fix(langgraph): respect strict option in responseFormat inside createReactAgent (#1389)

Co-authored-by: Tat Dat Duong <david@duong.cz>

.changeset/poor-avocados-guess.md

@@ -0,0 +1,5 @@
+---
+"@langchain/langgraph": patch
+---
+
+fix(langgraph): respect strict option in responseFormat inside createReactAgent

libs/langgraph/src/prebuilt/react_agent_executor.ts

@@ -57,10 +57,13 @@ export interface AgentState<
 
 export type N = typeof START | "agent" | "tools";
 
-export type StructuredResponseSchemaAndPrompt<StructuredResponseType> = {
-  prompt: string;
+type StructuredResponseSchemaOptions<StructuredResponseType> = {
   // eslint-disable-next-line @typescript-eslint/no-explicit-any
   schema: InteropZodType<StructuredResponseType> | Record<string, any>;
+  prompt?: string;
+
+  strict?: boolean;
+  [key: string]: unknown;
 };
 
 function _convertMessageModifierToPrompt(
@@ -478,6 +481,7 @@ export type CreateReactAgentParams<
    * @deprecated Use prompt instead.
    */
   stateModifier?: StateModifier;
+
   /**
    * An optional prompt for the LLM. This takes full graph state BEFORE the LLM is called and prepares the input to LLM.
    *
@@ -523,13 +527,15 @@ export type CreateReactAgentParams<
    */
   responseFormat?:
     | InteropZodType<StructuredResponseType>
-    | StructuredResponseSchemaAndPrompt<StructuredResponseType>
+    | StructuredResponseSchemaOptions<StructuredResponseType>
     // eslint-disable-next-line @typescript-eslint/no-explicit-any
     | Record<string, any>;
+
   /**
    * An optional name for the agent.
    */
   name?: string;
+
   /**
    * Use to specify how to expose the agent name to the underlying supervisor LLM.
 
@@ -711,20 +717,18 @@ export function createReactAgent<
     const messages = [...state.messages];
     let modelWithStructuredOutput;
 
-    if (
-      typeof responseFormat === "object" &&
-      "prompt" in responseFormat &&
-      "schema" in responseFormat
-    ) {
-      const { prompt, schema } = responseFormat;
-      modelWithStructuredOutput = (await _getModel(llm)).withStructuredOutput(
-        schema
-      );
-      messages.unshift(new SystemMessage({ content: prompt }));
+    const model = await _getModel(llm);
+
+    if (typeof responseFormat === "object" && "schema" in responseFormat) {
+      const { prompt, schema, ...options } =
+        responseFormat as StructuredResponseSchemaOptions<StructuredResponseFormat>;
+
+      modelWithStructuredOutput = model.withStructuredOutput(schema, options);
+      if (prompt != null) {
+        messages.unshift(new SystemMessage({ content: prompt }));
+      }
     } else {
-      modelWithStructuredOutput = (await _getModel(llm)).withStructuredOutput(
-        responseFormat
-      );
+      modelWithStructuredOutput = model.withStructuredOutput(responseFormat);
     }
 
     const response = await modelWithStructuredOutput.invoke(messages, config);

libs/langgraph/src/tests/prebuilt.test.ts

@@ -1864,20 +1864,31 @@ describe("createReactAgent with structured responses", () => {
       "The weather is nice"
     );
 
-    // Test with prompt and schema
+    // Test with prompt and schema (and options)
     const agent2 = createReactAgent({
       llm,
       tools: [getWeather],
       responseFormat: {
         prompt: "Meow",
         schema: weatherResponseSchema,
+
+        name: "generate_structured_response",
+        strict: true,
       },
     });
 
+    const withStructuredOutputSpy = vi.spyOn(llm, "withStructuredOutput");
+
     const result2 = await agent2.invoke({
       messages: [new HumanMessage("What's the weather?")],
     });
 
+    // Check if `strict` is set properly
+    expect(withStructuredOutputSpy).toHaveBeenCalledWith(
+      weatherResponseSchema,
+      { name: "generate_structured_response", strict: true }
+    );
+
     expect(result2.structuredResponse).toEqual(expectedStructuredResponse);
     expect(result2.messages.length).toEqual(4);
     expect(result2.messages[2].content).toEqual(