fix(cli): load .env file before agent import validation in deploy

When using `adk deploy agent_engine --validate-agent-import`, the
`_validate_agent_import` function imports the agent module without
first loading `.env` files. This causes agents that depend on
environment variables at import time (e.g. pydantic BaseSettings)
to fail validation with errors like `ValidationError`.

This fix calls `envs.load_dotenv_for_agent()` before the
`importlib.import_module()` call, consistent with how `AgentLoader`
already handles `.env` loading during normal agent loading.

Fixes #4688

Author: weiguangli-io

src/google/adk/cli/cli_deploy.py

@@ -28,6 +28,8 @@
 import click
 from packaging.version import parse
 
+from .utils import envs
+
 _IS_WINDOWS = os.name == 'nt'
 _GCLOUD_CMD = 'gcloud.cmd' if _IS_WINDOWS else 'gcloud'
 _LOCAL_STORAGE_FLAG_MIN_VERSION: Final[str] = '1.21.0'
@@ -509,6 +511,12 @@ def _validate_agent_import(
     # Add parent directory to path so imports work correctly
     if parent_dir not in sys.path:
       sys.path.insert(0, parent_dir)
+
+    # Load .env file before importing the agent module so that
+    # environment-dependent code (e.g. pydantic BaseSettings) can resolve
+    # variables during import.
+    envs.load_dotenv_for_agent(module_name, parent_dir)
+
     try:
       module = importlib.import_module(f'{module_name}.agent')
     except ImportError as e:

tests/unittests/cli/utils/test_cli_deploy.py

@@ -17,6 +17,7 @@
 from __future__ import annotations
 
 import importlib
+import os
 from pathlib import Path
 import shutil
 import subprocess
@@ -654,3 +655,25 @@ def test_restores_sys_path(self, tmp_path: Path) -> None:
     )
 
     assert sys.path == original_path
+
+  def test_loads_dotenv_before_import(self, tmp_path: Path) -> None:
+    """Should load .env file before importing agent module."""
+    # Create agent.py that reads an env var at import time
+    (tmp_path / "__init__.py").touch()
+    (tmp_path / "agent.py").write_text(
+        "import os\n"
+        "val = os.environ.get('_ADK_TEST_DEPLOY_VAR')\n"
+        "if val != 'from_dotenv':\n"
+        "    raise RuntimeError("
+        "'_ADK_TEST_DEPLOY_VAR not loaded from .env')\n"
+        "root_agent = 'ok'\n"
+    )
+    (tmp_path / ".env").write_text("_ADK_TEST_DEPLOY_VAR=from_dotenv\n")
+
+    # Should not raise because .env is loaded before import
+    cli_deploy._validate_agent_import(
+        str(tmp_path), "root_agent", is_config_agent=False
+    )
+
+    # Clean up the env var
+    os.environ.pop("_ADK_TEST_DEPLOY_VAR", None)