ADK Agent Engine Agent fails to use MCP. Error point at bad handling of session management in async context

[rrondir]

crossposting this as it seems it might be a vertexai issue rather google/adk-python#3950 This only happens in agent engine, adk web works well

Running the example

# Your ADK agent connects to the remote MCP service via Streamable HTTP
McpToolset(
    connection_params=StreamableHTTPConnectionParams(
        url="https://your-mcp-server-url.run.app/mcp",
        headers={"Authorization": "Bearer your-auth-token"}
    ),
)

My agent in agent engine is having issues answering questions, I'm using Gemini Enterprise as the interface.

After each call to the mcp the agent fails giving me the option to regenerate the response, it seems it tries to re use the previous session but fails with error messages such as:

Error: an error occured during closing of asynchronous generator <async_generator object streamable_http_client at ...>

RuntimeError: Attempted to exit cancel scope in a different task than it was entered in

RuntimeError: ahtrow(): asynchrnous generator is already running

I'm deploying using all the latest versions from google-genai, google-adk and google-cloud-aiplatform

I can share more details, but I can't see anything special about my setup

Additional context
When running this locally via ADK web I see no issues at all.
I'm using PSC I to connect to the MCP running in a cloud run server. The connections are not stateless