fix(openai): pass service_tier param to API when using useResponsesApi (#9898)

Co-authored-by: Christian Bromann <[email protected]>
Co-authored-by: Hunter Lovell <[email protected]>

Author: 3 people

.changeset/twelve-rivers-turn.md

@@ -0,0 +1,5 @@
+---
+"@langchain/openai": patch
+---
+
+fix(openai): pass service_tier to API when using Responses API

libs/providers/langchain-openai/src/chat_models/responses.ts

@@ -83,6 +83,7 @@ export class ChatOpenAIResponses<
       temperature: this.temperature,
       top_p: this.topP,
       user: this.user,
+      service_tier: this.service_tier,
 
       // if include_usage is set or streamUsage then stream must be set to true.
       stream: this.streaming,

libs/providers/langchain-openai/src/chat_models/tests/responses.int.test.ts

@@ -1241,3 +1241,14 @@ it("won't modify structured output content if outputVersion is set", async () =>
     .invoke("respond with the name 'John'");
   expect(response.name).toBeDefined();
 });
+
+test("ChatOpenAI with service_tier and useResponsesApi", async () => {
+  const model = new ChatOpenAI({
+    model: "gpt-4o",
+    useResponsesApi: true,
+    service_tier: "default",
+    apiKey: process.env.OPENAI_API_KEY || "sk-fake-key",
+  });
+  const res = await model.invoke("Hello");
+  expect(res.content).toBeDefined();
+});

libs/providers/langchain-openai/src/chat_models/tests/responses.test.ts

@@ -51,3 +51,15 @@ describe("strict tool-calling configuration", () => {
     expect((params.tools as Array<{ strict?: boolean }>)[0].strict).toBe(false);
   });
 });
+
+describe("service_tier configuration", () => {
+  it("passes service_tier to invocation params", () => {
+    const model = new ChatOpenAIResponses({
+      model: "gpt-4o",
+      service_tier: "auto",
+    });
+
+    const params = model.invocationParams({});
+    expect(params.service_tier).toBe("auto");
+  });
+});