    private function getStackTop(): Layer
-    {
-        return $this->stack[\count($this->stack) - 1];
-    }
-
-    private function getSampleRate(?bool $hasParentBeenSampled, float $fallbackSampleRate): float
-    {
-        if ($hasParentBeenSampled === true) {
-            return 1.0;
-        }
-
-        if ($hasParentBeenSampled === false) {
-            return 0.0;
-        }
-
-        return $fallbackSampleRate;
-    }
-
-    /**
-     * @param mixed $sampleRate
-     */
-    private function sample($sampleRate): bool
-    {
-        if ($sampleRate === 0.0 || $sampleRate === null) {
-            return false;
-        }
-
-        if ($sampleRate === 1.0) {
-            return true;
-        }
-
-        return mt_rand(0, mt_getrandmax() - 1) / mt_getrandmax() < $sampleRate;
-    }
-
-    /**
-     * @param mixed $sampleRate
-     */
-    private function isValidSampleRate($sampleRate): bool
-    {
-        if (!\is_float($sampleRate) && !\is_int($sampleRate)) {
-            return false;
-        }
-
-        if ($sampleRate < 0 || $sampleRate > 1) {
-            return false;
-        }
-
-        return true;
-    }
-}
diff --git a/src/State/HubAdapter.php b/src/State/HubAdapter.php
deleted file mode 100644
index 83272be9b6..0000000000
--- a/src/State/HubAdapter.php
+++ /dev/null
@@ -1,230 +0,0 @@
-<?php
-
-declare(strict_types=1);
-
-namespace Sentry\State;
-
-use Sentry\Attachment\Attachment;
-use Sentry\Breadcrumb;
-use Sentry\CheckInStatus;
-use Sentry\ClientInterface;
-use Sentry\Event;
-use Sentry\EventHint;
-use Sentry\EventId;
-use Sentry\Integration\IntegrationInterface;
-use Sentry\MonitorConfig;
-use Sentry\SentrySdk;
-use Sentry\Severity;
-use Sentry\Tracing\Span;
-use Sentry\Tracing\Transaction;
-use Sentry\Tracing\TransactionContext;
-
-/**
- * An implementation of {@see HubInterface} that uses {@see SentrySdk} internally
- * to manage the current hub.
- */
-final class HubAdapter implements HubInterface
-{
-    /**
-     * @var self|null The single instance which forwards all calls to {@see SentrySdk}
-     */
-    private static $instance;
-
-    /**
-     * Constructor.
-     */
-    private function __construct()
-    {
-    }
-
-    /**
-     * Gets the instance of this class. This is a singleton, so once initialized
-     * you will always get the same instance.
-     */
-    public static function getInstance(): self
-    {
-        if (self::$instance === null) {
-            self::$instance = new self();
-        }
-
-        return self::$instance;
-    }
-
-    /**
-     * {@inheritdoc}
-     */
-    public function getClient(): ClientInterface
-    {
-        return SentrySdk::getCurrentHub()->getClient();
-    }
-
-    /**
-     * {@inheritdoc}
-     */
-    public function getLastEventId(): ?EventId
-    {
-        return SentrySdk::getCurrentHub()->getLastEventId();
-    }
-
-    /**
-     * {@inheritdoc}
-     */
-    public function pushScope(): Scope
-    {
-        return SentrySdk::getCurrentHub()->pushScope();
-    }
-
-    /**
-     * {@inheritdoc}
-     */
-    public function popScope(): bool
-    {
-        return SentrySdk::getCurrentHub()->popScope();
-    }
-
-    /**
-     * {@inheritdoc}
-     */
-    public function withScope(callable $callback)
-    {
-        return SentrySdk::getCurrentHub()->withScope($callback);
-    }
-
-    /**
-     * {@inheritdoc}
-     */
-    public function configureScope(callable $callback): void
-    {
-        SentrySdk::getCurrentHub()->configureScope($callback);
-    }
-
-    /**
-     * {@inheritdoc}
-     */
-    public function bindClient(ClientInterface $client): void
-    {
-        SentrySdk::getCurrentHub()->bindClient($client);
-    }
-
-    /**
-     * {@inheritdoc}
-     */
-    public function captureMessage(string $message, ?Severity $level = null, ?EventHint $hint = null): ?EventId
-    {
-        return SentrySdk::getCurrentHub()->captureMessage($message, $level, $hint);
-    }
-
-    /**
-     * {@inheritdoc}
-     */
-    public function captureException(\Throwable $exception, ?EventHint $hint = null): ?EventId
-    {
-        return SentrySdk::getCurrentHub()->captureException($exception, $hint);
-    }
-
-    /**
-     * {@inheritdoc}
-     */
-    public function captureEvent(Event $event, ?EventHint $hint = null): ?EventId
-    {
-        return SentrySdk::getCurrentHub()->captureEvent($event, $hint);
-    }
-
-    /**
-     * {@inheritdoc}
-     */
-    public function captureLastError(?EventHint $hint = null): ?EventId
-    {
-        return SentrySdk::getCurrentHub()->captureLastError($hint);
-    }
-
-    /**
-     * {@inheritdoc}
-     *
-     * @param int|float|null $duration
-     */
-    public function captureCheckIn(string $slug, CheckInStatus $status, $duration = null, ?MonitorConfig $monitorConfig = null, ?string $checkInId = null): ?string
-    {
-        return SentrySdk::getCurrentHub()->captureCheckIn($slug, $status, $duration, $monitorConfig, $checkInId);
-    }
-
-    /**
-     * {@inheritdoc}
-     */
-    public function addBreadcrumb(Breadcrumb $breadcrumb): bool
-    {
-        return SentrySdk::getCurrentHub()->addBreadcrumb($breadcrumb);
-    }
-
-    /**
-     * {@inheritDoc}
-     */
-    public function addAttachment(Attachment $attachment): bool
-    {
-        return SentrySdk::getCurrentHub()->addAttachment($attachment);
-    }
-
-    /**
-     * {@inheritdoc}
-     */
-    public function getIntegration(string $className): ?IntegrationInterface
-    {
-        return SentrySdk::getCurrentHub()->getIntegration($className);
-    }
-
-    /**
-     * {@inheritdoc}
-     */
-    public function startTransaction(TransactionContext $context, array $customSamplingContext = []): Transaction
-    {
-        return SentrySdk::getCurrentHub()->startTransaction($context, $customSamplingContext);
-    }
-
-    /**
-     * {@inheritdoc}
-     */
-    public function getTransaction(): ?Transaction
-    {
-        return SentrySdk::getCurrentHub()->getTransaction();
-    }
-
-    /**
-     * {@inheritdoc}
-     */
-    public function getSpan(): ?Span
-    {
-        return SentrySdk::getCurrentHub()->getSpan();
-    }
-
-    /**
-     * {@inheritdoc}
-     */
-    public function setSpan(?Span $span): HubInterface
-    {
-        return SentrySdk::getCurrentHub()->setSpan($span);
-    }
-
-    /**
-     * @see https://www.php.net/manual/en/language.oop5.cloning.php#object.clone
-     */
-    public function __clone()
-    {
-        throw new \BadMethodCallException('Cloning is forbidden.');
-    }
-
-    /**
-     * @see https://www.php.net/manual/en/language.oop5.magic.php#object.wakeup
-     */
-    public function __wakeup(): void
-    {
-        throw new \BadMethodCallException('Unserializing instances of this class is forbidden.');
-    }
-
-    /**
-     * @see https://www.php.net/manual/en/language.oop5.magic.php#object.sleep
-     */
-    public function __sleep()
-    {
-        throw new \BadMethodCallException('Serializing instances of this class is forbidden.');
-    }
-}
diff --git a/src/State/HubInterface.php b/src/State/HubInterface.php
deleted file mode 100644
index c3c8c67a11..0000000000
--- a/src/State/HubInterface.php
+++ /dev/null
@@ -1,161 +0,0 @@
-<?php
-
-declare(strict_types=1);
-
-namespace Sentry\State;
-
-use Sentry\Attachment\Attachment;
-use Sentry\Breadcrumb;
-use Sentry\CheckInStatus;
-use Sentry\ClientInterface;
-use Sentry\Event;
-use Sentry\EventHint;
-use Sentry\EventId;
-use Sentry\Integration\IntegrationInterface;
-use Sentry\MonitorConfig;
-use Sentry\Severity;
-use Sentry\Tracing\Span;
-use Sentry\Tracing\Transaction;
-use Sentry\Tracing\TransactionContext;
-
-interface HubInterface
-{
-    /**
-     * Gets the client bound to the top of the stack.
-     */
-    public function getClient(): ClientInterface;
-
-    /**
-     * Gets the ID of the last captured event.
-     */
-    public function getLastEventId(): ?EventId;
-
-    /**
-     * Creates a new scope to store context information that will be layered on
-     * top of the current one. It is isolated, i.e. all breadcrumbs and context
-     * information added to this scope will be removed once the scope ends. Be
-     * sure to always remove this scope with {@see Hub::popScope} when the
-     * operation finishes or throws.
-     */
-    public function pushScope(): Scope;
-
-    /**
-     * Removes a previously pushed scope from the stack. This restores the state
-     * before the scope was pushed. All breadcrumbs and context information added
-     * since the last call to {@see Hub::pushScope} are discarded.
-     */
-    public function popScope(): bool;
-
-    /**
-     * Creates a new scope with and executes the given operation within. The scope
-     * is automatically removed once the operation finishes or throws.
-     *
-     * @param callable $callback The callback to be executed
-     *
-     * @phpstan-template T
-     *
-     * @phpstan-param callable(Scope): T $callback
-     *
-     * @return mixed|void The callback's return value, upon successful execution
-     *
-     * @phpstan-return T
-     */
-    public function withScope(callable $callback);
-
-    /**
-     * Calls the given callback passing to it the current scope so that any
-     * operation can be run within its context.
-     */
-    public function configureScope(callable $callback): void;
-
-    /**
-     * Binds the given client to the current scope.
-     */
-    public function bindClient(ClientInterface $client): void;
-
-    /**
-     * Captures a message event and sends it to Sentry.
-     */
-    public function captureMessage(string $message, ?Severity $level = null, ?EventHint $hint = null): ?EventId;
-
-    /**
-     * Captures an exception event and sends it to Sentry.
-     */
-    public function captureException(\Throwable $exception, ?EventHint $hint = null): ?EventId;
-
-    /**
-     * Captures a new event using the provided data.
-     */
-    public function captureEvent(Event $event, ?EventHint $hint = null): ?EventId;
-
-    /**
-     * Captures an event that logs the last occurred error.
-     */
-    public function captureLastError(?EventHint $hint = null): ?EventId;
-
-    /**
-     * Records a new breadcrumb which will be attached to future events. They
-     * will be added to subsequent events to provide more context on user's
-     * actions prior to an error or crash.
-     */
-    public function addBreadcrumb(Breadcrumb $breadcrumb): bool;
-
-    /**
-     * Captures a check-in.
-     *
-     * @param int|float|null $duration
-     */
-    public function captureCheckIn(string $slug, CheckInStatus $status, $duration = null, ?MonitorConfig $monitorConfig = null, ?string $checkInId = null): ?string;
-
-    /**
-     * Gets the integration whose FQCN matches the given one if it's available on the current client.
-     *
-     * @param string $className The FQCN of the integration
-     *
-     * @phpstan-template T of IntegrationInterface
-     *
-     * @phpstan-param class-string<T> $className
-     *
-     * @phpstan-return T|null
-     */
-    public function getIntegration(string $className): ?IntegrationInterface;
-
-    /**
-     * Starts a new `Transaction` and returns it. This is the entry point to manual
-     * tracing instrumentation.
-     *
-     * A tree structure can be built by adding child spans to the transaction, and
-     * child spans to other spans. To start a new child span within the transaction
-     * or any span, call the respective `startChild()` method.
-     *
-     * Every child span must be finished before the transaction is finished,
-     * otherwise the unfinished spans are discarded.
-     *
-     * The transaction must be finished with a call to its `finish()` method, at
-     * which point the transaction with all its finished child spans will be sent to
-     * Sentry.
-     *
-     * @param array<string, mixed> $customSamplingContext Additional context that will be passed to the {@see SamplingContext}
-     */
-    public function startTransaction(TransactionContext $context, array $customSamplingContext = []): Transaction;
-
-    /**
-     * Returns the transaction that is on the Hub.
-     */
-    public function getTransaction(): ?Transaction;
-
-    /**
-     * Returns the span that is on the Hub.
-     */
-    public function getSpan(): ?Span;
-
-    /**
-     * Sets the span on the Hub.
-     */
-    public function setSpan(?Span $span): HubInterface;
-
-    /**
-     * Records a new attachment that will be attached to error and transaction events.
-     */
-    public function addAttachment(Attachment $attachment): bool;
-}
diff --git a/src/State/IsolationScope.php b/src/State/IsolationScope.php
new file mode 100644
index 0000000000..c9b66d8e2d
--- /dev/null
+++ b/src/State/IsolationScope.php
@@ -0,0 +1,126 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Sentry\State;
+
+use Sentry\Tracing\PropagationContext;
+use Sentry\Tracing\Span;
+use Sentry\Tracing\Transaction;
+
+/**
+ * The scope holds data that should implicitly be sent with Sentry events. It
+ * can hold context data, extra parameters, level overrides, fingerprints etc.
+ */
+class IsolationScope extends MutableScope
+{
+    /**
+     * @var Span|null Set a Span on the Scope
+     */
+    private $span;
+
+    public function __construct(?PropagationContext $propagationContext = null)
+    {
+        parent::__construct();
+        $this->scopeData->setPropagationContext($propagationContext ?? PropagationContext::fromDefaults());
+    }
+
+    /**
+     * Adds a feature flag to the scope.
+     *
+     * @return $this
+     */
+    public function addFeatureFlag(string $key, bool $result): self
+    {
+        $this->scopeData->addFeatureFlag($key, $result);
+
+        if ($this->span !== null) {
+            $this->span->setFlag($key, $result);
+        }
+
+        return $this;
+    }
+
+    /**
+     * Clears event payload data from the scope. The client binding and last
+     * event ID are preserved.
+     */
+    public function clear(): void
+    {
+        parent::clear();
+        $this->span = null;
+    }
+
+    /**
+     * Returns the span that is on the scope.
+     */
+    public function getSpan(): ?Span
+    {
+        return $this->span;
+    }
+
+    /**
+     * Sets the span on the scope.
+     *
+     * @param Span|null $span The span
+     *
+     * @return $this
+     */
+    public function setSpan(?Span $span): self
+    {
+        $this->span = $span;
+
+        return $this;
+    }
+
+    /**
+     * Returns the transaction attached to the scope (if there is one).
+     */
+    public function getTransaction(): ?Transaction
+    {
+        if ($this->span !== null) {
+            return $this->span->getTransaction();
+        }
+
+        return null;
+    }
+
+    public function hasExternalPropagationContext(): bool
+    {
+        return $this->span === null && self::getExternalPropagationContext() !== null;
+    }
+
+    public function getPropagationContext(): PropagationContext
+    {
+        return $this->scopeData->getPropagationContext();
+    }
+
+    public function setPropagationContext(PropagationContext $propagationContext): self
+    {
+        $this->scopeData->setPropagationContext($propagationContext);
+
+        return $this;
+    }
+
+    /**
+     * @return array{
+     *     trace_id: string,
+     *     span_id: string,
+     *     parent_span_id?: string,
+     *     data?: array<string, mixed>,
+     *     description?: string,
+     *     op?: string,
+     *     status?: string,
+     *     tags?: array<string, string>,
+     *     origin?: string
+     * }
+     */
+    public function getTraceContext(): array
+    {
+        if ($this->span !== null) {
+            return $this->span->getTraceContext();
+        }
+
+        return self::getExternalPropagationContext() ?? $this->scopeData->getPropagationContext()->getTraceContext();
+    }
+}
diff --git a/src/State/Layer.php b/src/State/Layer.php
deleted file mode 100644
index 3befbd80a8..0000000000
--- a/src/State/Layer.php
+++ /dev/null
@@ -1,82 +0,0 @@
-<?php
-
-declare(strict_types=1);
-
-namespace Sentry\State;
-
-use Sentry\ClientInterface;
-
-/**
- * This class holds a pair of client and scope instances for each element in the
- * stack of a {@see Hub}.
- *
- * @internal
- */
-final class Layer
-{
-    /**
-     * @var ClientInterface The client held by this layer
-     */
-    private $client;
-
-    /**
-     * @var Scope The scope held by this layer
-     */
-    private $scope;
-
-    /**
-     * Constructor.
-     *
-     * @param ClientInterface $client The client held by this layer
-     * @param Scope           $scope  The scope held by this layer
-     */
-    public function __construct(ClientInterface $client, Scope $scope)
-    {
-        $this->client = $client;
-        $this->scope = $scope;
-    }
-
-    /**
-     * Gets the client held by this layer.
-     */
-    public function getClient(): ClientInterface
-    {
-        return $this->client;
-    }
-
-    /**
-     * Sets the client held by this layer.
-     *
-     * @param ClientInterface $client The client instance
-     *
-     * @return $this
-     */
-    public function setClient(ClientInterface $client): self
-    {
-        $this->client = $client;
-
-        return $this;
-    }
-
-    /**
-     * Gets the scope held by this layer.
-     */
-    public function getScope(): Scope
-    {
-        return $this->scope;
-    }
-
-    /**
-     * Sets the scope held by this layer.
-     *
-     * @param Scope $scope The scope instance
-     *
-     * @return $this
-     */
-    public function setScope(Scope $scope): self
-    {
-        $this->scope = $scope;
-
-        return $this;
-    }
-}
diff --git a/src/State/MergedScope.php b/src/State/MergedScope.php
new file mode 100644
index 0000000000..0245e22175
--- /dev/null
+++ b/src/State/MergedScope.php
@@ -0,0 +1,153 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Sentry\State;
+
+use Sentry\Event;
+use Sentry\EventHint;
+use Sentry\EventType;
+use Sentry\Options;
+use Sentry\Tracing\DynamicSamplingContext;
+use Sentry\Tracing\Span;
+
+/**
+ * The scope holds data that should implicitly be sent with Sentry events. It
+ * can hold context data, extra parameters, level overrides, fingerprints etc.
+ *
+ * @internal
+ */
+final class MergedScope extends Scope
+{
+    /**
+     * @var Span|null
+     */
+    private $span;
+
+    public function __construct(ScopeData $scopeData, ?Span $span)
+    {
+        $this->scopeData = $scopeData;
+        $this->span = $span;
+    }
+
+    /**
+     * Applies the current context and fingerprint to the event. If the event has
+     * already some breadcrumbs on it, the ones from this scope won't get merged.
+     *
+     * @param Event $event The event object that will be enriched with scope data
+     */
+    public function applyToEvent(Event $event, ?EventHint $hint = null, ?Options $options = null): ?Event
+    {
+        $event->setFingerprint(array_merge($event->getFingerprint(), $this->scopeData->getFingerprint()));
+
+        if (empty($event->getBreadcrumbs())) {
+            $breadcrumbs = $this->scopeData->getBreadcrumbs();
+            $maxBreadcrumbs = $options !== null ? $options->getMaxBreadcrumbs() : Options::DEFAULT_MAX_BREADCRUMBS;
+
+            if (\count($breadcrumbs) > $maxBreadcrumbs) {
+                $breadcrumbs = $maxBreadcrumbs > 0 ? \array_slice($breadcrumbs, -$maxBreadcrumbs) : [];
+            }
+
+            $event->setBreadcrumb($breadcrumbs);
+        }
+
+        if ($this->scopeData->getLevel() !== null) {
+            $event->setLevel($this->scopeData->getLevel());
+        }
+
+        if (!empty($this->scopeData->getTags())) {
+            $event->setTags(array_merge($this->scopeData->getTags(), $event->getTags()));
+        }
+
+        if (!empty($this->scopeData->getFlags())) {
+            $event->setContext('flags', [
+                'values' => array_map(static function (array $flag) {
+                    return [
+                        'flag' => key($flag),
+                        'result' => current($flag),
+                    ];
+                }, array_values($this->scopeData->getFlags())),
+            ]);
+        }
+
+        if (!empty($this->scopeData->getExtra())) {
+            $event->setExtra(array_merge($this->scopeData->getExtra(), $event->getExtra()));
+        }
+
+        $scopeUser = $this->scopeData->getUser();
+        if ($scopeUser !== null) {
+            $user = $event->getUser();
+
+            if ($user === null) {
+                $user = $scopeUser;
+            } else {
+                $user = (clone $scopeUser)->merge($user);
+            }
+
+            $event->setUser($user);
+        }
+
+        /**
+         * Apply the trace context to errors if there is a Span on the Scope.
+         * Else fallback to the external propagation context or to the
+         * propagation context.
+         * But do not override a trace context already present.
+         */
+        $externalPropagationContext = null;
+        if ($this->span === null) {
+            $externalPropagationContext = self::getExternalPropagationContext();
+        }
+
+        $traceContext = $this->span !== null
+            ? $this->span->getTraceContext()
+            : ($externalPropagationContext ?? $this->scopeData->getPropagationContext()->getTraceContext());
+
+        if (!\array_key_exists('trace', $event->getContexts())) {
+            $event->setContext('trace', $traceContext);
+        }
+
+        if ($this->span !== null) {
+            // Apply the dynamic sampling context to errors if there is a Transaction on the Scope
+            $transaction = $this->span->getTransaction();
+            if ($transaction !== null) {
+                $event->setSdkMetadata('dynamic_sampling_context', $transaction->getDynamicSamplingContext());
+            }
+        } elseif ($externalPropagationContext === null) {
+            $propagationContext = $this->scopeData->getPropagationContext();
+            $dynamicSamplingContext = $propagationContext->getDynamicSamplingContext();
+            if ($dynamicSamplingContext === null && $options !== null) {
+                $dynamicSamplingContext = DynamicSamplingContext::fromOptionsAndPropagationContext($options, $propagationContext);
+            }
+            $event->setSdkMetadata('dynamic_sampling_context', $dynamicSamplingContext);
+        }
+
+        foreach (array_merge($this->scopeData->getContexts(), $event->getContexts()) as $name => $data) {
+            $event->setContext($name, $data);
+        }
+
+        // We create a empty `EventHint` instance to allow processors to always receive a `EventHint` instance even if there wasn't one
+        if ($hint === null) {
+            $hint = new EventHint();
+        }
+
+        if ($event->getType() === EventType::event() || $event->getType() === EventType::transaction()) {
+            if (empty($event->getAttachments())) {
+                $event->setAttachments($this->scopeData->getAttachments());
+            }
+        }
+
+        foreach (array_merge(parent::$globalEventProcessors, $this->scopeData->getEventProcessors()) as $processor) {
+            $event = $processor($event, $hint);
+
+            if ($event === null) {
+                return null;
+            }
+
+            if (!$event instanceof Event) {
+                throw new \InvalidArgumentException(\sprintf('The event processor must return null or an instance of the %s class', Event::class));
+            }
+        }
+
+        return $event;
+    }
+}
diff --git a/src/State/MutableScope.php b/src/State/MutableScope.php
new file mode 100644
index 0000000000..36c2957338
--- /dev/null
+++ b/src/State/MutableScope.php
@@ -0,0 +1,267 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Sentry\State;
+
+use Sentry\Attachment\Attachment;
+use Sentry\Breadcrumb;
+use Sentry\ClientInterface;
+use Sentry\Event;
+use Sentry\EventHint;
+use Sentry\Severity;
+use Sentry\UserDataBag;
+
+/**
+ * The scope holds data that should implicitly be sent with Sentry events. It
+ * can hold context data, extra parameters, level overrides, fingerprints etc.
+ */
+abstract class MutableScope extends Scope
+{
+    /**
+     * Returns the client bound to this scope.
+     */
+    public function getClient(): ClientInterface
+    {
+        return $this->scopeData->getClient();
+    }
+
+    /**
+     * Sets the client bound to this scope.
+     *
+     * @return $this
+     */
+    public function setClient(ClientInterface $client): self
+    {
+        $this->scopeData->setClient($client);
+
+        return $this;
+    }
+
+    /**
+     * Sets a new tag in the tags context.
+     *
+     * @param string $key   The key that uniquely identifies the tag
+     * @param string $value The value
+     *
+     * @return $this
+     */
+    public function setTag(string $key, string $value): self
+    {
+        $this->scopeData->setTag($key, $value);
+
+        return $this;
+    }
+
+    /**
+     * Merges the given tags into the current tags context.
+     *
+     * @param array<string, string> $tags The tags to merge into the current context
+     *
+     * @return $this
+     */
+    public function setTags(array $tags): self
+    {
+        $this->scopeData->setTags(array_merge($this->scopeData->getTags(), $tags));
+
+        return $this;
+    }
+
+    /**
+     * Removes a given tag from the tags context.
+     *
+     * @param string $key The key that uniquely identifies the tag
+     *
+     * @return $this
+     */
+    public function removeTag(string $key): self
+    {
+        $this->scopeData->removeTag($key);
+
+        return $this;
+    }
+
+    /**
+     * Sets data to the context by a given name.
+     *
+     * @param string               $name  The name that uniquely identifies the context
+     * @param array<string, mixed> $value The value
+     *
+     * @return $this
+     */
+    public function setContext(string $name, array $value): self
+    {
+        if (!empty($value)) {
+            $this->scopeData->setContext($name, $value);
+        }
+
+        return $this;
+    }
+
+    /**
+     * Removes the context from the scope.
+     *
+     * @param string $name The name that uniquely identifies the context
+     *
+     * @return $this
+     */
+    public function removeContext(string $name): self
+    {
+        $this->scopeData->removeContext($name);
+
+        return $this;
+    }
+
+    /**
+     * Sets a new information in the extra context.
+     *
+     * @param string $key   The key that uniquely identifies the information
+     * @param mixed  $value The value
+     *
+     * @return $this
+     */
+    public function setExtra(string $key, $value): self
+    {
+        $this->scopeData->setExtra($key, $value);
+
+        return $this;
+    }
+
+    /**
+     * Merges the given data into the current extras context.
+     *
+     * @param array<string, mixed> $extras Data to merge into the current context
+     *
+     * @return $this
+     */
+    public function setExtras(array $extras): self
+    {
+        $this->scopeData->setExtras(array_merge($this->scopeData->getExtra(), $extras));
+
+        return $this;
+    }
+
+    /**
+     * Merges the given data in the user context.
+     *
+     * @param array<string, mixed>|UserDataBag $user The user data
+     *
+     * @return $this
+     */
+    public function setUser($user): self
+    {
+        $this->scopeData->setUser($user);
+
+        return $this;
+    }
+
+    /**
+     * Removes all data of the user context.
+     *
+     * @return $this
+     */
+    public function removeUser(): self
+    {
+        $this->scopeData->removeUser();
+
+        return $this;
+    }
+
+    /**
+     * Sets the list of strings used to dictate the deduplication of this event.
+     *
+     * @param string[] $fingerprint The fingerprint values
+     *
+     * @return $this
+     */
+    public function setFingerprint(array $fingerprint): self
+    {
+        $this->scopeData->setFingerprint($fingerprint);
+
+        return $this;
+    }
+
+    /**
+     * Sets the severity to apply to all events captured in this scope.
+     *
+     * @param Severity|null $level The severity
+     *
+     * @return $this
+     */
+    public function setLevel(?Severity $level): self
+    {
+        $this->scopeData->setLevel($level);
+
+        return $this;
+    }
+
+    /**
+     * Add the given breadcrumb to the scope.
+     *
+     * @param Breadcrumb $breadcrumb     The breadcrumb to add
+     * @param int        $maxBreadcrumbs The maximum number of breadcrumbs to record
+     *
+     * @return $this
+     */
+    public function addBreadcrumb(Breadcrumb $breadcrumb, int $maxBreadcrumbs = 100): self
+    {
+        $this->scopeData->addBreadcrumb($breadcrumb, $maxBreadcrumbs);
+
+        return $this;
+    }
+
+    /**
+     * Clears all the breadcrumbs.
+     *
+     * @return $this
+     */
+    public function clearBreadcrumbs(): self
+    {
+        $this->scopeData->clearBreadcrumbs();
+
+        return $this;
+    }
+
+    /**
+     * Adds a new event processor that will be called after {@see MergedScope::applyToEvent}
+     * finished its work.
+     *
+     * @param callable(Event, EventHint): ?Event $eventProcessor The event processor
+     *
+     * @return $this
+     */
+    public function addEventProcessor(callable $eventProcessor): self
+    {
+        $this->scopeData->addEventProcessor($eventProcessor);
+
+        return $this;
+    }
+
+    /**
+     * Clears event payload data from the scope. The client binding and last
+     * event ID are preserved.
+     */
+    public function clear(): void
+    {
+        $this->scopeData->clear();
+    }
+
+    public function __clone()
+    {
+        $this->scopeData = clone $this->scopeData;
+    }
+
+    public function addAttachment(Attachment $attachment): self
+    {
+        $this->scopeData->addAttachment($attachment);
+
+        return $this;
+    }
+
+    public function clearAttachments(): self
+    {
+        $this->scopeData->setAttachments([]);
+
+        return $this;
+    }
+}
diff --git a/src/State/RuntimeContext.php b/src/State/RuntimeContext.php
index 6910cae608..a2b3a45d61 100644
--- a/src/State/RuntimeContext.php
+++ b/src/State/RuntimeContext.php
@@ -4,6 +4,7 @@
 
 namespace Sentry\State;
 
+use Sentry\EventId;
 use Sentry\Logs\LogsAggregator;
 use Sentry\Metrics\MetricsAggregator;
 
@@ -23,9 +24,9 @@ final class RuntimeContext
     private $id;
 
     /**
-     * @var HubInterface
+     * @var IsolationScope
      */
-    private $hub;
+    private $isolationScope;
 
     /**
      * @var LogsAggregator
@@ -37,10 +38,15 @@ final class RuntimeContext
      */
     private $metricsAggregator;
 
-    public function __construct(string $id, HubInterface $hub)
+    /**
+     * @var EventId|null The ID of the last event captured within this context
+     */
+    private $lastEventId;
+
+    public function __construct(string $id, ?IsolationScope $isolationScope = null)
     {
         $this->id = $id;
-        $this->hub = $hub;
+        $this->isolationScope = $isolationScope ?? new IsolationScope();
         $this->logsAggregator = new LogsAggregator();
         $this->metricsAggregator = new MetricsAggregator();
     }
@@ -50,14 +56,14 @@ public function getId(): string
         return $this->id;
     }
 
-    public function getHub(): HubInterface
+    public function getIsolationScope(): IsolationScope
     {
-        return $this->hub;
+        return $this->isolationScope;
     }
 
-    public function setHub(HubInterface $hub): void
+    public function setIsolationScope(IsolationScope $isolationScope): void
     {
-        $this->hub = $hub;
+        $this->isolationScope = $isolationScope;
     }
 
     public function getLogsAggregator(): LogsAggregator
@@ -69,4 +75,14 @@ public function getMetricsAggregator(): MetricsAggregator
     {
         return $this->metricsAggregator;
     }
+
+    public function getLastEventId(): ?EventId
+    {
+        return $this->lastEventId;
+    }
+
+    public function setLastEventId(?EventId $lastEventId): void
+    {
+        $this->lastEventId = $lastEventId;
+    }
 }
diff --git a/src/State/RuntimeContextManager.php b/src/State/RuntimeContextManager.php
index cec72ee48e..4fd2c7e1a5 100644
--- a/src/State/RuntimeContextManager.php
+++ b/src/State/RuntimeContextManager.php
@@ -5,7 +5,8 @@
 namespace Sentry\State;
 
 use Psr\Log\LoggerInterface;
-use Sentry\Tracing\PropagationContext;
+use Sentry\ClientInterface;
+use Sentry\SentrySdk;
 
 /**
  * Manages runtime-local SDK state across different execution models.
@@ -22,11 +23,6 @@ final class RuntimeContextManager
 {
     private const PROCESS_EXECUTION_CONTEXT_KEY = 'process';
 
-    /**
-     * @var HubInterface
-     */
-    private $baseHub;
-
     /**
      * @var RuntimeContext|null
      */
@@ -42,46 +38,6 @@ final class RuntimeContextManager
      */
     private $executionContextToRuntimeContext = [];
 
-    public function __construct(HubInterface $baseHub)
-    {
-        $this->baseHub = $baseHub;
-        $this->globalContext = null;
-    }
-
-    /**
-     * Sets the current hub with context-aware behavior.
-     *
-     * If a runtime context is active for the current execution key, the hub is
-     * updated only for that active context. Otherwise, the baseline/global hub
-     * template is updated.
-     *
-     * @return bool Whether the hub was set on an active runtime context
-     */
-    public function setCurrentHub(HubInterface $hub): bool
-    {
-        $executionContextKey = $this->getExecutionContextKey();
-
-        if ($this->hasActiveContextForExecutionContextKey($executionContextKey)) {
-            $runtimeContextId = $this->executionContextToRuntimeContext[$executionContextKey];
-            $this->activeContexts[$runtimeContextId]->setHub($hub);
-
-            return true;
-        }
-
-        $this->baseHub = $hub;
-
-        if ($this->globalContext !== null) {
-            $this->globalContext->setHub($hub);
-        }
-
-        return false;
-    }
-
-    public function getCurrentHub(): HubInterface
-    {
-        return $this->getCurrentContext()->getHub();
-    }
-
     public function getCurrentContext(): RuntimeContext
     {
         $executionContextKey = $this->getExecutionContextKey();
@@ -137,7 +93,7 @@ public function endContext(?int $timeout = null): void
     private function createContextForExecutionContextKey(string $executionContextKey): void
     {
         $runtimeContextId = $this->generateRuntimeContextId();
-        $runtimeContext = new RuntimeContext($runtimeContextId, $this->createHubFromBaseHub());
+        $runtimeContext = new RuntimeContext($runtimeContextId);
 
         $this->activeContexts[$runtimeContextId] = $runtimeContext;
         $this->executionContextToRuntimeContext[$executionContextKey] = $runtimeContextId;
@@ -154,19 +110,18 @@ private function removeContextById(string $runtimeContextId, ?int $timeout = nul
         // Remove any key mappings that may still reference this context.
         $this->removeExecutionContextMappingsForRuntimeContext($runtimeContextId);
 
-        $logger = $this->getLoggerFromHub($runtimeContext->getHub());
+        $client = SentrySdk::getClient($runtimeContext->getIsolationScope());
+        $logger = $client->getOptions()->getLoggerOrNullLogger();
 
-        $this->flushRuntimeContextResources($runtimeContext, $timeout, $logger);
+        $this->flushRuntimeContextResources($runtimeContext, $client, $timeout, $logger);
     }
 
-    private function flushRuntimeContextResources(RuntimeContext $runtimeContext, ?int $timeout, LoggerInterface $logger): void
+    private function flushRuntimeContextResources(RuntimeContext $runtimeContext, ClientInterface $client, ?int $timeout, LoggerInterface $logger): void
     {
-        $hub = $runtimeContext->getHub();
-
         // captureEvent can throw before transport send (for example from scope event processors
         // or before_send callbacks), so we isolate failures and continue flushing other resources.
         try {
-            $runtimeContext->getLogsAggregator()->flush($hub);
+            $runtimeContext->getLogsAggregator()->flush($client, $runtimeContext->getIsolationScope());
         } catch (\Throwable $exception) {
             $logger->error('Failed to flush logs while ending a runtime context.', [
                 'exception' => $exception,
@@ -176,7 +131,7 @@ private function flushRuntimeContextResources(RuntimeContext $runtimeContext, ?i
 
         // Keep metrics flush independent from logs flush so one bad callback does not block the rest.
         try {
-            $runtimeContext->getMetricsAggregator()->flush($hub);
+            $runtimeContext->getMetricsAggregator()->flush($client, $runtimeContext->getIsolationScope());
         } catch (\Throwable $exception) {
             $logger->error('Failed to flush trace metrics while ending a runtime context.', [
                 'exception' => $exception,
@@ -184,8 +139,6 @@ private function flushRuntimeContextResources(RuntimeContext $runtimeContext, ?i
             ]);
         }
 
-        $client = $hub->getClient();
-
         // Custom transports may throw from close(); endContext must stay best-effort and non-fatal.
         try {
             $client->flush($timeout);
@@ -224,31 +177,6 @@ private function hasActiveContextForExecutionContextKey(string $executionContext
         return true;
     }
 
-    private function createHubFromBaseHub(): HubInterface
-    {
-        if (!$this->baseHub instanceof Hub) {
-            return new Hub($this->baseHub->getClient());
-        }
-
-        $clonedScope = null;
-
-        $this->baseHub->configureScope(static function (Scope $scope) use (&$clonedScope): void {
-            $clonedScope = clone $scope;
-            // Do not inherit active traces into a new runtime context.
-            $clonedScope->setSpan(null);
-            $clonedScope->setPropagationContext(PropagationContext::fromDefaults());
-        });
-
-        return new Hub($this->baseHub->getClient(), $clonedScope ?? new Scope());
-    }
-
-    private function getLoggerFromHub(HubInterface $hub): LoggerInterface
-    {
-        $client = $hub->getClient();
-
-        return $client->getOptions()->getLoggerOrNullLogger();
-    }
-
     private function generateRuntimeContextId(): string
     {
         return \sprintf('%s-%d', str_replace('.', '', uniqid('', true)), mt_rand());
@@ -264,7 +192,7 @@ private function getGlobalContext(): RuntimeContext
     {
         if ($this->globalContext === null) {
             // Lazy fallback keeps baseline behavior when users do not opt into explicit context lifecycle.
-            $this->globalContext = new RuntimeContext('global', $this->baseHub);
+            $this->globalContext = new RuntimeContext('global');
         }
 
         return $this->globalContext;
diff --git a/src/State/Scope.php b/src/State/Scope.php
index 58d95f00ff..90ce93938f 100644
--- a/src/State/Scope.php
+++ b/src/State/Scope.php
@@ -4,25 +4,17 @@
 
 namespace Sentry\State;
 
-use Sentry\Attachment\Attachment;
-use Sentry\Breadcrumb;
+use Sentry\ClientInterface;
 use Sentry\Event;
 use Sentry\EventHint;
-use Sentry\EventType;
-use Sentry\Options;
-use Sentry\Severity;
-use Sentry\Tracing\DynamicSamplingContext;
-use Sentry\Tracing\PropagationContext;
-use Sentry\Tracing\Span;
-use Sentry\Tracing\Transaction;
+use Sentry\NoOpClient;
 use Sentry\UserDataBag;
-use Sentry\Util\DebugType;
 
 /**
  * The scope holds data that should implicitly be sent with Sentry events. It
  * can hold context data, extra parameters, level overrides, fingerprints etc.
  */
-class Scope
+abstract class Scope
 {
     /**
      * Maximum number of flags allowed. We only track the first flags set.
@@ -32,216 +24,36 @@ class Scope
     public const MAX_FLAGS = 100;
 
     /**
-     * @var PropagationContext
-     */
-    private $propagationContext;
-
-    /**
-     * @var Breadcrumb[] The list of breadcrumbs recorded in this scope
-     */
-    private $breadcrumbs = [];
-
-    /**
-     * @var UserDataBag|null The user data associated to this scope
-     */
-    private $user;
-
-    /**
-     * @var array<string, array<string, mixed>> The list of contexts associated to this scope
-     */
-    private $contexts = [];
-
-    /**
-     * @var array<string, string> The list of tags associated to this scope
-     */
-    private $tags = [];
-
-    /**
-     * @var array<int, array<string, bool>> The list of flags associated to this scope
-     */
-    private $flags = [];
-
-    /**
-     * @var array<string, mixed> A set of extra data associated to this scope
-     */
-    private $extra = [];
-
-    /**
-     * @var string[] List of fingerprints used to group events together in
-     *               Sentry
-     */
-    private $fingerprint = [];
-
-    /**
-     * @var Severity|null The severity to associate to the events captured in
-     *                    this scope
-     */
-    private $level;
-
-    /**
-     * @var callable[] List of event processors
+     * @internal
      *
-     * @phpstan-var array<callable(Event, EventHint): ?Event>
-     */
-    private $eventProcessors = [];
-
-    /**
-     * @var Span|null Set a Span on the Scope
+     * @var ScopeData
      */
-    private $span;
-
-    /**
-     * @var Attachment[]
-     */
-    private $attachments = [];
+    protected $scopeData;
 
     /**
      * @var callable[] List of event processors
      *
      * @phpstan-var array<callable(Event, EventHint): ?Event>
      */
-    private static $globalEventProcessors = [];
+    protected static $globalEventProcessors = [];
 
     /**
      * @var callable|null
      */
-    private static $externalPropagationContextCallback;
-
-    public function __construct(?PropagationContext $propagationContext = null)
-    {
-        $this->propagationContext = $propagationContext ?? PropagationContext::fromDefaults();
-    }
-
-    /**
-     * Sets a new tag in the tags context.
-     *
-     * @param string $key   The key that uniquely identifies the tag
-     * @param string $value The value
-     *
-     * @return $this
-     */
-    public function setTag(string $key, string $value): self
-    {
-        $this->tags[$key] = $value;
+    protected static $externalPropagationContextCallback;
 
-        return $this;
-    }
-
-    /**
-     * Merges the given tags into the current tags context.
-     *
-     * @param array<string, string> $tags The tags to merge into the current context
-     *
-     * @return $this
-     */
-    public function setTags(array $tags): self
+    public function __construct()
     {
-        $this->tags = array_merge($this->tags, $tags);
-
-        return $this;
+        $this->scopeData = new ScopeData();
+        $this->scopeData->setClient(new NoOpClient());
     }
 
     /**
-     * Removes a given tag from the tags context.
-     *
-     * @param string $key The key that uniquely identifies the tag
-     *
-     * @return $this
+     * Returns the client bound to this scope.
      */
-    public function removeTag(string $key): self
+    public function getClient(): ClientInterface
     {
-        unset($this->tags[$key]);
-
-        return $this;
-    }
-
-    /**
-     * Adds a feature flag to the scope.
-     *
-     * @return $this
-     */
-    public function addFeatureFlag(string $key, bool $result): self
-    {
-        // If the flag was already set, remove it first
-        // This basically mimics an LRU cache so that the most recently added flags are kept
-        foreach ($this->flags as $flagIndex => $flag) {
-            if (isset($flag[$key])) {
-                unset($this->flags[$flagIndex]);
-            }
-        }
-
-        // Keep only the most recent MAX_FLAGS flags
-        if (\count($this->flags) >= self::MAX_FLAGS) {
-            array_shift($this->flags);
-        }
-
-        $this->flags[] = [$key => $result];
-
-        if ($this->span !== null) {
-            $this->span->setFlag($key, $result);
-        }
-
-        return $this;
-    }
-
-    /**
-     * Sets data to the context by a given name.
-     *
-     * @param string               $name  The name that uniquely identifies the context
-     * @param array<string, mixed> $value The value
-     *
-     * @return $this
-     */
-    public function setContext(string $name, array $value): self
-    {
-        if (!empty($value)) {
-            $this->contexts[$name] = $value;
-        }
-
-        return $this;
-    }
-
-    /**
-     * Removes the context from the scope.
-     *
-     * @param string $name The name that uniquely identifies the context
-     *
-     * @return $this
-     */
-    public function removeContext(string $name): self
-    {
-        unset($this->contexts[$name]);
-
-        return $this;
-    }
-
-    /**
-     * Sets a new information in the extra context.
-     *
-     * @param string $key   The key that uniquely identifies the information
-     * @param mixed  $value The value
-     *
-     * @return $this
-     */
-    public function setExtra(string $key, $value): self
-    {
-        $this->extra[$key] = $value;
-
-        return $this;
-    }
-
-    /**
-     * Merges the given data into the current extras context.
-     *
-     * @param array<string, mixed> $extras Data to merge into the current context
-     *
-     * @return $this
-     */
-    public function setExtras(array $extras): self
-    {
-        $this->extra = array_merge($this->extra, $extras);
-
-        return $this;
+        return $this->scopeData->getClient();
     }
 
