Codex CLI hangs when configured to use codex mcp-server as an MCP server

Open 💬 11 comments Opened Nov 14, 2025 by NikTheGeek1

💡 Likely answer: A maintainer (github-actions[bot], contributor) responded on this thread — see the highlighted reply below.

What version of Codex is running?

codex-cli 0.58.0

What subscription do you have?

pro

Which model were you using?

gpt-5.1-codex

What platform is your computer?

Darwin 24.6.0 arm64 arm

What issue are you seeing?

When configuring Codex CLI to connect to Codex’s own MCP server (via the codex mcp-server subcommand), the Codex CLI hangs indefinitely when listing MCP servers (e.g., using the /mcp command). The MCP server never initializes successfully and no tools are exposed.

What steps can reproduce the bug?

Add the following to ~/.codex/config.toml:

[mcp_servers.codex]
command = "codex"
args = ["mcp-server"]

Start the Codex CLI with: codex
In the CLI, run: /mcp

What is the expected behavior?

Expected Behavior
• Codex CLI should successfully start codex mcp-server as an MCP server.
• /mcp should list the MCP server and its tools.

Actual Behavior
• /mcp hangs indefinitely
• Trying to kill the Codex CLI with cmd + C doesn't work
• No MCP tools ever appear.
• The child codex mcp-server process appears to start but the CLI never completes the MCP handshake.

Additional information

_No response_

View original on GitHub ↗

11 Comments

github-actions[bot] contributor · 8 months ago

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

#4844
#5444
#6020
#5044
#5855

Powered by Codex Action

Zyy0530 · 8 months ago

same issue

NikTheGeek1 · 8 months ago

same issue

@Zyy0530 If you want a workaround, I found a reliable approach:
use a small Node.js HTTP MCP wrapper instead of connecting the Codex CLI directly to codex mcp-server.

The idea is to run a tiny HTTP server that:

launches codex mcp-server internally (via stdio)
auto-approves Codex confirmation prompts
re-exports the Codex MCP tools over HTTP using @modelcontextprotocol/sdk

Then in your config.toml, enable the HTTP MCP client and point Codex to the wrapper:

[features]
rmcp_client = true

[mcp_servers.codex-http-wrapper]
url = "http://127.0.0.1:2091/mcp"

This gives you full access to all Codex tools, just routed through a stable HTTP layer instead of the stdio path that currently hangs.

Not ideal long-term, but it’s a clean and reliable workaround until the direct stdio communication is fixed.

raghudinesht · 7 months ago

same issue

thomaswitt · 5 months ago

Same here. Used to work great, until it didnt.

etraut-openai contributor · 5 months ago

@thomaswitt, you mentioned that it used to work great. Does that mean you suspect a regression? If so, can you provide any further details, including repro steps and the version where you saw the behavior change? We haven't spent much time on this issue because we don't have a good repro.

thomaswitt · 5 months ago

@etraut-openai I added codex as an MCP server in claude:

    "codex": {
      "_website": "https://github.com/openai/codex",
      "_description": "Access openai codex via MCP",
      "type": "stdio",
      "command": "codex",
      "args": [
        "-m",
        "gpt-5.2-codex",
        "-s",
        "read-only",
        "-a",
        "never",
        "-c",
        "model_reasoning_effort=high",
        "mcp-server"
      ],
      "env": {}
    },

I see that Claude calls the MCP server:

codex - codex (MCP)(prompt: "Review the following architecture plan for …

but then runs basically for 30-40+ minutes. It insists that the MCP call aborted:

  Thomas is checking if I'm still here again. The Codex MCP call got aborted. Let me try again -
  maybe with a shorter prompt or just acknowledge and retry.

⏺ Nope, wide awake! The Codex MCP server keeps aborting — let me retry with a more focused prompt:

I also see in the ps task list that the command itself is running: codex -m gpt-5.2-codex -s read-only -a never -c model_reasoning_effort=high mcp-server

This doesnt happen EVERY time, but in 70% of the time.

