[juliays]

Please ensure you have read the contribution guide before creating a pull request.

Link to Issue or Description of Change

1. Link to an existing issue (if applicable):

• Closes: Add support for overriding Python version in "adk deploy" commands #4784

2. Or, if no issue exists, describe the change:

Problem:
_DOCKERFILE_TEMPLATE hard-codes FROM python:3.11-slim, so agents whose dependencies require Python 3.12+ cannot be deployed with adk deploy (cloud_run, docker, gke, or agent_engine). Additionally, setting "python_version" in .agent_engine_config.json (which the Agent Engine SDK accepts) was previously a silent no-op for ADK deployments because ADK builds from a generated Dockerfile (image_spec = {}), where the SDK ignores python_version.

Solution:

• Add --python_version (default 3.11) across all four adk deploy targets (cloud_run, docker, gke, agent_engine) and render FROM python:{python_version}-slim in _DOCKERFILE_TEMPLATE.
• Validate python_version against a strict Python 3.11+ pattern (^3\.(1[1-9]|[2-9][0-9])(\.[0-9]+)?$) before interpolating into the Dockerfile and fail fast in to_agent_engine before staging files.
• Support "python_version" in .agent_engine_config.json for adk deploy agent_engine (popped before calling client.runtimes.update), with precedence: explicit --python_version CLI flag > .agent_engine_config.json > '3.11'.

Testing Plan

Unit Tests:

• I have added or updated unit tests for my change.
• All unit tests pass locally.

uv run pytest tests/unittests/cli/utils/test_cli_deploy.py tests/unittests/cli/utils/test_cli_deploy_to_cloud_run.py tests/unittests/cli/utils/test_cli_tools_click.py
387 passed, 1 xfailed in 4.60s

Also verified uv run pre-commit run --files ... and uv run mypy on all touched files (no issues found).

Manual End-to-End (E2E) Tests:

# Deploy with an explicit Python version via CLI flag:
adk deploy cloud_run --python_version=3.12 --project=<project> --region=<region> path/to/my_agent

# Or via .agent_engine_config.json for Agent Engine:
# {"python_version": "3.12"}
adk deploy agent_engine --project=<project> --region=<region> path/to/my_agent

Checklist

• I have read the CONTRIBUTING.md document.
• I have performed a self-review of my own code.
• I have commented my code, particularly in hard-to-understand areas.
• I have added tests that prove my fix is effective or that my feature works.
• New and existing unit tests pass locally with my changes.
• I have manually tested my changes end-to-end.
• Any dependent changes have been merged and published in downstream modules.

Additional context

• Follow-up documentation update can be opened in google/adk-docs for the CLI reference and deployment guides once this lands.