A transient network/discovery failure invalidated the cached dynamic client and registered a fresh one on every retry. Invalidate only on invalid_client / unauthorized_client or a 400/401 from the provider. Unit-tested. Fixes #67 Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01PPmy3tPq869XDW4njjVaKA