Fly.io Machines

How Fly.io Machines works

Fly.io Machines are hardware-virtualized microVMs, marketed as Sprites for agent use. Each keeps a persistent ext4 filesystem, so files survive across runs, and you can checkpoint in roughly 300ms. Stop a Machine and it costs nothing while idle. There is a native MCP endpoint, GPUs are available, and the platform spans global regions, so you can place compute near users or data. It is a low-level VM primitive rather than an agent framework: flexible and cheap to idle, but you assemble the workflow around it yourself.

Pricing in practice & watch-outs

Fly.io bills usage plus concurrency plans, at roughly $0.07 per vCPU-hour, and stopped Machines cost nothing, which keeps idle-heavy agent fleets cheap. The tradeoff is labor. This is a general-purpose VM primitive, not an agent SDK, so snapshot logic, session management and the agent glue are yours to build. The native MCP endpoint helps, but you will not find the drop-in evaluation harnesses or SDK conveniences that the coding-agent-focused vendors ship. Choose it when you want a low-level, MCP-native building block and are comfortable doing the assembly.