›_ Codex Issues
Codex Issues / #16834

Codex crashes on startup due to MCP "Method not found" errors (Windows)

Open 💬 3 comments Opened Apr 5, 2026 by LiMing0016
💡 Likely answer: A maintainer (github-actions[bot], contributor) responded on this thread — see the highlighted reply below.

What version of the Codex App are you using (From “About Codex” dialog)?

Latest version

What subscription do you have?

ChatGPT Pro

What platform is your computer?

Microsoft Windows NT 10.0.26200.0 x64

What issue are you seeing?

Issue

Codex crashes or becomes unusable during startup due to MCP server errors.

Error logs

Mcp error: -32601: Method not found

Failed to list resource templates/resources for MCP servers:

  • Vibma
  • openaiDeveloperDocs
  • playwright

Steps to reproduce

  1. Launch Codex
  2. MCP servers initialize automatically
  3. Errors appear and Codex fails / crashes

Expected behavior

Codex should either:

  • Skip incompatible MCP servers gracefully, or
  • Show a clear warning without crashing

Actual behavior

Codex fails during startup due to MCP connection errors.

Workaround

Disabling MCP servers in config.toml resolves the issue.

Notes

This appears to be caused by MCP server incompatibility or missing method support (-32601 Method not found).
Codex currently does not handle this failure gracefully.

What steps can reproduce the bug?

  1. Launch Codex on Windows
  2. Codex automatically initializes configured MCP servers
  3. MCP servers (Vibma, openaiDeveloperDocs, playwright) attempt to connect
  4. Errors appear: "Mcp error: -32601: Method not found"
  5. Codex crashes or becomes unusable

What is the expected behavior?

Codex should handle MCP server incompatibility gracefully.

If an MCP server does not support a method, Codex should:

  • Skip the server, or
  • Show a clear warning

It should not crash or block the entire application.

Additional information

Environment:

  • OS: Microsoft Windows NT 10.0.26200.0 x64 (Windows 11)
  • Codex running via desktop UI

View original on GitHub ↗

3 Comments

github-actions[bot] contributor · 4 months ago

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

  • #16271
  • #16689
  • #16087

Powered by Codex Action

LiMing0016 · 4 months ago

<img width="1578" height="1308" alt="Image" src="https://github.com/user-attachments/assets/7c24e1ce-df85-47ff-a98b-36f4c9ab4201" />

johnsilvavlogs · 4 months ago

Additional related datapoint from a separate Windows repro in #16502:

  • packaged Store/AppX launch succeeds, window appears, then the whole Codex process tree self-exits after about 46-55 seconds with no Codex-specific WER crash bucket
  • same startup-time MCP warnings appear (openaiDeveloperDocs, vercel: -32601 Method not found)
  • same session also shows 403 Forbidden responses for https://chatgpt.com/backend-api/plugins/list and .../plugins/featured
  • launching C:\Program Files\WindowsApps\OpenAI.Codex_26.325.3894.0_x64__2p2nqsd0c76g0\app\Codex.exe directly stays alive, so the bad behavior may be specific to the packaged/AppX lifecycle path

Cross-link for full repro details: #16502

I still cannot prove MCP warnings are the root cause, but the overlap seems strong enough that these issues should probably be triaged together.