diff --git a/packages/tui/src/application/run-coordinator.ts b/packages/tui/src/application/run-coordinator.ts
index a510365d0..bb026e2c5 100644
--- a/packages/tui/src/application/run-coordinator.ts
+++ b/packages/tui/src/application/run-coordinator.ts
@@ -30,6 +30,8 @@ import {
 export type TuiRunRuntime = TuiConversationPort &
   Partial<Pick<TuiInteractionPort, 'getPendingQuestionnaire'>>;
 
+const MAX_TIMER_DELAY_MS = 2_147_483_647;
+
 export interface TuiRunRequest {
   turnId: string;
   session: Promise<TuiSession>;
@@ -181,7 +183,7 @@ export class TuiRunCoordinator {
     const activeRun = createActiveRun(request.turnId);
     this.activeRun = activeRun;
     const startedAtMs = this.nowMs();
-    let timeout: ReturnType<typeof setTimeout> | undefined;
+    let timeout: TimeoutChunks | undefined;
     let session: TuiSession | undefined;
     let accepted = false;
     let status: TuiTurnRunStatus = 'succeeded';
@@ -204,10 +206,12 @@ export class TuiRunCoordinator {
       let executionDeadlineAtMs: number | undefined;
       if (request.policy?.timeoutMs !== undefined) {
         executionDeadlineAtMs = this.nowMs() + request.policy.timeoutMs;
-        timeout = setTimeout(() => {
-          void this.stopActive(activeRun, 'timeout').catch(() => undefined);
-        }, request.policy.timeoutMs);
-        timeout.unref?.();
+        timeout = scheduleTimeoutChunks(
+          () => {
+            void this.stopActive(activeRun, 'timeout').catch(() => undefined);
+          },
+          request.policy.timeoutMs,
+        );
       }
 
       const source = this.sendWithQueueRecovery(
@@ -329,7 +333,7 @@ export class TuiRunCoordinator {
         failure = execError(error);
       }
     } finally {
-      if (timeout) clearTimeout(timeout);
+      timeout?.clear();
       if (this.activeRun === activeRun) this.activeRun = undefined;
     }
 
@@ -625,6 +629,37 @@ async function waitForSession(
 
 type BoundedSettlement<T> = { settled: true; value: T } | { settled: false };
 
+interface TimeoutChunks {
+  clear(): void;
+}
+
+/** Node clamps setTimeout delays above 2^31 - 1 ms to 1 ms, so longer
+ * timeouts are scheduled as consecutive bounded chunks that preserve the
+ * requested total delay. */
+function scheduleTimeoutChunks(onExpired: () => void, delayMs: number): TimeoutChunks {
+  let remainingMs = delayMs;
+  let timer: ReturnType<typeof setTimeout> | undefined;
+  let cleared = false;
+  const scheduleNext = () => {
+    if (cleared) return;
+    if (remainingMs <= 0) {
+      onExpired();
+      return;
+    }
+    const chunkMs = Math.min(remainingMs, MAX_TIMER_DELAY_MS);
+    remainingMs -= chunkMs;
+    timer = setTimeout(scheduleNext, chunkMs);
+    timer.unref?.();
+  };
+  scheduleNext();
+  return {
+    clear() {
+      cleared = true;
+      if (timer) clearTimeout(timer);
+    },
+  };
+}
+
 async function settleWithin<T>(task: Promise<T>, timeoutMs: number): Promise<BoundedSettlement<T>> {
   if (timeoutMs <= 0) return { settled: false };
   let timer: ReturnType<typeof setTimeout> | undefined;
diff --git a/packages/tui/test/unit/headless-invocation.test.ts b/packages/tui/test/unit/headless-invocation.test.ts
index f0808fdc6..3f804959c 100644
--- a/packages/tui/test/unit/headless-invocation.test.ts
+++ b/packages/tui/test/unit/headless-invocation.test.ts
@@ -395,6 +395,8 @@ describe('headless invocation', () => {
     ['30s', 30_000],
     ['2m', 120_000],
     ['1H', 3_600_000],
+    ['600h', 2_160_000_000],
+    ['2147483648ms', 2_147_483_648],
   ] as const)('parses timeout %s as %i milliseconds', async (timeout, timeoutMs) => {
     const cwd = await workspace();
     await expect(
diff --git a/packages/tui/test/unit/run-coordinator.test.ts b/packages/tui/test/unit/run-coordinator.test.ts
index 91eafa1e8..86931251c 100644
--- a/packages/tui/test/unit/run-coordinator.test.ts
+++ b/packages/tui/test/unit/run-coordinator.test.ts
@@ -237,6 +237,34 @@ describe('TuiRunCoordinator', () => {
     );
   });
 
+  it('fires timeouts above the Node timer limit only at the requested deadline', async () => {
+    vi.useFakeTimers();
+    try {
+      const timeoutRuntime = createRuntime(async function* pendingTimeout(_req, signal) {
+        yield* [];
+        await new Promise<void>((resolve) =>
+          signal?.addEventListener('abort', () => resolve(), { once: true }),
+        );
+      });
+      // 200 ms beyond Node's 32-bit timer limit; a plain setTimeout would
+      // clamp this to 1 ms and cancel the run almost immediately.
+      const timed = new TuiRunCoordinator(timeoutRuntime, { nowMs: () => 1_000 }).execute({
+        ...request('turn-timeout-overflow'),
+        policy: { timeoutMs: 2_147_483_847 },
+      });
+      expect(timeoutRuntime.abortSession).not.toHaveBeenCalled();
+      await vi.advanceTimersByTimeAsync(2_147_483_647);
+      expect(timeoutRuntime.abortSession).not.toHaveBeenCalled();
+      await vi.advanceTimersByTimeAsync(200);
+      await expect(timed).resolves.toMatchObject({ status: 'timeout' });
+      expect(timeoutRuntime.abortSession).toHaveBeenCalledWith(
+        expect.objectContaining({ reason: 'timeout' }),
+      );
+    } finally {
+      vi.useRealTimers();
+    }
+  });
+
   it('reports a Runtime questionnaire as awaiting continuation without aborting it', async () => {
     const runtime = createRuntime(async function* () {
       yield {