# build.sandbox

> Talos next · Since 0.6

a behaviour touches something the engine's sandbox does not provide (`window`, `fetch`, `require`, …)

| | |
|---|---|
| Severity | `error` |

## Meaning

a behaviour touches something the engine's sandbox does not provide (`window`, `fetch`, `require`, …)

## Fix

use `ctx` instead; behaviours run in QuickJS, not a browser or Node