Agent Skills: ADR Ops

ADR Ops

An Architecture Decision Record (ADR) captures one architectural decision: what was decided, why, what was rejected, and what it costs. ADRs are append-only project memory — they exist so a future maintainer touching a subsystem can recover the reasoning behind its shape without archaeology through git history or chat logs.

This skill encapsulates a battle-tested ADR protocol and generalizes it to any repo. The default location is docs/adr/, but every script takes --dir so a repo can keep records anywhere (docs/decisions/, architecture/adr/, …).

When to write an ADR

Write one when a change has any of these properties:

• It constrains future options — a boundary, an invariant, a "we will always / never do X" rule that later work must respect.
• Multiple alternatives were seriously evaluated and the choice is not obvious in hindsight.
• The rationale is non-obvious from the code — the code shows what, the ADR preserves why.

Write one decision per ADR. If a change bundles two separable decisions, write two.

When NOT to write one

• A bug fix, refactor, or feature that follows existing architecture without changing it — that is a commit message.
• A reversible, low-stakes choice — that is a code comment.
• A point-in-time event with no forward constraint (a benchmark run, an incident write-up) — that is an audit/log entry, not an ADR.

Rule of thumb: if someone could plausibly undo this next month without re-litigating a trade-off, it is not an ADR.

Naming, location, numbering

• Path: <adr-dir>/ADR-NNN-slug.md (default <adr-dir> = docs/adr).
• NNN is zero-padded three digits, assigned sequentially: the next number is highest existing + 1. Numbers are never reused, never reordered — a superseded ADR keeps its number forever.
• slug is short kebab-case naming the subject (oauth-only-auth, per-trial-container).
• A protocol/how-to file (e.g. 00_*) sorts above the numbered records and is not part of the sequence.

The directory IS the index

Do not maintain a hand-curated numbered list as the source of truth — it drifts from the filesystem. The authoritative list is the directory itself; adr-index.sh is just a clean parse of it. Any prose list elsewhere (README, AGENTS.md) is a convenience pointer that may lag and must say so.

Canonical format (compact view)

Full template in assets/ADR-template.md; full rules in references/canonical-format.md. The shape:

---
status: accepted
date: YYYY-MM-DD
supersedes: []
superseded-by: []
touches:
  - "path/one.py"
---

# ADR-NNN: Title in Title Case

## Decision (one sentence)
<BLUF — one present-tense sentence stating the standing rule; greppable, stands alone.>

## Context
## Alternatives considered
## Consequences
### Positive / ### Negative / ### Non-goals
## See also

Fixed section order: Decision → Context → Alternatives considered → Consequences → See also. Extra sections (Migration path, Enforcement, Implementation summary) go after Consequences. For a multi-part decision, keep the one-sentence BLUF and add a ## Decision (detail) section lower down.

Frontmatter fields

| Field | Required | Rule | |---|---|---| | status | yes | proposed / accepted / superseded / deprecated (lowercase). | | date | yes | Decision date, YYYY-MM-DD. | | supersedes | yes | YAML list of ADR ids this replaces ([] if none). | | superseded-by | yes | YAML list of ADR ids that replace this ([] until superseded). | | touches | yes | YAML list of paths / globs / config keys this governs. Quote each. The grep discovery surface — grep touches: answers "is there an ADR about the thing I'm changing?" | | extends | optional | ADR ids this builds on without replacing. | | related | optional | Companion ADR ids (not parents). | | deciders | optional | Who made the call. |

A new field is a protocol change — record it in a new ADR, don't invent per-record keys.

Status lifecycle & immutability

proposed ──► accepted ──► superseded   (superseded-by: [ADR-NNN])
                │
                └────────► deprecated  (withdrawn; nothing replaces it)

ADRs are append-only. Once accepted, you do not rewrite the Decision or Context. Three change modes (full detail in references/lifecycle-and-supersession.md):

1. Supersede — the rule itself changes. Write a new ADR with supersedes: [ADR-OLD]; flip the old record's frontmatter to status: superseded + superseded-by: [ADR-NEW] in the same commit. Body stays intact (obsolete reasoning is itself a record). Supersession is bidirectional — a one-sided link is a lint error.
2. Addendum — new facts that refine an in-force decision. A dated ## Addendum — YYYY-MM-DD: <topic> at the end of the body. Never use it to quietly reverse the decision.
3. In-place edit — typos, dead links, a renamed path in touches:. Preserves meaning; never rewrites rationale.

End-to-end workflow

1. Scaffold the next record: bash scripts/adr-new.sh --dir docs/adr --title "Your decision title" (computes NNN = highest+1, derives the slug, fills frontmatter).
2. Fill it in — BLUF first, then Context, Alternatives, Consequences, See also. Keep touches: accurate; it is the discovery surface.
3. Cross-check the number against the directory to avoid a collision with a parallel session: ls docs/adr/ADR-*.md (or bash scripts/adr-index.sh).
4. If superseding, flip the old record's frontmatter in the same commit — either by hand or with adr-new.sh --supersedes ADR-OLD --apply-supersede.
5. Lint before committing: python scripts/adr-lint.py --dir docs/adr.
6. Commit with a docs(adr): conventional-commit subject, e.g. docs(adr): ADR-020 — <subject>.

Adopting ADRs in a fresh repo? Run bash scripts/adr-init.sh --first-title "…" once to bootstrap the directory + a lint-clean ADR-001. Before changing an existing subsystem, run python scripts/adr-touching.py <path> to surface any decision already governing it.

