Add langsmith:nostream to avoid emitting an empty AI message

agent/agent.tsx

@@ -6,7 +6,7 @@ import { stockbrokerGraph } from "./stockbroker";
 import { ChatOpenAI } from "@langchain/openai";
 
 async function router(
-  state: GenerativeUIState,
+  state: GenerativeUIState
 ): Promise<Partial<GenerativeUIState>> {
   const routerDescription = `The route to take based on the user's input.
 - stockbroker: can fetch the price of a ticker, purchase/sell a ticker, or get the user's portfolio
@@ -27,7 +27,9 @@ async function router(
   const llm = new ChatGoogleGenerativeAI({
     model: "gemini-2.0-flash",
     temperature: 0,
-  }).bindTools([routerTool], { tool_choice: "router" });
+  })
+    .bindTools([routerTool], { tool_choice: "router" })
+    .withConfig({ tags: ["langsmith:nostream"] });
 
   const prompt = `You're a highly helpful AI assistant, tasked with routing the user's query to the appropriate tool.
 You should analyze the user's input, and choose the appropriate tool to use.`;
@@ -58,7 +60,7 @@ You should analyze the user's input, and choose the appropriate tool to use.`;
 }
 
 function handleRoute(
-  state: GenerativeUIState,
+  state: GenerativeUIState
 ): "stockbroker" | "weather" | "generalInput" {
   return state.next;
 }