fix(openai): Avoid thrown error on o1 stream calls (langchain-ai#6747)

libs/langchain-openai/src/chat_models.ts

@@ -14,6 +14,7 @@ import {
   ToolMessageChunk,
   OpenAIToolCall,
   isAIMessage,
+  convertToChunk,
 } from "@langchain/core/messages";
 import {
   type ChatGeneration,
@@ -1185,6 +1186,19 @@ export class ChatOpenAI<
     options: this["ParsedCallOptions"],
     runManager?: CallbackManagerForLLMRun
   ): AsyncGenerator<ChatGenerationChunk> {
+    if (this.model.includes("o1-")) {
+      console.warn(
+        "[WARNING]: OpenAI o1 models do not yet support token-level streaming. Streaming will yield single chunk."
+      );
+      const result = await this._generate(messages, options, runManager);
+      const messageChunk = convertToChunk(result.generations[0].message);
+      yield new ChatGenerationChunk({
+        message: messageChunk,
+        text:
+          typeof messageChunk.content === "string" ? messageChunk.content : "",
+      });
+      return;
+    }
     const messagesMapped: OpenAICompletionParam[] =
       convertMessagesToOpenAIParams(messages);
     const params = {

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

@@ -940,3 +940,14 @@ test("populates ID field on AIMessage", async () => {
   expect(finalChunk?.id?.length).toBeGreaterThan(1);
   expect(finalChunk?.id?.startsWith("chatcmpl-")).toBe(true);
 });
+
+test("Test ChatOpenAI stream method", async () => {
+  const model = new ChatOpenAI({ model: "o1-mini" });
+  const stream = await model.stream("Print hello world.");
+  const chunks = [];
+  for await (const chunk of stream) {
+    console.log(chunk);
+    chunks.push(chunk);
+  }
+  expect(chunks.length).toEqual(1);
+});