Getting Started

Prerequisites

• Podman (rootless mode recommended if you want SSH agent forwarding)
• An ANTHROPIC_API_KEY (for Claude Code) or OPENAI_API_KEY (for Codex)

Installation

Quick Install

curl -fsSL https://raw.githubusercontent.com/pthrasher/straightjacket/master/install.sh | sh

Detects your OS and architecture, downloads the latest release binary, and installs to /usr/local/bin.

Environment Variable	Description
SJ_INSTALL_DIR	Custom install directory (default: /usr/local/bin)
SJ_VERSION	Pin a specific version (e.g., v0.1.0)

From Source

git clone https://github.com/pthrasher/straightjacket.git
cd straightjacket
bun install
bun run build
cp build/sj /usr/local/bin/sj

Quick Start

cd your-project

# Launch Claude Code in a container
sj claude

# Launch Codex instead
sj codex

# Force rebuild the image (after changing presets/units)
sj claude --rebuild

# Use a different preset
sj codex --preset rust-wasm

# Just get a shell
sj shell

What Happens on First Run

When you run sj claude for the first time in a project:

1. Builds a container image tailored to your preset's units (Node, Rust, etc.)
2. Creates a sandboxed home directory for the agent at ~/.config/sj/harness-config/claude/
3. Syncs your git config into the container
4. Mounts your project at /workdirs/<project> inside the container
5. Launches the agent in full autonomous mode — no permission prompts

Subsequent runs reuse the cached image and persisted agent state — startup is near-instant.

How It Works

┌─────────────────────────────────────┐
│  Your Host                          │
│                                     │
│  $ sj claude                        │
│    │                                │
│    ├─ Resolve config & preset       │
│    ├─ Generate Dockerfile from units│
│    ├─ Build image (cached by hash)  │
│    ├─ Sync git config, SSH keys     │
│    └─ podman run ...                │
│         │                           │
│  ┌──────┴──────────────────────┐    │
│  │  Container                  │    │
│  │  • cap-drop=ALL             │    │
│  │  • no-new-privileges        │    │
│  │  • userns=keep-id           │    │
│  │  • /workdirs/project (rw)   │    │
│  │  • $HOME = sandboxed        │    │
│  │                             │    │
│  │  Claude Code (autonomous)   │    │
│  └─────────────────────────────┘    │
└─────────────────────────────────────┘

A container is not a magic shield

Straight Jacket prevents agents from trashing your host system or accessing files outside your project — but your project directory is mounted read-write. A rogue agent can still delete your entire codebase or overwrite files. Don't pass production credentials or secrets you wouldn't want an intern to have. Straight Jacket constrains the blast radius; it doesn't eliminate it. Use version control. Review diffs. Stay sharp.