fix: harden typing lifecycle and cross-channel suppression

src/channels/typing.ts

@@ -13,6 +13,8 @@ export type CreateTypingCallbacksParams = {
   onStartError: (err: unknown) => void;
   onStopError?: (err: unknown) => void;
   keepaliveIntervalMs?: number;
+  /** Stop keepalive after this many consecutive start() failures. Default: 2 */
+  maxConsecutiveFailures?: number;
   /** Maximum duration for typing indicator before auto-cleanup (safety TTL). Default: 60s */
   maxDurationMs?: number;
 };
@@ -20,19 +22,31 @@ export type CreateTypingCallbacksParams = {
 export function createTypingCallbacks(params: CreateTypingCallbacksParams): TypingCallbacks {
   const stop = params.stop;
   const keepaliveIntervalMs = params.keepaliveIntervalMs ?? 3_000;
+  const maxConsecutiveFailures = Math.max(1, params.maxConsecutiveFailures ?? 2);
   const maxDurationMs = params.maxDurationMs ?? 60_000; // Default 60s TTL
   let stopSent = false;
   let closed = false;
+  let consecutiveFailures = 0;
+  let breakerTripped = false;
   let ttlTimer: ReturnType<typeof setTimeout> | undefined;
 
-  const fireStart = async () => {
+  const fireStart = async (): Promise<void> => {
     if (closed) {
       return;
     }
+    if (breakerTripped) {
+      return;
+    }
     try {
       await params.start();
+      consecutiveFailures = 0;
     } catch (err) {
+      consecutiveFailures += 1;
       params.onStartError(err);
+      if (consecutiveFailures >= maxConsecutiveFailures) {
+        breakerTripped = true;
+        keepaliveLoop.stop();
+      }
     }
   };
 
@@ -67,9 +81,14 @@ export function createTypingCallbacks(params: CreateTypingCallbacksParams): Typi
       return;
     }
     stopSent = false;
+    breakerTripped = false;
+    consecutiveFailures = 0;
     keepaliveLoop.stop();
     clearTtlTimer();
     await fireStart();
+    if (breakerTripped) {
+      return;
+    }
     keepaliveLoop.start();
     startTtlTimer(); // Start TTL safety timer
   };