Fix WebSocket connection for process logs viewer (#734)

* fix: update useLogStream to use WebSocket instead of EventSource

The backend was migrated from SSE to WebSocket in a recent commit,
but the frontend hook was still trying to connect via EventSource.
This caused 'Connection failed' errors when viewing process logs.

Changes:
- Switch from EventSource to WebSocket connection
- Update endpoint to /api/execution-processes/{id}/raw-logs/ws
- Parse messages using LogMsg format (JsonPatch, Finished)
- Maintain all existing retry and error handling logic

* fix: address review feedback for WebSocket connection

- Fixed 'finished' message format: changed from {'Finished': ''} to {finished: true}
- Added isIntentionallyClosed flag to prevent reconnection loops
- Only retry connection on actual errors, not intentional closures
- Check WebSocket close code (1000 = normal closure) before retrying

frontend/src/hooks/useLogStream.ts

@@ -11,9 +11,10 @@ interface UseLogStreamResult {
 export const useLogStream = (processId: string): UseLogStreamResult => {
   const [logs, setLogs] = useState<LogEntry[]>([]);
   const [error, setError] = useState<string | null>(null);
-  const eventSourceRef = useRef<EventSource | null>(null);
+  const wsRef = useRef<WebSocket | null>(null);
   const retryCountRef = useRef<number>(0);
   const retryTimerRef = useRef<ReturnType<typeof setTimeout> | null>(null);
+  const isIntentionallyClosed = useRef<boolean>(false);
 
   useEffect(() => {
     if (!processId) {
@@ -25,12 +26,15 @@ export const useLogStream = (processId: string): UseLogStreamResult => {
     setError(null);
 
     const open = () => {
-      const eventSource = new EventSource(
-        `/api/execution-processes/${processId}/raw-logs`
+      const protocol = window.location.protocol === 'https:' ? 'wss:' : 'ws:';
+      const host = window.location.host;
+      const ws = new WebSocket(
+        `${protocol}//${host}/api/execution-processes/${processId}/raw-logs/ws`
       );
-      eventSourceRef.current = eventSource;
+      wsRef.current = ws;
+      isIntentionallyClosed.current = false;
 
-      eventSource.onopen = () => {
+      ws.onopen = () => {
         setError(null);
         // Reset logs on new connection since server replays history
         setLogs([]);
@@ -41,42 +45,50 @@ export const useLogStream = (processId: string): UseLogStreamResult => {
         setLogs((prev) => [...prev, entry]);
       };
 
-      // Handle json_patch events (new format from server)
-      eventSource.addEventListener('json_patch', (event) => {
+      // Handle WebSocket messages
+      ws.onmessage = (event) => {
         try {
-          const patches = JSON.parse(event.data);
-          patches.forEach((patch: any) => {
-            const value = patch?.value;
-            if (!value || !value.type) return;
+          const data = JSON.parse(event.data);
 
-            switch (value.type) {
-              case 'STDOUT':
-              case 'STDERR':
-                addLogEntry({ type: value.type, content: value.content });
-                break;
-              // Ignore other patch types (NORMALIZED_ENTRY, DIFF, etc.)
-              default:
-                break;
-            }
-          });
+          // Handle different message types based on LogMsg enum
+          if ('JsonPatch' in data) {
+            const patches = data.JsonPatch;
+            patches.forEach((patch: any) => {
+              const value = patch?.value;
+              if (!value || !value.type) return;
+
+              switch (value.type) {
+                case 'STDOUT':
+                case 'STDERR':
+                  addLogEntry({ type: value.type, content: value.content });
+                  break;
+                // Ignore other patch types (NORMALIZED_ENTRY, DIFF, etc.)
+                default:
+                  break;
+              }
+            });
+          } else if (data.finished === true) {
+            isIntentionallyClosed.current = true;
+            ws.close();
+          }
         } catch (e) {
-          console.error('Failed to parse json_patch:', e);
+          console.error('Failed to parse message:', e);
         }
-      });
+      };
 
-      eventSource.addEventListener('finished', () => {
-        eventSource.close();
-      });
-
-      eventSource.onerror = () => {
+      ws.onerror = () => {
         setError('Connection failed');
-        eventSource.close();
-        // Retry a few times with backoff in case of race before logs are ready
-        const next = retryCountRef.current + 1;
-        retryCountRef.current = next;
-        if (next <= 6) {
-          const delay = Math.min(1500, 250 * 2 ** (next - 1));
-          retryTimerRef.current = setTimeout(() => open(), delay);
+      };
+
+      ws.onclose = (event) => {
+        // Only retry if the close was not intentional and not a normal closure
+        if (!isIntentionallyClosed.current && event.code !== 1000) {
+          const next = retryCountRef.current + 1;
+          retryCountRef.current = next;
+          if (next <= 6) {
+            const delay = Math.min(1500, 250 * 2 ** (next - 1));
+            retryTimerRef.current = setTimeout(() => open(), delay);
+          }
         }
       };
     };
@@ -84,9 +96,10 @@ export const useLogStream = (processId: string): UseLogStreamResult => {
     open();
 
     return () => {
-      if (eventSourceRef.current) {
-        eventSourceRef.current.close();
-        eventSourceRef.current = null;
+      if (wsRef.current) {
+        isIntentionallyClosed.current = true;
+        wsRef.current.close();
+        wsRef.current = null;
       }
       if (retryTimerRef.current) {
         clearTimeout(retryTimerRef.current);