Cinch vs E2B: which sandbox for running untrusted, AI-generated code?

TL;DR

E2B is the category leader with a bigger free tier and more features. Cinch is the indie option: flat $0.10 per sandbox-hour, billed by the millisecond, no monthly floor. If you're running production workloads at serious scale with a team budget, E2B is a safe pick. If you're a solo dev or small team who doesn't want a $150/month subscription just to ship, that's exactly why Cinch exists.

Pricing, honestly

E2B (as of this writing):

• Free tier: a one-time $100 credit
• Production use effectively means the Pro plan — a $150/month floor, whether you use it or not
• Rates are per-resource: roughly $0.05 per vCPU-hour plus ~$0.016 per GiB-hour, billed per second

Cinch:

• Free tier: $1 on signup (about 10 sandbox-hours) — and up to $1,000 through the Builders program
• No plan. No floor. Prepaid credits, spend them whenever
• One flat rate: $0.10 per sandbox-hour, billed per millisecond

The rate math matters less than the floor math. A side project running 50 sandbox-hours a month costs $5 on Cinch. On E2B, needing production-grade limits means the Pro plan — $150 that month whether you burned the hours or not.

There's also a simplicity difference: per-vCPU-plus-per-GiB pricing is hard to estimate in your head. One flat number isn't.

When E2B is the right call

Genuinely — sometimes it is. If you're at a funded company where $150/month is a rounding error, the longer track record is worth it.

When Cinch is

You're building AI agents, code tools, graders, or anything that executes code it didn't write, and you want:

• One REST call — send code, get stdout/stderr/exit code back
• gVisor isolation — no network, read-only base filesystem, strict limits
• Sub-300ms typical execution
• Disposable sandboxes — fresh box per run, destroyed after
• Python and JavaScript SDKs, plus an MCP server for agent frameworks

The part no pricing page says

Cinch is built by one person — me. I'm 17. When you email, I answer, and early users' feedback literally decides the roadmap. Depending on your risk tolerance that's either the feature or the risk; for indie devs it's usually the feature.

Try it at cinch.codes — $1 free, no card required. Building something real? The Builders program is at cinch.codes/builders.