Keep GOOGLE_GENAI_USE_VERTEXAI as a long-term alias without runtime deprecation warnings

[ftnext]

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Is your feature request related to a specific problem?

After commit 4e85e9c, ADK introduced GOOGLE_GENAI_USE_ENTERPRISE and treats GOOGLE_GENAI_USE_VERTEXAI as a deprecated fallback. When GOOGLE_GENAI_USE_VERTEXAI is set, ADK emits a DeprecationWarning:

GOOGLE_GENAI_USE_VERTEXAI is deprecated, please use GOOGLE_GENAI_USE_ENTERPRISE instead

I understand the motivation for introducing the new name, but from an ADK user perspective GOOGLE_GENAI_USE_VERTEXAI is a public configuration surface that clearly describes the backend selection: use Vertex AI instead of the Gemini Developer API.

This environment variable can be spread across .env files, CI workflows, Dockerfiles, Kubernetes manifests, deployment scripts, samples, and internal documentation. Requiring users to rename it creates migration work without changing application behavior.

The runtime warning also creates noise and can become disruptive in environments that treat warnings strictly.

Describe the Solution You'd Like

Please keep GOOGLE_GENAI_USE_VERTEXAI as a long-term supported alias for GOOGLE_GENAI_USE_ENTERPRISE, and stop emitting a runtime DeprecationWarning for it.

A possible behavior would be:

• GOOGLE_GENAI_USE_ENTERPRISE remains the preferred variable in new documentation.
• GOOGLE_GENAI_USE_VERTEXAI remains supported as a compatibility alias.
• If both variables are set, GOOGLE_GENAI_USE_ENTERPRISE takes precedence.
• Using GOOGLE_GENAI_USE_VERTEXAI does not emit a runtime deprecation warning unless there is a clearly announced removal plan tied to a major version.

Impact on your work

This avoids unnecessary churn in existing ADK deployments and documentation.

Many projects already use GOOGLE_GENAI_USE_VERTEXAI=true as a stable way to select the Vertex AI backend. Renaming that variable across CI/CD, deployment configuration, examples, and local developer environments takes time but does not provide a direct functional benefit to users.

Keeping the old variable as a quiet long-term alias would preserve backward compatibility while still allowing ADK to document the newer name going forward.

Willingness to contribute

Yes, I can help validate the behavior. If maintainers agree with this direction, I may also be able to send a small PR.

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🟡 Recommended Information

Describe Alternatives You've Considered

The current workaround is to rename all existing configuration from:

GOOGLE_GENAI_USE_VERTEXAI=true

to:

GOOGLE_GENAI_USE_ENTERPRISE=true

This works, but it requires touching configuration that may be spread across many environments. It also introduces friction for a naming change that appears to be mostly semantic from the user's perspective.

Another workaround is to suppress DeprecationWarning, but that is too broad and may hide warnings that users actually need to see.

Proposed API / Implementation

In google/adk/utils/env_utils.py, keep the fallback behavior but remove the runtime warning:

def is_enterprise_mode_enabled() -> bool:
  if 'GOOGLE_GENAI_USE_ENTERPRISE' in os.environ:
    return is_env_enabled('GOOGLE_GENAI_USE_ENTERPRISE')
  if 'GOOGLE_GENAI_USE_VERTEXAI' in os.environ:
    return is_env_enabled('GOOGLE_GENAI_USE_VERTEXAI')
  return False

Optionally, documentation can say that GOOGLE_GENAI_USE_ENTERPRISE is the preferred name for new projects, while GOOGLE_GENAI_USE_VERTEXAI remains supported for existing projects.

Additional Context

In google-genai SDK, GOOGLE_GENAI_USE_VERTEXAI is not deprecated
https://github.com/googleapis/python-genai/blob/v2.9.0/google/genai/_api_client.py#L618