diff --git a/packages/client-runtime/src/state/assets.test.ts b/packages/client-runtime/src/state/assets.test.ts
index 1a4cf384663..58add31d6bb 100644
--- a/packages/client-runtime/src/state/assets.test.ts
+++ b/packages/client-runtime/src/state/assets.test.ts
@@ -4,7 +4,33 @@ import * as Layer from "effect/Layer";
 import { Atom } from "effect/unstable/reactivity";
 
 import type { EnvironmentRegistry } from "../connection/registry.ts";
-import { createAssetEnvironmentAtoms } from "./assets.ts";
+import {
+  createAssetEnvironmentAtoms,
+  InvalidAssetCollectionKeyError,
+  parseAssetCollectionKey,
+} from "./assets.ts";
+
+describe("asset collection keys", () => {
+  it("preserves malformed JSON and its native cause", () => {
+    const key = "not-json";
+    let error: unknown;
+
+    try {
+      parseAssetCollectionKey(key);
+    } catch (cause) {
+      error = cause;
+    }
+
+    expect(error).toBeInstanceOf(InvalidAssetCollectionKeyError);
+    expect(error).toMatchObject({ key, cause: expect.any(SyntaxError) });
+  });
+
+  it("rejects invalid asset collection shapes", () => {
+    const key = JSON.stringify(["environment-1", [{ _tag: "unknown" }]]);
+
+    expect(() => parseAssetCollectionKey(key)).toThrowError(InvalidAssetCollectionKeyError);
+  });
+});
 
 describe("createAssetEnvironmentAtoms", () => {
   it("keys asset URL queries by environment and resource", () => {
diff --git a/packages/client-runtime/src/state/assets.ts b/packages/client-runtime/src/state/assets.ts
index 6863de9055f..e407f5d0028 100644
--- a/packages/client-runtime/src/state/assets.ts
+++ b/packages/client-runtime/src/state/assets.ts
@@ -1,4 +1,5 @@
-import { EnvironmentId, type AssetResource, WS_METHODS } from "@t3tools/contracts";
+import { AssetResource, EnvironmentId, WS_METHODS } from "@t3tools/contracts";
+import * as Schema from "effect/Schema";
 import { Atom } from "effect/unstable/reactivity";
 
 import type { EnvironmentRegistry } from "../connection/registry.ts";
@@ -8,6 +9,32 @@ const ASSET_URL_REFRESH_INTERVAL_MS = 30 * 60_000;
 const ASSET_URL_STALE_TIME_MS = 5 * 60_000;
 const ASSET_URL_IDLE_TTL_MS = 60 * 60_000;
 
+export class InvalidAssetCollectionKeyError extends Schema.TaggedErrorClass<InvalidAssetCollectionKeyError>()(
+  "InvalidAssetCollectionKeyError",
+  {
+    key: Schema.String,
+    cause: Schema.Defect(),
+  },
+) {
+  override get message(): string {
+    return `Invalid asset collection atom key: ${JSON.stringify(this.key)}.`;
+  }
+}
+
+const decodeAssetCollectionKey = Schema.decodeUnknownSync(
+  Schema.Tuple([EnvironmentId, Schema.Array(AssetResource)]),
+);
+
+export function parseAssetCollectionKey(
+  key: string,
+): readonly [EnvironmentId, ReadonlyArray<AssetResource>] {
+  try {
+    return decodeAssetCollectionKey(JSON.parse(key));
+  } catch (cause) {
+    throw new InvalidAssetCollectionKeyError({ key, cause });
+  }
+}
+
 export function resolveAssetUrl(httpBaseUrl: string, relativeUrl: string): string | null {
   try {
     return new URL(relativeUrl, httpBaseUrl).toString();
@@ -27,8 +54,7 @@ export function createAssetEnvironmentAtoms<R, E>(
     refreshIntervalMs: ASSET_URL_REFRESH_INTERVAL_MS,
   });
   const createUrlsFamily = Atom.family((key: string) => {
-    const [rawEnvironmentId, resources] = JSON.parse(key) as [string, ReadonlyArray<AssetResource>];
-    const environmentId = EnvironmentId.make(rawEnvironmentId);
+    const [environmentId, resources] = parseAssetCollectionKey(key);
     return Atom.make((get) =>
       resources.map((resource) =>
         get(
diff --git a/packages/client-runtime/src/state/entities.test.ts b/packages/client-runtime/src/state/entities.test.ts
index 2bdb8f84250..c772d134a67 100644
--- a/packages/client-runtime/src/state/entities.test.ts
+++ b/packages/client-runtime/src/state/entities.test.ts
@@ -11,6 +11,14 @@ import * as Option from "effect/Option";
 import { AsyncResult, Atom, AtomRegistry } from "effect/unstable/reactivity";
 
