›_ Codex Issues
Codex Issues / #15508

MCP tools disappear in existing Codex sessions after reload or time, but work in new sessions

Resolved 💬 7 comments Opened Mar 23, 2026 by hiphoplucas Closed Jul 2, 2026
💡 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)?

26.318.11754

What subscription do you have?

ChatGPT Plus (Codex via VS Code extension)

What platform is your computer?

Microsoft Windows NT 10.0.26200.0

What issue are you seeing?

MCP servers are working correctly, but after some time, an existing Codex chat session stops being able to use them.

This happens even though nothing changed in the configuration.

What happens

  • MCP works normally when I start a new chat
  • After some time (or after reopening VS Code later), the same chat loses access to MCP tools
  • Codex says MCP is not available in that session
  • But MCP servers are still listed and enabled in Codex Settings
  • codex mcp list also shows everything correctly

If I start a new chat, MCP works again immediately.

Expected behavior

MCP tools should either:

  • keep working in the same session, or
  • automatically refresh, or
  • clearly indicate that the session needs to be restarted

Why this is a problem

This breaks long-running chats where I already have a lot of context, because I’m forced to start a new session to use MCP again.

Additional note

This feels like MCP tools are only loaded when the chat starts and never refreshed afterward.

What steps can reproduce the bug?

  1. Open VS Code with Codex extension installed
  2. Start a new Codex chat session
  3. Confirm that MCP tools are available and working normally
  4. Continue using the same chat session for some time OR close and reopen VS Code later
  5. Resume the same chat session
  6. Try to use MCP tools again

Result

  • MCP tools are no longer available in that session
  • Codex reports that MCP is not loaded or cannot be used
  • MCP servers are still listed and enabled in Codex Settings
  • Running codex mcp list shows all servers correctly

Workaround

  • Start a new chat session → MCP works immediately again

Notes

  • No changes were made to MCP configuration
  • This seems to be tied to session lifecycle or context persistence
  • Happens consistently when resuming older chats

What is the expected behavior?

_No response_

Additional information

_No response_

View original on GitHub ↗

7 Comments

github-actions[bot] contributor · 3 months ago

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

  • #15268
  • #15267
  • #14144
  • #14991

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etraut-openai contributor · 3 months ago

If you're able to repro this problem, please use /feedback to upload the logs and session details, then post the thread ID here.

edisonqu · 3 months ago

019dafcd-b677-7ec2-bd3d-00f9926c8913

edisonqu · 3 months ago

@etraut-openai

pavlo-tkhir · 2 months ago

I have the exact same problem. Forking the thread fixes the issue. I can continue using MCP in the forked thread.

A bit of the context from my side:

  • I'm using Codex desktop app on Mac, Version 26.429.61741 (2429)
  • The MCP that stops working is configured on the project level (not global)
innerbytes · 1 month ago

Happens all the time: 019ed073-5d36-7320-b8d6-f9ba178d3866

erictioh · 16 days ago

i have exactly same problem, oftenly after i left the session with multiple network discconection, laptop sleep, and rewakeup, then the existing session will sees no MCP and it will fall back to using curl to call the mcp.

when that scenario occured, simply creating new chat window will work again for MCP.