     /**
@@ -249,120 +61,11 @@ public function setExtras(array $extras): self
      */
     public function getUser(): ?UserDataBag
     {
-        return $this->user;
-    }
-
-    /**
-     * Merges the given data in the user context.
-     *
-     * @param array<string, mixed>|UserDataBag $user The user data
-     *
-     * @return $this
-     */
-    public function setUser($user): self
-    {
-        if (!\is_array($user) && !$user instanceof UserDataBag) {
-            throw new \TypeError(\sprintf('The $user argument must be either an array or an instance of the "%s" class. Got: "%s".', UserDataBag::class, DebugType::getDebugType($user)));
-        }
-
-        if (\is_array($user)) {
-            $user = UserDataBag::createFromArray($user);
-        }
-
-        if ($this->user === null) {
-            $this->user = $user;
-        } else {
-            $this->user = $this->user->merge($user);
-        }
-
-        return $this;
-    }
-
-    /**
-     * Removes all data of the user context.
-     *
-     * @return $this
-     */
-    public function removeUser(): self
-    {
-        $this->user = null;
-
-        return $this;
-    }
-
-    /**
-     * Sets the list of strings used to dictate the deduplication of this event.
-     *
-     * @param string[] $fingerprint The fingerprint values
-     *
-     * @return $this
-     */
-    public function setFingerprint(array $fingerprint): self
-    {
-        $this->fingerprint = $fingerprint;
-
-        return $this;
+        return $this->scopeData->getUser();
     }
 
     /**
-     * Sets the severity to apply to all events captured in this scope.
-     *
-     * @param Severity|null $level The severity
-     *
-     * @return $this
-     */
-    public function setLevel(?Severity $level): self
-    {
-        $this->level = $level;
-
-        return $this;
-    }
-
-    /**
-     * Add the given breadcrumb to the scope.
-     *
-     * @param Breadcrumb $breadcrumb     The breadcrumb to add
-     * @param int        $maxBreadcrumbs The maximum number of breadcrumbs to record
-     *
-     * @return $this
-     */
-    public function addBreadcrumb(Breadcrumb $breadcrumb, int $maxBreadcrumbs = 100): self
-    {
-        $this->breadcrumbs[] = $breadcrumb;
-        $this->breadcrumbs = \array_slice($this->breadcrumbs, -$maxBreadcrumbs);
-
-        return $this;
-    }
-
-    /**
-     * Clears all the breadcrumbs.
-     *
-     * @return $this
-     */
-    public function clearBreadcrumbs(): self
-    {
-        $this->breadcrumbs = [];
-
-        return $this;
-    }
-
-    /**
-     * Adds a new event processor that will be called after {@see Scope::applyToEvent}
-     * finished its work.
-     *
-     * @param callable $eventProcessor The event processor
-     *
-     * @return $this
-     */
-    public function addEventProcessor(callable $eventProcessor): self
-    {
-        $this->eventProcessors[] = $eventProcessor;
-
-        return $this;
-    }
-
-    /**
-     * Adds a new event processor that will be called after {@see Scope::applyToEvent}
+     * Adds a new event processor that will be called after {@see MergedScope::applyToEvent}
      * finished its work.
      *
      * @param callable $eventProcessor The event processor
@@ -418,234 +121,4 @@ public static function getExternalPropagationContext(): ?array
             'span_id' => $spanId,
         ];
     }
-
-    /**
-     * Clears the scope and resets any data it contains.
-     *
-     * @return $this
-     */
-    public function clear(): self
-    {
-        $this->user = null;
-        $this->level = null;
-        $this->span = null;
-        $this->fingerprint = [];
-        $this->breadcrumbs = [];
-        $this->tags = [];
-        $this->flags = [];
-        $this->extra = [];
-        $this->contexts = [];
-        $this->attachments = [];
-
-        return $this;
-    }
-
-    /**
-     * Applies the current context and fingerprint to the event. If the event has
-     * already some breadcrumbs on it, the ones from this scope won't get merged.
-     *
-     * @param Event $event The event object that will be enriched with scope data
-     */
-    public function applyToEvent(Event $event, ?EventHint $hint = null, ?Options $options = null): ?Event
-    {
-        $event->setFingerprint(array_merge($event->getFingerprint(), $this->fingerprint));
-
-        if (empty($event->getBreadcrumbs())) {
-            $event->setBreadcrumb($this->breadcrumbs);
-        }
-
-        if ($this->level !== null) {
-            $event->setLevel($this->level);
-        }
-
-        if (!empty($this->tags)) {
-            $event->setTags(array_merge($this->tags, $event->getTags()));
-        }
-
-        if (!empty($this->flags)) {
-            $event->setContext('flags', [
-                'values' => array_map(static function (array $flag) {
-                    return [
-                        'flag' => key($flag),
-                        'result' => current($flag),
-                    ];
-                }, array_values($this->flags)),
-            ]);
-        }
-
-        if (!empty($this->extra)) {
-            $event->setExtra(array_merge($this->extra, $event->getExtra()));
-        }
-
-        if ($this->user !== null) {
-            $user = $event->getUser();
-
-            if ($user === null) {
-                $user = $this->user;
-            } else {
-                $user = $this->user->merge($user);
-            }
-
-            $event->setUser($user);
-        }
-
-        /**
-         * Apply the trace context to errors if there is a Span on the Scope.
-         * Else fallback to the external propagation context or to the
-         * propagation context.
-         * But do not override a trace context already present.
-         */
-        $externalPropagationContext = null;
-        if ($this->span === null) {
-            $externalPropagationContext = self::getExternalPropagationContext();
-        }
-
-        $traceContext = $this->span !== null
-            ? $this->span->getTraceContext()
-            : ($externalPropagationContext ?? $this->propagationContext->getTraceContext());
-
-        if (!\array_key_exists('trace', $event->getContexts())) {
-            $event->setContext('trace', $traceContext);
-        }
-
-        if ($this->span !== null) {
-            // Apply the dynamic sampling context to errors if there is a Transaction on the Scope
-            $transaction = $this->span->getTransaction();
-            if ($transaction !== null) {
-                $event->setSdkMetadata('dynamic_sampling_context', $transaction->getDynamicSamplingContext());
-            }
-        } elseif ($externalPropagationContext === null) {
-            $dynamicSamplingContext = $this->propagationContext->getDynamicSamplingContext();
-            if ($dynamicSamplingContext === null && $options !== null) {
-                $dynamicSamplingContext = DynamicSamplingContext::fromOptions($options, $this);
-            }
-            $event->setSdkMetadata('dynamic_sampling_context', $dynamicSamplingContext);
-        }
-
-        foreach (array_merge($this->contexts, $event->getContexts()) as $name => $data) {
-            $event->setContext($name, $data);
-        }
-
-        // We create a empty `EventHint` instance to allow processors to always receive a `EventHint` instance even if there wasn't one
-        if ($hint === null) {
-            $hint = new EventHint();
-        }
-
-        if ($event->getType() === EventType::event() || $event->getType() === EventType::transaction()) {
-            if (empty($event->getAttachments())) {
-                $event->setAttachments($this->attachments);
-            }
-        }
-
-        foreach (array_merge(self::$globalEventProcessors, $this->eventProcessors) as $processor) {
-            $event = $processor($event, $hint);
-
-            if ($event === null) {
-                return null;
-            }
-
-            if (!$event instanceof Event) {
-                throw new \InvalidArgumentException(\sprintf('The event processor must return null or an instance of the %s class', Event::class));
-            }
-        }
-
-        return $event;
-    }
-
-    /**
-     * Returns the span that is on the scope.
-     */
-    public function getSpan(): ?Span
-    {
-        return $this->span;
-    }
-
-    /**
-     * Sets the span on the scope.
-     *
-     * @param Span|null $span The span
-     *
-     * @return $this
-     */
-    public function setSpan(?Span $span): self
-    {
-        $this->span = $span;
-
-        return $this;
-    }
-
-    /**
-     * Returns the transaction attached to the scope (if there is one).
-     */
-    public function getTransaction(): ?Transaction
-    {
-        if ($this->span !== null) {
-            return $this->span->getTransaction();
-        }
-
-        return null;
-    }
-
-    public function hasExternalPropagationContext(): bool
-    {
-        return $this->span === null && self::getExternalPropagationContext() !== null;
-    }
-
-    /**
-     * @return array{
-     *     trace_id: string,
-     *     span_id: string,
-     *     parent_span_id?: string,
-     *     data?: array<string, mixed>,
-     *     description?: string,
-     *     op?: string,
-     *     status?: string,
-     *     tags?: array<string, string>,
-     *     origin?: string
-     * }
-     */
-    public function getTraceContext(): array
-    {
-        if ($this->span !== null) {
-            return $this->span->getTraceContext();
-        }
-
-        return self::getExternalPropagationContext() ?? $this->propagationContext->getTraceContext();
-    }
-
-    public function getPropagationContext(): PropagationContext
-    {
-        return $this->propagationContext;
-    }
-
-    public function setPropagationContext(PropagationContext $propagationContext): self
-    {
-        $this->propagationContext = $propagationContext;
-
-        return $this;
-    }
-
-    public function __clone()
-    {
-        if ($this->user !== null) {
-            $this->user = clone $this->user;
-        }
-        if ($this->propagationContext !== null) {
-            $this->propagationContext = clone $this->propagationContext;
-        }
-    }
-
-    public function addAttachment(Attachment $attachment): self
-    {
-        $this->attachments[] = $attachment;
-
-        return $this;
-    }
-
-    public function clearAttachments(): self
-    {
-        $this->attachments = [];
-
-        return $this;
-    }
 }
diff --git a/src/State/ScopeData.php b/src/State/ScopeData.php
new file mode 100644
index 0000000000..202e5d77ea
--- /dev/null
+++ b/src/State/ScopeData.php
@@ -0,0 +1,452 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Sentry\State;
+
+use Sentry\Attachment\Attachment;
+use Sentry\Breadcrumb;
+use Sentry\ClientInterface;
+use Sentry\Event;
+use Sentry\EventHint;
+use Sentry\Severity;
+use Sentry\Tracing\PropagationContext;
+use Sentry\UserDataBag;
+use Sentry\Util\DebugType;
+
+/**
+ * Represents the internal state of a scope and stores all data that is shared between all types of scope.
+ *
+ * This class can be cloned safely.
+ *
+ * @internal
+ */
+class ScopeData
+{
+    /**
+     * @var PropagationContext
+     */
+    private $propagationContext;
+
+    /**
+     * @var ClientInterface The client bound to this scope
+     */
+    private $client;
+
+    /**
+     * @var Breadcrumb[] The list of breadcrumbs recorded in this scope
+     */
+    private $breadcrumbs = [];
+
+    /**
+     * @var UserDataBag|null The user data associated to this scope
+     */
+    private $user;
+
+    /**
+     * @var array<string, array<string, mixed>> The list of contexts associated to this scope
+     */
+    private $contexts = [];
+
+    /**
+     * @var array<string, string> The list of tags associated to this scope
+     */
+    private $tags = [];
+
+    /**
+     * @var array<int, array<string, bool>> The list of flags associated to this scope
+     */
+    private $flags = [];
+
+    /**
+     * @var array<string, mixed> A set of extra data associated to this scope
+     */
+    private $extra = [];
+
+    /**
+     * @var string[] List of fingerprints used to group events together in
+     *               Sentry
+     */
+    private $fingerprint = [];
+
+    /**
+     * @var Severity|null The severity to associate to the events captured in
+     *                    this scope
+     */
+    private $level;
+
+    /**
+     * @var callable[] List of event processors
+     *
+     * @phpstan-var array<callable(Event, EventHint): ?Event>
+     */
+    private $eventProcessors = [];
+
+    /**
+     * @var Attachment[]
+     */
+    private $attachments = [];
+
+    public function __construct(?PropagationContext $propagationContext = null)
+    {
+        $this->propagationContext = $propagationContext ?? PropagationContext::fromDefaults();
+    }
+
+    public function getPropagationContext(): PropagationContext
+    {
+        return $this->propagationContext;
+    }
+
+    public function setPropagationContext(PropagationContext $propagationContext): void
+    {
+        $this->propagationContext = $propagationContext;
+    }
+
+    public function getClient(): ClientInterface
+    {
+        return $this->client;
+    }
+
+    public function setClient(ClientInterface $client): void
+    {
+        $this->client = $client;
+    }
+
+    /**
+     * @return Breadcrumb[]
+     */
+    public function getBreadcrumbs(): array
+    {
+        return $this->breadcrumbs;
+    }
+
+    public function addBreadcrumb(Breadcrumb $breadcrumb, int $maxBreadcrumbs = 100): void
+    {
+        $this->breadcrumbs[] = $breadcrumb;
+        if (\count($this->breadcrumbs) > $maxBreadcrumbs) {
+            $this->breadcrumbs = \array_slice($this->breadcrumbs, -$maxBreadcrumbs);
+        }
+    }
+
+    public function clearBreadcrumbs(): void
+    {
+        $this->breadcrumbs = [];
+    }
+
+    public function getUser(): ?UserDataBag
+    {
+        return $this->user;
+    }
+
+    /**
+     * @param array<string, mixed>|UserDataBag $user
+     */
+    public function setUser($user): void
+    {
+        if (!\is_array($user) && !$user instanceof UserDataBag) {
+            throw new \TypeError(\sprintf('The $user argument must be either an array or an instance of the "%s" class. Got: "%s".', UserDataBag::class, DebugType::getDebugType($user)));
+        }
+
+        if (\is_array($user)) {
+            $user = UserDataBag::createFromArray($user);
+        }
+
+        if ($this->user === null) {
+            $this->user = $user;
+        } else {
+            $this->user = $this->user->merge($user);
+        }
+    }
+
+    public function removeUser(): void
+    {
+        $this->user = null;
+    }
+
+    /**
+     * @return array<string, array<string, mixed>>
+     */
+    public function getContexts(): array
+    {
+        return $this->contexts;
+    }
+
+    /**
+     * @param array<string, mixed> $value
+     */
+    public function setContext(string $name, array $value): void
+    {
+        $this->contexts[$name] = $value;
+    }
+
+    public function removeContext(string $key): void
+    {
+        unset($this->contexts[$key]);
+    }
+
+    /**
+     * @return array<string, string>
+     */
+    public function getTags(): array
+    {
+        return $this->tags;
+    }
+
+    /**
+     * @param array<string, string> $tags
+     */
+    public function setTags(array $tags): void
+    {
+        $this->tags = $tags;
+    }
+
+    public function setTag(string $key, string $value): void
+    {
+        $this->tags[$key] = $value;
+    }
+
+    public function removeTag(string $key): void
+    {
+        unset($this->tags[$key]);
+    }
+
+    /**
+     * @return array<int, array<string, bool>>
+     */
+    public function getFlags(): array
+    {
+        return $this->flags;
+    }
+
+    public function addFeatureFlag(string $key, bool $result): self
+    {
+        // If the flag was already set, remove it first
+        // This basically mimics an LRU cache so that the most recently added flags are kept
+        foreach ($this->flags as $flagIndex => $flag) {
+            if (isset($flag[$key])) {
+                unset($this->flags[$flagIndex]);
+            }
+        }
+
+        // Keep only the most recent MAX_FLAGS flags
+        if (\count($this->flags) >= Scope::MAX_FLAGS) {
+            array_shift($this->flags);
+        }
+
+        $this->flags[] = [$key => $result];
+
+        return $this;
+    }
+
+    /**
+     * @return array<string, mixed>
+     */
+    public function getExtra(): array
+    {
+        return $this->extra;
+    }
+
+    /**
+     * @param array<string, mixed> $extra
+     */
+    public function setExtras(array $extra): void
+    {
+        $this->extra = $extra;
+    }
+
+    /**
+     * @param mixed $value
+     */
+    public function setExtra(string $key, $value): void
+    {
+        $this->extra[$key] = $value;
+    }
+
+    /**
+     * @return string[]
+     */
+    public function getFingerprint(): array
+    {
+        return $this->fingerprint;
+    }
+
+    /**
+     * @param string[] $fingerprint
+     */
+    public function setFingerprint(array $fingerprint): void
+    {
+        $this->fingerprint = $fingerprint;
+    }
+
+    public function getLevel(): ?Severity
+    {
+        return $this->level;
+    }
+
+    public function setLevel(?Severity $level): void
+    {
+        $this->level = $level;
+    }
+
+    /**
+     * @return array<callable(Event, EventHint): ?Event>
+     */
+    public function getEventProcessors(): array
+    {
+        return $this->eventProcessors;
+    }
+
+    /**
+     * @param callable(Event, EventHint): ?Event $eventProcessor
+     */
+    public function addEventProcessor(callable $eventProcessor): void
+    {
+        $this->eventProcessors[] = $eventProcessor;
+    }
+
+    /**
+     * @return Attachment[]
+     */
+    public function getAttachments(): array
+    {
+        return $this->attachments;
+    }
+
+    /**
+     * @param Attachment[] $attachments
+     */
+    public function setAttachments(array $attachments): void
+    {
+        $this->attachments = $attachments;
+    }
+
+    public function addAttachment(Attachment $attachment): void
+    {
+        $this->attachments[] = $attachment;
+    }
+
+    public function clear(): void
+    {
+        $this->user = null;
+        $this->level = null;
+        $this->fingerprint = [];
+        $this->breadcrumbs = [];
+        $this->tags = [];
+        $this->flags = [];
+        $this->extra = [];
+        $this->contexts = [];
+        $this->attachments = [];
+    }
+
+    public function __clone()
+    {
+        if ($this->user !== null) {
+            $this->user = clone $this->user;
+        }
+        $this->propagationContext = clone $this->propagationContext;
+    }
+
+    /**
+     * Merges data of one ScopeData object into the other one. Data stored in $other will have precedence over
+     * $this. It is generally assumed $this refers to the global scope while $other is the isolation scope.
+     */
+    public function merge(self $other): self
+    {
+        $merged = clone $other;
+        $merged->tags = array_merge($this->tags, $other->tags);
+        $merged->extra = array_merge($this->extra, $other->extra);
+        $merged->contexts = array_merge($this->contexts, $other->contexts);
+
+        if ($this->user !== null && $other->user !== null) {
+            $merged->user = (clone $this->user)->merge($other->user);
+        } elseif ($this->user !== null) {
+            $merged->user = clone $this->user;
+        }
+
+        $merged->level = $other->level ?? $this->level;
+        $merged->fingerprint = array_merge($this->fingerprint, $other->fingerprint);
+        $merged->breadcrumbs = self::mergeBreadcrumbs($this->breadcrumbs, $other->breadcrumbs);
+        $merged->flags = self::mergeFlags($this->flags, $other->flags);
+        $merged->attachments = array_merge($this->attachments, $other->attachments);
+        $merged->eventProcessors = array_merge($this->eventProcessors, $other->eventProcessors);
+
+        return $merged;
+    }
+
+    /**
+     * @param Breadcrumb[] $globalBreadcrumbs
+     * @param Breadcrumb[] $isolationBreadcrumbs
+     *
+     * @return Breadcrumb[]
+     */
+    private static function mergeBreadcrumbs(array $globalBreadcrumbs, array $isolationBreadcrumbs): array
+    {
+        if (empty($globalBreadcrumbs)) {
+            return $isolationBreadcrumbs;
+        }
+
+        if (empty($isolationBreadcrumbs)) {
+            return $globalBreadcrumbs;
+        }
+
+        // if the last global is before the first isolation, it means that no global breadcrumb was created after
+        // the first isolation was written, so we can just merge them normally
+        if ($globalBreadcrumbs[\count($globalBreadcrumbs) - 1]->getTimestamp() <= $isolationBreadcrumbs[0]->getTimestamp()) {
+            return array_merge($globalBreadcrumbs, $isolationBreadcrumbs);
+        }
+
+        $globalCount = \count($globalBreadcrumbs);
+        $isolationCount = \count($isolationBreadcrumbs);
+        $globalIndex = 0;
+        $isolationIndex = 0;
+        $merged = [];
+
+        // we iterate over both lists as long as both have elements. Once we reached the end of one list,
+        // we can stop iterating and merge the remaining list fully
+        while ($globalIndex < $globalCount && $isolationIndex < $isolationCount) {
+            if ($globalBreadcrumbs[$globalIndex]->getTimestamp() <= $isolationBreadcrumbs[$isolationIndex]->getTimestamp()) {
+                $merged[] = $globalBreadcrumbs[$globalIndex++];
+            } else {
+                $merged[] = $isolationBreadcrumbs[$isolationIndex++];
+            }
+        }
+
+        return array_merge(
+            $merged,
+            \array_slice($globalBreadcrumbs, $globalIndex),
+            \array_slice($isolationBreadcrumbs, $isolationIndex)
+        );
+    }
+
+    /**
+     * @param array<int, array<string, bool>> $globalFlags
+     * @param array<int, array<string, bool>> $isolationFlags
+     *
+     * @return array<int, array<string, bool>>
+     */
+    private static function mergeFlags(array $globalFlags, array $isolationFlags): array
+    {
+        $flagsByKey = [];
+
+        foreach (array_merge($globalFlags, $isolationFlags) as $flag) {
+            $flagKey = key($flag);
+
+            if ($flagKey === null) {
+                continue;
+            }
+
+            unset($flagsByKey[$flagKey]);
+            $flagsByKey[$flagKey] = current($flag);
+        }
+
+        $flagsByKey = \array_slice($flagsByKey, -Scope::MAX_FLAGS, Scope::MAX_FLAGS, true);
+
+        $flags = [];
+
+        foreach ($flagsByKey as $flagKey => $flagResult) {
+            $flags[] = [$flagKey => $flagResult];
+        }
+
+        return $flags;
+    }
+}
diff --git a/src/Tracing/DynamicSamplingContext.php b/src/Tracing/DynamicSamplingContext.php
index 410b4fc533..714aab6ff3 100644
--- a/src/Tracing/DynamicSamplingContext.php
+++ b/src/Tracing/DynamicSamplingContext.php
@@ -4,9 +4,9 @@
 
 namespace Sentry\Tracing;
 
+use Sentry\ClientInterface;
 use Sentry\Options;
-use Sentry\State\HubInterface;
-use Sentry\State\Scope;
+use Sentry\State\IsolationScope;
 
 /**
  * This class represents the Dynamic Sampling Context (dsc).
@@ -149,7 +149,7 @@ public static function fromHeader(string $header): self
      *
      * @see https://develop.sentry.dev/sdk/performance/dynamic-sampling-context/#baggage-header
      */
-    public static function fromTransaction(Transaction $transaction, HubInterface $hub): self
+    public static function fromTransaction(Transaction $transaction, ClientInterface $client): self
     {
         $samplingContext = new self();
         $samplingContext->set('trace_id', (string) $transaction->getTraceId());
@@ -164,8 +164,6 @@ public static function fromTransaction(Transaction $transaction, HubInterface $h
             $samplingContext->set('transaction', $transaction->getName());
         }
 
-        $client = $hub->getClient();
-
         self::setOrgOptions($client->getOptions(), $samplingContext);
 
         if ($transaction->getSampled() !== null) {
@@ -181,11 +179,19 @@ public static function fromTransaction(Transaction $transaction, HubInterface $h
         return $samplingContext;
     }
 
-    public static function fromOptions(Options $options, Scope $scope): self
+    public static function fromOptions(Options $options, IsolationScope $scope): self
+    {
+        return self::fromOptionsAndPropagationContext($options, $scope->getPropagationContext());
+    }
+
+    /**
+     * @internal
+     */
+    public static function fromOptionsAndPropagationContext(Options $options, PropagationContext $propagationContext): self
     {
         $samplingContext = new self();
-        $samplingContext->set('trace_id', (string) $scope->getPropagationContext()->getTraceId());
-        $samplingContext->set('sample_rand', (string) $scope->getPropagationContext()->getSampleRand());
+        $samplingContext->set('trace_id', (string) $propagationContext->getTraceId());
+        $samplingContext->set('sample_rand', (string) $propagationContext->getSampleRand());
 
         if ($options->getTracesSampleRate() !== null) {
             $samplingContext->set('sample_rate', (string) $options->getTracesSampleRate());
diff --git a/src/Tracing/GuzzleTracingMiddleware.php b/src/Tracing/GuzzleTracingMiddleware.php
index 8c14fe0b07..50d73466d9 100644
--- a/src/Tracing/GuzzleTracingMiddleware.php
+++ b/src/Tracing/GuzzleTracingMiddleware.php
@@ -11,7 +11,8 @@
 use Sentry\Breadcrumb;
 use Sentry\ClientInterface;
 use Sentry\SentrySdk;
-use Sentry\State\HubInterface;
+use Sentry\State\BreadcrumbRecorder;
+use Sentry\State\IsolationScope;
 
 use function Sentry\getBaggage;
 use function Sentry\getTraceparent;
@@ -21,13 +22,13 @@
  */
 final class GuzzleTracingMiddleware
 {
-    public static function trace(?HubInterface $hub = null): \Closure
+    public static function trace(?IsolationScope $scope = null): \Closure
     {
-        return static function (callable $handler) use ($hub): \Closure {
-            return static function (RequestInterface $request, array $options) use ($hub, $handler) {
-                $hub = $hub ?? SentrySdk::getCurrentHub();
-                $client = $hub->getClient();
-                $parentSpan = $hub->getSpan();
+        return static function (callable $handler) use ($scope): \Closure {
+            return static function (RequestInterface $request, array $options) use ($handler, $scope) {
+                $scope = $scope ?? SentrySdk::getIsolationScope();
+                $client = SentrySdk::getClient($scope);
+                $parentSpan = $scope->getSpan();
 
                 $partialUri = Uri::fromParts([
                     'scheme' => $request->getUri()->getScheme(),
@@ -59,28 +60,27 @@ public static function trace(?HubInterface $hub = null): \Closure
 
                     $childSpan = $parentSpan->startChild($spanContext);
 
-                    $hub->setSpan($childSpan);
+                    $scope->setSpan($childSpan);
                 }
 
                 if (self::shouldAttachTracingHeaders($client, $request)) {
-                    $traceParent = getTraceparent();
+                    $traceParent = getTraceparent($scope);
                     if ($traceParent !== '') {
                         $request = $request->withHeader('sentry-trace', $traceParent);
                     }
 
-                    $baggage = getBaggage();
+                    $baggage = getBaggage($scope);
                     if ($baggage !== '') {
                         $request = $request->withHeader('baggage', $baggage);
                     }
                 }
 
-                $handlerPromiseCallback = static function ($responseOrException) use ($hub, $spanAndBreadcrumbData, $childSpan, $parentSpan, $partialUri) {
+                $handlerPromiseCallback = static function ($responseOrException) use ($client, $scope, $spanAndBreadcrumbData, $childSpan, $parentSpan, $partialUri) {
                     if ($childSpan !== null) {
-                        // We finish the span (which means setting the span end timestamp) first to ensure the measured time
-                        // the span spans is as close to only the HTTP request time and do the data collection afterwards
+                        // We finish the span first to keep the measured duration as close as possible to the HTTP request time.
                         $childSpan->finish();
 
-                        $hub->setSpan($parentSpan);
+                        $scope->setSpan($parentSpan);
                     }
 
                     $response = null;
@@ -113,7 +113,7 @@ public static function trace(?HubInterface $hub = null): \Closure
                         }
                     }
 
-                    $hub->addBreadcrumb(new Breadcrumb(
+                    BreadcrumbRecorder::record($client, $scope, new Breadcrumb(
                         $breadcrumbLevel,
                         Breadcrumb::TYPE_HTTP,
                         'http',
diff --git a/src/Tracing/PropagationContext.php b/src/Tracing/PropagationContext.php
index e2d525d5d6..497c513c0c 100644
--- a/src/Tracing/PropagationContext.php
+++ b/src/Tracing/PropagationContext.php
@@ -5,7 +5,6 @@
 namespace Sentry\Tracing;
 
 use Sentry\SentrySdk;
-use Sentry\State\Scope;
 use Sentry\Tracing\Traits\TraceHeaderParserTrait;
 
 final class PropagationContext
@@ -84,12 +83,10 @@ public function toTraceparent(): string
     public function toBaggage(): string
     {
         if ($this->dynamicSamplingContext === null) {
-            $hub = SentrySdk::getCurrentHub();
-            $options = $hub->getClient()->getOptions();
-
-            $hub->configureScope(function (Scope $scope) use ($options) {
-                $this->dynamicSamplingContext = DynamicSamplingContext::fromOptions($options, $scope);
-            });
+            $this->dynamicSamplingContext = DynamicSamplingContext::fromOptionsAndPropagationContext(
+                SentrySdk::getClient()->getOptions(),
+                $this
+            );
         }
 
         return (string) $this->dynamicSamplingContext;
diff --git a/src/Tracing/Span.php b/src/Tracing/Span.php
index e8df25b88d..faebe8a476 100644
--- a/src/Tracing/Span.php
+++ b/src/Tracing/Span.php
@@ -6,7 +6,6 @@
 
 use Sentry\EventId;
 use Sentry\SentrySdk;
-use Sentry\State\Scope;
 
 /**
  * This class stores all the information about a span.
@@ -299,11 +298,9 @@ public function setStatus(?SpanStatus $status)
      */
     public function setHttpStatus(int $statusCode)
     {
-        SentrySdk::getCurrentHub()->configureScope(static function (Scope $scope) use ($statusCode) {
-            $scope->setContext('response', [
-                'status_code' => $statusCode,
-            ]);
-        });
+        SentrySdk::getIsolationScope()->setContext('response', [
+            'status_code' => $statusCode,
+        ]);
 
         $status = SpanStatus::createFromHttpStatusCode($statusCode);
 
diff --git a/src/Tracing/Traits/TraceHeaderParserTrait.php b/src/Tracing/Traits/TraceHeaderParserTrait.php
index 3accc180b1..69933f22bb 100644
--- a/src/Tracing/Traits/TraceHeaderParserTrait.php
+++ b/src/Tracing/Traits/TraceHeaderParserTrait.php
@@ -127,8 +127,7 @@ private static function parseSampleRand(DynamicSamplingContext $samplingContext)
             }
         }
 
-        $hub = SentrySdk::getCurrentHub();
-        $client = $hub->getClient();
+        $client = SentrySdk::getClient();
         $client->getOptions()->getLoggerOrNullLogger()->debug(
             'Ignoring invalid sentry-sample_rand baggage value because it must be a numeric value in the range [0, 1).',
             ['sample_rand' => $sampleRand]
@@ -139,8 +138,7 @@ private static function parseSampleRand(DynamicSamplingContext $samplingContext)
 
     private static function shouldContinueTrace(DynamicSamplingContext $samplingContext): bool
     {
-        $hub = SentrySdk::getCurrentHub();
-        $client = $hub->getClient();
+        $client = SentrySdk::getClient();
 
         $options = $client->getOptions();
         $clientOrgId = $options->getOrgId();
diff --git a/src/Tracing/Transaction.php b/src/Tracing/Transaction.php
index e2baa09b90..2b3cba6b11 100644
--- a/src/Tracing/Transaction.php
+++ b/src/Tracing/Transaction.php
@@ -6,9 +6,11 @@
 
 use Sentry\Event;
 use Sentry\EventId;
+use Sentry\Options;
 use Sentry\Profiling\Profiler;
 use Sentry\SentrySdk;
-use Sentry\State\HubInterface;
+use Sentry\State\EventRecorder;
+use Sentry\State\IsolationScope;
 
 /**
  * This class stores all the information about a Transaction.
@@ -16,14 +18,14 @@
 final class Transaction extends Span
 {
     /**
-     * @var HubInterface The hub instance
+     * @var string Name of the transaction
      */
-    private $hub;
+    private $name;
 
     /**
-     * @var string Name of the transaction
+     * @var IsolationScope
      */
-    private $name;
+    private $scope;
 
     /**
      * @var Transaction The transaction
@@ -44,16 +46,15 @@ final class Transaction extends Span
      * Span constructor.
      *
      * @param TransactionContext $context The context to create the transaction with
-     * @param HubInterface|null  $hub     Instance of a hub to flush the transaction
      *
      * @internal
      */
-    public function __construct(TransactionContext $context, ?HubInterface $hub = null)
+    public function __construct(TransactionContext $context, ?IsolationScope $scope = null)
     {
         parent::__construct($context);
 
-        $this->hub = $hub ?? SentrySdk::getCurrentHub();
         $this->name = $context->getName();
+        $this->scope = $scope ?? SentrySdk::getIsolationScope();
         $this->metadata = $context->getMetadata();
         $this->transaction = $this;
     }
@@ -97,7 +98,7 @@ public function getDynamicSamplingContext(): DynamicSamplingContext
             return $this->metadata->getDynamicSamplingContext();
         }
 
-        $samplingContext = DynamicSamplingContext::fromTransaction($this->transaction, $this->hub);
+        $samplingContext = DynamicSamplingContext::fromTransaction($this->transaction, SentrySdk::getClient($this->scope));
         $this->getMetadata()->setDynamicSamplingContext($samplingContext);
 
         return $samplingContext;
@@ -119,10 +120,10 @@ public function initSpanRecorder(int $maxSpans = 1000): self
         return $this;
     }
 
-    public function initProfiler(): Profiler
+    public function initProfiler(?Options $options = null): Profiler
     {
         if ($this->profiler === null) {
-            $this->profiler = new Profiler($this->hub->getClient()->getOptions());
+            $this->profiler = new Profiler($options ?? SentrySdk::getClient($this->scope)->getOptions());
         }
 
         return $this->profiler;
@@ -187,6 +188,6 @@ public function finish(?float $endTimestamp = null): ?EventId
             }
         }
 
-        return $this->hub->captureEvent($event);
+        return EventRecorder::captureEvent($event, null, $this->scope);
     }
 }
diff --git a/src/Tracing/TransactionSampler.php b/src/Tracing/TransactionSampler.php
new file mode 100644
index 0000000000..ef6a284eca
--- /dev/null
+++ b/src/Tracing/TransactionSampler.php
@@ -0,0 +1,172 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Sentry\Tracing;
+
+use Sentry\Options;
+
+/**
+ * Applies tracing and profiling sampling decisions to transactions.
+ *
+ * @internal
+ */
+final class TransactionSampler
+{
+    private function __construct()
+    {
+    }
+
+    /**
+     * @param array<string, mixed> $customSamplingContext Additional context that will be passed to the {@see SamplingContext}
+     */
+    public static function startTransaction(Options $options, TransactionContext $context, array $customSamplingContext = []): Transaction
+    {
+        $transaction = new Transaction($context);
+        $logger = $options->getLoggerOrNullLogger();
+
+        if (!$options->isTracingEnabled()) {
+            $transaction->setSampled(false);
+
+            $logger->warning(\sprintf('Transaction [%s] was started but tracing is not enabled.', (string) $transaction->getTraceId()), ['context' => $context]);
+
+            return $transaction;
+        }
+
+        $samplingContext = SamplingContext::getDefault($context);
+        $samplingContext->setAdditionalContext($customSamplingContext);
+
+        $sampleSource = 'context';
+        $sampleRand = $context->getMetadata()->getSampleRand() ?? 0.0;
+
+        if ($transaction->getSampled() === null) {
+            $tracesSampler = $options->getTracesSampler();
+
+            if ($tracesSampler !== null) {
+                $sampleRate = $tracesSampler($samplingContext);
+                $sampleSource = 'config:traces_sampler';
+            } else {
+                $parentSampleRate = $context->getMetadata()->getParentSamplingRate();
+                if ($parentSampleRate !== null) {
+                    $sampleRate = $parentSampleRate;
+                    $sampleSource = 'parent:sample_rate';
+                } else {
+                    $sampleRate = self::getSampleRate(
+                        $samplingContext->getParentSampled(),
+                        $options->getTracesSampleRate() ?? 0
+                    );
+                    $sampleSource = $samplingContext->getParentSampled() !== null ? 'parent:sampling_decision' : 'config:traces_sample_rate';
+                }
+            }
+
+            if (!self::isValidSampleRate($sampleRate)) {
+                $transaction->setSampled(false);
+
+                $logger->warning(\sprintf('Transaction [%s] was started but not sampled because sample rate (decided by %s) is invalid.', (string) $transaction->getTraceId(), $sampleSource), ['context' => $context]);
+
+                return $transaction;
+            }
+
+            $transaction->getMetadata()->setSamplingRate($sampleRate);
+
+            // Always overwrite the sample_rate in the DSC
+            $dynamicSamplingContext = $context->getMetadata()->getDynamicSamplingContext();
+            if ($dynamicSamplingContext !== null) {
+                $dynamicSamplingContext->set('sample_rate', (string) $sampleRate, true);
+            }
+
+            if ($sampleRate === 0.0) {
+                $transaction->setSampled(false);
+
+                $logger->info(\sprintf('Transaction [%s] was started but not sampled because sample rate (decided by %s) is %s.', (string) $transaction->getTraceId(), $sampleSource, $sampleRate), ['context' => $context]);
+
+                return $transaction;
+            }
+
+            $transaction->setSampled($sampleRand < $sampleRate);
+        }
+
+        if (!$transaction->getSampled()) {
+            $logger->info(\sprintf('Transaction [%s] was started but not sampled, decided by %s.', (string) $transaction->getTraceId(), $sampleSource), ['context' => $context]);
+
+            return $transaction;
+        }
+
+        $logger->info(\sprintf('Transaction [%s] was started and sampled, decided by %s.', (string) $transaction->getTraceId(), $sampleSource), ['context' => $context]);
+
+        $transaction->initSpanRecorder();
+
+        $profilesSampleSource = 'config:profiles_sample_rate';
+        $profilesSampler = $options->getProfilesSampler();
+
+        if ($profilesSampler !== null) {
+            $profilesSampleRate = $profilesSampler($samplingContext);
+            $profilesSampleSource = 'config:profiles_sampler';
+        } else {
+            $profilesSampleRate = $options->getProfilesSampleRate();
+        }
+
+        if ($profilesSampleRate === null) {
+            $logger->info(\sprintf('Transaction [%s] is not profiling because neither `profiles_sample_rate` nor `profiles_sampler` option is set.', (string) $transaction->getTraceId()));
+        } elseif (!self::isValidSampleRate($profilesSampleRate)) {
+            $logger->warning(\sprintf('Transaction [%s] is not profiling because profile sample rate (decided by %s) is invalid.', (string) $transaction->getTraceId(), $profilesSampleSource));
+        } elseif (self::sampleRate($profilesSampleRate)) {
+            $logger->info(\sprintf('Transaction [%s] started profiling because it was sampled.', (string) $transaction->getTraceId()));
+
+            $transaction->initProfiler($options)->start();
+        } else {
+            $logger->info(\sprintf('Transaction [%s] is not profiling because it was not sampled.', (string) $transaction->getTraceId()));
+        }
+
+        return $transaction;
+    }
+
+    private static function getSampleRate(?bool $hasParentBeenSampled, float $fallbackSampleRate): float
+    {
+        if ($hasParentBeenSampled === true) {
+            return 1.0;
+        }
+
+        if ($hasParentBeenSampled === false) {
+            return 0.0;
+        }
+
+        return $fallbackSampleRate;
+    }
+
+    /**
+     * @param mixed $sampleRate
+     */
+    private static function sampleRate($sampleRate): bool
+    {
+        if (!\is_float($sampleRate) && !\is_int($sampleRate)) {
+            return false;
+        }
+
+        if ($sampleRate === 0.0) {
+            return false;
+        }
+
+        if ($sampleRate === 1.0) {
+            return true;
+        }
+
+        return mt_rand(0, mt_getrandmax() - 1) / mt_getrandmax() < (float) $sampleRate;
+    }
+
+    /**
+     * @param mixed $sampleRate
+     */
+    private static function isValidSampleRate($sampleRate): bool
+    {
+        if (!\is_float($sampleRate) && !\is_int($sampleRate)) {
+            return false;
+        }
+
+        if ($sampleRate < 0 || $sampleRate > 1) {
+            return false;
+        }
+
+        return true;
+    }
+}
diff --git a/src/UserDataBag.php b/src/UserDataBag.php
index 5fecb478c9..bff8118852 100644
--- a/src/UserDataBag.php
+++ b/src/UserDataBag.php
@@ -195,13 +195,9 @@ public function setIpAddress(?string $ipAddress): self
             }
 
             if (filter_var($ipAddress, \FILTER_VALIDATE_IP) === false) {
-                $client = SentrySdk::getCurrentHub()->getClient();
-
-                if ($client !== null) {
-                    $client->getOptions()->getLoggerOrNullLogger()->debug(
-                        \sprintf('The "%s" value is not a valid IP address.', $ipAddress)
-                    );
-                }
+                SentrySdk::getClient()->getOptions()->getLoggerOrNullLogger()->debug(
+                    \sprintf('The "%s" value is not a valid IP address.', $ipAddress)
+                );
 
                 return $this;
             }
diff --git a/src/functions.php b/src/functions.php
index 0935d739fc..84aadd28e1 100644
--- a/src/functions.php
+++ b/src/functions.php
@@ -10,6 +10,10 @@
 use Sentry\Integration\OTLPIntegration;
 use Sentry\Logs\Logs;
 use Sentry\Metrics\TraceMetrics;
+use Sentry\State\BreadcrumbRecorder;
+use Sentry\State\EventRecorder;
+use Sentry\State\GlobalScope;
+use Sentry\State\IsolationScope;
 use Sentry\State\Scope;
 use Sentry\Tracing\PropagationContext;
 use Sentry\Tracing\SpanContext;
@@ -18,7 +22,7 @@
 use Sentry\Transport\TransportInterface;
 
 /**
- * Creates a new Client and Hub which will be set as current.
+ * Creates a new Client and initializes the SDK.
  *
  * @param array{
  *     attach_stacktrace?: bool,
@@ -74,7 +78,22 @@ function init(array $options = []): void
 {
     $client = ClientBuilder::create($options)->getClient();
 
-    SentrySdk::init()->bindClient($client);
+    SentrySdk::init($client);
+}
+
+function getGlobalScope(): GlobalScope
+{
+    return SentrySdk::getGlobalScope();
+}
+
+function getIsolationScope(): IsolationScope
+{
+    return SentrySdk::getIsolationScope();
+}
+
+function getClient(): ClientInterface
+{
+    return SentrySdk::getClient();
 }
 
 /**
@@ -86,7 +105,7 @@ function init(array $options = []): void
  */
 function captureMessage(string $message, ?Severity $level = null, ?EventHint $hint = null): ?EventId
 {
-    return SentrySdk::getCurrentHub()->captureMessage($message, $level, $hint);
+    return EventRecorder::captureMessage($message, $level, $hint);
 }
 
 /**
@@ -97,7 +116,7 @@ function captureMessage(string $message, ?Severity $level = null, ?EventHint $hi
  */
 function captureException(\Throwable $exception, ?EventHint $hint = null): ?EventId
 {
-    return SentrySdk::getCurrentHub()->captureException($exception, $hint);
+    return EventRecorder::captureException($exception, $hint);
 }
 
 /**
@@ -108,7 +127,7 @@ function captureException(\Throwable $exception, ?EventHint $hint = null): ?Even
  */
 function captureEvent(Event $event, ?EventHint $hint = null): ?EventId
 {
-    return SentrySdk::getCurrentHub()->captureEvent($event, $hint);
+    return EventRecorder::captureEvent($event, $hint);
 }
 
 /**
@@ -118,7 +137,7 @@ function captureEvent(Event $event, ?EventHint $hint = null): ?EventId
  */
 function captureLastError(?EventHint $hint = null): ?EventId
 {
-    return SentrySdk::getCurrentHub()->captureLastError($hint);
+    return EventRecorder::captureLastError($hint);
 }
 
