Summary

• restrict OpenAI-compatible Vertex catalog transforms to the google-vertex provider
• prevent Vertex location and auth fetch options from leaking into unrelated providers such as OpenCode Zen
• add a regression for the exact cross-provider mutation

Root cause

The Google Vertex plugin matched every provider using @ai-sdk/openai-compatible. It consequently added location: "us-central1" and a Vertex auth fetch to the opencode provider. A model-level override to @ai-sdk/openai then forwarded location as a raw OpenAI Responses body field, producing HTTP 400.

Verification

• 28 focused provider and request tests
• Core typecheck
• 22-package push-hook typecheck
• Prettier check