What
API errors with code invalid_request_header are now logged the same way as invalid API key errors, showing the actual code rather than falling into generic handling. An API key verification failure is also now recognised when the header at fault is an X-Api-Key you supplied yourself rather than one coming from ANTHROPIC_CUSTOM_HEADERS.
Evidence
invalid_request_header
Strings lifted out of the shipped bundle, so the claim above can be checked against them.