Provider connections carry custom headers and cache diagnostics
A provider connection now has request options that apply to every call through it, such as a header a gateway requires.
In the UI: open a provider in Settings → Providers and use the Advanced card to add Custom headers or turn on Prompt cache diagnostics.
In the API: the provider settings accept the same options. Transport headers such as host and content-length are rejected, the list is limited to 16 headers of up to 2 KB each, and header values are redacted in diagnostics. The Anthropic, Gemini, Chat Completions and Open Responses drivers apply them.