diff --git a/README.md b/README.md
index 34e3b81..16e55cc 100644
--- a/README.md
+++ b/README.md
@@ -286,6 +286,8 @@ $perfbase->setAttribute('cache_hit_ratio', '0.85');
 #### `submitTrace(): SubmitResult`
 Submit collected profiling data to Perfbase. Resets the session on success; preserves trace state on failure so callers can decide whether to retry or discard.
 
+The SDK sends the exact raw bytes returned by `perfbase_get_data()` as the request body. It adds the payload encoding version and client-created timestamp as HTTP headers; it does not JSON-wrap or base64-encode the trace payload.
+
 The returned `SubmitResult` provides:
 - `isSuccess(): bool` — delivery confirmed
 - `isRetryable(): bool` — transient failure (network error, 429, 5xx)
@@ -303,7 +305,7 @@ if (!$result->isSuccess()) {
 ```
 
 #### `getTraceData(string $spanName = ''): string`
-Retrieve raw trace data (useful for debugging or custom processing).
+Retrieve the raw Brotli-compressed MessagePack trace payload produced by the extension (useful for debugging or custom processing).
 
 ```php
 $rawData = $perfbase->getTraceData();
diff --git a/perfbase_extension_stubs.php b/perfbase_extension_stubs.php
index b54d7f9..c9c0ba1 100644
--- a/perfbase_extension_stubs.php
+++ b/perfbase_extension_stubs.php
@@ -65,3 +65,16 @@ function perfbase_get_data(): string
         return '';
     }
 }
+
+if (!function_exists('perfbase_get_version')) {
+    /**
+     * Retrieves the encoding version for collected profiling data.
+     *
+     * @return int
+     */
+    function perfbase_get_version(): int
+    {
+        // Stub only—no implementation needed
+        return 1;
+    }
+}
diff --git a/src/Extension/ExtensionInterface.php b/src/Extension/ExtensionInterface.php
index f59a5af..d6814cd 100644
--- a/src/Extension/ExtensionInterface.php
+++ b/src/Extension/ExtensionInterface.php
@@ -33,6 +33,13 @@ public function stopSpan(string $spanName): void;
      */
     public function getSpanData(string $spanName = ''): string;
 
+    /**
+     * Retrieves the encoding version for the current trace payload format.
+     *
+     * @return int
+     */
+    public function getVersion(): int;
+
     /**
      * Sets an attribute for a specific span
      * @param string $key
@@ -46,4 +53,4 @@ public function setAttribute(string $key, string $value): void;
      * @return void
      */
     public function reset(): void;
-}
\ No newline at end of file
+}
diff --git a/src/Extension/PerfbaseExtension.php b/src/Extension/PerfbaseExtension.php
index ee59b76..b821051 100644
--- a/src/Extension/PerfbaseExtension.php
+++ b/src/Extension/PerfbaseExtension.php
@@ -45,6 +45,11 @@ public function getSpanData(string $spanName = ''): string
         return perfbase_get_data();
     }
 
+    public function getVersion(): int
+    {
+        return perfbase_get_version();
+    }
+
     public function setAttribute(string $key, string $value): void
     {
         perfbase_set_attribute($key, $value);
@@ -54,4 +59,4 @@ public function reset(): void
     {
         perfbase_reset();
     }
-}
\ No newline at end of file
+}
diff --git a/src/Http/ApiClient.php b/src/Http/ApiClient.php
index 3b5644c..45cd353 100644
--- a/src/Http/ApiClient.php
+++ b/src/Http/ApiClient.php
@@ -34,7 +34,6 @@ public function __construct(Config $config, ?HttpClientInterface $httpClient = n
             'Authorization' => 'Bearer ' . $this->config->api_key,
             'Accept' => 'application/json',
             'User-Agent' => sprintf('Perfbase-PHP-SDK/%s', Perfbase::VERSION),
-            'Content-Type' => 'application/json',
             'Connection' => 'keep-alive',
         ];
 