 import { PrimaryConnectionTarget } from "../connection/model.ts";
+import {
+  InvalidScopedProjectKeyError,
+  InvalidScopedProjectRefCollectionKeyError,
+  InvalidScopedThreadKeyError,
+  parseProjectKey,
+  parseProjectRefCollectionKey,
+  parseThreadKey,
+} from "./entities.ts";
 import type { EnvironmentShellState } from "./shell.ts";
 import { EMPTY_ENVIRONMENT_THREAD_STATE, type EnvironmentThreadState } from "./threads.ts";
 import { createEnvironmentProjectAtoms } from "./projectEntities.ts";
@@ -25,6 +33,56 @@ const OTHER_PROJECT_ID = ProjectId.make("project-2");
 const THREAD_ID = ThreadId.make("thread-1");
 const OTHER_THREAD_ID = ThreadId.make("thread-2");
 
+describe("scoped entity keys", () => {
+  it("preserves an invalid project key as structured error data", () => {
+    const key = "missing-project-key-separator";
+    let error: unknown;
+
+    try {
+      parseProjectKey(key);
+    } catch (cause) {
+      error = cause;
+    }
+
+    expect(error).toEqual(new InvalidScopedProjectKeyError({ key }));
+  });
+
+  it("preserves an invalid thread key as structured error data", () => {
+    const key = "missing-thread-key-separator";
+    let error: unknown;
+
+    try {
+      parseThreadKey(key);
+    } catch (cause) {
+      error = cause;
+    }
+
+    expect(error).toEqual(new InvalidScopedThreadKeyError({ key }));
+  });
+
+  it("preserves malformed project reference collection input and its cause", () => {
+    const key = "not-json";
+    let error: unknown;
+
+    try {
+      parseProjectRefCollectionKey(key);
+    } catch (cause) {
+      error = cause;
+    }
+
+    expect(error).toBeInstanceOf(InvalidScopedProjectRefCollectionKeyError);
+    expect(error).toMatchObject({ key, cause: expect.anything() });
+  });
+
+  it("rejects invalid project reference collection shapes", () => {
+    const key = JSON.stringify([["environment-1"]]);
+
+    expect(() => parseProjectRefCollectionKey(key)).toThrowError(
+      InvalidScopedProjectRefCollectionKeyError,
+    );
+  });
+});
+
 const THREAD_SHELL = {
   id: THREAD_ID,
   projectId: PROJECT_ID,
diff --git a/packages/client-runtime/src/state/entities.ts b/packages/client-runtime/src/state/entities.ts
index 4bcf16f7cfd..e90f31d6da4 100644
--- a/packages/client-runtime/src/state/entities.ts
+++ b/packages/client-runtime/src/state/entities.ts
@@ -5,6 +5,45 @@ import {
   type ScopedProjectRef,
   type ScopedThreadRef,
 } from "@t3tools/contracts";
+import * as Schema from "effect/Schema";
+
+export class InvalidScopedProjectKeyError extends Schema.TaggedErrorClass<InvalidScopedProjectKeyError>()(
+  "InvalidScopedProjectKeyError",
+  {
+    key: Schema.String,
+  },
+) {
+  override get message(): string {
+    return `Invalid scoped project atom key: ${JSON.stringify(this.key)}.`;
+  }
+}
+
+export class InvalidScopedThreadKeyError extends Schema.TaggedErrorClass<InvalidScopedThreadKeyError>()(
+  "InvalidScopedThreadKeyError",
+  {
+    key: Schema.String,
+  },
+) {
+  override get message(): string {
+    return `Invalid scoped thread atom key: ${JSON.stringify(this.key)}.`;
+  }
+}
+
+export class InvalidScopedProjectRefCollectionKeyError extends Schema.TaggedErrorClass<InvalidScopedProjectRefCollectionKeyError>()(
+  "InvalidScopedProjectRefCollectionKeyError",
+  {
+    key: Schema.String,
+    cause: Schema.Defect(),
+  },
+) {
+  override get message(): string {
+    return `Invalid scoped project reference collection atom key: ${JSON.stringify(this.key)}.`;
+  }
+}
+
+const decodeProjectRefCollectionKey = Schema.decodeUnknownSync(
+  Schema.Array(Schema.Tuple([Schema.String, Schema.String])),
+);
 
