VS Code extension starts the same MCP stdio server twice from one config entry

[Attys-syttA]

What version of the IDE extension are you using?

openai.chatgpt@26.5422.21459

What subscription do you have?

Free / not relevant to issue

Which IDE are you using?

Visual Studio Code 1.117.0 (user setup)

What platform is your computer?

Microsoft Windows NT 10.0.26200.0 (x64)

What issue are you seeing?

Summary

The OpenAI ChatGPT / Codex VS Code extension starts the same MCP stdio server twice from a single ~/.codex/config.toml entry.

This is not Serena-specific: the same duplicate startup also happened with xcodebuildmcp.

Environment

• OS: Windows
• VS Code extension: openai.chatgpt@26.5422.21459
• Codex process: codex.exe app-server --analytics-default-enabled
• MCP server affected: Serena MCP
• Config file: C:\Users\<user>\.codex\config.toml

Serena config

[mcp_servers.serena]
command = "uvx"
args = [
  "--from",
  "git+https://github.com/oraios/serena",
  "serena",
  "start-mcp-server",
  "--context",
  "codex"
]

### What steps can reproduce the bug?

1. Start VS Code with the OpenAI ChatGPT/Codex extension installed.
2. Open a workspace that has Codex MCP configured in ~/.codex/config.toml.
3. Configure one Serena MCP server only:

[mcp_servers.serena]
command = "uvx"
args = [
  "--from",
  "git+https://github.com/oraios/serena",
  "serena",
  "start-mcp-server",
  "--context",
  "codex"
]

4. Start/open the Codex Agent session from the VS Code extension.
5. Trigger/use the Serena MCP tools from Codex.
6. Inspect the process tree.

Expected result:
Only one Serena MCP server process should be started.

Actual result:
Two identical Serena MCP server process trees are started by the same codex.exe app-server process.

Observed process tree:

codex.exe app-server --analytics-default-enabled
  -> uvx.exe --from git+https://github.com/oraios/serena serena start-mcp-server --context codex
     -> uv.exe tool uvx --from git+https://github.com/oraios/serena serena start-mcp-server --context codex
        -> serena.exe start-mcp-server --context codex

codex.exe app-server --analytics-default-enabled
  -> uvx.exe --from git+https://github.com/oraios/serena serena start-mcp-server --context codex
     -> uv.exe tool uvx --from git+https://github.com/oraios/serena serena start-mcp-server --context codex
        -> serena.exe start-mcp-server --context codex

Both uvx.exe processes had the same parent process:
codex.exe app-server --analytics-default-enabled

There was only one [mcp_servers.serena] entry in ~/.codex/config.toml.
VS Code settings did not contain a separate Serena/MCP configuration.


### What is the expected behavior?

When a single MCP server is configured once in ~/.codex/config.toml, the Codex VS Code extension should start exactly one MCP server process for that entry.

For the Serena MCP config below, I expect one process tree only:

codex.exe app-server
  -> uvx.exe --from git+https://github.com/oraios/serena serena start-mcp-server --context codex
     -> uv.exe tool uvx ...
        -> serena.exe start-mcp-server --context codex

The extension should not start two identical uvx/serena MCP process trees from the same codex.exe app-server parent unless there are two distinct configured MCP entries or two separate Codex Agent sessions that intentionally require separate MCP servers.


### Additional information

This does not appear to be VS Code itself launching Serena directly. The duplicate launch appears under the OpenAI/Codex extension's codex.exe app-server process.

In the same process snapshot, another MCP server (xcodebuildmcp) also appeared to be started twice under the same codex.exe parent, so this may be a duplicate MCP initialization issue rather than Serena-specific behavior.

[github-actions]

Potential duplicates detected. Please review them and close your issue if it is a duplicate.

• VS Code extension leaks and duplicates local stdio MCP processes on Windows #18965

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[Attys-syttA]

Small note:

There seems to be a formatting issue in the report:

• missing closing ``` in the Serena config block
• duplicated config snippet in the steps section

I’ll clean this up if needed.

[Attys-syttA]

Added this as an additional reproduction/data point to #18965: .
Leaving this issue open for now because it contains process-tree diagnostics and confirms the same parent codex.exe app-server starts both duplicate MCP processes.