---
key: docs.decision-lifecycle
title: 2026-07-21 — Decision records carry a lifecycle schema, validated by a script; append-only-by-diff is retired (#521)
status: active
since: '2026-07-21'
supersedes: docs.append-only-guard@2026-07-12
superseded-by: none
rule: 'every decision `##` record (active or archived) carries a 5-field metadata block (`key`, `status`, `since`, `supersedes`, `superseded-by`) checked by `scripts/decisions_validate.py`; a record is never deleted or line-edited to reverse a call — it is moved to `docs/decisions/archive/` with `status: superseded`/`retired` and a reciprocal `superseded-by`/`supersedes` key pair to its replacement.'
signals: 'decision lifecycle, supersession, archive · paths: `scripts/decisions_lib.py`, `scripts/decisions_validate.py`, `scripts/build_decisions_catalog.py`, `docs/decisions/archive/` · issues: #520, #521'
mechanics: '`scripts/decisions_validate.py` (`PYTHONPATH=. python3 scripts/decisions_validate.py`); catalog regen `scripts/build_decisions_catalog.py`; `docs/decisions/migration-map.md`'
---

**This replaces `docs.append-only-guard` (ersatztv#303 H9), not just extends it.** The old guard treated
`docs/decisions.md` as a single append-only text file: any line-delete was blocked by a Husky
`commit-msg` hook + CI job, and a "supersession" was a hand-written `> **Superseded …**` banner
prepended to the old entry plus an `(superseded)` Index tag — prose conventions an agent had to
remember and apply correctly by hand, with no machine check that the banner, the tag, and the new
entry's back-reference actually agreed with each other. That is exactly the failure mode this arc
(#520/#521) set out to fix: state should be derived and checked, not asserted in prose (the same
throughline as #303 H6's `## Done-when`).

**The new model.** Every decision record — whether still in force or not — gets a `key` (dotted,
stable identity independent of its heading text or which file it lives in), a `status`
(`active`/`superseded`/`retired`/`legacy-unmigrated` for anything not yet carrying the schema), a
`since` date, and a reciprocal `supersedes`/`superseded-by` pair of keys. `scripts/decisions_lib.py`
parses the schema; `scripts/decisions_validate.py` enforces: at most one `active` record per key;
`superseded`/`retired` records MUST live under `docs/decisions/archive/`, never in an active file;
an `active` record MUST NOT live under `archive/`; every `supersedes`/`superseded-by` key must
resolve to a record that actually exists (active or archived); and — replacing the append-only
guard's line-delete detection — a record's rationale prose (the schema strips only the contiguous
metadata block before comparing) must not change between a PR's base and head unless the commit
carries the rationale-edit marker (`Decisions-Edit: yes`, a git trailer since #609 — see
`ci.decisions-edit-trailer`), and a record that disappears from the active set without a matching
archive copy is flagged as an unlogged removal. `scripts/build_decisions_catalog.py` regenerates
`docs/decisions/README.md`, a compact router listing only `active` records by key, so an agent
doesn't have to read the full chronological log (or the archive) to find the current rule.

**Why this is a strictly better enforcement of the same spirit, not a loosening.** The old guard's
actual invariant was never "no line may change" — it was "history is never silently rewritten to
erase *why we changed our mind*." A hand-prepended banner satisfied that invariant by convention; a
validator that checks reciprocal keys, archive placement, and rationale-prose stability satisfies it
by construction, and additionally catches classes of mistake the old guard could not (a supersession
banner added without moving the entry out of the active read-path; a `superseded-by` reference to a
key that doesn't exist; two `active` records quietly claiming the same key after a copy-paste).
The rationale-edit marker is kept, narrowed to its one remaining legitimate use — an actual
rationale-prose edit (fixing a factual error) — since routine lifecycle moves (a status flip, an
archive relocation) are now marker-free and machine-checked instead.

**This PR is the first to exercise the new regime, on itself.** `docs.append-only-guard` (the H9 half
of #303's combined H9/H3 entry; H3's root-screenshot guard is untouched and stays active) is marked
`status: superseded` and relocated to `docs/decisions/archive/release-ci-governance.md`, with this
record as its `superseded-by` and this record's `supersedes` pointing back — the same-PR supersession
pattern the new rule itself mandates for every future reversal. `docs/decisions/migration-map.md`
tracks the legacy-heading → key → status → location mapping as the rest of the log migrates
(ersatztv#520/#521, ongoing — most existing headings remain `legacy-unmigrated` until touched).
