Parallel coding agents,
each in its own sandbox
An isolated sandbox for every agent workstream, with its own dev server and URL. A microVM or a container, set up once per agent.
curl -sSL https://smolmachines.com/install.sh | bash
curl -fsSL https://raw.githubusercontent.com/BarakChamo/boxer/main/install.sh | sh
How it works
Install it into your agent
One command: boxer install claude-code, codex, or whichever agent you use.
Work as usual
Each workstream gets its sandbox when it starts, with dependencies installed and your dev server running.
Run as many as you want
Every new worktree, session or subagent can get its own sandbox. Finished ones are cleaned up.
A sandbox per workstream
One per git worktree by default, or one per agent session or subagent. Created when the work starts, cleaned up after.
Your agent doesn’t change
npm test, pytest and make run in the sandbox. Output and exit codes come back as usual.
No port clashes
Each worktree’s dev servers get their own ports, or named URLs like https://fix-ui.myapp.localhost.
MicroVM or container
A smolvm microVM with its own kernel and a network allowlist by default. Docker, podman or Apple container if you prefer.
Works with your setup
Your own images and devcontainer, and services like Postgres running in the sandbox.
Local and open source
Runs on your Mac or Linux machine. No account. Apache-2.0.
Compared with what you use now
| boxer | Agent’s built-in sandbox | A container per worktree | Cloud sandbox | |
| Separate ports and dev server per task | yes, automatic | no | yes, if you map ports | yes |
| Own kernel per task | yes, on smolvm | no | no | yes |
| Follows worktrees the agent creates | yes | n/a | no | no |
| Code stays on your machine | yes | yes | yes | no |
| Cost of one command | 33 ms | ~8 ms | ~29 ms | a network round trip |
Works with
Try it
curl -sSL https://smolmachines.com/install.sh | bash
curl -fsSL https://raw.githubusercontent.com/BarakChamo/boxer/main/install.sh | sh
boxer install claude-code