I didn't have these problems until around end of this year. Unfortunately I can't pinpoint them to a specific release.

etraut-openai contributor · 5 months ago

OK, thanks for the details. That's still not a lot to go on. Since this issue has been reported only by a few users in the past several months, it hasn't been a big priority for us to investigate (relative to many other higher-impact issues), so community help is welcome here. If anyone is able to pinpoint concrete repro steps — or better yet, root cause the problem, that would be most helpful.

thomaswitt · 5 months ago

@etraut-openai It would be helpful if I could SOMEWHERE get some debugging output from Codex. I don't know if it's even starting to work, if it hangs because of questions (tried to avoid that with -a never) ... at least a mcp list command for the current thread ids and get an in-between result would be very helpful, as it apparently doesn't stream his results (that's at least what I assume).

Claudes session logs are also not much more insightful:


{
  "debug": "Starting connection with timeout of 300000ms",
  "timestamp": "2026-01-30T16:03:01.386Z",
  "sessionId": "44fd07a6-1f6d-4f9c-be71-6e635b6f2b93",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Successfully connected to stdio server in 52ms",
  "timestamp": "2026-01-30T16:03:01.436Z",
  "sessionId": "44fd07a6-1f6d-4f9c-be71-6e635b6f2b93",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Connection established with capabilities: {\"hasTools\":true,\"hasPrompts\":false,\"hasResources\":false,\"serverVersion\":{\"name\":\"codex-mcp-server\",\"title\":\"Codex\",\"version\":\"0.92.0\"}}",
  "timestamp": "2026-01-30T16:03:01.436Z",
  "sessionId": "44fd07a6-1f6d-4f9c-be71-6e635b6f2b93",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Calling MCP tool: codex",
  "timestamp": "2026-01-30T16:06:46.773Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (30s elapsed)",
  "timestamp": "2026-01-30T16:07:16.774Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (60s elapsed)",
  "timestamp": "2026-01-30T16:07:46.774Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (90s elapsed)",
  "timestamp": "2026-01-30T16:08:16.833Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (120s elapsed)",
  "timestamp": "2026-01-30T16:08:46.915Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (150s elapsed)",
  "timestamp": "2026-01-30T16:09:17.036Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (180s elapsed)",
  "timestamp": "2026-01-30T16:09:47.118Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (210s elapsed)",
  "timestamp": "2026-01-30T16:10:17.222Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (240s elapsed)",
  "timestamp": "2026-01-30T16:10:47.329Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (270s elapsed)",
  "timestamp": "2026-01-30T16:11:17.456Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (300s elapsed)",
  "timestamp": "2026-01-30T16:11:47.511Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (330s elapsed)",
  "timestamp": "2026-01-30T16:12:17.615Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (360s elapsed)",
  "timestamp": "2026-01-30T16:12:47.668Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (390s elapsed)",
  "timestamp": "2026-01-30T16:13:17.761Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (421s elapsed)",
  "timestamp": "2026-01-30T16:13:47.909Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (451s elapsed)",
  "timestamp": "2026-01-30T16:14:17.969Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (481s elapsed)",
  "timestamp": "2026-01-30T16:14:48.089Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (511s elapsed)",
  "timestamp": "2026-01-30T16:15:18.198Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (541s elapsed)",
  "timestamp": "2026-01-30T16:15:48.201Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (571s elapsed)",
  "timestamp": "2026-01-30T16:16:18.201Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (601s elapsed)",
  "timestamp": "2026-01-30T16:16:48.202Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (631s elapsed)",
  "timestamp": "2026-01-30T16:17:18.204Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (661s elapsed)",
  "timestamp": "2026-01-30T16:17:48.204Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (691s elapsed)",
  "timestamp": "2026-01-30T16:18:18.206Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (721s elapsed)",
  "timestamp": "2026-01-30T16:18:48.285Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (751s elapsed)",
  "timestamp": "2026-01-30T16:19:18.350Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (781s elapsed)",
  "timestamp": "2026-01-30T16:19:48.467Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (811s elapsed)",
  "timestamp": "2026-01-30T16:20:18.577Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (841s elapsed)",
  "timestamp": "2026-01-30T16:20:48.711Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (872s elapsed)",
  "timestamp": "2026-01-30T16:21:18.805Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (902s elapsed)",
  "timestamp": "2026-01-30T16:21:48.888Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (932s elapsed)",
  "timestamp": "2026-01-30T16:22:18.961Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (962s elapsed)",
  "timestamp": "2026-01-30T16:22:49.025Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (992s elapsed)",
  "timestamp": "2026-01-30T16:23:19.134Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (1022s elapsed)",
  "timestamp": "2026-01-30T16:23:49.262Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (1052s elapsed)",
  "timestamp": "2026-01-30T16:24:19.338Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (1082s elapsed)",
  "timestamp": "2026-01-30T16:24:49.392Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (1112s elapsed)",
  "timestamp": "2026-01-30T16:25:19.524Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (1142s elapsed)",
  "timestamp": "2026-01-30T16:25:49.586Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (1172s elapsed)",
  "timestamp": "2026-01-30T16:26:19.585Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (1202s elapsed)",
  "timestamp": "2026-01-30T16:26:49.586Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (1232s elapsed)",
  "timestamp": "2026-01-30T16:27:19.587Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (1262s elapsed)",
  "timestamp": "2026-01-30T16:27:49.587Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (1292s elapsed)",
  "timestamp": "2026-01-30T16:28:19.608Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (1322s elapsed)",
  "timestamp": "2026-01-30T16:28:49.667Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (1353s elapsed)",
  "timestamp": "2026-01-30T16:29:19.812Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (1383s elapsed)",
