From 45b86450795d8bd3d1e548c8815cd97d6583199d Mon Sep 17 00:00:00 2001
From: Ayaan Zaidi <hi@obviy.us>
Date: Fri, 1 May 2026 07:34:30 +0530
Subject: [PATCH] fix(channels): keep typing indicators off reply critical path

---
 src/auto-reply/reply/typing.ts | 24 ++++++++++++++++++++----
 src/channels/typing.test.ts    | 21 +++++++++++++++++++++
 src/channels/typing.ts         | 15 +++++++++------
 3 files changed, 50 insertions(+), 10 deletions(-)

diff --git a/src/auto-reply/reply/typing.ts b/src/auto-reply/reply/typing.ts
index 8ab76d3fde3..f5f3aed13b6 100644
--- a/src/auto-reply/reply/typing.ts
+++ b/src/auto-reply/reply/typing.ts
@@ -46,6 +46,7 @@ export function createTypingController(params: {
   let active = false;
   let runComplete = false;
   let dispatchIdle = false;
+  let triggerInFlight = false;
   // Important: callbacks (tool/block streaming) can fire late (after the run completed),
   // especially when upstream event emitters don't await async listeners.
   // Once we stop typing, we "seal" the controller so late events can't restart typing forever.
@@ -120,9 +121,24 @@ export function createTypingController(params: {
   });
 
   const triggerTyping = async () => {
-    await startGuard.run(async () => {
-      await onReplyStart?.();
-    });
+    if (triggerInFlight) {
+      return;
+    }
+    triggerInFlight = true;
+    try {
+      await startGuard.run(async () => {
+        await onReplyStart?.();
+      });
+    } catch (err) {
+      log?.(`typing start failed: ${String(err)}`);
+    } finally {
+      triggerInFlight = false;
+    }
+  };
+
+  const scheduleTyping = async () => {
+    void triggerTyping();
+    await Promise.resolve();
   };
 
   const typingLoop = createTypingKeepaliveLoop({
@@ -145,7 +161,7 @@ export function createTypingController(params: {
       return;
     }
     started = true;
-    await triggerTyping();
+    await scheduleTyping();
   };
 
   const maybeStopOnIdle = () => {
diff --git a/src/channels/typing.test.ts b/src/channels/typing.test.ts
index 3c398b2b01c..d8ddae0a592 100644
--- a/src/channels/typing.test.ts
+++ b/src/channels/typing.test.ts
@@ -67,10 +67,28 @@ describe("createTypingCallbacks", () => {
     });
 
     await callbacks.onReplyStart();
+    await flushMicrotasks();
 
     expect(onStartError).toHaveBeenCalledTimes(1);
   });
 
+  it("does not block reply start on a pending typing request", async () => {
+    let resolveStart!: () => void;
+    const { start, callbacks } = createTypingHarness({
+      start: vi.fn(
+        () =>
+          new Promise<void>((resolve) => {
+            resolveStart = resolve;
+          }),
+      ),
+    });
+
+    await callbacks.onReplyStart();
+
+    expect(start).toHaveBeenCalledTimes(1);
+    resolveStart();
+  });
+
   it("invokes stop on idle and reports stop errors", async () => {
     const { stop, onStopError, callbacks } = createTypingHarness({
       stop: vi.fn().mockRejectedValue(new Error("stop")),
@@ -113,6 +131,7 @@ describe("createTypingCallbacks", () => {
         start: vi.fn().mockRejectedValue(new Error("gone")),
       });
       await callbacks.onReplyStart();
+      await flushMicrotasks();
       expect(start).toHaveBeenCalledTimes(1);
       expect(onStartError).toHaveBeenCalledTimes(1);
 
@@ -133,6 +152,7 @@ describe("createTypingCallbacks", () => {
       });
 
       await callbacks.onReplyStart();
+      await flushMicrotasks();
       expect(start).toHaveBeenCalledTimes(1);
 
       await vi.advanceTimersByTimeAsync(9_000);
@@ -154,6 +174,7 @@ describe("createTypingCallbacks", () => {
         maxConsecutiveFailures: 2,
       });
       await callbacks.onReplyStart(); // fail
+      await flushMicrotasks();
       await vi.advanceTimersByTimeAsync(3_000); // success
       await vi.advanceTimersByTimeAsync(3_000); // fail
       await vi.advanceTimersByTimeAsync(3_000); // success
diff --git a/src/channels/typing.ts b/src/channels/typing.ts
index 5d2a5c2e100..c28e2b153d9 100644
--- a/src/channels/typing.ts
+++ b/src/channels/typing.ts
@@ -76,12 +76,15 @@ export function createTypingCallbacks(params: CreateTypingCallbacksParams): Typi
     startGuard.reset();
     keepaliveLoop.stop();
     clearTtlTimer();
-    await fireStart();
-    if (startGuard.isTripped()) {
-      return;
-    }
-    keepaliveLoop.start();
-    startTtlTimer(); // Start TTL safety timer
+    const startPromise = fireStart();
+    void startPromise.then(() => {
+      if (closed || startGuard.isTripped()) {
+        return;
+      }
+      keepaliveLoop.start();
+      startTtlTimer();
+    });
+    await Promise.resolve();
   };
 
   const fireStop = () => {