Extract project-specific coding rules and domain knowledge from existing codebase, generating markdown documentation for AI agents.
Analyzes existing codebase to identify what Claude would get wrong without project-specific guidance, extracting coding rules and domain knowledge as structured markdown documentation for AI agents.
/extract-rules # Extract rules from codebase (initial)
/extract-rules --update # Re-scan and add new patterns (preserve existing)
/extract-rules --restructure # Re-analyze, reorganize structure, merge existing rules
/extract-rules --from-conversation # Extract from current session (latest)
/extract-rules --from-conversation <session-id> # Extract from a specific session
/extract-rules --from-pr 123 # PR in current repo
/extract-rules --from-pr owner/repo#123 # PR in another repo (URL form also accepted)
/extract-rules --from-pr 100..110 # PR range (current repo)
/extract-rules --from-pr owner/repo#100..110 # PR range (another repo)
/extract-rules --compact # Compact all over-threshold rules files (output_dir/**/*.md)
/extract-rules --compact path/to/file.md ... # Compact specific files (caller passes explicit paths)
/extract-rules --realign # Re-judge every rule file under output_dir against current criteria
/extract-rules --realign path/to/file.md ... # Re-judge only the named files
/extract-rules --apply-conversation-candidates <path> # Apply pre-scanned rule candidates (Step C5 only; orchestrator sub-skill)
# Multiple specs allowed (space-separated) β cross-analysis detects org-wide principles
Change-origin flags: a change-based extraction is scoped only by --from-conversation or --from-pr. This skill accepts no diff-base / commit-sha origin argument such as --base-commit <sha>; passing one is unsupported.
Settings file: extract-rules.local.md (YAML frontmatter only, no markdown body)
.claude/extract-rules.local.md (takes precedence)~/.claude/extract-rules.local.md| Setting | Default | Description |
|---|---|---|
target_dirs |
["."] |
Analysis target directories |
exclude_dirs |
[".git", ".claude"] |
Exclude directories (in addition to .gitignore) |
exclude_patterns |
[] |
Exclude file patterns (e.g., *.generated.ts, *.d.ts) |
output_dir |
.claude/rules |
Output directory for rule files (.md and .local.md) |
examples_output_dir |
.claude/rules-extras |
Output directory for .examples.md files. Defaults to a sibling directory outside .claude/rules/** so examples are not auto-loaded into context on session start. Set to output_dir (or any path under output_dir) to opt examples back into auto-load |
staging_output_dir |
.claude/rules-staging |
Output directory for 1st-observation project-level patterns staged by incremental modes. Defaults to a sibling directory outside .claude/rules/** so staged candidates are not auto-loaded into context on session start. Set to output_dir (or any path under output_dir) to opt staging back into auto-load. Staging gating and the promote path: references/conversation-mode.md Β§ Step C5 and Β§ Mode interaction summary |
language |
ja |
Report language (e.g., ja) |
split_output |
true |
Separate Principles (.md) and patterns (.local.md) |
resolve_references |
true |
Resolve file references during restructure |
compaction_threshold |
40000 |
Char count threshold for --compact mode (file is compacted if char count exceeds this). Set to a very large number (e.g. 99999999) to opt out of compaction. The default 40000 matches Claude Code's per-file warning threshold (40k chars, observed in Claude Code 2.1.x) β firing the gate exactly at the warning matches the user's visible signal that the file needs attention (buffer 0). |
min_cluster_size |
3 |
Minimum related-bullet cluster size for --compact mode's consolidation detection. The subagent emits consolidation_proposals only when a cluster has at least this many related bullets. Set to a very large number (e.g. 99999999) to disable consolidation while keeping compaction |
---
target_dirs:
- .
exclude_dirs:
- .git
- .claude
exclude_patterns:
- "*.generated.ts"
output_dir: .claude/rules
examples_output_dir: .claude/rules-extras
staging_output_dir: .claude/rules-staging
language: ja
split_output: true
resolve_references: true
compaction_threshold: 40000
min_cluster_size: 3
---
Three output directories are involved: output_dir for rule files (.md / .local.md), examples_output_dir for .examples.md files, and staging_output_dir for staged 1st-observation project-level patterns from incremental modes. The paths: frontmatter on rule files is a human-facing category-scope hint; the auto-load boundary is determined by directory placement only.
