fix(core): Do not overwrite user provided conversation id in Vercel (#19903)

We set the conversation id unconditionally based on the `resonse_id`, so
if a user calls `Sentry.setConversationId()` explicitly this will
be overwritten, which is unexpected.


Closes #19904 (added automatically)

Author: nicohrubec

dev-packages/node-integration-tests/suites/tracing/vercelai/scenario-conversation-id.mjs

@@ -0,0 +1,27 @@
+import * as Sentry from '@sentry/node';
+import { generateText } from 'ai';
+import { MockLanguageModelV1 } from 'ai/test';
+
+Sentry.setConversationId('conv-a');
+
+async function run() {
+  await Sentry.startSpan({ op: 'function', name: 'main' }, async () => {
+    await generateText({
+      experimental_telemetry: { isEnabled: true },
+      model: new MockLanguageModelV1({
+        doGenerate: async () => ({
+          rawCall: { rawPrompt: null, rawSettings: {} },
+          finishReason: 'stop',
+          usage: { promptTokens: 10, completionTokens: 20 },
+          text: 'Hello!',
+          providerMetadata: {
+            openai: { responseId: 'resp_should_not_overwrite' },
+          },
+        }),
+      }),
+      prompt: 'Say hello',
+    });
+  });
+}
+
+run();

dev-packages/node-integration-tests/suites/tracing/vercelai/test.ts

@@ -923,4 +923,31 @@ describe('Vercel AI integration', () => {
       await createRunner().expect({ transaction: expectedTransaction }).start().completed();
     });
   });
+
+  createEsmAndCjsTests(__dirname, 'scenario-conversation-id.mjs', 'instrument.mjs', (createRunner, test) => {
+    test('does not overwrite conversation id set via Sentry.setConversationId with responseId from provider metadata', async () => {
+      await createRunner()
+        .expect({
+          transaction: {
+            transaction: 'main',
+            spans: expect.arrayContaining([
+              expect.objectContaining({
+                op: 'gen_ai.invoke_agent',
+                data: expect.objectContaining({
+                  'gen_ai.conversation.id': 'conv-a',
+                }),
+              }),
+              expect.objectContaining({
+                op: 'gen_ai.generate_text',
+                data: expect.objectContaining({
+                  'gen_ai.conversation.id': 'conv-a',
+                }),
+              }),
+            ]),
+          },
+        })
+        .start()
+        .completed();
+    });
+  });
 });

packages/core/src/tracing/vercel-ai/index.ts

@@ -470,7 +470,9 @@ function addProviderMetadataToAttributes(attributes: SpanAttributes): void {
           'gen_ai.usage.output_tokens.prediction_rejected',
           openaiMetadata.rejectedPredictionTokens,
         );
-        setAttributeIfDefined(attributes, 'gen_ai.conversation.id', openaiMetadata.responseId);
+        if (!attributes['gen_ai.conversation.id']) {
+          setAttributeIfDefined(attributes, 'gen_ai.conversation.id', openaiMetadata.responseId);
+        }
       }
 
       if (providerMetadataObject.anthropic) {