### Check for existing issues

- [x] I have searched the existing issues and checked that my issue is not a duplicate.

### The Feature

Currently, LiteLLM enables structured outputs for Claude models via the structured-outputs-2025-11-13 header. However, newer Claude models only support structured output through the output_config.format field in the request body.

I would like LiteLLM to support passing structured output configuration using output_config.format, so that requests can be made in a way that is compatible with the latest Claude API specifications.

Ideally:

Allow users to define structured output via output_config.format Ensure this field is correctly forwarded to the Claude API Avoid relying solely on header-based structured output mechanisms

### Motivation, pitch

The current header-based approach is incompatible with newer Claude models that require output_config.format for structured outputs. This creates a blocker for adopting the latest models and features.

Supporting output_config.format would:

Ensure compatibility with the latest Claude API Provide a more standardized and future-proof way to request structured outputs Reduce friction for developers who nee…