feat: Propagate traceId from code assist to response metadata (Fixes … (#11360)

Co-authored-by: owenofbrien <86964623+owenofbrien@users.noreply.github.com>

packages/core/src/code_assist/converter.test.ts

@@ -310,6 +310,27 @@ describe('converter', () => {
       const genaiRes = fromGenerateContentResponse(codeAssistRes);
       expect(genaiRes.modelVersion).toEqual('gemini-2.5-pro');
     });
+
+    it('should handle traceId', () => {
+      const codeAssistRes: CaGenerateContentResponse = {
+        response: {
+          candidates: [],
+        },
+        traceId: 'my-trace-id',
+      };
+      const genaiRes = fromGenerateContentResponse(codeAssistRes);
+      expect(genaiRes.responseId).toEqual('my-trace-id');
+    });
+
+    it('should handle missing traceId', () => {
+      const codeAssistRes: CaGenerateContentResponse = {
+        response: {
+          candidates: [],
+        },
+      };
+      const genaiRes = fromGenerateContentResponse(codeAssistRes);
+      expect(genaiRes.responseId).toBeUndefined();
+    });
   });
 
   describe('toContents', () => {

packages/core/src/code_assist/converter.ts

@@ -73,6 +73,7 @@ interface VertexGenerationConfig {
 
 export interface CaGenerateContentResponse {
   response: VertexGenerateContentResponse;
+  traceId?: string;
 }
 
 interface VertexGenerateContentResponse {
@@ -139,6 +140,7 @@ export function fromGenerateContentResponse(
   out.promptFeedback = inres.promptFeedback;
   out.usageMetadata = inres.usageMetadata;
   out.modelVersion = inres.modelVersion;
+  out.responseId = res.traceId;
   return out;
 }
 

packages/core/src/core/turn.test.ts

@@ -784,6 +784,68 @@ describe('Turn', () => {
         { type: GeminiEventType.Content, value: 'Success' },
       ]);
     });
+
+    it('should yield content events with traceId', async () => {
+      const mockResponseStream = (async function* () {
+        yield {
+          type: StreamEventType.CHUNK,
+          value: {
+            candidates: [{ content: { parts: [{ text: 'Hello' }] } }],
+            responseId: 'trace-123',
+          } as GenerateContentResponse,
+        };
+      })();
+      mockSendMessageStream.mockResolvedValue(mockResponseStream);
+
+      const events = [];
+      for await (const event of turn.run(
+        'test-model',
+        [{ text: 'Hi' }],
+        new AbortController().signal,
+      )) {
+        events.push(event);
+      }
+
+      expect(events).toEqual([
+        { type: GeminiEventType.Content, value: 'Hello', traceId: 'trace-123' },
+      ]);
+    });
+
+    it('should yield thought events with traceId', async () => {
+      const mockResponseStream = (async function* () {
+        yield {
+          type: StreamEventType.CHUNK,
+          value: {
+            candidates: [
+              {
+                content: {
+                  parts: [{ text: '[Thought: thinking]', thought: 'thinking' }],
+                },
+              },
+            ],
+            responseId: 'trace-456',
+          } as unknown as GenerateContentResponse,
+        };
+      })();
+      mockSendMessageStream.mockResolvedValue(mockResponseStream);
+
+      const events = [];
+      for await (const event of turn.run(
+        'test-model',
+        [{ text: 'Hi' }],
+        new AbortController().signal,
+      )) {
+        events.push(event);
+      }
+
+      expect(events).toEqual([
+        {
+          type: GeminiEventType.Thought,
+          value: { subject: '', description: '[Thought: thinking]' },
+          traceId: 'trace-456',
+        },
+      ]);
+    });
   });
 
   describe('getDebugResponses', () => {

packages/core/src/core/turn.ts

@@ -120,11 +120,13 @@ export interface ServerToolCallConfirmationDetails {
 export type ServerGeminiContentEvent = {
   type: GeminiEventType.Content;
   value: string;
+  traceId?: string;
 };
 
 export type ServerGeminiThoughtEvent = {
   type: GeminiEventType.Thought;
   value: ThoughtSummary;
+  traceId?: string;
 };
 
 export type ServerGeminiToolCallRequestEvent = {
@@ -261,19 +263,22 @@ export class Turn {
 
         this.debugResponses.push(resp);
 
+        const traceId = resp.responseId;
+
         const thoughtPart = resp.candidates?.[0]?.content?.parts?.[0];
         if (thoughtPart?.thought) {
           const thought = parseThought(thoughtPart.text ?? '');
           yield {
             type: GeminiEventType.Thought,
             value: thought,
+            traceId,
           };
           continue;
         }
 
         const text = getResponseText(resp);
         if (text) {
-          yield { type: GeminiEventType.Content, value: text };
+          yield { type: GeminiEventType.Content, value: text, traceId };
         }
 
         // Handle function calls (requesting tool execution)