- Route Vertex partner/open MaaS models and explicit openapi-enabled credentials through the OpenAI-compatible endpoints/openapi endpoint while reusing service-account OAuth token acquisition and supporting openapi_location overrides.
- Register Vertex service-account MaaS models and aliases from credential metadata and OAuth alias rules so partner models are discoverable and routable.
- Normalize Vertex OpenAPI model identifiers and reject static API keys against official Google Vertex OpenAPI hosts that require OAuth tokens.
Closes: #6763