diff --git a/src/hooks/useMessageStream.test.ts b/src/hooks/useMessageStream.test.ts
index 10370a8b..8fa3544e 100644
--- a/src/hooks/useMessageStream.test.ts
+++ b/src/hooks/useMessageStream.test.ts
@@ -234,6 +234,107 @@ describe("useMessageStream", () => {
     });
   });
 
+  it("resets connection state when conversationId is cleared", async () => {
+    const { result, rerender } = renderHook(
+      ({ conversationId }) => useMessageStream(conversationId),
+      { initialProps: { conversationId: "conv-123" as string | null } }
+    );
+
+    act(() => {
+      MockEventSource.instances[0].simulateOpen();
+    });
+
+    await waitFor(() => {
+      expect(result.current.isConnected).toBe(true);
+    });
+
+    const firstInstance = MockEventSource.instances[0];
+
+    rerender({ conversationId: null });
+
+    await waitFor(() => {
+      expect(firstInstance.closed).toBe(true);
+      expect(result.current.isConnected).toBe(false);
+      expect(result.current.error).toBeNull();
+      expect(MockEventSource.instances).toHaveLength(1);
+    });
+  });
+
+  it("waits for onopen when the same conversation reconnects after being cleared", async () => {
+    const { result, rerender } = renderHook(
+      ({ conversationId }) => useMessageStream(conversationId),
+      { initialProps: { conversationId: "conv-123" as string | null } }
+    );
+
+    act(() => {
+      MockEventSource.instances[0].simulateOpen();
+    });
+
+    await waitFor(() => {
+      expect(result.current.isConnected).toBe(true);
+    });
+
+    const firstInstance = MockEventSource.instances[0];
+
+    rerender({ conversationId: null });
+
+    await waitFor(() => {
+      expect(firstInstance.closed).toBe(true);
+      expect(result.current.isConnected).toBe(false);
+    });
+
+    rerender({ conversationId: "conv-123" });
+
+    expect(MockEventSource.instances).toHaveLength(2);
+    expect(result.current.isConnected).toBe(false);
+    expect(result.current.error).toBeNull();
+
+    act(() => {
+      MockEventSource.instances[1].simulateOpen();
+    });
+
+    await waitFor(() => {
+      expect(result.current.isConnected).toBe(true);
+    });
+  });
+
+  it("does not expose stale errors before same conversation reconnect opens", async () => {
+    const { result, rerender } = renderHook(
+      ({ conversationId }) => useMessageStream(conversationId),
+      { initialProps: { conversationId: "conv-123" as string | null } }
+    );
+
+    act(() => {
+      MockEventSource.instances[0].simulateError();
+    });
+
+    await waitFor(() => {
+      expect(result.current.error).toBeTruthy();
+      expect(result.current.isConnected).toBe(false);
+    });
+
+    rerender({ conversationId: null });
+
+    await waitFor(() => {
+      expect(result.current.error).toBeNull();
+    });
+
+    rerender({ conversationId: "conv-123" });
+
+    expect(MockEventSource.instances).toHaveLength(2);
+    expect(result.current.error).toBeNull();
+    expect(result.current.isConnected).toBe(false);
+
+    act(() => {
+      MockEventSource.instances[1].simulateOpen();
+    });
+
+    await waitFor(() => {
+      expect(result.current.error).toBeNull();
+      expect(result.current.isConnected).toBe(true);
+    });
+  });
+
   it("clears error on successful reconnect", async () => {
     const { result } = renderHook(() => useMessageStream("conv-123"));
 
diff --git a/src/hooks/useMessageStream.ts b/src/hooks/useMessageStream.ts
index 09808559..91f44fb6 100644
--- a/src/hooks/useMessageStream.ts
+++ b/src/hooks/useMessageStream.ts
@@ -20,12 +20,22 @@ export function useMessageStream(
   conversationId: string | null,
   options: UseMessageStreamOptions = {}
 ): UseMessageStreamReturn {
-  const [isConnected, setIsConnected] = useState(false);
-  const [error, setError] = useState<Error | null>(null);
+  const [connectedStreamId, setConnectedStreamId] = useState<number | null>(
+    null
+  );
+  const [connectionError, setConnectionError] = useState<{
+    streamId: number;
+    conversationId: string;
+    error: Error;
+  } | null>(null);
   const [reconnectTrigger, setReconnectTrigger] = useState(0);
-  const [isOtherTyping, setIsOtherTyping] = useState(false);
+  const [otherTypingState, setOtherTypingState] = useState({
+    conversationId: null as string | null,
+    streamId: null as number | null,
+    isTyping: false,
+  });
   const eventSourceRef = useRef<EventSource | null>(null);
-  const typingTimeoutRef = useRef<NodeJS.Timeout | null>(null);
+  const streamIdRef = useRef(0);
   const lastTypingSentRef = useRef<number>(0);
 
   const { onMessage, onTypingChange } = options;
@@ -40,17 +50,39 @@ export function useMessageStream(
     onTypingChangeRef.current = onTypingChange;
   }, [onTypingChange]);
 
