Setup

Task

Set up the sandbox plugin on this host so the user can run Claude Code inside an isolated Docker/Podman container. The launcher is the cenci binary itself (cenci open / its cn alias, cenci sandbox <verb>) — no plugin symlink is installed by this skill. Two steps:

1. Verify the launcher — cenci resolves on PATH.
2. Build the container image via cenci sandbox build. Without a .cenci/Dockerfile in the repo, this builds the shared monolith cenci-sandbox:latest; with one present (as in this repo), it builds the per-repo cenci-sandbox-<slug>:latest instead.

Parse $ARGUMENTS

• --check-only — do step 1 only (verify), skip the image build.
• --build-only — do step 2 only (build), skip the verification.
• empty — do both.

Preconditions

Run these checks first. If any fails, report it clearly and stop — do not continue.

• Container runtime: command -v podman || command -v docker. If neither is found, tell the user to install Docker or Podman and stop.

Step 1 — Verify the launcher

Skip this step when --build-only was passed.

1. Check the binary and its alias:

   command -v cenci
   command -v cn
   

   • If cenci is missing, the plugin's first-session bootstrap has not run yet or ~/.local/bin is not on $PATH. Check with:

     case ":$PATH:" in *":$HOME/.local/bin:"*) echo on-path ;; *) echo not-on-path ;; esac
     

     If it is not on $PATH, warn the user to add it (e.g. export PATH="$HOME/.local/bin:$PATH" in their shell profile). If it is on $PATH but cenci still does not resolve, tell the user to re-run the cenci installer per the download-verify-run sequence in docs/getting-started.md (requires cosign; fails closed with no fallback to an unverified ref). The legacy curl -fsSL https://raw.githubusercontent.com/matteobortolazzo/cenci/main/install.sh | bash one-liner still works and re-execs itself through that same verified path — set CENCI_REF=main to explicitly opt into unsafe, unverified main instead and stop.
   • A missing cn alone is cosmetic — mention re-running the installer to create it, but continue.

2. Confirm the launcher answers: cenci version.

Step 2 — Build the image

Skip this step when --check-only was passed.

Run the build through the launcher so the same runtime-detection and asset-resolution logic is used:

cenci sandbox build

The build can take several minutes on first run (it pulls the base image and installs the SDKs). Report the outcome.

On failure, surface the runtime's error output and stop. cenci diagnose diagnoses a running/launched session, not an image build, so it does not help here — if the image builds successfully but a later cenci open launch fails instead, run cenci diagnose --name <session> for a read-only report (summarize it for the user rather than pasting it verbatim — it may include secrets, credentials, or host paths) and consult docs/failure-atlas.md and docs/error-codes.md for CENCI-* error codes and their suggested recovery commands before falling back to manual debugging.

Done

Summarize what was done and point the user at usage:

• cn (alias for cenci open) — launch Claude Code in the sandbox (full permissions inside the container)
• cenci open --agent codex — launch Codex in the sandbox instead
• cenci open --model <model> — launch with a specific model override
• cenci open --shell — open a shell for manual setup / troubleshooting
• cenci sandbox build — rebuild the image after changing the Dockerfile

See ${CLAUDE_PLUGIN_ROOT}/README.md for auth, MCP, cenci, and Docker-in-Docker details, and watch/README.md for the full CLI reference, including the one-token agent/model shortcut table.