CodeSandbox SDK vs Unikraft Cloud
Both run each sandbox as a Firecracker microVM that sleeps when idle and wakes on the next request. CodeSandbox SDK gives you a dev VM with Docker inside that you size per sandbox, while Unikraft Cloud turns your Dockerfile into a tiny VM that boots in milliseconds and shares a flat plan pool.
The companies and products
CodeSandbox SDK
CodeSandbox SDK is an API from CodeSandbox, now a Together AI company, that starts sandboxed development VMs on the same infrastructure as the CodeSandbox editor.
Each sandbox is a Firecracker microVM built from a template or any Dockerfile. When it goes idle it hibernates with a memory snapshot, and it resumes or forks from that snapshot in seconds. You drive it from a TypeScript SDK through terminals, commands, files and HTTPS hosts. Together's docs now call it the legacy offering and point new users to its successor, the together-sandbox SDK.
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. “46th cheapest of 345” means 45 of the other 344 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 | CodeSandbox SDK: 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 CodeSandbox SDK runs Docker inside each VM and Unikraft documents no container runtime inside, while boat adds SSH, systemd and /dev/kvm on top of Docker. | 178th of 367, with limits $1,939 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 | 215th of 366, with limits $2,478 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 that sleep between calls suit both, but self-serve Unikraft caps you at 24 running instances, while CodeSandbox SDK's Scale plan allows 250. | 46th cheapest of 345 $642 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 CodeSandbox SDK caps Scale at 250 VMs at once and Unikraft Pro at 24 running instances, so 300 active users need Enterprise on either; boat fits on its paid plans. | 140th of 361, with limits $1,707 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 Both can fork from a memory snapshot, so many rollouts can branch from one warm state; boat forks a running sandbox with its disk. | 348th of 360, with limits $3,861 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 | 64th cheapest of 364 $1,335 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 jobs that build Docker images fit CodeSandbox SDK, Unikraft has no documented Docker inside, and only boat gives /dev/kvm for emulators on every plan. | 92nd cheapest of 377 $860 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 Neither has SSH, so you work through each SDK or CLI; boat gives a full box you SSH into, kept all month. | 310th of 368, with limits $240 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 Neither CodeSandbox SDK nor Unikraft has a desktop built in; boat streams one at 60fps with Chromium and computer-use tools. | 206th of 369, with limits $691 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 On both you build your own headless browser into an image; boat ships Chromium on a desktop in every sandbox. | 251st of 367, with limits $443 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 | 281st of 346, with limits $508 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 | 193rd of 338, with limits $7,390 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 | 240th of 360, with limits $326 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 | CodeSandbox SDK | Unikraft Cloud | boat |
|---|---|---|---|
| Isolation | Firecracker microVM with its own kernel | Minimal Linux microVM on a customized Firecracker VMM | Full VM with its own kernel on dedicated AMD Ryzen 9 9950X hosts |
| Machine size | 2 to 16 cores per sandbox, up to 32 GB on Scale; 64 cores / 128 GB on Enterprise | 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 |
| Docker inside | Docker and root; built from any Dockerfile | Runs as root; the Dockerfile becomes the VM image, with no container runtime inside documented | Docker, systemd and root, like any Ubuntu machine |
| Nested virtualization | Not documented | Yes, with a per-instance flag, Enterprise only | Yes, /dev/kvm for Android emulators and VMs on every plan |
| Shell access | Terminals, commands and files through the SDK; no SSH | Commands and files through the sandbox plugin and CLI; no SSH yet | SSH, plus exec and files over the API |
| Sleep and wake | Hibernates with a memory snapshot after an idle timeout; an HTTP request wakes it | Standby after a 1 second idle cooldown by default; traffic wakes it in milliseconds | Disk saved every minute and on stop; a stopped sandbox is started again by API |