 /**
@@ -132,7 +151,7 @@ function captureLastError(?EventHint $hint = null): ?EventId
  */
 function captureCheckIn(string $slug, CheckInStatus $status, $duration = null, ?MonitorConfig $monitorConfig = null, ?string $checkInId = null): ?string
 {
-    return SentrySdk::getCurrentHub()->captureCheckIn($slug, $status, $duration, $monitorConfig, $checkInId);
+    return EventRecorder::captureCheckIn($slug, $status, $duration, $monitorConfig, $checkInId);
 }
 
 /**
@@ -146,7 +165,7 @@ function captureCheckIn(string $slug, CheckInStatus $status, $duration = null, ?
  */
 function withMonitor(string $slug, callable $callback, ?MonitorConfig $monitorConfig = null)
 {
-    $checkInId = SentrySdk::getCurrentHub()->captureCheckIn($slug, CheckInStatus::inProgress(), null, $monitorConfig);
+    $checkInId = captureCheckIn($slug, CheckInStatus::inProgress(), null, $monitorConfig);
 
     $status = CheckInStatus::ok();
     $duration = 0;
@@ -162,7 +181,7 @@ function withMonitor(string $slug, callable $callback, ?MonitorConfig $monitorCo
 
         throw $e;
     } finally {
-        SentrySdk::getCurrentHub()->captureCheckIn($slug, $status, $duration, $monitorConfig, $checkInId);
+        captureCheckIn($slug, $status, $duration, $monitorConfig, $checkInId);
     }
 }
 
@@ -180,11 +199,12 @@ function withMonitor(string $slug, callable $callback, ?MonitorConfig $monitorCo
  */
 function addBreadcrumb($category, ?string $message = null, array $metadata = [], string $level = Breadcrumb::LEVEL_INFO, string $type = Breadcrumb::TYPE_DEFAULT, ?float $timestamp = null): void
 {
-    SentrySdk::getCurrentHub()->addBreadcrumb(
-        $category instanceof Breadcrumb
-            ? $category
-            : new Breadcrumb($level, $type, $category, $message, $metadata, $timestamp)
-    );
+    $scope = SentrySdk::getIsolationScope();
+    $breadcrumb = $category instanceof Breadcrumb
+        ? $category
+        : new Breadcrumb($level, $type, $category, $message, $metadata, $timestamp);
+
+    BreadcrumbRecorder::record(SentrySdk::getClient($scope), $scope, $breadcrumb);
 }
 
 /**
@@ -195,7 +215,7 @@ function addBreadcrumb($category, ?string $message = null, array $metadata = [],
  */
 function configureScope(callable $callback): void
 {
-    SentrySdk::getCurrentHub()->configureScope($callback);
+    $callback(SentrySdk::getIsolationScope());
 }
 
 /**
@@ -211,10 +231,38 @@ function configureScope(callable $callback): void
  * @return mixed|void The callback's return value, upon successful execution
  *
  * @phpstan-return T
+ *
+ * @deprecated This function will be removed in a follow-up PR. Use {@see withIsolationScope()} instead.
  */
 function withScope(callable $callback)
 {
-    return SentrySdk::getCurrentHub()->withScope($callback);
+    return withIsolationScope($callback);
+}
+
+/**
+ * Forks the current isolation scope for the duration of the callback.
+ *
+ * @param callable $callback The callback to be executed
+ *
+ * @phpstan-template T
+ *
+ * @phpstan-param callable(IsolationScope): T $callback
+ *
+ * @return mixed|void The callback's return value, upon successful execution
+ *
+ * @phpstan-return T
+ */
+function withIsolationScope(callable $callback)
+{
+    $context = SentrySdk::getCurrentRuntimeContext();
+    $previousScope = $context->getIsolationScope();
+    $context->setIsolationScope(clone $previousScope);
+
+    try {
+        return $callback($context->getIsolationScope());
+    } finally {
+        $context->setIsolationScope($previousScope);
+    }
 }
 
 function startContext(): void
@@ -268,7 +316,7 @@ function withContext(callable $callback, ?int $timeout = null)
  */
 function startTransaction(TransactionContext $context, array $customSamplingContext = []): Transaction
 {
-    return SentrySdk::getCurrentHub()->startTransaction($context, $customSamplingContext);
+    return Tracing\TransactionSampler::startTransaction(SentrySdk::getClient()->getOptions(), $context, $customSamplingContext);
 }
 
 /**
@@ -277,14 +325,14 @@ function startTransaction(TransactionContext $context, array $customSamplingCont
  *
  * @template T
  *
- * @param callable(Scope): T $trace   The callable that is going to be traced
- * @param SpanContext        $context The context of the span to be created
+ * @param callable(IsolationScope): T $trace   The callable that is going to be traced
+ * @param SpanContext                 $context The context of the span to be created
  *
  * @return T
  */
 function trace(callable $trace, SpanContext $context)
 {
-    return SentrySdk::getCurrentHub()->withScope(static function (Scope $scope) use ($context, $trace) {
+    return withIsolationScope(static function (IsolationScope $scope) use ($context, $trace) {
         $parentSpan = $scope->getSpan();
         $span = null;
 
@@ -314,10 +362,9 @@ function trace(callable $trace, SpanContext $context)
  */
 function getOtlpTracesEndpointUrl(): ?string
 {
-    $hub = SentrySdk::getCurrentHub();
-    $client = $hub->getClient();
+    $client = SentrySdk::getClient();
 
-    $integration = $hub->getIntegration(OTLPIntegration::class);
+    $integration = $client->getIntegration(OTLPIntegration::class);
     if ($integration instanceof OTLPIntegration && $integration->getCollectorUrl() !== null) {
         return $integration->getCollectorUrl();
     }
@@ -336,29 +383,24 @@ function getOtlpTracesEndpointUrl(): ?string
  * This function is context aware, as in it either returns the traceparent based
  * on the current span, or the scope's propagation context.
  */
-function getTraceparent(): string
+function getTraceparent(?IsolationScope $scope = null): string
 {
-    $hub = SentrySdk::getCurrentHub();
-    $client = $hub->getClient();
+    $scope = $scope ?? SentrySdk::getIsolationScope();
+    $client = SentrySdk::getClient($scope);
     $options = $client->getOptions();
 
     if ($options->isTracingEnabled()) {
-        $span = SentrySdk::getCurrentHub()->getSpan();
+        $span = $scope->getSpan();
         if ($span !== null) {
             return $span->toTraceparent();
         }
     }
 
-    $traceParent = '';
-    $hub->configureScope(static function (Scope $scope) use (&$traceParent) {
-        if ($scope->hasExternalPropagationContext()) {
-            return;
-        }
-
-        $traceParent = $scope->getPropagationContext()->toTraceparent();
-    });
+    if ($scope->hasExternalPropagationContext()) {
+        return '';
+    }
 
-    return $traceParent;
+    return $scope->getPropagationContext()->toTraceparent();
 }
 
 /**
@@ -367,29 +409,24 @@ function getTraceparent(): string
  * This function is context aware, as in it either returns the baggage based
  * on the current span or the scope's propagation context.
  */
-function getBaggage(): string
+function getBaggage(?IsolationScope $scope = null): string
 {
-    $hub = SentrySdk::getCurrentHub();
-    $client = $hub->getClient();
+    $scope = $scope ?? SentrySdk::getIsolationScope();
+    $client = SentrySdk::getClient($scope);
     $options = $client->getOptions();
 
     if ($options->isTracingEnabled()) {
-        $span = SentrySdk::getCurrentHub()->getSpan();
+        $span = $scope->getSpan();
         if ($span !== null) {
             return $span->toBaggage();
         }
     }
 
-    $baggage = '';
-    $hub->configureScope(static function (Scope $scope) use (&$baggage) {
-        if ($scope->hasExternalPropagationContext()) {
-            return;
-        }
-
-        $baggage = $scope->getPropagationContext()->toBaggage();
-    });
+    if ($scope->hasExternalPropagationContext()) {
+        return '';
+    }
 
-    return $baggage;
+    return $scope->getPropagationContext()->toBaggage();
 }
 
 /**
@@ -420,10 +457,7 @@ function continueTrace(string $sentryTrace, string $baggage): TransactionContext
         $propagationContext->setDynamicSamplingContext($dynamicSamplingContext);
     }
 
-    $hub = SentrySdk::getCurrentHub();
-    $hub->configureScope(static function (Scope $scope) use ($propagationContext): void {
-        $scope->setPropagationContext($propagationContext);
-    });
+    SentrySdk::getIsolationScope()->setPropagationContext($propagationContext);
 
     return $transactionContext;
 }
@@ -452,9 +486,7 @@ function traceMetrics(): TraceMetrics
  */
 function addFeatureFlag(string $name, bool $result): void
 {
-    SentrySdk::getCurrentHub()->configureScope(static function (Scope $scope) use ($name, $result) {
-        $scope->addFeatureFlag($name, $result);
-    });
+    SentrySdk::getIsolationScope()->addFeatureFlag($name, $result);
 }
 
 /**
diff --git a/tests/ClientReport/ClientReportAggregatorTest.php b/tests/ClientReport/ClientReportAggregatorTest.php
index 7766c7ea50..d59dbda4a3 100644
--- a/tests/ClientReport/ClientReportAggregatorTest.php
+++ b/tests/ClientReport/ClientReportAggregatorTest.php
@@ -11,11 +11,12 @@
 use Sentry\NoOpClient;
 use Sentry\Options;
 use Sentry\SentrySdk;
-use Sentry\State\Hub;
 use Sentry\Tests\StubLogger;
 use Sentry\Tests\StubTransport;
 use Sentry\Transport\DataCategory;
 
+use function Sentry\captureMessage;
+
 class ClientReportAggregatorTest extends TestCase
 {
     protected function setUp(): void
@@ -23,7 +24,7 @@ protected function setUp(): void
         ini_set('zend.exception_ignore_args', '0');
         StubTransport::$events = [];
         StubLogger::$logs = [];
-        SentrySdk::init()->bindClient(new Client(new Options([
+        SentrySdk::init(new Client(new Options([
             'logger' => StubLogger::getInstance(),
         ]), StubTransport::getInstance()));
     }
@@ -69,16 +70,15 @@ public function testClientReportAggregation(): void
 
     public function testFlushDoesNotOverwriteLastEventId(): void
     {
-        $hub = SentrySdk::getCurrentHub();
-        $eventId = $hub->captureMessage('foo');
+        $eventId = captureMessage('foo');
 
         $this->assertNotNull($eventId);
-        $this->assertSame($eventId, $hub->getLastEventId());
+        $this->assertSame($eventId, SentrySdk::getLastEventId());
 
         ClientReportAggregator::getInstance()->add(DataCategory::profile(), Reason::eventProcessor(), 10);
         ClientReportAggregator::getInstance()->flush();
 
-        $this->assertSame($eventId, $hub->getLastEventId());
+        $this->assertSame($eventId, SentrySdk::getLastEventId());
     }
 
     public function testNegativeQuantityDiscarded(): void
@@ -103,13 +103,13 @@ public function testZeroQuantityDiscarded(): void
 
     public function testNegativeQuantityDiscardedWhenNoClientIsBound(): void
     {
-        SentrySdk::setCurrentHub(new Hub(new NoOpClient()));
+        SentrySdk::init(new NoOpClient());
 
         ClientReportAggregator::getInstance()->add(DataCategory::profile(), Reason::eventProcessor(), -10);
 
-        SentrySdk::setCurrentHub(new Hub(new Client(new Options([
+        SentrySdk::init(new Client(new Options([
             'logger' => StubLogger::getInstance(),
-        ]), StubTransport::getInstance())));
+        ]), StubTransport::getInstance()));
 
         ClientReportAggregator::getInstance()->flush();
 
diff --git a/tests/ClientTest.php b/tests/ClientTest.php
index 6f23fba983..c6fef94c2f 100644
--- a/tests/ClientTest.php
+++ b/tests/ClientTest.php
@@ -20,6 +20,7 @@
 use Sentry\Serializer\RepresentationSerializerInterface;
 use Sentry\Severity;
 use Sentry\Stacktrace;
+use Sentry\State\IsolationScope;
 use Sentry\State\Scope;
 use Sentry\Transport\Result;
 use Sentry\Transport\ResultStatus;
@@ -69,7 +70,7 @@ public function setupOnce(): void
             $logger
         );
 
-        $client->captureEvent(Event::createEvent(), null, new Scope());
+        $client->captureEvent(Event::createEvent(), null, new IsolationScope());
 
         $this->assertTrue($integrationCalled);
     }
@@ -966,7 +967,7 @@ public function testProcessEventDiscardsEventWhenEventProcessorReturnsNull(): vo
                                ->setLogger($logger)
                                ->getClient();
 
-        $scope = new Scope();
+        $scope = new IsolationScope();
         $scope->addEventProcessor(static function () {
             return null;
         });
diff --git a/tests/Fixtures/OpenTelemetry/TestDiscoveryStrategy.php b/tests/Fixtures/OpenTelemetry/TestDiscoveryStrategy.php
index 6477cf1900..2144bd1f7a 100644
--- a/tests/Fixtures/OpenTelemetry/TestDiscoveryStrategy.php
+++ b/tests/Fixtures/OpenTelemetry/TestDiscoveryStrategy.php
@@ -4,6 +4,7 @@
 
 namespace Sentry\Tests\Fixtures\OpenTelemetry;
 
+use GuzzleHttp\Psr7\HttpFactory;
 use Nyholm\Psr7\Factory\Psr17Factory;
 use Psr\Http\Client\ClientInterface;
 use Psr\Http\Message\RequestFactoryInterface;
@@ -21,7 +22,10 @@ public static function getCandidates(string $type): array
         }
 
         if (is_a(RequestFactoryInterface::class, $type, true) || is_a(StreamFactoryInterface::class, $type, true)) {
-            return [['class' => Psr17Factory::class, 'condition' => Psr17Factory::class]];
+            return [
+                ['class' => HttpFactory::class, 'condition' => HttpFactory::class],
+                ['class' => Psr17Factory::class, 'condition' => Psr17Factory::class],
+            ];
         }
 
         return [];
diff --git a/tests/Fixtures/runtime/frankenphp/index.php b/tests/Fixtures/runtime/frankenphp/index.php
index bbcceb5bb3..e0367175ee 100644
--- a/tests/Fixtures/runtime/frankenphp/index.php
+++ b/tests/Fixtures/runtime/frankenphp/index.php
@@ -4,9 +4,7 @@
 
 use Sentry\Event;
 use Sentry\SentrySdk;
-use Sentry\State\Scope;
 
-use function Sentry\configureScope;
 use function Sentry\getTraceparent;
 use function Sentry\init;
 use function Sentry\withContext;
@@ -20,9 +18,7 @@
     'default_integrations' => false,
 ]);
 
-configureScope(static function (Scope $scope): void {
-    $scope->setTag('baseline', 'yes');
-});
+SentrySdk::getGlobalScope()->setTag('baseline', 'yes');
 
 $handler = static function (): void {
     $path = parse_url($_SERVER['REQUEST_URI'] ?? '/', \PHP_URL_PATH);
@@ -46,18 +42,14 @@
     $leakTag = isset($_GET['leak']) ? (string) $_GET['leak'] : null;
 
     withContext(static function () use ($requestTag, $leakTag): void {
-        configureScope(static function (Scope $scope) use ($requestTag, $leakTag): void {
-            $scope->setTag('request', $requestTag);
+        SentrySdk::getIsolationScope()->setTag('request', $requestTag);
 
-            if ($leakTag !== null) {
-                $scope->setTag('leak', $leakTag);
-            }
-        });
+        if ($leakTag !== null) {
+            SentrySdk::getIsolationScope()->setTag('leak', $leakTag);
+        }
 
         $event = Event::createEvent();
-        configureScope(static function (Scope $scope) use (&$event): void {
-            $event = $scope->applyToEvent($event);
-        });
+        $event = SentrySdk::getGlobalScope()->merge(SentrySdk::getIsolationScope())->applyToEvent($event);
 
         $tags = [];
 
diff --git a/tests/Fixtures/runtime/roadrunner-worker.php b/tests/Fixtures/runtime/roadrunner-worker.php
index 6a4680da83..f8d6bf79d6 100644
--- a/tests/Fixtures/runtime/roadrunner-worker.php
+++ b/tests/Fixtures/runtime/roadrunner-worker.php
@@ -6,11 +6,9 @@
 use Nyholm\Psr7\Response;
 use Sentry\Event;
 use Sentry\SentrySdk;
-use Sentry\State\Scope;
 use Spiral\RoadRunner\Http\PSR7Worker;
 use Spiral\RoadRunner\Worker;
 
-use function Sentry\configureScope;
 use function Sentry\getTraceparent;
 use function Sentry\init;
 use function Sentry\withContext;
@@ -37,9 +35,7 @@
     'default_integrations' => false,
 ]);
 
-configureScope(static function (Scope $scope): void {
-    $scope->setTag('baseline', 'yes');
-});
+SentrySdk::getGlobalScope()->setTag('baseline', 'yes');
 
 $factory = new Psr17Factory();
 $worker = Worker::create();
@@ -102,18 +98,14 @@ function handleRequest($request): Response
     $leakTag = isset($query['leak']) ? (string) $query['leak'] : null;
 
     $payload = withContext(static function () use ($requestTag, $leakTag): string {
-        configureScope(static function (Scope $scope) use ($requestTag, $leakTag): void {
-            $scope->setTag('request', $requestTag);
+        SentrySdk::getIsolationScope()->setTag('request', $requestTag);
 
-            if ($leakTag !== null) {
-                $scope->setTag('leak', $leakTag);
-            }
-        });
+        if ($leakTag !== null) {
+            SentrySdk::getIsolationScope()->setTag('leak', $leakTag);
+        }
 
         $event = Event::createEvent();
-        configureScope(static function (Scope $scope) use (&$event): void {
-            $event = $scope->applyToEvent($event);
-        });
+        $event = SentrySdk::getGlobalScope()->merge(SentrySdk::getIsolationScope())->applyToEvent($event);
 
         $tags = [];
 
diff --git a/tests/FunctionsTest.php b/tests/FunctionsTest.php
index 4611e60547..34e77e592f 100644
--- a/tests/FunctionsTest.php
+++ b/tests/FunctionsTest.php
@@ -19,8 +19,8 @@
 use Sentry\Options;
 use Sentry\SentrySdk;
 use Sentry\Severity;
-use Sentry\State\Hub;
-use Sentry\State\HubInterface;
+use Sentry\State\GlobalScope;
+use Sentry\State\IsolationScope;
 use Sentry\State\Scope;
 use Sentry\Tracing\PropagationContext;
 use Sentry\Tracing\Span;
@@ -34,6 +34,7 @@
 use Sentry\Util\SentryUid;
 
 use function Sentry\addBreadcrumb;
+use function Sentry\addFeatureFlag;
 use function Sentry\captureCheckIn;
 use function Sentry\captureEvent;
 use function Sentry\captureException;
@@ -50,6 +51,7 @@
 use function Sentry\startTransaction;
 use function Sentry\trace;
 use function Sentry\withContext;
+use function Sentry\withIsolationScope;
 use function Sentry\withMonitor;
 use function Sentry\withScope;
 
@@ -59,7 +61,26 @@ public function testInit(): void
     {
         init(['default_integrations' => false]);
 
-        $this->assertNotNull(SentrySdk::getCurrentHub()->getClient());
+        $client = SentrySdk::getClient();
+
+        $this->assertNotInstanceOf(NoOpClient::class, $client);
+        $this->assertSame($client, SentrySdk::getGlobalScope()->getClient());
+    }
+
+    public function testInitPreservesGlobalScope(): void
+    {
+        $globalScope = SentrySdk::getGlobalScope();
+        $globalScope->setTag('baseline', 'yes');
+
+        init(['default_integrations' => false]);
+
+        $this->assertSame($globalScope, SentrySdk::getGlobalScope());
+        $this->assertSame(SentrySdk::getClient(), $globalScope->getClient());
+
+        $event = $globalScope->merge(new IsolationScope())->applyToEvent(Event::createEvent());
+
+        $this->assertNotNull($event);
+        $this->assertSame(['baseline' => 'yes'], $event->getTags());
     }
 
     /**
@@ -68,16 +89,20 @@ public function testInit(): void
     public function testCaptureMessage(array $functionCallArgs, array $expectedFunctionCallArgs): void
     {
         $eventId = EventId::generate();
+        $message = $expectedFunctionCallArgs[0];
+        $level = $expectedFunctionCallArgs[1];
+        $hint = $expectedFunctionCallArgs[2];
+
+        $client = $this->createMock(ClientInterface::class);
+        $scope = $this->setClientAndIsolationScope($client);
 
-        $hub = $this->createMock(HubInterface::class);
-        $hub->expects($this->once())
+        $client->expects($this->once())
             ->method('captureMessage')
-            ->with(...$expectedFunctionCallArgs)
+            ->with($message, $level, $this->captureScopeConstraint($scope), $hint)
             ->willReturn($eventId);
 
-        SentrySdk::setCurrentHub($hub);
-
         $this->assertSame($eventId, captureMessage(...$functionCallArgs));
+        $this->assertSame($eventId, SentrySdk::getLastEventId());
     }
 
     public static function captureMessageDataProvider(): \Generator
@@ -115,15 +140,16 @@ public function testCaptureException(array $functionCallArgs, array $expectedFun
     {
         $eventId = EventId::generate();
 
-        $hub = $this->createMock(HubInterface::class);
-        $hub->expects($this->once())
+        $client = $this->createMock(ClientInterface::class);
+        $scope = $this->setClientAndIsolationScope($client);
+
+        $client->expects($this->once())
             ->method('captureException')
-            ->with(...$expectedFunctionCallArgs)
+            ->with($expectedFunctionCallArgs[0], $this->captureScopeConstraint($scope), $expectedFunctionCallArgs[1])
             ->willReturn($eventId);
 
-        SentrySdk::setCurrentHub($hub);
-
         $this->assertSame($eventId, captureException(...$functionCallArgs));
+        $this->assertSame($eventId, SentrySdk::getLastEventId());
     }
 
     public static function captureExceptionDataProvider(): \Generator
@@ -155,15 +181,16 @@ public function testCaptureEvent(): void
         $event = Event::createEvent();
         $hint = new EventHint();
 
-        $hub = $this->createMock(HubInterface::class);
-        $hub->expects($this->once())
+        $client = $this->createMock(ClientInterface::class);
+        $scope = $this->setClientAndIsolationScope($client);
+
+        $client->expects($this->once())
             ->method('captureEvent')
-            ->with($event, $hint)
+            ->with($event, $hint, $this->captureScopeConstraint($scope))
             ->willReturn($event->getId());
 
-        SentrySdk::setCurrentHub($hub);
-
         $this->assertSame($event->getId(), captureEvent($event, $hint));
+        $this->assertSame($event->getId(), SentrySdk::getLastEventId());
     }
 
     /**
@@ -173,17 +200,18 @@ public function testCaptureLastError(array $functionCallArgs, array $expectedFun
     {
         $eventId = EventId::generate();
 
-        $hub = $this->createMock(HubInterface::class);
-        $hub->expects($this->once())
+        $client = $this->createMock(ClientInterface::class);
+        $scope = $this->setClientAndIsolationScope($client);
+
+        $client->expects($this->once())
             ->method('captureLastError')
-            ->with(...$expectedFunctionCallArgs)
+            ->with($this->captureScopeConstraint($scope), $expectedFunctionCallArgs[0])
             ->willReturn($eventId);
 
-        SentrySdk::setCurrentHub($hub);
-
         @trigger_error('foo', \E_USER_NOTICE);
 
         $this->assertSame($eventId, captureLastError(...$functionCallArgs));
+        $this->assertSame($eventId, SentrySdk::getLastEventId());
     }
 
     public static function captureLastErrorDataProvider(): \Generator
@@ -199,9 +227,92 @@ public static function captureLastErrorDataProvider(): \Generator
         ];
     }
 
+    public function testCaptureMessageClearsLastEventIdWhenClientReturnsNull(): void
+    {
+        $client = $this->createMock(ClientInterface::class);
+        $scope = $this->setClientAndIsolationScope($client);
+        SentrySdk::getCurrentRuntimeContext()->setLastEventId(EventId::generate());
+
+        $client->expects($this->once())
+            ->method('captureMessage')
+            ->with('foo', null, $this->captureScopeConstraint($scope), null)
+            ->willReturn(null);
+
+        $this->assertNull(captureMessage('foo'));
+        $this->assertNull(SentrySdk::getLastEventId());
+    }
+
+    public function testCaptureExceptionClearsLastEventIdWhenClientReturnsNull(): void
+    {
+        $exception = new \RuntimeException('foo');
+        $client = $this->createMock(ClientInterface::class);
+        $scope = $this->setClientAndIsolationScope($client);
+        SentrySdk::getCurrentRuntimeContext()->setLastEventId(EventId::generate());
+
+        $client->expects($this->once())
+            ->method('captureException')
+            ->with($exception, $this->captureScopeConstraint($scope), null)
+            ->willReturn(null);
+
+        $this->assertNull(captureException($exception));
+        $this->assertNull(SentrySdk::getLastEventId());
+    }
+
+    public function testCaptureEventClearsLastEventIdWhenClientReturnsNull(): void
+    {
+        $event = Event::createEvent();
+        $client = $this->createMock(ClientInterface::class);
+        $scope = $this->setClientAndIsolationScope($client);
+        SentrySdk::getCurrentRuntimeContext()->setLastEventId(EventId::generate());
+
+        $client->expects($this->once())
+            ->method('captureEvent')
+            ->with($event, null, $this->captureScopeConstraint($scope))
+            ->willReturn(null);
+
+        $this->assertNull(captureEvent($event));
+        $this->assertNull(SentrySdk::getLastEventId());
+    }
+
+    public function testCaptureLastErrorClearsLastEventIdWhenClientReturnsNull(): void
+    {
+        $client = $this->createMock(ClientInterface::class);
+        $scope = $this->setClientAndIsolationScope($client);
+        SentrySdk::getCurrentRuntimeContext()->setLastEventId(EventId::generate());
+
+        $client->expects($this->once())
+            ->method('captureLastError')
+            ->with($this->captureScopeConstraint($scope), null)
+            ->willReturn(null);
+
+        $this->assertNull(captureLastError());
+        $this->assertNull(SentrySdk::getLastEventId());
+    }
+
+    public function testCaptureExceptionInsideWithIsolationScopeUpdatesLastEventId(): void
+    {
+        $eventId = EventId::generate();
+        $exception = new \RuntimeException('foo');
+        $client = $this->createMock(ClientInterface::class);
+        $this->setClientAndIsolationScope($client);
+
+        $client->expects($this->once())
+            ->method('captureException')
+            ->willReturn($eventId);
+
+        withIsolationScope(static function () use ($exception): void {
+            captureException($exception);
+        });
+
+        // The forked isolation scope is discarded after the callback, but the
+        // captured event ID must remain readable from the runtime context.
+        $this->assertSame($eventId, SentrySdk::getLastEventId());
+    }
+
     public function testCaptureCheckIn(): void
     {
         $checkInId = SentryUid::generate();
+        $eventId = EventId::generate();
         $monitorConfig = new MonitorConfig(
             MonitorSchedule::crontab('*/5 * * * *'),
             5,
@@ -209,13 +320,30 @@ public function testCaptureCheckIn(): void
             'UTC'
         );
 
-        $hub = $this->createMock(HubInterface::class);
-        $hub->expects($this->once())
-            ->method('captureCheckIn')
-            ->with('test-crontab', CheckInStatus::ok(), 10, $monitorConfig, $checkInId)
-            ->willReturn($checkInId);
+        $client = $this->createMock(ClientInterface::class);
+        $scope = $this->setClientAndIsolationScope($client);
 
-        SentrySdk::setCurrentHub($hub);
+        $client->expects($this->once())
+            ->method('getOptions')
+            ->willReturn(new Options([
+                'environment' => Event::DEFAULT_ENVIRONMENT,
+                'release' => '1.0.0',
+            ]));
+        $client->expects($this->once())
+            ->method('captureEvent')
+            ->with($this->callback(static function (Event $event) use ($checkInId, $monitorConfig): bool {
+                $checkIn = $event->getCheckIn();
+
+                return $checkIn !== null
+                    && $checkIn->getId() === $checkInId
+                    && $checkIn->getMonitorSlug() === 'test-crontab'
+                    && $checkIn->getStatus() == CheckInStatus::ok()
+                    && $checkIn->getRelease() === '1.0.0'
+                    && $checkIn->getEnvironment() === Event::DEFAULT_ENVIRONMENT
+                    && $checkIn->getDuration() === 10
+                    && $checkIn->getMonitorConfig() === $monitorConfig;
+            }), null, $this->captureScopeConstraint($scope))
+            ->willReturn($eventId);
 
         $this->assertSame($checkInId, captureCheckIn(
             'test-crontab',
@@ -224,99 +352,184 @@ public function testCaptureCheckIn(): void
             $monitorConfig,
             $checkInId
         ));
+        $this->assertSame($eventId, SentrySdk::getLastEventId());
+    }
+
+    public function testCaptureCheckInReturnsNullForNoOpClient(): void
+    {
+        SentrySdk::init(new NoOpClient());
+
+        $this->assertNull(captureCheckIn('test-crontab', CheckInStatus::ok()));
     }
 
     public function testWithMonitor(): void
     {
-        $hub = $this->createMock(HubInterface::class);
-        $hub->expects($this->exactly(2))
-            ->method('captureCheckIn')
-            ->with(
-                $this->callback(static function (string $slug): bool {
-                    return $slug === 'test-crontab';
-                }),
-                $this->callback(static function (CheckInStatus $checkInStatus): bool {
-                    // just check for type CheckInStatus
-                    return true;
-                }),
-                $this->anything(),
-                $this->callback(static function (MonitorConfig $monitorConfig): bool {
-                    return $monitorConfig->getSchedule()->getValue() === '*/5 * * * *'
-                        && $monitorConfig->getSchedule()->getType() === MonitorSchedule::TYPE_CRONTAB
-                        && $monitorConfig->getCheckinMargin() === 5
-                        && $monitorConfig->getMaxRuntime() === 30
-                        && $monitorConfig->getTimezone() === 'UTC';
-                })
-            );
-
-        SentrySdk::setCurrentHub($hub);
-
-        withMonitor('test-crontab', static function () {
-            // Do something...
-        }, new MonitorConfig(
+        $events = [];
+        $monitorConfig = new MonitorConfig(
             new MonitorSchedule(MonitorSchedule::TYPE_CRONTAB, '*/5 * * * *'),
             5,
             30,
             'UTC'
-        ));
+        );
+
+        $client = $this->createMock(ClientInterface::class);
+        $scope = $this->setClientAndIsolationScope($client);
+
+        $client->expects($this->exactly(2))
+            ->method('getOptions')
+            ->willReturn(new Options());
+        $client->expects($this->exactly(2))
+            ->method('captureEvent')
+            ->with($this->callback(static function (Event $event): bool {
+                $checkIn = $event->getCheckIn();
+
+                return $checkIn !== null
+                    && $checkIn->getMonitorSlug() === 'test-crontab'
+                    && $checkIn->getMonitorConfig() !== null
+                    && $checkIn->getMonitorConfig()->getSchedule()->getValue() === '*/5 * * * *';
+            }), null, $this->captureScopeConstraint($scope))
+            ->willReturnCallback(static function (Event $event, ?EventHint $hint = null, ?IsolationScope $scope = null) use (&$events): EventId {
+                $events[] = $event;
+
+                return EventId::generate();
+            });
+
+        $result = withMonitor('test-crontab', static function (): string {
+            // Do something...
+            return 'done';
+        }, $monitorConfig);
+
+        $this->assertSame('done', $result);
+        $this->assertCount(2, $events);
+        $this->assertSame(CheckInStatus::inProgress(), $events[0]->getCheckIn()->getStatus());
+        $this->assertSame(CheckInStatus::ok(), $events[1]->getCheckIn()->getStatus());
+        $this->assertSame($events[0]->getCheckIn()->getId(), $events[1]->getCheckIn()->getId());
     }
 
     public function testWithMonitorCallableThrows(): void
     {
-        $this->expectException(\Exception::class);
-
-        $hub = $this->createMock(HubInterface::class);
-        $hub->expects($this->exactly(2))
-            ->method('captureCheckIn')
-            ->with(
-                $this->callback(static function (string $slug): bool {
-                    return $slug === 'test-crontab';
-                }),
-                $this->callback(static function (CheckInStatus $checkInStatus): bool {
-                    // just check for type CheckInStatus
-                    return true;
-                }),
-                $this->anything(),
-                $this->callback(static function (MonitorConfig $monitorConfig): bool {
-                    return $monitorConfig->getSchedule()->getValue() === '*/5 * * * *'
-                        && $monitorConfig->getSchedule()->getType() === MonitorSchedule::TYPE_CRONTAB
-                        && $monitorConfig->getCheckinMargin() === 5
-                        && $monitorConfig->getMaxRuntime() === 30
-                        && $monitorConfig->getTimezone() === 'UTC';
-                })
-            );
-
-        SentrySdk::setCurrentHub($hub);
-
-        withMonitor('test-crontab', static function () {
-            throw new \Exception();
-        }, new MonitorConfig(
-            new MonitorSchedule(MonitorSchedule::TYPE_CRONTAB, '*/5 * * * *'),
-            5,
-            30,
-            'UTC'
-        ));
+        $events = [];
+
+        $client = $this->createMock(ClientInterface::class);
+        $scope = $this->setClientAndIsolationScope($client);
+
+        $client->expects($this->exactly(2))
+            ->method('getOptions')
+            ->willReturn(new Options());
+        $client->expects($this->exactly(2))
+            ->method('captureEvent')
+            ->with($this->isInstanceOf(Event::class), null, $this->captureScopeConstraint($scope))
+            ->willReturnCallback(static function (Event $event, ?EventHint $hint = null, ?IsolationScope $scope = null) use (&$events): EventId {
+                $events[] = $event;
+
+                return EventId::generate();
+            });
+
+        try {
+            withMonitor('test-crontab', static function (): void {
+                throw new \Exception('monitor failed');
+            }, new MonitorConfig(
+                new MonitorSchedule(MonitorSchedule::TYPE_CRONTAB, '*/5 * * * *'),
+                5,
+                30,
+                'UTC'
+            ));
+
+            $this->fail('The callback exception should be rethrown.');
+        } catch (\Exception $exception) {
+            $this->assertSame('monitor failed', $exception->getMessage());
+        }
+
+        $this->assertCount(2, $events);
+        $this->assertSame(CheckInStatus::inProgress(), $events[0]->getCheckIn()->getStatus());
+        $this->assertSame(CheckInStatus::error(), $events[1]->getCheckIn()->getStatus());
+        $this->assertSame($events[0]->getCheckIn()->getId(), $events[1]->getCheckIn()->getId());
     }
 
     public function testAddBreadcrumb(): void
     {
         $breadcrumb = new Breadcrumb(Breadcrumb::LEVEL_ERROR, Breadcrumb::TYPE_ERROR, 'error_reporting');
+        $otherScope = new IsolationScope();
 
         /** @var ClientInterface&MockObject $client */
         $client = $this->createMock(ClientInterface::class);
+        $scope = $this->setClientAndIsolationScope($client);
+
         $client->expects($this->once())
             ->method('getOptions')
             ->willReturn(new Options(['default_integrations' => false]));
 
-        SentrySdk::getCurrentHub()->bindClient($client);
+        addBreadcrumb($breadcrumb);
+
+        $this->assertScopeBreadcrumbs($scope, [$breadcrumb]);
+        $this->assertScopeBreadcrumbs($otherScope, []);
+    }
+
+    public function testAddBreadcrumbDoesNothingIfMaxBreadcrumbsLimitIsZero(): void
+    {
+        $breadcrumb = new Breadcrumb(Breadcrumb::LEVEL_ERROR, Breadcrumb::TYPE_ERROR, 'error_reporting');
+
+        $client = $this->createMock(ClientInterface::class);
+        $scope = $this->setClientAndIsolationScope($client);
+
+        $client->expects($this->once())
+            ->method('getOptions')
+            ->willReturn(new Options(['max_breadcrumbs' => 0]));
 
         addBreadcrumb($breadcrumb);
-        configureScope(function (Scope $scope) use ($breadcrumb): void {
-            $event = $scope->applyToEvent(Event::createEvent());
 
-            $this->assertNotNull($event);
-            $this->assertSame([$breadcrumb], $event->getBreadcrumbs());
-        });
+        $this->assertScopeBreadcrumbs($scope, []);
+    }
+
+    public function testAddBreadcrumbDoesNothingForNoOpClient(): void
+    {
+        SentrySdk::init(new NoOpClient());
+        $scope = SentrySdk::getIsolationScope();
+
+        addBreadcrumb(new Breadcrumb(Breadcrumb::LEVEL_ERROR, Breadcrumb::TYPE_ERROR, 'error_reporting'));
+
+        $this->assertScopeBreadcrumbs($scope, []);
+    }
+
+    public function testAddBreadcrumbDoesNothingWhenBeforeBreadcrumbCallbackReturnsNull(): void
+    {
+        $breadcrumb = new Breadcrumb(Breadcrumb::LEVEL_ERROR, Breadcrumb::TYPE_ERROR, 'error_reporting');
+
+        $client = $this->createMock(ClientInterface::class);
+        $scope = $this->setClientAndIsolationScope($client);
+
+        $client->expects($this->once())
+            ->method('getOptions')
+            ->willReturn(new Options([
+                'before_breadcrumb' => static function () {
+                    return null;
+                },
+            ]));
+
+        addBreadcrumb($breadcrumb);
+
+        $this->assertScopeBreadcrumbs($scope, []);
+    }
+
+    public function testAddBreadcrumbStoresBreadcrumbReturnedByBeforeBreadcrumbCallback(): void
+    {
+        $breadcrumb1 = new Breadcrumb(Breadcrumb::LEVEL_ERROR, Breadcrumb::TYPE_ERROR, 'error_reporting');
+        $breadcrumb2 = new Breadcrumb(Breadcrumb::LEVEL_WARNING, Breadcrumb::TYPE_DEFAULT, 'custom');
+
+        $client = $this->createMock(ClientInterface::class);
+        $scope = $this->setClientAndIsolationScope($client);
+
+        $client->expects($this->once())
+            ->method('getOptions')
+            ->willReturn(new Options([
+                'before_breadcrumb' => static function () use ($breadcrumb2): Breadcrumb {
+                    return $breadcrumb2;
+                },
+            ]));
+
+        addBreadcrumb($breadcrumb1);
+
+        $this->assertScopeBreadcrumbs($scope, [$breadcrumb2]);
     }
 
     public function testWithScope(): void
@@ -328,83 +541,123 @@ public function testWithScope(): void
         $this->assertSame('foobarbaz', $returnValue);
     }
 
-    public function testConfigureScope(): void
+    public function testConfigureScopeMutatesCurrentIsolationScopeOnly(): void
     {
-        $callbackInvoked = false;
+        $globalScope = SentrySdk::getGlobalScope();
+        $globalScope->setTag('scope', 'global');
+
+        $isolationScope = new IsolationScope();
+        SentrySdk::getCurrentRuntimeContext()->setIsolationScope($isolationScope);
 
-        configureScope(static function () use (&$callbackInvoked): void {
-            $callbackInvoked = true;
+        $callbackScope = null;
+
+        configureScope(static function (IsolationScope $scope) use (&$callbackScope): void {
+            $callbackScope = $scope;
+            $scope->setTag('scope', 'isolation');
         });
 
-        $this->assertTrue($callbackInvoked);
+        $this->assertSame($isolationScope, $callbackScope);
+
+        $isolationEvent = (new GlobalScope())->merge($isolationScope)->applyToEvent(Event::createEvent());
+        $this->assertNotNull($isolationEvent);
+        $this->assertSame(['scope' => 'isolation'], $isolationEvent->getTags());
+
+        $globalEvent = $globalScope->merge(new IsolationScope())->applyToEvent(Event::createEvent());
+        $this->assertNotNull($globalEvent);
+        $this->assertSame(['scope' => 'global'], $globalEvent->getTags());
+    }
+
+    public function testAddFeatureFlagMutatesCurrentIsolationScopeOnly(): void
+    {
+        $globalScope = SentrySdk::getGlobalScope();
+
+        $isolationScope = new IsolationScope();
+        SentrySdk::getCurrentRuntimeContext()->setIsolationScope($isolationScope);
+
+        addFeatureFlag('isolation-only', false);
+
+        $isolationEvent = (new GlobalScope())->merge($isolationScope)->applyToEvent(Event::createEvent());
+        $this->assertNotNull($isolationEvent);
+        $this->assertSame([
+            'values' => [
+                [
+                    'flag' => 'isolation-only',
+                    'result' => false,
+                ],
+            ],
+        ], $isolationEvent->getContexts()['flags']);
+
+        $globalEvent = $globalScope->merge(new IsolationScope())->applyToEvent(Event::createEvent());
+        $this->assertNotNull($globalEvent);
+        $this->assertArrayNotHasKey('flags', $globalEvent->getContexts());
     }
 
     public function testStartAndEndContext(): void
     {
         SentrySdk::init();
 
-        $globalHub = SentrySdk::getCurrentHub();
+        $globalScope = SentrySdk::getIsolationScope();
 
         startContext();
 
-        $requestHub = SentrySdk::getCurrentHub();
+        $requestScope = SentrySdk::getIsolationScope();
 
-        $this->assertNotSame($globalHub, $requestHub);
+        $this->assertNotSame($globalScope, $requestScope);
 
         endContext();
 
-        $this->assertSame($globalHub, SentrySdk::getCurrentHub());
+        $this->assertSame($globalScope, SentrySdk::getIsolationScope());
     }
 
     public function testWithContext(): void
     {
         SentrySdk::init();
 
-        $globalHub = SentrySdk::getCurrentHub();
+        $globalScope = SentrySdk::getIsolationScope();
 
-        $result = withContext(function () use ($globalHub): string {
-            $this->assertNotSame($globalHub, SentrySdk::getCurrentHub());
+        $result = withContext(function () use ($globalScope): string {
+            $this->assertNotSame($globalScope, SentrySdk::getIsolationScope());
 
             return 'ok';
         });
 
         $this->assertSame('ok', $result);
-        $this->assertSame($globalHub, SentrySdk::getCurrentHub());
+        $this->assertSame($globalScope, SentrySdk::getIsolationScope());
     }
 
     public function testNestedWithContextReusesOuterContext(): void
     {
         SentrySdk::init();
 
-        $globalHub = SentrySdk::getCurrentHub();
-        $outerHub = null;
-        $innerHub = null;
+        $globalScope = SentrySdk::getIsolationScope();
+        $outerScope = null;
+        $innerScope = null;
 
-        withContext(function () use (&$outerHub, &$innerHub, $globalHub): void {
-            $outerHub = SentrySdk::getCurrentHub();
+        withContext(function () use (&$outerScope, &$innerScope, $globalScope): void {
+            $outerScope = SentrySdk::getIsolationScope();
 
-            configureScope(static function (Scope $scope): void {
+            configureScope(static function (IsolationScope $scope): void {
                 $scope->setTag('outer', 'yes');
             });
 
-            withContext(static function () use (&$innerHub): void {
-                $innerHub = SentrySdk::getCurrentHub();
+            withContext(static function () use (&$innerScope): void {
+                $innerScope = SentrySdk::getIsolationScope();
             });
 
             $event = Event::createEvent();
 
-            configureScope(static function (Scope $scope) use (&$event): void {
-                $event = $scope->applyToEvent($event);
+            configureScope(static function (IsolationScope $scope) use (&$event): void {
+                $event = SentrySdk::getGlobalScope()->merge($scope)->applyToEvent($event);
             });
 
-            $this->assertNotSame($globalHub, SentrySdk::getCurrentHub());
+            $this->assertNotSame($globalScope, SentrySdk::getIsolationScope());
             $this->assertSame('yes', $event->getTags()['outer'] ?? null);
         });
 