@@ -59,11 +58,13 @@ public function __construct(Config $config, ?HttpClientInterface $httpClient = n
      * Submits a trace to the Perfbase API
      *
      * @param string $perfData Data to send in the request body
+     * @param int $payloadVersion Payload encoding version. Defaults to `1` for backwards compatibility.
+     * @param string|null $clientCreatedAt Trace creation timestamp in ISO 8601 UTC
      * @return SubmitResult
      */
-    public function submitTrace(string $perfData): SubmitResult
+    public function submitTrace(string $perfData, int $payloadVersion = 1, ?string $clientCreatedAt = null): SubmitResult
     {
-        return $this->submit('/v1/submit', $perfData);
+        return $this->submit('/v1/submit', $perfData, $payloadVersion, $clientCreatedAt);
     }
 
     /**
@@ -71,12 +72,22 @@ public function submitTrace(string $perfData): SubmitResult
      *
      * @param string $endpoint API endpoint to send the request to
      * @param string $perfData Data to send in the request body
+     * @param int $payloadVersion Payload encoding version
+     * @param string|null $clientCreatedAt Trace creation timestamp in ISO 8601 UTC
      * @return SubmitResult
      */
-    private function submit(string $endpoint, string $perfData): SubmitResult
+    private function submit(string $endpoint, string $perfData, int $payloadVersion, ?string $clientCreatedAt = null): SubmitResult
     {
+        $headers = $this->defaultHeaders;
+        $headers['Content-Type'] = 'application/octet-stream';
+        $headers['X-Perfbase-Payload-Version'] = (string) $payloadVersion;
+
+        if ($clientCreatedAt !== null) {
+            $headers['X-Perfbase-Client-Created-At'] = $clientCreatedAt;
+        }
+
         $options = [
-            'headers' => $this->defaultHeaders,
+            'headers' => $headers,
             'body' => $perfData,
         ];
 
diff --git a/src/Perfbase.php b/src/Perfbase.php
index 6bc2c59..5176909 100644
--- a/src/Perfbase.php
+++ b/src/Perfbase.php
@@ -3,6 +3,7 @@
 namespace Perfbase\SDK;
 
 use Perfbase\SDK\Exception\PerfbaseExtensionException;
+use Perfbase\SDK\Exception\PerfbaseException;
 use Perfbase\SDK\Exception\PerfbaseInvalidConfigException;
 use Perfbase\SDK\Exception\PerfbaseInvalidSpanException;
 use Perfbase\SDK\Extension\ExtensionInterface;
@@ -24,7 +25,7 @@ class Perfbase
     /**
      * The version of the Perfbase SDK
      */
-    public const VERSION = '1.0.0';
+    public const VERSION = '1.1.0';
 
     /**
      * The default span name used when starting a profiling session
@@ -167,9 +168,22 @@ public function setFlags(int $flags): void
      */
     public function submitTrace(): SubmitResult
     {
-        $payload = TracePayloadFactory::build($this->getTraceData());
+        $traceData = $this->getTraceData();
 
-        $result = $this->apiClient->submitTrace($payload);
+        if ($traceData === '') {
+            throw new PerfbaseException('Extension returned empty trace data');
+        }
+
+        $payloadVersion = $this->extension->getVersion();
+        if ($payloadVersion <= 0) {
+            throw new PerfbaseException('Extension returned invalid encoding version');
+        }
+
+        $result = $this->apiClient->submitTrace(
+            $traceData,
+            $payloadVersion,
+            gmdate('Y-m-d\TH:i:s\Z')
+        );
 