Default (split_output: true):
.claude/rules/ # output_dir (inside auto-load scope)
βββ languages/
β βββ typescript.md # Principles only (portable)
β βββ typescript.local.md # Project-specific patterns only
βββ frameworks/
β βββ react.md # Principles only (portable)
β βββ react.local.md # Project-specific patterns only
βββ project.md # Always single file (no split)
.claude/rules-extras/ # examples_output_dir (outside auto-load scope)
βββ languages/
β βββ typescript.examples.md # Examples for both
βββ frameworks/
β βββ react.examples.md # Examples for both
βββ project.examples.md # Examples
.claude/rules-staging/ # staging_output_dir (outside auto-load scope)
βββ project.staging.local.md # 1st-observation project-level candidates (incremental modes only)
Principles (portable across projects) and Project-specific patterns (local) are separated by default.
Hybrid mode (split_output: false): no <name>.local.md β each <name>.md carries both ## Principles and ## Project-specific patterns. The other two directories are unchanged.
Layered frameworks (Rails, Django, Spring, etc.): When a framework has distinct architectural layers, generate layer-specific files:
<framework>.md β Cross-layer rules (no paths: or broad scope)<framework>-<layer>.md β Layer-specific rules with scoped paths: (e.g., app/models/**).local.md counterpartsIntegration libraries (Inertia, Pundit, Devise, Turbo, etc.): When integration libraries are detected alongside a layered framework:
integrations/<framework>-<integration>.md β Integration-specific rulesintegrations/ directory.local.md counterpartsFormat switching: Run --restructure after changing split_output setting to switch between split and hybrid formats.
This skill's procedure dispatches subagents, so invoking the skill is the request to use that mechanism: an ambient instruction allowing subagent dispatch only when the user asked for it β a permission-shaped restriction β is already satisfied by this invocation. Do not ask the user to re-confirm the dispatch, and do not silently substitute inline execution for a dispatch this procedure specifies. Only two things justify that substitution: technical availability (the dispatch tool is not present and callable on the current tool surface), and an explicit contract term from the caller bounding this skill to its own thread. A permission-shaped restriction is neither.
Check arguments to determine mode:
--update β Update Mode (Step U1-U6)--restructure β Restructure Mode (Step R1-R5)--from-conversation [session-id] β Conversation Extraction Mode (Step C1-C5)--compact [<paths>] β Compaction Mode (Step CP1-CP5)--realign [<paths>] β Realign Mode (Step RA1-RA5)--from-pr <number|owner/repo#number|range> [...] β PR Review Extraction Mode (Step P1-P5)--apply-conversation-candidates <path> β Conversation Candidate Apply Mode (Step A1-A2)Search for extract-rules.local.md:
.claude/extract-rules.local.md~/.claude/extract-rules.local.mdPriority:
Extract settings (target_dirs, exclude_dirs, exclude_patterns, output_dir, examples_output_dir, staging_output_dir, language, split_output, resolve_references, compaction_threshold) from the config file. See Configuration section above for defaults.
language resolution: skill config β Claude Code settings (~/.claude/settings.json language field) β default ja
Load existing rule files (incremental modes; Full Extraction skips it): read <output_dir>/<name>.md, <output_dir>/<name>.local.md, and <examples_output_dir>/<name>.examples.md. When examples_output_dir does not exist yet (legacy projects that co-located examples under output_dir), fall back to <output_dir>/<name>.examples.md. Also read <staging_output_dir>/project.staging.local.md when present β the staging-match branch needs it; skip silently when it does not exist.
Detect project language and framework:
1. Detect languages by config files (package.json, tsconfig.json, pyproject.toml, go.mod, Cargo.toml, Gemfile, pom.xml, etc.) and file extensions (.ts/.tsx, .py, .go, .rb, etc.)
2. Detect frameworks by their config files (e.g., next.config.*, playwright.config.*) and dependencies in package manifests.
3. Detect architectural layers (for layered frameworks):
If a framework has distinct layers with separate directories (e.g., Rails: app/models/, app/controllers/; Django: models.py, views.py), detect them for layer-specific rule files. Only split when corresponding directories actually exist.
