fix(agent): filter SDK metadata from messages/partial events

libs/agent/src/lib/internals/stream-manager.bridge.spec.ts

@@ -139,6 +139,88 @@ describe('createStreamManagerBridge', () => {
     }
   );
 
+  it.each(['messages/partial', 'messages/complete'] as const)(
+    'filters metadata from normalized SDK %s events (messages array path)',
+    async (type) => {
+      const transport = new MockAgentTransport();
+      const subjects = makeSubjects();
+      const destroy$ = new Subject<void>();
+      const bridge = createStreamManagerBridge({
+        options: { apiUrl: '', assistantId: 'test', transport },
+        subjects,
+        threadId$: of(null),
+        destroy$: destroy$.asObservable(),
+      });
+
+      bridge.submit({});
+      // Simulate post-normalizeSdkEvent shape: messages array includes metadata
+      // This is what FetchStreamTransport produces in production
+      transport.emit([{
+        type,
+        messages: [
+          { id: 'ai-1', type: 'ai', content: 'Hello' },
+          { langgraph_node: 'chatbot', langgraph_triggers: ['start:chatbot'] },
+        ],
+        data: [
+          { id: 'ai-1', type: 'ai', content: 'Hello' },
+          { langgraph_node: 'chatbot', langgraph_triggers: ['start:chatbot'] },
+        ],
+      } as any]);
+      transport.close();
+
+      await new Promise(r => setTimeout(r, 10));
+
+      // Only the real message should be in messages$, not the metadata
+      expect(subjects.messages$.value).toHaveLength(1);
+      expect(subjects.messages$.value[0]).toMatchObject({ id: 'ai-1', content: 'Hello' });
+      destroy$.next();
+    }
+  );
+
+  it('does not accumulate metadata across multiple messages/partial events', async () => {
+    const transport = new MockAgentTransport();
+    const subjects = makeSubjects();
+    const destroy$ = new Subject<void>();
+    const bridge = createStreamManagerBridge({
+      options: { apiUrl: '', assistantId: 'test', transport },
+      subjects,
+      threadId$: of(null),
+      destroy$: destroy$.asObservable(),
+    });
+
+    bridge.submit({});
+
+    // First values event — sets up the human message
+    transport.emit([{
+      type: 'values',
+      values: { messages: [{ id: 'h-1', type: 'human', content: 'hi' }] },
+    } as any]);
+
+    // Simulate multiple messages/partial events (production SDK shape)
+    for (let i = 0; i < 5; i++) {
+      transport.emit([{
+        type: 'messages/partial',
+        messages: [
+          { id: 'ai-1', type: 'ai', content: 'Hello'.slice(0, i + 1) },
+          { langgraph_node: 'chatbot' },
+        ],
+        data: [
+          { id: 'ai-1', type: 'ai', content: 'Hello'.slice(0, i + 1) },
+          { langgraph_node: 'chatbot' },
+        ],
+      } as any]);
+    }
+
+    transport.close();
+    await new Promise(r => setTimeout(r, 10));
+
+    // Should only have human + AI messages, no accumulated metadata
+    expect(subjects.messages$.value).toHaveLength(2);
+    expect(subjects.messages$.value[0]).toMatchObject({ id: 'h-1', content: 'hi' });
+    expect(subjects.messages$.value[1]).toMatchObject({ id: 'ai-1', content: 'Hello' });
+    destroy$.next();
+  });
+
   it('ignores late events from the previous stream after threadId changes', async () => {
     const transport = new MockAgentTransport();
     const subjects = makeSubjects();

libs/agent/src/lib/internals/stream-manager.bridge.ts

@@ -255,7 +255,10 @@ function isMessagesEvent(type: StreamEvent['type']): boolean {
 function normalizeMessages(event: StreamEvent): unknown[] | null {
   const directMessages = event['messages'];
   if (Array.isArray(directMessages)) {
-    return directMessages;
+    // Filter out non-message metadata objects (e.g. { langgraph_node, langgraph_triggers })
+    // that the LangGraph SDK includes alongside real messages in messages/* events.
+    const filtered = directMessages.filter(isMessageLike);
+    return filtered.length > 0 ? filtered : null;
   }
 
   const data = event['data'];