-        $this->assertNotNull($outerHub);
-        $this->assertNotNull($innerHub);
-        $this->assertSame($outerHub, $innerHub);
-        $this->assertSame($globalHub, SentrySdk::getCurrentHub());
+        $this->assertNotNull($outerScope);
+        $this->assertNotNull($innerScope);
+        $this->assertSame($outerScope, $innerScope);
+        $this->assertSame($globalScope, SentrySdk::getIsolationScope());
     }
 
     public function testWithContextAlwaysEndsContextWithOptionalTimeout(): void
@@ -419,7 +672,7 @@ public function testWithContextAlwaysEndsContextWithOptionalTimeout(): void
             ->with(13)
             ->willReturn(new Result(ResultStatus::success()));
 
-        SentrySdk::init()->bindClient($client);
+        SentrySdk::init($client);
 
         try {
             withContext(static function (): void {
@@ -438,15 +691,16 @@ public function testStartTransaction(): void
         $transaction = new Transaction($transactionContext);
         $customSamplingContext = ['foo' => 'bar'];
 
-        $hub = $this->createMock(HubInterface::class);
-        $hub->expects($this->once())
-            ->method('startTransaction')
-            ->with($transactionContext, $customSamplingContext)
-            ->willReturn($transaction);
+        $client = $this->createMock(ClientInterface::class);
+        $client->expects($this->once())
+            ->method('getOptions')
+            ->willReturn(new Options());
+
+        SentrySdk::getGlobalScope()->setClient($client);
 
-        SentrySdk::setCurrentHub($hub);
+        $transaction = startTransaction($transactionContext, $customSamplingContext);
 
-        $this->assertSame($transaction, startTransaction($transactionContext, $customSamplingContext));
+        $this->assertSame('foo', $transaction->getName());
     }
 
     public function testTraceReturnsClosureResult(): void
@@ -462,54 +716,60 @@ public function testTraceReturnsClosureResult(): void
 
     public function testTraceCorrectlyReplacesAndRestoresCurrentSpan(): void
     {
-        $hub = new Hub(new NoOpClient());
-
         $transaction = new Transaction(TransactionContext::make());
         $transaction->setSampled(true);
+        $outerScope = SentrySdk::getIsolationScope();
+        $outerScope->setSpan($transaction);
 
-        $hub->setSpan($transaction);
+        $this->assertSame($transaction, SentrySdk::getIsolationScope()->getSpan());
 
-        SentrySdk::setCurrentHub($hub);
+        $childSpan = null;
 
-        $this->assertSame($transaction, $hub->getSpan());
+        trace(function (IsolationScope $scope) use ($outerScope, $transaction, &$childSpan): void {
+            $childSpan = $scope->getSpan();
 
-        trace(function () use ($transaction, $hub) {
-            $this->assertNotSame($transaction, $hub->getSpan());
+            $this->assertNotSame($outerScope, $scope);
+            $this->assertNotSame($transaction, $childSpan);
+            $this->assertSame($childSpan, SentrySdk::getIsolationScope()->getSpan());
+            $this->assertNull($childSpan->getEndTimestamp());
         }, new SpanContext());
 
-        $this->assertSame($transaction, $hub->getSpan());
+        $this->assertNotNull($childSpan);
+        $this->assertNotNull($childSpan->getEndTimestamp());
+        $this->assertSame($outerScope, SentrySdk::getIsolationScope());
+        $this->assertSame($transaction, SentrySdk::getIsolationScope()->getSpan());
 
         try {
-            trace(static function () {
+            trace(function (IsolationScope $scope) use ($transaction): void {
+                $this->assertNotSame($transaction, $scope->getSpan());
+
                 throw new \RuntimeException('Throwing should still restore the previous span');
             }, new SpanContext());
         } catch (\RuntimeException $e) {
-            $this->assertSame($transaction, $hub->getSpan());
+            $this->assertSame($outerScope, SentrySdk::getIsolationScope());
+            $this->assertSame($transaction, SentrySdk::getIsolationScope()->getSpan());
         }
     }
 
     public function testTraceDoesntCreateSpanIfTransactionIsNotSampled(): void
     {
-        $scope = $this->createMock(Scope::class);
-
-        $hub = new Hub(new NoOpClient(), $scope);
-
         $transaction = new Transaction(TransactionContext::make());
         $transaction->setSampled(false);
 
-        $scope->expects($this->never())
-              ->method('setSpan');
-        $scope->expects($this->exactly(3))
-              ->method('getSpan')
-              ->willReturn($transaction);
+        $outerScope = SentrySdk::getIsolationScope();
+        $outerScope->setSpan($transaction);
+        $callbackScope = null;
 
-        SentrySdk::setCurrentHub($hub);
+        trace(function (IsolationScope $scope) use ($transaction, &$callbackScope): void {
+            $callbackScope = $scope;
 
-        trace(function () use ($transaction, $hub) {
-            $this->assertSame($transaction, $hub->getSpan());
+            $this->assertSame($transaction, $scope->getSpan());
+            $this->assertSame($transaction, SentrySdk::getIsolationScope()->getSpan());
         }, SpanContext::make());
 
-        $this->assertSame($transaction, $hub->getSpan());
+        $this->assertNotSame($outerScope, $callbackScope);
+        $this->assertSame($outerScope, SentrySdk::getIsolationScope());
+        $this->assertSame($transaction, SentrySdk::getIsolationScope()->getSpan());
     }
 
     public function testTraceparentWithTracingDisabled(): void
@@ -518,11 +778,7 @@ public function testTraceparentWithTracingDisabled(): void
         $propagationContext->setTraceId(new TraceId('566e3688a61d4bc888951642d6f14a19'));
         $propagationContext->setSpanId(new SpanId('566e3688a61d4bc8'));
 
-        $scope = new Scope($propagationContext);
-
-        $hub = new Hub(new NoOpClient(), $scope);
-
-        SentrySdk::setCurrentHub($hub);
+        SentrySdk::getCurrentRuntimeContext()->setIsolationScope(new IsolationScope($propagationContext));
 
         $traceParent = getTraceparent();
 
@@ -538,9 +794,7 @@ public function testTraceparentWithTracingEnabled(): void
                 'traces_sample_rate' => 1.0,
             ]));
 
-        $hub = new Hub($client);
-
-        SentrySdk::setCurrentHub($hub);
+        SentrySdk::getGlobalScope()->setClient($client);
 
         $spanContext = (new SpanContext())
             ->setTraceId(new TraceId('566e3688a61d4bc888951642d6f14a19'))
@@ -548,7 +802,7 @@ public function testTraceparentWithTracingEnabled(): void
 
         $span = new Span($spanContext);
 
-        $hub->setSpan($span);
+        SentrySdk::getIsolationScope()->setSpan($span);
 
         $traceParent = getTraceparent();
 
@@ -568,7 +822,7 @@ public function testTraceHeadersAreEmptyWhenExternalPropagationContextIsActive()
             ];
         });
 
-        SentrySdk::setCurrentHub(new Hub(new NoOpClient(), new Scope($propagationContext)));
+        SentrySdk::getCurrentRuntimeContext()->setIsolationScope(new IsolationScope($propagationContext));
 
         $this->assertSame('', getTraceparent());
         $this->assertSame('', getBaggage());
@@ -582,8 +836,6 @@ public function testBaggageWithTracingDisabled(): void
         $propagationContext->setTraceId(new TraceId('566e3688a61d4bc888951642d6f14a19'));
         $propagationContext->setSampleRand(0.25);
 
-        $scope = new Scope($propagationContext);
-
         $client = $this->createMock(ClientInterface::class);
         $client->expects($this->atLeastOnce())
             ->method('getOptions')
@@ -592,13 +844,13 @@ public function testBaggageWithTracingDisabled(): void
                 'environment' => 'development',
             ]));
 
-        $hub = new Hub($client, $scope);
-
-        SentrySdk::setCurrentHub($hub);
+        SentrySdk::getGlobalScope()->setClient($client);
+        SentrySdk::getCurrentRuntimeContext()->setIsolationScope(new IsolationScope($propagationContext));
 
         $baggage = getBaggage();
 
         $this->assertSame('sentry-trace_id=566e3688a61d4bc888951642d6f14a19,sentry-sample_rand=0.25,sentry-release=1.0.0,sentry-environment=development', $baggage);
+        $this->assertNotNull($propagationContext->getDynamicSamplingContext());
     }
 
     public function testBaggageWithTracingEnabled(): void
@@ -612,9 +864,7 @@ public function testBaggageWithTracingEnabled(): void
                 'environment' => 'development',
             ]));
 
-        $hub = new Hub($client);
-
-        SentrySdk::setCurrentHub($hub);
+        SentrySdk::getGlobalScope()->setClient($client);
 
         $transactionContext = new TransactionContext();
         $transactionContext->setName('Test');
@@ -627,7 +877,7 @@ public function testBaggageWithTracingEnabled(): void
 
         $span = $transaction->startChild($spanContext);
 
-        $hub->setSpan($span);
+        SentrySdk::getIsolationScope()->setSpan($span);
 
         $baggage = getBaggage();
 
@@ -647,7 +897,7 @@ public function testGetOtlpTracesEndpointUrlFallsBackToDsn(): void
                 'dsn' => 'https://public@example.com/1',
             ]));
 
-        SentrySdk::setCurrentHub(new Hub($client));
+        SentrySdk::getGlobalScope()->setClient($client);
 
         $this->assertSame('https://example.com/api/1/integration/otlp/v1/traces/', getOtlpTracesEndpointUrl());
     }
@@ -666,16 +916,17 @@ public function testGetOtlpTracesEndpointUrlPrefersCollectorUrl(): void
                 'dsn' => 'https://public@example.com/1',
             ]));
 
-        SentrySdk::setCurrentHub(new Hub($client));
+        SentrySdk::getGlobalScope()->setClient($client);
 
         $this->assertSame('http://collector:4318/v1/traces', getOtlpTracesEndpointUrl());
     }
 
     public function testContinueTrace(): void
     {
-        $hub = new Hub(new NoOpClient());
+        SentrySdk::getGlobalScope()->setClient(new NoOpClient());
 
-        SentrySdk::setCurrentHub($hub);
+        $scope = new IsolationScope();
+        SentrySdk::getCurrentRuntimeContext()->setIsolationScope($scope);
 
         $transactionContext = continueTrace(
             '566e3688a61d4bc888951642d6f14a19-566e3688a61d4bc8-1',
@@ -686,17 +937,15 @@ public function testContinueTrace(): void
         $this->assertSame('566e3688a61d4bc8', (string) $transactionContext->getParentSpanId());
         $this->assertTrue($transactionContext->getParentSampled());
 
-        configureScope(function (Scope $scope): void {
-            $propagationContext = $scope->getPropagationContext();
+        $propagationContext = $scope->getPropagationContext();
 
-            $this->assertSame('566e3688a61d4bc888951642d6f14a19', (string) $propagationContext->getTraceId());
-            $this->assertSame('566e3688a61d4bc8', (string) $propagationContext->getParentSpanId());
+        $this->assertSame('566e3688a61d4bc888951642d6f14a19', (string) $propagationContext->getTraceId());
+        $this->assertSame('566e3688a61d4bc8', (string) $propagationContext->getParentSpanId());
 
-            $dynamicSamplingContext = $propagationContext->getDynamicSamplingContext();
+        $dynamicSamplingContext = $propagationContext->getDynamicSamplingContext();
 
-            $this->assertSame('566e3688a61d4bc888951642d6f14a19', (string) $dynamicSamplingContext->get('trace_id'));
-            $this->assertTrue($dynamicSamplingContext->isFrozen());
-        });
+        $this->assertSame('566e3688a61d4bc888951642d6f14a19', (string) $dynamicSamplingContext->get('trace_id'));
+        $this->assertTrue($dynamicSamplingContext->isFrozen());
     }
 
     public function testContinueTraceWhenOrgMismatch(): void
@@ -709,8 +958,10 @@ public function testContinueTraceWhenOrgMismatch(): void
                 'org_id' => 1,
             ]));
 
-        $hub = new Hub($client);
-        SentrySdk::setCurrentHub($hub);
+        SentrySdk::getGlobalScope()->setClient($client);
+
+        $scope = new IsolationScope();
+        SentrySdk::getCurrentRuntimeContext()->setIsolationScope($scope);
 
         $transactionContext = continueTrace(
             '566e3688a61d4bc888951642d6f14a19-566e3688a61d4bc8-1',
@@ -727,14 +978,12 @@ public function testContinueTraceWhenOrgMismatch(): void
         $this->assertNull($transactionContext->getMetadata()->getDynamicSamplingContext());
         $this->assertNotNull($newSampleRand);
 
-        configureScope(function (Scope $scope) use ($newTraceId, $newSampleRand): void {
-            $propagationContext = $scope->getPropagationContext();
+        $propagationContext = $scope->getPropagationContext();
 
-            $this->assertSame($newTraceId, (string) $propagationContext->getTraceId());
-            $this->assertNull($propagationContext->getParentSpanId());
-            $this->assertNull($propagationContext->getDynamicSamplingContext());
-            $this->assertSame($newSampleRand, $propagationContext->getSampleRand());
-        });
+        $this->assertSame($newTraceId, (string) $propagationContext->getTraceId());
+        $this->assertNull($propagationContext->getParentSpanId());
+        $this->assertNull($propagationContext->getDynamicSamplingContext());
+        $this->assertSame($newSampleRand, $propagationContext->getSampleRand());
     }
 
     public function testContinueTraceWhenOrgMatch(): void
@@ -747,8 +996,10 @@ public function testContinueTraceWhenOrgMatch(): void
                 'org_id' => 1,
             ]));
 
-        $hub = new Hub($client);
-        SentrySdk::setCurrentHub($hub);
+        SentrySdk::getGlobalScope()->setClient($client);
+
+        $scope = new IsolationScope();
+        SentrySdk::getCurrentRuntimeContext()->setIsolationScope($scope);
 
         $transactionContext = continueTrace(
             '566e3688a61d4bc888951642d6f14a19-566e3688a61d4bc8-1',
@@ -759,16 +1010,60 @@ public function testContinueTraceWhenOrgMatch(): void
         $this->assertSame('566e3688a61d4bc8', (string) $transactionContext->getParentSpanId());
         $this->assertTrue($transactionContext->getParentSampled());
 
-        configureScope(function (Scope $scope): void {
-            $propagationContext = $scope->getPropagationContext();
+        $propagationContext = $scope->getPropagationContext();
+
+        $this->assertSame('566e3688a61d4bc888951642d6f14a19', (string) $propagationContext->getTraceId());
+        $this->assertSame('566e3688a61d4bc8', (string) $propagationContext->getParentSpanId());
+
+        $dynamicSamplingContext = $propagationContext->getDynamicSamplingContext();
+
+        $this->assertNotNull($dynamicSamplingContext);
+        $this->assertSame('1', $dynamicSamplingContext->get('org_id'));
+    }
+
+    private function setClientAndIsolationScope(ClientInterface $client): IsolationScope
+    {
+        SentrySdk::init();
 
-            $this->assertSame('566e3688a61d4bc888951642d6f14a19', (string) $propagationContext->getTraceId());
-            $this->assertSame('566e3688a61d4bc8', (string) $propagationContext->getParentSpanId());
+        SentrySdk::getGlobalScope()->clear();
+        SentrySdk::getGlobalScope()->setTag('scope', 'global');
+        SentrySdk::getGlobalScope()->setTag('global', 'yes');
+        SentrySdk::getGlobalScope()->setClient($client);
 
-            $dynamicSamplingContext = $propagationContext->getDynamicSamplingContext();
+        $scope = new IsolationScope();
+        $scope->setTag('scope', 'isolation');
+        $scope->setTag('isolation', 'yes');
+        SentrySdk::getCurrentRuntimeContext()->setIsolationScope($scope);
 
-            $this->assertNotNull($dynamicSamplingContext);
-            $this->assertSame('1', $dynamicSamplingContext->get('org_id'));
+        return $scope;
+    }
+
+    private function captureScopeConstraint(IsolationScope $isolationScope)
+    {
+        return $this->callback(function (IsolationScope $captureScope) use ($isolationScope): bool {
+            $this->assertSame($isolationScope, $captureScope);
+
+            $event = SentrySdk::getGlobalScope()->merge($captureScope)->applyToEvent(Event::createEvent());
+
+            $this->assertNotNull($event);
+            $this->assertSame([
+                'scope' => 'isolation',
+                'global' => 'yes',
+                'isolation' => 'yes',
+            ], $event->getTags());
+
+            return true;
         });
     }
+
+    /**
+     * @param Breadcrumb[] $expectedBreadcrumbs
+     */
+    private function assertScopeBreadcrumbs(IsolationScope $scope, array $expectedBreadcrumbs): void
+    {
+        $event = (new GlobalScope())->merge($scope)->applyToEvent(Event::createEvent());
+
+        $this->assertNotNull($event);
+        $this->assertSame($expectedBreadcrumbs, $event->getBreadcrumbs());
+    }
 }
diff --git a/tests/Integration/EnvironmentIntegrationTest.php b/tests/Integration/EnvironmentIntegrationTest.php
index 788b95fa86..3c7a66fe73 100644
--- a/tests/Integration/EnvironmentIntegrationTest.php
+++ b/tests/Integration/EnvironmentIntegrationTest.php
@@ -12,7 +12,7 @@
 use Sentry\Event;
 use Sentry\Integration\EnvironmentIntegration;
 use Sentry\SentrySdk;
-use Sentry\State\Scope;
+use Sentry\State\IsolationScope;
 use Sentry\Util\PHPVersion;
 
 use function Sentry\withScope;
@@ -33,14 +33,14 @@ public function testInvoke(bool $isIntegrationEnabled, ?RuntimeContext $initialR
             ->method('getIntegration')
             ->willReturn($isIntegrationEnabled ? $integration : null);
 
-        SentrySdk::getCurrentHub()->bindClient($client);
+        SentrySdk::init($client);
 
-        withScope(function (Scope $scope) use ($expectedRuntimeContext, $expectedOsContext, $initialRuntimeContext, $initialOsContext): void {
+        withScope(function (IsolationScope $scope) use ($expectedRuntimeContext, $expectedOsContext, $initialRuntimeContext, $initialOsContext): void {
             $event = Event::createEvent();
             $event->setRuntimeContext($initialRuntimeContext);
             $event->setOsContext($initialOsContext);
 
-            $event = $scope->applyToEvent($event);
+            $event = SentrySdk::getGlobalScope()->merge($scope)->applyToEvent($event);
 
             $this->assertNotNull($event);
 
diff --git a/tests/Integration/FrameContextifierIntegrationTest.php b/tests/Integration/FrameContextifierIntegrationTest.php
index 5667826b0d..ac49a43883 100644
--- a/tests/Integration/FrameContextifierIntegrationTest.php
+++ b/tests/Integration/FrameContextifierIntegrationTest.php
@@ -14,7 +14,7 @@
 use Sentry\Options;
 use Sentry\SentrySdk;
 use Sentry\Stacktrace;
-use Sentry\State\Scope;
+use Sentry\State\IsolationScope;
 
 use function Sentry\withScope;
 
@@ -40,7 +40,7 @@ public function testInvoke(string $fixtureFilePath, int $lineNumber, int $contex
             ->method('getOptions')
             ->willReturn($options);
 
-        SentrySdk::getCurrentHub()->bindClient($client);
+        SentrySdk::init($client);
 
         $stacktrace = new Stacktrace([
             new Frame('[unknown]', $fixtureFilePath, $lineNumber, null, $fixtureFilePath),
@@ -49,8 +49,8 @@ public function testInvoke(string $fixtureFilePath, int $lineNumber, int $contex
         $event = Event::createEvent();
         $event->setStacktrace($stacktrace);
 
-        withScope(static function (Scope $scope) use (&$event): void {
-            $event = $scope->applyToEvent($event);
+        withScope(static function (IsolationScope $scope) use (&$event): void {
+            $event = SentrySdk::getGlobalScope()->merge($scope)->applyToEvent($event);
         });
 
         $this->assertNotNull($event);
@@ -133,7 +133,7 @@ public function testInvokeLogsWarningMessageIfSourceCodeExcerptCannotBeRetrieved
             ->method('getOptions')
             ->willReturn($options);
 
-        SentrySdk::getCurrentHub()->bindClient($client);
+        SentrySdk::init($client);
 
         $stacktrace = new Stacktrace([
             new Frame(null, '[internal]', 0),
@@ -143,8 +143,8 @@ public function testInvokeLogsWarningMessageIfSourceCodeExcerptCannotBeRetrieved
         $event = Event::createEvent();
         $event->setStacktrace($stacktrace);
 
-        withScope(static function (Scope $scope) use (&$event): void {
-            $event = $scope->applyToEvent($event);
+        withScope(static function (IsolationScope $scope) use (&$event): void {
+            $event = SentrySdk::getGlobalScope()->merge($scope)->applyToEvent($event);
         });
 
         $this->assertNotNull($event);
diff --git a/tests/Integration/ModulesIntegrationTest.php b/tests/Integration/ModulesIntegrationTest.php
index 52b96c9d36..33abcc5022 100644
--- a/tests/Integration/ModulesIntegrationTest.php
+++ b/tests/Integration/ModulesIntegrationTest.php
@@ -11,7 +11,7 @@
 use Sentry\Event;
 use Sentry\Integration\ModulesIntegration;
 use Sentry\SentrySdk;
-use Sentry\State\Scope;
+use Sentry\State\IsolationScope;
 use Sentry\Transport\Result;
 use Sentry\Transport\ResultStatus;
 use Sentry\Transport\TransportInterface;
@@ -34,10 +34,10 @@ public function testInvoke(bool $isIntegrationEnabled, bool $expectedEmptyModule
             ->method('getIntegration')
             ->willReturn($isIntegrationEnabled ? $integration : null);
 
-        SentrySdk::getCurrentHub()->bindClient($client);
+        SentrySdk::init($client);
 
-        withScope(function (Scope $scope) use ($expectedEmptyModules): void {
-            $event = $scope->applyToEvent(Event::createEvent());
+        withScope(function (IsolationScope $scope) use ($expectedEmptyModules): void {
+            $event = SentrySdk::getGlobalScope()->merge($scope)->applyToEvent(Event::createEvent());
 
             $this->assertNotNull($event);
 
@@ -86,9 +86,9 @@ public function testModuleIntegration(): void
                                ->setTransport($transport)
                                ->getClient();
 
-        SentrySdk::getCurrentHub()->bindClient($client);
+        SentrySdk::init($client);
 
-        $client->captureEvent(Event::createEvent(), null, new Scope());
+        $client->captureEvent(Event::createEvent(), null, new IsolationScope());
     }
 
     /**
diff --git a/tests/Integration/OTLPIntegrationTest.php b/tests/Integration/OTLPIntegrationTest.php
index a0f3e5680f..b8ef7ce13d 100644
--- a/tests/Integration/OTLPIntegrationTest.php
+++ b/tests/Integration/OTLPIntegrationTest.php
@@ -19,7 +19,6 @@
 use Sentry\Integration\OTLPIntegration;
 use Sentry\Options;
 use Sentry\SentrySdk;
-use Sentry\State\Hub;
 use Sentry\State\Scope;
 use Sentry\Tests\Fixtures\OpenTelemetry\StubOtelHttpClient;
 use Sentry\Tests\Fixtures\OpenTelemetry\TestClientDiscoverer;
@@ -115,7 +114,7 @@ public function testSetupOnceRegistersExternalPropagationContext(): void
             ->willReturn($integration);
 
         try {
-            SentrySdk::setCurrentHub(new Hub($client));
+            SentrySdk::init($client);
 
             $this->assertSame([
                 'trace_id' => '771a43a4192642f0b136d5159a501700',
@@ -146,7 +145,7 @@ public function testExternalPropagationContextIsIgnoredWhenCurrentClientDoesNotH
             ->willReturn(null);
 
         try {
-            SentrySdk::setCurrentHub(new Hub($client));
+            SentrySdk::init($client);
 
             $this->assertNull(Scope::getExternalPropagationContext());
         } finally {
@@ -280,10 +279,10 @@ private function useCapturingHttpClient(): void
 
         if (method_exists(HttpClientDiscovery::class, 'setDiscoverers')) {
             HttpClientDiscovery::setDiscoverers([new TestClientDiscoverer()]);
-        } else {
-            ClassDiscovery::prependStrategy(TestDiscoveryStrategy::class);
         }
 
+        ClassDiscovery::prependStrategy(TestDiscoveryStrategy::class);
+
         StubOtelHttpClient::reset();
     }
 
diff --git a/tests/Integration/RequestIntegrationTest.php b/tests/Integration/RequestIntegrationTest.php
index 66749155a9..7de6c166c6 100644
--- a/tests/Integration/RequestIntegrationTest.php
+++ b/tests/Integration/RequestIntegrationTest.php
@@ -16,7 +16,7 @@
 use Sentry\Integration\RequestIntegration;
 use Sentry\Options;
 use Sentry\SentrySdk;
-use Sentry\State\Scope;
+use Sentry\State\IsolationScope;
 use Sentry\UserDataBag;
 
 use function Sentry\withScope;
@@ -44,10 +44,10 @@ public function testInvoke(array $options, ServerRequestInterface $request, arra
             ->method('getOptions')
             ->willReturn(new Options($options));
 
-        SentrySdk::getCurrentHub()->bindClient($client);
+        SentrySdk::init($client);
 
-        withScope(function (Scope $scope) use ($event, $expectedRequestContextData, $expectedUser): void {
-            $event = $scope->applyToEvent($event);
+        withScope(function (IsolationScope $scope) use ($event, $expectedRequestContextData, $expectedUser): void {
+            $event = SentrySdk::getGlobalScope()->merge($scope)->applyToEvent($event);
 
             $this->assertNotNull($event);
             $this->assertSame($expectedRequestContextData, $event->getRequest());
diff --git a/tests/Integration/TransactionIntegrationTest.php b/tests/Integration/TransactionIntegrationTest.php
index ab46c6a1b3..91bced84a2 100644
--- a/tests/Integration/TransactionIntegrationTest.php
+++ b/tests/Integration/TransactionIntegrationTest.php
@@ -11,7 +11,7 @@
 use Sentry\EventHint;
 use Sentry\Integration\TransactionIntegration;
 use Sentry\SentrySdk;
-use Sentry\State\Scope;
+use Sentry\State\IsolationScope;
 
 use function Sentry\withScope;
 
@@ -35,10 +35,10 @@ public function testSetupOnce(Event $event, bool $isIntegrationEnabled, ?EventHi
             ->method('getIntegration')
             ->willReturn($isIntegrationEnabled ? $integration : null);
 
-        SentrySdk::getCurrentHub()->bindClient($client);
+        SentrySdk::init($client);
 
-        withScope(function (Scope $scope) use ($event, $hint, $expectedTransaction): void {
-            $event = $scope->applyToEvent($event, $hint);
+        withScope(function (IsolationScope $scope) use ($event, $hint, $expectedTransaction): void {
+            $event = SentrySdk::getGlobalScope()->merge($scope)->applyToEvent($event, $hint);
 
             $this->assertNotNull($event);
             $this->assertSame($event->getTransaction(), $expectedTransaction);
diff --git a/tests/Logs/LogsAggregatorTest.php b/tests/Logs/LogsAggregatorTest.php
index 5278f5039d..02621a0bcd 100644
--- a/tests/Logs/LogsAggregatorTest.php
+++ b/tests/Logs/LogsAggregatorTest.php
@@ -7,10 +7,13 @@
 use PHPUnit\Framework\TestCase;
 use Sentry\Client;
 use Sentry\ClientBuilder;
+use Sentry\ClientInterface;
+use Sentry\Event;
 use Sentry\Logs\LogLevel;
 use Sentry\Logs\LogsAggregator;
+use Sentry\Options;
 use Sentry\SentrySdk;
-use Sentry\State\Hub;
+use Sentry\State\IsolationScope;
 use Sentry\State\Scope;
 use Sentry\Tests\StubTransport;
 use Sentry\Tracing\PropagationContext;
@@ -35,8 +38,7 @@ public function testAttributes(array $attributes, array $expected): void
             'enable_logs' => true,
         ])->getClient();
 
-        $hub = new Hub($client);
-        SentrySdk::setCurrentHub($hub);
+        SentrySdk::init($client);
 
         $aggregator = new LogsAggregator();
 
@@ -93,8 +95,7 @@ public function testMessageFormatting(string $message, array $values, string $ex
             'enable_logs' => true,
         ])->getClient();
 
-        $hub = new Hub($client);
-        SentrySdk::setCurrentHub($hub);
+        SentrySdk::init($client);
 
         $aggregator = new LogsAggregator();
 
@@ -170,22 +171,19 @@ public function testAttributesAreAddedToLogMessage(): void
             'server_name' => 'web-server-01',
         ])->getClient();
 
-        $hub = new Hub($client);
-        SentrySdk::setCurrentHub($hub);
+        SentrySdk::init($client);
 
-        $hub->configureScope(static function (Scope $scope) {
-            $userDataBag = new UserDataBag();
-            $userDataBag->setId('unique_id');
-            $userDataBag->setEmail('foo@example.com');
-            $userDataBag->setUsername('my_user');
-            $scope->setUser($userDataBag);
-        });
+        $userDataBag = new UserDataBag();
+        $userDataBag->setId('unique_id');
+        $userDataBag->setEmail('foo@example.com');
+        $userDataBag->setUsername('my_user');
+        SentrySdk::getIsolationScope()->setUser($userDataBag);
 
         $spanContext = new SpanContext();
         $spanContext->setTraceId(new TraceId('566e3688a61d4bc888951642d6f14a19'));
         $spanContext->setSpanId(new SpanId('566e3688a61d4bc8'));
         $span = new Span($spanContext);
-        $hub->setSpan($span);
+        SentrySdk::getIsolationScope()->setSpan($span);
 
         $aggregator = new LogsAggregator();
 
@@ -211,6 +209,31 @@ public function testAttributesAreAddedToLogMessage(): void
         $this->assertSame('my_user', $attributes->get('user.name')->getValue());
     }
 
+    public function testGlobalScopeAttributesAreAddedToLogMessage(): void
+    {
+        $client = ClientBuilder::create([
+            'enable_logs' => true,
+        ])->getClient();
+
+        SentrySdk::init($client);
+        SentrySdk::getGlobalScope()->setUser(UserDataBag::createFromUserIdentifier('global-user'));
+
+        $spanContext = new SpanContext();
+        $spanContext->setTraceId(new TraceId('566e3688a61d4bc888951642d6f14a19'));
+        $spanContext->setSpanId(new SpanId('566e3688a61d4bc8'));
+        SentrySdk::getIsolationScope()->setSpan(new Span($spanContext));
+
+        $aggregator = new LogsAggregator();
+        $aggregator->add(LogLevel::info(), 'Test message');
+
+        $logs = $aggregator->all();
+        $this->assertCount(1, $logs);
+
+        $attributes = $logs[0]->attributes();
+        $this->assertSame('global-user', $attributes->get('user.id')->getValue());
+        $this->assertSame('566e3688a61d4bc8', $attributes->get('sentry.trace.parent_span_id')->getValue());
+    }
+
     public function testUserAttributesCanBeSetManuallyWithDefaultPiiOff(): void
     {
         $client = ClientBuilder::create([
@@ -218,16 +241,13 @@ public function testUserAttributesCanBeSetManuallyWithDefaultPiiOff(): void
             'send_default_pii' => false,
         ])->getClient();
 
-        $hub = new Hub($client);
-        SentrySdk::setCurrentHub($hub);
+        SentrySdk::init($client);
 
-        $hub->configureScope(static function (Scope $scope) {
-            $userDataBag = new UserDataBag();
-            $userDataBag->setId('unique_id');
-            $userDataBag->setEmail('foo@example.com');
-            $userDataBag->setUsername('my_user');
-            $scope->setUser($userDataBag);
-        });
+        $userDataBag = new UserDataBag();
+        $userDataBag->setId('unique_id');
+        $userDataBag->setEmail('foo@example.com');
+        $userDataBag->setUsername('my_user');
+        SentrySdk::getIsolationScope()->setUser($userDataBag);
 
         $aggregator = new LogsAggregator();
         $aggregator->add(LogLevel::info(), 'User performed action');
@@ -252,8 +272,7 @@ public function testFlushesImmediatelyWhenThresholdIsReached(): void
             'log_flush_threshold' => 2,
         ])->setTransport($transport)->getClient();
 
-        $hub = new Hub($client);
-        SentrySdk::setCurrentHub($hub);
+        SentrySdk::init($client);
 
         $aggregator = new LogsAggregator();
 
@@ -271,6 +290,39 @@ public function testFlushesImmediatelyWhenThresholdIsReached(): void
         $this->assertSame('Second message', StubTransport::$events[0]->getLogs()[1]->getBody());
     }
 
+    public function testFlushCapturesLogsWithProvidedClient(): void
+    {
+        $client = $this->createMock(ClientInterface::class);
+        $client->method('getOptions')
+            ->willReturn(new Options([
+                'enable_logs' => true,
+            ]));
+
+        $fallbackClient = $this->createMock(ClientInterface::class);
+        $fallbackClient->method('getOptions')
+            ->willReturn(new Options([
+                'enable_logs' => true,
+            ]));
+        $fallbackClient->expects($this->never())
+            ->method('captureEvent');
+        SentrySdk::init($fallbackClient);
+
+        $aggregator = new LogsAggregator();
+        $aggregator->add(LogLevel::info(), 'Test message');
+
+        $client->expects($this->once())
+            ->method('captureEvent')
+            ->with(
+                $this->callback(function (Event $event): bool {
+                    $this->assertCount(1, $event->getLogs());
+
+                    return true;
+                })
+            );
+
+        $aggregator->flush($client);
+    }
+
     public function testDoesNotFlushImmediatelyWhenThresholdIsNull(): void
     {
         StubTransport::$events = [];
@@ -281,8 +333,7 @@ public function testDoesNotFlushImmediatelyWhenThresholdIsNull(): void
             'log_flush_threshold' => null,
         ])->setTransport($transport)->getClient();
 
-        $hub = new Hub($client);
-        SentrySdk::setCurrentHub($hub);
+        SentrySdk::init($client);
 
         $aggregator = new LogsAggregator();
 
@@ -303,8 +354,8 @@ public function testDoesNotUsePropagationContextSpanIdAsParentSpanIdWhenNoLocalS
         $propagationContext->setTraceId(new TraceId('771a43a4192642f0b136d5159a501700'));
         $propagationContext->setSpanId(new SpanId('1234567890abcdef'));
 
-        $hub = new Hub($client, new Scope($propagationContext));
-        SentrySdk::setCurrentHub($hub);
+        SentrySdk::init($client);
+        SentrySdk::getCurrentRuntimeContext()->setIsolationScope(new IsolationScope($propagationContext));
 
         $aggregator = new LogsAggregator();
         $aggregator->add(LogLevel::info(), 'Test message');
@@ -325,8 +376,7 @@ public function testUsesExternalPropagationContextWhenNoLocalSpanExists(): void
             'enable_logs' => true,
         ])->getClient();
 
-        $hub = new Hub($client);
-        SentrySdk::setCurrentHub($hub);
+        SentrySdk::init($client);
 
         Scope::registerExternalPropagationContext(static function (): array {
             return [
diff --git a/tests/Logs/LogsTest.php b/tests/Logs/LogsTest.php
index 4dd361b564..a0a4053b39 100644
--- a/tests/Logs/LogsTest.php
+++ b/tests/Logs/LogsTest.php
@@ -13,7 +13,6 @@
 use Sentry\Logs\LogLevel;
 use Sentry\Options;
 use Sentry\SentrySdk;
-use Sentry\State\Hub;
 use Sentry\Transport\Result;
 use Sentry\Transport\ResultStatus;
 use Sentry\Transport\TransportInterface;
@@ -36,8 +35,7 @@ public function testLogNotSentWhenDisabled(): void
         $client->expects($this->never())
                ->method('captureEvent');
 
-        $hub = new Hub($client);
-        SentrySdk::setCurrentHub($hub);
+        SentrySdk::init($client);
 
         logger()->info('Some info message');
 
@@ -186,8 +184,7 @@ private function assertEvent(callable $assert, array $options = []): ClientInter
 
         $client = ClientBuilder::create($clientOptions)->setTransport($transport)->getClient();
 
-        $hub = new Hub($client);
-        SentrySdk::setCurrentHub($hub);
+        SentrySdk::init($client);
 
         return $client;
     }
diff --git a/tests/Metrics/TraceMetricsTest.php b/tests/Metrics/TraceMetricsTest.php
index 1191e076ec..97ab7eebcb 100644
--- a/tests/Metrics/TraceMetricsTest.php
+++ b/tests/Metrics/TraceMetricsTest.php
@@ -6,14 +6,17 @@
 
 use PHPUnit\Framework\TestCase;
 use Sentry\Client;
+use Sentry\ClientInterface;
+use Sentry\Event;
 use Sentry\Metrics\MetricsAggregator;
 use Sentry\Metrics\Types\CounterMetric;
 use Sentry\Metrics\Types\DistributionMetric;
 use Sentry\Metrics\Types\GaugeMetric;
 use Sentry\Metrics\Types\Metric;
 use Sentry\Options;
-use Sentry\State\HubAdapter;
+use Sentry\SentrySdk;
 use Sentry\State\Scope;
+use Sentry\UserDataBag;
 
 use function Sentry\traceMetrics;
 
@@ -21,7 +24,7 @@ final class TraceMetricsTest extends TestCase
 {
     protected function setUp(): void
     {
-        HubAdapter::getInstance()->bindClient(new Client(new Options(), StubTransport::getInstance()));
+        SentrySdk::init(new Client(new Options(), StubTransport::getInstance()));
         StubTransport::$events = [];
     }
 
@@ -75,7 +78,7 @@ public function testDistributionMetrics(): void
 
     public function testFlushesImmediatelyWhenMetricFlushThresholdIsReached(): void
     {
-        HubAdapter::getInstance()->bindClient(new Client(new Options([
+        SentrySdk::init(new Client(new Options([
             'metric_flush_threshold' => 2,
         ]), StubTransport::getInstance()));
 
@@ -95,7 +98,7 @@ public function testFlushesImmediatelyWhenMetricFlushThresholdIsReached(): void
 
     public function testDoesNotFlushImmediatelyWhenMetricFlushThresholdIsNull(): void
     {
-        HubAdapter::getInstance()->bindClient(new Client(new Options([
+        SentrySdk::init(new Client(new Options([
             'metric_flush_threshold' => null,
         ]), StubTransport::getInstance()));
 
@@ -110,9 +113,55 @@ public function testDoesNotFlushImmediatelyWhenMetricFlushThresholdIsNull(): voi
         $this->assertCount(2, StubTransport::$events[0]->getMetrics());
     }
 
+    public function testGlobalScopeAttributesAreAddedToMetric(): void
+    {
+        SentrySdk::getGlobalScope()->setUser(UserDataBag::createFromUserIdentifier('global-user'));
+
+        traceMetrics()->count('test-count', 2);
+        traceMetrics()->flush();
+
+        $this->assertCount(1, StubTransport::$events);
+
+        $metric = StubTransport::$events[0]->getMetrics()[0];
+        $this->assertSame('global-user', $metric->getAttributes()->get('user.id')->getValue());
+    }
+
+    public function testFlushCapturesMetricsWithProvidedClient(): void
+    {
+        $client = $this->createMock(ClientInterface::class);
+        $client->method('getOptions')
+            ->willReturn(new Options([
+                'enable_metrics' => true,
+            ]));
+
+        $fallbackClient = $this->createMock(ClientInterface::class);
+        $fallbackClient->method('getOptions')
+            ->willReturn(new Options([
+                'enable_metrics' => true,
+            ]));
+        $fallbackClient->expects($this->never())
+            ->method('captureEvent');
+        SentrySdk::init($fallbackClient);
+
+        $aggregator = new MetricsAggregator();
+        $aggregator->add(CounterMetric::TYPE, 'test-count', 2, ['foo' => 'bar'], null);
+
+        $client->expects($this->once())
+            ->method('captureEvent')
+            ->with(
+                $this->callback(function (Event $event): bool {
+                    $this->assertCount(1, $event->getMetrics());
+
+                    return true;
+                })
+            );
+
+        $aggregator->flush($client);
+    }
+
     public function testMetricsBufferFullWhenMetricFlushThresholdIsNull(): void
     {
-        HubAdapter::getInstance()->bindClient(new Client(new Options([
+        SentrySdk::init(new Client(new Options([
             'metric_flush_threshold' => null,
         ]), StubTransport::getInstance()));
 
@@ -131,7 +180,7 @@ public function testMetricsBufferFullWhenMetricFlushThresholdIsNull(): void
 
     public function testEnableMetrics(): void
     {
-        HubAdapter::getInstance()->bindClient(new Client(new Options([
+        SentrySdk::init(new Client(new Options([
             'enable_metrics' => false,
         ]), StubTransport::getInstance()));
 
@@ -143,7 +192,7 @@ public function testEnableMetrics(): void
 
     public function testBeforeSendMetricAltersContent(): void
     {
-        HubAdapter::getInstance()->bindClient(new Client(new Options([
+        SentrySdk::init(new Client(new Options([
             'before_send_metric' => static function (Metric $metric) {
                 $metric->setValue(99999);
 
diff --git a/tests/Monolog/BreadcrumbHandlerTest.php b/tests/Monolog/BreadcrumbHandlerTest.php
index 812c5d12fd..e9f5765edd 100644
--- a/tests/Monolog/BreadcrumbHandlerTest.php
+++ b/tests/Monolog/BreadcrumbHandlerTest.php
@@ -8,8 +8,11 @@
 use Monolog\LogRecord;
 use PHPUnit\Framework\TestCase;
 use Sentry\Breadcrumb;
+use Sentry\ClientInterface;
+use Sentry\Event;
 use Sentry\Monolog\BreadcrumbHandler;
-use Sentry\State\HubInterface;
+use Sentry\Options;
+use Sentry\SentrySdk;
 
 final class BreadcrumbHandlerTest extends TestCase
 {
@@ -20,22 +23,29 @@ final class BreadcrumbHandlerTest extends TestCase
      */
     public function testHandle($record, Breadcrumb $expectedBreadcrumb): void
     {
-        $hub = $this->createMock(HubInterface::class);
-        $hub->expects($this->once())
-            ->method('addBreadcrumb')
-            ->with($this->callback(function (Breadcrumb $breadcrumb) use ($expectedBreadcrumb): bool {
-                $this->assertSame($expectedBreadcrumb->getMessage(), $breadcrumb->getMessage());
-                $this->assertSame($expectedBreadcrumb->getLevel(), $breadcrumb->getLevel());
-                $this->assertSame($expectedBreadcrumb->getType(), $breadcrumb->getType());
-                $this->assertEquals($expectedBreadcrumb->getTimestamp(), $breadcrumb->getTimestamp());
-                $this->assertSame($expectedBreadcrumb->getCategory(), $breadcrumb->getCategory());
-                $this->assertEquals($expectedBreadcrumb->getMetadata(), $breadcrumb->getMetadata());
-
-                return true;
-            }));
-
-        $handler = new BreadcrumbHandler($hub);
+        $client = $this->createMock(ClientInterface::class);
+        $client->expects($this->once())
+            ->method('getOptions')
+            ->willReturn(new Options());
+
+        SentrySdk::init($client);
+
+        $handler = new BreadcrumbHandler();
         $handler->handle($record);
+
+        $event = Event::createEvent();
+        SentrySdk::getGlobalScope()->merge(SentrySdk::getIsolationScope())->applyToEvent($event);
+
+        $this->assertCount(1, $event->getBreadcrumbs());
+
+        $breadcrumb = $event->getBreadcrumbs()[0];
+
+        $this->assertSame($expectedBreadcrumb->getMessage(), $breadcrumb->getMessage());
+        $this->assertSame($expectedBreadcrumb->getLevel(), $breadcrumb->getLevel());
+        $this->assertSame($expectedBreadcrumb->getType(), $breadcrumb->getType());
+        $this->assertEquals($expectedBreadcrumb->getTimestamp(), $breadcrumb->getTimestamp());
+        $this->assertSame($expectedBreadcrumb->getCategory(), $breadcrumb->getCategory());
+        $this->assertEquals($expectedBreadcrumb->getMetadata(), $breadcrumb->getMetadata());
     }
 
