fix(langchain): Respect split model name for initChatModel

examples/src/models/chat/configurable/basic.ts

@@ -7,7 +7,7 @@ const gpt4o = await initChatModel("gpt-4o", {
 });
 
 // You can also specify the model provider in the model name like this in
-// langchain>=0.3.17:
+// langchain>=0.3.18:
 
 // Returns a @langchain/anthropic ChatAnthropic instance.
 const claudeOpus = await initChatModel("anthropic:claude-3-opus-20240229", {

langchain/src/chat_models/tests/universal.int.test.ts

@@ -62,12 +62,18 @@ test("Initialize non-configurable models", async () => {
 });
 
 test("Works with model provider in model name", async () => {
-  const gpt4 = await initChatModel("openai:gpt-4o-mini", {
+  // eslint-disable-next-line @typescript-eslint/no-explicit-any
+  let error: any;
+  const o3Mini = await initChatModel("openai:o3-mini", {
     temperature: 0.25,
     apiKey: openAIApiKey,
   });
-  const result = await gpt4.invoke("what's your name");
-  expect(result).toBeDefined();
+  try {
+    await o3Mini.invoke("what's your name");
+  } catch (e) {
+    error = e;
+  }
+  expect(error.message).toContain("temperature");
 });
 
 test("Create a partially configurable model with no default model", async () => {

langchain/src/chat_models/universal.ts

@@ -814,7 +814,7 @@ export async function initChatModel<
     ...(fields ?? {}),
   };
   if (modelProvider === undefined && model?.includes(":")) {
-    const modelComponents = model.split(":", 1);
+    const modelComponents = model.split(":", 2);
     if (
       _SUPPORTED_PROVIDERS.includes(modelComponents[0] as ChatModelProvider)
     ) {