         if ($result->isSuccess()) {
             $this->reset();
diff --git a/src/TracePayloadFactory.php b/src/TracePayloadFactory.php
deleted file mode 100644
index a176362..0000000
--- a/src/TracePayloadFactory.php
+++ /dev/null
@@ -1,54 +0,0 @@
-<?php
-
-namespace Perfbase\SDK;
-
-use Perfbase\SDK\Exception\PerfbaseException;
-
-/**
- * Builds the submission payload from extension output.
- *
- * The extension returns JSON like {"v":1,"p":"<base64>"}. This factory
- * owns the outer envelope — it validates structure, injects the client
- * timestamp, and produces the final JSON body for the receiver.
- */
-class TracePayloadFactory
-{
-    /**
-     * Build a submission payload from raw extension output.
-     *
-     * @param string $extensionOutput Raw JSON from perfbase_get_data()
-     * @return string JSON payload ready for HTTP submission
-     * @throws PerfbaseException If the extension output is malformed
-     */
-    public static function build(string $extensionOutput): string
-    {
-        if ($extensionOutput === '') {
-            throw new PerfbaseException('Extension returned empty trace data');
-        }
-
-        /** @var mixed $decoded */
-        $decoded = json_decode($extensionOutput, true);
-
-        if (!is_array($decoded)) {
-            throw new PerfbaseException('Extension returned invalid JSON');
-        }
-
-        if (!isset($decoded['v']) || !is_int($decoded['v'])) {
-            throw new PerfbaseException('Extension output missing version field (v)');
-        }
-
-        if (!isset($decoded['p']) || !is_string($decoded['p'])) {
-            throw new PerfbaseException('Extension output missing payload field (p)');
-        }
-
-        // Inject client timestamp so the receiver knows when the trace was created
-        $decoded['d'] = gmdate('Y-m-d\TH:i:s\Z');
-
-        $json = json_encode($decoded);
-        if ($json === false) {
-            throw new PerfbaseException('Failed to encode submission payload');
-        }
-
-        return $json;
-    }
-}
diff --git a/src/Utils/ExtensionUtils.php b/src/Utils/ExtensionUtils.php
index bcc9c2c..7821d65 100644
--- a/src/Utils/ExtensionUtils.php
+++ b/src/Utils/ExtensionUtils.php
@@ -12,6 +12,7 @@ class ExtensionUtils
         'perfbase_disable',
         'perfbase_reset',
         'perfbase_get_data',
+        'perfbase_get_version',
         'perfbase_set_attribute'
     ];
 
diff --git a/tests/Extension/ExtensionTest.php b/tests/Extension/ExtensionTest.php
index 00f5d43..fdd23b9 100644
--- a/tests/Extension/ExtensionTest.php
+++ b/tests/Extension/ExtensionTest.php
@@ -92,6 +92,23 @@ public function testGetData(): void
         $this->assertIsString($data);
     }
 
+    /**
+     * @covers ::getVersion
+     */
+    public function testGetVersion(): void
+    {
+        if (!ExtensionUtils::perfbaseExtensionLoaded()) {
+            $this->markTestSkipped('Perfbase extension not loaded');
+        }
+
+        $extension = new PerfbaseExtension();
+
+        $version = $extension->getVersion();
+
+        $this->assertIsInt($version);
+        $this->assertGreaterThan(0, $version);
+    }
+
     /**
      * @covers ::reset
      */
@@ -125,4 +142,4 @@ public function testSetAttribute(): void
         
         $this->assertTrue(true); // If we get here, no exception was thrown
     }
-}
\ No newline at end of file
+}
diff --git a/tests/Http/ApiClientTest.php b/tests/Http/ApiClientTest.php
index cf72bcc..fe33067 100644
--- a/tests/Http/ApiClientTest.php
+++ b/tests/Http/ApiClientTest.php
@@ -67,7 +67,6 @@ public function testConstructorSetsCorrectHeaders(): void
 
         $this->assertEquals('Bearer test-api-key', $headers['Authorization']);
         $this->assertEquals('application/json', $headers['Accept']);
-        $this->assertEquals('application/json', $headers['Content-Type']);
         $this->assertEquals('keep-alive', $headers['Connection']);
         $this->assertStringContainsString('Perfbase-PHP-SDK/', $headers['User-Agent']);
     }
@@ -85,12 +84,13 @@ public function testSubmitTraceReturnsResult(): void
             ->once()
             ->with('/v1/submit', Mockery::on(function ($options) use ($testData) {
                 return isset($options['body']) && $options['body'] === $testData
-                    && isset($options['headers']) && is_array($options['headers']);
+                    && isset($options['headers']) && is_array($options['headers'])
+                    && $options['headers']['X-Perfbase-Payload-Version'] === '1';
             }))
             ->andReturn($expectedResult);
 
         $apiClient = new ApiClient($this->config, $this->mockHttpClient);
-        $result = $apiClient->submitTrace($testData);
+        $result = $apiClient->submitTrace($testData, 1);
 
