Runtime

CodeSandbox SDK alternatives: agent sandboxes ranked by cost

Runtime is the cheapest CodeSandbox SDK alternative, 74% less per job, billed by the second with no plan for concurrency.

Runtime runs the CodeSandbox SDK's workload for 74% less, in the same kind of Firecracker microVM. 1,000 one-minute runs of a 2 vCPU, 4 GiB sandbox cost $0.64 on Runtime and $2.48 on a CodeSandbox Nano VM, $184 a month saved at 100,000 runs, with no plan needed for more than 10 sandboxes at once. Rates checked 23 September 2026.

Estimated compute cost

74% less than CodeSandbox55% less than Fly Machines62% less than Morph

2 vCPUs · 4 GiB · 60 s a run · 20 CPU-seconds busy

1,000

Compute only, at list rates checked 23 September 2026 (Together Code Sandbox, Fly.io pricing, Morph Cloud pricing). Plan fees, network, taxes and free credits are left out. The worked example below shows the arithmetic.

Why do teams look beyond the CodeSandbox SDK?

The CodeSandbox SDK, now documented by Together (CodeSandbox is a Together company), sells VMs in fixed sizes paid for in credits. The reasons to move are in how that bills:

  • A size, not usage. A Nano VM is 10 credits an hour at $0.01486 a credit for as long as it runs, whether the CPU is busy or the agent is waiting on a model.
  • Rounded up to the minute. A VM that runs for 3 minutes and 25 seconds is billed as 4. A 40-second tool call is billed as a minute.
  • Fixed shapes. You pick the size that covers your largest need. On Runtime you set vCPUs and memory for each sandbox and pay for no more.
  • Concurrency costs a plan. The free Build plan runs 10 VMs at once; more needs the Scale plan, $170 a month for 250. A paid Runtime account starts at 100 sandboxes at once with no plan fee, raised on request.

Which alternatives are cheapest?

Each provider gets the same job at its list rates: 1,000 runs of 60 seconds on a 2 vCPU, 4 GiB sandbox, busy for 20 CPU-seconds apiece. For CodeSandbox that means a Nano VM, 2 cores and 4 GB, which comes seventh. Pricing lays out every row's arithmetic, with no plan fees, storage, network, free credits or negotiated prices in it.

# Provider Isolation CPU billed on 1,000 runs
1 Runtime Firecracker microVM, own kernel Measured CPU, with a small floor $0.64
2 Northflank microVMs for CPU work, gVisor for GPU work Allocated vCPUs $1.11
3 Cloudflare Sandbox (2 vCPU, 6 GiB, 12 GB disk) A container in its own VM Active CPU $1.35
4 Fly Machines, performance-2x with 4 GB Firecracker microVM The machine's size while started $1.44
5 Morph, 2 MCUs Full virtual machines The machine's size in MCUs $1.67
6 Vercel Sandbox, iad1 (4 GB) Firecracker microVM, own kernel Active CPU $2.12
7 CodeSandbox SDK, a Nano VM (the one you are replacing) Firecracker microVM The VM's size, by the minute rounded up $2.48
8 E2B Firecracker microVM, own kernel Allocated vCPUs $2.76
9 Daytona Containers by default; VM class separate Allocated vCPUs $2.76
10 Blaxel (4 GB) Lightweight virtual machines Included with memory, active time $2.76
11 Fly Sprites (4 GB in use) Firecracker microVM Measured CPU $3.31
12 Modal Sandboxes (1 physical core) gVisor, a user-space kernel Requested or used, whichever is higher $3.97
13 Runloop, a MEDIUM devbox microVM, with a container inside Allocated CPUs while running $5.33

Cost for the same job

The working for Runtime, CodeSandbox and the two other providers that bill a machine by its size:

TextRuntime      CPU    1,000 × 20 s / 3,600 × $0.025          = $0.14             Memory 1,000 × 60 s / 3,600 × 4 × $0.0075     = $0.50             Total                                            $0.64CodeSandbox  Size   1,000 × 60 s / 3,600 × $0.1486         = $2.48Machines     Size   1,000 × 60 s / 3,600 × $0.0861         = $1.44Morph        Size   1,000 × 60 s / 3,600 × 2 MCU × $0.05   = $1.67

A VM priced by size costs the same whatever the CPU does, so with both CPUs busy for the whole minute the figures are $1.33 on Runtime, $2.48 on CodeSandbox, $1.44 on Machines and $1.67 on Morph, and the waiting agent is where the saving is largest. At 100,000 runs a month, waiting, it is $63.89 on Runtime and $247.67 on CodeSandbox.

