# What is idle pause?

Idle pause suspends a sandbox or VM after a set time with no activity, keeping its state, so nobody pays compute for a machine left open.

**On Runtime `idlePauseSeconds` pauses a sandbox with its files, memory and
running processes, and the next request wakes it, usually in about half a
second.** A 2 vCPU, 4 GiB sandbox left running with nothing to do costs
$0.03125 an hour; paused, it costs $0.08 per GB of saved state per 30-day
month ([pricing](/docs/pricing#paused-storage)).

## Why it matters for AI agents

Agents are idle most of the time. A coding agent waits on its model between
commands, and a user who opened a session goes to lunch without closing it.
Code that forgets to call `stop()` after an error leaves a machine running
until someone notices. Idle pause is a timer on the server that catches all of
these, without the agent having to remember anything.

Pausing is better than stopping for this job because nothing is lost. A dev
server, an open REPL or a half-built project is still there after the wake.

## Runtime's idle pause

| Setting or behaviour    | Detail                                                                   |
| ----------------------- | ------------------------------------------------------------------------ |
| `idlePauseSeconds`      | 60 to 86,400 seconds; 0 turns it off                                     |
| What counts as activity | An exec, file, process, terminal, desktop or preview request             |
| Default                 | 300 seconds until first use, with no `timeoutSeconds`, image or snapshot |
| `idlePauseUnusedOnly`   | `true` for that default; `false` for an idle time you set                |
| After the pause         | The next request wakes it, unless `autoWake` is `false`                  |
| A visit to a preview    | Wakes it behind a short "Waking up" page that reloads itself             |
| Change it later         | `sbx.update({ idlePauseSeconds })`, or the API's `:update`               |

An idle time you set counts from the last request. The default only catches a
sandbox that was created and never used ([API](/docs/api)).

## Set it

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

const sbx = await Sandbox.create({ idlePauseSeconds: 600 }); // ten quiet minutes
console.log(sbx.info.idlePauseUnusedOnly); // false: counts from the last request
await sbx.update({ idlePauseSeconds: 0 }); // never pause for idleness
await sbx.stop();
```

```python check
from withruntime import Sandbox

sbx = Sandbox.create(idle_pause_seconds=600)
sbx.update(idle_pause_seconds=0)
sbx.stop()
```

## Idle pause and the lease

Idle pause answers "nobody is using it". The [lease](/glossary/sandbox-lease)
answers "it has run long enough": `timeoutSeconds` ends the run at a fixed time
whatever is happening, then pauses or stops as `onLeaseEnd` says. Most agent
sandboxes want both. A wake from idle gets a fresh lease of the sandbox's own
`timeoutSeconds` and is billed from the moment it runs again
([wake on request](/docs/javascript#wake-on-request)).

## Related

- [How to pause and resume a sandbox](/how-to/pause-and-resume-a-sandbox)
- [What is a sandbox lease?](/glossary/sandbox-lease)
- [How to preview apps an AI agent builds](/use-cases/preview-agent-built-apps)
- [What is a warm pool?](/glossary/warm-pool)

Facts on this page were checked on 25 September 2026.