Sprites vs Unikraft Cloud
Both run each workload in its own Firecracker microVM that sleeps when idle. Sprites gives each agent a ready Ubuntu computer with a 100 GB disk and bills the CPU and memory it really uses, while Unikraft Cloud turns your Dockerfile into a tiny VM that wakes in milliseconds, sold as flat plans that cap how much can run at once.
The companies and products
Sprites
Sprites is Fly.io's product for agents: persistent Linux computers you create by API or CLI, which sleep when idle and wake on the next request.
Each Sprite is a Firecracker microVM with 8 vCPU, memory the platform manages, and a 100 GB ext4 disk that syncs to object storage. It runs one managed Ubuntu image with Claude Code, Codex, Gemini CLI and Cursor preinstalled, gets an HTTPS URL that wakes it, and bills only for the CPU and memory it actually uses while awake. It is built for coding agents, dev environments and user code that sit idle most of the time.
- Isolation
- Firecracker microVM per Sprite
- Regions
- Not selectable for Sprites
- Free start
- $30 trial credit per organization
Unikraft Cloud
Unikraft Cloud is a microVM cloud from Unikraft Inc. that runs any Dockerfile-based workload as a minimal Linux microVM with millisecond cold starts and scale-to-zero.
Your Dockerfile becomes the VM image at build time, and each instance runs on a heavily customized Firecracker VMM, so it boots in milliseconds and can go into standby when no traffic arrives. It is a general compute platform built for dense, bursty work such as HTTP services, headless browsers and agent fleets, sold as flat self-serve plans plus Enterprise dedicated hosts, on-prem and bring your own cloud. It is not a dev machine you log into: instances are reached through services, the CLI and a sandbox plugin for commands and files.
Which use cases each one fits
For each use case, Battleships prices every sandbox provider on the same workload and sorts them from the cheapest monthly bill up. “63rd cheapest of 377” means 62 of the other 376 providers run that workload, with every feature it needs, for less. “With limits” means the provider runs it but misses something, so it is listed after every full match. Open a use case for its whole ranking and what each provider misses.
| Use case and its workload | Sprites: price rank | Unikraft Cloud: price rank | boat: price rank |
|---|---|---|---|
| Software factory 100 at once · 4 vCPU / 8 GB · 2,200 sessions of 8 h a month Sprites gives an agent a ready Ubuntu machine with Docker and a 100 GB disk, while Unikraft builds your Dockerfile into the VM and documents no container runtime inside; boat adds systemd and /dev/kvm on top. | 66th of 367, with limits $546 a month | Can't run it | 3rd cheapest of 367 $634 a month |
| Always-on AI employees 50 machines 24/7 · 2 vCPU / 4 GB An always-on assistant drops its open connections on every Sprite pause, and on Unikraft it shares a Team pool of 8 GiB with every other running instance; boat just keeps the machine running. | 157th of 366, with limits $1,166 a month | Can't run it | 5th cheapest of 366 $657 a month |
| Code interpreter bursts 100 at once · 1 vCPU / 2 GB · 200,000 sessions of 1 min a month Short code runs suit both: Sprites bills only real CPU and memory while awake, and Unikraft wakes in milliseconds, though its self-serve plans stop at 24 running instances. | 93rd of 345, with limits $140 a month | Can't run it | 186th of 345, with limits $2,000 a month |
| Sandboxes for your users 300 at once · 2 vCPU / 4 GB · 30,000 sessions of 23 min a month Neither fits 300 user sandboxes at once as published: Sprites does not confirm that many running, and Unikraft Pro runs 24, so you need a plan or contract from sales. | 56th of 361, with limits $428 a month | Can't run it | Cheapest of 361 $209 a month |
