When cloning a repo, we kept hitting the same wall: no Dockerfile, no dev container, no clear path to running it. Asking an agent to fix it directly on your system is risky, as it can clear Docker config, change kernel settings, downgrade packages without warning.
Keystone runs the agent inside a Modal sandbox with its own Docker daemon. It iterates until tests pass, then hands you a .devcontainer/ you can just check in. Now your repo knows how to run itself!