## Why
An MCP tool call can still be waiting for an elicitation response when
an environment update replaces the thread's MCP runtime.
Before this change:
```text
runtime A starts a tool call and asks the user
environment becomes ready, so runtime B is published
client answers the prompt through runtime B
runtime B cannot find runtime A's pending responder
```
The response is lost and the original tool call stays blocked.
## What changed
All MCP runtimes for one thread now share a small elicitation router:
```text
runtime A ---\
shared router: response token -> exact pending responder
runtime B ---/
```
When Codex surfaces an MCP elicitation, it assigns a unique opaque
response token. The router records which pending request owns that
token. A replacement runtime reuses the same router, so the latest
runtime can deliver a response to a request started by the previous
runtime.
The Codex-owned token also prevents two runtime connections that reuse
the same MCP server request ID from receiving each other's responses.
This does not retain or search old MCP managers. Only the pending
responder map is shared.
## Covered scenario
The integration test exercises the complete failure mode:
1. A thread starts while its selected environment is still unavailable.
2. A configured MCP server starts a tool call and asks the client for
input.
3. The environment becomes ready, causing Codex to publish a replacement
MCP runtime.
4. The client answers the original prompt after the replacement.
5. The original tool call receives that answer and completes.
A focused routing test also creates two runtimes with the same server
request ID and verifies that each response reaches the exact request
that emitted its token.
## Scope
This PR changes only elicitation response routing across MCP runtime
replacement. It does not change when runtimes are rebuilt, which
environments contribute MCP configuration, or how environment
availability is detected.
Codex CLI is a coding agent from OpenAI that runs locally on your computer.
If you want Codex in your code editor (VS Code, Cursor, Windsurf), install in your IDE.
If you want the desktop app experience, run
codex app or visit the Codex App page.
If you are looking for the cloud-based agent from OpenAI, Codex Web, go to chatgpt.com/codex.
Quickstart
Installing and running Codex CLI
Run the following on Mac or Linux to install Codex CLI:
curl -fsSL https://chatgpt.com/codex/install.sh | sh
Run the following on Windows to install Codex CLI:
powershell -ExecutionPolicy ByPass -c "irm https://chatgpt.com/codex/install.ps1 | iex"
Codex CLI can also be installed via the following package managers:
# Install using npm
npm install -g @openai/codex
# Install using Homebrew
brew install --cask codex
Then simply run codex to get started.
You can also go to the latest GitHub Release and download the appropriate binary for your platform.
Each GitHub Release contains many executables, but in practice, you likely want one of these:
- macOS
- Apple Silicon/arm64:
codex-aarch64-apple-darwin.tar.gz - x86_64 (older Mac hardware):
codex-x86_64-apple-darwin.tar.gz
- Apple Silicon/arm64:
- Linux
- x86_64:
codex-x86_64-unknown-linux-musl.tar.gz - arm64:
codex-aarch64-unknown-linux-musl.tar.gz
- x86_64:
Each archive contains a single entry with the platform baked into the name (e.g., codex-x86_64-unknown-linux-musl), so you likely want to rename it to codex after extracting it.
Using Codex with your ChatGPT plan
Run codex and select Sign in with ChatGPT. We recommend signing into your ChatGPT account to use Codex as part of your Plus, Pro, Business, Edu, or Enterprise plan. Learn more about what's included in your ChatGPT plan.
You can also use Codex with an API key, but this requires additional setup.
Docs
This repository is licensed under the Apache-2.0 License.