 export function projectKey(ref: ScopedProjectRef): string {
   return `${ref.environmentId}\u0000${ref.projectId}`;
@@ -21,7 +60,7 @@ export function projectRefCollectionKey(refs: ReadonlyArray<ScopedProjectRef>):
 export function parseProjectKey(key: string): ScopedProjectRef {
   const separator = key.indexOf("\u0000");
   if (separator < 0) {
-    throw new Error("Invalid scoped project atom key.");
+    throw new InvalidScopedProjectKeyError({ key });
   }
   return {
     environmentId: EnvironmentId.make(key.slice(0, separator)),
@@ -30,7 +69,12 @@ export function parseProjectKey(key: string): ScopedProjectRef {
 }
 
 export function parseProjectRefCollectionKey(key: string): ReadonlyArray<ScopedProjectRef> {
-  const entries = JSON.parse(key) as ReadonlyArray<readonly [string, string]>;
+  let entries: ReadonlyArray<readonly [string, string]>;
+  try {
+    entries = decodeProjectRefCollectionKey(JSON.parse(key));
+  } catch (cause) {
+    throw new InvalidScopedProjectRefCollectionKeyError({ key, cause });
+  }
   return entries.map(([environmentId, projectId]) => ({
     environmentId: EnvironmentId.make(environmentId),
     projectId: ProjectId.make(projectId),
@@ -40,7 +84,7 @@ export function parseProjectRefCollectionKey(key: string): ReadonlyArray<ScopedP
 export function parseThreadKey(key: string): ScopedThreadRef {
   const separator = key.indexOf("\u0000");
   if (separator < 0) {
-    throw new Error("Invalid scoped thread atom key.");
+    throw new InvalidScopedThreadKeyError({ key });
   }
   return {
     environmentId: EnvironmentId.make(key.slice(0, separator)),
diff --git a/packages/client-runtime/src/state/threads.ts b/packages/client-runtime/src/state/threads.ts
index 1e2505ac503..bbb38f8d4be 100644
--- a/packages/client-runtime/src/state/threads.ts
+++ b/packages/client-runtime/src/state/threads.ts
@@ -1,7 +1,5 @@
 import {
-  EnvironmentId,
   ORCHESTRATION_WS_METHODS,
-  ThreadId,
   type EnvironmentId as EnvironmentIdType,
   type OrchestrationThread,
   type OrchestrationThreadStreamItem,
@@ -20,6 +18,7 @@ import { connectionProjectionPhase } from "../connection/model.ts";
 import { EnvironmentSupervisor } from "../connection/supervisor.ts";
 import { EnvironmentCacheStore } from "../platform/persistence.ts";
 import { subscribe } from "../rpc/client.ts";
+import { parseThreadKey, threadKey } from "./entities.ts";
 import { applyThreadDetailEvent } from "./threadReducer.ts";
 import { THREAD_STATE_IDLE_TTL_MS } from "./threadRetention.ts";
 import { followStreamInEnvironment } from "./runtime.ts";
@@ -227,29 +226,11 @@ export function threadStateChanges(environmentId: EnvironmentIdType, threadId: T
   );
 }
 
-function threadAtomKey(environmentId: EnvironmentIdType, threadId: ThreadIdType): string {
-  return `${environmentId}\u0000${threadId}`;
-}
-
-function parseThreadAtomKey(key: string): {
-  readonly environmentId: EnvironmentIdType;
-  readonly threadId: ThreadIdType;
-} {
-  const separator = key.indexOf("\u0000");
-  if (separator < 0) {
-    throw new Error("Invalid environment thread atom key.");
-  }
-  return {
-    environmentId: EnvironmentId.make(key.slice(0, separator)),
-    threadId: ThreadId.make(key.slice(separator + 1)),
-  };
-}
-
 export function createEnvironmentThreadStateAtoms<R, E>(
   runtime: Atom.AtomRuntime<EnvironmentRegistry | EnvironmentCacheStore | R, E>,
 ) {
   const family = Atom.family((key: string) => {
-    const { environmentId, threadId } = parseThreadAtomKey(key);
+    const { environmentId, threadId } = parseThreadKey(key);
     return runtime
       .atom(threadStateChanges(environmentId, threadId), {
         initialValue: EMPTY_ENVIRONMENT_THREAD_STATE,
@@ -262,7 +243,7 @@ export function createEnvironmentThreadStateAtoms<R, E>(
 
   return {
     stateAtom: (environmentId: EnvironmentIdType, threadId: ThreadIdType) =>
-      family(threadAtomKey(environmentId, threadId)),
+      family(threadKey({ environmentId, threadId })),
   };
 }