1.21.1
(fix): Fix additional_headers in a request’s options being unable to override a global header that was
set at client construction. Every default header was protected from additional_headers, so a
caller who configured a global header on the client (e.g. X-Greenhouse-Id) could not vary it per
request — the per-request value was silently dropped. The API’s non-literal global headers are
now overridable per request, while SDK metadata (User-Agent, X-Fern-*), auth headers, and
literal headers stay protected as before.