Built-in gateway documentation updated for unknown fields, auto-mode safeguards and managed settings

What

Claude Code includes documentation for people running a sign-in server or an LLM gateway, a server that sits between Claude Code and the model. That text changed:

• Servers must ignore request parameters, body fields and headers they do not recognize ("Don't reject what you don't recognize."). They should pass body fields and anthropic-beta values through unchanged.
• In auto mode, the client adds an anthropic-beta value and a top-level safeguards field to requests, and reads safeguard_results from responses. A gateway that does not support this should answer with a 400 error naming safeguards.
• The managed settings response is now wrapped as {uuid, checksum, settings}, with a sha256 checksum used for If-None-Match and 304 (not modified) replies. Before, the documentation described returning the bare managed-settings.json with an ETag.

Why

If you run a gateway, requests can carry fields your server has not seen before and should not be rejected. The findings suggest a managed settings response in the old shape may be treated as a failed fetch.