Agent skill

codex-container-sandbox

Run Codex CLI inside a Podman container with full internet access but filesystem exposure limited to the repo root + explicit bind mounts; use when you want yolo/web-search without giving the agent access to your whole host filesystem.

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Install this agent skill to your Project

npx add-skill https://github.com/majiayu000/claude-skill-registry/tree/main/skills/development/codex-container-sandbox

SKILL.md

codex-container-sandbox

Use this when you want:

  • Full egress/network for codex (web search, fetching, etc.)
  • Tight filesystem boundaries via container bind mounts (repo root + explicit allowlist)

This repo contains a wrapper script intended to be installed as codex-container-sandbox.

Workflow

  1. Build the image

    From the repo root (this repository):

    bash
    podman build -t localhost/codex-container-sandbox:latest -f Containerfile .
    
  2. Install the wrapper

    bash
    install -m 0755 codex-container-sandbox ~/.local/bin/codex-container-sandbox
    
  3. (Optional) Configure extra mounts

    Create ~/.config/codex-container-sandbox/config.sh:

    bash
    CODEX_CONTAINER_SANDBOX_IMAGE="localhost/codex-container-sandbox:latest"
    
    # Extra read-only mounts (mapped under /home/codex/... if under $HOME)
    CODEX_CONTAINER_SANDBOX_RO_MOUNTS=(
      "$HOME/.local/bin"
    )
    
    # Extra read-write mounts
    CODEX_CONTAINER_SANDBOX_RW_MOUNTS=(
      "$HOME/.cache/uv"
      "$HOME/tmp"
    )
    
  4. Login once inside the container

    bash
    codex-container-sandbox --shell
    codex login
    
  5. Run the self-test (recommended)

    bash
    ./selftest.sh
    

    If this repo is vendored as a git submodule at ./codex-container-sandbox/ (for example in a dotfiles repo), either:

    • cd codex-container-sandbox && ./selftest.sh, or
    • run ./codex-container-sandbox/selftest.sh from the parent repo root.
  6. Run Codex

    bash
    codex-container-sandbox exec "Summarize this repo"
    

Safety notes

  • This wrapper runs Codex in full-yolo mode (--dangerously-bypass-approvals-and-sandbox) with full networking. Anything mounted into the container can be exfiltrated.
  • Keep mounts minimal; do not mount secrets, password stores, SSH keys, or large chunks of $HOME unless you intend to expose them.

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