adk deploy agent_engine --otel_to_cloud drops the config file's env_vars #7969

Required Information

Describe the Bug:

When the agent folder has no .env, adk deploy agent_engine --otel_to_cloud replaces the env_vars from .agent_engine_config.json (or the file passed to --agent_engine_config_file) with the two variables the flag adds. The instance boots without the user's variables.

to_agent_engine writes GOOGLE_CLOUD_AGENT_ENGINE_ENABLE_TELEMETRY and ADK_CAPTURE_MESSAGE_CONTENT_IN_SPANS into the dict it read from .env (cli_deploy.py#L1862-L1871). With no .env, that dict holds only those two variables. It is not empty, so the next block (#L1882-L1890) treats it as .env content and overwrites agent_config['env_vars'] with it.

Steps to Reproduce:

1. pip install google-adk==2.13.0
2. Save the script under Minimal Reproduction Code as repro.py. It stubs the Agent Platform client, so it needs no GCP project and creates nothing.
3. python repro.py

The script calls to_agent_engine with a config of {"env_vars": {"MY_SETTING": "keep-me"}}, no .env, and otel_to_cloud=True, which is what adk deploy agent_engine --project=my-project --region=us-central1 --otel_to_cloud my_agent passes for that folder.

Expected Behavior:

The flag adds its two variables to the config's env_vars, as it already does for variables read from .env:

{'MY_SETTING': 'keep-me', 'GOOGLE_CLOUD_AGENT_ENGINE_ENABLE_TELEMETRY': 'true', 'ADK_CAPTURE_MESSAGE_CONTENT_IN_SPANS': 'false'}

An ADK_CAPTURE_MESSAGE_CONTENT_IN_SPANS the user set in the config is kept.

Observed Behavior:

Overriding env_vars in agent platform config with ['ADK_CAPTURE_MESSAGE_CONTENT_IN_SPANS', 'GOOGLE_CLOUD_AGENT_ENGINE_ENABLE_TELEMETRY']
google-adk 2.13.0 -> {'GOOGLE_CLOUD_AGENT_ENGINE_ENABLE_TELEMETRY': 'true', 'ADK_CAPTURE_MESSAGE_CONTENT_IN_SPANS': 'false'}

MY_SETTING is gone. A config that sets "ADK_CAPTURE_MESSAGE_CONTENT_IN_SPANS": "true" is deployed with false.

Environment Details:

• ADK Library Version (pip show google-adk): 2.13.0 (latest on PyPI, released 2026-10-23); also 2.9.2, 2.11.0 and main at 3565ad3 (2026-11-02)
• Desktop OS: macOS
• Python Version (python -V): 3.11.14

Model Information:

• Are you using LiteLLM: N/A (deploy CLI)
• Which model is being used: N/A

Optional Information

Regression:

No. It has behaved this way since --otel_to_cloud was added to adk deploy agent_engine in 1.23.0 (21f63f6).

Additional Context:

We keep a config directory path in env_vars, so our deploy script refuses --otel_to_cloud until this is fixed.

--api_key has the same shape (#L1848-L1857): with no .env, the two variables it adds also replace the config's env_vars. I kept this report to --otel_to_cloud.

I have a fix with tests and will open a PR. It settles which env_vars get deployed first, with .env still winning over the config file, and then adds the telemetry variables to that map.

Minimal Reproduction Code:

import json
import pathlib
import sys
import tempfile
import types

import google.adk

deployed = {}


class _Runtimes:

  def create(self, **kwargs):
    return types.SimpleNamespace(
        api_resource=types.SimpleNamespace(
            name='projects/p/locations/us-central1/reasoningEngines/1'
        )
    )

  def update(self, *, name, config):
    deployed.update(config)

  def delete(self, *, name):
    pass


# Stub the Agent Platform client so nothing is created in GCP. ADK 2.12+
# imports `agentplatform` and calls `client.runtimes`; older releases import
# `vertexai` and call `client.agent_engines`.
def _client(*args, **kwargs):
  return types.SimpleNamespace(runtimes=_Runtimes(), agent_engines=_Runtimes())


for name in ('agentplatform', 'vertexai'):
  stub = types.ModuleType(name)
  stub.Client = _client
  sys.modules[name] = stub

from google.adk.cli import cli_deploy

agent = pathlib.Path(tempfile.mkdtemp()) / 'my_agent'
agent.mkdir()
(agent / 'agent.py').write_text('root_agent = None\n')
(agent / '.agent_engine_config.json').write_text(
    json.dumps({'env_vars': {'MY_SETTING': 'keep-me'}})
)

cli_deploy.to_agent_engine(
    agent_folder=str(agent),
    project='my-project',
    region='us-central1',
    otel_to_cloud=True,
)
print('google-adk', google.adk.__version__, '->', deployed['env_vars'])

How often has this issue occurred?:

• Always (100%), whenever the config sets env_vars, the folder has no .env and --otel_to_cloud is passed.