     /**
diff --git a/tests/Monolog/ExceptionToSentryIssueHandlerTest.php b/tests/Monolog/ExceptionToSentryIssueHandlerTest.php
index 20dd681397..8d8beae655 100644
--- a/tests/Monolog/ExceptionToSentryIssueHandlerTest.php
+++ b/tests/Monolog/ExceptionToSentryIssueHandlerTest.php
@@ -11,8 +11,8 @@
 use Sentry\ClientInterface;
 use Sentry\Event;
 use Sentry\Monolog\ExceptionToSentryIssueHandler;
-use Sentry\State\Hub;
-use Sentry\State\Scope;
+use Sentry\SentrySdk;
+use Sentry\State\IsolationScope;
 
 final class ExceptionToSentryIssueHandlerTest extends TestCase
 {
@@ -30,8 +30,9 @@ public function testHandleCapturesExceptionAndAddsMetadata($record, \Throwable $
             ->method('captureException')
             ->with(
                 $this->identicalTo($exception),
-                $this->callback(function (Scope $scopeArg) use ($expectedExtra): bool {
-                    $event = $scopeArg->applyToEvent(Event::createEvent());
+                $this->callback(function (IsolationScope $scopeArg) use ($expectedExtra): bool {
+                    $globalScope = SentrySdk::getGlobalScope();
+                    $event = $globalScope->merge($scopeArg)->applyToEvent(Event::createEvent());
 
                     $this->assertNotNull($event);
                     $this->assertSame($expectedExtra, $event->getExtra());
@@ -41,7 +42,9 @@ public function testHandleCapturesExceptionAndAddsMetadata($record, \Throwable $
                 null
             );
 
-        $handler = new ExceptionToSentryIssueHandler(new Hub($client, new Scope()));
+        SentrySdk::init($client);
+
+        $handler = new ExceptionToSentryIssueHandler();
 
         $this->assertTrue($handler->isHandling($record));
         $handler->handle($record);
@@ -55,9 +58,11 @@ public function testHandleReturnsFalseWhenBubblingEnabled(): void
         $client = $this->createMock(ClientInterface::class);
         $client->expects($this->once())
             ->method('captureException')
-            ->with($this->identicalTo($exception), $this->isInstanceOf(Scope::class), null);
+            ->with($this->identicalTo($exception), $this->isInstanceOf(IsolationScope::class), null);
+
+        SentrySdk::init($client);
 
-        $handler = new ExceptionToSentryIssueHandler(new Hub($client, new Scope()), Logger::WARNING);
+        $handler = new ExceptionToSentryIssueHandler(Logger::WARNING);
         $record = RecordFactory::create(
             'foo bar',
             Logger::WARNING,
@@ -80,9 +85,11 @@ public function testHandleReturnsTrueWhenBubblingDisabled(): void
         $client = $this->createMock(ClientInterface::class);
         $client->expects($this->once())
             ->method('captureException')
-            ->with($this->identicalTo($exception), $this->isInstanceOf(Scope::class), null);
+            ->with($this->identicalTo($exception), $this->isInstanceOf(IsolationScope::class), null);
+
+        SentrySdk::init($client);
 
-        $handler = new ExceptionToSentryIssueHandler(new Hub($client, new Scope()), Logger::WARNING, false);
+        $handler = new ExceptionToSentryIssueHandler(Logger::WARNING, false);
         $record = RecordFactory::create(
             'foo bar',
             Logger::WARNING,
@@ -109,7 +116,9 @@ public function testHandleIgnoresRecordsWithoutThrowable($record): void
         $client->expects($this->never())
             ->method('captureException');
 
-        $handler = new ExceptionToSentryIssueHandler(new Hub($client, new Scope()), Logger::DEBUG, false);
+        SentrySdk::init($client);
+
+        $handler = new ExceptionToSentryIssueHandler(Logger::DEBUG, false);
 
         $this->assertTrue($handler->isHandling($record));
         $this->assertFalse($handler->handle($record));
@@ -124,7 +133,9 @@ public function testHandleIgnoresRecordsBelowThreshold(): void
         $client->expects($this->never())
             ->method('captureException');
 
-        $handler = new ExceptionToSentryIssueHandler(new Hub($client, new Scope()), Logger::ERROR, false);
+        SentrySdk::init($client);
+
+        $handler = new ExceptionToSentryIssueHandler(Logger::ERROR, false);
         $record = RecordFactory::create(
             'foo bar',
             Logger::WARNING,
@@ -145,7 +156,7 @@ public function testLegacyIsHandlingUsesMinimalLevelRecord(): void
             $this->markTestSkipped('Test only works for Monolog < 3');
         }
 
-        $handler = new ExceptionToSentryIssueHandler(new Hub($this->createMock(ClientInterface::class), new Scope()), Logger::WARNING);
+        $handler = new ExceptionToSentryIssueHandler(Logger::WARNING);
 
         $this->assertTrue($handler->isHandling(['level' => Logger::WARNING]));
         $this->assertFalse($handler->isHandling(['level' => Logger::INFO]));
diff --git a/tests/Monolog/LogToSentryIssueHandlerTest.php b/tests/Monolog/LogToSentryIssueHandlerTest.php
index 7bbff023b4..087057039e 100644
--- a/tests/Monolog/LogToSentryIssueHandlerTest.php
+++ b/tests/Monolog/LogToSentryIssueHandlerTest.php
@@ -14,9 +14,9 @@
 use Sentry\EventHint;
 use Sentry\Monolog\ExceptionToSentryIssueHandler;
 use Sentry\Monolog\LogToSentryIssueHandler;
+use Sentry\SentrySdk;
 use Sentry\Severity;
-use Sentry\State\Hub;
-use Sentry\State\Scope;
+use Sentry\State\IsolationScope;
 use Sentry\Tests\StubTransport;
 
 final class LogToSentryIssueHandlerTest extends TestCase
@@ -49,8 +49,9 @@ public function testHandleCapturesLogMessageAsIssue(bool $fillExtraContext, $rec
 
                     return true;
                 }),
-                $this->callback(function (Scope $scopeArg) use ($expectedExtra): bool {
-                    $event = $scopeArg->applyToEvent(Event::createEvent());
+                $this->callback(function (IsolationScope $scopeArg) use ($expectedExtra): bool {
+                    $globalScope = SentrySdk::getGlobalScope();
+                    $event = $globalScope->merge($scopeArg)->applyToEvent(Event::createEvent());
 
                     $this->assertNotNull($event);
                     $this->assertSame($expectedExtra, $event->getExtra());
@@ -59,7 +60,9 @@ public function testHandleCapturesLogMessageAsIssue(bool $fillExtraContext, $rec
                 })
             );
 
-        $handler = new LogToSentryIssueHandler(new Hub($client, new Scope()), Logger::DEBUG, true, $fillExtraContext);
+        SentrySdk::init($client);
+
+        $handler = new LogToSentryIssueHandler(Logger::DEBUG, true, $fillExtraContext);
 
         $this->assertTrue($handler->isHandling($record));
         $this->assertFalse($handler->handle($record));
@@ -71,9 +74,11 @@ public function testHandleReturnsTrueWhenBubblingDisabled(): void
         $client = $this->createMock(ClientInterface::class);
         $client->expects($this->once())
             ->method('captureEvent')
-            ->with($this->isInstanceOf(Event::class), $this->isInstanceOf(EventHint::class), $this->isInstanceOf(Scope::class));
+            ->with($this->isInstanceOf(Event::class), $this->isInstanceOf(EventHint::class), $this->isInstanceOf(IsolationScope::class));
+
+        SentrySdk::init($client);
 
-        $handler = new LogToSentryIssueHandler(new Hub($client, new Scope()), Logger::WARNING, false);
+        $handler = new LogToSentryIssueHandler(Logger::WARNING, false);
         $record = RecordFactory::create('foo bar', Logger::WARNING, 'channel.foo', [], []);
 
         $this->assertTrue($handler->isHandling($record));
@@ -87,7 +92,9 @@ public function testHandleIgnoresRecordsWithThrowableExceptionContext(): void
         $client->expects($this->never())
             ->method('captureEvent');
 
-        $handler = new LogToSentryIssueHandler(new Hub($client, new Scope()), Logger::DEBUG, false);
+        SentrySdk::init($client);
+
+        $handler = new LogToSentryIssueHandler(Logger::DEBUG, false);
         $record = RecordFactory::create(
             'foo bar',
             Logger::WARNING,
@@ -111,8 +118,9 @@ public function testHandleCapturesRecordsWithNonThrowableExceptionContext(): voi
             ->with(
                 $this->isInstanceOf(Event::class),
                 $this->isInstanceOf(EventHint::class),
-                $this->callback(function (Scope $scopeArg): bool {
-                    $event = $scopeArg->applyToEvent(Event::createEvent());
+                $this->callback(function (IsolationScope $scopeArg): bool {
+                    $globalScope = SentrySdk::getGlobalScope();
+                    $event = $globalScope->merge($scopeArg)->applyToEvent(Event::createEvent());
 
                     $this->assertNotNull($event);
                     $this->assertSame([
@@ -127,7 +135,9 @@ public function testHandleCapturesRecordsWithNonThrowableExceptionContext(): voi
                 })
             );
 
-        $handler = new LogToSentryIssueHandler(new Hub($client, new Scope()), Logger::DEBUG, false, true);
+        SentrySdk::init($client);
+
+        $handler = new LogToSentryIssueHandler(Logger::DEBUG, false, true);
         $record = RecordFactory::create(
             'foo bar',
             Logger::WARNING,
@@ -149,7 +159,9 @@ public function testHandleIgnoresRecordsBelowThreshold(): void
         $client->expects($this->never())
             ->method('captureEvent');
 
-        $handler = new LogToSentryIssueHandler(new Hub($client, new Scope()), Logger::ERROR, false);
+        SentrySdk::init($client);
+
+        $handler = new LogToSentryIssueHandler(Logger::ERROR, false);
         $record = RecordFactory::create('foo bar', Logger::WARNING, 'channel.foo', [], []);
 
         $this->assertFalse($handler->isHandling($record));
@@ -162,7 +174,7 @@ public function testLegacyIsHandlingUsesMinimalLevelRecord(): void
             $this->markTestSkipped('Test only works for Monolog < 3');
         }
 
-        $handler = new LogToSentryIssueHandler(new Hub($this->createMock(ClientInterface::class), new Scope()), Logger::WARNING);
+        $handler = new LogToSentryIssueHandler(Logger::WARNING);
 
         $this->assertTrue($handler->isHandling(['level' => Logger::WARNING]));
         $this->assertFalse($handler->isHandling(['level' => Logger::INFO]));
@@ -173,11 +185,11 @@ public function testLogAndExceptionIssueHandlersReplaceLegacyHandlerUseCases():
         $client = ClientBuilder::create()
             ->setTransport(StubTransport::getInstance())
             ->getClient();
-        $hub = new Hub($client, new Scope());
+        SentrySdk::init($client);
 
         $logger = new Logger('channel.foo', [
-            new LogToSentryIssueHandler($hub, Logger::WARNING, true, true),
-            new ExceptionToSentryIssueHandler($hub, Logger::WARNING),
+            new LogToSentryIssueHandler(Logger::WARNING, true, true),
+            new ExceptionToSentryIssueHandler(Logger::WARNING),
         ]);
 
         $logger->warning('plain warning', [
diff --git a/tests/Monolog/LogsHandlerTest.php b/tests/Monolog/LogsHandlerTest.php
index f3f2965cc3..0d94c68006 100644
--- a/tests/Monolog/LogsHandlerTest.php
+++ b/tests/Monolog/LogsHandlerTest.php
@@ -13,7 +13,6 @@
 use Sentry\Logs\Logs;
 use Sentry\Monolog\LogsHandler;
 use Sentry\SentrySdk;
-use Sentry\State\Hub;
 use Sentry\Tests\StubTransport;
 
 final class LogsHandlerTest extends TestCase
@@ -28,8 +27,7 @@ protected function setUp(): void
             },
         ])->getClient();
 
-        $hub = new Hub($client);
-        SentrySdk::setCurrentHub($hub);
+        SentrySdk::init($client);
     }
 
     /**
@@ -108,8 +106,7 @@ public function testLogsHandlerDestructor(): void
         ])->setTransport($transport)
             ->getClient();
 
-        $hub = new Hub($client);
-        SentrySdk::setCurrentHub($hub);
+        SentrySdk::init($client);
 
         $this->handleLogAndDrop();
 
diff --git a/tests/SentrySdkExtension.php b/tests/SentrySdkExtension.php
index b50bc2ed85..afe5ccb1a8 100644
--- a/tests/SentrySdkExtension.php
+++ b/tests/SentrySdkExtension.php
@@ -13,7 +13,7 @@ final class SentrySdkExtension implements BeforeTestHookInterface
 {
     public function executeBeforeTest(string $test): void
     {
-        $reflectionProperty = new \ReflectionProperty(SentrySdk::class, 'currentHub');
+        $reflectionProperty = new \ReflectionProperty(SentrySdk::class, 'globalScope');
         if (\PHP_VERSION_ID < 80100) {
             $reflectionProperty->setAccessible(true);
         }
diff --git a/tests/SentrySdkTest.php b/tests/SentrySdkTest.php
index 3ce3d6f12d..911b8ee879 100644
--- a/tests/SentrySdkTest.php
+++ b/tests/SentrySdkTest.php
@@ -11,63 +11,129 @@
 use Sentry\NoOpClient;
 use Sentry\Options;
 use Sentry\SentrySdk;
-use Sentry\State\Hub;
-use Sentry\State\Scope;
+use Sentry\State\IsolationScope;
 use Sentry\Tracing\Span;
 use Sentry\Tracing\SpanContext;
+use Sentry\Tracing\TransactionContext;
 use Sentry\Transport\Result;
 use Sentry\Transport\ResultStatus;
 
+use function Sentry\startTransaction;
+
 final class SentrySdkTest extends TestCase
 {
-    public function testInit(): void
+    public function testInitResetsRuntimeContext(): void
     {
-        $hub1 = SentrySdk::init();
-        $hub2 = SentrySdk::getCurrentHub();
+        $previousScope = SentrySdk::getIsolationScope();
+        $previousScope->setTag('runtime', 'old');
+
+        SentrySdk::init();
+
+        $currentScope = SentrySdk::getIsolationScope();
 
-        $this->assertSame($hub1, $hub2);
-        $this->assertNotSame(SentrySdk::init(), SentrySdk::init());
+        $this->assertNotSame($previousScope, $currentScope);
+
+        $event = SentrySdk::getGlobalScope()->merge($currentScope)->applyToEvent(Event::createEvent());
+
+        $this->assertNotNull($event);
+        $this->assertSame([], $event->getTags());
     }
 
-    public function testGetCurrentHub(): void
+    public function testGetGlobalScope(): void
     {
-        SentrySdk::init();
+        $scope = SentrySdk::getGlobalScope();
+
+        $this->assertSame($scope, SentrySdk::getGlobalScope());
+    }
+
+    public function testGetIsolationScope(): void
+    {
+        $scope = SentrySdk::getIsolationScope();
+
+        $this->assertSame($scope, SentrySdk::getIsolationScope());
+    }
+
+    public function testGetClientReturnsCachedNoOpFallbackBeforeInit(): void
+    {
+        $client = SentrySdk::getClient();
+
+        $this->assertInstanceOf(NoOpClient::class, $client);
+        $this->assertSame($client, SentrySdk::getClient());
+    }
+
+    public function testGetClientReturnsGlobalScopeClient(): void
+    {
+        $client = $this->createMock(ClientInterface::class);
+
+        SentrySdk::getGlobalScope()->setClient($client);
+
+        $this->assertSame($client, SentrySdk::getClient());
+    }
+
+    public function testGetClientReturnsIsolationScopeClientBeforeGlobalScopeClient(): void
+    {
+        $globalClient = $this->createMock(ClientInterface::class);
+        $isolationClient = $this->createMock(ClientInterface::class);
+
+        SentrySdk::getGlobalScope()->setClient($globalClient);
+        SentrySdk::getIsolationScope()->setClient($isolationClient);
 
-        $hub2 = SentrySdk::getCurrentHub();
-        $hub3 = SentrySdk::getCurrentHub();
+        $this->assertSame($isolationClient, SentrySdk::getClient());
+    }
+
+    public function testStartContextUsesSeparateIsolationScope(): void
+    {
+        $globalIsolationScope = SentrySdk::getIsolationScope();
+
+        SentrySdk::startContext();
+
+        $contextIsolationScope = SentrySdk::getIsolationScope();
+
+        $this->assertNotSame($globalIsolationScope, $contextIsolationScope);
+
+        SentrySdk::endContext();
+
+        $this->assertSame($globalIsolationScope, SentrySdk::getIsolationScope());
+    }
+
+    public function testInitWithClientSetsGlobalScopeClient(): void
+    {
+        $client = $this->createMock(ClientInterface::class);
+
+        SentrySdk::init($client);
 
-        $this->assertSame($hub2, $hub3);
+        $this->assertSame($client, SentrySdk::getClient());
     }
 
-    public function testSetCurrentHub(): void
+    public function testInitDoesNotResetGlobalScope(): void
     {
-        $hub = new Hub(new NoOpClient());
+        $globalScope = SentrySdk::getGlobalScope();
+        $globalScope->setTag('baseline', 'yes');
+
+        SentrySdk::init();
 
-        $this->assertSame($hub, SentrySdk::setCurrentHub($hub));
-        $this->assertSame($hub, SentrySdk::getCurrentHub());
+        $this->assertSame($globalScope, SentrySdk::getGlobalScope());
+
+        $event = $globalScope->merge(new IsolationScope())->applyToEvent(Event::createEvent());
+
+        $this->assertNotNull($event);
+        $this->assertSame(['baseline' => 'yes'], $event->getTags());
     }
 
     public function testStartAndEndContextIsolateScopeData(): void
     {
         SentrySdk::init();
 
-        SentrySdk::getCurrentHub()->configureScope(static function (Scope $scope): void {
-            $scope->setTag('baseline', 'yes');
-        });
+        SentrySdk::getIsolationScope()->setTag('baseline', 'yes');
 
         SentrySdk::startContext();
 
-        SentrySdk::getCurrentHub()->configureScope(static function (Scope $scope): void {
-            $scope->setTag('request', 'yes');
-        });
+        SentrySdk::getIsolationScope()->setTag('request', 'yes');
 
         SentrySdk::endContext();
 
         $event = Event::createEvent();
-
-        SentrySdk::getCurrentHub()->configureScope(static function (Scope $scope) use (&$event): void {
-            $event = $scope->applyToEvent($event);
-        });
+        $event = SentrySdk::getGlobalScope()->merge(SentrySdk::getIsolationScope())->applyToEvent($event);
 
         $this->assertArrayHasKey('baseline', $event->getTags());
         $this->assertArrayNotHasKey('request', $event->getTags());
@@ -78,16 +144,15 @@ public function testStartContextDoesNotInheritBaselineSpan(): void
         SentrySdk::init();
 
         $baselineSpan = new Span(new SpanContext());
-        SentrySdk::getCurrentHub()->setSpan($baselineSpan);
+        SentrySdk::getIsolationScope()->setSpan($baselineSpan);
 
         SentrySdk::startContext();
-        $contextHub = SentrySdk::getCurrentHub();
 
-        $this->assertNull($contextHub->getSpan());
+        $this->assertNull(SentrySdk::getIsolationScope()->getSpan());
 
         SentrySdk::endContext();
 
-        $this->assertSame($baselineSpan, SentrySdk::getCurrentHub()->getSpan());
+        $this->assertSame($baselineSpan, SentrySdk::getIsolationScope()->getSpan());
     }
 
     public function testStartContextCreatesFreshPropagationContext(): void
@@ -113,16 +178,16 @@ public function testWithContextResetsSpanAndTransactionAcrossInvocations(): void
         SentrySdk::init();
 
         SentrySdk::withContext(function (): void {
-            $transaction = SentrySdk::getCurrentHub()->startTransaction(new \Sentry\Tracing\TransactionContext('request-1'));
-            SentrySdk::getCurrentHub()->setSpan($transaction);
+            $transaction = startTransaction(new TransactionContext('request-1'));
+            SentrySdk::getIsolationScope()->setSpan($transaction);
 
-            $this->assertSame($transaction, SentrySdk::getCurrentHub()->getSpan());
-            $this->assertSame($transaction, SentrySdk::getCurrentHub()->getTransaction());
+            $this->assertSame($transaction, SentrySdk::getIsolationScope()->getSpan());
+            $this->assertSame($transaction, SentrySdk::getIsolationScope()->getTransaction());
         });
 
         SentrySdk::withContext(function (): void {
-            $this->assertNull(SentrySdk::getCurrentHub()->getSpan());
-            $this->assertNull(SentrySdk::getCurrentHub()->getTransaction());
+            $this->assertNull(SentrySdk::getIsolationScope()->getSpan());
+            $this->assertNull(SentrySdk::getIsolationScope()->getTransaction());
         });
     }
 
@@ -130,22 +195,22 @@ public function testNestedStartContextIsNoOp(): void
     {
         SentrySdk::init();
 
-        $globalHub = SentrySdk::getCurrentHub();
+        $globalScope = SentrySdk::getIsolationScope();
 
         SentrySdk::startContext();
-        $firstContextHub = SentrySdk::getCurrentHub();
+        $firstContextScope = SentrySdk::getIsolationScope();
 
         SentrySdk::startContext();
-        $secondContextHub = SentrySdk::getCurrentHub();
+        $secondContextScope = SentrySdk::getIsolationScope();
 
-        $this->assertNotSame($globalHub, $firstContextHub);
-        $this->assertSame($firstContextHub, $secondContextHub);
+        $this->assertNotSame($globalScope, $firstContextScope);
+        $this->assertSame($firstContextScope, $secondContextScope);
 
         SentrySdk::endContext();
-        $this->assertSame($globalHub, SentrySdk::getCurrentHub());
+        $this->assertSame($globalScope, SentrySdk::getIsolationScope());
 
         SentrySdk::endContext();
-        $this->assertSame($globalHub, SentrySdk::getCurrentHub());
+        $this->assertSame($globalScope, SentrySdk::getIsolationScope());
     }
 
     public function testEndContextFlushesClientTransportWithOptionalTimeout(): void
@@ -160,7 +225,7 @@ public function testEndContextFlushesClientTransportWithOptionalTimeout(): void
             ->with(12)
             ->willReturn(new Result(ResultStatus::success()));
 
-        SentrySdk::init()->bindClient($client);
+        SentrySdk::init($client);
 
         SentrySdk::startContext();
         SentrySdk::endContext(12);
@@ -175,83 +240,79 @@ public function testFlushFlushesClientTransport(): void
             ->with(null)
             ->willReturn(new Result(ResultStatus::success()));
 
-        SentrySdk::init()->bindClient($client);
+        SentrySdk::init($client);
 
         SentrySdk::flush();
     }
 
-    public function testWithContextReturnsCallbackResultAndRestoresGlobalHub(): void
+    public function testWithContextReturnsCallbackResultAndRestoresGlobalIsolationScope(): void
     {
         SentrySdk::init();
 
-        $globalHub = SentrySdk::getCurrentHub();
-        $callbackHub = null;
+        $globalScope = SentrySdk::getIsolationScope();
+        $callbackScope = null;
 
-        $result = SentrySdk::withContext(static function () use (&$callbackHub): string {
-            $callbackHub = SentrySdk::getCurrentHub();
+        $result = SentrySdk::withContext(static function () use (&$callbackScope): string {
+            $callbackScope = SentrySdk::getIsolationScope();
 
             return 'ok';
         });
 
         $this->assertSame('ok', $result);
-        $this->assertNotNull($callbackHub);
-        $this->assertNotSame($globalHub, $callbackHub);
-        $this->assertSame($globalHub, SentrySdk::getCurrentHub());
+        $this->assertNotNull($callbackScope);
+        $this->assertNotSame($globalScope, $callbackScope);
+        $this->assertSame($globalScope, SentrySdk::getIsolationScope());
     }
 
     public function testNestedWithContextReusesOuterContext(): void
     {
         SentrySdk::init();
 
-        $globalHub = SentrySdk::getCurrentHub();
-        $outerHub = null;
-        $innerHub = null;
+        $globalScope = SentrySdk::getIsolationScope();
+        $outerScope = null;
+        $innerScope = null;
         $outerContextId = null;
         $innerContextId = null;
 
-        SentrySdk::withContext(function () use (&$outerHub, &$innerHub, &$outerContextId, &$innerContextId, $globalHub): void {
-            $outerHub = SentrySdk::getCurrentHub();
+        SentrySdk::withContext(function () use (&$outerScope, &$innerScope, &$outerContextId, &$innerContextId, $globalScope): void {
+            $outerScope = SentrySdk::getIsolationScope();
             $outerContextId = SentrySdk::getCurrentRuntimeContext()->getId();
 
-            SentrySdk::getCurrentHub()->configureScope(static function (Scope $scope): void {
-                $scope->setTag('outer', 'yes');
-            });
+            SentrySdk::getIsolationScope()->setTag('outer', 'yes');
 
-            SentrySdk::withContext(static function () use (&$innerHub, &$innerContextId): void {
-                $innerHub = SentrySdk::getCurrentHub();
+            SentrySdk::withContext(static function () use (&$innerScope, &$innerContextId): void {
+                $innerScope = SentrySdk::getIsolationScope();
                 $innerContextId = SentrySdk::getCurrentRuntimeContext()->getId();
             });
 
             $event = Event::createEvent();
 
-            SentrySdk::getCurrentHub()->configureScope(static function (Scope $scope) use (&$event): void {
-                $event = $scope->applyToEvent($event);
-            });
+            $event = SentrySdk::getGlobalScope()->merge(SentrySdk::getIsolationScope())->applyToEvent($event);
 
-            $this->assertNotSame($globalHub, SentrySdk::getCurrentHub());
+            $this->assertNotSame($globalScope, SentrySdk::getIsolationScope());
             $this->assertSame('yes', $event->getTags()['outer'] ?? null);
             $this->assertSame($outerContextId, SentrySdk::getCurrentRuntimeContext()->getId());
         });
 
-        $this->assertNotNull($outerHub);
-        $this->assertNotNull($innerHub);
+        $this->assertNotNull($outerScope);
+        $this->assertNotNull($innerScope);
         $this->assertNotNull($outerContextId);
         $this->assertNotNull($innerContextId);
-        $this->assertSame($outerHub, $innerHub);
+        $this->assertSame($outerScope, $innerScope);
         $this->assertSame($outerContextId, $innerContextId);
-        $this->assertSame($globalHub, SentrySdk::getCurrentHub());
+        $this->assertSame($globalScope, SentrySdk::getIsolationScope());
     }
 
     public function testWithContextEndsContextWhenCallbackThrows(): void
     {
         SentrySdk::init();
 
-        $globalHub = SentrySdk::getCurrentHub();
-        $callbackHub = null;
+        $globalScope = SentrySdk::getIsolationScope();
+        $callbackScope = null;
 
         try {
-            SentrySdk::withContext(static function () use (&$callbackHub): void {
-                $callbackHub = SentrySdk::getCurrentHub();
+            SentrySdk::withContext(static function () use (&$callbackScope): void {
+                $callbackScope = SentrySdk::getIsolationScope();
 
                 throw new \RuntimeException('boom');
             });
@@ -261,18 +322,16 @@ public function testWithContextEndsContextWhenCallbackThrows(): void
             $this->assertSame('boom', $exception->getMessage());
         }
 
-        $this->assertNotNull($callbackHub);
-        $this->assertNotSame($globalHub, $callbackHub);
-        $this->assertSame($globalHub, SentrySdk::getCurrentHub());
+        $this->assertNotNull($callbackScope);
+        $this->assertNotSame($globalScope, $callbackScope);
+        $this->assertSame($globalScope, SentrySdk::getIsolationScope());
     }
 
     private function getCurrentScopeTraceparent(): string
     {
         $traceparent = '';
 
-        SentrySdk::getCurrentHub()->configureScope(static function (Scope $scope) use (&$traceparent): void {
-            $traceparent = $scope->getPropagationContext()->toTraceparent();
-        });
+        $traceparent = SentrySdk::getIsolationScope()->getPropagationContext()->toTraceparent();
 