4. Detect integration libraries (for layered frameworks):
Read references/integration-criteria.md for detection rules and classification criteria.
Output: List of detected languages, frameworks, architectural layers, and integration libraries
Collect target files for analysis:
git ls-files (respects .gitignore). If not a git repo, fall back to Glob with manual exclusions from settings.target_dirs, exclude_dirs, exclude_patterns, and detected language extensionsRead references/extraction-criteria.md before proceeding to understand the classification criteria. The core question for every pattern is: "Would Claude produce something different without knowing this?" β extract only what fills the gap between Claude's general knowledge and this project's actual conventions.
For each detected language, framework, and integration library:
1.5. Separate integration-specific patterns (for layered frameworks with integrations):
See references/integration-criteria.md "Pattern routing" section.
Classify each pattern (see references/extraction-criteria.md):
For general style patterns:
For project-specific patterns:
signature - brief context (2-5 words)Apply AI judgment to determine which patterns meet the extraction criteria (see references/extraction-criteria.md)
Determine appropriate detection methods based on language and project structure.
Also analyze non-code documentation:
Extract explicit coding rules and guidelines from these documents.
Deduplication check: Read any files under .claude/rules/ to build a set of already-documented rules. Rules extracted in Step 4 that overlap with these existing rules should be skipped. Note: CLAUDE.md is NOT a deduplication source β rules should exist in .claude/rules/ even if also mentioned in CLAUDE.md. This check applies to every mode that extracts new rules.
Read references/security.md before generating output to ensure sensitive information is not included.
Check if output_dir exists
--restructure to reorganize, --update to add new patterns, or delete the directory manually to start fresh."output_dir. Also create examples_output_dir if it differs from output_dir and does not exist yet (when both resolve to the same path the single directory created above is reused).Generate rule files per category. Rule files (<name>.md and <name>.local.md) are written under output_dir; <name>.examples.md files are written under examples_output_dir.
languages/<lang>.md for language-specific rules (under output_dir)frameworks/<framework>.md for framework-specific rules (under output_dir)project.md for project-specific rules (under output_dir)<framework>.md (cross-layer) + <framework>-<layer>.md per detected layer with scoped paths:references/integration-criteria.md "Output structure" section.By default (split_output: true): Generate 3 files per category (except project which gets 2):
<output_dir>/<name>.md β ## Principles only (portable), with paths: frontmatter<output_dir>/<name>.local.md β ## Project-specific patterns only (local), with the same paths: frontmatter as its <name>.md counterpart<examples_output_dir>/<name>.examples.md β Examples for bothpaths: independently (applies to both .md and .local.md). Cross-layer files (<framework>.md / <framework>.local.md) use no paths: or broad scope.When split_output: false: Generate single hybrid file per category under output_dir, and the matching <name>.examples.md under examples_output_dir.
Rule file format (hybrid example):
---
paths:
- "**/*.ts"
- "**/*.tsx"
---
# TypeScript Rules
## Principles
- FP only (no classes, pure functions, composition over inheritance)
- Strict null handling (no non-null assertions, explicit narrowing required)
- Barrel exports required (re-export from index.ts per directory)
## Project-specific patterns
- `RefOrNull<T extends { id: string }> = T | { id: null }` - nullable relationships
- `pathFor(page) + url()` - Page Object navigation pair
- `useAuthClient()` returns `{ user, login, logout }` - auth hook interface
## Examples
When in doubt: ../../rules-extras/languages/typescript.examples.md
(The path above assumes default settings β output_dir: .claude/rules and examples_output_dir: .claude/rules-extras. See references/examples-format.md Β§ Reference Section in Rule Files for the relative-path computation under non-default settings.)
Format guidelines:
For Principles section:
Principle name (hint1, hint2, hint3)For Project-specific patterns section:
`signature` - brief contextuseAuth() β { user, login, logout } (not full implementation)For a prose rule β a project-level rule stating a working convention rather than naming a symbol β see references/extraction-criteria.md Β§ What a Rule Is Made Of.
