Feature Request: Support Google Cloud Service Account Impersonation

Context:
Claude Code currently integrates with Google Cloud Vertex AI for executing and managing AI workflows
.

https://docs.anthropic.com/en/docs/claude-code/google-vertex-ai

Problem:
There is no built-in support for Google Cloud service account impersonation, which provides short-lived, secure credentials without relying on long-lived service account keys .

https://cloud.google.com/docs/authentication/use-service-account-impersonation

Proposal:

• Add an --impersonate-service-account flag to the Vertex AI integration in Claude Code (anthropic/claude-code) to allow users to specify a service account email for impersonation.
• Under the hood, update the ADC setup or gcloud CLI invocation to include auth/impersonate_service_account=SERVICE_ACCOUNT_EMAIL.

Benefits:

• Aligns Claude Code with Google’s recommended best practices for secure authentication.
• Simplifies enterprise workflows by enabling elevated permissions only when needed.