fix(openai): Support o1 streaming (langchain-ai#7229)

libs/langchain-openai/src/chat_models.ts

@@ -14,7 +14,6 @@ import {
   ToolMessageChunk,
   OpenAIToolCall,
   isAIMessage,
-  convertToChunk,
   UsageMetadata,
 } from "@langchain/core/messages";
 import {
@@ -1360,19 +1359,6 @@ 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

@@ -1166,3 +1166,31 @@ describe("Audio output", () => {
     ).toBeGreaterThan(1);
   });
 });
+
+test("Can stream o1 requests", async () => {
+  const model = new ChatOpenAI({
+    model: "o1-mini",
+  });
+  const stream = await model.stream(
+    "Write me a very simple hello world program in Python. Ensure it is wrapped in a function called 'hello_world' and has descriptive comments."
+  );
+  let finalMsg: AIMessageChunk | undefined;
+  let numChunks = 0;
+  for await (const chunk of stream) {
+    finalMsg = finalMsg ? concat(finalMsg, chunk) : chunk;
+    numChunks += 1;
+  }
+
+  expect(finalMsg).toBeTruthy();
+  if (!finalMsg) {
+    throw new Error("No final message found");
+  }
+  if (typeof finalMsg.content === "string") {
+    expect(finalMsg.content.length).toBeGreaterThan(10);
+  } else {
+    expect(finalMsg.content.length).toBeGreaterThanOrEqual(1);
+  }
+
+  // A
+  expect(numChunks).toBeGreaterThan(3);
+});