         $this->assertTrue($result->isSuccess());
         $this->assertSame(202, $result->getStatusCode());
@@ -102,18 +102,46 @@ public function testSubmitTraceReturnsResult(): void
      */
     public function testSubmitTracePassesCorrectHeaders(): void
     {
+        $clientCreatedAt = '2026-04-08T12:00:00Z';
+
         $this->mockHttpClient->shouldReceive('post')
             ->once()
-            ->with('/v1/submit', Mockery::on(function ($options) {
+            ->with('/v1/submit', Mockery::on(function ($options) use ($clientCreatedAt) {
                 $headers = $options['headers'];
                 return $headers['Authorization'] === 'Bearer test-api-key'
                     && $headers['Accept'] === 'application/json'
-                    && $headers['Content-Type'] === 'application/json'
+                    && $headers['Content-Type'] === 'application/octet-stream'
                     && $headers['Connection'] === 'keep-alive'
+                    && $headers['X-Perfbase-Payload-Version'] === '1'
+                    && $headers['X-Perfbase-Client-Created-At'] === $clientCreatedAt
                     && isset($headers['User-Agent']);
             }))
             ->andReturn(SubmitResult::success());
 
+        $apiClient = new ApiClient($this->config, $this->mockHttpClient);
+        $result = $apiClient->submitTrace('test-data', 1, $clientCreatedAt);
+
+        $this->assertTrue($result->isSuccess());
+    }
+
+    /**
+     * @covers ::submitTrace
+     * @covers ::submit
+     */
+    public function testSubmitTraceMaintainsSingleArgumentCompatibility(): void
+    {
+        $this->mockHttpClient->shouldReceive('post')
+            ->once()
+            ->with('/v1/submit', Mockery::on(function ($options) {
+                $headers = $options['headers'];
+
+                return $options['body'] === 'test-data'
+                    && $headers['Content-Type'] === 'application/octet-stream'
+                    && $headers['X-Perfbase-Payload-Version'] === '1'
+                    && !isset($headers['X-Perfbase-Client-Created-At']);
+            }))
+            ->andReturn(SubmitResult::success());
+
         $apiClient = new ApiClient($this->config, $this->mockHttpClient);
         $result = $apiClient->submitTrace('test-data');
 
@@ -129,12 +157,15 @@ public function testSubmitTraceWithEmptyData(): void
         $this->mockHttpClient->shouldReceive('post')
             ->once()
             ->with('/v1/submit', Mockery::on(function ($options) {
-                return $options['body'] === '';
+                return $options['body'] === ''
+                    && $options['headers']['Content-Type'] === 'application/octet-stream'
+                    && $options['headers']['X-Perfbase-Payload-Version'] === '1'
+                    && !isset($options['headers']['X-Perfbase-Client-Created-At']);
             }))
             ->andReturn(SubmitResult::success());
 
         $apiClient = new ApiClient($this->config, $this->mockHttpClient);
-        $result = $apiClient->submitTrace('');
+        $result = $apiClient->submitTrace('', 1);
 
         $this->assertTrue($result->isSuccess());
     }
@@ -151,7 +182,7 @@ public function testSubmitTracePropagateshFailureResult(): void
             ->andReturn($failureResult);
 
         $apiClient = new ApiClient($this->config, $this->mockHttpClient);
-        $result = $apiClient->submitTrace('test-data');
+        $result = $apiClient->submitTrace('test-data', 1);
 
         $this->assertTrue($result->isRetryable());
         $this->assertSame(503, $result->getStatusCode());
diff --git a/tests/Integration/PerfbaseIntegrationTest.php b/tests/Integration/PerfbaseIntegrationTest.php
index f642d74..65534d2 100644
--- a/tests/Integration/PerfbaseIntegrationTest.php
+++ b/tests/Integration/PerfbaseIntegrationTest.php
@@ -17,8 +17,9 @@
  */
 class PerfbaseIntegrationTest extends BaseTest
 {
-    /** Valid extension JSON output for use in tests that call submitTrace() */
-    private const EXTENSION_JSON = '{"v":1,"p":"dGVzdA=="}';
+    /** Valid raw extension bytes for use in tests that call submitTrace() */
+    private const EXTENSION_BYTES = 'test';
+    private const ISO_8601_UTC_PATTERN = '/^\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}Z$/';
 
