Apply Rules Skill | Agent Skills

Apply Rules

Applies organization-wide rules (produced by merge-rules) to the current project. Detects the project's tech stack, selects relevant rules, merges them with existing extract-rules output, cleans up promoted patterns from .local.md files, and ensures the final structure conforms to the extract-rules/merge-rules convention.

Usage

/apply-rules <source>                  # Apply from GitHub URL or local path
/apply-rules                           # Apply using config file
/apply-rules --config <path>           # Apply using specified config file
/apply-rules --dry-run                 # Show what would change without writing
/apply-rules --dry-run <source>        # Dry run with specified source

<source> points directly to the rules directory (merge-rules or extract-rules output):

GitHub: https://github.com/org/repo/tree/main/.claude/rules
Local: ~/org-rules/.claude/rules

Configuration

Config file search order:

--config <path> argument
.claude/apply-rules.local.md (project-level)
~/.claude/apply-rules.local.md (user-level)

File format: YAML frontmatter only (no markdown body), same convention as extract-rules.local.md and merge-rules.local.md.

---
# Rules directory (GitHub URL or local path)
# GitHub: https://github.com/org/repo/tree/main/.claude/rules
# Local: ~/org-rules/.claude/rules
source: https://github.com/org/repo/tree/main/.claude/rules

# Alternative: specify GitHub source components separately
# (useful when branch name contains "/" or for tags/SHAs)
# source_repo: org/repo
# source_ref: feature/rules-v2
# source_path: .claude/rules

# Output directory in target project (default: .claude/rules/)
output_dir: .claude/rules/

# Auto-detect which rules to apply (default: true)
# When false, applies ALL rules from source
auto_detect: true

# Explicitly include rules even if not auto-detected
include: []
# Example: [languages/typescript, integrations/rails-inertia]

# Explicitly exclude rules even if auto-detected
exclude: []
# Example: [frameworks/rails-views]

# Report language (default: ja)
language: ja
---

CLI argument <source> overrides the config's source field.

Processing Flow

Step 1: Load Configuration

If CLI <source> argument provided, use it (overrides config source)
Search for config file (see search order above)
Parse YAML frontmatter, apply defaults for omitted fields
- language resolution order: Skill config → Claude Code settings (~/.claude/settings.json → language field) → default ja
Validate:
- source must be specified (via CLI argument or config file)
- If neither: Error "No source specified. Provide a GitHub URL or local path as argument, or create .claude/apply-rules.local.md with a source: field."

Step 2: Fetch Source Rules

If source is a local path:

Expand ~ and resolve to absolute path
Verify directory exists and contains rule files (.md)
Read directly from this location

If source is a GitHub URL:

Parse URL to extract owner, repo, branch, and path:

https://github.com/{owner}/{repo}/tree/{branch}/{path}
Example: https://github.com/org/repo/tree/main/.claude/rules → owner: org, repo: repo, branch: main, path: .claude/rules

Note on ambiguous refs: Branch names may contain / (e.g., feature/rules-v2), and refs can also be tags or SHAs. Simple URL splitting cannot reliably separate ref from path. To handle this robustly:

Try resolving ref candidates from longest prefix first using gh api repos/{owner}/{repo}/git/ref/{candidate}
Alternatively, the user can specify components separately in the config:
```
source_repo: org/repo
source_ref: feature/rules-v2
source_path: .claude/rules
```
When these fields are present, they take precedence over URL parsing.
For the common case (branch = main or master), simple URL parsing works.

Fetch using gh api:

Verify authentication: gh auth status
Create temp directory: mktemp -d
List top-level directory contents:
```
gh api repos/{owner}/{repo}/contents/{path}?ref={branch}
```
For each entry with type: "dir", recursively fetch subdirectory contents:
```
gh api repos/{owner}/{repo}/contents/{path}/{subdir}?ref={branch}
```
This dynamically discovers all categories (not limited to languages/, frameworks/, integrations/).
For each .md file found, fetch content and decode:
```
gh api repos/{owner}/{repo}/contents/{file_path}?ref={branch} --jq '.content | @base64d'
```
Save to tmpdir preserving directory structure
Temp dir is cleaned up in Step 8

Inventory source files:

Glob for **/*.md and **/*.examples.md under the source rules directory
Skip project.md and project.examples.md (inherently project-specific)
Skip .local.md files (merge-rules output should not contain these, but handle gracefully)
Parse each file: extract YAML frontmatter (paths:) and body sections

Step 3: Detect Target Project Tech Stack

Analyze the current working directory to determine which source rules are relevant. Detection is best-effort, based on dependency files (e.g., Gemfile, package.json) and project directory structure (e.g., app/controllers/).

