Agents that ask before they act.
Harness is a local-first runtime for coding agents. A Rust kernel runs them in a sandbox on your own Mac, against your own repositories. You plan the work with them, watch it run, decide every risky step, and review, revert, fork or replay whatever changed.
What Harness promises, in the words it uses on screen.
The person stays in control
Every risky step asks. Stop always works. Nothing is approved on your behalf.
Approved by you · once
Local first
The work, the data and the audit trail stay on your machines.
Agents work in this folder on your Mac. Nothing else is connected.
Show the real state
Running, waiting, stopped or missing, in words. Estimates say they are estimates.
Waiting 12s · agent paused until you decide
The kernel decides, the clients show
Risk and outcomes come from the kernel. You will never see a 0 to 100 risk score.
High risk · writes outside the workspace
Every turn can be undone
Review, revert, fork or replay any turn from its checkpoint.
Restores app.ts to how it was before this turn. Later changes to that file in this agent are lost.
One model across Mac and iPhone
The same moments on both, each adapted to its platform. Approve from your phone when you step away.
ledgerline · main · iPhone → Mac · 4s
The agent works. When a step is risky, it stops and asks you.
This run was generated for you from the page's seed. The plan streams in, then the kernel holds the risky step until you decide. Approve it, deny it, or stop the agent. Afterwards you can revert the whole turn.
Native apps on both, talking to the same kernel.
Plan, watch and decide at your desk. When you step away, the iPhone app shows the same approvals and the same stop button.
One kernel on your Mac. The apps are windows onto it.
The kernel runs agents in a sandbox against your repositories, keeps a checkpoint for every turn and writes the audit trail. The Mac and iPhone apps talk to it through its protocol, so either one can approve, deny or stop.
Put Harness on your Mac before it ships.
We are letting in a small group of engineers who already run coding agents and want them on a shorter leash.
- macOS app and kernel, with iPhone supervision in TestFlight
- Runs against your repositories, on your machine
- A direct line to the people building the kernel