# Error budgets

Error budgets apply only to `PRODUCTION` SLO policies.

For a window with population `N`, objective `O` and bad count `B`:

```text
allowed_bad  = (1 - O) × N
consumed_bad = B
remaining    = max(0, allowed_bad - B)
burn_rate    = (B / N) / (1 - O)
```

The long burn rate uses the complete rolling policy window. The short burn rate uses the last five
minutes, bounded by the policy window. Latency bad events are completed requests over the exact
policy threshold; success-ratio bad events are valid terminal failures.

An operational capability can be serving while consuming budget. The UI therefore shows SLO state,
observed value and budget separately. `remaining=0` is not rewritten as a capability outage, and an
acknowledged alert does not restore budget.

Windows roll naturally as old events leave the population. A new evaluation is an immutable
snapshot, so recovery is demonstrated by later snapshots rather than rewriting history. LAB and
BACKGROUND evaluations have `allowed_bad`, `consumed_bad`, `remaining` and burn rates unset by
default.