     private MockInterface $mockExtension;
     private MockInterface $mockHttpClient;
@@ -55,14 +56,13 @@ public function testCompleteProfilingWorkflow(): void
         $this->mockExtension->shouldReceive('isAvailable')->once()->andReturn(true);
         $this->mockExtension->shouldReceive('startSpan')->once()->with('integration-span', $this->config->flags, []);
         $this->mockExtension->shouldReceive('stopSpan')->once()->with('integration-span');
-        $this->mockExtension->shouldReceive('getSpanData')->twice()->andReturn(self::EXTENSION_JSON);
+        $this->mockExtension->shouldReceive('getSpanData')->twice()->andReturn(self::EXTENSION_BYTES);
+        $this->mockExtension->shouldReceive('getVersion')->once()->andReturn(1);
         $this->mockExtension->shouldReceive('reset')->twice();
 
         $this->mockApiClient->shouldReceive('submitTrace')
             ->once()
-            ->with(Mockery::on(function (string $p): bool {
-                return strpos($p, '"v":1') !== false;
-            }))
+            ->with(self::EXTENSION_BYTES, 1, Mockery::pattern(self::ISO_8601_UTC_PATTERN))
             ->andReturn(SubmitResult::success(202));
 
         $perfbase = new Perfbase($this->config, $this->mockExtension, $this->mockApiClient);
@@ -71,7 +71,7 @@ public function testCompleteProfilingWorkflow(): void
         $this->assertTrue($perfbase->stopTraceSpan('integration-span'));
 
         $traceData = $perfbase->getTraceData();
-        $this->assertEquals(self::EXTENSION_JSON, $traceData);
+        $this->assertEquals(self::EXTENSION_BYTES, $traceData);
 
         $result = $perfbase->submitTrace();
         $this->assertTrue($result->isSuccess());
@@ -88,7 +88,8 @@ public function testMultipleSpansWorkflow(): void
         $this->mockExtension->shouldReceive('stopSpan')->once()->with('span-1');
         $this->mockExtension->shouldReceive('startSpan')->once()->with('span-2', $this->config->flags, []);
         $this->mockExtension->shouldReceive('stopSpan')->once()->with('span-2');
-        $this->mockExtension->shouldReceive('getSpanData')->once()->andReturn(self::EXTENSION_JSON);
+        $this->mockExtension->shouldReceive('getSpanData')->once()->andReturn(self::EXTENSION_BYTES);
+        $this->mockExtension->shouldReceive('getVersion')->once()->andReturn(1);
         $this->mockExtension->shouldReceive('reset')->twice();
 
         $this->mockApiClient->shouldReceive('submitTrace')
@@ -118,7 +119,8 @@ public function testWorkflowWithConfigurationChanges(): void
         $this->mockExtension->shouldReceive('startSpan')->once()->with('modified-span', $newFlags, []);
         $this->mockExtension->shouldReceive('stopSpan')->once()->with('config-span');
         $this->mockExtension->shouldReceive('stopSpan')->once()->with('modified-span');
-        $this->mockExtension->shouldReceive('getSpanData')->once()->andReturn(self::EXTENSION_JSON);
+        $this->mockExtension->shouldReceive('getSpanData')->once()->andReturn(self::EXTENSION_BYTES);
+        $this->mockExtension->shouldReceive('getVersion')->once()->andReturn(1);
         $this->mockExtension->shouldReceive('reset')->twice();
 
         $this->mockApiClient->shouldReceive('submitTrace')
@@ -162,22 +164,26 @@ public function testErrorHandlingInWorkflow(): void
      */
     public function testApiClientIntegration(): void
     {
-        $testData = '{"v":1,"p":"test","d":"2024-01-01T00:00:00Z"}';
+        $testData = 'binary-data';
+        $clientCreatedAt = '2024-01-01T00:00:00Z';
 