| RL rollouts 1,000 at once · 2 vCPU / 4 GB · 1,000,000 sessions of 3 min a month | 105th of 360, with limits $6,540 a month | Can't run it | 34th of 360, with limits $2,000 a month |
| Agent evals 250 at once · 4 vCPU / 8 GB · 15,000 sessions of 20 min a month | 125th of 364, with limits $545 a month | Can't run it | 10th cheapest of 364 $200 a month |
| CI runners 40 at once · 8 vCPU / 16 GB · 6,000 sessions of 12 min a month CI that builds Android apps or VM images needs /dev/kvm: the Sprites docs do not mention it, Unikraft keeps it for Enterprise, and boat has it on every plan. | 63rd cheapest of 377 $476 a month | Can't run it | 4th cheapest of 377 $86 a month |
| 24/7 dev boxes 1 machine 24/7 · 4 vCPU / 8 GB For a 24/7 dev box, Sprites comes to $27 a month and Unikraft to $39, but neither offers direct SSH; boat comes to $26 with SSH and systemd. | 213th of 368, with limits $27 a month | 219th of 368, with limits $39 a month | 18th cheapest of 368 $26 a month |
| Computer-use agents 50 at once · 4 vCPU / 8 GB · 20,000 sessions of 15 min a month Both are headless, so a computer-use agent needs a display and browser you build yourself; boat streams a 60fps desktop with Chromium. | 85th of 369, with limits $136 a month | Can't run it | 6th cheapest of 369 $200 a month |
| Browser-use agents 50 at once · 2 vCPU / 4 GB · 30,000 sessions of 10 min a month Teams run their own headless Chrome on Unikraft at scale, and on Sprites you install one yourself; boat ships Chromium on a desktop you can watch. | 171st of 367, with limits $122 a month | Can't run it | 7th cheapest of 367 $200 a month |
| Scraping & bots (startup scale) 50 at once · 1 vCPU / 2 GB · 100,000 sessions of 3 min a month | 229th of 346, with limits $206 a month | Can't run it | 6th cheapest of 346 $90 a month |
| Mass scraping & bots (undetectable) 1,000 at once · 1 vCPU / 2 GB · 3,000,000 sessions of 2 min a month | 141st of 338, with limits $4,113 a month | Can't run it | 71st of 338, with limits $1,800 a month |
| Parallel red teaming 200 at once · 2 vCPU / 4 GB · 5,000 sessions of 30 min a month | 210th of 360, with limits $223 a month | Can't run it | 2nd cheapest of 360 $200 a month |
| GPU eval jobs 10 at once · 8 vCPU / 32 GB · 500 sessions of 30 min a month | Can't run it | Can't run it | Can't run it |
| macOS agents 5 at once · 4 vCPU / 8 GB · 1,000 sessions of 20 min a month | Can't run it | Can't run it | Can't run it |
Key features
| Feature | Sprites | Unikraft Cloud | boat |
|---|---|---|---|
| Isolation | Firecracker microVM with its own kernel | Minimal Linux microVM on a customized Firecracker VMM; full VMs on Enterprise | Full VM with its own kernel on dedicated AMD Ryzen 9 9950X hosts |
| Machine size | Fixed 8 vCPU and 100 GB disk; memory managed and scaled by the platform | Plan pool shared by all running instances: 2 vCPU / 4 GiB, 8 vCPU / 8 GiB or 24 vCPU / 32 GiB | 4 vCPU / 8 GB by default, up to 16 vCPU / 32 GB per sandbox on the $100 plan and above |
| Image | One managed Ubuntu image; you install on top of it | Your Dockerfile becomes the VM image | Full Ubuntu machine you install on; named snapshots to start new sandboxes from |
| Docker and systemd inside | Root and Docker (with rough edges users report); no systemd | Runs as root; no container runtime inside documented | Root, Docker and systemd, like any Ubuntu machine |
| Nested virtualization | No /dev/kvm in the docs | Yes, with a per-instance flag, Enterprise only | Yes, /dev/kvm for Android emulators and VMs on every plan |
| SSH | Only through the sprite proxy CLI, with an SSH server you install | Not yet; commands and files go through the sandbox plugin and CLI | Yes, into every sandbox |
| Idle and wake | Pauses about 30 seconds after activity stops; wakes on the next request in 100 to 500 ms with memory | Standby after a 1 second idle cooldown by default; wakes on traffic in milliseconds with memory restored | Runs until you stop it or its time to live ends; a stopped sandbox costs nothing and starts again by API |
