## Problem The built-in Codex Apps MCP client shares a future for the full startup operation: connect, complete `initialize`, fetch the initial tools, and return a usable client. Sharing deduplicates startup work, but it also memoizes terminal errors. After a transient connection, handshake, or initial `tools/list` failure, later tool builds observe the same failed future. The thread cannot reconnect after the backend recovers and continues serving its startup-time cached tool snapshot, which may be empty or stale. ## Fix When Apps MCP startup ends in an error, Codex starts bounded recovery without putting startup latency on tool-router construction: 1. The current tool build immediately continues with the cached startup snapshot. 2. After the initial failure is reported, Codex starts one fresh full startup attempt in the background. 3. Concurrent tool builds share that in-flight attempt and also continue with cached tools. 4. On success, the recovered client becomes active, refreshes the Apps tools cache, emits a `Ready` startup status, and is reused by later operations. 5. On failure, the cache remains unchanged and later tool builds may start another background attempt after exponential cooldown: 1s, 2s, 4s, 8s, 16s, then 30s maximum. Each recreated startup performs a fresh MCP `initialize` and uncached `tools/list`. The MCP client retains its existing bounded retries for retryable `initialize` and `tools/list` failures. This avoids adding the Apps startup timeout to every request during a sustained outage. ## Scope This is limited to the built-in Codex Apps MCP client: - no reconnects for user-configured MCP servers; - no cache deletion; and - no proactive refresh for a healthy client with stale tools. ## Tests Coverage verifies: - tool builds return cached tools without waiting for a blocked reconnect; - concurrent tool builds start only one background reconnect; - failed reconnects preserve cached tools and respect exponential cooldown; - a recovered client is retained and reused; and - a long-lived thread exposes recovered app tools on a later follow-up. Validation: - `just test -p codex-mcp` — 95 passed - `just test -p codex-core later_follow_up_uses_background_recovered_apps_after_mid_thread_startup_failures --no-capture` — passed - `just fix -p codex-mcp` - `just fmt`
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.
