# ADR-0038: Versioned SLO and error-budget model

## Status

Accepted in M14 on 2026-08-27.

## Decision

Separate immutable SLI definitions from versioned SLO policies and immutable evaluation snapshots.
Only production policies receive error budgets. Minimum population and freshness are evaluated
before health; short and rolling-window burn rates remain distinct.

## Consequences

Threshold changes cannot rewrite historical meaning. LAB evidence cannot masquerade as production
reliability. A serving capability can consume budget without being misreported as unavailable, and
too little evidence remains explicitly `INSUFFICIENT_DATA`.