Read references/detection-heuristics.md for the full detection table mapping indicators to rule files. If the source contains rule files not covered in the table, use AI judgment to match them against the project's dependencies and file structure.

Apply overrides:

Add include: entries to the detected set
Remove exclude: entries from the detected set
If auto_detect: false: start with ALL source rules, then apply exclude only

Step 4: Filter and Propose

If auto_detect: false: Apply ALL source rules (minus exclude entries). Skip the proposal step entirely — no integration proposals or skipped rules. Proceed directly to Step 5.

If auto_detect: true (default):

Auto-matched rules: Rules that match detected tech stack → apply automatically
Integration proposals: For integrations NOT detected in the project but related to a detected framework (e.g., source has integrations/rails-pundit but project doesn't use pundit), use AskUserQuestion to present them as a single list:
The following integration rules are available in the source but were not detected in your project. Which would you like to apply?
1. integrations/rails-pundit — Authorization library Pundit rules
2. integrations/rails-good-job — Job queue GoodJob rules
Options: all / none / specify by number (e.g. "1" or "1,2")
Apply only those the user approves.
Skipped rules: Rules for tech not detected and not in related frameworks → skip, list in report

Step 5: Inventory Existing Target Rules

Check if {output_dir}/ exists in the target project
If exists, read all files: .md, .local.md, .examples.md
Parse frontmatter and body sections for each
Categorize files the same way as source files
Detect hybrid format: If any target .md file contains ## Project-specific patterns (hybrid format from extract-rules split_output: false), note this. The merge step will convert hybrid to split format because the split format (separate .md and .local.md) is the standard expected by both extract-rules and merge-rules, and mixing formats causes confusion when rules flow back through the pipeline. Note: source files from merge-rules should not contain ## Project-specific patterns (promoted patterns are converted to Principles format)

Step 5.5: Normalize File Names

Before merging, align target file names with source (canonical) names. This prevents duplicate files for the same concept (e.g., rails-controller.md vs rails-controllers.md).

Compare target file names against source file names within the same category
Detect naming variants: singular/plural (controller/controllers), minor differences for the same concept
If renames are detected, use AskUserQuestion to confirm:
The following target files will be renamed to match source (canonical) names:
1. frameworks/rails-controller.md → frameworks/rails-controllers.md
Options: all / none / specify by number
Apply approved renames and report in the summary

Step 6: Merge Rules

For each filtered source rule file, determine the merge action:

6a. Merge .md files (Principles):

Case: No existing .md

Copy source .md as-is (source from merge-rules contains only ## Principles)

Case: Existing .md exists

paths: frontmatter: Union of all path patterns, deduplicate
Hybrid → split conversion: If existing .md contains ## Project-specific patterns (hybrid format):
- Extract that section and move to .local.md (create if not exists, append if exists)
- Remove the section from .md, keeping only ## Principles
## Principles:
- Match principles by name (text before parenthetical hints)
- Source principle not in target → Add
- Target principle not in source → Keep (project may have added its own)
- Same principle, same meaning but different hints → Union hints from both
- Same principle name but different content → Collect all conflicts, then use AskUserQuestion to present them together:
  The following principles differ between org rules and project rules:
  
  1. Immutability (in languages/ruby.md)
  - Org: Immutability (spread, map/filter/reduce, const)
  - Project: Immutability (freeze, deep clone, readonly)
  2. Error handling (in frameworks/rails.md)
  - Org: Error handling (rescue, custom exceptions)
  - Project: Error handling (rescue, retry, circuit breaker)
  For each, choose: (a) Adopt org rule / (b) Keep project rule / (c) Keep both Example: "1a, 2c" or "all a"

6b. Clean up promoted patterns from .local.md files:

.local.md files contain project-specific patterns discovered by extract-rules. When org rules promote a pattern to a Principle, the original pattern in .local.md becomes redundant. apply-rules cleans up these duplicates while preserving genuinely project-specific patterns.

apply-rules does not write new patterns to .local.md
Cross-format duplicate removal: After merging Principles in Step 6a, scan target .local.md for patterns whose description matches a Principle name now present in the corresponding .md (e.g., `useAuth() → { user, login, logout }` - auth hook interface is a duplicate of Auth hook interface (useAuth) in ## Principles). Use AI judgment for semantic equivalence (case-insensitive, synonyms)
Remove matched patterns from .local.md
If .local.md becomes empty after removal, delete the file
Preserve all patterns that do not match any Principle (genuinely project-specific)