+  const isConnected =
+    conversationId !== null && connectedStreamId === streamIdRef.current;
+  const error =
+    connectionError?.conversationId === conversationId &&
+    connectionError.streamId === streamIdRef.current
+      ? connectionError.error
+      : null;
+  const isOtherTyping =
+    conversationId !== null &&
+    otherTypingState.conversationId === conversationId &&
+    otherTypingState.streamId === streamIdRef.current &&
+    otherTypingState.isTyping;
+
   // Poll for typing status
   useEffect(() => {
-    if (!conversationId || !isConnected) return;
+    if (!conversationId || !isConnected || connectedStreamId === null) return;
+
+    let cancelled = false;
+    const streamId = connectedStreamId;
 
     const pollTyping = async () => {
       try {
         const response = await fetch(`/api/conversations/${conversationId}/typing`);
         if (response.ok) {
           const data = await response.json();
-          const hasTyping = data.typing && data.typing.length > 0;
-          setIsOtherTyping(hasTyping);
+          if (cancelled || streamIdRef.current !== streamId) return;
+
+          const hasTyping = Boolean(data.typing?.length);
+          setOtherTypingState({
+            conversationId,
+            streamId,
+            isTyping: hasTyping,
+          });
           onTypingChangeRef.current?.(hasTyping, data.typing?.[0]);
         }
       } catch {
@@ -62,15 +94,30 @@ export function useMessageStream(
     const interval = setInterval(pollTyping, 2000);
     pollTyping(); // Initial poll
 
-    return () => clearInterval(interval);
-  }, [conversationId, isConnected]);
+    return () => {
+      cancelled = true;
+      clearInterval(interval);
+    };
+  }, [conversationId, connectedStreamId, isConnected]);
 
   useEffect(() => {
-    if (!conversationId) return;
-
-    // Clean up existing connection
     if (eventSourceRef.current) {
       eventSourceRef.current.close();
+      eventSourceRef.current = null;
+    }
+
+    const streamId = streamIdRef.current + 1;
+    streamIdRef.current = streamId;
+    setConnectedStreamId(null);
+    setConnectionError(null);
+    setOtherTypingState({
+      conversationId: null,
+      streamId: null,
+      isTyping: false,
+    });
+
+    if (!conversationId) {
+      return;
     }
 
     const eventSource = new EventSource(
@@ -79,31 +126,48 @@ export function useMessageStream(
     eventSourceRef.current = eventSource;
 
     eventSource.onopen = () => {
-      setIsConnected(true);
-      setError(null);
+      if (streamIdRef.current !== streamId) return;
+
+      setConnectedStreamId(streamId);
+      setConnectionError(null);
     };
 
     eventSource.onmessage = (event) => {
+      if (streamIdRef.current !== streamId) return;
+
       try {
         const message = JSON.parse(event.data) as MessageWithSender;
         onMessageRef.current?.(message);
         // Clear typing indicator when a message is received
-        setIsOtherTyping(false);
+        setOtherTypingState({
+          conversationId,
+          streamId,
+          isTyping: false,
+        });
       } catch (e) {
         console.error("Failed to parse message:", e);
       }
     };
 
     eventSource.onerror = () => {
-      setIsConnected(false);
-      setError(new Error("Connection lost"));
+      if (streamIdRef.current !== streamId) return;
+
+      setConnectedStreamId(null);
+      setConnectionError({
+        streamId,
+        conversationId,
+        error: new Error("Connection lost"),
+      });
       eventSource.close();
     };
 
     return () => {
       eventSource.close();
-      if (typingTimeoutRef.current) {
-        clearTimeout(typingTimeoutRef.current);
+      if (eventSourceRef.current === eventSource) {
+        eventSourceRef.current = null;
+      }
+      if (streamIdRef.current === streamId) {
+        streamIdRef.current += 1;
       }
     };
   }, [conversationId, reconnectTrigger]);