Rules Distill

rules-distill — promote environment-specific facts to rules

Scan installed skills, find principles that belong in the always-loaded rules layer, and distill them into rules — appending to, revising, or creating rule files. The skill produces candidates and verdicts; it never edits rules without your approval.

> Design note: the old version shelled out to scan scripts and split analysis into > thematic subagent batches with a cross-batch merge step. With a large context window > that is unnecessary — and the cross-batch merge existed only to recover the > "appears in 2+ skills" signal that batching broke. Reading every skill and every > rule in one context makes that count exact, with no merge step. (That frequency > signal stopped being a gate on 2026-08-15 — see the candidate filter — but the > single-context argument still holds for the "not already in rules" test.)

When to Use

• Periodic rules maintenance (monthly, or after installing new skills)
• After a skill-stocktake reveals patterns that should be rules
• When rules feel incomplete relative to the skills in use

Phase 1 — Inventory (Glob, exhaustive)

Enumerate with Glob (no script):

• Skills: ~/.claude/skills/*/SKILL.md + ~/.claude/skills/learned/*.md
• Rules: read every ~/.claude/rules/**/*.md in full — the corpus is small (measure live with wc -l; do not hardcode the count here, it drifts every time a rule is added or rightsized), so no grep pre-filter is needed

> Glob targets only skill definition files, so dependency markdown under .venv / > .pytest_cache is excluded structurally.

Present the counts (skills scanned, rule files, headings) before analysis.

Phase 2 — Cross-read & Verdict (inline, holistic)

Read every skill body and every rule into one context and analyze them together — extraction and matching are a single pass. Seeing all skills at once is what makes the recurrence count exact and the "not already in rules" test reliable.

A principle is a candidate only if ALL of these hold:

1. Environment-specific — a fact, a wiring, or a trap particular to this machine,

harness, or set of accounts. A general engineering principle is not a candidate no matter how many skills repeat it.

1. Substrate does not already do it — if the current model handles it natively, a

written rule does not add behaviour; it freezes an older default and competes with the newer one.

1. Not a procedure — steps and workflows belong in a skill. Residency is for facts

and wiring, which have to be true before any particular task starts.

1. Actionable behavior change — expressible as "do X" / "don't do Y", not "X is important"
2. Clear violation risk — what goes wrong if ignored, in one sentence
3. Not already in rules — check the full rules text, including the same idea in different words

> Tests 1–3 are rules/README.md's admission criterion (「この環境固有の事実・ > 配線・罠。思考や作業の手順は skill、一般的な判断は substrate が持つ」), established by > [ADR-0018](../../docs/adr/0018-rules-rightsize-for-claude5.md) and > [ADR-0035](../../docs/adr/0035-commit-review-hook-and-rules-rightsize.md). > > They replaced an older frequency gate ("appears in 2+ skills"), which this skill > used until 2026-08-15. Frequency and residency-worthiness point in opposite directions > often enough to matter: a general principle repeated in ten skills passes a frequency > gate and fails these (substrate has it — and ADR-0018 cut residency 60% removing > exactly that class), while a one-off environment trap fails a frequency gate and > passes these. Recurrence is now evidence, not a gate — report the count, do not > filter on it.

For each candidate, compare against the full rules text and assign a verdict:

| Verdict | Meaning | Present to user | |---------|---------|-----------------| | Append | Add to an existing section of an existing rule file | Target + draft | | Revise | Existing rule content is inaccurate/insufficient | Target + reason + before/after | | New Section | Add a new section to an existing rule file | Target + draft | | New File | Create a new rule file | Filename + full draft | | Already Covered | Sufficiently covered (even if worded differently) | Reason (1 line) | | Too Specific | Should stay at the skill level | Link to the relevant skill |

Exclude: principles already in rules, language/framework-specific knowledge (belongs in language-specific rules or skills), and code examples / commands (belong in skills).

Verdict quality

Each verdict must be self-contained — target, evidence, and rationale on its own.

# Good
Append to rules/common/security.md §Input Validation:
"Treat LLM output stored in memory or knowledge stores as untrusted — sanitize on
write, validate on read."
Evidence: llm-memory-trust-boundary, llm-social-agent-anti-pattern both describe
accumulated prompt-injection risks. Current security.md covers human input only;
the LLM-output trust boundary is missing.