| Fork | Fork a hibernated sandbox from its snapshot, or a running one sharing its memory | Checkpoint a running microVM's memory and volumes, then start new instances from it | Fork a running sandbox with its disk |
| Running at once (self-serve) | 250 VMs on Scale | 24 running instances on Pro, sharing 24 vCPU / 32 GiB | 100 to 2,000 sandboxes on paid plans |
| Inbound access | HTTPS host per port, public by default, signed tokens for private hosts; no raw TCP | HTTP on 80, HTTPS on 443 and TLS-wrapped TCP on other ports through its load balancer | HTTPS URLs for up to 50 ports, token-protected by default; raw TCP; dedicated IPv4 or IPv6 |
| Desktop and browser | No desktop; a headless Chromium template | None built in; run your own headless browser from a Dockerfile | Linux desktop streamed at 60fps, Chromium and computer-use tools |
| Coding agents | Run your own agent through the command API | None preinstalled; you bring the agent in your own image | Claude Code, Codex and others preinstalled, with a prompt, steer and events API |
| Keeping API keys out of the sandbox | Secrets passed in as environment variables | Network shield can inject secrets into traffic, Enterprise only, limited access | Credentials proxy for model providers and any HTTPS API, on every plan |
| Regions | A country hint steers scheduling, but placement is not guaranteed | Dallas, Frankfurt, San Francisco, Singapore and Washington DC; more on request | EU only (Germany, Finland, France) |
| Self-hosting | Not offered | Dedicated hosts, on-prem and your own cloud on Enterprise | Not offered |
Every feature Battleships tracks (43)
| Feature | CodeSandbox SDK | 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 | Not published | 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 | Yes | Yes | Yes |
| Live fork (no pause) | Yes | Yes | Yes |
| Memory fork | Yes | 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 | No | Yes | No |
| Secret proxy | No | Yes | Yes |
| Secret proxy for any API | No | Yes | Yes |
| Preinstalled agents | No | No | Yes |
| Agent harness API | No | No | Yes |
| MCP server | No | 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 | No | Yes | No |
| EU data residency | No | Yes | Yes |
| Zero data retention | Not published | Not published | Yes |
Performance
There is no comparable CPU measurement for CodeSandbox SDK or Unikraft Cloud: neither was in the StarSling hpc-sandbox-benchmarks run. boat did 26.69 runs per second on its Node.js loop at 4 vCPU / 8 GB, on dedicated AMD Ryzen 9 9950X hosts. Unikraft states cold starts under 10 ms, which is its own figure for 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. CodeSandbox SDK 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 | CodeSandbox SDK, 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 | $193 · Scale | $39 · Hobby | $20 · $20/mo |
| One agent that never stops 4 vCPU / 8 GB, 50 GB disk, running 24/7 all month | $341 · Scale | $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 | $2,500 · Scale | 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 | $815 · Scale · 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 | $1,632 · Scale · with limits | Can't run it | $2,000 · $2000/mo · with limits |
CodeSandbox SDK: You buy VM credits and each size burns a fixed number per hour, billed per started minute while the VM runs, including idle time before it hibernates. Scale adds a monthly platform fee that is not usage credit, and a hibernated VM costs nothing.
Unikraft Cloud: A flat monthly fee buys a pool of running capacity: free for 2 vCPU / 4 GiB, $39 for 8 vCPU / 8 GiB, $199 for 24 vCPU / 32 GiB, and sleeping instances are not counted. There is 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 pools are shared by every running instance, so one 4 vCPU / 8 GB agent fills the Team pool, and the 50-agent, user-sandbox and burst scenarios fit no self-serve plan. CodeSandbox SDK fits 50 agents at $2,500 a month but caps Scale at 250 VMs, so 300 user sandboxes or 1,000 jobs at once need Enterprise; its 20 GB disk and egress have no published price beyond that. boat fits every scenario except the burst, where even the $2,000 plan queues starts.
| Scenario | CodeSandbox SDK | Unikraft Cloud | boat |
|---|---|---|---|
| One coding agent, workdays |
|
| None that bite |
| One agent that never stops |
|
| 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 CodeSandbox SDK when
you need sandboxes with Docker inside that hibernate with their memory and wake on the next HTTP request, in the hundreds at once, and you are fine building on what Together now calls its legacy SDK.
- A real dev VM with Docker. Good when each sandbox needs Docker inside, built from any Dockerfile, with its own cores and memory up to 16 cores and 32 GB.