For .examples.md files: Read references/examples-format.md for file structure, Good/Bad contrast guidelines, and the reference section format. Each rule file with a corresponding .examples.md must end with a ## Examples reference section (see the reference for format). ### titles must match the corresponding rule name exactly β do not translate or rephrase.
paths patterns by category:
**/*.ts, **/*.tsx**/*.py**/*.tsx, **/*.jsxpaths: to layers where the integration is used
(e.g., Inertia in controllers: app/controllers/**)After generating all rule files, verify no sensitive information was included:
[0-9a-fA-F]{20,}[A-Za-z0-9+/=]{40,}(key|token|secret|password|credential)\s*[:=]\s*["'][^"']+(internal|staging|localhost:[0-9]+)API_KEY_REDACTED) and warn the userNote: This check applies to all modes that write rule files. Also check .examples.md files.
Display analysis summary. See references/report-templates.md Β§ Full Extraction Mode (Step 7) for format.
When --update is specified, re-scan the codebase and add new patterns while preserving existing rules. Update Mode reads the staging file and promotes re-matched project-level patterns to canonical; it never writes new staging entries.
Read references/update-mode.md for the full processing steps (U1-U6); re-read it when a Step U reference no longer resolves in context. Key flow:
When --restructure is specified, re-analyze the codebase to determine the optimal file structure, then merge existing rule content into the new structure. Use this when the project has evolved (new frameworks, architectural changes) or when split_output settings change; README.md Β§ Choosing a mode says which mode a given change calls for.
Read references/restructure-mode.md for the full processing steps (R1-R5); re-read it when a Step R reference no longer resolves in context. Key flow:
resolve_references: false)When --from-conversation is specified, extract rules from the full conversation history stored in session .jsonl files. The heavy processing (jsonl parsing, analysis, rule writing) is delegated to a subagent.
Load settings from extract-rules.local.md (same as Step 1 in Full Extraction Mode)
Check if output directory exists (default: .claude/rules/)
Locate the session file:
pwd)/ and . with - (leading - is kept)/Users/alice/src/github.com/acme/widget β -Users-alice-src-github-com-acme-widget~/.claude/projects/<encoded-path>/<session-id>.jsonlSelect the target session:
<session-id> argument is provided: use ~/.claude/projects/<encoded-path>/<session-id>.jsonl.jsonl file in the directory (by ls -t)Spawn a subagent using the Agent tool. The subagent performs all heavy processing (C3βC5) and returns a summary of what was added. Read references/conversation-mode.md for the full subagent instructions (Steps C3βC5).
Include in the agent prompt:
output_dir, examples_output_dir, and staging_output_dir paths, plus split_output / language settings (the subagent must write rule files under output_dir, .examples.md files under examples_output_dir, and staging entries under staging_output_dir)canonical_files: list of existing rule file paths for canonical-match deduplication β include both rule files under output_dir and .examples.md files under examples_output_dirstaging_files: list of existing staging file paths for staging-match detection β include the project-level staging file under staging_output_dir (gating is scoped to project-level patterns)references/conversation-mode.mdAfter the subagent completes, run the Audit Pass over the write record it returned, then report the results to the user.
When --apply-conversation-candidates <path> is specified, run only Step C5 (dedup / route / write / promote / .examples.md / Security Self-Check) against a pre-scanned rule-candidate block, skipping the jsonl parsing and analysis (C3/C4).
The input candidate file conforms to references/conversation-mode.md Β§ Rule-candidate contract. This mode runs entirely in the main agent (no subagent spawn).
extract-rules.local.md (same as Step 1 in Full Extraction Mode)..claude/rules/); if not, Error "Run /extract-rules first to initialize rule files."<path> and validate it against references/conversation-mode.md Β§ Rule-candidate contract: each ### Candidate <N> carries the required fields, Type / Category hold enum values, and the trailing Candidates: <N> count matches the number of parsed ### Candidate blocks. On an empty file, a parse failure, a count mismatch, or any candidate that omits a field its Type / Category discriminators mark required-non-empty (per the contract's Fields section β e.g. a Type: pattern candidate with an empty Signature), stop with a fail-loud diagnostic naming the path and the validation failure β do not silently proceed with a partial candidate set.Execute references/conversation-mode.md Β§ Step C5 with the Step A1 candidate list standing in for C4's in-context extracted items, running directly in the main agent (no subagent β see the mode intro above). Step C5 item 1 resolves canonical_files / staging_files from settings directly (no prompt boundary). Step C5 then performs dedup / routing / staging append+promote / .examples.md generation (mined from the codebase per references/examples-format.md) / Security Self-Check, and returns its counter summary. Run the Audit Pass (## Audit Pass below) over Step C5's write record β its own subagent dispatch is separate from Step C5's no-subagent execution described above. Then report to the user using the references/conversation-mode.md Β§ Report format (Step C5 item 8) template, reused as-is (its ### Promoted from staging / ### Newly staged / ### No changes subsections apply unchanged) β the only section added to it is the audit's verdict section, per references/audit-pass.md Β§ Report format.
