fix(openai): fix streaming in openai (langchain-ai#8995)

Author: christian-bromann

.changeset/metal-camels-join.md

@@ -0,0 +1,5 @@
+---
+"@langchain/openai": patch
+---
+
+fix(openai): fix streaming in openai

libs/langchain-openai/src/chat_models.ts

@@ -806,7 +806,7 @@ export abstract class BaseChatOpenAI<
     this.verbosity = fields?.verbosity ?? this.verbosity;
 
     // disable streaming in BaseChatModel if explicitly disabled
-    if (this.streaming === false) this.disableStreaming = true;
+    if (fields?.streaming === false) this.disableStreaming = true;
     if (this.disableStreaming === true) this.streaming = false;
 
     this.streamUsage = fields?.streamUsage ?? this.streamUsage;

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

@@ -1,7 +1,12 @@
 /* eslint-disable no-promise-executor-return */
 /* eslint-disable @typescript-eslint/no-explicit-any */
 import { test, expect, jest } from "@jest/globals";
-import { AIMessage, HumanMessage, ToolMessage } from "@langchain/core/messages";
+import {
+  AIMessage,
+  AIMessageChunk,
+  HumanMessage,
+  ToolMessage,
+} from "@langchain/core/messages";
 import { concat } from "@langchain/core/utils/stream";
 import { InMemoryCache } from "@langchain/core/caches";
 import { ChatOpenAI } from "../chat_models.js";
@@ -746,15 +751,38 @@ test("Test ChatOpenAI tool calling with empty schema in streaming vs non-streami
 
   // Test streaming mode - this should also work but currently doesn't
   const stream = await llmWithTools.stream(dialogs);
-  let finalChunk;
+  let finalChunk: AIMessageChunk | undefined;
+  const chunks = [];
   for await (const chunk of stream) {
+    chunks.push(chunk);
     if (!finalChunk) {
       finalChunk = chunk;
     } else {
       finalChunk = finalChunk.concat(chunk);
     }
   }
 
+  expect(chunks.length).toBeGreaterThanOrEqual(4);
+  expect(finalChunk?.tool_calls).toHaveLength(1);
+  expect(finalChunk?.tool_calls?.[0]).toEqual(
+    expect.objectContaining({
+      name: "get_current_time",
+      args: expect.any(Object),
+      id: expect.any(String),
+      type: "tool_call",
+    })
+  );
+  expect(finalChunk?.tool_call_chunks).toHaveLength(1);
+  expect(finalChunk?.tool_call_chunks?.[0]).toEqual(
+    expect.objectContaining({
+      name: "get_current_time",
+      args: "{}",
+      id: expect.any(String),
+      index: 0,
+      type: "tool_call_chunk",
+    })
+  );
+
   // This should pass but currently fails due to the bug
   expect(finalChunk?.tool_calls).toBeDefined();
   expect(finalChunk?.tool_calls?.length).toBeGreaterThan(0);

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

@@ -12,19 +12,19 @@ describe("ChatOpenAI", () => {
       let chat = new ChatOpenAI({
         model: "gpt-4o-mini",
       });
-      expect(chat.disableStreaming).toBe(true);
+      expect(chat.disableStreaming).toBe(false);
       expect(chat.streaming).toBe(false);
       chat = new ChatOpenAI({
         model: "gpt-4o-mini",
         disableStreaming: undefined,
       } as any);
-      expect(chat.disableStreaming).toBe(true);
+      expect(chat.disableStreaming).toBe(false);
       expect(chat.streaming).toBe(false);
       chat = new ChatOpenAI({
         model: "gpt-4o-mini",
         disableStreaming: false,
       });
-      expect(chat.disableStreaming).toBe(true);
+      expect(chat.disableStreaming).toBe(false);
       expect(chat.streaming).toBe(false);
       chat = new ChatOpenAI({
         model: "gpt-4o-mini",
@@ -36,19 +36,19 @@ describe("ChatOpenAI", () => {
         model: "gpt-4o-mini",
         disableStreaming: null,
       } as any);
-      expect(chatWithNull.disableStreaming).toBe(true);
+      expect(chatWithNull.disableStreaming).toBe(false);
       expect(chat.streaming).toBe(false);
       const chatWithZero = new ChatOpenAI({
         model: "gpt-4o-mini",
         disableStreaming: 0,
       } as any);
-      expect(chatWithZero.disableStreaming).toBe(true);
+      expect(chatWithZero.disableStreaming).toBe(false);
       expect(chat.streaming).toBe(false);
       const chatWithEmptyString = new ChatOpenAI({
         model: "gpt-4o-mini",
         disableStreaming: "",
       } as any);
-      expect(chatWithEmptyString.disableStreaming).toBe(true);
+      expect(chatWithEmptyString.disableStreaming).toBe(false);
       expect(chat.streaming).toBe(false);
       chat = new ChatOpenAI({
         model: "gpt-4o-mini",