code-airlock

code-airlock

Run Claude Code, Codex, OpenCode, or another coding agent in a disposable microVM, then review its work as normal git commits.

Code Airlock is a small wrapper around Docker Sandboxes for people who want to let coding agents work with fewer prompts without giving them direct access to the host machine.

Why Use It

Coding agents are most useful when they can install packages, run tests, inspect failures, and iterate without asking before every command. That is also exactly when you want a stronger boundary than process-level deny rules.

Code Airlock keeps the workflow simple:

You want	Code Airlock does
Run agents unattended	Starts the selected agent inside a Docker Sandbox microVM
Keep your local repo clean	Uses clone mode, so the host repo is mounted read-only
Review everything first	Pulls sandbox commits back with fetch, diff, and merge
Limit network access	Can apply a configurable allowlist for model APIs and package registries
Switch agents	Uses AGENT=claude, AGENT=codex, AGENT=opencode, and other Docker Sandbox agents

Why Not Just Use sbx Directly?

You can. Code Airlock is intentionally a thin wrapper around Docker Sandboxes, not a replacement for it.

Use sbx directly when you want full control over sandbox lifecycle, policies, kits, and one-off experiments. Use Code Airlock when you want the common coding-agent loop already wired together:

• clone mode by default
• stable sandbox naming per repo
• one-command agent startup
• repo-local AGENTS.md scaffolding
• fetch, diff, review, and merge commands for the sandbox branch
• a documented credential and network-policy path for Claude Code, Codex, and OpenCode

The point is to make the safe workflow boring and repeatable while still leaving sbx available underneath.

Quick Start

Install Docker Sandboxes first. On Linux:

curl -fsSL https://get.docker.com | sudo REPO_ONLY=1 sh
sudo apt-get install docker-sbx
sudo usermod -aG kvm $USER
newgrp kvm
sbx login

On macOS and Windows, follow Docker's official install guide.

Install Code Airlock with npm:

npm install -g code-airlock

Or use the standalone shell installer:

curl -fsSL https://raw.githubusercontent.com/Trivo25/code-airlock/main/install.sh | sh

The shell installer also adds a short codelock alias when that command is not already taken:

codelock up
codelock status
codelock attach

The npm package intentionally installs only code-airlock, because codelock is already an npm package name. Add a personal shell alias if you want the shorter command after npm install:

alias codelock=code-airlock

Or clone it manually:

git clone https://github.com/Trivo25/code-airlock.git
cd code-airlock
ln -s "$PWD/code-airlock" ~/.local/bin/code-airlock

The installer writes to ~/.local/bin by default. Choose another location with:

curl -fsSL https://raw.githubusercontent.com/Trivo25/code-airlock/main/install.sh | PREFIX=/usr/local/bin sh

Skip or rename the short alias:

curl -fsSL https://raw.githubusercontent.com/Trivo25/code-airlock/main/install.sh | CODE_AIRLOCK_INSTALL_ALIAS=0 sh
curl -fsSL https://raw.githubusercontent.com/Trivo25/code-airlock/main/install.sh | CODE_AIRLOCK_ALIAS=calock sh

Install - Agent

Already using a coding agent? Send it this:

Install Code Airlock in this environment, then run its first-run checks.

Use npm when available:
npm install -g code-airlock

If npm is unavailable, use:
curl -fsSL https://raw.githubusercontent.com/Trivo25/code-airlock/main/install.sh | sh

After install, make sure code-airlock is on PATH, then run:
code-airlock doctor
code-airlock --dry-run up

Do not start a real sandbox or change network policy unless I explicitly ask.