         $this->mockHttpClient->shouldReceive('post')
             ->once()
-            ->with('/v1/submit', Mockery::on(function ($options) use ($testData) {
+            ->with('/v1/submit', Mockery::on(function ($options) use ($testData, $clientCreatedAt) {
                 return $options['body'] === $testData
-                    && $options['headers']['Authorization'] === 'Bearer integration-test-key';
+                    && $options['headers']['Authorization'] === 'Bearer integration-test-key'
+                    && $options['headers']['Content-Type'] === 'application/octet-stream'
+                    && $options['headers']['X-Perfbase-Payload-Version'] === '1'
+                    && $options['headers']['X-Perfbase-Client-Created-At'] === $clientCreatedAt;
             }))
             ->andReturn(SubmitResult::success(202));
 
         $apiClient = new ApiClient($this->config, $this->mockHttpClient);
-        $this->assertTrue($apiClient->submitTrace($testData)->isSuccess());
+        $this->assertTrue($apiClient->submitTrace($testData, 1, $clientCreatedAt)->isSuccess());
     }
 
     /**
-     * Test full stack integration: Perfbase → TracePayloadFactory → ApiClient → HttpClient
+     * Test full stack integration: Perfbase → ApiClient → HttpClient
      * @covers \Perfbase\SDK\Perfbase
      */
     public function testFullStackIntegration(): void
@@ -185,18 +191,17 @@ public function testFullStackIntegration(): void
         $this->mockExtension->shouldReceive('isAvailable')->once()->andReturn(true);
         $this->mockExtension->shouldReceive('startSpan')->once()->with('full-stack', $this->config->flags, []);
         $this->mockExtension->shouldReceive('stopSpan')->once()->with('full-stack');
-        $this->mockExtension->shouldReceive('getSpanData')->once()->andReturn(self::EXTENSION_JSON);
+        $this->mockExtension->shouldReceive('getSpanData')->once()->andReturn(self::EXTENSION_BYTES);
+        $this->mockExtension->shouldReceive('getVersion')->once()->andReturn(1);
         $this->mockExtension->shouldReceive('reset')->twice();
 
         $this->mockHttpClient->shouldReceive('post')
             ->once()
             ->with('/v1/submit', Mockery::on(function ($options) {
-                $body = json_decode($options['body'], true);
-                // Factory should have injected 'd' timestamp
-                return is_array($body)
-                    && $body['v'] === 1
-                    && $body['p'] === 'dGVzdA=='
-                    && isset($body['d'])
+                return $options['body'] === self::EXTENSION_BYTES
+                    && $options['headers']['Content-Type'] === 'application/octet-stream'
+                    && $options['headers']['X-Perfbase-Payload-Version'] === '1'
+                    && preg_match(self::ISO_8601_UTC_PATTERN, $options['headers']['X-Perfbase-Client-Created-At']) === 1
                     && isset($options['headers']['Authorization']);
             }))
             ->andReturn(SubmitResult::success(202));
@@ -218,7 +223,8 @@ public function testFailedSubmissionPreservesState(): void
         $this->mockExtension->shouldReceive('isAvailable')->once()->andReturn(true);
         $this->mockExtension->shouldReceive('startSpan')->once();
         $this->mockExtension->shouldReceive('stopSpan')->once();
-        $this->mockExtension->shouldReceive('getSpanData')->andReturn(self::EXTENSION_JSON);
+        $this->mockExtension->shouldReceive('getSpanData')->andReturn(self::EXTENSION_BYTES);
+        $this->mockExtension->shouldReceive('getVersion')->once()->andReturn(1);
         $this->mockExtension->shouldReceive('reset')->once(); // destructor only
 