         return $traceparent;
     }
diff --git a/tests/State/BreadcrumbRecorderTest.php b/tests/State/BreadcrumbRecorderTest.php
new file mode 100644
index 0000000000..a61ef479f4
--- /dev/null
+++ b/tests/State/BreadcrumbRecorderTest.php
@@ -0,0 +1,133 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Sentry\Tests\State;
+
+use PHPUnit\Framework\TestCase;
+use Sentry\Breadcrumb;
+use Sentry\ClientInterface;
+use Sentry\Event;
+use Sentry\NoOpClient;
+use Sentry\Options;
+use Sentry\State\BreadcrumbRecorder;
+use Sentry\State\GlobalScope;
+use Sentry\State\IsolationScope;
+
+final class BreadcrumbRecorderTest extends TestCase
+{
+    public function testRecordAddsBreadcrumbToGivenScope(): void
+    {
+        $breadcrumb = new Breadcrumb(Breadcrumb::LEVEL_ERROR, Breadcrumb::TYPE_ERROR, 'error_reporting');
+        $scope = new IsolationScope();
+        $otherScope = new IsolationScope();
+        $client = $this->createMock(ClientInterface::class);
+
+        $client->expects($this->once())
+            ->method('getOptions')
+            ->willReturn(new Options());
+
+        $this->assertTrue(BreadcrumbRecorder::record($client, $scope, $breadcrumb));
+        $this->assertScopeBreadcrumbs($scope, [$breadcrumb]);
+        $this->assertScopeBreadcrumbs($otherScope, []);
+    }
+
+    public function testRecordReturnsFalseForNoOpClient(): void
+    {
+        $scope = new IsolationScope();
+
+        $this->assertFalse(BreadcrumbRecorder::record(
+            new NoOpClient(),
+            $scope,
+            new Breadcrumb(Breadcrumb::LEVEL_ERROR, Breadcrumb::TYPE_ERROR, 'error_reporting')
+        ));
+        $this->assertScopeBreadcrumbs($scope, []);
+    }
+
+    public function testRecordReturnsFalseWhenMaxBreadcrumbsLimitIsZero(): void
+    {
+        $scope = new IsolationScope();
+        $client = $this->createMock(ClientInterface::class);
+
+        $client->expects($this->once())
+            ->method('getOptions')
+            ->willReturn(new Options(['max_breadcrumbs' => 0]));
+
+        $this->assertFalse(BreadcrumbRecorder::record(
+            $client,
+            $scope,
+            new Breadcrumb(Breadcrumb::LEVEL_ERROR, Breadcrumb::TYPE_ERROR, 'error_reporting')
+        ));
+        $this->assertScopeBreadcrumbs($scope, []);
+    }
+
+    public function testRecordReturnsFalseWhenBeforeBreadcrumbCallbackReturnsNull(): void
+    {
+        $scope = new IsolationScope();
+        $client = $this->createMock(ClientInterface::class);
+
+        $client->expects($this->once())
+            ->method('getOptions')
+            ->willReturn(new Options([
+                'before_breadcrumb' => static function () {
+                    return null;
+                },
+            ]));
+
+        $this->assertFalse(BreadcrumbRecorder::record(
+            $client,
+            $scope,
+            new Breadcrumb(Breadcrumb::LEVEL_ERROR, Breadcrumb::TYPE_ERROR, 'error_reporting')
+        ));
+        $this->assertScopeBreadcrumbs($scope, []);
+    }
+
+    public function testRecordStoresBreadcrumbReturnedByBeforeBreadcrumbCallback(): void
+    {
+        $breadcrumb1 = new Breadcrumb(Breadcrumb::LEVEL_ERROR, Breadcrumb::TYPE_ERROR, 'error_reporting');
+        $breadcrumb2 = new Breadcrumb(Breadcrumb::LEVEL_WARNING, Breadcrumb::TYPE_DEFAULT, 'custom');
+        $scope = new IsolationScope();
+        $client = $this->createMock(ClientInterface::class);
+
+        $client->expects($this->once())
+            ->method('getOptions')
+            ->willReturn(new Options([
+                'before_breadcrumb' => static function () use ($breadcrumb2): Breadcrumb {
+                    return $breadcrumb2;
+                },
+            ]));
+
+        $this->assertTrue(BreadcrumbRecorder::record($client, $scope, $breadcrumb1));
+        $this->assertScopeBreadcrumbs($scope, [$breadcrumb2]);
+    }
+
+    public function testRecordRespectsMaxBreadcrumbsLimit(): void
+    {
+        $breadcrumb1 = new Breadcrumb(Breadcrumb::LEVEL_INFO, Breadcrumb::TYPE_DEFAULT, 'one');
+        $breadcrumb2 = new Breadcrumb(Breadcrumb::LEVEL_INFO, Breadcrumb::TYPE_DEFAULT, 'two');
+        $breadcrumb3 = new Breadcrumb(Breadcrumb::LEVEL_INFO, Breadcrumb::TYPE_DEFAULT, 'three');
+        $scope = new IsolationScope();
+        $client = $this->createMock(ClientInterface::class);
+
+        $client->expects($this->exactly(3))
+            ->method('getOptions')
+            ->willReturn(new Options(['max_breadcrumbs' => 2]));
+
+        BreadcrumbRecorder::record($client, $scope, $breadcrumb1);
+        BreadcrumbRecorder::record($client, $scope, $breadcrumb2);
+        BreadcrumbRecorder::record($client, $scope, $breadcrumb3);
+
+        $this->assertScopeBreadcrumbs($scope, [$breadcrumb2, $breadcrumb3]);
+    }
+
+    /**
+     * @param Breadcrumb[] $expectedBreadcrumbs
+     */
+    private function assertScopeBreadcrumbs(IsolationScope $scope, array $expectedBreadcrumbs): void
+    {
+        $event = (new GlobalScope())->merge($scope)->applyToEvent(Event::createEvent());
+
+        $this->assertNotNull($event);
+        $this->assertSame($expectedBreadcrumbs, $event->getBreadcrumbs());
+    }
+}
diff --git a/tests/State/EventRecorderTest.php b/tests/State/EventRecorderTest.php
new file mode 100644
index 0000000000..b26d5b14bb
--- /dev/null
+++ b/tests/State/EventRecorderTest.php
@@ -0,0 +1,219 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Sentry\Tests\State;
+
+use PHPUnit\Framework\TestCase;
+use Sentry\CheckInStatus;
+use Sentry\ClientInterface;
+use Sentry\Event;
+use Sentry\EventHint;
+use Sentry\EventId;
+use Sentry\MonitorConfig;
+use Sentry\MonitorSchedule;
+use Sentry\NoOpClient;
+use Sentry\Options;
+use Sentry\SentrySdk;
+use Sentry\Severity;
+use Sentry\State\EventRecorder;
+use Sentry\State\IsolationScope;
+use Sentry\Util\SentryUid;
+
+final class EventRecorderTest extends TestCase
+{
+    public function testCaptureMessagePassesIsolationScopeAndStoresLastEventId(): void
+    {
+        $eventId = EventId::generate();
+        $hint = new EventHint();
+        $client = $this->createMock(ClientInterface::class);
+        $isolationScope = $this->setClientAndIsolationScope($client);
+
+        $client->expects($this->once())
+            ->method('captureMessage')
+            ->with('foo', Severity::debug(), $this->callback(function (IsolationScope $scope) use ($isolationScope): bool {
+                return $this->isCaptureScope($scope, $isolationScope);
+            }), $hint)
+            ->willReturn($eventId);
+
+        $this->assertSame($eventId, EventRecorder::captureMessage('foo', Severity::debug(), $hint, $isolationScope));
+        $this->assertSame($eventId, SentrySdk::getLastEventId());
+    }
+
+    public function testCaptureExceptionPassesIsolationScopeAndStoresLastEventId(): void
+    {
+        $eventId = EventId::generate();
+        $exception = new \RuntimeException('foo');
+        $hint = new EventHint();
+        $client = $this->createMock(ClientInterface::class);
+        $isolationScope = $this->setClientAndIsolationScope($client);
+
+        $client->expects($this->once())
+            ->method('captureException')
+            ->with($exception, $this->callback(function (IsolationScope $scope) use ($isolationScope): bool {
+                return $this->isCaptureScope($scope, $isolationScope);
+            }), $hint)
+            ->willReturn($eventId);
+
+        $this->assertSame($eventId, EventRecorder::captureException($exception, $hint, $isolationScope));
+        $this->assertSame($eventId, SentrySdk::getLastEventId());
+    }
+
+    public function testCaptureEventPassesIsolationScopeAndStoresLastEventId(): void
+    {
+        $event = Event::createEvent();
+        $hint = new EventHint();
+        $client = $this->createMock(ClientInterface::class);
+        $isolationScope = $this->setClientAndIsolationScope($client);
+
+        $client->expects($this->once())
+            ->method('captureEvent')
+            ->with($event, $hint, $this->callback(function (IsolationScope $scope) use ($isolationScope): bool {
+                return $this->isCaptureScope($scope, $isolationScope);
+            }))
+            ->willReturn($event->getId());
+
+        $this->assertSame($event->getId(), EventRecorder::captureEvent($event, $hint, $isolationScope));
+        $this->assertSame($event->getId(), SentrySdk::getLastEventId());
+    }
+
+    public function testCaptureLastErrorPassesIsolationScopeAndStoresLastEventId(): void
+    {
+        $eventId = EventId::generate();
+        $hint = new EventHint();
+        $client = $this->createMock(ClientInterface::class);
+        $isolationScope = $this->setClientAndIsolationScope($client);
+
+        $client->expects($this->once())
+            ->method('captureLastError')
+            ->with($this->callback(function (IsolationScope $scope) use ($isolationScope): bool {
+                return $this->isCaptureScope($scope, $isolationScope);
+            }), $hint)
+            ->willReturn($eventId);
+
+        $this->assertSame($eventId, EventRecorder::captureLastError($hint, $isolationScope));
+        $this->assertSame($eventId, SentrySdk::getLastEventId());
+    }
+
+    public function testCaptureEventClearsLastEventIdWhenClientReturnsNull(): void
+    {
+        $event = Event::createEvent();
+        $client = $this->createMock(ClientInterface::class);
+        $isolationScope = $this->setClientAndIsolationScope($client);
+        SentrySdk::getCurrentRuntimeContext()->setLastEventId(EventId::generate());
+
+        $client->expects($this->once())
+            ->method('captureEvent')
+            ->with($event, null, $this->callback(function (IsolationScope $scope) use ($isolationScope): bool {
+                return $this->isCaptureScope($scope, $isolationScope);
+            }))
+            ->willReturn(null);
+
+        $this->assertNull(EventRecorder::captureEvent($event));
+        $this->assertNull(SentrySdk::getLastEventId());
+    }
+
+    public function testCaptureCheckInCreatesEventAndStoresLastEventId(): void
+    {
+        $checkInId = SentryUid::generate();
+        $eventId = EventId::generate();
+        $monitorConfig = new MonitorConfig(
+            MonitorSchedule::crontab('*/5 * * * *'),
+            5,
+            30,
+            'UTC'
+        );
+        $client = $this->createMock(ClientInterface::class);
+        $isolationScope = $this->setClientAndIsolationScope($client);
+
+        $client->expects($this->once())
+            ->method('getOptions')
+            ->willReturn(new Options([
+                'environment' => Event::DEFAULT_ENVIRONMENT,
+                'release' => '1.0.0',
+            ]));
+        $client->expects($this->once())
+            ->method('captureEvent')
+            ->with($this->callback(static function (Event $event) use ($checkInId, $monitorConfig): bool {
+                $checkIn = $event->getCheckIn();
+
+                return $checkIn !== null
+                    && $checkIn->getId() === $checkInId
+                    && $checkIn->getMonitorSlug() === 'test-crontab'
+                    && $checkIn->getStatus() == CheckInStatus::ok()
+                    && $checkIn->getRelease() === '1.0.0'
+                    && $checkIn->getEnvironment() === Event::DEFAULT_ENVIRONMENT
+                    && $checkIn->getDuration() === 10
+                    && $checkIn->getMonitorConfig() === $monitorConfig;
+            }), null, $this->callback(function (IsolationScope $scope) use ($isolationScope): bool {
+                return $this->isCaptureScope($scope, $isolationScope);
+            }))
+            ->willReturn($eventId);
+
+        $this->assertSame($checkInId, EventRecorder::captureCheckIn(
+            'test-crontab',
+            CheckInStatus::ok(),
+            10,
+            $monitorConfig,
+            $checkInId,
+            $isolationScope
+        ));
+        $this->assertSame($eventId, SentrySdk::getLastEventId());
+    }
+
+    public function testCaptureCheckInReturnsNullForNoOpClient(): void
+    {
+        SentrySdk::init(new NoOpClient());
+        $eventId = EventId::generate();
+        SentrySdk::getCurrentRuntimeContext()->setLastEventId($eventId);
+
+        $this->assertNull(EventRecorder::captureCheckIn('test-crontab', CheckInStatus::ok()));
+        $this->assertSame($eventId, SentrySdk::getLastEventId());
+    }
+
+    public function testCaptureDoesNotClearLastEventIdForNoOpClient(): void
+    {
+        SentrySdk::init(new NoOpClient());
+        $eventId = EventId::generate();
+        SentrySdk::getCurrentRuntimeContext()->setLastEventId($eventId);
+
+        $this->assertNull(EventRecorder::captureMessage('foo'));
+        $this->assertNull(EventRecorder::captureException(new \RuntimeException('foo')));
+        $this->assertNull(EventRecorder::captureEvent(Event::createEvent()));
+        $this->assertNull(EventRecorder::captureLastError());
+        $this->assertSame($eventId, SentrySdk::getLastEventId());
+    }
+
+    private function setClientAndIsolationScope(ClientInterface $client): IsolationScope
+    {
+        SentrySdk::init();
+
+        SentrySdk::getGlobalScope()->clear();
+        SentrySdk::getGlobalScope()->setTag('scope', 'global');
+        SentrySdk::getGlobalScope()->setTag('global', 'yes');
+        SentrySdk::getGlobalScope()->setClient($client);
+
+        $scope = new IsolationScope();
+        $scope->setTag('scope', 'isolation');
+        $scope->setTag('isolation', 'yes');
+        SentrySdk::getCurrentRuntimeContext()->setIsolationScope($scope);
+
+        return $scope;
+    }
+
+    private function isCaptureScope(IsolationScope $captureScope, IsolationScope $isolationScope): bool
+    {
+        $this->assertSame($isolationScope, $captureScope);
+
+        $event = SentrySdk::getGlobalScope()->merge($captureScope)->applyToEvent(Event::createEvent());
+
+        $this->assertNotNull($event);
+        $this->assertSame([
+            'scope' => 'isolation',
+            'global' => 'yes',
+            'isolation' => 'yes',
+        ], $event->getTags());
+
+        return true;
+    }
+}
diff --git a/tests/State/HubAdapterTest.php b/tests/State/HubAdapterTest.php
deleted file mode 100644
index b07c0de26d..0000000000
--- a/tests/State/HubAdapterTest.php
+++ /dev/null
@@ -1,394 +0,0 @@
-<?php
-
-declare(strict_types=1);
-
-namespace Sentry\Tests\State;
-
-use PHPUnit\Framework\MockObject\MockObject;
-use PHPUnit\Framework\TestCase;
-use Sentry\Breadcrumb;
-use Sentry\CheckInStatus;
-use Sentry\ClientInterface;
-use Sentry\Event;
-use Sentry\EventHint;
-use Sentry\EventId;
-use Sentry\Integration\IntegrationInterface;
-use Sentry\MonitorConfig;
-use Sentry\MonitorSchedule;
-use Sentry\NoOpClient;
-use Sentry\Options;
-use Sentry\SentrySdk;
-use Sentry\Severity;
-use Sentry\State\Hub;
-use Sentry\State\HubAdapter;
-use Sentry\State\HubInterface;
-use Sentry\State\Scope;
-use Sentry\Tracing\Span;
-use Sentry\Tracing\Transaction;
-use Sentry\Tracing\TransactionContext;
-use Sentry\Util\SentryUid;
-
-final class HubAdapterTest extends TestCase
-{
-    public function testGetInstance(): void
-    {
-        $this->assertSame(HubAdapter::getInstance(), HubAdapter::getInstance());
-    }
-
-    public function testGetInstanceReturnsUncloneableInstance(): void
-    {
-        $this->expectException(\BadMethodCallException::class);
-        $this->expectExceptionMessage('Cloning is forbidden.');
-
-        clone HubAdapter::getInstance();
-    }
-
-    public function testHubAdapterThrowsExceptionOnSerialization(): void
-    {
-        $this->expectException(\BadMethodCallException::class);
-        $this->expectExceptionMessage('Serializing instances of this class is forbidden.');
-
-        serialize(HubAdapter::getInstance());
-    }
-
-    public function testHubAdapterThrowsExceptionOnUnserialization(): void
-    {
-        $this->expectException(\BadMethodCallException::class);
-        $this->expectExceptionMessage('Unserializing instances of this class is forbidden.');
-
-        unserialize('O:23:"Sentry\State\HubAdapter":0:{}');
-    }
-
-    public function testGetClient(): void
-    {
-        $client = $this->createMock(ClientInterface::class);
-
-        SentrySdk::getCurrentHub()->bindClient($client);
-
-        $this->assertSame($client, HubAdapter::getInstance()->getClient());
-    }
-
-    public function testGetLastEventId(): void
-    {
-        $eventId = EventId::generate();
-
-        $hub = $this->createMock(HubInterface::class);
-        $hub->expects($this->once())
-            ->method('getLastEventId')
-            ->willReturn($eventId);
-
-        SentrySdk::setCurrentHub($hub);
-
-        $this->assertSame($eventId, HubAdapter::getInstance()->getLastEventId());
-    }
-
-    public function testPushScope(): void
-    {
-        $scope = new Scope();
-
-        $hub = $this->createMock(HubInterface::class);
-        $hub->expects($this->once())
-            ->method('pushScope')
-            ->willReturn($scope);
-
-        SentrySdk::setCurrentHub($hub);
-
-        $this->assertSame($scope, HubAdapter::getInstance()->pushScope());
-    }
-
-    public function testPopScope(): void
-    {
-        $hub = $this->createMock(HubInterface::class);
-        $hub->expects($this->once())
-            ->method('popScope')
-            ->willReturn(true);
-
-        SentrySdk::setCurrentHub($hub);
-
-        $this->assertTrue(HubAdapter::getInstance()->popScope());
-    }
-
-    public function testWithScope(): void
-    {
-        $callback = static function (): string {
-            return 'foobarbaz';
-        };
-
-        $hub = $this->createMock(HubInterface::class);
-        $hub->expects($this->once())
-            ->method('withScope')
-            ->with($callback)
-            ->willReturnCallback($callback);
-
-        SentrySdk::setCurrentHub($hub);
-
-        $returnValue = HubAdapter::getInstance()->withScope($callback);
-
-        $this->assertSame('foobarbaz', $returnValue);
-    }
-
-    public function testConfigureScope(): void
-    {
-        $callback = static function () {};
-
-        $hub = $this->createMock(HubInterface::class);
-        $hub->expects($this->once())
-            ->method('configureScope')
-            ->with($callback);
-
-        SentrySdk::setCurrentHub($hub);
-        HubAdapter::getInstance()->configureScope($callback);
-    }
-
-    public function testBindClient(): void
-    {
-        $client = $this->createMock(ClientInterface::class);
-
-        $hub = $this->createMock(HubInterface::class);
-        $hub->expects($this->once())
-            ->method('bindClient')
-            ->with($client);
-
-        SentrySdk::setCurrentHub($hub);
-        HubAdapter::getInstance()->bindClient($client);
-    }
-
-    /**
-     * @dataProvider captureMessageDataProvider
-     */
-    public function testCaptureMessage(array $expectedFunctionCallArgs): void
-    {
-        $eventId = EventId::generate();
-
-        $hub = $this->createMock(HubInterface::class);
-        $hub->expects($this->once())
-            ->method('captureMessage')
-            ->with(...$expectedFunctionCallArgs)
-            ->willReturn($eventId);
-
-        SentrySdk::setCurrentHub($hub);
-
-        $this->assertSame($eventId, HubAdapter::getInstance()->captureMessage(...$expectedFunctionCallArgs));
-    }
-
-    public static function captureMessageDataProvider(): \Generator
-    {
-        yield [
-            [
-                'foo',
-                Severity::debug(),
-            ],
-        ];
-
-        yield [
-            [
-                'foo',
-                Severity::debug(),
-                new EventHint(),
-            ],
-        ];
-    }
-
-    /**
-     * @dataProvider captureExceptionDataProvider
-     */
-    public function testCaptureException(array $expectedFunctionCallArgs): void
-    {
-        $eventId = EventId::generate();
-        $exception = new \Exception();
-
-        $hub = $this->createMock(HubInterface::class);
-        $hub->expects($this->once())
-            ->method('captureException')
-            ->with(...$expectedFunctionCallArgs)
-            ->willReturn($eventId);
-
-        SentrySdk::setCurrentHub($hub);
-
-        $this->assertSame($eventId, HubAdapter::getInstance()->captureException(...$expectedFunctionCallArgs));
-    }
-
-    public static function captureExceptionDataProvider(): \Generator
-    {
-        yield [
-            [
-                new \Exception('foo'),
-            ],
-        ];
-
-        yield [
-            [
-                new \Exception('foo'),
-                new EventHint(),
-            ],
-        ];
-    }
-
-    public function testCaptureEvent(): void
-    {
-        $event = Event::createEvent();
-        $hint = EventHint::fromArray([]);
-
-        $hub = $this->createMock(HubInterface::class);
-        $hub->expects($this->once())
-            ->method('captureEvent')
-            ->with($event, $hint)
-            ->willReturn($event->getId());
-
-        SentrySdk::setCurrentHub($hub);
-
-        $this->assertSame($event->getId(), HubAdapter::getInstance()->captureEvent($event, $hint));
-    }
-
-    /**
-     * @dataProvider captureLastErrorDataProvider
-     */
-    public function testCaptureLastError(array $expectedFunctionCallArgs): void
-    {
-        $eventId = EventId::generate();
-
-        $hub = $this->createMock(HubInterface::class);
-        $hub->expects($this->once())
-            ->method('captureLastError')
-            ->with(...$expectedFunctionCallArgs)
-            ->willReturn($eventId);
-
-        SentrySdk::setCurrentHub($hub);
-
-        $this->assertSame($eventId, HubAdapter::getInstance()->captureLastError(...$expectedFunctionCallArgs));
-    }
-
-    public static function captureLastErrorDataProvider(): \Generator
-    {
-        yield [
-            [],
-        ];
-
-        yield [
-            [
-                new EventHint(),
-            ],
-        ];
-    }
-
-    public function testCaptureCheckIn(): void
-    {
-        $hub = new Hub(new NoOpClient());
-
-        $options = new Options([
-            'environment' => Event::DEFAULT_ENVIRONMENT,
-            'release' => '1.1.8',
-        ]);
-        /** @var ClientInterface&MockObject $client */
-        $client = $this->createMock(ClientInterface::class);
-        $client->expects($this->once())
-            ->method('getOptions')
-            ->willReturn($options);
-
-        $hub->bindClient($client);
-        SentrySdk::setCurrentHub($hub);
-
-        $checkInId = SentryUid::generate();
-
-        $this->assertSame($checkInId, HubAdapter::getInstance()->captureCheckIn(
-            'test-crontab',
-            CheckInStatus::ok(),
-            10,
-            new MonitorConfig(
-                MonitorSchedule::crontab('*/5 * * * *'),
-                5,
-                30,
-                'UTC'
-            ),
-            $checkInId
-        ));
-    }
-
-    public function testAddBreadcrumb(): void
-    {
-        $breadcrumb = new Breadcrumb(Breadcrumb::LEVEL_DEBUG, Breadcrumb::TYPE_ERROR, 'user');
-
-        $hub = $this->createMock(HubInterface::class);
-        $hub->expects($this->once())
-            ->method('addBreadcrumb')
-            ->willReturn(true);
-
-        SentrySdk::setCurrentHub($hub);
-
-        $this->assertTrue(HubAdapter::getInstance()->addBreadcrumb($breadcrumb));
-    }
-
-    public function testGetIntegration(): void
-    {
-        $integration = $this->createMock(IntegrationInterface::class);
-
-        $hub = $this->createMock(HubInterface::class);
-        $hub->expects($this->once())
-            ->method('getIntegration')
-            ->with(\get_class($integration))
-            ->willReturn($integration);
-
-        SentrySdk::setCurrentHub($hub);
-
-        $this->assertSame($integration, HubAdapter::getInstance()->getIntegration(\get_class($integration)));
-    }
-
-    public function testStartTransaction(): void
-    {
-        $transactionContext = new TransactionContext();
-        $transaction = new Transaction($transactionContext);
-
-        $hub = $this->createMock(HubInterface::class);
-        $hub->expects($this->once())
-            ->method('startTransaction')
-            ->with($transactionContext)
-            ->willReturn($transaction);
-
-        SentrySdk::setCurrentHub($hub);
-
-        $this->assertSame($transaction, HubAdapter::getInstance()->startTransaction($transactionContext));
-    }
-
-    public function testGetTransaction(): void
-    {
-        $transaction = new Transaction(new TransactionContext());
-
-        $hub = $this->createMock(HubInterface::class);
-        $hub->expects($this->once())
-            ->method('getTransaction')
-            ->willReturn($transaction);
-
-        SentrySdk::setCurrentHub($hub);
-
-        $this->assertSame($transaction, HubAdapter::getInstance()->getTransaction());
-    }
-
-    public function testGetSpan(): void
-    {
-        $span = new Span();
-
-        $hub = $this->createMock(HubInterface::class);
-        $hub->expects($this->once())
-            ->method('getSpan')
-            ->willReturn($span);
-
-        SentrySdk::setCurrentHub($hub);
-
-        $this->assertSame($span, HubAdapter::getInstance()->getSpan());
-    }
-
-    public function testSetSpan(): void
-    {
-        $span = new Span();
-
-        $hub = $this->createMock(HubInterface::class);
-        $hub->expects($this->once())
-            ->method('setSpan')
-            ->with($span)
-            ->willReturn($hub);
-
-        SentrySdk::setCurrentHub($hub);
-
-        $this->assertSame($hub, HubAdapter::getInstance()->setSpan($span));
-    }
-}
diff --git a/tests/State/HubTest.php b/tests/State/HubTest.php
deleted file mode 100644
index 972ce617e7..0000000000
--- a/tests/State/HubTest.php
+++ /dev/null
@@ -1,1055 +0,0 @@
-<?php
-
-declare(strict_types=1);
-
-namespace Sentry\Tests\State;
-
-use PHPUnit\Framework\MockObject\MockObject;
-use PHPUnit\Framework\TestCase;
-use Sentry\Breadcrumb;
-use Sentry\CheckIn;
-use Sentry\CheckInStatus;
-use Sentry\ClientInterface;
-use Sentry\Event;
-use Sentry\EventHint;
-use Sentry\EventId;
-use Sentry\Integration\IntegrationInterface;
-use Sentry\MonitorConfig;
-use Sentry\MonitorSchedule;
-use Sentry\NoOpClient;
-use Sentry\Options;
-use Sentry\Severity;
-use Sentry\State\Hub;
-use Sentry\State\Scope;
-use Sentry\Tracing\DynamicSamplingContext;
-use Sentry\Tracing\PropagationContext;
-use Sentry\Tracing\SamplingContext;
-use Sentry\Tracing\TransactionContext;
-use Sentry\Tracing\TransactionMetadata;
-use Sentry\Util\SentryUid;
-
-final class HubTest extends TestCase
-{
-    public function testGetClient(): void
-    {
-        /** @var ClientInterface&MockObject $client */
-        $client = $this->createMock(ClientInterface::class);
-        $hub = new Hub($client);
-
-        $this->assertSame($client, $hub->getClient());
-    }
-
-    public function testGetScope(): void
-    {
-        $callbackInvoked = false;
-        $scope = new Scope();
-        $hub = new Hub($this->createMock(ClientInterface::class), $scope);
-
-        $hub->configureScope(function (Scope $scopeArg) use (&$callbackInvoked, $scope) {
-            $this->assertSame($scope, $scopeArg);
-
-            $callbackInvoked = true;
-        });
-
-        $this->assertTrue($callbackInvoked);
-    }
-
-    public function testGetLastEventId(): void
-    {
-        $eventId = EventId::generate();
-
-        /** @var ClientInterface&MockObject $client */
-        $client = $this->createMock(ClientInterface::class);
-        $client->expects($this->once())
-            ->method('captureMessage')
-            ->willReturn($eventId);
-
-        $hub = new Hub($client);
-
-        $this->assertNull($hub->getLastEventId());
-        $this->assertSame($hub->captureMessage('foo'), $hub->getLastEventId());
-        $this->assertSame($eventId, $hub->getLastEventId());
-    }
-
-    public function testPushScope(): void
-    {
-        /** @var ClientInterface&MockObject $client1 */
-        $client1 = $this->createMock(ClientInterface::class);
-        $scope1 = new Scope();
-        $hub = new Hub($client1, $scope1);
-
-        $this->assertSame($client1, $hub->getClient());
-
-        $scope2 = $hub->pushScope();
-
-        $this->assertSame($client1, $hub->getClient());
-        $this->assertNotSame($scope1, $scope2);
-
-        $hub->configureScope(function (Scope $scopeArg) use (&$callbackInvoked, $scope2): void {
-            $this->assertSame($scope2, $scopeArg);
-
-            $callbackInvoked = true;
-        });
-
-        $this->assertTrue($callbackInvoked);
-    }
-
-    public function testPopScope(): void
-    {
-        /** @var ClientInterface&MockObject $client */
-        $client = $this->createMock(ClientInterface::class);
-        $scope1 = new Scope();
-        $hub = new Hub($client, $scope1);
-
-        $this->assertFalse($hub->popScope());
-
-        $scope2 = $hub->pushScope();
-
-        $callbackInvoked = false;
-
-        $hub->configureScope(function (Scope $scopeArg) use ($scope2, &$callbackInvoked): void {
-            $this->assertSame($scope2, $scopeArg);
-
-            $callbackInvoked = true;
-        });
-
-        $this->assertTrue($callbackInvoked);
-        $this->assertSame($client, $hub->getClient());
-
-        $this->assertTrue($hub->popScope());
-
-        $callbackInvoked = false;
-
-        $hub->configureScope(function (Scope $scopeArg) use ($scope1, &$callbackInvoked): void {
-            $this->assertSame($scope1, $scopeArg);
-
-            $callbackInvoked = true;
-        });
-
-        $this->assertTrue($callbackInvoked);
-        $this->assertSame($client, $hub->getClient());
-
-        $this->assertFalse($hub->popScope());
-
-        $callbackInvoked = false;
-
-        $hub->configureScope(function (Scope $scopeArg) use ($scope1, &$callbackInvoked): void {
-            $this->assertSame($scope1, $scopeArg);
-
-            $callbackInvoked = true;
-        });
-
-        $this->assertTrue($callbackInvoked);
-        $this->assertSame($client, $hub->getClient());
-    }
-
-    public function testWithScope(): void
-    {
-        $scope = new Scope();
-        $hub = new Hub(new NoOpClient(), $scope);
-
-        $callbackReturn = $hub->withScope(function (Scope $scopeArg) use ($scope): string {
-            $this->assertNotSame($scope, $scopeArg);
-
-            return 'foobarbaz';
-        });
-
-        $this->assertSame('foobarbaz', $callbackReturn);
-
-        $callbackInvoked = false;
-
-        $hub->configureScope(function (Scope $scopeArg) use (&$callbackInvoked, $scope): void {
-            $this->assertSame($scope, $scopeArg);
-
-            $callbackInvoked = true;
-        });
-
-        $this->assertTrue($callbackInvoked);
-    }
-
-    public function testWithScopeWhenExceptionIsThrown(): void
-    {
-        $scope = new Scope();
-        $hub = new Hub($this->createMock(ClientInterface::class), $scope);
-        $callbackInvoked = false;
-
-        try {
-            $hub->withScope(function (Scope $scopeArg) use ($scope, &$callbackInvoked): void {
-                $this->assertNotSame($scope, $scopeArg);
-
-                $callbackInvoked = true;
-
-                // We throw to test that the scope is correctly popped form the
-                // stack regardless
-                throw new \RuntimeException();
-            });
-        } catch (\RuntimeException $exception) {
-            // Do nothing, we catch this exception to not make the test fail
-        }
-
-        $this->assertTrue($callbackInvoked);
-
-        $callbackInvoked = false;
-
-        $hub->configureScope(function (Scope $scopeArg) use (&$callbackInvoked, $scope): void {
-            $this->assertSame($scope, $scopeArg);
-
-            $callbackInvoked = true;
-        });
-
-        $this->assertTrue($callbackInvoked);
-    }
-
-    public function testConfigureScope(): void
-    {
-        $scope = new Scope();
-        $hub = new Hub(new NoOpClient(), $scope);
-
-        $callbackInvoked = false;
-
-        $hub->configureScope(function (Scope $scopeArg) use ($scope, &$callbackInvoked): void {
-            $this->assertSame($scope, $scopeArg);
-
-            $callbackInvoked = true;
-        });
-
-        $this->assertTrue($callbackInvoked);
-    }
-
-    public function testBindClient(): void
-    {
-        /** @var ClientInterface&MockObject $client1 */
-        $client1 = $this->createMock(ClientInterface::class);
-
-        /** @var ClientInterface&MockObject $client2 */
-        $client2 = $this->createMock(ClientInterface::class);
-
-        $hub = new Hub($client1);
-
-        $this->assertSame($client1, $hub->getClient());
-
-        $hub->bindClient($client2);
-
-        $this->assertSame($client2, $hub->getClient());
-    }
-
-    /**
-     * @dataProvider captureMessageDataProvider
-     */
-    public function testCaptureMessage(array $functionCallArgs, array $expectedFunctionCallArgs, PropagationContext $propagationContext): void
-    {
-        $eventId = EventId::generate();
-        $hub = new Hub(new NoOpClient());
-
-        $hub->configureScope(static function (Scope $scope) use ($propagationContext): void {
-            $scope->setPropagationContext($propagationContext);
-        });
-
-        /** @var ClientInterface&MockObject $client */
-        $client = $this->createMock(ClientInterface::class);
-        $client->expects($this->once())
-            ->method('captureMessage')
-            ->with(...$expectedFunctionCallArgs)
-            ->willReturn($eventId);
-
-        $this->assertNull($hub->captureMessage('foo'));
-
-        $hub->bindClient($client);
-
-        $this->assertSame($eventId, $hub->captureMessage(...$functionCallArgs));
-    }
-
-    public static function captureMessageDataProvider(): \Generator
-    {
-        $propagationContext = PropagationContext::fromDefaults();
-
-        yield [
-            [
-                'foo',
-                Severity::debug(),
-            ],
-            [
-                'foo',
-                Severity::debug(),
-                new Scope($propagationContext),
-            ],
-            $propagationContext,
-        ];
-
-        yield [
-            [
-                'foo',
-                Severity::debug(),
-                new EventHint(),
-            ],
-            [
-                'foo',
-                Severity::debug(),
-                new Scope($propagationContext),
-                new EventHint(),
-            ],
-            $propagationContext,
-        ];
-    }
-
-    /**
-     * @dataProvider captureExceptionDataProvider
-     */
-    public function testCaptureException(array $functionCallArgs, array $expectedFunctionCallArgs, PropagationContext $propagationContext): void
-    {
-        $eventId = EventId::generate();
-        $hub = new Hub(new NoOpClient());
-
-        $hub->configureScope(static function (Scope $scope) use ($propagationContext): void {
-            $scope->setPropagationContext($propagationContext);
-        });
-
-        $client = $this->createMock(ClientInterface::class);
-        $client->expects($this->once())
-            ->method('captureException')
-            ->with(...$expectedFunctionCallArgs)
-            ->willReturn($eventId);
-
-        $this->assertNull($hub->captureException(new \RuntimeException()));
-
-        $hub->bindClient($client);
-
-        $this->assertSame($eventId, $hub->captureException(...$functionCallArgs));
-    }
-
-    public static function captureExceptionDataProvider(): \Generator
-    {
-        $propagationContext = PropagationContext::fromDefaults();
-
-        yield [
-            [
-                new \Exception('foo'),
-            ],
-            [
-                new \Exception('foo'),
-                new Scope($propagationContext),
-                null,
-            ],
-            $propagationContext,
-        ];
-
-        yield [
-            [
-                new \Exception('foo'),
-                new EventHint(),
-            ],
-            [
-                new \Exception('foo'),
-                new Scope($propagationContext),
-                new EventHint(),
-            ],
-            $propagationContext,
-        ];
-    }
-
-    /**
-     * @dataProvider captureLastErrorDataProvider
-     */
-    public function testCaptureLastError(array $functionCallArgs, array $expectedFunctionCallArgs, PropagationContext $propagationContext): void
-    {
-        $eventId = EventId::generate();
-        $hub = new Hub(new NoOpClient());
-
-        $hub->configureScope(static function (Scope $scope) use ($propagationContext): void {
-            $scope->setPropagationContext($propagationContext);
-        });
-
-        /** @var ClientInterface&MockObject $client */
-        $client = $this->createMock(ClientInterface::class);
-        $client->expects($this->once())
-            ->method('captureLastError')
-            ->with(...$expectedFunctionCallArgs)
-            ->willReturn($eventId);
-
-        $this->assertNull($hub->captureLastError(...$functionCallArgs));
-
-        $hub->bindClient($client);
-
-        $this->assertSame($eventId, $hub->captureLastError(...$functionCallArgs));
-    }
-
-    public static function captureLastErrorDataProvider(): \Generator
-    {
-        $propagationContext = PropagationContext::fromDefaults();
-
-        yield [
-            [],
-            [
-                new Scope($propagationContext),
-                null,
-            ],
-            $propagationContext,
-        ];
-
-        yield [
-            [
-                new EventHint(),
-            ],
-            [
-                new Scope($propagationContext),
-                new EventHint(),
-            ],
-            $propagationContext,
-        ];
-    }
-
-    public function testCaptureCheckIn(): void
-    {
-        $expectedCheckIn = new CheckIn(
-            'test-crontab',
-            CheckInStatus::ok(),
-            SentryUid::generate(),
-            '0.0.1-dev',
-            Event::DEFAULT_ENVIRONMENT,
-            10,
-            new MonitorConfig(
-                MonitorSchedule::crontab('*/5 * * * *'),
-                5,
-                30,
-                'UTC'
-            )
-        );
-
-        /** @var ClientInterface&MockObject $client */
-        $client = $this->createMock(ClientInterface::class);
-        $client->expects($this->once())
-            ->method('getOptions')
-            ->willReturn(new Options([
-                'environment' => Event::DEFAULT_ENVIRONMENT,
-                'release' => '0.0.1-dev',
-            ]));
-
-        $client->expects($this->once())
-            ->method('captureEvent')
-            ->with($this->callback(static function (Event $event) use ($expectedCheckIn): bool {
-                return $event->getCheckIn() == $expectedCheckIn;
-            }));
-
-        $hub = new Hub($client);
-
-        $this->assertSame($expectedCheckIn->getId(), $hub->captureCheckIn(
-            $expectedCheckIn->getMonitorSlug(),
-            $expectedCheckIn->getStatus(),
-            $expectedCheckIn->getDuration(),
-            $expectedCheckIn->getMonitorConfig(),
-            $expectedCheckIn->getId()
-        ));
-    }
-
-    public function testCaptureEvent(): void
-    {
-        $hub = new Hub(new NoOpClient());
-        $event = Event::createEvent();
-
-        /** @var ClientInterface&MockObject $client */
-        $client = $this->createMock(ClientInterface::class);
-        $client->expects($this->once())
-            ->method('captureEvent')
-            ->with($event)
-            ->willReturn($event->getId());
-
-        $this->assertNull($hub->captureEvent($event));
-
-        $hub->bindClient($client);
-
-        $this->assertSame($event->getId(), $hub->captureEvent($event));
-    }
-
-    public function testAddBreadcrumb(): void
-    {
-        /** @var ClientInterface&MockObject $client */
-        $client = $this->createMock(ClientInterface::class);
-        $client->expects($this->once())
-            ->method('getOptions')
-            ->willReturn(new Options());
-
-        $callbackInvoked = false;
-        $hub = new Hub(new NoOpClient());
-        $breadcrumb = new Breadcrumb(Breadcrumb::LEVEL_ERROR, Breadcrumb::TYPE_ERROR, 'error_reporting');
-
-        $hub->addBreadcrumb($breadcrumb);
-        $hub->configureScope(function (Scope $scope): void {
-            $event = $scope->applyToEvent(Event::createEvent());
-
-            $this->assertNotNull($event);
-            $this->assertEmpty($event->getBreadcrumbs());
-        });
-
-        $hub->bindClient($client);
-        $hub->addBreadcrumb($breadcrumb);
-        $hub->configureScope(function (Scope $scope) use (&$callbackInvoked, $breadcrumb): void {
-            $event = $scope->applyToEvent(Event::createEvent());
-
-            $this->assertNotNull($event);
-            $this->assertSame([$breadcrumb], $event->getBreadcrumbs());
-
-            $callbackInvoked = true;
-        });
-
-        $this->assertTrue($callbackInvoked);
-    }
-
-    public function testAddBreadcrumbDoesNothingIfMaxBreadcrumbsLimitIsZero(): void
-    {
-        /** @var ClientInterface&MockObject $client */
-        $client = $this->createMock(ClientInterface::class);
-        $client->expects($this->once())
-            ->method('getOptions')
-            ->willReturn(new Options(['max_breadcrumbs' => 0]));
-
-        $hub = new Hub($client);
-
-        $hub->addBreadcrumb(new Breadcrumb(Breadcrumb::LEVEL_ERROR, Breadcrumb::TYPE_ERROR, 'error_reporting'));
-        $hub->configureScope(function (Scope $scope): void {
-            $event = $scope->applyToEvent(Event::createEvent());
-
-            $this->assertNotNull($event);
-            $this->assertEmpty($event->getBreadcrumbs());
-        });
-    }
-
-    public function testAddBreadcrumbRespectsMaxBreadcrumbsLimit(): void
-    {
-        /** @var ClientInterface&MockObject $client */
-        $client = $this->createMock(ClientInterface::class);
-        $client->expects($this->any())
-            ->method('getOptions')
-            ->willReturn(new Options(['max_breadcrumbs' => 2]));
-
-        $hub = new Hub($client);
-        $breadcrumb1 = new Breadcrumb(Breadcrumb::LEVEL_WARNING, Breadcrumb::TYPE_ERROR, 'error_reporting', 'foo');
-        $breadcrumb2 = new Breadcrumb(Breadcrumb::LEVEL_WARNING, Breadcrumb::TYPE_ERROR, 'error_reporting', 'bar');
-        $breadcrumb3 = new Breadcrumb(Breadcrumb::LEVEL_WARNING, Breadcrumb::TYPE_ERROR, 'error_reporting', 'baz');
-
-        $hub->addBreadcrumb($breadcrumb1);
-        $hub->addBreadcrumb($breadcrumb2);
-
-        $hub->configureScope(function (Scope $scope) use ($breadcrumb1, $breadcrumb2): void {
-            $event = $scope->applyToEvent(Event::createEvent());
-
-            $this->assertNotNull($event);
-            $this->assertSame([$breadcrumb1, $breadcrumb2], $event->getBreadcrumbs());
-        });
-
-        $hub->addBreadcrumb($breadcrumb3);
-
-        $hub->configureScope(function (Scope $scope) use ($breadcrumb2, $breadcrumb3): void {
-            $event = $scope->applyToEvent(Event::createEvent());
-
-            $this->assertNotNull($event);
-            $this->assertSame([$breadcrumb2, $breadcrumb3], $event->getBreadcrumbs());
-        });
-    }
-
-    public function testAddBreadcrumbDoesNothingWhenBeforeBreadcrumbCallbackReturnsNull(): void
-    {
-        /** @var ClientInterface&MockObject $client */
-        $client = $this->createMock(ClientInterface::class);
-        $client->expects($this->once())
-            ->method('getOptions')
-            ->willReturn(new Options([
-                'before_breadcrumb' => static function () {
-                    return null;
-                },
-            ]));
-
-        $hub = new Hub($client);
-
-        $hub->addBreadcrumb(new Breadcrumb(Breadcrumb::LEVEL_ERROR, Breadcrumb::TYPE_ERROR, 'error_reporting'));
-        $hub->configureScope(function (Scope $scope): void {
-            $event = $scope->applyToEvent(Event::createEvent());
-
-            $this->assertNotNull($event);
-            $this->assertEmpty($event->getBreadcrumbs());
-        });
-    }
-
-    public function testAddBreadcrumbStoresBreadcrumbReturnedByBeforeBreadcrumbCallback(): void
-    {
-        $callbackInvoked = false;
-        $breadcrumb1 = new Breadcrumb(Breadcrumb::LEVEL_ERROR, Breadcrumb::TYPE_ERROR, 'error_reporting');
-        $breadcrumb2 = new Breadcrumb(Breadcrumb::LEVEL_ERROR, Breadcrumb::TYPE_ERROR, 'error_reporting');
-
-        /** @var ClientInterface&MockObject $client */
-        $client = $this->createMock(ClientInterface::class);
-        $client->expects($this->once())
-            ->method('getOptions')
-            ->willReturn(new Options([
-                'before_breadcrumb' => static function () use ($breadcrumb2): Breadcrumb {
-                    return $breadcrumb2;
-                },
-            ]));
-
-        $hub = new Hub($client);
-
-        $hub->addBreadcrumb($breadcrumb1);
-        $hub->configureScope(function (Scope $scope) use (&$callbackInvoked, $breadcrumb2): void {
-            $event = $scope->applyToEvent(Event::createEvent());
-
-            $this->assertNotNull($event);
-            $this->assertSame([$breadcrumb2], $event->getBreadcrumbs());
-
-            $callbackInvoked = true;
-        });
-
-        $this->assertTrue($callbackInvoked);
-    }
-
-    public function testGetIntegration(): void
-    {
-        /** @var IntegrationInterface&MockObject $integration */
-        $integration = $this->createMock(IntegrationInterface::class);
-
-        /** @var ClientInterface&MockObject $client */
-        $client = $this->createMock(ClientInterface::class);
-        $client->expects($this->once())
-            ->method('getIntegration')
-            ->with('Foo\\Bar')
-            ->willReturn($integration);
-
-        $hub = new Hub(new NoOpClient());
-
-        $this->assertNull($hub->getIntegration('Foo\\Bar'));
-
-        $hub->bindClient($client);
-
-        $this->assertSame($integration, $hub->getIntegration('Foo\\Bar'));
-    }
-
-    /**
-     * @dataProvider startTransactionDataProvider
-     */
-    public function testStartTransactionWithTracesSampler(Options $options, TransactionContext $transactionContext, bool $expectedSampled): void
-    {
-        $client = $this->createMock(ClientInterface::class);
-        $client->expects($this->once())
-            ->method('getOptions')
-            ->willReturn($options);
-
-        $hub = new Hub($client);
-        $transaction = $hub->startTransaction($transactionContext);
-
-        $this->assertSame($expectedSampled, $transaction->getSampled());
-    }
-
-    public function testStartTransactionIgnoresBaggageSampleRateWithoutSentryTrace(): void
-    {
-        $client = $this->createMock(ClientInterface::class);
-        $client->expects($this->once())
-            ->method('getOptions')
-            ->willReturn(new Options([
-                'traces_sample_rate' => 0.0,
-            ]));
-
-        $hub = new Hub($client);
-        $transactionContext = TransactionContext::fromHeaders('', 'sentry-sample_rate=1');
-        $transaction = $hub->startTransaction($transactionContext);
-
-        $this->assertFalse($transaction->getSampled());
-    }
-
-    public static function startTransactionDataProvider(): iterable
-    {
-        yield 'Acceptable float value returned from traces_sampler' => [
-            new Options([
-                'traces_sampler' => static function (): float {
-                    return 1.0;
-                },
-            ]),
-            new TransactionContext(),
-            true,
-        ];
-
-        yield 'Acceptable but too low float value returned from traces_sampler' => [
-            new Options([
-                'traces_sampler' => static function (): float {
-                    return 0.0;
-                },
-            ]),
-            new TransactionContext(),
-            false,
-        ];
-
-        yield 'Acceptable integer value returned from traces_sampler' => [
-            new Options([
-                'traces_sampler' => static function (): int {
-                    return 1;
-                },
-            ]),
-            new TransactionContext(),
-            true,
-        ];
-
-        yield 'Acceptable but too low integer value returned from traces_sampler' => [
-            new Options([
-                'traces_sampler' => static function (): int {
-                    return 0;
-                },
-            ]),
-            new TransactionContext(),
-            false,
-        ];
-
-        yield 'Acceptable float value returned from traces_sample_rate' => [
-            new Options([
-                'traces_sample_rate' => 1.0,
-            ]),
-            new TransactionContext(),
-            true,
-        ];
-
-        yield 'Acceptable but too low float value returned from traces_sample_rate' => [
-            new Options([
-                'traces_sample_rate' => 0.0,
-            ]),
-            new TransactionContext(),
-            false,
-        ];
-
-        yield 'Acceptable integer value returned from traces_sample_rate' => [
-            new Options([
-                'traces_sample_rate' => 1,
-            ]),
-            new TransactionContext(),
-            true,
-        ];
-
-        yield 'Acceptable but too low integer value returned from traces_sample_rate' => [
-            new Options([
-                'traces_sample_rate' => 0,
-            ]),
-            new TransactionContext(),
-            false,
-        ];
-
-        yield 'Acceptable but too low value returned from traces_sample_rate which is preferred over sample_rate' => [
-            new Options([
-                'sample_rate' => 1.0,
-                'traces_sample_rate' => 0.0,
-            ]),
-            new TransactionContext(),
-            false,
-        ];
-
-        yield 'Acceptable value returned from traces_sample_rate which is preferred over sample_rate' => [
-            new Options([
-                'sample_rate' => 0.0,
-                'traces_sample_rate' => 1.0,
-            ]),
-            new TransactionContext(),
-            true,
-        ];
-
-        yield 'Acceptable value returned from SamplingContext::getParentSampled() which is preferred over traces_sample_rate (x1)' => [
-            new Options([
-                'traces_sample_rate' => 0.5,
-            ]),
-            new TransactionContext(TransactionContext::DEFAULT_NAME, true),
-            true,
-        ];
-
-        yield 'Acceptable value returned from SamplingContext::getParentSampled() which is preferred over traces_sample_rate (x2)' => [
-            new Options([
-                'traces_sample_rate' => 1.0,
-            ]),
-            new TransactionContext(TransactionContext::DEFAULT_NAME, false),
-            false,
-        ];
-
-        yield 'Invalid incoming sample_rand is ignored' => [
-            new Options([
-                'traces_sample_rate' => 1.0,
-            ]),
-            TransactionContext::fromHeaders(
-                '566e3688a61d4bc888951642d6f14a19-566e3688a61d4bc8',
-                'sentry-sample_rand=2.0'
-            ),
-            true,
-        ];
-
-        yield 'Out of range sample rate returned from traces_sampler (lower than minimum)' => [
-            new Options([
-                'traces_sampler' => static function (): float {
-                    return -1.0;
-                },
-            ]),
-            new TransactionContext(TransactionContext::DEFAULT_NAME, false),
-            false,
-        ];
-
-        yield 'Out of range sample rate returned from traces_sampler (greater than maximum)' => [
-            new Options([
-                'traces_sampler' => static function (): float {
-                    return 1.1;
-                },
-            ]),
-            new TransactionContext(TransactionContext::DEFAULT_NAME, false),
-            false,
-        ];
-
-        yield 'Invalid type returned from traces_sampler' => [
-            new Options([
-                'traces_sampler' => static function (): string {
-                    return 'foo';
-                },
-            ]),
-            new TransactionContext(TransactionContext::DEFAULT_NAME, false),
-            false,
-        ];
-    }
-
-    public function testStartTransactionDoesNothingIfTracingIsNotEnabled(): void
-    {
-        $client = $this->createMock(ClientInterface::class);
-        $client->expects($this->once())
-            ->method('getOptions')
-            ->willReturn(new Options());
-
-        $hub = new Hub($client);
-        $transaction = $hub->startTransaction(new TransactionContext());
-
-        $this->assertFalse($transaction->getSampled());
-    }
-
-    public function testStartTransactionWithCustomSamplingContext(): void
-    {
-        $customSamplingContext = ['a' => 'b'];
-
-        $client = $this->createMock(ClientInterface::class);
-        $client->expects($this->once())
-            ->method('getOptions')
-            ->willReturn(new Options([
-                'traces_sampler' => function (SamplingContext $samplingContext) use ($customSamplingContext): float {
-                    $this->assertSame($samplingContext->getAdditionalContext(), $customSamplingContext);
-
-                    return 1.0;
-                },
-            ]));
-
-        $hub = new Hub($client);
-        $hub->startTransaction(new TransactionContext(), $customSamplingContext);
-    }
-
-    public function testStartTransactionStartsProfilerWithProfilesSampler(): void
-    {
-        $client = $this->createMock(ClientInterface::class);
-        $client->expects($this->exactly(2))
-            ->method('getOptions')
-            ->willReturn(new Options([
-                'traces_sample_rate' => 1.0,
-                'profiles_sampler' => static function (): float {
-                    return 1.0;
-                },
-            ]));
-
-        $hub = new Hub($client);
-        $transaction = $hub->startTransaction(new TransactionContext());
-
-        $this->assertTrue($transaction->getSampled());
-        $this->assertNotNull($transaction->getProfiler());
-    }
-
-    public function testStartTransactionDoesNotStartProfilerWhenProfilesSamplerReturnsZero(): void
-    {
-        $client = $this->createMock(ClientInterface::class);
-        $client->expects($this->once())
-            ->method('getOptions')
-            ->willReturn(new Options([
-                'traces_sample_rate' => 1.0,
-                'profiles_sampler' => static function (): float {
-                    return 0.0;
-                },
-            ]));
-
-        $hub = new Hub($client);
-        $transaction = $hub->startTransaction(new TransactionContext());
-
-        $this->assertTrue($transaction->getSampled());
-        $this->assertNull($transaction->getProfiler());
-    }
-
-    public function testStartTransactionPrefersProfilesSamplerOverProfilesSampleRate(): void
-    {
-        $client = $this->createMock(ClientInterface::class);
-        $client->expects($this->once())
-            ->method('getOptions')
-            ->willReturn(new Options([
-                'traces_sample_rate' => 1.0,
-                'profiles_sample_rate' => 1.0,
-                'profiles_sampler' => static function (): float {
-                    return 0.0;
-                },
-            ]));
-
-        $hub = new Hub($client);
-        $transaction = $hub->startTransaction(new TransactionContext());
-
-        $this->assertTrue($transaction->getSampled());
-        $this->assertNull($transaction->getProfiler());
-    }
-
-    public function testStartTransactionWithProfilesSamplerReceivesCustomSamplingContext(): void
-    {
-        $customSamplingContext = ['a' => 'b'];
-
-        $client = $this->createMock(ClientInterface::class);
-        $client->expects($this->once())
-            ->method('getOptions')
-            ->willReturn(new Options([
-                'traces_sample_rate' => 1.0,
-                'profiles_sampler' => function (SamplingContext $samplingContext) use ($customSamplingContext): float {
-                    $this->assertSame($samplingContext->getAdditionalContext(), $customSamplingContext);
-
-                    return 0.0;
-                },
-            ]));
-
-        $hub = new Hub($client);
-        $hub->startTransaction(new TransactionContext(), $customSamplingContext);
-    }
-
-    public function testStartTransactionDoesNotStartProfilerWhenProfilesSamplerReturnsInvalidValue(): void
-    {
-        $client = $this->createMock(ClientInterface::class);
-        $client->expects($this->once())
-            ->method('getOptions')
-            ->willReturn(new Options([
-                'traces_sample_rate' => 1.0,
-                'profiles_sampler' => static function (): string {
-                    return 'foo';
-                },
-            ]));
-
-        $hub = new Hub($client);
-        $transaction = $hub->startTransaction(new TransactionContext());
-
-        $this->assertTrue($transaction->getSampled());
-        $this->assertNull($transaction->getProfiler());
-    }
-
-    public function testStartTransactionDoesNotCallProfilesSamplerWhenTransactionIsNotSampled(): void
-    {
-        $profilesSamplerInvoked = false;
-
-        $client = $this->createMock(ClientInterface::class);
-        $client->expects($this->once())
-            ->method('getOptions')
-            ->willReturn(new Options([
-                'traces_sample_rate' => 0.0,
-                'profiles_sampler' => static function () use (&$profilesSamplerInvoked): float {
-                    $profilesSamplerInvoked = true;
-
-                    return 1.0;
-                },
-            ]));
-
-        $hub = new Hub($client);
-        $transaction = $hub->startTransaction(new TransactionContext());
-
-        $this->assertFalse($transaction->getSampled());
-        $this->assertFalse($profilesSamplerInvoked);
-        $this->assertNull($transaction->getProfiler());
-    }
-
-    public function testStartTransactionUpdatesTheDscSampleRate(): void
-    {
-        $client = $this->createMock(ClientInterface::class);
-        $client->expects($this->once())
-            ->method('getOptions')
-            ->willReturn(new Options([
-                'traces_sampler' => static function (SamplingContext $samplingContext): float {
-                    return 1.0;
-                },
-            ]));
-
-        $hub = new Hub($client);
-
-        $dsc = DynamicSamplingContext::fromHeader('sentry-trace_id=d49d9bf66f13450b81f65bc51cf49c03,sentry-public_key=public');
-        $transactionMetaData = new TransactionMetadata(null, $dsc);
-        $transactionContext = new TransactionContext(TransactionContext::DEFAULT_NAME, null, $transactionMetaData);
-
-        $transaction = $hub->startTransaction($transactionContext);
-        $this->assertSame('1', $transaction->getMetadata()->getDynamicSamplingContext()->get('sample_rate'));
-    }
-
-    public function testGetTransactionReturnsInstanceSetOnTheScopeIfTransactionIsNotSampled(): void
-    {
-        $client = $this->createMock(ClientInterface::class);
-        $client->expects($this->once())
-            ->method('getOptions')
-            ->willReturn(new Options(['traces_sample_rate' => 1]));
-
-        $hub = new Hub($client);
-        $transaction = $hub->startTransaction(new TransactionContext(TransactionContext::DEFAULT_NAME, false));
-
-        $hub->configureScope(static function (Scope $scope) use ($transaction): void {
-            $scope->setSpan($transaction);
-        });
-
-        $this->assertSame($transaction, $hub->getTransaction());
-    }
-
-    public function testGetTransactionReturnsInstanceSetOnTheScopeIfTransactionIsSampled(): void
-    {
-        $client = $this->createMock(ClientInterface::class);
-        $client->expects($this->once())
-            ->method('getOptions')
-            ->willReturn(new Options(['traces_sample_rate' => 1]));
-
-        $hub = new Hub($client);
-        $transaction = $hub->startTransaction(new TransactionContext(TransactionContext::DEFAULT_NAME, true));
-
-        $hub->configureScope(static function (Scope $scope) use ($transaction): void {
-            $scope->setSpan($transaction);
-        });
-
-        $this->assertSame($transaction, $hub->getTransaction());
-    }
-
-    public function testGetTransactionReturnsNullIfNoTransactionIsSetOnTheScope(): void
-    {
-        $client = $this->createMock(ClientInterface::class);
-        $client->expects($this->once())
-            ->method('getOptions')
-            ->willReturn(new Options(['traces_sample_rate' => 1]));
-
-        $hub = new Hub($client);
-        $hub->startTransaction(new TransactionContext(TransactionContext::DEFAULT_NAME, true));
-
-        $this->assertNull($hub->getTransaction());
-    }
-
-    public function testEventTraceContextIsAlwaysFilled(): void
-    {
-        $hub = new Hub(new NoOpClient());
-
-        $event = Event::createEvent();
-
-        $hub->configureScope(function (Scope $scope) use ($event): void {
-            $event = $scope->applyToEvent($event);
-
-            $this->assertNotEmpty($event->getContexts()['trace']);
-        });
-    }
-
-    public function testEventTraceContextIsNotOverridenWhenPresent(): void
-    {
-        $hub = new Hub(new NoOpClient());
-
-        $traceContext = ['foo' => 'bar'];
-
-        $event = Event::createEvent();
-        $event->setContext('trace', $traceContext);
-
-        $hub->configureScope(function (Scope $scope) use ($event, $traceContext): void {
-            $event = $scope->applyToEvent($event);
-
-            $this->assertEquals($event->getContexts()['trace'], $traceContext);
-        });
-    }
-}
diff --git a/tests/State/LayerTest.php b/tests/State/LayerTest.php
deleted file mode 100644
index 501f0e5793..0000000000
--- a/tests/State/LayerTest.php
+++ /dev/null
@@ -1,37 +0,0 @@
-<?php
-
-declare(strict_types=1);
-
-namespace Sentry\Tests\State;
-
-use PHPUnit\Framework\MockObject\MockObject;
-use PHPUnit\Framework\TestCase;
-use Sentry\ClientInterface;
-use Sentry\State\Layer;
-use Sentry\State\Scope;
-
-final class LayerTest extends TestCase
-{
-    public function testGettersAndSetters(): void
-    {
-        /** @var ClientInterface|MockObject $client1 */
-        $client1 = $this->createMock(ClientInterface::class);
-
-        /** @var ClientInterface|MockObject $client2 */
-        $client2 = $this->createMock(ClientInterface::class);
-
-        $scope1 = new Scope();
-        $scope2 = new Scope();
-
-        $layer = new Layer($client1, $scope1);
-
-        $this->assertSame($client1, $layer->getClient());
-        $this->assertSame($scope1, $layer->getScope());
-
-        $layer->setClient($client2);
-        $layer->setScope($scope2);
-
-        $this->assertSame($client2, $layer->getClient());
-        $this->assertSame($scope2, $layer->getScope());
-    }
-}
diff --git a/tests/State/ScopeTest.php b/tests/State/ScopeTest.php
index a9a9d3e8aa..b02a18af02 100644
--- a/tests/State/ScopeTest.php
+++ b/tests/State/ScopeTest.php
@@ -7,10 +7,14 @@
 use PHPUnit\Framework\TestCase;
 use Sentry\Attachment\Attachment;
 use Sentry\Breadcrumb;
+use Sentry\ClientInterface;
 use Sentry\Event;
 use Sentry\EventHint;
+use Sentry\NoOpClient;
 use Sentry\Options;
 use Sentry\Severity;
+use Sentry\State\GlobalScope;
+use Sentry\State\IsolationScope;
 use Sentry\State\Scope;
 use Sentry\Tracing\DynamicSamplingContext;
 use Sentry\Tracing\PropagationContext;
@@ -24,10 +28,46 @@
 
 final class ScopeTest extends TestCase
 {
+    private function applyScope(IsolationScope $scope, Event $event, ?EventHint $hint = null, ?Options $options = null): ?Event
+    {
+        $globalScope = new GlobalScope();
+
+        return $globalScope->merge($scope)->applyToEvent($event, $hint, $options);
+    }
+
+    private function breadcrumbWithTimestamp(float $timestamp, string $category = 'test'): Breadcrumb
+    {
+        return new Breadcrumb(Breadcrumb::LEVEL_INFO, Breadcrumb::TYPE_DEFAULT, $category, null, [], $timestamp);
+    }
+
+    public function testGetAndSetClient(): void
+    {
+        $scope = new IsolationScope();
+
+        $this->assertInstanceOf(NoOpClient::class, $scope->getClient());
+
+        $client = $this->createMock(ClientInterface::class);
+
+        $this->assertSame($scope, $scope->setClient($client));
+        $this->assertSame($client, $scope->getClient());
+    }
+
+    public function testClonedScopeKeepsClientShared(): void
+    {
+        $client = $this->createMock(ClientInterface::class);
+
+        $scope = new IsolationScope();
+        $scope->setClient($client);
+
+        $clonedScope = clone $scope;
+
+        $this->assertSame($client, $clonedScope->getClient());
+    }
+
     public function testSetTag(): void
     {
-        $scope = new Scope();
-        $event = $scope->applyToEvent(Event::createEvent());
+        $scope = new IsolationScope();
+        $event = $this->applyScope($scope, Event::createEvent());
 
