E2B vs Fly Sprites Sprites 13% cheaper if agents wait, E2B 20% if busy

Which is better, E2B or Fly Sprites?

It depends on how often your agents go quiet. Runtime has the lowest bill here whether they wait or compute: $0.64 for the waiting job, against $2.40 on Sprites and $2.76 on E2B. It measures CPU like Sprites, at a lower rate, and lets you size memory yourself. Pick E2B for self-hosting or for pauses with no expiry. Pick Sprites for cold storage at $0.02 per GB-month, or for the Go and Elixir SDKs.

At a glance

Are Sprites cheaper than E2B?

Only when the sandbox uses little memory. Sprites bill CPU the way Runtime does, by what the code uses, so a waiting agent pays almost nothing for CPU: $0.21 in the job below, against $1.68 on E2B. Memory is where Sprites cost more. It is $0.021875 per GB-hour of memory in use, against E2B's $0.0162 per allocated GiB-hour. So a Sprite using all 4 GB pays $2.19 for memory and $2.40 in total.

A Sprite is billed for the memory it actually uses. The same job using 1 GB costs $0.76 on Sprites, well under E2B's $2.76. A busy job moves the other way: Sprites' CPU charge grows with use, while E2B's does not.

Runtime's measured CPU costs $0.025 per vCPU-hour, and its memory $0.0075 per GiB-hour. It is cheaper than both, whichever way the job leans.

Cost for the same job

1,000 runs of a 2 vCPU, 4 GiB sandbox. Each run lasts 60 seconds and keeps the CPU busy for 20 CPU-seconds: an agent that mostly waits for a model. The Sprite is assumed to use all 4 GB for the whole minute.

At 100,000 runs per month, that is $276.00 on E2B, $240.14 on Sprites and $63.89 on Runtime. With both CPUs busy for the whole minute, it is $1.33 on Runtime, against $2.76 on E2B and $3.47 on Sprites, so Runtime is cheaper however busy the sandbox is. The Sprite figure includes the 30 seconds or so that a Sprite stays awake and billed after its run. Plan fees, storage, network and free credits are left out.

What happens when the agent goes quiet?

This is where the two differ most. A Sprite pauses itself when nothing is happening. It keeps its disk always and its memory at first. When it goes cold, its memory is dropped at a time you do not choose. An E2B sandbox bills its full size until its timeout ends it, or until you pause or kill it. A session lasts at most 1 hour on Hobby and 24 hours on Pro. A paused E2B sandbox keeps files, memory and running processes with no expiry.

Runtime does both: a sandbox can pause itself after a set idle time, and a paused sandbox keeps its files, memory and processes while you have credit. The next request wakes it.

TypeScriptimport { Sandbox } from "withruntime";const sbx = await Sandbox.create({ idlePauseSeconds: 600 }); // ten idle minutesawait sbx.update({ idlePauseSeconds: 1800 }); // change it later; 0 turns it off

Pythonfrom withruntime import Sandboxdev = Sandbox.get_or_create("dev", idle_pause_seconds=900)dev.exec("git pull || true")

Which one to pick

• Pick E2B for fixed sizes billed by the second, paused sandboxes kept with no expiry, or a runtime you can self-host under Apache-2.0.
• Pick Sprites for sandboxes that manage their own sleep, a 100 GB disk, very cheap cold storage at $0.02 per GB-month, or SDKs in Go and Elixir.
• Pick Runtime for measured CPU at 35% below Sprites' rate and 50% below E2B's allocated rate, memory you size and plan against, and a pause that keeps memory for as long as you choose.

Switch from either one

From E2B, change one import:

TypeScriptimport { Sandbox } from "withruntime/e2b"; // was: from "e2b"

Pythonfrom withruntime.e2b import Sandbox  # was: from e2b import Sandbox

From Sprites, the calls map directly: client.createSprite(name) becomes Sandbox.create(), or Sandbox.getOrCreate(name) to find a named one again, and sprite.execFile(cmd, args) becomes exec([cmd, ...args]):

TypeScriptimport { Sandbox } from "withruntime";const box = await Sandbox.create();try {  await box.files.write("/workspace/invoice.py", "print(sum([125, 250, 375]))\n");  console.log((await box.exec(["python3", "/workspace/invoice.py"], { check: true })).stdout);} finally {  await box.stop();}

Or give your coding agent the one instruction in migration: it switches the project on a branch, tests it on the free usage and reports the monthly saving. npx withruntime compare --from fly (or --from e2b) prices what you ran at the old provider's rates. Credit you add within 30 days of signing up is matched, up to $1,000 in total. The full comparisons are Runtime vs E2B and Runtime vs Fly.io.

Sources

Fly.io prices checked 25 October 2026.

E2B and Fly.io pricing pages rechecked 25 October 2026; the rest checked 25 October 2026.

• E2B pricing, E2B sandbox persistence
• Fly.io pricing, Sprites, Sprites documentation, Sprites lifecycle and persistence
• Runtime pricing and the JavaScript guide

Facts on this page were checked on 26 October 2026.