| Fork and checkpoints | Filesystem checkpoints that restore in place; no fork | Checkpoint memory and volumes of a running microVM, then start new instances from it | Fork a running sandbox with its disk; disk saved every minute and on stop |
| Inbound access | One HTTPS URL to one HTTP port; other ports only through the sprite proxy CLI | Services on its load balancer: HTTP, HTTPS and TLS-wrapped TCP; no public IP per instance | HTTPS URLs for up to 50 ports, token-protected; raw TCP; dedicated IPv4 or IPv6 |
| Outbound rules | DNS-based domain allowlist set from outside; private IPs always blocked | Network shield filters traffic, Enterprise only, limited access | Open internet, no provider-side allowlist |
| Keeping API keys out of the sandbox | Connectors gateway holds the token for any HTTP API, with path allow and block lists | Network shield can inject secrets, Enterprise only, limited access | Credentials proxy for model providers and any HTTPS API on every plan; switch to another account when credits run out |
| Coding agents | Claude Code, Codex, Gemini CLI and Cursor preinstalled, run through exec or a console | None preinstalled; you bring the agent in your own image | Seven agents preinstalled, with a prompt, steer and events API to drive them from outside |
| Desktop and browser | Headless; no desktop or browser product | None built in; you can run your own headless browser | 60fps desktop and Chromium, computer use and browser control |
| Regions | Region not selectable | Dallas, Frankfurt, San Francisco, Singapore and Washington DC, more on request | EU only (Germany, Finland, France), with EU data residency |
Every feature Battleships tracks (43)
| Feature | Sprites | Unikraft Cloud | boat |
|---|---|---|---|
| Full VM (own kernel) | Yes | Yes | Yes |
| Docker inside | Yes | No | Yes |
| Nested virtualization | No | Yes | Yes |
| Root | Yes | Yes | Yes |
| Systemd | No | Not published | Yes |
| Desktop GUI | No | No | Yes |
| Browser | No | No | Yes |
| Computer-use API | No | No | Yes |
| SSH | No | No | Yes |
| Persistent disk | Yes | Yes | Yes |
| Pause/resume | Yes | Yes | Yes |
| Automatic snapshots | Yes | Yes | Yes |
| Fork/clone | No | Yes | Yes |
| Live fork (no pause) | No | Yes | Yes |
| Memory fork | No | Yes | No |
| Custom image (Docker or snapshot) | Yes | Yes | Yes |
| ≥24 h sessions | Yes | Yes | Yes |
| Idle auto-stop | Yes | Yes | No |
| Wake on request | Yes | Yes | No |
| HTTPS preview URLs | Yes | Yes | Yes |
| Raw TCP inbound | No | Not published | Yes |
| Public IPv4 | No | No | No |
| Egress allowlist | Yes | Yes | No |
| Secret proxy | Yes | Yes | Yes |
| Secret proxy for any API | Yes | Yes | Yes |
| Preinstalled agents | Yes | No | Yes |
| Agent harness API | No | No | Yes |
| MCP server | Yes | No | No |
| GPU | No | Yes | No |
| Windows | No | No | No |
| Arm64 | No | Yes | No |
| Self-hosting | No | Yes | No |
| BYOC | No | Yes | No |
| Open source | No | No | No |
| Scoped API keys | Not published | Not published | Yes |
| Spend limits | Not published | Not published | Yes |
| Usage per sandbox (API) | No | No | Yes |
| Audit logs | Not published | Yes | No |
| SSO | Yes | No | No |
| SOC 2 | Yes | Yes | No |
| HIPAA | Yes | Yes | No |
| EU data residency | No | Yes | Yes |
| Zero data retention | Not published | Not published | Yes |
Performance
There is no comparable measurement for Sprites or Unikraft Cloud: neither is in the hpc-sandbox-benchmarks results we use. boat did 26.69 runs per second on the Node.js build-and-test test at 4 vCPU / 8 GB, on dedicated AMD Ryzen 9 9950X hosts. Unikraft states cold starts under 10 ms and Sprites states wakes of 100 to 500 ms, but those measure start time, not CPU speed.
