The per-rotation scan called get_provider_handler() unguarded. A rotation member
with invalid/expired credentials (e.g. codex) raises ValueError during credential
validation, which propagated uncaught and returned HTTP 500 for the whole
rotation (hermes bot hitting rotation/lisa). Wrap the build in try/except and
skip the provider on failure, so the rotation falls through to a working member.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>