# X_READINESS_CHECK_DUPLICATE

## Means

a readiness check name is registered twice

## Typical cause

two `registerReadinessCheck('<name>', check)` calls under one name. A silent replacement leaves the probe an operator believes is running unreachable, and `/readyz` green on the strength of the one that replaced it — the `cause` lists every name already registered

## Fix

name the second check for what it actually probes, e.g. `registerReadinessCheck('<name>-replica', check)` — or hold the unregister the first registration returned and call it first

[Core and runtime](/error-codes#core-and-runtime)