Vercel Sandbox vs Fly.io Sprites
Answer in brief
Choose Vercel Sandbox for teams on Vercel and agent builders who want microVM isolation, active-CPU billing and credential brokering; choose Fly.io Sprites for long-running, stateful agent computers that should cost nothing while idle. Vercel Sandbox uses Firecracker microVM isolation; Fly.io Sprites uses MicroVM isolation.
Vercel Sandbox vs Fly.io Sprites at a glance
| Attribute | Vercel Sandbox | Fly.io Sprites |
|---|---|---|
| What it is | Firecracker microVM sandboxes on Vercel’s infrastructure, persistent by default and billed on active CPU, with fine-grained egress control. | Persistent, hardware-isolated Linux computers for AI agents with a durable 100 GB disk, checkpoints, and no compute charges while idle. |
| Isolation | Firecracker microVM with a dedicated kernel per sandbox | Dedicated microVM with hardware-level isolation (Fly docs); reported to be Firecracker-based |
| Open source | No (SDK and CLI Apache-2.0) | No (SDKs MIT) |
| Self-host / BYOC | No / No | No / No |
| SDKs | JavaScript/TypeScript, Python | JavaScript/TypeScript, Go, Python, Elixir |
| Cold start (vendor claim) | “Start in milliseconds” (vendor claim, no figure); snapshot resume faster than fresh start | Warm wake 100–500 ms with processes preserved; cold wake 1–2 s (vendor docs) |
| Max session | 5 min default; up to 45 min per session on Hobby and 24 hours on Pro/Enterprise; persistent sandboxes can be resumed indefinitely | No lifetime limit — a Sprite persists until destroyed and sleeps after ~30 s idle |
| Persistence | Persistent by default — filesystem auto-snapshotted on stop and restored on resume; manual snapshots; Drives (beta) and S3 mounts | 100 GB durable disk per Sprite that survives sleep; copy-on-write checkpoints (~1 s) with restore; memory preserved on warm pause |
| GPU | Not documented | No GPU option documented |
| Networking | Firewall modes allow-all, deny-all or domain/CIDR rules, updatable at runtime; credential brokering injects headers so secrets never enter the sandbox; public URLs for up to 15 ports | HTTPS URL per Sprite (org-private by default); outbound open by default with optional DNS-based domain allow/deny policy; connectors broker API credentials |
| Pricing | Active CPU $0.128/hour (billed only while CPU is used) + provisioned memory $0.0212/GB-hour + $0.60 per million creations, plus storage and transfer (iad1 rates) | Per second, compute only while active: $0.0385 per CPU-hour + $0.021875 per GB-hour memory; storage billed while idle |
| Compliance | Runs on Vercel infrastructure with SOC 2 Type II (company-wide) | Fly.io is SOC 2 Type 2; HIPAA BAA and DPA available (company-wide) |
| Best for | Teams on Vercel and agent builders who want microVM isolation, active-CPU billing and credential brokering | Long-running, stateful agent computers that should cost nothing while idle |
Verified November 8, 2026 from each provider’s documentation. Cold-start figures are vendor claims, not our measurements.
Which should you choose?
Choose Vercel Sandbox if…
- You deploy on Vercel or use the AI SDK
- You want secrets brokered outside the sandbox
- Your agents idle while waiting on models and you want active-CPU billing
- You want persistent-by-default microVMs
Choose Fly.io Sprites if…
- You want a persistent computer per agent or per user
- Your agents are idle most of the time and you want to pay only for active compute
- You want fast checkpoints and rollback
- You want Elixir or Go SDKs
Both are worth piloting with your own image and region. See the full Vercel Sandbox profile and Fly.io Sprites profile, or the complete comparison.
Frequently asked questions
Is Vercel Sandbox or Fly.io Sprites better for AI agents?
Neither is better for every workload. Vercel Sandbox is best for teams on Vercel and agent builders who want microVM isolation, active-CPU billing and credential brokering. Fly.io Sprites is best for long-running, stateful agent computers that should cost nothing while idle.
Which is open source, Vercel Sandbox or Fly.io Sprites?
Neither is open source.
How do Vercel Sandbox and Fly.io Sprites isolate code?
Vercel Sandbox: Firecracker microVM with a dedicated kernel per sandbox. Fly.io Sprites: Dedicated microVM with hardware-level isolation (Fly docs); reported to be Firecracker-based.
Sources
Cite this page
Agent Sandboxes. (2026). Vercel Sandbox vs Fly.io Sprites. agentsandboxes.org. Last reviewed November 8, 2026. https://agentsandboxes.org/compare/vercel-sandbox-vs-fly-sprites/
Found an error or a missing sandbox? Submit a correction — every entry links to the sources it relies on.