diff --git a/packages/chat/src/platform-adapter.ts b/packages/chat/src/platform-adapter.ts
index 5bdae3ea..6fc113a6 100644
--- a/packages/chat/src/platform-adapter.ts
+++ b/packages/chat/src/platform-adapter.ts
@@ -111,6 +111,13 @@ export type CreateHubChatPlatformDeps = {
    * backoff in milliseconds instead of the production ~8s budget.
    */
   reclaimRetryDelaysMs?: readonly number[];
+  /**
+   * Per-attempt wall-clock bound on `sendFoldedMail` inside
+   * `sendFoldedMailWithReclaimRetry` (CL-6644). Defaults to
+   * `DEFAULT_WAKE_TIMEOUT_MS`. Injectable so tests exercise the bound
+   * in milliseconds instead of the production ~30s budget.
+   */
+  mailDeliveryTimeoutMs?: number;
   /**
    * The invite-launch model fallback (see `./inference-preferences.ts`'s
    * `createWorkbenchHostInferencePreferencesResolver`): a
@@ -245,10 +252,42 @@ export function createHubChatPlatform(
     250, 500, 1000, 2000, 4000,
   ];
 
+  // CL-6644: the reclaim-retry loop's own delays only run between
+  // attempts that already failed LOUD with "agent is unreachable" --
+  // they bound nothing about an attempt that instead stalls forever
+  // (a sidecar ack that never comes, a wedged promise anywhere in
+  // `sendFoldedMail`'s call chain) without ever throwing. Each
+  // attempt gets the same kind of wall-clock bound `wakeByAddressBounded`
+  // already puts on the wake itself, so that hang becomes a rejection
+  // `dispatchTurnBatch`'s catch can report and notify on, instead of a
+  // promise nothing ever settles.
+  const MAIL_DELIVERY_TIMEOUT_MS =
+    deps.mailDeliveryTimeoutMs ?? DEFAULT_WAKE_TIMEOUT_MS;
+
   function sleep(ms: number): Promise<void> {
     return new Promise((resolveSleep) => setTimeout(resolveSleep, ms));
   }
 
+  function withTimeout<T>(
+    promise: Promise<T>,
+    ms: number,
+    message: string,
+  ): Promise<T> {
+    return new Promise((resolve, reject) => {
+      const timer = setTimeout(() => reject(new Error(message)), ms);
+      promise.then(
+        (value) => {
+          clearTimeout(timer);
+          resolve(value);
+        },
+        (cause: unknown) => {
+          clearTimeout(timer);
+          reject(cause);
+        },
+      );
+    });
+  }
+
   function isAgentUnreachable(err: unknown): boolean {
     return err instanceof Error && err.message.includes("agent is unreachable");
   }
@@ -565,25 +604,11 @@ export function createHubChatPlatform(
    * failing loud (CL-6644).
    */
   function wakeByAddressBounded(address: string): Promise<void> {
-    return new Promise((resolve, reject) => {
-      const timer = setTimeout(() => {
-        reject(
-          new Error(
-            `wake for "${address}" did not settle within ${String(DEFAULT_WAKE_TIMEOUT_MS)}ms`,
-          ),
-        );
-      }, DEFAULT_WAKE_TIMEOUT_MS);
-      wakeByAddress(address).then(
-        (value) => {
-          clearTimeout(timer);
-          resolve(value);
-        },
-        (cause: unknown) => {
-          clearTimeout(timer);
-          reject(cause);
-        },
-      );
-    });
+    return withTimeout(
+      wakeByAddress(address),
+      DEFAULT_WAKE_TIMEOUT_MS,
+      `wake for "${address}" did not settle within ${String(DEFAULT_WAKE_TIMEOUT_MS)}ms`,
+    );
   }
 
   /**
@@ -682,7 +707,11 @@ export function createHubChatPlatform(
     let loggedRetryStart = false;
     for (let attempt = 0; ; attempt++) {
       try {
-        return await sendFoldedMail(foldedRunsDeps, params);
+        return await withTimeout(
+          sendFoldedMail(foldedRunsDeps, params),
+          MAIL_DELIVERY_TIMEOUT_MS,
+          `mail to ${params.agentAddress} did not settle within ${String(MAIL_DELIVERY_TIMEOUT_MS)}ms`,
+        );
       } catch (err) {
         const delay = RECLAIM_RETRY_DELAYS_MS[attempt];
         if (!isAgentUnreachable(err) || delay === undefined) {
diff --git a/packages/chat/test/platform-adapter.test.ts b/packages/chat/test/platform-adapter.test.ts
index c15e6993..c6529654 100644
--- a/packages/chat/test/platform-adapter.test.ts
+++ b/packages/chat/test/platform-adapter.test.ts
@@ -943,6 +943,70 @@ describe("createHubChatPlatform", () => {
     );
   });
 
+  test("sendMail rejects within the mail-delivery deadline instead of hanging forever when delivery never settles (CL-6644)", async () => {
+    resolveDefinitionSourcesResult = {
+      ok: true,
+      sources: [
+        {
+          id: "off_1",
+          provider: "anthropic",
+          baseURL: "https://inference.invalid",
+          apiKey: "placeholder",
+          model: "claude-sonnet-5",
+        },
+      ],
+      defaultSource: "off_1",
+    };
+
+    const db = createFakeDb({
+      assetRow: {
+        tenantId: "ten_1",
+        creatorPrincipalId: "prin_creator",
+        name: "workbench-1",
+        displayName: null,
+      },
+      definitionId: "wfd_workbench1",
+      workflowRunRow: {
+        id: "ins_workbench1",
+        address: "ins_workbench1@ten1.workbench.test",
+        principalId: "prin_run1",
+      },
+    });
+    db.inserted.push({
+      table: agentSession,
+      values: { id: "ses_run1", principalId: "prin_run1" },
+    });
+
+    const sessionService = createFakeSessionService();
+    // Models the observed CL-6644 symptom: the post-deploy delivery
+    // step (`sessionService.sendUserMessage`, reached through
+    // `sendFoldedMail`) never resolves and never rejects -- a wedged
+    // ack, not a thrown "agent is unreachable" the reclaim-retry loop
+    // already knows how to handle. Before the fix, `sendMail`'s
+    // returned promise stayed pending forever with nothing logged.
+    sessionService.sendUserMessage = () => new Promise<never>(() => {});
+    const sidecarRouter = createFakeSidecarRouter();
+
+    const platform = createHubChatPlatform({
+      toolGrantsForPins: () => [],
+      db: db as never,
+      sessionService,
+      assetService: createFakeAssetService(),
+      sidecarRouter,
+      eventCollectors: createFakeEventCollectors(),
+      mailDeliveryTimeoutMs: 20,
+    });
+
+    await expect(
+      platform.sendMail({
+        tenantId: "ten_1",
+        workbenchId: "ins_workbench1",
+        principalId: "prin_sender",
+        content: { content: "hello workbench" },
+      }),
+    ).rejects.toThrow(/did not settle within 20ms/);
+  });
+
   test("launchInvite mints from the target definition and ensureAwake deploys it", async () => {
     resolveDefinitionSourcesCalls.length = 0;
     resolveDefinitionSourcesResult = {