         $this->assertNotNull($event);
         $this->assertEmpty($event->getTags());
@@ -35,7 +75,7 @@ public function testSetTag(): void
         $scope->setTag('foo', 'bar');
         $scope->setTag('bar', 'baz');
 
-        $event = $scope->applyToEvent(Event::createEvent());
+        $event = $this->applyScope($scope, Event::createEvent());
 
         $this->assertNotNull($event);
         $this->assertSame(['foo' => 'bar', 'bar' => 'baz'], $event->getTags());
@@ -43,17 +83,17 @@ public function testSetTag(): void
 
     public function testSetTags(): void
     {
-        $scope = new Scope();
+        $scope = new IsolationScope();
         $scope->setTags(['foo' => 'bar']);
 
-        $event = $scope->applyToEvent(Event::createEvent());
+        $event = $this->applyScope($scope, Event::createEvent());
 
         $this->assertNotNull($event);
         $this->assertSame(['foo' => 'bar'], $event->getTags());
 
         $scope->setTags(['bar' => 'baz']);
 
-        $event = $scope->applyToEvent(Event::createEvent());
+        $event = $this->applyScope($scope, Event::createEvent());
 
         $this->assertNotNull($event);
         $this->assertSame(['foo' => 'bar', 'bar' => 'baz'], $event->getTags());
@@ -61,20 +101,20 @@ public function testSetTags(): void
 
     public function testRemoveTag(): void
     {
-        $scope = new Scope();
-        $event = $scope->applyToEvent(Event::createEvent());
+        $scope = new IsolationScope();
+        $event = $this->applyScope($scope, Event::createEvent());
 
         $scope->setTag('foo', 'bar');
         $scope->setTag('bar', 'baz');
 
-        $event = $scope->applyToEvent(Event::createEvent());
+        $event = $this->applyScope($scope, Event::createEvent());
 
         $this->assertNotNull($event);
         $this->assertSame(['foo' => 'bar', 'bar' => 'baz'], $event->getTags());
 
         $scope->removeTag('foo');
 
-        $event = $scope->applyToEvent(Event::createEvent());
+        $event = $this->applyScope($scope, Event::createEvent());
 
         $this->assertNotNull($event);
         $this->assertSame(['bar' => 'baz'], $event->getTags());
@@ -82,8 +122,8 @@ public function testRemoveTag(): void
 
     public function testSetFlag(): void
     {
-        $scope = new Scope();
-        $event = $scope->applyToEvent(Event::createEvent());
+        $scope = new IsolationScope();
+        $event = $this->applyScope($scope, Event::createEvent());
 
         $this->assertNotNull($event);
         $this->assertArrayNotHasKey('flags', $event->getContexts());
@@ -91,7 +131,7 @@ public function testSetFlag(): void
         $scope->addFeatureFlag('foo', true);
         $scope->addFeatureFlag('bar', false);
 
-        $event = $scope->applyToEvent(Event::createEvent());
+        $event = $this->applyScope($scope, Event::createEvent());
 
         $this->assertNotNull($event);
         $this->assertArrayHasKey('flags', $event->getContexts());
@@ -111,8 +151,8 @@ public function testSetFlag(): void
 
     public function testSetFlagLimit(): void
     {
-        $scope = new Scope();
-        $event = $scope->applyToEvent(Event::createEvent());
+        $scope = new IsolationScope();
+        $event = $this->applyScope($scope, Event::createEvent());
 
         $this->assertNotNull($event);
         $this->assertArrayNotHasKey('flags', $event->getContexts());
@@ -128,7 +168,7 @@ public function testSetFlagLimit(): void
             ];
         }
 
-        $event = $scope->applyToEvent(Event::createEvent());
+        $event = $this->applyScope($scope, Event::createEvent());
 
         $this->assertNotNull($event);
         $this->assertArrayHasKey('flags', $event->getContexts());
@@ -143,7 +183,7 @@ public function testSetFlagLimit(): void
             'result' => true,
         ];
 
-        $event = $scope->applyToEvent(Event::createEvent());
+        $event = $this->applyScope($scope, Event::createEvent());
 
         $this->assertNotNull($event);
         $this->assertArrayHasKey('flags', $event->getContexts());
@@ -154,7 +194,7 @@ public function testSetFlagPropagatesToSpan(): void
     {
         $span = new Span();
 
-        $scope = new Scope();
+        $scope = new IsolationScope();
         $scope->setSpan($span);
 
         $scope->addFeatureFlag('feature', true);
@@ -166,10 +206,10 @@ public function testSetAndRemoveContext(): void
     {
         $propgationContext = PropagationContext::fromDefaults();
 
-        $scope = new Scope($propgationContext);
+        $scope = new IsolationScope($propgationContext);
         $scope->setContext('foo', ['foo' => 'bar']);
 
-        $event = $scope->applyToEvent(Event::createEvent());
+        $event = $this->applyScope($scope, Event::createEvent());
 
         $this->assertNotNull($event);
         $this->assertSame([
@@ -182,7 +222,7 @@ public function testSetAndRemoveContext(): void
 
         $scope->removeContext('foo');
 
-        $event = $scope->applyToEvent(Event::createEvent());
+        $event = $this->applyScope($scope, Event::createEvent());
 
         $this->assertNotNull($event);
         $this->assertSame([
@@ -194,7 +234,7 @@ public function testSetAndRemoveContext(): void
 
         $scope->setContext('foo', []);
 
-        $event = $scope->applyToEvent(Event::createEvent());
+        $event = $this->applyScope($scope, Event::createEvent());
 
         $this->assertNotNull($event);
         $this->assertSame([
@@ -207,8 +247,8 @@ public function testSetAndRemoveContext(): void
 
     public function testSetExtra(): void
     {
-        $scope = new Scope();
-        $event = $scope->applyToEvent(Event::createEvent());
+        $scope = new IsolationScope();
+        $event = $this->applyScope($scope, Event::createEvent());
 
         $this->assertNotNull($event);
         $this->assertEmpty($event->getExtra());
@@ -216,7 +256,7 @@ public function testSetExtra(): void
         $scope->setExtra('foo', 'bar');
         $scope->setExtra('bar', 'baz');
 
-        $event = $scope->applyToEvent(Event::createEvent());
+        $event = $this->applyScope($scope, Event::createEvent());
 
         $this->assertNotNull($event);
         $this->assertSame(['foo' => 'bar', 'bar' => 'baz'], $event->getExtra());
@@ -224,17 +264,17 @@ public function testSetExtra(): void
 
     public function testSetExtras(): void
     {
-        $scope = new Scope();
+        $scope = new IsolationScope();
         $scope->setExtras(['foo' => 'bar']);
 
-        $event = $scope->applyToEvent(Event::createEvent());
+        $event = $this->applyScope($scope, Event::createEvent());
 
         $this->assertNotNull($event);
         $this->assertSame(['foo' => 'bar'], $event->getExtra());
 
         $scope->setExtras(['bar' => 'baz']);
 
-        $event = $scope->applyToEvent(Event::createEvent());
+        $event = $this->applyScope($scope, Event::createEvent());
 
         $this->assertNotNull($event);
         $this->assertSame(['foo' => 'bar', 'bar' => 'baz'], $event->getExtra());
@@ -242,8 +282,8 @@ public function testSetExtras(): void
 
     public function testSetUser(): void
     {
-        $scope = new Scope();
-        $event = $scope->applyToEvent(Event::createEvent());
+        $scope = new IsolationScope();
+        $event = $this->applyScope($scope, Event::createEvent());
 
         $this->assertNotNull($event);
         $this->assertNull($event->getUser());
@@ -253,21 +293,21 @@ public function testSetUser(): void
 
         $scope->setUser($user);
 
-        $event = $scope->applyToEvent(Event::createEvent());
+        $event = $this->applyScope($scope, Event::createEvent());
 
         $this->assertNotNull($event);
-        $this->assertSame($user, $event->getUser());
+        $this->assertEquals($user, $event->getUser());
 
-        $user = UserDataBag::createFromUserIpAddress('127.0.0.1');
-        $user->setMetadata('subscription', 'basic');
-        $user->setMetadata('subscription_expires_at', '2020-08-26');
+        $expectedUser = UserDataBag::createFromUserIdentifier('unique_id');
+        $expectedUser->setMetadata('subscription', 'basic');
+        $expectedUser->setMetadata('subscription_expires_at', '2020-08-26');
 
         $scope->setUser(['ip_address' => '127.0.0.1', 'subscription_expires_at' => '2020-08-26']);
 
-        $event = $scope->applyToEvent($event);
+        $event = $this->applyScope($scope, $event);
 
         $this->assertNotNull($event);
-        $this->assertEquals($user, $event->getUser());
+        $this->assertEquals($expectedUser, $event->getUser());
     }
 
     public function testSetUserThrowsOnInvalidArgument(): void
@@ -275,23 +315,23 @@ public function testSetUserThrowsOnInvalidArgument(): void
         $this->expectException(\TypeError::class);
         $this->expectExceptionMessage('The $user argument must be either an array or an instance of the "Sentry\UserDataBag" class. Got: "string".');
 
-        $scope = new Scope();
+        $scope = new IsolationScope();
         $scope->setUser('foo');
     }
 
     public function testRemoveUser(): void
     {
-        $scope = new Scope();
+        $scope = new IsolationScope();
         $scope->setUser(UserDataBag::createFromUserIdentifier('unique_id'));
 
-        $event = $scope->applyToEvent(Event::createEvent());
+        $event = $this->applyScope($scope, Event::createEvent());
 
         $this->assertNotNull($event);
         $this->assertNotNull($event->getUser());
 
         $scope->removeUser();
 
-        $event = $scope->applyToEvent(Event::createEvent());
+        $event = $this->applyScope($scope, Event::createEvent());
 
         $this->assertNotNull($event);
         $this->assertNull($event->getUser());
@@ -299,15 +339,15 @@ public function testRemoveUser(): void
 
     public function testSetFingerprint(): void
     {
-        $scope = new Scope();
-        $event = $scope->applyToEvent(Event::createEvent());
+        $scope = new IsolationScope();
+        $event = $this->applyScope($scope, Event::createEvent());
 
         $this->assertNotNull($event);
         $this->assertEmpty($event->getFingerprint());
 
         $scope->setFingerprint(['foo', 'bar']);
 
-        $event = $scope->applyToEvent(Event::createEvent());
+        $event = $this->applyScope($scope, Event::createEvent());
 
         $this->assertNotNull($event);
         $this->assertSame(['foo', 'bar'], $event->getFingerprint());
@@ -315,15 +355,15 @@ public function testSetFingerprint(): void
 
     public function testSetLevel(): void
     {
-        $scope = new Scope();
-        $event = $scope->applyToEvent(Event::createEvent());
+        $scope = new IsolationScope();
+        $event = $this->applyScope($scope, Event::createEvent());
 
         $this->assertNotNull($event);
         $this->assertNull($event->getLevel());
 
         $scope->setLevel(Severity::debug());
 
-        $event = $scope->applyToEvent(Event::createEvent());
+        $event = $this->applyScope($scope, Event::createEvent());
 
         $this->assertNotNull($event);
         $this->assertEquals(Severity::debug(), $event->getLevel());
@@ -331,12 +371,12 @@ public function testSetLevel(): void
 
     public function testAddBreadcrumb(): void
     {
-        $scope = new Scope();
+        $scope = new IsolationScope();
         $breadcrumb1 = new Breadcrumb(Breadcrumb::LEVEL_ERROR, Breadcrumb::TYPE_ERROR, 'error_reporting');
         $breadcrumb2 = new Breadcrumb(Breadcrumb::LEVEL_ERROR, Breadcrumb::TYPE_ERROR, 'error_reporting');
         $breadcrumb3 = new Breadcrumb(Breadcrumb::LEVEL_ERROR, Breadcrumb::TYPE_ERROR, 'error_reporting');
 
-        $event = $scope->applyToEvent(Event::createEvent());
+        $event = $this->applyScope($scope, Event::createEvent());
 
         $this->assertNotNull($event);
         $this->assertEmpty($event->getBreadcrumbs());
@@ -344,14 +384,14 @@ public function testAddBreadcrumb(): void
         $scope->addBreadcrumb($breadcrumb1);
         $scope->addBreadcrumb($breadcrumb2);
 
-        $event = $scope->applyToEvent(Event::createEvent());
+        $event = $this->applyScope($scope, Event::createEvent());
 
         $this->assertNotNull($event);
         $this->assertSame([$breadcrumb1, $breadcrumb2], $event->getBreadcrumbs());
 
         $scope->addBreadcrumb($breadcrumb3, 2);
 
-        $event = $scope->applyToEvent(Event::createEvent());
+        $event = $this->applyScope($scope, Event::createEvent());
 
         $this->assertNotNull($event);
         $this->assertSame([$breadcrumb2, $breadcrumb3], $event->getBreadcrumbs());
@@ -359,19 +399,19 @@ public function testAddBreadcrumb(): void
 
     public function testClearBreadcrumbs(): void
     {
-        $scope = new Scope();
+        $scope = new IsolationScope();
 
         $scope->addBreadcrumb(new Breadcrumb(Breadcrumb::LEVEL_ERROR, Breadcrumb::TYPE_ERROR, 'error_reporting'));
         $scope->addBreadcrumb(new Breadcrumb(Breadcrumb::LEVEL_ERROR, Breadcrumb::TYPE_ERROR, 'error_reporting'));
 
-        $event = $scope->applyToEvent(Event::createEvent());
+        $event = $this->applyScope($scope, Event::createEvent());
 
         $this->assertNotNull($event);
         $this->assertNotEmpty($event->getBreadcrumbs());
 
         $scope->clearBreadcrumbs();
 
-        $event = $scope->applyToEvent(Event::createEvent());
+        $event = $this->applyScope($scope, Event::createEvent());
 
         $this->assertNotNull($event);
         $this->assertEmpty($event->getBreadcrumbs());
@@ -384,7 +424,7 @@ public function testAddEventProcessor(): void
         $callback3Called = false;
 
         $event = Event::createEvent();
-        $scope = new Scope();
+        $scope = new IsolationScope();
 
         $scope->addEventProcessor(function (Event $eventArg) use (&$callback1Called, $callback2Called, $callback3Called): ?Event {
             $this->assertFalse($callback2Called);
@@ -395,7 +435,7 @@ public function testAddEventProcessor(): void
             return $eventArg;
         });
 
-        $this->assertSame($event, $scope->applyToEvent($event));
+        $this->assertSame($event, $this->applyScope($scope, $event));
         $this->assertTrue($callback1Called);
 
         $scope->addEventProcessor(function () use ($callback1Called, &$callback2Called, $callback3Called) {
@@ -413,7 +453,7 @@ public function testAddEventProcessor(): void
             return null;
         });
 
-        $this->assertNull($scope->applyToEvent($event));
+        $this->assertNull($this->applyScope($scope, $event));
         $this->assertTrue($callback2Called);
         $this->assertFalse($callback3Called);
     }
@@ -421,7 +461,7 @@ public function testAddEventProcessor(): void
     public function testEventProcessorReceivesTheEventAndEventHint(): void
     {
         $event = Event::createEvent();
-        $scope = new Scope();
+        $scope = new IsolationScope();
         $hint = new EventHint();
 
         $processorCalled = false;
@@ -434,16 +474,18 @@ public function testEventProcessorReceivesTheEventAndEventHint(): void
             return $eventArg;
         });
 
-        $this->assertSame($event, $scope->applyToEvent($event, $hint));
+        $this->assertSame($event, $this->applyScope($scope, $event, $hint));
         $this->assertSame($hint, $processorReceivedHint);
         $this->assertTrue($processorCalled);
     }
 
     public function testClear(): void
     {
-        $scope = new Scope();
+        $scope = new IsolationScope();
         $breadcrumb = new Breadcrumb(Breadcrumb::LEVEL_ERROR, Breadcrumb::TYPE_ERROR, 'error_reporting');
+        $client = $this->createMock(ClientInterface::class);
 
+        $scope->setClient($client);
         $scope->setLevel(Severity::info());
         $scope->addBreadcrumb($breadcrumb);
         $scope->setFingerprint(['foo']);
@@ -453,7 +495,7 @@ public function testClear(): void
         $scope->setUser(UserDataBag::createFromUserIdentifier('unique_id'));
         $scope->clear();
 
-        $event = $scope->applyToEvent(Event::createEvent());
+        $event = $this->applyScope($scope, Event::createEvent());
 
         $this->assertNotNull($event);
         $this->assertNull($event->getLevel());
@@ -463,6 +505,7 @@ public function testClear(): void
         $this->assertEmpty($event->getTags());
         $this->assertEmpty($event->getUser());
         $this->assertArrayNotHasKey('flags', $event->getContexts());
+        $this->assertSame($client, $scope->getClient());
     }
 
     public function testApplyToEvent(): void
@@ -481,7 +524,7 @@ public function testApplyToEvent(): void
         $span = $transaction->startChild(new SpanContext());
         $span->setSpanId(new SpanId('566e3688a61d4bc8'));
 
-        $scope = new Scope();
+        $scope = new IsolationScope();
         $scope->setLevel(Severity::warning());
         $scope->setFingerprint(['foo']);
         $scope->addBreadcrumb($breadcrumb);
@@ -493,13 +536,13 @@ public function testApplyToEvent(): void
         $scope->addFeatureFlag('feature', true);
         $scope->setSpan($span);
 
-        $this->assertSame($event, $scope->applyToEvent($event));
+        $this->assertSame($event, $this->applyScope($scope, $event));
         $this->assertTrue($event->getLevel()->isEqualTo(Severity::warning()));
         $this->assertSame(['foo'], $event->getFingerprint());
         $this->assertSame([$breadcrumb], $event->getBreadcrumbs());
         $this->assertSame(['foo' => 'bar'], $event->getTags());
         $this->assertSame(['bar' => 'foo'], $event->getExtra());
-        $this->assertSame($user, $event->getUser());
+        $this->assertEquals($user, $event->getUser());
         $this->assertSame([
             'foocontext' => [
                 'foo' => 'foo',
@@ -531,14 +574,372 @@ public function testApplyToEvent(): void
         $this->assertSame('566e3688a61d4bc888951642d6f14a19', $dynamicSamplingContext->get('trace_id'));
     }
 
+    public function testMergeScopesAppliesGlobalScopeUnderIsolationScope(): void
+    {
+        $globalBreadcrumb = new Breadcrumb(Breadcrumb::LEVEL_INFO, Breadcrumb::TYPE_DEFAULT, 'global');
+        $isolationBreadcrumb = new Breadcrumb(Breadcrumb::LEVEL_INFO, Breadcrumb::TYPE_DEFAULT, 'isolation');
+        $globalAttachment = Attachment::fromBytes('global.txt', 'global');
+        $isolationAttachment = Attachment::fromBytes('isolation.txt', 'isolation');
+
+        $globalUser = UserDataBag::createFromUserIdentifier('global-user');
+        $globalUser->setMetadata('shared', 'global');
+        $globalUser->setMetadata('global', true);
+
+        $globalScope = new GlobalScope();
+        $globalScope->setTag('shared', 'global');
+        $globalScope->setTag('global', 'tag');
+        $globalScope->setExtra('shared', 'global');
+        $globalScope->setExtra('global', true);
+        $globalScope->setContext('shared_context', ['value' => 'global']);
+        $globalScope->setContext('global_context', ['value' => 'global']);
+        $globalScope->setUser($globalUser);
+        $globalScope->setLevel(Severity::error());
+        $globalScope->setFingerprint(['global-fingerprint']);
+        $globalScope->addBreadcrumb($globalBreadcrumb);
+        $globalScope->addAttachment($globalAttachment);
+
+        $isolationUser = UserDataBag::createFromUserIdentifier('isolation-user');
+        $isolationUser->setMetadata('shared', 'isolation');
+        $isolationUser->setMetadata('isolation', true);
+
+        $isolationScope = new IsolationScope();
+        $isolationScope->setTag('shared', 'isolation');
+        $isolationScope->setTag('isolation', 'tag');
+        $isolationScope->setExtra('shared', 'isolation');
+        $isolationScope->setExtra('isolation', true);
+        $isolationScope->setContext('shared_context', ['value' => 'isolation']);
+        $isolationScope->setContext('isolation_context', ['value' => 'isolation']);
+        $isolationScope->setUser($isolationUser);
+        $isolationScope->setLevel(Severity::warning());
+        $isolationScope->setFingerprint(['isolation-fingerprint']);
+        $isolationScope->addBreadcrumb($isolationBreadcrumb);
+        $isolationScope->addFeatureFlag('shared-flag', true);
+        $isolationScope->addFeatureFlag('isolation-flag', false);
+        $isolationScope->addAttachment($isolationAttachment);
+
+        $eventUser = UserDataBag::createFromUserIdentifier('event-user');
+        $eventUser->setMetadata('shared', 'event');
+        $eventUser->setMetadata('event', true);
+
+        $event = Event::createEvent();
+        $event->setTag('shared', 'event');
+        $event->setTag('event', 'tag');
+        $event->setExtra(['shared' => 'event', 'event' => true]);
+        $event->setContext('shared_context', ['value' => 'event']);
+        $event->setUser($eventUser);
+        $event->setFingerprint(['event-fingerprint']);
+
+        $event = $globalScope->merge($isolationScope)->applyToEvent($event);
+
+        $this->assertNotNull($event);
+        $this->assertTrue($event->getLevel()->isEqualTo(Severity::warning()));
+        $this->assertSame(['event-fingerprint', 'global-fingerprint', 'isolation-fingerprint'], $event->getFingerprint());
+        $this->assertSame([
+            'shared' => 'event',
+            'global' => 'tag',
+            'isolation' => 'tag',
+            'event' => 'tag',
+        ], $event->getTags());
+        $this->assertSame([
+            'shared' => 'event',
+            'global' => true,
+            'isolation' => true,
+            'event' => true,
+        ], $event->getExtra());
+        $this->assertSame(['value' => 'event'], $event->getContexts()['shared_context']);
+        $this->assertSame(['value' => 'global'], $event->getContexts()['global_context']);
+        $this->assertSame(['value' => 'isolation'], $event->getContexts()['isolation_context']);
+        $this->assertSame([
+            'values' => [
+                [
+                    'flag' => 'shared-flag',
+                    'result' => true,
+                ],
+                [
+                    'flag' => 'isolation-flag',
+                    'result' => false,
+                ],
+            ],
+        ], $event->getContexts()['flags']);
+        $this->assertSame([$globalBreadcrumb, $isolationBreadcrumb], $event->getBreadcrumbs());
+        $this->assertSame([$globalAttachment, $isolationAttachment], $event->getAttachments());
+
+        $user = $event->getUser();
+        $this->assertNotNull($user);
+        $this->assertSame('event-user', $user->getId());
+        $this->assertSame([
+            'shared' => 'event',
+            'global' => true,
+            'isolation' => true,
+            'event' => true,
+        ], $user->getMetadata());
+    }
+
+    public function testMergeScopesUsesGlobalLevelWhenIsolationLevelIsUnset(): void
+    {
+        $globalScope = new GlobalScope();
+        $globalScope->setLevel(Severity::error());
+
+        $event = $globalScope->merge(new IsolationScope())->applyToEvent(Event::createEvent());
+
+        $this->assertNotNull($event);
+        $this->assertTrue($event->getLevel()->isEqualTo(Severity::error()));
+    }
+
+    public function testMergeScopesCapsBreadcrumbsAndFlags(): void
+    {
+        $globalScope = new GlobalScope();
+        $globalBreadcrumbs = [];
+
+        foreach (range(1, 100) as $i) {
+            $breadcrumb = new Breadcrumb(Breadcrumb::LEVEL_INFO, Breadcrumb::TYPE_DEFAULT, "global{$i}");
+            $globalBreadcrumbs[] = $breadcrumb;
+            $globalScope->addBreadcrumb($breadcrumb);
+        }
+
+        $isolationBreadcrumb = new Breadcrumb(Breadcrumb::LEVEL_INFO, Breadcrumb::TYPE_DEFAULT, 'isolation');
+        $isolationScope = new IsolationScope();
+        $isolationScope->addBreadcrumb($isolationBreadcrumb);
+
+        foreach (range(1, Scope::MAX_FLAGS) as $i) {
+            $isolationScope->addFeatureFlag("feature{$i}", true);
+        }
+
+        $isolationScope->addFeatureFlag('feature50', false);
+        $isolationScope->addFeatureFlag('feature101', true);
+
+        $event = $globalScope->merge($isolationScope)->applyToEvent(Event::createEvent());
+
+        $this->assertNotNull($event);
+        $this->assertCount(100, $event->getBreadcrumbs());
+        $this->assertSame($globalBreadcrumbs[1], $event->getBreadcrumbs()[0]);
+        $this->assertSame($isolationBreadcrumb, $event->getBreadcrumbs()[99]);
+
+        $flags = $event->getContexts()['flags']['values'];
+        $this->assertCount(Scope::MAX_FLAGS, $flags);
+        $this->assertSame([
+            'flag' => 'feature2',
+            'result' => true,
+        ], $flags[0]);
+        $this->assertSame([
+            'flag' => 'feature50',
+            'result' => false,
+        ], $flags[98]);
+        $this->assertSame([
+            'flag' => 'feature101',
+            'result' => true,
+        ], $flags[99]);
+        $this->assertFalse(\in_array('feature1', array_column($flags, 'flag'), true));
+    }
+
+    public function testMergeScopesInterleavesBreadcrumbsChronologically(): void
+    {
+        $globalBreadcrumb1 = $this->breadcrumbWithTimestamp(1.0, 'global1');
+        $globalBreadcrumb2 = $this->breadcrumbWithTimestamp(3.0, 'global2');
+        $isolationBreadcrumb1 = $this->breadcrumbWithTimestamp(2.0, 'isolation1');
+        $isolationBreadcrumb2 = $this->breadcrumbWithTimestamp(4.0, 'isolation2');
+
+        $globalScope = new GlobalScope();
+        $globalScope->addBreadcrumb($globalBreadcrumb1);
+        $globalScope->addBreadcrumb($globalBreadcrumb2);
+
+        $isolationScope = new IsolationScope();
+        $isolationScope->addBreadcrumb($isolationBreadcrumb1);
+        $isolationScope->addBreadcrumb($isolationBreadcrumb2);
+
+        $event = $globalScope->merge($isolationScope)->applyToEvent(Event::createEvent());
+
+        $this->assertNotNull($event);
+        $this->assertSame([$globalBreadcrumb1, $isolationBreadcrumb1, $globalBreadcrumb2, $isolationBreadcrumb2], $event->getBreadcrumbs());
+    }
+
+    public function testMergeScopesRespectsMaxBreadcrumbsLargerThanDefault(): void
+    {
+        $options = new Options(['max_breadcrumbs' => 150]);
+        $globalScope = new GlobalScope();
+        $isolationScope = new IsolationScope();
+        $breadcrumbs = [];
+
+        foreach (range(1, 100) as $i) {
+            $breadcrumb = $this->breadcrumbWithTimestamp((float) $i, "global{$i}");
+            $breadcrumbs[] = $breadcrumb;
+            $globalScope->addBreadcrumb($breadcrumb, 150);
+        }
+
+        foreach (range(101, 200) as $i) {
+            $breadcrumb = $this->breadcrumbWithTimestamp((float) $i, "isolation{$i}");
+            $breadcrumbs[] = $breadcrumb;
+            $isolationScope->addBreadcrumb($breadcrumb, 150);
+        }
+
+        $event = $globalScope->merge($isolationScope)->applyToEvent(Event::createEvent(), null, $options);
+
+        $this->assertNotNull($event);
+        $this->assertCount(150, $event->getBreadcrumbs());
+        $this->assertSame(\array_slice($breadcrumbs, -150), $event->getBreadcrumbs());
+    }
+
+    public function testMergeScopesAppliesMaxBreadcrumbsSmallerThanMergedCount(): void
+    {
+        $globalBreadcrumb1 = $this->breadcrumbWithTimestamp(1.0, 'global1');
+        $globalBreadcrumb2 = $this->breadcrumbWithTimestamp(4.0, 'global2');
+        $isolationBreadcrumb1 = $this->breadcrumbWithTimestamp(2.0, 'isolation1');
+        $isolationBreadcrumb2 = $this->breadcrumbWithTimestamp(3.0, 'isolation2');
+        $isolationBreadcrumb3 = $this->breadcrumbWithTimestamp(5.0, 'isolation3');
+
+        $globalScope = new GlobalScope();
+        $globalScope->addBreadcrumb($globalBreadcrumb1);
+        $globalScope->addBreadcrumb($globalBreadcrumb2);
+
+        $isolationScope = new IsolationScope();
+        $isolationScope->addBreadcrumb($isolationBreadcrumb1);
+        $isolationScope->addBreadcrumb($isolationBreadcrumb2);
+        $isolationScope->addBreadcrumb($isolationBreadcrumb3);
+
+        $event = $globalScope->merge($isolationScope)->applyToEvent(Event::createEvent(), null, new Options(['max_breadcrumbs' => 3]));
+
+        $this->assertNotNull($event);
+        $this->assertSame([$isolationBreadcrumb2, $globalBreadcrumb2, $isolationBreadcrumb3], $event->getBreadcrumbs());
+    }
+
+    public function testMergeScopesBreadcrumbsWithEqualTimestampsKeepGlobalScopeFirst(): void
+    {
+        $globalBreadcrumb1 = $this->breadcrumbWithTimestamp(1.0, 'global1');
+        $globalBreadcrumb2 = $this->breadcrumbWithTimestamp(1.0, 'global2');
+        $isolationBreadcrumb1 = $this->breadcrumbWithTimestamp(1.0, 'isolation1');
+        $isolationBreadcrumb2 = $this->breadcrumbWithTimestamp(1.0, 'isolation2');
+
+        $globalScope = new GlobalScope();
+        $globalScope->addBreadcrumb($globalBreadcrumb1);
+        $globalScope->addBreadcrumb($globalBreadcrumb2);
+
+        $isolationScope = new IsolationScope();
+        $isolationScope->addBreadcrumb($isolationBreadcrumb1);
+        $isolationScope->addBreadcrumb($isolationBreadcrumb2);
+
+        $event = $globalScope->merge($isolationScope)->applyToEvent(Event::createEvent());
+
+        $this->assertNotNull($event);
+        $this->assertSame([$globalBreadcrumb1, $globalBreadcrumb2, $isolationBreadcrumb1, $isolationBreadcrumb2], $event->getBreadcrumbs());
+    }
+
+    public function testMergeScopesPreservesInsertionOrderWithinScopeForOutOfOrderTimestamps(): void
+    {
+        // Breadcrumbs recorded on the same scope are never reordered, even when
+        // their user-supplied timestamps are not monotonic; only breadcrumbs of
+        // different scopes are interleaved by timestamp.
+        $globalBreadcrumb = $this->breadcrumbWithTimestamp(4.0, 'global1');
+        $isolationBreadcrumb1 = $this->breadcrumbWithTimestamp(2.0, 'isolation1');
+        $isolationBreadcrumb2 = $this->breadcrumbWithTimestamp(6.0, 'isolation2');
+        $isolationBreadcrumb3 = $this->breadcrumbWithTimestamp(1.0, 'isolation3');
+
+        $globalScope = new GlobalScope();
+        $globalScope->addBreadcrumb($globalBreadcrumb);
+
+        $isolationScope = new IsolationScope();
+        $isolationScope->addBreadcrumb($isolationBreadcrumb1);
+        $isolationScope->addBreadcrumb($isolationBreadcrumb2);
+        $isolationScope->addBreadcrumb($isolationBreadcrumb3);
+
+        $event = $globalScope->merge($isolationScope)->applyToEvent(Event::createEvent());
+
+        $this->assertNotNull($event);
+        $this->assertSame([$isolationBreadcrumb1, $globalBreadcrumb, $isolationBreadcrumb2, $isolationBreadcrumb3], $event->getBreadcrumbs());
+    }
+
+    public function testApplyToEventDropsScopeBreadcrumbsWhenMaxBreadcrumbsIsZero(): void
+    {
+        $scope = new IsolationScope();
+        $scope->addBreadcrumb(new Breadcrumb(Breadcrumb::LEVEL_INFO, Breadcrumb::TYPE_DEFAULT, 'test'));
+
+        $event = $this->applyScope($scope, Event::createEvent(), null, new Options(['max_breadcrumbs' => 0]));
+
+        $this->assertNotNull($event);
+        $this->assertSame([], $event->getBreadcrumbs());
+    }
+
+    public function testApplyToEventDoesNotOverrideEventBreadcrumbs(): void
+    {
+        $eventBreadcrumb = new Breadcrumb(Breadcrumb::LEVEL_INFO, Breadcrumb::TYPE_DEFAULT, 'event');
+
+        $scope = new IsolationScope();
+        $scope->addBreadcrumb(new Breadcrumb(Breadcrumb::LEVEL_INFO, Breadcrumb::TYPE_DEFAULT, 'scope'));
+
+        $event = Event::createEvent();
+        $event->setBreadcrumb([$eventBreadcrumb]);
+
+        $event = $this->applyScope($scope, $event);
+
+        $this->assertNotNull($event);
+        $this->assertSame([$eventBreadcrumb], $event->getBreadcrumbs());
+    }
+
+    public function testMergeScopesKeepsTraceStateFromIsolationScope(): void
+    {
+        $globalScope = new GlobalScope();
+
+        $isolationPropagationContext = PropagationContext::fromDefaults();
+        $isolationPropagationContext->setTraceId(new TraceId('33333333333333333333333333333333'));
+        $isolationPropagationContext->setSpanId(new SpanId('3333333333333333'));
+
+        $isolationScope = new IsolationScope($isolationPropagationContext);
+
+        $this->assertNull($isolationScope->getSpan());
+        $this->assertSame([
+            'trace_id' => '33333333333333333333333333333333',
+            'span_id' => '3333333333333333',
+        ], $isolationScope->getTraceContext());
+
+        $mergedScope = $globalScope->merge($isolationScope);
+        $isolationScope->setPropagationContext(PropagationContext::fromDefaults());
+
+        $event = $mergedScope->applyToEvent(Event::createEvent());
+
+        $this->assertNotNull($event);
+        $this->assertSame([
+            'trace_id' => '33333333333333333333333333333333',
+            'span_id' => '3333333333333333',
+        ], $event->getContexts()['trace']);
+    }
+
+    public function testMergeScopesKeepsProcessorOrder(): void
+    {
+        $calls = [];
+
+        Scope::addGlobalEventProcessor(static function (Event $event) use (&$calls): ?Event {
+            $calls[] = 'static';
+
+            return $event;
+        });
+
+        $globalScope = new GlobalScope();
+        $globalScope->addEventProcessor(static function (Event $event) use (&$calls): ?Event {
+            $calls[] = 'global';
+
+            return $event;
+        });
+
+        $isolationScope = new IsolationScope();
+        $isolationScope->addEventProcessor(static function (Event $event) use (&$calls): ?Event {
+            $calls[] = 'isolation';
+
+            return $event;
+        });
+
+        $event = $globalScope->merge($isolationScope)->applyToEvent(Event::createEvent());
+
+        $this->assertNotNull($event);
+        $this->assertSame(['static', 'global', 'isolation'], $calls);
+    }
+
     /**
      * @dataProvider eventWithLogCountProvider
      */
     public function testAttachmentsAppliedForType(Event $event, int $attachmentCount): void
     {
-        $scope = new Scope();
+        $scope = new IsolationScope();
         $scope->addAttachment(Attachment::fromBytes('test', 'abcde'));
-        $scope->applyToEvent($event);
+        $this->applyScope($scope, $event);
         $this->assertCount($attachmentCount, $event->getAttachments());
     }
 
@@ -563,7 +964,7 @@ public function testGetTraceContextPrefersExternalPropagationContextOverPropagat
             ];
         });
 
-        $scope = new Scope($propagationContext);
+        $scope = new IsolationScope($propagationContext);
 
         $this->assertSame([
             'trace_id' => '771a43a4192642f0b136d5159a501700',
@@ -588,7 +989,7 @@ public function testGetTraceContextPrefersLocalSpanOverExternalPropagationContex
         $span = $transaction->startChild(new SpanContext());
         $span->setSpanId(new SpanId('566e3688a61d4bc8'));
 
-        $scope = new Scope();
+        $scope = new IsolationScope();
         $scope->setSpan($span);
 
         $this->assertSame([
@@ -610,8 +1011,8 @@ public function testApplyToEventSkipsDynamicSamplingContextWhenUsingExternalProp
             ];
         });
 
-        $scope = new Scope();
-        $event = $scope->applyToEvent(Event::createEvent(), null, new Options([
+        $scope = new IsolationScope();
+        $event = $this->applyScope($scope, Event::createEvent(), null, new Options([
             'dsn' => 'http://public@example.com/1',
             'release' => '1.0.0',
             'environment' => 'test',
diff --git a/tests/Tracing/DynamicSamplingContextTest.php b/tests/Tracing/DynamicSamplingContextTest.php
index 0996aa7021..70424e0d04 100644
--- a/tests/Tracing/DynamicSamplingContextTest.php
+++ b/tests/Tracing/DynamicSamplingContextTest.php
@@ -8,8 +8,7 @@
 use Sentry\ClientInterface;
 use Sentry\NoOpClient;
 use Sentry\Options;
-use Sentry\State\Hub;
-use Sentry\State\Scope;
+use Sentry\State\IsolationScope;
 use Sentry\Tracing\DynamicSamplingContext;
 use Sentry\Tracing\PropagationContext;
 use Sentry\Tracing\TraceId;
@@ -91,16 +90,14 @@ public function testFromTransaction(): void
                 'environment' => 'test',
             ]));
 
-        $hub = new Hub($client);
-
         $transactionContext = new TransactionContext();
         $transactionContext->setName('foo');
 
-        $transaction = new Transaction($transactionContext, $hub);
+        $transaction = new Transaction($transactionContext);
         $transaction->getMetadata()->setSamplingRate(1.0);
         $transaction->getMetadata()->setSampleRand(0.5);
 
-        $samplingContext = DynamicSamplingContext::fromTransaction($transaction, $hub);
+        $samplingContext = DynamicSamplingContext::fromTransaction($transaction, $client);
 
         $this->assertSame((string) $transaction->getTraceId(), $samplingContext->get('trace_id'));
         $this->assertSame((string) $transaction->getMetaData()->getSamplingRate(), $samplingContext->get('sample_rate'));
@@ -114,15 +111,13 @@ public function testFromTransaction(): void
 
     public function testFromTransactionSourceUrl(): void
     {
-        $hub = new Hub(new NoOpClient());
-
         $transactionContext = new TransactionContext();
         $transactionContext->setName('/foo/bar/123');
         $transactionContext->setSource(TransactionSource::url());
 
