4.3. Set both tolerances🔗

A comparison threshold has an absolute allowance in the metric's native unit and a relative allowance in basis points:

let config : ComparisonConfig := {
  metric := .p95Ns
  threshold := {
    absolute := 500_000
    relativeBps := 1000
  }
}

For a nanosecond metric, this allows 0.5 milliseconds and 10%. An increase is a regression only when it is strictly greater than both. This keeps a high percentage on a tiny span below the absolute noise floor, while a small absolute change on a long span stays below the relative allowance.

When the baseline is zero, only the absolute allowance can be evaluated.