Render Sandboxes give every agent its own isolated Linux computer. Sandboxes starts in under a second and can run any agent or harness, like Claude Code or Codex. Your agent can also run your app with Docker Compose to test its changes. You decide which domains each sandbox can reach. When your agent goes idle, the sandbox suspends and compute charges stop. It wakes with files and memory intact. And you can reliably run thousands at once - all on the same platform as the rest of your app.