Concepts

What is a box?

A box is a dedicated cloud machine that runs one coding agent for you. It boots when you create it, bills only while it is running, and is yours alone until you destroy it.

A micro-VM of your own

Each box is its own Fly Machine — a hardware-virtualized micro-VM, one per box. Nobody else shares your box, and your agent cannot reach anyone else's; how that isolation is enforced is covered in Security.

What's inside

• A node:22-slim base image.
• Your agent — Codex or Claude Code.
• The OpenAgent sidecar, which dials out to our relay so any device can pick up the session — no inbound ports, no SSH.
• A /home/agent workspace holding your code and files, plus any instructions and skills from your template.

Sizes

Per-hour rates for each size are on the pricing page. Your rate is snapshotted onto the box when it is created, so a later price change never touches a box you are already running.

Billing, only while running

A box bills per second at its size's rate while it is running, and nothing while it is suspended. Billing is strictly prepaid — see pricing for how packs and metering work.

Suspend, wake, destroy

• Suspend — after 30 minutes idle a box suspends: its RAM and processes are frozen and its disk is preserved, but it stops billing.
• Wake — connect again and it resumes in a few seconds, exactly where it was.
• Destroy — destroying a box erases its disk. A suspended box keeps its disk; a destroyed box does not.

Network

By default your agent has open outbound access to the public internet — it needs it to install packages, clone repositories, and call your model provider. Two things are always blocked regardless of mode: the cloud metadata endpoint and every other tenant's box. You can lock a box down further with a per-template agent_network policy — an allowlist of hosts, or no egress at all. The details are in Security.