6c. Merge .examples.md files:

Case: No existing .examples.md

Copy source .examples.md as-is (source from merge-rules contains only ## Principles Examples)

Case: Existing .examples.md exists

## Principles Examples: Add examples from source for principles not already covered in target
## Project-specific Examples (target only): Remove examples whose ### title corresponds to patterns removed from .local.md in Step 6b. Preserve all other existing entries

6d. Ensure ## Examples reference:

Every .md and .local.md that still exists and has a corresponding .examples.md must end with:
```
## Examples
When in doubt: ./<name>.examples.md
```
If a .local.md was deleted in Step 6b (became empty), no reference is needed

Step 7: Structure Conformance Check + Auto-cleanup

Scan output_dir for files that don't conform to extract-rules/merge-rules convention:

Valid patterns:

{category}/{name}.md
{category}/{name}.local.md
{category}/{name}.examples.md
project.md
project.examples.md

Valid categories: languages/, frameworks/, integrations/

Non-conforming file handling:

Read the non-conforming file and analyze its content
Determine the appropriate conforming file(s) to migrate rules into (based on category, content, and paths: hints)
Use AskUserQuestion to present the migration plan as a single list for confirmation:
The following non-conforming files were detected. Migrate their rules to conforming files and delete them?
1. frameworks/old-custom-rules.md → migrate to frameworks/rails.md
2. ruby-rules.md → migrate to languages/ruby.md
3. project.rules.md → migrate to project.md (project file — confirm individually)
Options: all / none / specify by number (e.g. "1,2")

Note: project.* files are excluded from "all". Specify them individually by number.
User approval → merge rules into conforming file(s) and delete non-conforming files
Report all migrations and deletions

Step 8: Cleanup

If source was a GitHub URL, remove the temp directory: rm -rf <tmpdir>

Step 9: Report Summary

Display report. Report headers are always in English, content in the configured language.

# Apply Rules Report

## Source
- https://github.com/org/repo/tree/main/.claude/rules (15 rule files)

## Target Project Detection
- Languages: ruby
- Frameworks: rails, rails-controllers, rails-models, rails-views
- Integrations: rails-devise, rails-pundit

## Applied Rules
| File | Action | Principles |
|------|--------|------------|
| languages/ruby.md | Merged | +3 added, 7 kept |
| frameworks/rails.md | Created | 13 |
| frameworks/rails-controllers.md | Created | 5 |
| integrations/rails-devise.md | Merged | +1 added |

## Promoted Pattern Cleanup
- languages/ruby.local.md: removed 1 pattern (now in Principles)
- frameworks/rails.local.md: no duplicates found

## Preserved
- languages/ruby.local.md (2 remaining patterns)
- frameworks/rails.local.md (3 patterns, untouched)

## User-approved Integrations
- integrations/rails-pundit (not detected, approved by user)

## Skipped (not relevant to project)
- languages/typescript.md
- frameworks/react.md
- frameworks/nextjs.md
- integrations/rails-stripe.md

## Structure Cleanup
- frameworks/old-custom.md → rules migrated to frameworks/rails.md → deleted

## Conflicts (resolved by user)
- languages/ruby.md: "Immutability" → user chose: Keep both

Conflict Handling

Summary of user-confirmation points and automatic actions:

| Situation | Action | |-----------|--------| | Principle in source, not in target | Auto-add | | Principle in target, not in source | Auto-keep | | Same principle, different hints | Auto-union hints | | Same principle name, different content | AskUserQuestion: collect all conflicts, present together (adopt org / keep project / keep both) | | Non-conforming file detected | AskUserQuestion: present migration plan as single list for confirmation | | project.* non-conforming file | Excluded from "all" — must be specified individually by number | | Target file name differs from source canonical name | AskUserQuestion: confirm renames (all / none / specify) | | Undetected integration rule (related framework) | AskUserQuestion: present as single list for approval (all / none / specify) | | .local.md pattern matching a Principle | Auto-remove from .local.md (cross-format duplicate cleanup) | | .local.md pattern not matching any Principle | Preserved | | ## Project-specific Examples for removed pattern | Auto-remove | | ## Project-specific Examples for remaining pattern | Preserved |

Agent Skills: Apply Rules

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