fix(chat): enhance model name parsing to preserve full model name wit…

.changeset/wicked-teachers-brake.md

@@ -0,0 +1,5 @@
+---
+"langchain": patch
+---
+
+preserve full model name when deciding model provider

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

@@ -807,3 +807,19 @@ describe("Can be initialized without `modelProvider`", () => {
     expect(modelResult.content.length).toBeGreaterThan(0);
   });
 });
+
+describe.skip("Model name parsing with multiple colons preserves full model name", () => {
+  test.each([
+    "ollama:qwen2.5:14b",
+    "ollama:llama3:8b",
+    "ollama:deepseek-r1:1.5b",
+  ])("for %s", async (modelName) => {
+    const model = await initChatModel(modelName, {
+      temperature: 0,
+    });
+
+    const modelResult = await model.invoke("what's your name");
+    expect(modelResult).toBeDefined();
+    expect(modelResult.content.length).toBeGreaterThan(0);
+  });
+});

libs/langchain/src/chat_models/universal.ts

@@ -855,7 +855,11 @@ export async function initChatModel<
     ...(fields ?? {}),
   };
   if (modelProvider === undefined && model?.includes(":")) {
-    const modelComponents = model.split(":", 2);
+    const [provider, ...remainingParts] = model.split(":");
+    const modelComponents =
+      remainingParts.length === 0
+        ? [provider]
+        : [provider, remainingParts.join(":")];
     if (SUPPORTED_PROVIDERS.includes(modelComponents[0] as ChatModelProvider)) {
       // eslint-disable-next-line no-param-reassign
       [modelProvider, model] = modelComponents;