Boxes.dev gives each Claude Code or Codex agent its own cloud Linux computer, copied from a snapshot of a working development environment. It is for engineers and teams who already run several coding agents at once. On a laptop those agents compete for CPU, memory, and ports, and they stop when the machine sleeps. With its YC Fall 2026 launch, the San Francisco company is offering three free months of Pro through boxes.dev/launch-yc. You start by pasting a prompt into Claude Code or Codex in a local project. The agent inspects that environment, drafts a setup plan, and, once you approve it, ports dependencies, services, and local configuration to a Template box in the cloud. Each task then runs on its own devbox, a fresh copy of that snapshot with a separate filesystem, ports, and database state, so the agent can reproduce a bug and test a fix in the running app. Boxes.dev runs the native harnesses unchanged and does not sell model tokens, so usage stays on the Claude or ChatGPT plan, or API key, you already pay for. Agents can be started from the desktop app, a phone, the terminal, Slack, Linear, a schedule, or an API, and port forwarding still lets you open the remote app on localhost. They can also message one another while they work. Nick Bushak and Drew Regitsky built Boxes.dev after spending the past year coding almost entirely with Claude Code and Codex. They met at MIT and previously worked together at Gem, the YC S17 recruiting company, where Bushak was co-founder and CTO and Regitsky was the first engineer. Bushak had earlier led engineering teams at Facebook.