         $this->mockHttpClient->shouldReceive('post')
diff --git a/tests/PerfbaseTest.php b/tests/PerfbaseTest.php
index 52cd3c5..b5669c9 100644
--- a/tests/PerfbaseTest.php
+++ b/tests/PerfbaseTest.php
@@ -220,19 +220,14 @@ public function testGetTraceData(): void
      */
     public function testSubmitTraceResetsOnSuccess(): void
     {
-        $extensionJson = json_encode(['v' => 1, 'p' => 'dGVzdA==']);
+        $extensionData = 'test-binary-data';
         $this->mockExtension->shouldReceive('isAvailable')->once()->andReturn(true);
-        $this->mockExtension->shouldReceive('getSpanData')->once()->andReturn($extensionJson);
+        $this->mockExtension->shouldReceive('getSpanData')->once()->andReturn($extensionData);
+        $this->mockExtension->shouldReceive('getVersion')->once()->andReturn(1);
         $this->mockExtension->shouldReceive('reset')->twice(); // Called by submitTrace and destructor
         $this->mockApiClient->shouldReceive('submitTrace')
             ->once()
-            ->with(Mockery::on(function (string $payload) {
-                $decoded = json_decode($payload, true);
-                return is_array($decoded)
-                    && $decoded['v'] === 1
-                    && $decoded['p'] === 'dGVzdA=='
-                    && isset($decoded['d']); // timestamp injected
-            }))
+            ->with($extensionData, 1, Mockery::pattern('/^\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}Z$/'))
             ->andReturn(SubmitResult::success(202));
 
         $perfbase = new Perfbase($this->config, $this->mockExtension, $this->mockApiClient);
@@ -246,13 +241,15 @@ public function testSubmitTraceResetsOnSuccess(): void
      */
     public function testSubmitTraceDoesNotResetOnFailure(): void
     {
-        $extensionJson = json_encode(['v' => 1, 'p' => 'dGVzdA==']);
+        $extensionData = 'test-binary-data';
         $this->mockExtension->shouldReceive('isAvailable')->once()->andReturn(true);
         $this->mockExtension->shouldReceive('startSpan')->once();
-        $this->mockExtension->shouldReceive('getSpanData')->once()->andReturn($extensionJson);
+        $this->mockExtension->shouldReceive('getSpanData')->once()->andReturn($extensionData);
+        $this->mockExtension->shouldReceive('getVersion')->once()->andReturn(1);
         $this->mockExtension->shouldReceive('reset')->once(); // Only destructor, NOT submitTrace
         $this->mockApiClient->shouldReceive('submitTrace')
             ->once()
+            ->with($extensionData, 1, Mockery::pattern('/^\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}Z$/'))
             ->andReturn(SubmitResult::retryableFailure(503, 'Service Unavailable'));
 
         $perfbase = new Perfbase($this->config, $this->mockExtension, $this->mockApiClient);
@@ -317,16 +314,17 @@ public function testDestructorCallsReset(): void
     /**
      * @covers ::submitTrace
      */
-    public function testSubmitTraceThrowsWhenExtensionReturnsMalformedData(): void
+    public function testSubmitTraceThrowsWhenExtensionReturnsInvalidVersion(): void
     {
         $this->mockExtension->shouldReceive('isAvailable')->once()->andReturn(true);
-        $this->mockExtension->shouldReceive('getSpanData')->once()->andReturn('not valid json');
+        $this->mockExtension->shouldReceive('getSpanData')->once()->andReturn('binary-data');
+        $this->mockExtension->shouldReceive('getVersion')->once()->andReturn(0);
         $this->mockExtension->shouldReceive('reset')->once(); // destructor
 
         $perfbase = new Perfbase($this->config, $this->mockExtension, $this->mockApiClient);
 
         $this->expectException(PerfbaseException::class);
-        $this->expectExceptionMessage('invalid JSON');
+        $this->expectExceptionMessage('invalid encoding version');
         $perfbase->submitTrace();
     }
 
@@ -337,6 +335,7 @@ public function testSubmitTraceThrowsWhenExtensionReturnsEmpty(): void
     {
         $this->mockExtension->shouldReceive('isAvailable')->once()->andReturn(true);
         $this->mockExtension->shouldReceive('getSpanData')->once()->andReturn('');
+        $this->mockExtension->shouldReceive('getVersion')->never();
         $this->mockExtension->shouldReceive('reset')->once(); // destructor
 