Tools

All scripts take --dir (default docs/adr), --help, and follow semantic exit codes (0 ok, 2 usage, 3 not-found, 5 precondition, 10 findings/domain-signal). Pair with the git-ops skill for the commit/PR step. The three read tools form the legs of a stool: lint = integrity, index = overview, touching = "what governs this file before I change it".

scripts/adr-init.sh — bootstrap a repo adopting ADRs cold

# Create docs/adr/, scaffold a lint-clean ADR-001, write a generated README:
bash scripts/adr-init.sh --first-title "Adopt ADRs"

# Custom dir + preview without writing:
bash scripts/adr-init.sh --dir docs/decisions --first-title "OAuth-only auth" --dry-run

Refuses to run in a directory that already holds ADR-*.md (exit 5) unless --force. The ADR-001 it scaffolds is rendered by adr-new.sh, so it lints clean immediately. The generated <dir>/README.md is self-labeled "generated — do not hand-edit; the directory is the index" and says to run adr-index to regenerate. --dry-run writes nothing.

scripts/adr-new.sh — scaffold the next ADR

# Next number, slug derived from the title, frontmatter pre-filled:
bash scripts/adr-new.sh --title "OAuth-only auth"

# Custom dir + explicit slug + proposed status, preview without writing:
bash scripts/adr-new.sh --dir docs/decisions --title "Per-trial container" \
  --slug per-trial-container --status proposed --dry-run

# Supersede an old record and flip its frontmatter automatically:
bash scripts/adr-new.sh --title "Replace router" --supersedes ADR-002 --apply-supersede

Refuses to overwrite an existing file (exit 5). Atomic write. --dry-run prints the path

• rendered content and writes nothing. --number N forces a specific number (backfilling or coordination) — use sparingly; sequential highest+1 is the discipline.

scripts/adr-index.sh — the directory as a table (read-only)

bash scripts/adr-index.sh                       # number | status | date | title
bash scripts/adr-index.sh --json | jq '.data[] | select(.status=="accepted")'

Prefers yq; degrades to a built-in parser when yq is absent (announced on stderr). Pass --output FILE to write a generated Markdown index (heading + a do not hand-edit marker + the | # | Status | Date | Title | table) atomically to a file instead of stdout — for a README pointer that you regenerate rather than hand-curate.

scripts/adr-touching.py — what governs this file? (the discovery surface)

The touches: frontmatter is the grep target answering "is there an ADR about the thing I'm changing?". This tool is that grep, done properly — match a path, glob, or config key against every ADR's touches: list.

# Before editing src/auth.py, ask what decisions constrain it:
python scripts/adr-touching.py src/auth.py        # exit 10 if an ADR governs it
python scripts/adr-touching.py 'src/**'           # glob query
python scripts/adr-touching.py --json src/ | jq '.data[].number'

Matching is bidirectional and pragmatic: exact equality; fnmatch glob either direction (touches src/** matches query src/auth.py; query src/* matches touches src/auth.py); path-prefix containment (query src/ governs touches src/auth.py, and vice-versa); config keys (file.yaml:key) by exact-or-prefix.

Guard contract (the load-bearing bit): exit 0 = no governing ADR found, exit 10 = at least one ADR governs the query. A pre-edit hook or CI step branches on it — "heads up, ADR-010 governs this path; read it before changing." Exit 3 dir not found, 2 usage.

scripts/adr-lint.py — conformance validator

python scripts/adr-lint.py --dir docs/adr        # exit 0 clean, 10 if findings
python scripts/adr-lint.py --strict --json | jq '.data[] | select(.severity=="error")'

Checks required + well-typed frontmatter, the # ADR-NNN: title matching the filename, the BLUF placement, core section order, no duplicate numbers (gaps are a warning), and supersession bidirectionality (the high-value cross-file check). Plus:

• Lifecycle consistency (errors): superseded with an empty superseded-by; deprecated with a non-empty superseded-by; an in-force (accepted/proposed) ADR carrying a superseded-by. These complement the bidirectionality check without double-reporting.
• Stale touches (warning): a touches: entry that is a literal filesystem path (not a glob, not a config key) which no longer resolves under --repo-root (default: git toplevel, else cwd) — the discovery surface may have drifted. Warning-tier only; counts toward exit 10 under --strict.

--strict makes warnings count toward exit 10. Exit 4 if a file's frontmatter is unparseable.

CI integration

ADRs only stay trustworthy if the integrity contract is machine-enforced. Gate the lint in CI; --strict turns the stale-touches drift warning into a hard signal.

# .github/workflows/adr-lint.yml
name: adr-lint
on: [pull_request]
jobs:
  lint:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - name: Lint ADRs
        run: python skills/adr-ops/scripts/adr-lint.py --strict --dir docs/adr
        # exit 10 (findings, incl. stale-touches under --strict) fails the build

Local pre-commit gate: add python scripts/adr-lint.py --strict --dir docs/adr to a pre-commit hook so a one-sided supersession or a stale discovery surface is caught before the commit lands. A pre-edit hook can additionally call adr-touching.py <changed-path> and surface the governing ADR (exit 10) before a subsystem is modified.

See also

• references/canonical-format.md — the full template, field table, and body rules.
• references/lifecycle-and-supersession.md — status lifecycle + the three change modes.
• assets/ADR-template.md — copy-ready canonical template.