Run it from the repo you want the agent to work on:

cd ~/code/my-project
code-airlock doctor       # check sbx, virtualization, login, and git
code-airlock --dry-run up # preview the sbx commands without running them
code-airlock init         # optional: add starter AGENTS.md instructions
code-airlock up           # start Claude Code in a sandbox
code-airlock status       # see this repo's sandbox and tmux session

On a remote server, keep the agent running after your SSH connection closes:

code-airlock --tmux up # detach with Ctrl-b, then d
code-airlock attach    # reattach later

Use another agent:

AGENT=codex code-airlock up
AGENT=opencode code-airlock up

When the agent has made changes, review them from your host:

code-airlock fetch
code-airlock diff
code-airlock review      # optional: open a visual diff
code-airlock merge

How It Works

Code Airlock starts Docker Sandboxes with --clone:

1. Docker creates a private clone inside the sandbox VM.
2. The agent edits and commits inside that clone.
3. Your host repo stays read-only while the agent runs.
4. You fetch the sandbox branch into your local repo and review the diff.
5. You merge only when you are satisfied.

This means uncommitted sandbox edits do not come back through the normal flow. If needed, enter the sandbox and commit first:

code-airlock shell
git status
git add -A
git commit -m "describe the agent work"
exit

Then fetch and review from the host.

First-Run Checks

Most setup failures come from missing Docker Sandboxes, missing KVM/virtualization support, or an unauthenticated sbx CLI. Check before launching:

code-airlock doctor

Preview what Code Airlock would run without creating a sandbox:

code-airlock --dry-run up

Dry-run mode prints the sbx and git commands instead of running them. It is useful on machines that cannot run KVM yet, or when you want to understand the workflow before creating a VM.

Remote / Server Runs

Use --tmux to start the sandboxed agent inside a host-side tmux session:

code-airlock --tmux up

This attaches immediately so you can talk to the coding agent. To disconnect without stopping it, press Ctrl-b, then d. This detaches your terminal and leaves the agent running in the tmux session. Reattach later with:

code-airlock attach

For an unattended server run, start the tmux session without attaching:

code-airlock --tmux-detached up

The default session name is code-airlock-<sandbox-name>. Override it with:

TMUX_SESSION=agent-work code-airlock --tmux up
TMUX_SESSION=agent-work code-airlock attach

For a visual review, use:

code-airlock review

This fetches the sandbox branch and opens a Git directory diff using VS Code by default. Your working tree is not modified by the review command.

Use another Git difftool:

REVIEW_TOOL=opendiff code-airlock review
REVIEW_TOOL=vimdiff code-airlock review

Agent Instructions

Agents work better when the repo contains concise project instructions. Code Airlock can create a starter file:

code-airlock init

This writes AGENTS.md in the target repo only if one does not already exist. code-airlock up will mention the command when no AGENTS.md is present, but it will not silently modify your working tree.

Authentication

Model credentials should go through Docker Sandboxes' secret manager or host-side auth flow, not be pasted into the VM.

Common setup:

sbx secret set -g anthropic          # Claude Code API key
sbx secret set -g openai --oauth     # Codex OAuth
sbx secret set -g openai             # Codex/OpenCode API key

Agent-specific notes:

Agent	Authentication
Claude Code	Run code-airlock up and use /login inside Claude, or store an Anthropic key with sbx secret set -g anthropic
Codex	Use sbx secret set -g openai --oauth, sbx secret set -g openai, or export OPENAI_API_KEY before launch
OpenCode	Store the provider keys you use, such as openai, anthropic, google, xai, groq, aws, or openrouter

Sandboxes do not carry user-level config such as ~/.claude or ~/.codex into the VM by design. Put project-level config in the repo if the agent needs it.

GitHub Credentials

Code Airlock does not need GitHub credentials for the normal fetch/diff/merge review loop.

Give the sandbox GitHub access only if you want the agent to use gh, open pull requests, create issues, or push directly from inside the VM:

echo "$(gh auth token)" | sbx secret set -g github

Global secrets apply when a sandbox is created. For an existing sandbox, either recreate it or scope the token to that sandbox:

echo "$(gh auth token)" | sbx secret set sandbox-sbx-my-project github

If you use SSH remotes, Docker Sandboxes can forward your host SSH agent when SSH_AUTH_SOCK is set. The private key stays on the host; sandboxed processes can request signatures but cannot read the key.

