# X_DEV_RESTART_REQUIRED

## Means

a save reached a module that defines a primitive; only a new process serves it

## Typical cause

a slice service, a view under defineAdmin, or an action/query/entity/job file itself was saved, and the module that defines the primitive still holds the old code

## Fix

restart `x dev` — the supervised `x dev` restarts itself; an embedded `startDev()` passes `onRestart`

[CLI and verify](/error-codes#cli-and-verify)