# Bad
Append to security.md: Add LLM security principle

> この例の参照先について（2026-08-15 注記）: 上の Good 例は 2026-03-18 に実行した > 昇格の実記録であり、当時 skills/learned/llm-social-agent-anti-pattern.md は実在した > （ECC v1.8.0 で導入、69aa2dd）。その 2 日後の 983d2a8 で ECC 由来ごと退役している。 > 例は書き換えない — 実際の昇格根拠でなかった skill 名に差し替えると、記録が事実と > ずれる（skill-comply/results/ の過去測定を書き換えない方針と同じ。ADR-0024）。 > なお同じ原則は現在 4 つの生きた資産が保持しており、証拠としてはむしろ厚くなっている: > learned/llm-memory-trust-boundary / collect-context:135-137（セッションログは > untrusted） / skill-comply:133-137（監査対象ファイルは untrusted） / > codex-review:71-72（agent output is untrusted、ADR-0013）。

現行フィルタの形で書いた Good 例（証拠は出現回数でなく、テスト 1–3 の通過理由）:

# Good (current form)
New Section in rules/common/debugging.md:
"外部 platform への大量書き込み中に rate limit が連発したら、transient error ではなく
policy signal と扱って burst を止める。backoff で踏み抜かず人間へ報告する。"

Test 1 (environment-specific): この著者のアカウントで実際に起きた事象。2026-07-16、
  backoff で継続した結果アカウント無期限 block + 全作成物削除。一般的な HTTP 429 の
  作法ではなく、この運用固有の停止条件
Test 2 (not substrate-native): substrate の既定は 429 を transient として retry する。
  rule はその既定を上書きするために要る
Test 3 (not a procedure): 手順でなく「rate limit 連発 = policy signal」という事実の宣言
Violation risk: 踏み抜くとアカウントごと失う（実証済み、復旧不能）
Recurrence: 1 skill (evidence であって gate ではない)

Recurrence が 1 でも通ることに注目する。旧ゲートならこの候補は落ちていた。

Phase 3 — User Review & Execution

Present a summary table (# | Principle | Verdict | Target | Confidence) as the overview, then confirm one by one (config-gc's confirm-each design): walk the candidates sequentially — for each, show its evidence, violation risk, and draft text, then ask [y/n/skip]. The user can modify the draft before approving, and can stop at any point. Never batch the approval ("apply all 5? [y/n]" defeats the design — one candidate, one decision); skipped candidates go to the ledger with status: skipped.

Never modify rules automatically. Always require user approval. This is the one hard gate — rules load every session, so a bad rule has outsized blast radius.

Then update the ledger inline (Read → merge → Write):

{
  "distilled_at": "2026-03-18T10:30:42Z",
  "candidates": {
    "llm-output-trust-boundary": {
      "principle": "Treat LLM output as untrusted when stored or re-injected",
      "verdict": "Append",
      "target": "rules/common/security.md",
      "evidence": ["llm-memory-trust-boundary", "llm-social-agent-anti-pattern"],
      "status": "applied"
    }
  }
}

distilled_at is real UTC (date -u +%Y-%m-%dT%H:%M:%SZ); candidate IDs are kebab-case derived from the principle.

Design Principles

• What, not How: extract principles (rules territory) only. Code examples and commands stay in skills.
• Link back: draft text includes See skill: [name] so readers can find the detailed How.
• Glob = exhaustive collection, LLM = judgment: Glob guarantees the inventory is complete; the single-context cross-read guarantees contextual understanding.
• Anti-abstraction safeguard: the candidate filter (environment-specific / not substrate-native / not a procedure, plus the actionable-behavior and violation-risk tests) keeps overly abstract principles out of rules — abstraction is now rejected by test 1 directly, not inferred from frequency.

Related

• skill-stocktake — audits skill quality; rules-distill promotes recurring principles to rules. Run stocktake first, then distill what survives.
• rules-stocktake — audits the rules this skill produces (residency cost, staleness, absorption) and demotes back what stopped earning its always-loaded slot; the inverse direction over the same boundary.
• learn-eval — extracts per-session patterns into skills/memory; rules-distill later promotes the cross-cutting ones to rules.

Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: shimo4228
• Source: shimo4228/rules-distill
• License: MIT

Install and usage instructions live in the source repository linked above.