diff --git a/packages/core/lib/v3/llm/OpenAIClient.ts b/packages/core/lib/v3/llm/OpenAIClient.ts
index d3391d8ca..226997586 100644
--- a/packages/core/lib/v3/llm/OpenAIClient.ts
+++ b/packages/core/lib/v3/llm/OpenAIClient.ts
@@ -191,6 +191,7 @@ export class OpenAIClient extends LLMClient {
           json_schema: {
             name: options.response_model.name,
             schema: toJsonSchema(options.response_model.schema),
+            strict: true,
           },
         };
       }