         $perfbase = new Perfbase($this->config, $this->mockExtension, $this->mockApiClient);
diff --git a/tests/TracePayloadFactoryTest.php b/tests/TracePayloadFactoryTest.php
deleted file mode 100644
index 02dba71..0000000
--- a/tests/TracePayloadFactoryTest.php
+++ /dev/null
@@ -1,96 +0,0 @@
-<?php
-
-namespace Perfbase\SDK\Tests;
-
-use Perfbase\SDK\Exception\PerfbaseException;
-use Perfbase\SDK\TracePayloadFactory;
-
-/**
- * @coversDefaultClass \Perfbase\SDK\TracePayloadFactory
- */
-class TracePayloadFactoryTest extends BaseTest
-{
-    /**
-     * @covers ::build
-     */
-    public function testBuildInjectsTimestamp(): void
-    {
-        $input = json_encode(['v' => 1, 'p' => 'dGVzdA==']);
-
-        $output = TracePayloadFactory::build($input);
-        $decoded = json_decode($output, true);
-
-        $this->assertSame(1, $decoded['v']);
-        $this->assertSame('dGVzdA==', $decoded['p']);
-        $this->assertArrayHasKey('d', $decoded);
-        $this->assertMatchesRegularExpression('/^\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}Z$/', $decoded['d']);
-    }
-
-    /**
-     * @covers ::build
-     */
-    public function testBuildPreservesExistingFields(): void
-    {
-        $input = json_encode(['v' => 1, 'p' => 'abc123']);
-
-        $decoded = json_decode(TracePayloadFactory::build($input), true);
-
-        $this->assertSame(1, $decoded['v']);
-        $this->assertSame('abc123', $decoded['p']);
-    }
-
-    /**
-     * @covers ::build
-     */
-    public function testBuildThrowsOnEmptyInput(): void
-    {
-        $this->expectException(PerfbaseException::class);
-        $this->expectExceptionMessage('empty trace data');
-
-        TracePayloadFactory::build('');
-    }
-
-    /**
-     * @covers ::build
-     */
-    public function testBuildThrowsOnInvalidJson(): void
-    {
-        $this->expectException(PerfbaseException::class);
-        $this->expectExceptionMessage('invalid JSON');
-
-        TracePayloadFactory::build('not json');
-    }
-
-    /**
-     * @covers ::build
-     */
-    public function testBuildThrowsOnMissingVersion(): void
-    {
-        $this->expectException(PerfbaseException::class);
-        $this->expectExceptionMessage('version field');
-
-        TracePayloadFactory::build(json_encode(['p' => 'abc']));
-    }
-
-    /**
-     * @covers ::build
-     */
-    public function testBuildThrowsOnMissingPayload(): void
-    {
-        $this->expectException(PerfbaseException::class);
-        $this->expectExceptionMessage('payload field');
-
-        TracePayloadFactory::build(json_encode(['v' => 1]));
-    }
-
-    /**
-     * @covers ::build
-     */
-    public function testBuildOutputIsValidJson(): void
-    {
-        $input = json_encode(['v' => 1, 'p' => 'dGVzdA==']);
-        $output = TracePayloadFactory::build($input);
-
-        $this->assertJson($output);
-    }
-}
diff --git a/tests/Utils/ExtensionUtilsTest.php b/tests/Utils/ExtensionUtilsTest.php
index bb7f76f..5c910b1 100644
--- a/tests/Utils/ExtensionUtilsTest.php
+++ b/tests/Utils/ExtensionUtilsTest.php
@@ -46,6 +46,7 @@ public function testPerfbaseMethodsAvailableChecksAllRequiredMethods(): void
             'perfbase_disable',
             'perfbase_reset',
             'perfbase_get_data',
+            'perfbase_get_version',
             'perfbase_set_attribute'
         ];
         
@@ -101,10 +102,11 @@ public function testMethodsArrayContainsExpectedFunctions(): void
         $this->assertContains('perfbase_disable', $methods);
         $this->assertContains('perfbase_reset', $methods);
         $this->assertContains('perfbase_get_data', $methods);
+        $this->assertContains('perfbase_get_version', $methods);
         $this->assertContains('perfbase_set_attribute', $methods);
         
-        // Verify the array has exactly 5 methods
-        $this->assertCount(5, $methods);
+        // Verify the array has exactly 6 methods
+        $this->assertCount(6, $methods);
     }
 
     /**
@@ -146,4 +148,4 @@ public function testConsistencyOfResults(): void
         $this->assertEquals($methodsResult1, $methodsResult2, 
             'Methods available check should be consistent');
     }
-}
\ No newline at end of file
+}