Sandbox guide

Provider · checked 2026-10-28

Sprites

Persistent Fly.io microVMs that suspend after about 30 seconds idle and bill measured CPU and memory.

fly.io/sprites12 providersSources linked

Sprites are persistent Linux environments on Fly.io for agents, development and user-submitted code. Each is a dedicated microVM with a whole filesystem that survives between sessions.

The design assumes a computer that sleeps: a short idle window suspends it with memory frozen, and a longer idle period stops it and drops memory, keeping the disk.

At a glance

Who it is forDevelopers who want a long-lived Linux computer for an agent, with automatic sleep and usage-based billing rather than a reserved size.
IsolationDedicated microVM with hardware-level isolation. Root is available and Docker is reported to work, but Sprites do not run systemd: a built-in service manager starts services on wake.
SizesOne fixed shape: 8 vCPUs and 100 GB of storage, with memory assigned and autoscaled per Sprite. No published region selection, GPU or ARM option.

How it bills

ModelMeasured usage, with optional monthly plans that bundle allowances.
MeterActual CPU at $0.0385 per CPU-hour and actual memory at $0.021875 per GB-hour while awake; hot storage at $0.000683 per GB-hour and cold storage at $0.000027 per GB-hour.
While stoppedNo compute charge in warm or cold state, but cold storage is billed for as long as data is kept.
Plan feeThe pricing page says there are no plans; the product FAQ describes plans including Hero at $100 a month. Both are current.
MinimumNo published minimum. A one-time $30 trial credit per user and per organisation, which cannot pay a subscription fee.

How Sprites lets you try before paying is on Trials and free tiers.

Where it stands out

  • The whole filesystem persists between sessions, not one mounted folder.
  • Warm suspension keeps processes and resumes in 100–500 ms.
  • Wake on request is explicit.
  • Copy-on-write checkpoints that do not interrupt work.
  • Connectors keep credentials in the gateway, not the guest.

Using it without writing code

DashboardA dashboard exists for connector setup and a Gateway Playground that can fire a request without code.
Without codeLimited. The documented start path installs a CLI and opens a console; the no-code surface is connector testing, not running an agent.
SignupUses a Fly.io account. Card requirement, waitlist and trial duration are not published.
Docs and supportFly documentation covers lifecycle, checkpoints, networking and connectors. Support is community on lower plans and varies by plan.

Caveats and contradictions

Shown as the research found them. A contradiction means the provider's own pages disagree; an open question means the answer is not published.

  1. 01

    The pricing page and product FAQ disagree on plans Contradiction

    Pricing says there are no plans and nothing charged per Sprite; the FAQ describes plans including Hero at $100 a month with CPU, RAM and storage allowances.

  2. 02

    Warm-to-cold timing is not published Open question

    The idle window before warm suspension is about 30 seconds; how long before a Sprite drops to cold is not stated.

  3. 03

    Storage charges while idle are ambiguous Contradiction

    The FAQ says warm and cold are not billed, while the pricing page bills cold storage for as long as data is kept.

  4. 04

    No fork or create-from-checkpoint is documented Open question

    Checkpoints restore in place and overwrite current files; a live fork or clone is not established.

  5. 05

    Region selection and architecture are unpublished Open question

    No provider-confirmed region list, GPU option or CPU architecture statement was found.

Sources

The three shared workloads

List-price illustrations, not quotes

A · 1,000 short tasks

$14.58 to $65.92

8-vCPU Sprite, 4 GB average memory, no retained disk, deleted after each task

  • Memory166.67 h × 4 GB × $0.021875$14.58
  • CPU at zero to full use166.67 h × 0–8 × $0.0385$0–$51.33
  • The requested 2 vCPU / 4 GiB shape cannot be reserved; CPU is measured up to the 8-vCPU ceiling.
  • Actual storage writes and task time are excluded.

B · One always-on box

$153.67 to $378.51

8-vCPU Sprite, 8 GB average memory, 50 GB retained, 730 h

  • Memory730 × 8 × $0.021875$127.75
  • CPU at zero to full use730 × 0–8 × $0.0385$0–$224.84
  • Storage, hot plus cold730 × 50 × ($0.000683 + $0.000027)$25.92
  • An always-on workload must actively prevent idle sleep.
  • Whether hot and cold storage apply to the same bytes is not unambiguous in the provider's wording.

C · Three hours a day

$9.49 to $37.21

8-vCPU Sprite, 4 GB average memory, 20 GB retained, 90 active hours

  • Memory90 × 4 × $0.021875$7.88
  • CPU at zero to full use90 × 0–8 × $0.0385$0–$27.72
  • Storage, hot plus cold90 × 20 × $0.000683 + 720 × 20 × $0.000027$1.62
  • Idle time is compute-free, but the disk keeps billing while it exists.
  • Warm suspension keeps memory frozen; a longer idle period drops it and the next wake starts processes fresh.