Summary

• show a note in the Google Vertex API-key connection flow that Anthropic models require Google Cloud credentials
• convert missing Google credentials from the Vertex Anthropic SDK path into an actionable provider auth error
• carry resolved model context into session error formatting so the guidance applies only to @ai-sdk/google-vertex/anthropic, not other Vertex models

Context

Google Vertex exposes multiple model integrations under the same provider. API-key connections work for supported Vertex API-key model paths, while OpenCode routes Anthropic models through @ai-sdk/google-vertex/anthropic, whose AI SDK auth path uses Google Cloud credentials. Previously a user could connect Google Vertex with an API key, select a Claude model, and see only Could not load the default credentials.

The connection notice says:

Note: this API key cannot be used with Anthropic models.
Use `gcloud auth application-default login` or set `GOOGLE_APPLICATION_CREDENTIALS`.

Validation

• bun install --frozen-lockfile --ignore-scripts
• packages/opencode: bun typecheck
• packages/opencode: bun test "test/session/message-v2.test.ts" "test/cli/cmd/tui/provider-options.test.ts" (42 pass)