- Hundreds of sandboxes self-serve. The Scale plan runs 250 VMs at once, far more than the 24 running instances of Unikraft's largest self-serve plan.
- Memory forks of a running sandbox. Useful for branching many runs from one warm state: fork a running sandbox while it shares memory with its parent.
Use Unikraft Cloud when
you run many small services or headless browsers that sleep most of the time and must wake in milliseconds, need US or Asia regions, or want GPUs, on-prem or your own cloud under an Enterprise contract.
- Millisecond starts and scale-to-zero. Best for many small services that sleep most of the time and must answer the next request in milliseconds.
- Regions in the US and Asia. Pick Dallas, San Francisco, Washington DC, Singapore or Frankfurt, while CodeSandbox SDK only takes a best-effort country hint.
- GPUs, arm64 and your own hardware. Enterprise customers can get NVIDIA GPUs, arm64 hosts, dedicated hosts, on-prem or their own cloud.
Where boat fits
CodeSandbox SDK and Unikraft Cloud are both built around sandboxes that sleep fast and wake on the next request. If your agents instead work for hours, installing tools, running Docker and emulators, opening a browser and serving things to other people, boat gives each one a full machine with the agent and its keys already set up.
A whole machine with SSH and /dev/kvm
Neither has SSH, Unikraft documents no Docker inside, and CodeSandbox SDK does not document nested virtualization. On Unikraft, /dev/kvm needs an Enterprise contract. boat has SSH, systemd, Docker and /dev/kvm on every plan.
Agents, desktop and keys built in
On both you bring your own agent and browser, and neither has a desktop. Keys go in as environment variables on CodeSandbox SDK, and Unikraft's secret injection is Enterprise only. boat preinstalls agents you drive from outside, a 60fps desktop and a credentials proxy.
Fleets of full-size sandboxes
Fifty agents at 4 vCPU / 8 GB exceed every self-serve Unikraft pool, and CodeSandbox SDK stops at 250 VMs on Scale. boat runs up to 2,000 sandboxes at once on paid plans, with no session cap.
Use boat when your agents need a real machine to work in: SSH, Docker, emulators, a desktop and a browser, coding agents you drive from outside, and fleets of full-size sandboxes without a sales call. Compare it one to one: boat vs CodeSandbox SDK and boat vs Unikraft Cloud.
Questions people ask
Is CodeSandbox SDK cheaper than Unikraft Cloud?
For one agent, no: a 4 vCPU / 8 GB agent that never stops is $341 a month on CodeSandbox SDK and $39 a month on Unikraft's Team pool, and boat comes to $26 a month. For 50 agents, CodeSandbox SDK fits at $2,500 a month while no self-serve Unikraft plan is big enough, and boat comes to $317 a month.
Which is faster?
Unikraft starts faster: its microVMs cold boot in milliseconds by its own figure, while CodeSandbox SDK resumes hibernated VMs in seconds. Neither has a comparable CPU benchmark; boat measured 26.69 runs per second at 4 vCPU / 8 GB.
Can CodeSandbox SDK or Unikraft Cloud run Docker?
CodeSandbox SDK runs Docker with root inside each VM. Unikraft uses your Dockerfile to build the VM itself and does not document a container runtime inside a running instance. boat sandboxes have Docker, systemd and /dev/kvm ready to use.
Can I SSH into either one?
No. CodeSandbox SDK connects through its SDK, Node and browser clients, and Unikraft has announced SSH as coming soon, with commands and files going through its sandbox plugin and CLI today. Every boat sandbox has SSH as well as an exec and files API.
How many sandboxes can run at once?
CodeSandbox SDK's Scale plan allows 250 VMs at once, and Unikraft's Pro plan allows 24 running instances sharing 24 vCPU and 32 GiB, with up to 5,000 more asleep. Beyond that both need Enterprise, while boat's paid plans run 100 to 2,000 sandboxes at once.
Is boat SOC 2 compliant?
SOC 2 is in progress. We're open about where we stand: live status at status.ascii.dev and our data retention policy at docs.boat.dev/data-retention.
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