Fly.io Sprites
Fly.io Sprites are persistent, stateful Linux virtual machines built as sandboxes for AI agents. Each Sprite is a hardware-isolated Firecracker microVM with a full Linux filesystem that survives across runs. Sprites scale to zero (hibernate when idle, wake on the next request) so agents can keep long-lived state and installed tools between sessions. They expose a REST and WebSocket API and are intended for executing untrusted or agent-generated code in isolation, with built-in features for checkpoints, file transfer, port forwarding, and outbound network policy.
| Pricing model | Pay-as-you-go, per-second billing on CPU and memory while running; no compute charge while the Sprite is hibernating |
|---|---|
| Pricing The headline compute price as the provider states it. Sorting ranks prices stated per vCPU over time, converted to hourly. Other pricing models sort after, unranked. | $0.07 per CPU-hour and $0.04375 per GB-hour of memory |
| Free while idle Whether a stopped, paused, or sleeping sandbox costs nothing. | ✓ |
| Elastic Resources flex with what the sandbox actually uses, and the bill follows: yes when the provider bills on active or observed use, no when capacity is reserved or allocated and billed while it runs. | ✕ |
| Memory snapshots Whether RAM state survives a pause and resume, not just disk. | ✕ |
| Wake on request Whether a stopped sandbox wakes automatically on inbound traffic. | ✓ |
| Start / resume Typical time from create or resume to running. Sorting ranks stated times, converted to seconds; claims with no figure sort after, unranked. | ~100-500 ms warm resume; ~1-2 s cold start |
| Max runtime The longest a sandbox may run. | No fixed limit |
| Isolation The isolation technology between sandboxes. | Firecracker microVM |
| GPUs Whether GPU instances are available for sandboxes. | ✕ |
| Docker Whether Docker containers can run inside the sandbox. | ✕ |
| SDKs | Go, JavaScript/TypeScript, Python, Elixir |
✓ yes · ✕ no · – no cited public fact.
Sprites intentionally drop OCI/Docker container images — every Sprite boots from a standard base image and software is installed directly on the filesystem. RAM state does not survive hibernation (only disk and network config persist), so any process the agent needs to keep alive across a sleep must be registered as a Sprites 'Service' that auto-restarts on wake.
Sources
- https://community.fly.io/t/how-to-get-docker-running-on-sprites/27168
- https://github.com/superfly/sprites-go
- https://github.com/superfly/sprites-js
- https://github.com/superfly/sprites-py
- https://github.com/superfly/sprites-ex
- https://docs.sprites.dev/api/dev-latest/
- https://fly.io/
- https://community.fly.io/t/sprite-constantly-stays-warm-also-any-way-to-reboot/26926
- https://docs.sprites.dev/concepts/checkpoints
- https://fly.io/blog/design-and-implementation/
- https://news.ycombinator.com/item?id=46634450
- https://docs.sprites.dev/
- https://docs.sprites.dev/working-with-sprites/
- https://community.fly.io/t/sprites-not-shutting-off/26793
Last verified 2026-08-16. Corrections land through the update log.