  "timestamp": "2026-01-30T16:29:49.859Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (1413s elapsed)",
  "timestamp": "2026-01-30T16:30:19.934Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (1443s elapsed)",
  "timestamp": "2026-01-30T16:30:50.033Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (1473s elapsed)",
  "timestamp": "2026-01-30T16:31:20.035Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (1503s elapsed)",
  "timestamp": "2026-01-30T16:31:50.035Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (1533s elapsed)",
  "timestamp": "2026-01-30T16:32:20.035Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (1563s elapsed)",
  "timestamp": "2026-01-30T16:32:50.036Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (1593s elapsed)",
  "timestamp": "2026-01-30T16:33:20.036Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (1623s elapsed)",
  "timestamp": "2026-01-30T16:33:50.039Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (1653s elapsed)",
  "timestamp": "2026-01-30T16:34:20.100Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (1683s elapsed)",
  "timestamp": "2026-01-30T16:34:50.273Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (1713s elapsed)",
  "timestamp": "2026-01-30T16:35:20.348Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (1743s elapsed)",
  "timestamp": "2026-01-30T16:35:50.453Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (1773s elapsed)",
  "timestamp": "2026-01-30T16:36:20.502Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (1803s elapsed)",
  "timestamp": "2026-01-30T16:36:50.636Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (1833s elapsed)",
  "timestamp": "2026-01-30T16:37:20.702Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (1863s elapsed)",
  "timestamp": "2026-01-30T16:37:50.767Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (1894s elapsed)",
  "timestamp": "2026-01-30T16:38:20.821Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (1924s elapsed)",
  "timestamp": "2026-01-30T16:38:50.957Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (1954s elapsed)",
  "timestamp": "2026-01-30T16:39:21.019Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (1984s elapsed)",
  "timestamp": "2026-01-30T16:39:51.054Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (2014s elapsed)",
  "timestamp": "2026-01-30T16:40:21.148Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (2044s elapsed)",
  "timestamp": "2026-01-30T16:40:51.232Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (2074s elapsed)",
  "timestamp": "2026-01-30T16:41:21.275Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (2104s elapsed)",
  "timestamp": "2026-01-30T16:41:51.275Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (2134s elapsed)",
  "timestamp": "2026-01-30T16:42:21.281Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (2164s elapsed)",
  "timestamp": "2026-01-30T16:42:51.283Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (2194s elapsed)",
  "timestamp": "2026-01-30T16:43:21.318Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (2224s elapsed)",
  "timestamp": "2026-01-30T16:43:51.385Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (2254s elapsed)",
  "timestamp": "2026-01-30T16:44:21.448Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (2284s elapsed)",
  "timestamp": "2026-01-30T16:44:51.531Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (2314s elapsed)",
  "timestamp": "2026-01-30T16:45:21.592Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (2344s elapsed)",
  "timestamp": "2026-01-30T16:45:51.713Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (2375s elapsed)",
  "timestamp": "2026-01-30T16:46:21.789Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (2405s elapsed)",
  "timestamp": "2026-01-30T16:46:51.939Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (2435s elapsed)",
  "timestamp": "2026-01-30T16:47:22.034Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (2465s elapsed)",
  "timestamp": "2026-01-30T16:47:52.104Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (2495s elapsed)",
  "timestamp": "2026-01-30T16:48:22.195Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (2525s elapsed)",
  "timestamp": "2026-01-30T16:48:52.256Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (2555s elapsed)",
  "timestamp": "2026-01-30T16:49:22.358Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (2585s elapsed)",
  "timestamp": "2026-01-30T16:49:52.358Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (2615s elapsed)",
  "timestamp": "2026-01-30T16:50:22.359Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (2645s elapsed)",
  "timestamp": "2026-01-30T16:50:52.360Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' failed after 2659s: MCP error -32001: AbortError: The operation was aborted.",
  "timestamp": "2026-01-30T16:51:06.191Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Calling MCP tool: codex",
  "timestamp": "2026-01-30T16:51:21.784Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (30s elapsed)",
  "timestamp": "2026-01-30T16:51:51.784Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (60s elapsed)",
  "timestamp": "2026-01-30T16:52:21.785Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (90s elapsed)",
  "timestamp": "2026-01-30T16:52:51.785Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (120s elapsed)",
  "timestamp": "2026-01-30T16:53:21.789Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (150s elapsed)",
  "timestamp": "2026-01-30T16:53:51.792Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' still running (180s elapsed)",
  "timestamp": "2026-01-30T16:54:21.792Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' failed after 208s: MCP error -32000: Connection closed",
  "timestamp": "2026-01-30T16:54:50.571Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Starting connection with timeout of 300000ms",
  "timestamp": "2026-01-30T16:55:14.523Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Successfully connected to stdio server in 128ms",
  "timestamp": "2026-01-30T16:55:14.650Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Connection established with capabilities: {\"hasTools\":true,\"hasPrompts\":false,\"hasResources\":false,\"serverVersion\":{\"name\":\"codex-mcp-server\",\"title\":\"Codex\",\"version\":\"0.92.0\"}}",
  "timestamp": "2026-01-30T16:55:14.650Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Calling MCP tool: codex",
  "timestamp": "2026-01-30T16:55:14.650Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}
{
  "debug": "Tool 'codex' failed after 3s: MCP error -32001: AbortError: The operation was aborted.",
  "timestamp": "2026-01-30T16:55:18.177Z",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "cwd": "/Users/thomas/Dev/myproject"
}