Node.js build-and-test loop at 4 vCPU / 8 GB, higher is better. Measured with the open hpc-sandbox-benchmarks suite. Sprites and Unikraft Cloud have no published run in this suite yet, so there is no like-for-like number to compare.
Pricing in five scenarios
Each bill is priced from the providers' public price lists by the open Battleships engine, with the cheapest plan that runs the scenario.
| Scenario | Sprites, a month | Unikraft Cloud, a month | boat, a month |
|---|---|---|---|
| One coding agent, workdays 4 vCPU / 8 GB, 50 GB disk, 8 hours a day, 22 days a month, files kept between days | $23 · Pay-as-you-go | $39 · Hobby | $20 · $20/mo |
| One agent that never stops 4 vCPU / 8 GB, 50 GB disk, running 24/7 all month | $92 · Pay-as-you-go | $39 · Hobby | $26 · $20/mo |
| 50 agents in parallel 50 machines of 4 vCPU / 8 GB at once, 8-hour sessions, 1,100 sessions a month, Docker inside | $1,120 · Pay-as-you-go | Can't run it | $317 · $20/mo × 3 seats |
| Sandboxes for your users 2 vCPU / 4 GB, 30,000 sessions of 10 minutes a month, up to 300 at once | $314 · Pay-as-you-go · with limits | Can't run it | $200 · $100/mo × 2 seats |
| 1,000 short jobs at once 2 vCPU / 4 GB, 1,000 at once, 3 minutes each, 200,000 jobs a month | $1,134 · Pay-as-you-go · with limits | Can't run it | $2,000 · $2000/mo · with limits |
Sprites: Sprites bills CPU time at $0.0385 per CPU-hour and actual memory at $0.021875 per GB-hour, only while the Sprite is awake, plus storage on the bytes you write. Optional plans add fixed CPU-hour, memory-hour and storage allowances, and usage above them bills at the normal rates.
Unikraft Cloud: Unikraft charges a flat monthly fee for a pool of running capacity: free for 2 vCPU / 4 GiB, $39 for 8 vCPU / 8 GiB and $199 for 24 vCPU / 32 GiB, with sleeping instances not counted. It publishes no per-hour rate, so anything bigger is an Enterprise quote.
Unikraft Cloud: Plans start at $20 a month, and the whole fee is usage credit. You pay per second while a sandbox runs, and a stopped sandbox costs nothing and keeps its disk.
Limits in those scenarios
Unikraft's limits are pools that every running instance shares: one 4 vCPU / 8 GB agent fills the Team plan, so 50 agents, 300 user sandboxes and 1,000 short jobs fit no self-serve plan. Sprites does not publish how many machines can run at once on pay as you go, so 300 user sandboxes and 1,000 jobs at once are not confirmed, and an always-on agent needs a task hold renewed every hour. boat has no session cap on paid plans, but at 1,000 short jobs at once even its $2,000 plan queues starts above 90 a minute.
| Scenario | Sprites | Unikraft Cloud | boat |
|---|---|---|---|
| One coding agent, workdays | None that bite |
| None that bite |
| One agent that never stops | None that bite |
| None that bite |
| 50 agents in parallel |
|
| None that bite |
| Sandboxes for your users |
|
| None that bite |
| 1,000 short jobs at once |
|
|
|
Which one should you use?
Use Sprites when
you want a ready Ubuntu computer for a coding agent that sits idle much of the day, billed only for what it uses, with a domain allowlist on self-serve plans.
