fix: #562 invalid model settings when prompt is set in Agent

.changeset/young-bars-hide.md

@@ -0,0 +1,5 @@
+---
+'@openai/agents-openai': patch
+---
+
+fix: #562 invalid model settings when prompt is set in Agent

examples/basic/prompt-id.ts

@@ -5,7 +5,6 @@ async function main() {
     name: 'Assistant',
     prompt: {
       promptId: 'pmpt_68d50b26524c81958c1425070180b5e10ab840669e470fc7',
-      version: '1',
       variables: { name: 'Kaz' },
     },
   });

packages/agents-openai/src/openaiResponsesModel.ts

@@ -878,7 +878,7 @@ export class OpenAIResponsesModel implements Model {
     }
 
     const requestData = {
-      model: this.#model,
+      ...(!request.prompt ? { model: this.#model } : {}),
       instructions: normalizeInstructions(request.systemInstructions),
       input,
       include,

packages/agents-openai/test/openaiResponsesModel.test.ts

@@ -74,6 +74,36 @@ describe('OpenAIResponsesModel', () => {
     });
   });
 
+  it('omits model when a prompt is provided', async () => {
+    await withTrace('test', async () => {
+      const fakeResponse = { id: 'res-prompt', usage: {}, output: [] };
+      const createMock = vi.fn().mockResolvedValue(fakeResponse);
+      const fakeClient = {
+        responses: { create: createMock },
+      } as unknown as OpenAI;
+      const model = new OpenAIResponsesModel(fakeClient, 'gpt-default');
+
+      const request = {
+        systemInstructions: undefined,
+        prompt: { promptId: 'pmpt_123' },
+        input: 'hello',
+        modelSettings: {},
+        tools: [],
+        outputType: 'text',
+        handoffs: [],
+        tracing: false,
+        signal: undefined,
+      };
+
+      await model.getResponse(request as any);
+
+      expect(createMock).toHaveBeenCalledTimes(1);
+      const [args] = createMock.mock.calls[0];
+      expect('model' in args).toBe(false);
+      expect(args.prompt).toMatchObject({ id: 'pmpt_123' });
+    });
+  });
+
   it('normalizes systemInstructions so empty strings are omitted', async () => {
     await withTrace('test', async () => {
       const fakeResponse = {