Each run here is a whole minute, so CodeSandbox's rounding adds nothing. Make it 40 seconds and CodeSandbox still bills $2.48, while Runtime bills the 40 seconds.

What each alternative means for a CodeSandbox user

1. Runtime: per-second billing, sized to the job

A Firecracker microVM per sandbox, like a CodeSandbox VM, billed each second: $0.025 per vCPU-hour of measured CPU, with a twentieth of a vCPU as the floor, and $0.0075 per reserved GiB-hour. You pick vCPUs and memory separately. Snapshots and forks carry files, memory and running processes, and a named sandbox that pauses when idle works as a per-user workspace.

2. Northflank: allocation at low rates

$0.01667 per vCPU-hour and $0.00833 per GB-hour, with each resource chosen on its own. A sandbox is a service with a deployment plan, deployable into your AWS, GCP or Azure account.

3. Cloudflare Sandbox: fine-grained active CPU

Active CPU at $0.072 per vCPU-hour in 10 ms steps, far finer than a rounded-up minute, but with at least 3 GiB per vCPU. It is driven from a Worker on the Workers Paid plan, from $5 a month.

4. Fly Machines: the closest billing model

Also a fixed size, but counted by the second instead of the minute. performance-2x with 4 GB costs $0.0861 an hour in iad, across 18 regions.

5. Morph: branching, plus shareable devboxes

$0.05 per MCU-hour, one MCU covering 1 vCPU, 4 GB of memory or 16 GB of disk. Infinibranch forks a running machine into hundreds of replicas, and Morph Devboxes are shareable workspaces that hold memory while idle.

6. Vercel Sandbox: thousands at once

$0.128 per active CPU-hour and $0.0212 per GB-hour in iad1, on Firecracker, with room for 10,000 sandboxes at once on Pro against CodeSandbox's 250 on Scale.

7. E2B: allocation billing on microVMs

$0.0504 per vCPU-hour and $0.0162 per GiB-hour, by the second. Sessions reach 24 hours on Pro at $150 a month, 1 hour on Hobby; the runtime is Apache-2.0.

8. Daytona: GPUs and Windows machines

E2B's rates, containers by default with VMs as their own class, GPU sandboxes and Windows machines.

9. Blaxel: memory-only pricing with standby

$0.0000115 per GB-second while active, cores included. Standby starts when connections close, and a sandbox is back in about 25 ms.

10. Fly Sprites: a big disk that persists

$0.07 per measured CPU-hour and $0.04375 per GB-hour of memory in use, with a 100 GB disk that stays with the Sprite.

11. Modal Sandboxes: GPU functions nearby

gVisor at $0.1419 per physical core-hour, charged on request or use, whichever is larger.

12. Runloop: devboxes for benchmarks

$0.108 per CPU-hour and $0.0252 per GB-hour, plus disk, with SWE-Bench and other public benchmarks.

How to switch from the CodeSandbox SDK

A one-off run is a create, an exec and a stop:

TypeScriptimport { Sandbox } from "withruntime";const box = await Sandbox.create({ funding: "trial" });try {  console.log((await box.exec("python3 -c 'print(6 * 7)'", { check: true })).stdout);} finally {  await box.stop();}

A CodeSandbox VM kept per user or per project becomes a named Runtime sandbox. get_or_create returns the sandbox with that name, woken if it is paused, or creates it:

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

To have it done for you, give a coding agent the single instruction in migration; it replaces the calls on a branch, tries them on the free trial and states the monthly saving. After some runs, npx withruntime compare --from codesandbox prices your own sandboxes at the CodeSandbox SDK's published rates. On workspaces, see per-user dev environments and preview agent-built apps.

Sources

Rival rates were checked 23 September 2026; the Together Code Sandbox page was read again on 25 September 2026.

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