- A ready computer for coding agents. Each Sprite is an Ubuntu machine with a 100 GB disk and Claude Code, Codex, Gemini CLI and Cursor already installed.
- Billed by real use. Sprites bills the CPU time and memory a machine actually uses while awake, so a mostly idle agent costs little.
- Egress allowlist and connectors, self-serve. Teams that must limit where agents connect get a domain allowlist and API path rules without an Enterprise contract.
Use Unikraft Cloud when
you run many small services or headless browsers from a Dockerfile that must wake in milliseconds, need US or Asia regions, or want GPUs or on-prem under Enterprise.
- Millisecond starts from your Dockerfile. Best for many small services built from a Dockerfile that sleep most of the time and must answer in milliseconds.
- Checkpoints you can start new instances from. Unikraft can checkpoint a running microVM's memory and start new instances from it, with warm caches.
- Regions, GPUs and your own hardware. Unikraft runs in the US, Frankfurt and Singapore, and Enterprise adds GPUs, arm64, on-prem or your own cloud.
Where boat fits
Sprites and Unikraft Cloud are both built around machines that sleep most of the time. If your agents work for hours, run Docker and emulators, need a screen, or run as fleets of 50 or more, look at boat: each sandbox is a full VM that keeps running until you stop it.
A full machine with systemd and /dev/kvm
Sprites has no systemd and no /dev/kvm in its docs, and Unikraft documents no container runtime inside and keeps nested virtualization for Enterprise. On either, Android emulators and stacks built on systemd units need rework or a sales contract.
Agents that keep working, and fleets that fit
A Sprite drops open connections on every pause unless a task hold, renewed each hour, keeps it awake. Unikraft's biggest self-serve pool runs 24 instances, so 50 agents at 4 vCPU / 8 GB need an Enterprise quote. boat runs them with no session cap.
A desktop, SSH and agents driven from outside
Both are headless and neither offers direct SSH, so you build a display, browser and stream yourself and write the code that starts and watches each agent. boat has a 60fps desktop, SSH, 50 HTTPS ports and an API to drive agents inside.
Use boat when your agents need a full machine for hours: Docker, systemd, emulators, SSH, a desktop and browser, forks, and fleets of full-size sandboxes without a sales call. Compare it one to one: boat vs Sprites and boat vs Unikraft Cloud.
Questions people ask
Is Sprites cheaper than Unikraft Cloud?
For one coding agent on workdays, yes: $23 a month on Sprites against the $39 Team pool on Unikraft. For one agent that never stops, Unikraft's flat $39 beats $92 on Sprites. For 50 agents in parallel, Sprites comes to $1,120 and no self-serve Unikraft plan fits; boat comes to $20, $26 and $317 for the same three.
Which one is faster?
Unikraft starts faster: it states cold starts under 10 ms, while a Sprite wakes in 100 to 500 ms. Neither has a CPU speed measurement we can compare. boat did 26.69 runs per second on our Node.js test at 4 vCPU / 8 GB.
Can Sprites or Unikraft Cloud run Docker?
Users run Docker inside Sprites, though some containers hit capability limits, and Sprites does not run systemd. Unikraft uses your Dockerfile to build the VM itself and does not document a container runtime inside. A boat sandbox runs Docker, systemd and /dev/kvm.
Can I SSH into Sprites or Unikraft Cloud?
Not directly. On Sprites you install an SSH server and tunnel it through the sprite proxy CLI, and Unikraft lists SSH as coming soon, with commands going through its sandbox plugin and CLI today. Every boat sandbox has SSH, raw TCP and a dedicated IP.
Which one keeps an agent running all day?
Neither by default. A Sprite pauses about 30 seconds after activity stops unless a task hold keeps it awake for up to an hour at a time, and Unikraft puts idle instances into standby. A boat sandbox keeps running until you stop it.
Where do they run?
Sprites does not let you choose a region. Unikraft runs in Dallas, Frankfurt, San Francisco, Singapore and Washington DC, with more on request. boat runs only in the EU, in Germany, Finland and France.
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