›_ Codex Issues
Codex Issues / #2434

Session continuity not working - no session ID returned from initial calls

Resolved 💬 4 comments Opened Aug 18, 2025 by zhendalf Closed Feb 23, 2026
💡 Likely answer: A maintainer (etraut-openai, contributor) responded on this thread — see the highlighted reply below.

Description

When using Codex through an MCP (Model Context Protocol) integration, session continuity doesn't work because the initial Codex call doesn't return a session ID that can be used for subsequent conversation turns.

Expected Behavior

Based on the MCP integration design:

  1. Initial call to Codex should return both the response text AND a session ID
  2. Subsequent calls should be able to use this session ID to continue the conversation with maintained context

Actual Behavior

  1. Initial Codex call only returns the text response, no session ID
  2. Attempting to continue the conversation fails with "Session not found" errors
  3. Context is lost between calls

Steps to Reproduce

  1. Start a Codex conversation with an initial prompt including context to remember:

``
"Hello! My favorite color is blue. Please remember this."
``

  1. Attempt to continue the conversation with a follow-up that references the context:

``
"What was my favorite color that I mentioned earlier?"
``

  1. The continuation fails because there's no session ID to reference

Impact

This prevents building stateful, multi-turn conversations with Codex, which is essential for:

  • Complex coding tasks that require iterative refinement
  • Maintaining context across multiple related questions
  • Building conversational AI experiences with Codex

Possible Solutions

  1. Return session IDs: Modify Codex to return a session identifier along with each response
  2. Document session management: If session management exists but works differently, provide documentation on the correct approach
  3. Stateless context passing: If sessions aren't supported, document how to pass previous context in subsequent calls

Environment

  • Using Codex through MCP (Model Context Protocol) integration
  • Testing with both sync and async execution modes

Additional Context

The MCP wrapper for Codex expects session functionality (with sessionId parameters), suggesting this was intended to work but may have an implementation gap between what the MCP server expects and what Codex provides.

Would appreciate guidance on whether session continuity is supported and if so, how to properly implement it.

View original on GitHub ↗

4 Comments

Faolain · 1 year ago

Threw this together which works for me locally https://github.com/openai/codex/pull/2449

@ebeloded if you wish to test my changes quickly you can run it locally via:

  • Clone my repo, and git checkout my Faolain:fix/sessionId-inclusion branch
  • Run cd <Directory>/codex/codex-rs && cargo build --release --bin codex-mcp-server
  • From there you can simply check the codex/code-rs/target/release folder which should have the codex-mcp-server binary which you can run as is.

If you want to get some nice interactivity as a followup:

  • In terminal run export PATH="$PATH:/Users/<Directory>/codex/codex-rs/target/release" to ensure it's available in your path (make sure you built it in the previous step)
  • Then run npx @modelcontextprotocol/inspector within the same terminal, this will open a browser where you can test the newly created mcp server binary
  • On the left where it says command, write codex-mcp-server which is the same binary we just created and press connect

<img width="233" height="424" alt="Image" src="https://github.com/user-attachments/assets/b29e8d8e-9aa1-4c61-b2e2-0ad2d4308434" />

  • Under Tools, tap list_tools

<img width="701" height="224" alt="Image" src="https://github.com/user-attachments/assets/c3bd1607-0d64-4fd1-863f-3b75655f5ed3" />

which will now show codex and codex-reply

  • Tap codex, write your prompt, you will get a sessionId in the structured response

<img width="1362" height="874" alt="Image" src="https://github.com/user-attachments/assets/9aecfe90-d7a3-4727-b492-ffe8887f90e1" />

  • Tap the codex-reply tool and provide the sessionId you got back (it will be your own unique session and different from mine)

<img width="2814" height="1170" alt="Image" src="https://github.com/user-attachments/assets/2bb6c3b5-96b6-4734-8e81-0f221baaa5ad" />

Tada. If you have any questions codex might be able to help better hehe

guersam · 11 months ago

I think it's implemented in https://github.com/openai/codex/pull/3219 and will be released with v0.32.0 in a few days

guersam · 11 months ago

Sorry for the misleading comment. Although #3219 introduced more consistent foundations with conversation id, but currently it seems to be only exposed in session_configured MCP event that's not being utilized by many MCP clients yet.

etraut-openai contributor · 6 months ago

This was addressed a while ago, just forgot to close the issue.