feat(web): implement SSE chat streaming with real-time token rendering (#516)

Co-authored-by: Jason Woltje <jason@diversecanvas.com>
Co-committed-by: Jason Woltje <jason@diversecanvas.com>

apps/web/src/components/chat/Chat.tsx

@@ -59,14 +59,15 @@ export const Chat = forwardRef<ChatRef, ChatProps>(function Chat(
 
   const { user, isLoading: authLoading } = useAuth();
 
-  // Use the chat hook for state management
   const {
     messages,
     isLoading: isChatLoading,
+    isStreaming,
     error,
     conversationId,
     conversationTitle,
     sendMessage,
+    abortStream,
     loadConversation,
     startNewConversation,
     clearError,
@@ -75,15 +76,7 @@ export const Chat = forwardRef<ChatRef, ChatProps>(function Chat(
     ...(initialProjectId !== undefined && { projectId: initialProjectId }),
   });
 
-  // Connect to WebSocket for real-time updates (when we have a user)
-  const { isConnected: isWsConnected } = useWebSocket(
-    user?.id ?? "", // Use user ID as workspace ID for now
-    "", // Token not needed since we use cookies
-    {
-      // Future: Add handlers for chat-related events
-      // onChatMessage: (msg) => { ... }
-    }
-  );
+  const { isConnected: isWsConnected } = useWebSocket(user?.id ?? "", "", {});
 
   const messagesEndRef = useRef<HTMLDivElement>(null);
   const inputRef = useRef<HTMLTextAreaElement>(null);
@@ -91,7 +84,10 @@ export const Chat = forwardRef<ChatRef, ChatProps>(function Chat(
   const quipTimerRef = useRef<NodeJS.Timeout | null>(null);
   const quipIntervalRef = useRef<NodeJS.Timeout | null>(null);
 
-  // Expose methods to parent via ref
+  // Identify the streaming message (last assistant message while streaming)
+  const streamingMessageId =
+    isStreaming && messages.length > 0 ? messages[messages.length - 1]?.id : undefined;
+
   useImperativeHandle(ref, () => ({
     loadConversation: async (cId: string): Promise<void> => {
       await loadConversation(cId);
@@ -110,7 +106,6 @@ export const Chat = forwardRef<ChatRef, ChatProps>(function Chat(
     scrollToBottom();
   }, [messages, scrollToBottom]);
 
-  // Notify parent of conversation changes
   useEffect(() => {
     if (conversationId && conversationTitle) {
       onConversationChange?.(conversationId, {
@@ -125,7 +120,6 @@ export const Chat = forwardRef<ChatRef, ChatProps>(function Chat(
     }
   }, [conversationId, conversationTitle, initialProjectId, onConversationChange]);
 
-  // Global keyboard shortcut: Ctrl+/ to focus input
   useEffect(() => {
     const handleKeyDown = (e: KeyboardEvent): void => {
       if ((e.ctrlKey || e.metaKey) && e.key === "/") {
@@ -139,20 +133,17 @@ export const Chat = forwardRef<ChatRef, ChatProps>(function Chat(
     };
   }, []);
 
-  // Show loading quips
+  // Show loading quips only during non-streaming load (initial fetch wait)
   useEffect(() => {
-    if (isChatLoading) {
-      // Show first quip after 3 seconds
+    if (isChatLoading && !isStreaming) {
       quipTimerRef.current = setTimeout(() => {
         setLoadingQuip(WAITING_QUIPS[Math.floor(Math.random() * WAITING_QUIPS.length)] ?? null);
       }, 3000);
 
-      // Change quip every 5 seconds
       quipIntervalRef.current = setInterval(() => {
         setLoadingQuip(WAITING_QUIPS[Math.floor(Math.random() * WAITING_QUIPS.length)] ?? null);
       }, 5000);
     } else {
-      // Clear timers when loading stops
       if (quipTimerRef.current) {
         clearTimeout(quipTimerRef.current);
         quipTimerRef.current = null;
@@ -168,7 +159,7 @@ export const Chat = forwardRef<ChatRef, ChatProps>(function Chat(
       if (quipTimerRef.current) clearTimeout(quipTimerRef.current);
       if (quipIntervalRef.current) clearInterval(quipIntervalRef.current);
     };
-  }, [isChatLoading]);
+  }, [isChatLoading, isStreaming]);
 
   const handleSendMessage = useCallback(
     async (content: string) => {
@@ -177,7 +168,6 @@ export const Chat = forwardRef<ChatRef, ChatProps>(function Chat(
     [sendMessage]
   );
 
-  // Show loading state while auth is loading
   if (authLoading) {
     return (
       <div
@@ -227,6 +217,8 @@ export const Chat = forwardRef<ChatRef, ChatProps>(function Chat(
           <MessageList
             messages={messages as (Message & { thinking?: string })[]}
             isLoading={isChatLoading}
+            isStreaming={isStreaming}
+            {...(streamingMessageId != null ? { streamingMessageId } : {})}
             loadingQuip={loadingQuip}
           />
           <div ref={messagesEndRef} />
@@ -294,6 +286,8 @@ export const Chat = forwardRef<ChatRef, ChatProps>(function Chat(
             onSend={handleSendMessage}
             disabled={isChatLoading || !user}
             inputRef={inputRef}
+            isStreaming={isStreaming}
+            onStopStreaming={abortStream}
           />
         </div>
       </div>