Stdio Docker MCP containers remain running after closing a session #4461

Describe the bug

When multiple Copilot CLI sessions use local stdio MCP servers running in Docker, closing one session does not terminate the Docker containers started for that session.

The behavior occurs with both:

• A direct Docker MCP.
• A Node wrapper that starts.

Because both MCP implementations reproduce the problem, this appears to be a Copilot CLI stdio MCP lifecycle issue rather than a problem in either Docker image.

After using multiple sessions, docker ps showed three active instances of each image:

matheusrhgestor/html2pdf-mcp
matheusrhgestor/html2pdf-mcp
matheusrhgestor/html2pdf-mcp
matheusrhgestor/kendo-ui-doc
matheusrhgestor/kendo-ui-doc
matheusrhgestor/kendo-ui-doc

In one reproduction:

• A session was resumed around 11:45 local time.
• Its session shutdown was recorded around 11:54 local time.
• The kendo-ui-doc and html2pdf-mcp containers created around 11:44 remained in Up state afterward.
• A new active session started another pair around 11:55.

Representative container output:

052529bdf996|matheusrhgestor/html2pdf-mcp|Up 7 minutes
1793cf8f1aad|matheusrhgestor/kendo-ui-doc|Up 7 minutes
9870e1fd5c7f|matheusrhgestor/html2pdf-mcp|Up 18 minutes
d1bc7dd02cd6|matheusrhgestor/kendo-ui-doc|Up 18 minutes
e161b8af2fb7|matheusrhgestor/html2pdf-mcp|Up 39 minutes
fc11f628ff81|matheusrhgestor/kendo-ui-doc|Up 39 minutes

Affected version

1.0.79

Steps to reproduce the behavior

1. Configure the kendo-ui-doc MCP as a local stdio server using Docker:

   {
     "type": "local",
     "command": "docker",
     "args": [
       "run",
       "--rm",
       "-i",
       "matheusrhgestor/kendo-ui-doc"
     ]
   }

2. Configure the html2pdf MCP as a local stdio server using a Node wrapper that starts:

   docker run --rm -i --mount ... matheusrhgestor/html2pdf-mcp
   

3. Start Copilot CLI session A and verify that one container per MCP is running.

4. Start Copilot CLI session B and verify that a second pair of containers is running.

5. Close session A using the normal session exit action, such as /exit or Ctrl+D.

6. Run:

   docker ps --all --format "{{.ID}}|{{.Image}}|{{.Status}}|{{.Names}}|{{.CreatedAt}}"

7. Observe that the containers created for session A are still running.

Expected behavior

Closing a session should disconnect its stdio MCP processes and stop/remove only the containers created by that session.

The --rm option should remove each container after the corresponding docker run process is terminated.

Containers belonging to other active Copilot CLI sessions should remain running.

Additional context

• Operating system: Windows 11 Pro
• Architecture: x64
• Shell: command prompt
• MCP transport: local stdio
• Docker images:
  • matheusrhgestor/kendo-ui-doc
  • matheusrhgestor/html2pdf-mcp

The direct kendo-ui-doc configuration uses docker run --rm -i.

The html2pdf wrapper uses Node child_process.spawn with stdio: "inherit" and also starts Docker with --rm -i. Therefore, --rm cannot clean up the container while the Docker process is still alive.

The issue is reproducible across more than one session and more than one MCP implementation. The likely failure is that closing a Copilot CLI session does not propagate termination to the local stdio MCP process and its Docker child process.

This appears related to:

#4049
#3440

This report concerns concurrent sessions and closing one session, rather than only /new or /resume.