Network Policy

On first use, Code Airlock initializes Docker Sandboxes' global network policy to balanced if it has not been initialized yet.

Override that default:

GLOBAL_NETWORK_POLICY=deny-all code-airlock up
GLOBAL_NETWORK_POLICY=allow-all code-airlock up

For stricter runs, use:

code-airlock lockdown

Run lockdown after the sandbox exists. It sets Docker Sandboxes' global default to deny-all, then applies Code Airlock's allowlist to the named sandbox.

Undo the global policy change with:

code-airlock unlock

unlock runs sbx policy reset, which restores Docker Sandboxes' policy defaults.

The default allowlist covers Anthropic, OpenAI, GitHub, and npm:

api.anthropic.com,*.anthropic.com,api.openai.com,*.openai.com,github.com,*.github.com,codeload.github.com,objects.githubusercontent.com,registry.npmjs.org,*.npmjs.org

Customize it with sandbox.conf:

# sandbox.conf
AGENT=codex
ALLOW=api.openai.com,*.openai.com,github.com,*.github.com,registry.npmjs.org,*.npmjs.org

If a download fails, inspect blocked hosts:

code-airlock net

Headless Runs

Pass agent arguments after --.

Claude Code:

code-airlock up -- -p "add pagination to the users endpoint and run the test suite"

Codex:

AGENT=codex code-airlock up -- --dangerously-bypass-approvals-and-sandbox "fix the build"

OpenCode defaults to a TUI. Pass OpenCode's own flags after -- when you need session-specific behavior.

Configuration

Copy sandbox.conf.example to sandbox.conf and edit:

cp sandbox.conf.example sandbox.conf

Useful settings:

SANDBOX_NAME=sbx-my-project
AGENT=claude
REPO_DIR=/absolute/path/to/repo
GLOBAL_NETWORK_POLICY=balanced
REVIEW_TOOL=vscode
TMUX_SESSION=code-airlock-sbx-my-project
TMUX_ATTACH=1
ALLOW=api.anthropic.com,*.anthropic.com,github.com,*.github.com

sandbox.conf is git-ignored.

Commands

Command	What it does
up [-- agent-args]	Create and start the sandbox in clone mode with the selected agent
doctor	Check sbx, virtualization/KVM, git, daemon reachability, and login status
status	Show this repo's sandbox and tmux session status
attach	Attach to this repo's Code Airlock tmux session
init	Create a starter AGENTS.md in the target repo
shell	Open a shell inside the running sandbox
fetch	Fetch the sandbox commits into your local repo
diff [base]	Fetch, then show base..sandbox-<name>/base
review [base]	Fetch, then open a visual Git difftool review
merge [base]	Fetch, then merge the sandbox branch into base
net	Show allowed and blocked network hosts
stop	Stop the sandbox but keep its VM and commits
rm	Remove the sandbox and repo tmux session after offering to fetch commits
lockdown	Set the global policy to deny-all and apply the allowlist to an existing sandbox
unlock	Reset Docker Sandboxes policies with sbx policy reset

Global option:

Option	What it does
--dry-run	Print commands instead of running them
--tmux	Run up inside a host-side tmux session and attach
--tmux-detached	Run up inside a detached host-side tmux session

Security Notes

• The isolation boundary is the Docker Sandbox microVM, not the agent's own permission model.
• Clone mode keeps your host repo mounted read-only.
• lockdown sets the default network policy to deny-all for all Docker Sandboxes. Revert with code-airlock unlock.
• Keep the allowlist as narrow as the task allows. Allowed hosts remain possible egress paths.
• Do not give the sandbox broad credentials unless the task truly requires them.
• code-airlock rm deletes the sandbox clone. Fetch or push anything you want to keep first.

Requirements

• macOS: Apple Silicon
• Linux: KVM enabled (lsmod | grep kvm)
• Windows: Windows 11 with Hypervisor Platform, run under WSL2
• Git
• Docker Sandboxes CLI (sbx)

License

MIT. See LICENSE.