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

[sdip0971]

Fixes langchain-ai/langgraphjs#1277

🛠️ What this PR does

This PR adds support for the strict flag inside the responseFormat option of createReactAgent.

Now, when strict: true is passed like:

responseFormat: {
  schema: SomeZodSchema,
  prompt: "Some system prompt",
  strict: true,
}

The LLM will correctly invoke:

model.withStructuredOutput(schema, { strict: true });

If strict is not passed, it will default to:

model.withStructuredOutput(schema);

---

🐛 The Problem

The strict flag was previously ignored in the logic block below:

if (typeof responseFormat === "object" && "prompt" in responseFormat && "schema" in responseFormat) {
  const { prompt, schema, strict } = responseFormat;
  model.withStructuredOutput(schema); // ⚠️ strict was never passed!
}

---

✅ The Fix

• ✅ Updated logic to respect strict flag and pass it to withStructuredOutput
• ✅ Updated type definition of responseFormat to support { schema, strict }

responseFormat?: 
  | InteropZodType<StructuredResponseType>
  | StructuredResponseSchemaAndPrompt<StructuredResponseType>
  | { schema: InteropZodType<StructuredResponseType> | Record<string, any>; strict?: boolean }
  | Record<string, any>;

---

Let me know if tests need to be added or adjusted!

[changeset-bot]

🦋 Changeset detected

Latest commit: 30f8eba

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@langchain/langgraph	Patch

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