thomaswitt · 5 months ago

@etraut-openai I also found this debug output in /private/tmp/...claude../tasks/, in case that helps....

{
  "parentUuid": "779944d3-055d-4e70-95c2-bc1cc5569cb6",
  "isSidechain": true,
  "userType": "external",
  "cwd": "/Users/thomas/Dev/myproject",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "version": "2.1.25",
  "gitBranch": "264-ingestion",
  "agentId": "afa4c31",
  "slug": "stateful-weaving-pancake",
  "message": {
    "model": "claude-opus-4-5-20251101",
    "id": "msg_01Fn1cbUSCFRhgER3VLbQjL6",
    "type": "message",
    "role": "assistant",
    "content": [
      {
        "type": "tool_use",
        "id": "toolu_01KFTifai2R3nqagY2Qui163",
        "name": "mcp__codex__codex",
        "input": {
          "prompt": "You are reviewing a [...shortened...]",
          "cwd": "/Users/thomas/Dev/myproject"
        },
        "caller": {
          "type": "direct"
        }
      }
    ],
    "stop_reason": null,
    "stop_sequence": null,
    "usage": {
      "input_tokens": 3,
      "cache_creation_input_tokens": 814,
      "cache_read_input_tokens": 53067,
      "cache_creation": {
        "ephemeral_5m_input_tokens": 0,
        "ephemeral_1h_input_tokens": 814
      },
      "output_tokens": 2,
      "service_tier": "standard"
    }
  },
  "requestId": "req_011CXe8KRzESAv3ZF5amaWKf",
  "type": "assistant",
  "uuid": "8306e5d7-6c65-4b0d-80d9-4bc56cadb885",
  "timestamp": "2026-01-30T19:38:39.940Z"
}
{
  "parentUuid": "8306e5d7-6c65-4b0d-80d9-4bc56cadb885",
  "isSidechain": true,
  "userType": "external",
  "cwd": "/Users/thomas/Dev/myproject",
  "sessionId": "76a784c5-ffe7-4bcc-9e34-722017cab969",
  "version": "2.1.25",
  "gitBranch": "264-ingestion",
  "agentId": "afa4c31",
  "slug": "stateful-weaving-pancake",
  "type": "progress",
  "data": {
    "type": "mcp_progress",
    "status": "started",
    "serverName": "codex",
    "toolName": "codex"
  },
  "toolUseID": "toolu_01KFTifai2R3nqagY2Qui163",
  "parentToolUseID": "toolu_01KFTifai2R3nqagY2Qui163",
  "uuid": "b58b00b4-596f-4809-9f3a-82dd88d916b8",
  "timestamp": "2026-01-30T19:38:40.051Z"
}

After a while, this file disappears, but claude still says codex - codex (MCP)(prompt: "You are reviewing...
So maybe the commuication that the job is done doesnt go well?

