fix: decouple stream listeners from stream entry lifecycle

src/lib/stream-session-manager.ts

@@ -31,7 +31,6 @@ interface ActiveStream {
   sessionId: string;
   abortController: AbortController;
   snapshot: SessionStreamSnapshot;
-  listeners: Set<StreamEventListener>;
   idleCheckTimer: ReturnType<typeof setInterval> | null;
   lastEventTime: number;
   gcTimer: ReturnType<typeof setTimeout> | null;
@@ -65,6 +64,7 @@ export interface StartStreamParams {
 // ==========================================
 
 const GLOBAL_KEY = '__streamSessionManager__' as const;
+const LISTENERS_KEY = '__streamSessionListeners__' as const;
 const STREAM_IDLE_TIMEOUT_MS = 330_000;
 const GC_DELAY_MS = 5 * 60 * 1000; // 5 minutes
 
@@ -75,6 +75,14 @@ function getStreamsMap(): Map<string, ActiveStream> {
   return (globalThis as Record<string, unknown>)[GLOBAL_KEY] as Map<string, ActiveStream>;
 }
 
+/** Listener registry — persists independently of stream entries so GC doesn't orphan listeners */
+function getListenersMap(): Map<string, Set<StreamEventListener>> {
+  if (!(globalThis as Record<string, unknown>)[LISTENERS_KEY]) {
+    (globalThis as Record<string, unknown>)[LISTENERS_KEY] = new Map<string, Set<StreamEventListener>>();
+  }
+  return (globalThis as Record<string, unknown>)[LISTENERS_KEY] as Map<string, Set<StreamEventListener>>;
+}
+
 // ==========================================
 // Helpers
 // ==========================================
@@ -102,8 +110,11 @@ function emit(stream: ActiveStream, type: StreamEvent['type']) {
   const snapshot = buildSnapshot(stream);
   stream.snapshot = snapshot; // store latest
   const event: StreamEvent = { type, sessionId: stream.sessionId, snapshot };
-  for (const listener of stream.listeners) {
-    try { listener(event); } catch { /* listener error */ }
+  const listeners = getListenersMap().get(stream.sessionId);
+  if (listeners) {
+    for (const listener of listeners) {
+      try { listener(event); } catch { /* listener error */ }
+    }
   }
   // Also dispatch window event for AppShell
   if (typeof window !== 'undefined') {
@@ -164,7 +175,6 @@ export function startStream(params: StartStreamParams): void {
       error: null,
       finalMessageContent: null,
     },
-    listeners: existing?.listeners ?? new Set(),
     idleCheckTimer: null,
     lastEventTime: Date.now(),
     gcTimer: null,
@@ -487,49 +497,19 @@ export function stopStream(sessionId: string): void {
 // ==========================================
 
 export function subscribe(sessionId: string, listener: StreamEventListener): () => void {
-  const map = getStreamsMap();
-  let stream = map.get(sessionId);
-
-  if (!stream) {
-    // Create a placeholder entry to hold listeners even when no stream is active
-    stream = {
-      sessionId,
-      abortController: new AbortController(),
-      snapshot: {
-        sessionId,
-        phase: 'completed' as const,
-        streamingContent: '',
-        toolUses: [],
-        toolResults: [],
-        streamingToolOutput: '',
-        statusText: undefined,
-        pendingPermission: null,
-        permissionResolved: null,
-        tokenUsage: null,
-        startedAt: 0,
-        completedAt: null,
-        error: null,
-        finalMessageContent: null,
-      },
-      listeners: new Set(),
-      idleCheckTimer: null,
-      lastEventTime: 0,
-      gcTimer: null,
-      accumulatedText: '',
-      toolUsesArray: [],
-      toolResultsArray: [],
-      toolOutputAccumulated: '',
-      toolTimeoutInfo: null,
-      isIdleTimeout: false,
-      sendMessageFn: null,
-    };
-    map.set(sessionId, stream);
+  const listenersMap = getListenersMap();
+  let listeners = listenersMap.get(sessionId);
+  if (!listeners) {
+    listeners = new Set();
+    listenersMap.set(sessionId, listeners);
   }
-
-  stream.listeners.add(listener);
+  listeners.add(listener);
 
   return () => {
-    stream!.listeners.delete(listener);
+    listeners!.delete(listener);
+    if (listeners!.size === 0) {
+      listenersMap.delete(sessionId);
+    }
   };
 }
 
@@ -627,7 +607,7 @@ export function clearSnapshot(sessionId: string): void {
   const stream = getStreamsMap().get(sessionId);
   if (stream && stream.snapshot.phase !== 'active') {
     if (stream.gcTimer) clearTimeout(stream.gcTimer);
-    // Keep the listeners entry but reset the snapshot
+    // Reset the snapshot (listeners are in a separate registry)
     stream.snapshot = {
       ...stream.snapshot,
       startedAt: 0,