# GitHub Codespaces vs an agent sandbox: which one should run AI agents?

Codespaces gives a person a cloud dev environment per repository; an agent sandbox gives code a machine it creates and drives by API.

**Runtime charges $0.03125 to $0.08 an hour for 2 vCPUs and 4 GiB, against
$0.18 an hour for a 2-core codespace**, because it bills the CPU the code uses
rather than the machine's cores. A new sandbox ran its first Python command
351 ms after the create request at the median, measured on 24 September 2026
([speed](/docs/speed)), and every command is one API call. GitHub rates
checked 25 September 2026.

## What Codespaces is built for

GitHub describes a codespace as a development environment for a repository.
When you create one, "a virtual machine (VM) is created", "dedicated and
private to you", and "GitHub Codespaces uses a Docker container as the
development environment". You connect to it with an editor, or from a
terminal with `gh codespace ssh`.

- **Files.** `/workspaces` is "a persistent directory that is mounted into the
  container". Changes elsewhere survive a stop and start but "are not preserved
  when you rebuild the container".
- **Idle timeout.** "By default this period is 30 minutes", and it can be set
  from 5 to 240 minutes.
- **Retention.** Stopped codespaces are deleted after 30 days inactive by
  default, and 30 days is the maximum.
- **API.** The REST API creates a codespace in a repository and starts and
  stops it (`POST /repos/{owner}/{repo}/codespaces`,
  `POST /user/codespaces/{codespace_name}/start`). Commands inside run over a
  connection such as `gh codespace ssh`.

## Side by side

|               | GitHub Codespaces                            | Runtime sandbox                                                         |
| ------------- | -------------------------------------------- | ----------------------------------------------------------------------- |
| Made for      | A developer working on one repository        | Code that an agent or a program starts, runs and throws away            |
| Machine       | A dedicated VM with the dev container inside | A Firecracker microVM with its own Linux kernel                         |
| Run a command | Connect, then run it                         | `sbx.exec(...)`, with exit code, output and a timeout in the result     |
| Sizes         | 2 to 32 cores                                | vCPUs, memory and disk set per sandbox; 2 vCPU and 4 GiB by default     |
| Idle          | Stops after 5 to 240 minutes; files kept     | Pauses with files, memory and running processes, kept 1 to 365 days     |
| Copies        | New codespaces from the repository           | Fork a running sandbox, memory included, into 1 to 10 copies            |
| Editor        | An editor, or `gh codespace ssh`             | VS Code and JetBrains over SSH (`runtime sandbox ssh config --install`) |
| Billing       | By machine type while running, plus storage  | Measured CPU plus reserved memory while running; paused storage         |

## What each costs

GitHub's rates, checked 25 September 2026: compute from $0.18 an hour on a
2-core machine to $2.88 on 32 cores, "proportional to the number of processor
cores", and storage at $0.07 per GB-month. A personal account on GitHub Free
includes 120 hours of compute and 15 GB-month of storage a month; GitHub Pro
includes 180 hours and 20 GB-month.

Runtime at 2 vCPU and 4 GiB: $0.03125 an hour waiting (memory plus a CPU floor
of a twentieth of a vCPU) and $0.08 an hour with both CPUs busy.

| Usage, past any free allowance     | Codespaces, 2-core   | Runtime, 2 vCPU and 4 GiB                      |
| ---------------------------------- | -------------------- | ---------------------------------------------- |
| One hour                           | $0.18                | $0.03125 waiting, $0.08 busy                   |
| A working month, 8 hours × 21 days | 168 × $0.18 = $30.24 | 168 × $0.03125 = $5.25 to 168 × $0.08 = $13.44 |
| Stored while idle                  | $0.07 per GB-month   | $0.08 per decimal GB-month, memory included    |

An agent spends most of an hour waiting on its model, which is where measured
CPU pays: the sandbox is charged for the floor, not for two idle cores
([pricing](/docs/pricing)).

## The Runtime equivalent

A named environment per task or per user: found again if it exists, paused
after 15 quiet minutes, and woken by the next command.

```ts check
import { Sandbox } from "withruntime";

const dev = await Sandbox.getOrCreate("issue-4821", { idlePauseSeconds: 900 });
await dev.exec("git clone https://github.com/octocat/Hello-World.git repo || true", {
  timeoutMs: 120_000,
});
const run = await dev.exec("cd repo && git log --oneline -1");
console.log(run.stdout);
```

```python check
from withruntime import Sandbox

dev = Sandbox.get_or_create("issue-4821", idle_pause_seconds=900)
dev.exec("git clone https://github.com/octocat/Hello-World.git repo || true", timeout_ms=120_000)
print(dev.exec("cd repo && git log --oneline -1").stdout)
```

To look over the agent's shoulder in your own editor:

```bash no-run
runtime sandbox ssh config --install   # then connect VS Code to issue-4821.runtime
```

## Which one fits

- **Pick Codespaces** for people: a developer, a class or a reviewer who
  wants a ready editor for a repository, inside GitHub's billing and its free
  monthly hours.
- **Pick an agent sandbox** for programs: an agent that needs a fresh machine
  per task, a hundred at once, commands with structured results, network rules
  it cannot change, keys it never holds, and a bill that stays small while it waits on the model.

A paid Runtime account runs 100 sandboxes at once to start, and new accounts
get 50 free sandbox hours, no card.

More: [coding agent sandbox](/use-cases/coding-agent-sandbox),
[per-user dev environments](/use-cases/per-user-dev-environments),
[pause and resume a sandbox](/how-to/pause-and-resume-a-sandbox),
[SSH and editors](/docs/editors).

## Sources

Checked 25 September 2026.

- [GitHub: Codespaces billing](https://docs.github.com/en/billing/concepts/product-billing/github-codespaces)
- [GitHub: Codespaces deep dive](https://docs.github.com/en/codespaces/about-codespaces/deep-dive)
- [GitHub: timeout period](https://docs.github.com/en/codespaces/setting-your-user-preferences/setting-your-timeout-period-for-github-codespaces) and [automatic deletion](https://docs.github.com/en/codespaces/setting-your-user-preferences/configuring-automatic-deletion-of-your-codespaces)
- [GitHub: Codespaces REST API](https://docs.github.com/en/rest/codespaces/codespaces), [gh codespace ssh](https://cli.github.com/manual/gh_codespace_ssh)
- Runtime [pricing](/docs/pricing), [speed](/docs/speed) and [SSH and editors](/docs/editors)

Facts on this page were checked on 25 September 2026.