The broker provider allows only token exchange, so the client_credentials
probe always got 400 (Invalid grant_type for provider). Probe with token
exchange and no subject. Authentik checks grant type, then secret, then
subject, so invalid_request means the credentials passed. invalid_client
and invalid_grant are DOWN. Refusals carry their OAuth2 error code
(BrokerRefusedException).
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>