Penlect · 4 months ago

I can reproduce a narrower root cause for this on codex-cli 0.114.0.

This is not a full MCP handshake failure. initialize and tools/list succeed. The hang is specifically that codex mcp-server never replies to:

resources/list
resources/templates/list

That explains why /mcp wedges: the snapshot path waits for tools, resources, and resource templates together, so tools may already be available but the overall /mcp request stays blocked until the resource timeout expires.

Minimal JSON-RPC repro

This reproduces against a command that launches codex ... mcp-server over stdio.

Control: `initialize` and `tools/list` work

python3 - <<'PY' | timeout 15s <command that launches codex mcp-server>
import json
msgs = [
  {
    "jsonrpc": "2.0",
    "id": 0,
    "method": "initialize",
    "params": {
      "capabilities": {"elicitation": {"form": {}}},
      "clientInfo": {
        "name": "codex-mcp-client",
        "version": "0.114.0",
        "title": "Codex"
      },
      "protocolVersion": "2025-06-18"
    }
  },
  {
    "jsonrpc": "2.0",
    "method": "notifications/initialized"
  },
  {
    "jsonrpc": "2.0",
    "id": 1,
    "method": "tools/list",
    "params": {}
  }
]
for msg in msgs:
    print(json.dumps(msg), flush=True)
PY
````

Observed:

* `initialize` responds immediately
* `tools/list` responds immediately

### Failure: `resources/list` never responds

```bash
python3 - <<'PY' | timeout 8s <command that launches codex mcp-server>
import json
msgs = [
  {
    "jsonrpc": "2.0",
    "id": 0,
    "method": "initialize",
    "params": {
      "capabilities": {"elicitation": {"form": {}}},
      "clientInfo": {
        "name": "codex-mcp-client",
        "version": "0.114.0",
        "title": "Codex"
      },
      "protocolVersion": "2025-06-18"
    }
  },
  {
    "jsonrpc": "2.0",
    "method": "notifications/initialized"
  },
  {
    "jsonrpc": "2.0",
    "id": 2,
    "method": "resources/list",
    "params": {}
  }
]
for msg in msgs:
    print(json.dumps(msg), flush=True)
PY

Observed:

initialize responds
no response is ever sent for resources/list before timeout kills the pipeline

Failure: `resources/templates/list` never responds

Same setup, replacing the last request with:

{"jsonrpc":"2.0","id":3,"method":"resources/templates/list","params":{}}

Observed:

initialize responds
no response is ever sent for resources/templates/list

Source-level explanation

Current source appears to explain this:

ClientRequest::ListResourcesRequest and ClientRequest::ListResourceTemplatesRequest are accepted
handle_list_resources() and handle_list_resource_templates() only log and return
those handlers do not receive RequestId
unlike implemented handlers, they never call send_response(...) or send_error(...)

So the server is silently accepting the request and then never replying.

Requested fixes

Server-side

For resources/list and resources/templates/list, please either:

return valid empty results, or
return an explicit JSON-RPC error such as METHOD_NOT_FOUND

The current behavior of accepting the request and never replying is a protocol bug.

Client-side

/mcp should not block tool listing on optional resource enumeration.

Even if one server:

lacks resource capability
returns method-not-found for resource methods
or is slow/broken on resource enumeration

/mcp should still render tools and remain responsive.

This also looks related to the broader “Codex over-indexes on resources/list” issue family for tool-only MCP servers.

Codex CLI hangs when configured to use codex mcp-server as an MCP server

What version of Codex is running?

What subscription do you have?

Which model were you using?

What platform is your computer?

What issue are you seeing?

What steps can reproduce the bug?

What is the expected behavior?

Additional information

11 Comments

Minimal JSON-RPC repro

Control: initialize and tools/list work

Failure: resources/templates/list never responds

Source-level explanation

Requested fixes

Server-side

Client-side

Control: `initialize` and `tools/list` work

Failure: `resources/templates/list` never responds