-        $transaction = new Transaction($transactionContext, $hub);
+        $transaction = new Transaction($transactionContext);
 
-        $samplingContext = DynamicSamplingContext::fromTransaction($transaction, $hub);
+        $samplingContext = DynamicSamplingContext::fromTransaction($transaction, new NoOpClient());
 
         $this->assertNull($samplingContext->get('transaction'));
     }
@@ -140,7 +135,7 @@ public function testFromOptions(): void
         $propagationContext->setTraceId(new TraceId('21160e9b836d479f81611368b2aa3d2c'));
         $propagationContext->setSampleRand(0.5);
 
-        $scope = new Scope();
+        $scope = new IsolationScope();
         $scope->setPropagationContext($propagationContext);
 
         $samplingContext = DynamicSamplingContext::fromOptions($options, $scope);
@@ -161,7 +156,7 @@ public function testFromOptionsUsesConfiguredOrgIdOverDsnOrgId(): void
             'org_id' => 2,
         ]);
 
-        $scope = new Scope();
+        $scope = new IsolationScope();
         $samplingContext = DynamicSamplingContext::fromOptions($options, $scope);
 
         $this->assertSame('2', $samplingContext->get('org_id'));
@@ -173,7 +168,7 @@ public function testFromOptionsFallsBackToDsnOrgId(): void
             'dsn' => 'http://public@o1.example.com/1',
         ]);
 
-        $scope = new Scope();
+        $scope = new IsolationScope();
         $samplingContext = DynamicSamplingContext::fromOptions($options, $scope);
 
         $this->assertSame('1', $samplingContext->get('org_id'));
@@ -189,9 +184,8 @@ public function testFromTransactionUsesConfiguredOrgIdOverDsnOrgId(): void
                 'org_id' => 2,
             ]));
 
-        $hub = new Hub($client);
-        $transaction = new Transaction(new TransactionContext(), $hub);
-        $samplingContext = DynamicSamplingContext::fromTransaction($transaction, $hub);
+        $transaction = new Transaction(new TransactionContext());
+        $samplingContext = DynamicSamplingContext::fromTransaction($transaction, $client);
 
         $this->assertSame('2', $samplingContext->get('org_id'));
     }
@@ -205,9 +199,8 @@ public function testFromTransactionFallsBackToDsnOrgId(): void
                 'dsn' => 'http://public@o1.example.com/1',
             ]));
 
-        $hub = new Hub($client);
-        $transaction = new Transaction(new TransactionContext(), $hub);
-        $samplingContext = DynamicSamplingContext::fromTransaction($transaction, $hub);
+        $transaction = new Transaction(new TransactionContext());
+        $samplingContext = DynamicSamplingContext::fromTransaction($transaction, $client);
 
         $this->assertSame('1', $samplingContext->get('org_id'));
     }
diff --git a/tests/Tracing/GuzzleTracingMiddlewareTest.php b/tests/Tracing/GuzzleTracingMiddlewareTest.php
index becfa84a8e..61610f5cab 100644
--- a/tests/Tracing/GuzzleTracingMiddlewareTest.php
+++ b/tests/Tracing/GuzzleTracingMiddlewareTest.php
@@ -16,7 +16,8 @@
 use Sentry\EventType;
 use Sentry\Options;
 use Sentry\SentrySdk;
-use Sentry\State\Hub;
+use Sentry\State\GlobalScope;
+use Sentry\State\IsolationScope;
 use Sentry\State\Scope;
 use Sentry\Tracing\GuzzleTracingMiddleware;
 use Sentry\Tracing\SpanStatus;
@@ -33,16 +34,15 @@ public function testTraceCreatesBreadcrumbIfSpanIsNotSet(): void
                 'traces_sample_rate' => 0,
             ]));
 
-        $hub = new Hub($client);
-        SentrySdk::setCurrentHub($hub);
+        SentrySdk::init($client);
 
-        $transaction = $hub->startTransaction(TransactionContext::make());
+        $transaction = \Sentry\startTransaction(TransactionContext::make());
 
         $this->assertFalse($transaction->getSampled());
 
         $expectedPromiseResult = new Response();
 
-        $middleware = GuzzleTracingMiddleware::trace($hub);
+        $middleware = GuzzleTracingMiddleware::trace();
         $function = $middleware(static function () use ($expectedPromiseResult): PromiseInterface {
             return new FulfilledPromise($expectedPromiseResult);
         });
@@ -60,13 +60,11 @@ public function testTraceCreatesBreadcrumbIfSpanIsNotSet(): void
 
         $this->assertNull($transaction->getSpanRecorder());
 
-        $hub->configureScope(function (Scope $scope): void {
-            $event = Event::createEvent();
+        $event = Event::createEvent();
 
-            $scope->applyToEvent($event);
+        (new GlobalScope())->merge(SentrySdk::getIsolationScope())->applyToEvent($event);
 
-            $this->assertCount(1, $event->getBreadcrumbs());
-        });
+        $this->assertCount(1, $event->getBreadcrumbs());
     }
 
     public function testTraceCreatesBreadcrumbIfSpanIsRecorded(): void
@@ -78,16 +76,15 @@ public function testTraceCreatesBreadcrumbIfSpanIsRecorded(): void
                    'traces_sample_rate' => 1,
                ]));
 
-        $hub = new Hub($client);
-        SentrySdk::setCurrentHub($hub);
+        SentrySdk::init($client);
 
-        $transaction = $hub->startTransaction(TransactionContext::make());
+        $transaction = \Sentry\startTransaction(TransactionContext::make());
 
         $this->assertTrue($transaction->getSampled());
 
         $expectedPromiseResult = new Response();
 
-        $middleware = GuzzleTracingMiddleware::trace($hub);
+        $middleware = GuzzleTracingMiddleware::trace();
         $function = $middleware(static function () use ($expectedPromiseResult): PromiseInterface {
             return new FulfilledPromise($expectedPromiseResult);
         });
@@ -106,13 +103,61 @@ public function testTraceCreatesBreadcrumbIfSpanIsRecorded(): void
         $this->assertNotNull($transaction->getSpanRecorder());
         $this->assertCount(1, $transaction->getSpanRecorder()->getSpans());
 
-        $hub->configureScope(function (Scope $scope): void {
-            $event = Event::createEvent();
+        $event = Event::createEvent();
+
+        (new GlobalScope())->merge(SentrySdk::getIsolationScope())->applyToEvent($event);
 
-            $scope->applyToEvent($event);
+        $this->assertCount(1, $event->getBreadcrumbs());
+    }
 
-            $this->assertCount(1, $event->getBreadcrumbs());
+    public function testTraceUsesProvidedIsolationScope(): void
+    {
+        $client = $this->createMock(ClientInterface::class);
+        $client->expects($this->atLeastOnce())
+            ->method('getOptions')
+            ->willReturn(new Options([
+                'trace_propagation_targets' => [
+                    'www.example.com',
+                ],
+            ]));
+
+        SentrySdk::init($client);
+
+        $currentScope = SentrySdk::getIsolationScope();
+
+        $providedScope = new IsolationScope();
+        $providedScope->setClient($client);
+
+        $request = new Request('GET', 'https://www.example.com');
+        $expectedPromiseResult = new Response();
+
+        $middleware = GuzzleTracingMiddleware::trace($providedScope);
+        $function = $middleware(function (Request $request) use ($expectedPromiseResult): PromiseInterface {
+            $this->assertNotEmpty($request->getHeader('sentry-trace'));
+            $this->assertNotEmpty($request->getHeader('baggage'));
+
+            return new FulfilledPromise($expectedPromiseResult);
         });
+
+        /** @var PromiseInterface $promise */
+        $promise = $function($request, []);
+
+        try {
+            $promiseResult = $promise->wait();
+        } catch (\Throwable $exception) {
+            $promiseResult = $exception;
+        }
+
+        $this->assertSame($expectedPromiseResult, $promiseResult);
+
+        $currentEvent = Event::createEvent();
+        (new GlobalScope())->merge($currentScope)->applyToEvent($currentEvent);
+
+        $providedEvent = Event::createEvent();
+        (new GlobalScope())->merge($providedScope)->applyToEvent($providedEvent);
+
+        $this->assertCount(0, $currentEvent->getBreadcrumbs());
+        $this->assertCount(1, $providedEvent->getBreadcrumbs());
     }
 
     /**
@@ -125,12 +170,11 @@ public function testTraceHeaders(Request $request, Options $options, bool $heade
             ->method('getOptions')
             ->willReturn($options);
 
-        $hub = new Hub($client);
-        SentrySdk::setCurrentHub($hub);
+        SentrySdk::init($client);
 
         $expectedPromiseResult = new Response();
 
-        $middleware = GuzzleTracingMiddleware::trace($hub);
+        $middleware = GuzzleTracingMiddleware::trace();
         $function = $middleware(function (Request $request) use ($expectedPromiseResult, $headersShouldBePresent): PromiseInterface {
             if ($headersShouldBePresent) {
                 $this->assertNotEmpty($request->getHeader('sentry-trace'));
@@ -157,16 +201,15 @@ public function testTraceHeadersWithTransaction(Request $request, Options $optio
             ->method('getOptions')
             ->willReturn($options);
 
-        $hub = new Hub($client);
-        SentrySdk::setCurrentHub($hub);
+        SentrySdk::init($client);
 
-        $transaction = $hub->startTransaction(new TransactionContext());
+        $transaction = \Sentry\startTransaction(new TransactionContext());
 
-        $hub->setSpan($transaction);
+        SentrySdk::getIsolationScope()->setSpan($transaction);
 
         $expectedPromiseResult = new Response();
 
-        $middleware = GuzzleTracingMiddleware::trace($hub);
+        $middleware = GuzzleTracingMiddleware::trace();
         $function = $middleware(function (Request $request) use ($expectedPromiseResult, $headersShouldBePresent): PromiseInterface {
             if ($headersShouldBePresent) {
                 $this->assertNotEmpty($request->getHeader('sentry-trace'));
@@ -201,11 +244,10 @@ public function testTraceHeadersAreNotAddedWhenExternalPropagationContextIsActiv
                 'trace_propagation_targets' => null,
             ]));
 
-        $hub = new Hub($client);
-        SentrySdk::setCurrentHub($hub);
+        SentrySdk::init($client);
         $expectedPromiseResult = new Response();
 
-        $middleware = GuzzleTracingMiddleware::trace($hub);
+        $middleware = GuzzleTracingMiddleware::trace();
         $function = $middleware(function (Request $request) use ($expectedPromiseResult): PromiseInterface {
             $this->assertEmpty($request->getHeader('sentry-trace'));
             $this->assertEmpty($request->getHeader('baggage'));
@@ -329,17 +371,15 @@ public function testTrace(Request $request, $expectedPromiseResult, array $expec
                 ],
             ]));
 
-        $hub = new Hub($client);
-        SentrySdk::setCurrentHub($hub);
+        SentrySdk::init($client);
+        $scope = SentrySdk::getIsolationScope();
 
         $client->expects($this->once())
             ->method('captureEvent')
-            ->with($this->callback(function (Event $eventArg) use ($hub, $request, $expectedPromiseResult, $expectedBreadcrumbData, $expectedSpanData): bool {
+            ->with($this->callback(function (Event $eventArg) use ($scope, $request, $expectedPromiseResult, $expectedBreadcrumbData, $expectedSpanData): bool {
                 $this->assertSame(EventType::transaction(), $eventArg->getType());
 
-                $hub->configureScope(static function (Scope $scope) use ($eventArg): void {
-                    $scope->applyToEvent($eventArg);
-                });
+                (new GlobalScope())->merge($scope)->applyToEvent($eventArg);
 
                 $spans = $eventArg->getSpans();
                 $breadcrumbs = $eventArg->getBreadcrumbs();
@@ -372,11 +412,11 @@ public function testTrace(Request $request, $expectedPromiseResult, array $expec
                 return true;
             }));
 
-        $transaction = $hub->startTransaction(new TransactionContext());
+        $transaction = \Sentry\startTransaction(new TransactionContext());
 
-        $hub->setSpan($transaction);
+        $scope->setSpan($transaction);
 
-        $middleware = GuzzleTracingMiddleware::trace($hub);
+        $middleware = GuzzleTracingMiddleware::trace();
         $function = $middleware(function (Request $request) use ($expectedPromiseResult): PromiseInterface {
             $this->assertNotEmpty($request->getHeader('sentry-trace'));
             $this->assertNotEmpty($request->getHeader('baggage'));
diff --git a/tests/Tracing/PropagationContextTest.php b/tests/Tracing/PropagationContextTest.php
index beefa0cb1d..8d24219138 100644
--- a/tests/Tracing/PropagationContextTest.php
+++ b/tests/Tracing/PropagationContextTest.php
@@ -5,8 +5,10 @@
 namespace Sentry\Tests\Tracing;
 
 use PHPUnit\Framework\TestCase;
+use Sentry\ClientInterface;
 use Sentry\Options;
-use Sentry\State\Scope;
+use Sentry\SentrySdk;
+use Sentry\State\IsolationScope;
 use Sentry\Tracing\DynamicSamplingContext;
 use Sentry\Tracing\PropagationContext;
 use Sentry\Tracing\SpanId;
@@ -113,6 +115,29 @@ public function testToBaggage(): void
         $this->assertSame('sentry-trace_id=566e3688a61d4bc888951642d6f14a19', $propagationContext->toBaggage());
     }
 
+    public function testToBaggageUsesCurrentClientAndIsolationScope(): void
+    {
+        $propagationContext = PropagationContext::fromDefaults();
+        $propagationContext->setTraceId(new TraceId('566e3688a61d4bc888951642d6f14a19'));
+        $propagationContext->setSampleRand(0.25);
+
+        $client = $this->createMock(ClientInterface::class);
+        $client->expects($this->once())
+            ->method('getOptions')
+            ->willReturn(new Options([
+                'release' => '1.0.0',
+                'environment' => 'development',
+            ]));
+
+        SentrySdk::getGlobalScope()->setClient($client);
+        SentrySdk::getCurrentRuntimeContext()->setIsolationScope(new IsolationScope($propagationContext));
+
+        $this->assertSame(
+            'sentry-trace_id=566e3688a61d4bc888951642d6f14a19,sentry-sample_rand=0.25,sentry-release=1.0.0,sentry-environment=development',
+            $propagationContext->toBaggage()
+        );
+    }
+
     public function testGetTraceContext(): void
     {
         $propagationContext = PropagationContext::fromDefaults();
@@ -199,7 +224,7 @@ public function testGettersAndSetters(string $getterMethod, string $setterMethod
 
     public static function gettersAndSettersDataProvider(): array
     {
-        $scope = new Scope();
+        $scope = new IsolationScope();
         $options = new Options([
             'dsn' => 'http://public@example.com/sentry/1',
             'release' => '1.0.0',
diff --git a/tests/Tracing/SpanTest.php b/tests/Tracing/SpanTest.php
index cf8956172d..251a9eaf86 100644
--- a/tests/Tracing/SpanTest.php
+++ b/tests/Tracing/SpanTest.php
@@ -5,6 +5,10 @@
 namespace Sentry\Tests\Tracing;
 
 use PHPUnit\Framework\TestCase;
+use Sentry\Event;
+use Sentry\SentrySdk;
+use Sentry\State\GlobalScope;
+use Sentry\State\IsolationScope;
 use Sentry\Tests\TestUtil\ClockMock;
 use Sentry\Tracing\Span;
 use Sentry\Tracing\SpanContext;
@@ -73,6 +77,28 @@ public function testStartChild(): void
         $this->assertSame($spanContext1->getTraceId(), $span2->getTraceId());
     }
 
+    public function testSetHttpStatusWritesResponseContextToCurrentIsolationScopeOnly(): void
+    {
+        $globalScope = SentrySdk::getGlobalScope();
+        $globalScope->setContext('response', [
+            'status_code' => 201,
+        ]);
+
+        $isolationScope = new IsolationScope();
+        SentrySdk::getCurrentRuntimeContext()->setIsolationScope($isolationScope);
+
+        $span = new Span();
+        $span->setHttpStatus(404);
+
+        $isolationEvent = (new GlobalScope())->merge($isolationScope)->applyToEvent(Event::createEvent());
+        $this->assertNotNull($isolationEvent);
+        $this->assertSame(404, $isolationEvent->getContexts()['response']['status_code']);
+
+        $globalEvent = $globalScope->merge(new IsolationScope())->applyToEvent(Event::createEvent());
+        $this->assertNotNull($globalEvent);
+        $this->assertSame(201, $globalEvent->getContexts()['response']['status_code']);
+    }
+
     /**
      * @dataProvider toTraceparentDataProvider
      */
diff --git a/tests/Tracing/StrictTraceContinuationTest.php b/tests/Tracing/StrictTraceContinuationTest.php
index 6de0a3a962..88440b5da4 100644
--- a/tests/Tracing/StrictTraceContinuationTest.php
+++ b/tests/Tracing/StrictTraceContinuationTest.php
@@ -8,7 +8,6 @@
 use Sentry\ClientInterface;
 use Sentry\Options;
 use Sentry\SentrySdk;
-use Sentry\State\Hub;
 use Sentry\Tracing\PropagationContext;
 use Sentry\Tracing\TransactionContext;
 
@@ -26,7 +25,7 @@ public function testPropagationContext(Options $options, string $baggage, bool $
             ->method('getOptions')
             ->willReturn($options);
 
-        SentrySdk::setCurrentHub(new Hub($client));
+        SentrySdk::init($client);
 
         $contexts = [
             PropagationContext::fromHeaders(self::SENTRY_TRACE_HEADER, $baggage),
@@ -56,7 +55,7 @@ public function testTransactionContext(Options $options, string $baggage, bool $
             ->method('getOptions')
             ->willReturn($options);
 
-        SentrySdk::setCurrentHub(new Hub($client));
+        SentrySdk::init($client);
 
         $contexts = [
             TransactionContext::fromHeaders(self::SENTRY_TRACE_HEADER, $baggage),
diff --git a/tests/Tracing/TransactionContextTest.php b/tests/Tracing/TransactionContextTest.php
index 678d8d8979..9d2b3dd61d 100644
--- a/tests/Tracing/TransactionContextTest.php
+++ b/tests/Tracing/TransactionContextTest.php
@@ -10,7 +10,6 @@
 use Sentry\NoOpClient;
 use Sentry\Options;
 use Sentry\SentrySdk;
-use Sentry\State\Hub;
 use Sentry\Tracing\DynamicSamplingContext;
 use Sentry\Tracing\SpanId;
 use Sentry\Tracing\TraceId;
@@ -182,7 +181,7 @@ public function testInvalidSampleRandIsLogged(): void
         $client->method('getOptions')
             ->willReturn(new Options(['logger' => $logger]));
 
-        SentrySdk::setCurrentHub(new Hub($client));
+        SentrySdk::init($client);
 
         try {
             TransactionContext::fromHeaders(
@@ -190,7 +189,7 @@ public function testInvalidSampleRandIsLogged(): void
                 'sentry-sample_rand=-1.0'
             );
         } finally {
-            SentrySdk::setCurrentHub(new Hub(new NoOpClient()));
+            SentrySdk::init(new NoOpClient());
         }
     }
 
diff --git a/tests/Tracing/TransactionSamplerTest.php b/tests/Tracing/TransactionSamplerTest.php
new file mode 100644
index 0000000000..9118e9c121
--- /dev/null
+++ b/tests/Tracing/TransactionSamplerTest.php
@@ -0,0 +1,323 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Sentry\Tests\Tracing;
+
+use PHPUnit\Framework\TestCase;
+use Sentry\Options;
+use Sentry\Tracing\DynamicSamplingContext;
+use Sentry\Tracing\SamplingContext;
+use Sentry\Tracing\Transaction;
+use Sentry\Tracing\TransactionContext;
+use Sentry\Tracing\TransactionMetadata;
+use Sentry\Tracing\TransactionSampler;
+
+final class TransactionSamplerTest extends TestCase
+{
+    /**
+     * @dataProvider sampleTransactionDataProvider
+     */
+    public function testSampleTransaction(Options $options, TransactionContext $transactionContext, bool $expectedSampled): void
+    {
+        $transaction = $this->sampleTransaction($options, $transactionContext);
+
+        $this->assertSame($expectedSampled, $transaction->getSampled());
+    }
+
+    public function testIgnoresBaggageSampleRateWithoutSentryTrace(): void
+    {
+        $transactionContext = TransactionContext::fromHeaders('', 'sentry-sample_rate=1');
+        $transaction = $this->sampleTransaction(new Options([
+            'traces_sample_rate' => 0.0,
+        ]), $transactionContext);
+
+        $this->assertFalse($transaction->getSampled());
+    }
+
+    public static function sampleTransactionDataProvider(): iterable
+    {
+        yield 'Acceptable float value returned from traces_sampler' => [
+            new Options([
+                'traces_sampler' => static function (): float {
+                    return 1.0;
+                },
+            ]),
+            new TransactionContext(),
+            true,
+        ];
+
+        yield 'Acceptable but too low float value returned from traces_sampler' => [
+            new Options([
+                'traces_sampler' => static function (): float {
+                    return 0.0;
+                },
+            ]),
+            new TransactionContext(),
+            false,
+        ];
+
+        yield 'Acceptable integer value returned from traces_sampler' => [
+            new Options([
+                'traces_sampler' => static function (): int {
+                    return 1;
+                },
+            ]),
+            new TransactionContext(),
+            true,
+        ];
+
+        yield 'Acceptable but too low integer value returned from traces_sampler' => [
+            new Options([
+                'traces_sampler' => static function (): int {
+                    return 0;
+                },
+            ]),
+            new TransactionContext(),
+            false,
+        ];
+
+        yield 'Acceptable float value returned from traces_sample_rate' => [
+            new Options([
+                'traces_sample_rate' => 1.0,
+            ]),
+            new TransactionContext(),
+            true,
+        ];
+
+        yield 'Acceptable but too low float value returned from traces_sample_rate' => [
+            new Options([
+                'traces_sample_rate' => 0.0,
+            ]),
+            new TransactionContext(),
+            false,
+        ];
+
+        yield 'Acceptable integer value returned from traces_sample_rate' => [
+            new Options([
+                'traces_sample_rate' => 1,
+            ]),
+            new TransactionContext(),
+            true,
+        ];
+
+        yield 'Acceptable but too low integer value returned from traces_sample_rate' => [
+            new Options([
+                'traces_sample_rate' => 0,
+            ]),
+            new TransactionContext(),
+            false,
+        ];
+
+        yield 'Acceptable but too low value returned from traces_sample_rate which is preferred over sample_rate' => [
+            new Options([
+                'sample_rate' => 1.0,
+                'traces_sample_rate' => 0.0,
+            ]),
+            new TransactionContext(),
+            false,
+        ];
+
+        yield 'Acceptable value returned from traces_sample_rate which is preferred over sample_rate' => [
+            new Options([
+                'sample_rate' => 0.0,
+                'traces_sample_rate' => 1.0,
+            ]),
+            new TransactionContext(),
+            true,
+        ];
+
+        yield 'Acceptable value returned from SamplingContext::getParentSampled() which is preferred over traces_sample_rate (x1)' => [
+            new Options([
+                'traces_sample_rate' => 0.5,
+            ]),
+            new TransactionContext(TransactionContext::DEFAULT_NAME, true),
+            true,
+        ];
+
+        yield 'Acceptable value returned from SamplingContext::getParentSampled() which is preferred over traces_sample_rate (x2)' => [
+            new Options([
+                'traces_sample_rate' => 1.0,
+            ]),
+            new TransactionContext(TransactionContext::DEFAULT_NAME, false),
+            false,
+        ];
+
+        yield 'Invalid incoming sample_rand is ignored' => [
+            new Options([
+                'traces_sample_rate' => 1.0,
+            ]),
+            TransactionContext::fromHeaders(
+                '566e3688a61d4bc888951642d6f14a19-566e3688a61d4bc8',
+                'sentry-sample_rand=2.0'
+            ),
+            true,
+        ];
+
+        yield 'Out of range sample rate returned from traces_sampler (lower than minimum)' => [
+            new Options([
+                'traces_sampler' => static function (): float {
+                    return -1.0;
+                },
+            ]),
+            new TransactionContext(TransactionContext::DEFAULT_NAME, false),
+            false,
+        ];
+
+        yield 'Out of range sample rate returned from traces_sampler (greater than maximum)' => [
+            new Options([
+                'traces_sampler' => static function (): float {
+                    return 1.1;
+                },
+            ]),
+            new TransactionContext(TransactionContext::DEFAULT_NAME, false),
+            false,
+        ];
+
+        yield 'Invalid type returned from traces_sampler' => [
+            new Options([
+                'traces_sampler' => static function (): string {
+                    return 'foo';
+                },
+            ]),
+            new TransactionContext(TransactionContext::DEFAULT_NAME, false),
+            false,
+        ];
+    }
+
+    public function testDoesNothingIfTracingIsNotEnabled(): void
+    {
+        $transaction = $this->sampleTransaction(new Options(), new TransactionContext());
+
+        $this->assertFalse($transaction->getSampled());
+    }
+
+    public function testPassesCustomSamplingContextToTracesSampler(): void
+    {
+        $customSamplingContext = ['a' => 'b'];
+        $samplerInvoked = false;
+
+        $this->sampleTransaction(new Options([
+            'traces_sampler' => function (SamplingContext $samplingContext) use ($customSamplingContext, &$samplerInvoked): float {
+                $this->assertSame($customSamplingContext, $samplingContext->getAdditionalContext());
+                $samplerInvoked = true;
+
+                return 1.0;
+            },
+        ]), new TransactionContext(), $customSamplingContext);
+
+        $this->assertTrue($samplerInvoked);
+    }
+
+    public function testStartsProfilerWithProfilesSampler(): void
+    {
+        $transaction = $this->sampleTransaction(new Options([
+            'traces_sample_rate' => 1.0,
+            'profiles_sampler' => static function (): float {
+                return 1.0;
+            },
+        ]), new TransactionContext());
+
+        $this->assertTrue($transaction->getSampled());
+        $this->assertNotNull($transaction->getProfiler());
+    }
+
+    public function testDoesNotStartProfilerWhenProfilesSamplerReturnsZero(): void
+    {
+        $transaction = $this->sampleTransaction(new Options([
+            'traces_sample_rate' => 1.0,
+            'profiles_sampler' => static function (): float {
+                return 0.0;
+            },
+        ]), new TransactionContext());
+
+        $this->assertTrue($transaction->getSampled());
+        $this->assertNull($transaction->getProfiler());
+    }
+
+    public function testPrefersProfilesSamplerOverProfilesSampleRate(): void
+    {
+        $transaction = $this->sampleTransaction(new Options([
+            'traces_sample_rate' => 1.0,
+            'profiles_sample_rate' => 1.0,
+            'profiles_sampler' => static function (): float {
+                return 0.0;
+            },
+        ]), new TransactionContext());
+
+        $this->assertTrue($transaction->getSampled());
+        $this->assertNull($transaction->getProfiler());
+    }
+
+    public function testPassesCustomSamplingContextToProfilesSampler(): void
+    {
+        $customSamplingContext = ['a' => 'b'];
+        $samplerInvoked = false;
+
+        $this->sampleTransaction(new Options([
+            'traces_sample_rate' => 1.0,
+            'profiles_sampler' => function (SamplingContext $samplingContext) use ($customSamplingContext, &$samplerInvoked): float {
+                $this->assertSame($customSamplingContext, $samplingContext->getAdditionalContext());
+                $samplerInvoked = true;
+
+                return 0.0;
+            },
+        ]), new TransactionContext(), $customSamplingContext);
+
+        $this->assertTrue($samplerInvoked);
+    }
+
+    public function testDoesNotStartProfilerWhenProfilesSamplerReturnsInvalidValue(): void
+    {
+        $transaction = $this->sampleTransaction(new Options([
+            'traces_sample_rate' => 1.0,
+            'profiles_sampler' => static function (): string {
+                return 'foo';
+            },
+        ]), new TransactionContext());
+
+        $this->assertTrue($transaction->getSampled());
+        $this->assertNull($transaction->getProfiler());
+    }
+
+    public function testDoesNotCallProfilesSamplerWhenTransactionIsNotSampled(): void
+    {
+        $profilesSamplerInvoked = false;
+
+        $transaction = $this->sampleTransaction(new Options([
+            'traces_sample_rate' => 0.0,
+            'profiles_sampler' => static function () use (&$profilesSamplerInvoked): float {
+                $profilesSamplerInvoked = true;
+
+                return 1.0;
+            },
+        ]), new TransactionContext());
+
+        $this->assertFalse($transaction->getSampled());
+        $this->assertFalse($profilesSamplerInvoked);
+        $this->assertNull($transaction->getProfiler());
+    }
+
+    public function testUpdatesTheDscSampleRate(): void
+    {
+        $dsc = DynamicSamplingContext::fromHeader('sentry-trace_id=d49d9bf66f13450b81f65bc51cf49c03,sentry-public_key=public');
+        $transactionMetaData = new TransactionMetadata(null, $dsc);
+        $transactionContext = new TransactionContext(TransactionContext::DEFAULT_NAME, null, $transactionMetaData);
+
+        $transaction = $this->sampleTransaction(new Options([
+            'traces_sampler' => static function (SamplingContext $samplingContext): float {
+                return 1.0;
+            },
+        ]), $transactionContext);
+
+        $this->assertSame('1', $transaction->getMetadata()->getDynamicSamplingContext()->get('sample_rate'));
+    }
+
+    /**
+     * @param array<string, mixed> $customSamplingContext
+     */
+    private function sampleTransaction(Options $options, TransactionContext $transactionContext, array $customSamplingContext = []): Transaction
+    {
+        return TransactionSampler::startTransaction($options, $transactionContext, $customSamplingContext);
+    }
+}
diff --git a/tests/Tracing/TransactionTest.php b/tests/Tracing/TransactionTest.php
index 76a2c3aab6..1727fb373c 100644
--- a/tests/Tracing/TransactionTest.php
+++ b/tests/Tracing/TransactionTest.php
@@ -10,13 +10,15 @@
 use Sentry\EventId;
 use Sentry\EventType;
 use Sentry\Options;
-use Sentry\State\Hub;
-use Sentry\State\HubInterface;
+use Sentry\SentrySdk;
+use Sentry\State\IsolationScope;
 use Sentry\Tests\TestUtil\ClockMock;
 use Sentry\Tracing\SpanContext;
 use Sentry\Tracing\Transaction;
 use Sentry\Tracing\TransactionContext;
 
+use function Sentry\startTransaction;
+
 /**
  * @group time-sensitive
  */
@@ -37,19 +39,18 @@ public function testFinish(): void
             ->method('getOptions')
             ->willReturn(new Options());
 
-        $hub = $this->createMock(HubInterface::class);
-        $hub->expects($this->once())
-            ->method('getClient')
-            ->willReturn($client);
+        SentrySdk::init($client);
 
-        $transaction = new Transaction($transactionContext, $hub);
+        $scope = SentrySdk::getIsolationScope();
+        $transaction = new Transaction($transactionContext, $scope);
+        SentrySdk::getCurrentRuntimeContext()->setIsolationScope(new IsolationScope());
         $transaction->initSpanRecorder();
 
         $span1 = $transaction->startChild(new SpanContext());
         $span2 = $transaction->startChild(new SpanContext());
         $span3 = $transaction->startChild(new SpanContext()); // This span isn't finished, so it should not be included in the event
 
-        $hub->expects($this->once())
+        $client->expects($this->once())
             ->method('captureEvent')
             ->with($this->callback(function (Event $eventArg) use ($transactionContext, $span1, $span2): bool {
                 $this->assertSame(EventType::transaction(), $eventArg->getType());
@@ -60,7 +61,7 @@ public function testFinish(): void
                 $this->assertSame([$span1, $span2], $eventArg->getSpans());
 
                 return true;
-            }))
+            }), null, $scope)
             ->willReturnCallback(static function (Event $eventArg) use (&$expectedEventId): EventId {
                 $expectedEventId = $eventArg->getId();
 
@@ -73,15 +74,18 @@ public function testFinish(): void
         $eventId = $transaction->finish();
 
         $this->assertSame($expectedEventId, $eventId);
+        $this->assertSame($expectedEventId, SentrySdk::getLastEventId());
     }
 
     public function testFinishDoesNothingIfSampledFlagIsNotTrue(): void
     {
-        $hub = $this->createMock(HubInterface::class);
-        $hub->expects($this->never())
+        $client = $this->createMock(ClientInterface::class);
+        $client->expects($this->never())
             ->method('captureEvent');
 
-        $transaction = new Transaction(new TransactionContext(), $hub);
+        SentrySdk::init($client);
+
+        $transaction = new Transaction(new TransactionContext());
         $transaction->finish();
     }
 
@@ -112,7 +116,9 @@ public function testTransactionIsSampledCorrectlyWhenTracingIsSetToZeroInOptions
                 ])
             );
 
-        $transaction = (new Hub($client))->startTransaction($context);
+        SentrySdk::init($client);
+
+        $transaction = startTransaction($context);
 
         $this->assertSame($expectedSampled, $transaction->getSampled());
     }
@@ -155,7 +161,9 @@ public function testTransactionIsNotSampledWhenTracingIsDisabledInOptions(Transa
                 ])
             );
 
-        $transaction = (new Hub($client))->startTransaction($context);
+        SentrySdk::init($client);
+
+        $transaction = startTransaction($context);
 
         $this->assertSame($expectedSampled, $transaction->getSampled());
     }
diff --git a/tests/phpt-oom/php84/out_of_memory_fatal_error_increases_memory_limit.phpt b/tests/phpt-oom/php84/out_of_memory_fatal_error_increases_memory_limit.phpt
index 35a32c8381..47364f8737 100644
--- a/tests/phpt-oom/php84/out_of_memory_fatal_error_increases_memory_limit.phpt
+++ b/tests/phpt-oom/php84/out_of_memory_fatal_error_increases_memory_limit.phpt
@@ -65,7 +65,7 @@ $options->setTransport($transport);
 
 $client = (new ClientBuilder($options))->getClient();
 
-SentrySdk::init()->bindClient($client);
+SentrySdk::init($client);
 
 echo 'Before OOM memory limit: ' . \ini_get('memory_limit');
 
diff --git a/tests/phpt-oom/php85/out_of_memory_fatal_error_increases_memory_limit.phpt b/tests/phpt-oom/php85/out_of_memory_fatal_error_increases_memory_limit.phpt
index a547854dab..544929924c 100644
--- a/tests/phpt-oom/php85/out_of_memory_fatal_error_increases_memory_limit.phpt
+++ b/tests/phpt-oom/php85/out_of_memory_fatal_error_increases_memory_limit.phpt
@@ -65,7 +65,7 @@ $options->setTransport($transport);
 
 $client = (new ClientBuilder($options))->getClient();
 
-SentrySdk::init()->bindClient($client);
+SentrySdk::init($client);
 
 echo 'Before OOM memory limit: ' . \ini_get('memory_limit');
 
diff --git a/tests/phpt/error_handler_captures_errors_not_silencable_on_php_8_and_up.phpt b/tests/phpt/error_handler_captures_errors_not_silencable_on_php_8_and_up.phpt
index fe1cf65e24..5fb8643950 100644
--- a/tests/phpt/error_handler_captures_errors_not_silencable_on_php_8_and_up.phpt
+++ b/tests/phpt/error_handler_captures_errors_not_silencable_on_php_8_and_up.phpt
@@ -57,7 +57,7 @@ $client = ClientBuilder::create($options)
     ->setTransport($transport)
     ->getClient();
 
-SentrySdk::getCurrentHub()->bindClient($client);
+SentrySdk::init($client);
 
 echo 'Triggering "silenced" E_USER_ERROR error' . PHP_EOL;
 
diff --git a/tests/phpt/error_handler_respects_capture_silenced_errors_option.phpt b/tests/phpt/error_handler_respects_capture_silenced_errors_option.phpt
index 11ffa7c3c8..b0179c1889 100644
--- a/tests/phpt/error_handler_respects_capture_silenced_errors_option.phpt
+++ b/tests/phpt/error_handler_respects_capture_silenced_errors_option.phpt
@@ -50,7 +50,7 @@ $client = ClientBuilder::create($options)
     ->setTransport($transport)
     ->getClient();
 
-SentrySdk::getCurrentHub()->bindClient($client);
+SentrySdk::init($client);
 
 echo 'Triggering silenced error' . PHP_EOL;
 
diff --git a/tests/phpt/error_handler_respects_current_error_reporting_level.phpt b/tests/phpt/error_handler_respects_current_error_reporting_level.phpt
index f6017b8a55..09e0ab2416 100644
--- a/tests/phpt/error_handler_respects_current_error_reporting_level.phpt
+++ b/tests/phpt/error_handler_respects_current_error_reporting_level.phpt
@@ -56,7 +56,7 @@ $client = ClientBuilder::create($options)
     ->setTransport($transport)
     ->getClient();
 
-SentrySdk::getCurrentHub()->bindClient($client);
+SentrySdk::init($client);
 
 echo 'Triggering E_USER_NOTICE with error reporting on E_ALL' . PHP_EOL;
 
diff --git a/tests/phpt/error_handler_respects_error_types_option_regardless_of_error_reporting.phpt b/tests/phpt/error_handler_respects_error_types_option_regardless_of_error_reporting.phpt
index 592ebaa37d..fd610d824c 100644
--- a/tests/phpt/error_handler_respects_error_types_option_regardless_of_error_reporting.phpt
+++ b/tests/phpt/error_handler_respects_error_types_option_regardless_of_error_reporting.phpt
@@ -50,7 +50,7 @@ $client = ClientBuilder::create($options)
     ->setTransport($transport)
     ->getClient();
 
-SentrySdk::getCurrentHub()->bindClient($client);
+SentrySdk::init($client);
 
 echo 'Triggering E_USER_NOTICE error' . PHP_EOL;
 
diff --git a/tests/phpt/error_listener_integration_respects_error_types_option.phpt b/tests/phpt/error_listener_integration_respects_error_types_option.phpt
index 20d413ecde..db00f7b26e 100644
--- a/tests/phpt/error_listener_integration_respects_error_types_option.phpt
+++ b/tests/phpt/error_listener_integration_respects_error_types_option.phpt
@@ -56,7 +56,7 @@ $client = (new ClientBuilder($options))
     ->setTransport($transport)
     ->getClient();
 
-SentrySdk::getCurrentHub()->bindClient($client);
+SentrySdk::init($client);
 
 trigger_error('Error thrown', E_USER_NOTICE);
 trigger_error('Error thrown', E_USER_WARNING);
diff --git a/tests/phpt/php84/error_handler_captures_fatal_error.phpt b/tests/phpt/php84/error_handler_captures_fatal_error.phpt
index 9225fbafe1..349c6e6613 100644
--- a/tests/phpt/php84/error_handler_captures_fatal_error.phpt
+++ b/tests/phpt/php84/error_handler_captures_fatal_error.phpt
@@ -53,7 +53,7 @@ $client = ClientBuilder::create($options)
     ->setTransport($transport)
     ->getClient();
 
-SentrySdk::getCurrentHub()->bindClient($client);
+SentrySdk::init($client);
 
 $errorHandler = ErrorHandler::registerOnceErrorHandler();
 $errorHandler->addErrorHandlerListener(static function (): void {
diff --git a/tests/phpt/php84/fatal_error_integration_captures_fatal_error.phpt b/tests/phpt/php84/fatal_error_integration_captures_fatal_error.phpt
index 7b76f6fedb..9fafb91883 100644
--- a/tests/phpt/php84/fatal_error_integration_captures_fatal_error.phpt
+++ b/tests/phpt/php84/fatal_error_integration_captures_fatal_error.phpt
@@ -58,7 +58,7 @@ $client = (new ClientBuilder($options))
     ->setTransport($transport)
     ->getClient();
 
-SentrySdk::getCurrentHub()->bindClient($client);
+SentrySdk::init($client);
 
 final class TestClass implements \JsonSerializable
 {
diff --git a/tests/phpt/php84/fatal_error_integration_respects_error_types_option.phpt b/tests/phpt/php84/fatal_error_integration_respects_error_types_option.phpt
index 56620b1c03..f215caeef8 100644
--- a/tests/phpt/php84/fatal_error_integration_respects_error_types_option.phpt
+++ b/tests/phpt/php84/fatal_error_integration_respects_error_types_option.phpt
@@ -59,7 +59,7 @@ $client = (new ClientBuilder($options))
     ->setTransport($transport)
     ->getClient();
 
-SentrySdk::getCurrentHub()->bindClient($client);
+SentrySdk::init($client);
 
 final class TestClass implements \JsonSerializable
 {
diff --git a/tests/phpt/php85/error_handler_captures_fatal_error.phpt b/tests/phpt/php85/error_handler_captures_fatal_error.phpt
index 03f77c5891..594ad434ab 100644
--- a/tests/phpt/php85/error_handler_captures_fatal_error.phpt
+++ b/tests/phpt/php85/error_handler_captures_fatal_error.phpt
@@ -53,7 +53,7 @@ $client = ClientBuilder::create($options)
     ->setTransport($transport)
     ->getClient();
 
-SentrySdk::getCurrentHub()->bindClient($client);
+SentrySdk::init($client);
 
 $errorHandler = ErrorHandler::registerOnceErrorHandler();
 $errorHandler->addErrorHandlerListener(static function (): void {
diff --git a/tests/phpt/php85/fatal_error_integration_captures_fatal_error.phpt b/tests/phpt/php85/fatal_error_integration_captures_fatal_error.phpt
index b6c62b636c..8911b0b46d 100644
--- a/tests/phpt/php85/fatal_error_integration_captures_fatal_error.phpt
+++ b/tests/phpt/php85/fatal_error_integration_captures_fatal_error.phpt
@@ -58,7 +58,7 @@ $client = (new ClientBuilder($options))
     ->setTransport($transport)
     ->getClient();
 
-SentrySdk::getCurrentHub()->bindClient($client);
+SentrySdk::init($client);
 
 final class TestClass implements \JsonSerializable
 {
diff --git a/tests/phpt/php85/fatal_error_integration_respects_error_types_option.phpt b/tests/phpt/php85/fatal_error_integration_respects_error_types_option.phpt
index dbf4e8356f..6928a5de52 100644
--- a/tests/phpt/php85/fatal_error_integration_respects_error_types_option.phpt
+++ b/tests/phpt/php85/fatal_error_integration_respects_error_types_option.phpt
@@ -59,7 +59,7 @@ $client = (new ClientBuilder($options))
     ->setTransport($transport)
     ->getClient();
 
-SentrySdk::getCurrentHub()->bindClient($client);
+SentrySdk::init($client);
 
 final class TestClass implements \JsonSerializable
 {
diff --git a/tests/phpt/test_callable_serialization.phpt b/tests/phpt/test_callable_serialization.phpt
index ff5a2d79e4..4806cf053a 100644
--- a/tests/phpt/test_callable_serialization.phpt
+++ b/tests/phpt/test_callable_serialization.phpt
@@ -19,6 +19,8 @@ use Sentry\Transport\Result;
 use Sentry\Transport\ResultStatus;
 use Sentry\Transport\TransportInterface;
 
+use function Sentry\captureException;
+
 $vendor = __DIR__;
 
 while (!file_exists($vendor . '/vendor')) {
@@ -51,11 +53,11 @@ $client = ClientBuilder::create($options)
     ->setTransport($transport)
     ->getClient();
 
-SentrySdk::getCurrentHub()->bindClient($client);
+SentrySdk::init($client);
 
 class Foo {
     function __construct(string $bar) {
-        SentrySdk::getCurrentHub()->captureException(new Exception('doh!'));
+        captureException(new Exception('doh!'));
     }
 }