[Reasoning Engine] 400 Reasoning Engine resource [projects/255909145646/locations/us-central1/reasoningEngines/7620517180022456320] failed to start and cannot serve traffic.

[Noahsunpro]

Environment details

• n2-standard-8
• Python version: 3.11.13
• pip version: 25.2
• google-cloud-aiplatform version: 1.110.0

Steps to reproduce

I followed the instructions at https://github.com/google/adk-samples/tree/main/python/agents/personalized-shopping
and then tried to deploy the agent. When attempting to deploy, I see
google.api_core.exceptions.InvalidArgument: 400 Reasoning Engine resource [projects/255909145646/locations/us-central1/reasoningEngines/7620517180022456320] failed to start and cannot serve traffic. Please refer to our documentation (https://cloud.google.com/vertex-ai/generative-ai/docs/agent-engine/troubleshooting/deploy) for checking logs and other troubleshooting tips. 3: Reasoning Engine resource [projects/255909145646/locations/us-central1/reasoningEngines/7620517180022456320] failed to start and cannot serve traffic. Please refer to our documentation (https://cloud.google.com/vertex-ai/generative-ai/docs/agent-engine/troubleshooting/deploy) for checking logs and other troubleshooting tips.

My organisation does not use VPC-SC.

Code example

# Copyright 2025 Google LLC
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

import vertexai
from vertexai.preview.reasoning_engines import AdkApp
from vertexai import agent_engines
from dotenv import load_dotenv
import os

# Import the polling object to modify the timeout
from google.api_core.future import polling

from personalized_shopping.agent import root_agent

load_dotenv()

cloud_project = os.getenv("GOOGLE_CLOUD_PROJECT")
cloud_location = os.getenv("GOOGLE_CLOUD_LOCATION")
storage_bucket = os.getenv("GOOGLE_CLOUD_STORAGE_BUCKET")

print(f"cloud_project={cloud_project}")
print(f"cloud_location={cloud_location}")
print(f"storage_bucket={storage_bucket}")

vertexai.init(
    project=cloud_project,
    location=cloud_location,
    staging_bucket=f"gs://{storage_bucket}",
)

print("-" * 50)
print("Deploying app begin...")
app = AdkApp(
    agent=root_agent,
    enable_tracing=True,
)

AGENT_WHL_FILE = "./personalized_shopping-0.1.0-py3-none-any.whl"

print("Deploying agent to agent engine...")

remote_app = agent_engines.create(
    app,
    requirements=[
        AGENT_WHL_FILE,
    ],
    extra_packages=[
        AGENT_WHL_FILE,
    ],
)
print("Deploying agent to agent engine finished.")
print("-" * 50)

print("Testing deployment:")
# Note: The following test might not work immediately as the endpoint needs time to initialize.
try:
    session = remote_app.create_session(user_id="123")
    for event in remote_app.stream_query(
        user_id="123",
        session_id=session["id"],
        message="Hello!",
    ):
        print(event)
    print("Testing deployment finished!")
except Exception as e:
    print(f"Testing failed. The endpoint might still be initializing. Error: {e}")
print("-" * 50)

Could it be related to a timeout? The model is large.

[HamzaAI9D]

I am encountering the same issue. Could you please confirm whether you’ve been able to resolve it?

[Noahsunpro]

hey @HamzaAI9D I was not able to resolve it and moved onto other solutions.