# X_TELEMETRY_SAMPLER_ARG_INVALID

## Means

the trace sampling ratio is not a number between 0 and 1

## Typical cause

`OTEL_TRACES_SAMPLER_ARG` holding a value outside `[0, 1]`, or one that is not a number. Read at the first span, not at boot — so it warns through the logger and samples **every** trace rather than killing a process mid-request over a sampling typo. Losing the traces silently is the worse failure; the bill is the loud one

## Fix

`set OTEL_TRACES_SAMPLER_ARG=0.05` — the `cause` names the spelling it read

[Metrics](/error-codes#metrics)