Install the REST auth profile registry once at composition and make it the
single transport authority for V3. Contract composition now rejects an
unregistered authProfileId, so the executor never resolves a profile at
runtime.
The credential collaborator contributes proof headers only: Fetch credentials
come from the resolved profile, transport-owned and forbidden headers are
rejected, headers outside the profile's allowed set are rejected, and a missing
required header fails closed as AUTH_INTEGRATION_FAILURE with zero fetch calls.
The final invariant re-proves credentials mode and the exact header sets.
Demo mode satisfies the strict bearer profile with a fixed non-secret marker
instead of weakening REFERENCE_EXTERNAL_BEARER. Credential owners now receive
the operation lifetime through AuthOperationContext.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
