# X_MUTATOR_CLOCK_MISSING

## Means

a mutator declares conflict: 'last-write-wins' and its entity has no number clock column

## Typical cause

`mutator({ conflict: 'last-write-wins' })`, checked at declaration. An entity row in its output has no **number** `updatedAt` the server writes (a `timestamp()` string does not count), or the output carries no entity row at all. Core's `resolveConflict` could then never prove the local row newer, so the server row would win every time

## Fix

add `updatedAt` (a number, epoch ms, written by the server) to the entity, or declare `conflict: 'server-wins'`. With no entity row in the output: return the entity row from the mutator's output, or declare `conflict: 'server-wins'`

[Actions](/error-codes#actions)