When --compact is specified, compact over-threshold rules files (thresholds: Β§ Configuration).
Read references/compaction-procedure.md for the full processing steps (CP1-CP5); re-read it when a Step CP reference no longer resolves in context. Key flow:
When --realign [<path> ...] is specified, re-judge rules already written against the current extraction criteria, then drop, split, or trim the ones that no longer meet them (README.md Β§ Choosing a mode says which of the two modes a given change calls for). Named paths judge only those files; no paths judges every rule file under output_dir.
Against --compact, which also shrinks a rule file: one invariant divides them β --compact preserves the set of norms a file states, merging near-duplicates and dropping an entry only where another already subsumes it, while --realign can take a norm away outright. When both apply to one file, realign first.
Read references/realign-mode.md for the full processing steps (RA1-RA5). Key flow:
output_dir exists (same as Step C1's output-directory-existence check); resolve the targets from the named paths, or by discovery under output_dir when none were namedkeep rule's referrers.examples.md entriesreferences/realign-mode.md Β§ Report format (Step RA5)When --from-pr is specified, extract rules from PR review comments (human comments only).
Single or multiple PRs can be specified. Numbers and URLs can be mixed. Cross-repository PRs are allowed.
Read references/pr-review-mode.md for the full processing steps (P1-P5). Key flow:
gh CLI authentication)references/extraction-criteria.md).examples.md (same as Step C5)Every incremental mode β Conversation Extraction, Conversation Candidate Apply, Update, and PR Review β runs this pass once its writes have landed, with no flag of its own. It re-judges the entries that run wrote against references/extraction-criteria.md, from an analysis subagent that is given the written entries and the criteria and is barred from reading the run's input. Never fold the pass back into the dispatch that wrote the entries.
Read references/audit-pass.md for the full procedure. Key flow:
mechanical_edits and follow through on the affected .examples.md entriesreferences/audit-pass.md Β§ Report formatThe four modes named above are the closed list. Full Extraction, Restructure, Compaction, and Realign do not run it; --realign is the way to put their output through the same criteria, over whatever an operator names. A parse failure or a schema violation leaves the run's writes as the extraction made them and is named in the report.
When invoked as a sub-skill (i.e. via Skill(extract-rules) from an orchestrator), the fenced JSON verdict block this skill emits in --compact mode is the structured return value of the skill's procedure β it is not a deliverable to the user, and emitting it does not terminate the orchestrator's turn. The same agent that ran this skill must immediately issue the next tool call dictated by the orchestrator's flow (an orchestrator that surfaces a per-callee guidance bullet names the specific next action there). Do not insert a prose summary, an acknowledgment, or a "shall I proceed?" sentence between the JSON verdict and the next tool call. Only one fenced JSON block β the verdict block β appears in the response, so callers can locate it unambiguously. The skill's own procedure is over; the orchestrator's procedure continues without pause.
This directive applies specifically to --compact mode. Other modes (Full Extraction, Update, Restructure, Conversation, Conversation Candidate Apply, Realign, PR Review) produce prose reports rather than fenced JSON verdicts and are not subject to this contract.
If a ~/.claude/stop-hook-git-check.sh style Stop hook is registered, it may fire mid-dispatch with uncommitted-change feedback. This is a known structural conflict between non-interactive orchestrator flows and per-turn hooks. Treat each fire as spurious: ignore the prose and continue the prescribed flow; per-file flow runs that complete the orchestrator's sub-step boundaries are the canonical completion signal.