ADR-021: Reserved

Status: Reserved Date: 2026-04-24

This slot is intentionally empty. ADR-020 and ADR-022 both exist; no ADR-021 was ever written.

The docs/decisions/README.md rule is "Never reuse a number, even for a superseded record — the slot stays occupied by the old decision." This file exists so a reader scanning the directory does not hunt for a missing file, and so the next author does not mistakenly claim 021 for a new decision.

Tracked in docs/DEBT.md → adr-021-missing. If a future ADR wants this slot, the normal rule applies: pick the next unused number instead. This file is not a placeholder for "write 021 later" — it documents the permanent absence.