codex-sidecar

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A sidecar CLI that lets Claude Code keep talking to the same Codex thread.

Claude Code is the primary executor. Codex Sidecar is the reviewer / design partner sitting next to it. Repeated ask calls from the same project directory continue the same Codex-side context.

Install

npm install -g codex-sidecar
npx skills add nora/codex-sidecar

Run npx skills add from the project root where you want the skill installed. Add --global only if you want a global install.

Requirements: Node.js 22+ and OpenAI Codex CLI.

Use from Claude Code

Use $codex-sidecar to review this design and list the top 3 risks.

Use $codex-sidecar to focus on the second risk and suggest the smallest safe fix.

The skill calls codex-sidecar status/start/ask/reset/stop under the hood.

CLI

codex-sidecar start
codex-sidecar ask "Review this implementation and point out likely regressions."
codex-sidecar ask "Continue from your previous answer and propose a minimal fix."
codex-sidecar status
codex-sidecar reset
codex-sidecar ask "Start fresh under this new assumption: ..."
codex-sidecar stop
codex-sidecar --model gpt-5.5 --effort xhigh ask "Review this with a stronger model."

• start: create and save a new Codex thread
• ask <message>: send a message to the active thread and print Codex's reply
• status: show the saved thread state and effective model settings
• reset: archive the current thread and switch to a new one
• stop: archive the current thread and delete local state
• --model <model>: pass a specific model to Codex. Use latest or omit the option to use the Codex CLI default.
• --effort <effort>: pass a reasoning effort for turns. Default: high

Session model

• State file: .agents/state/codex-sidecar.json under each project directory
• Current limit: 1 directory = 1 sidecar session
• Default model: Codex CLI default, so it follows the latest model selected by the installed Codex CLI
• Default reasoning effort: high
• No daemon: each command launches codex app-server, resumes the saved thread, runs one operation, and exits

If ask fails with a state/resume error, run codex-sidecar status, then codex-sidecar reset if needed. Use codex-sidecar stop for a hard cleanup.