Doc Sync

Maintains the CLAUDE.md navigation hierarchy and optional README.md architecture docs across a repository. This skill is self-contained and performs all documentation work directly.

Scope Resolution

Determine scope FIRST:

User Request	Scope
"sync docs" / "update documentation" / no specific path	REPOSITORY-WIDE
"sync docs in src/validator/"	DIRECTORY: src/validator/ and descendants
"update CLAUDE.md for parser.py"	FILE: single file's parent directory

For REPOSITORY-WIDE scope, perform a full audit. For narrower scopes, operate only within the specified boundary.

CLAUDE.md Format Specification

Index Format

Use tabular format with What and When columns:

## Files

| File        | What                           | When to read                              |
| ----------- | ------------------------------ | ----------------------------------------- |
| `cache.rs`  | LRU cache with O(1) operations | Implementing caching, debugging evictions |
| `errors.rs` | Error types and Result aliases | Adding error variants, handling failures  |

## Subdirectories

| Directory   | What                          | When to read                              |
| ----------- | ----------------------------- | ----------------------------------------- |
| `config/`   | Runtime configuration loading | Adding config options, modifying defaults |
| `handlers/` | HTTP request handlers         | Adding endpoints, modifying request flow  |

Column Guidelines

• File/Directory: Use backticks around names: cache.rs, config/
• What: Factual description of contents (nouns, not actions)
• When to read: Task-oriented triggers using action verbs (implementing, debugging, modifying, adding, understanding)
• At least one column must have content; empty cells use -

Trigger Quality Test

Given task "add a new validation rule", can an LLM scan the "When to read" column and identify the right file?

ROOT vs SUBDIRECTORY CLAUDE.md

ROOT CLAUDE.md:

# [Project Name]

[One sentence: what this is]

## Files

| File | What | When to read |
| ---- | ---- | ------------ |

## Subdirectories

| Directory | What | When to read |
| --------- | ---- | ------------ |

## Build

[Copy-pasteable command]

## Test

[Copy-pasteable command]

## Development

[Setup instructions, environment requirements, workflow notes]

SUBDIRECTORY CLAUDE.md:

# [directory-name]/

## Files

| File | What | When to read |
| ---- | ---- | ------------ |

## Subdirectories

| Directory | What | When to read |
| --------- | ---- | ------------ |

Critical constraint: Subdirectory CLAUDE.md files are PURE INDEX. No prose, no overview sections, no architectural explanations. Those belong in README.md.

README.md Specification

Creation Criteria (Invisible Knowledge Test)

Create README.md ONLY when the directory contains knowledge NOT visible from reading the code:

• Multiple components interact through non-obvious contracts or protocols
• Design tradeoffs were made that affect how code should be modified
• The directory's structure encodes domain knowledge (e.g., processing order matters)
• Failure modes or edge cases aren't apparent from reading individual files
• There are "rules" developers must follow that aren't enforced by the compiler/linter

DO NOT create README.md when:

• The directory is purely organizational (just groups related files)
• Code is self-explanatory with good function/module docs
• You'd be restating what CLAUDE.md index entries already convey

Content Test

For each sentence in README.md, ask: "Could a developer learn this by reading the source files?"

• If YES: delete the sentence
• If NO: keep it

README.md earns its tokens by providing INVISIBLE knowledge: the reasoning behind the code, not descriptions of the code.

README.md Structure

# [Component Name]

## Overview

[One paragraph: what problem this solves, high-level approach]

## Architecture

[How sub-components interact; data flow; key abstractions]

## Design Decisions

[Tradeoffs made and why; alternatives considered]

## Invariants

[Rules that must be maintained; constraints not enforced by code]

Workflow

Phase 1: Discovery

Map directories requiring CLAUDE.md verification:

# Find all directories (excluding .git, node_modules, __pycache__, etc.)
find . -type d \( -name .git -o -name node_modules -o -name __pycache__ -o -name .venv -o -name target -o -name dist -o -name build \) -prune -o -type d -print

For each directory in scope, record:

1. Does CLAUDE.md exist?
2. If yes, does it have the required table-based index structure?
3. What files/subdirectories exist that need indexing?

Phase 2: Audit

For each directory, check for drift and misplaced content:

<audit_check dir="[path]">
CLAUDE.md exists: [YES/NO]
Has table-based index: [YES/NO]
Files in directory: [list]
Files in index: [list]
Missing from index: [list]
Stale in index (file deleted): [list]
Triggers are task-oriented: [YES/NO/PARTIAL]
Contains misplaced content: [YES/NO] (architecture/design docs that belong in README.md)
README.md exists: [YES/NO]
README.md warranted: [YES/NO] (invisible knowledge present?)
</audit_check>

Phase 3: Content Migration

Critical: If CLAUDE.md contains content that does NOT belong there, migrate it:

Content that MUST be moved from CLAUDE.md to README.md:

• Architecture explanations or diagrams
• Design decision documentation
• Component interaction descriptions
• Overview sections with prose (in subdirectory CLAUDE.md files)
• Invariants or rules documentation
• Any "why" explanations beyond simple triggers

Migration process:

1. Identify misplaced content in CLAUDE.md
2. Create or update README.md with the architectural content
3. Strip CLAUDE.md down to pure index format
4. Add README.md to the CLAUDE.md index table

Phase 4: Index Updates

For each directory needing work:

Creating/Updating CLAUDE.md:

1. Use the appropriate template (ROOT or SUBDIRECTORY)
2. Populate tables with all files and subdirectories
3. Write "What" column: factual content description
4. Write "When to read" column: action-oriented triggers
5. If README.md exists, include it in the Files table

Creating README.md (only when warranted):

1. Verify invisible knowledge criteria are met
2. Document architecture, design decisions, invariants
3. Apply the content test: remove anything visible from code
4. Keep under ~500 tokens

Phase 5: Verification

After all updates complete, verify:

1. Every directory in scope has CLAUDE.md
2. All CLAUDE.md files use table-based index format
3. No drift remains (files <-> index entries match)
4. No misplaced content in CLAUDE.md (architecture docs moved to README.md)
5. README.md files are indexed in their parent CLAUDE.md
6. Subdirectory CLAUDE.md files contain no prose/overview sections

Output Format

## Doc Sync Report

### Scope: [REPOSITORY-WIDE | directory path]

### Changes Made
- CREATED: [list of new CLAUDE.md files]
- UPDATED: [list of modified CLAUDE.md files]
- MIGRATED: [list of content moved from CLAUDE.md to README.md]
- CREATED: [list of new README.md files]
- FLAGGED: [any issues requiring human decision]

### Verification
- Directories audited: [count]
- CLAUDE.md coverage: [count]/[total] (100%)
- Drift detected: [count] entries fixed
- Content migrations: [count] (architecture docs moved to README.md)
- README.md files: [count] (only where warranted)

Exclusions

DO NOT index:

• Generated files (dist/, build/, .generated., compiled outputs)
• Vendored dependencies (node_modules/, vendor/, third_party/)
• Git internals (.git/)
• IDE/editor configs (.idea/, .vscode/ unless project-specific settings)

DO index:

• Hidden config files that affect development (.eslintrc, .env.example, .gitignore)
• Test files and test directories
• Documentation files (including README.md)

Anti-Patterns

Index Anti-Patterns

Too vague (matches everything):

| `config/` | Configuration | Working with configuration |

Content description instead of trigger:

| `cache.rs` | Contains the LRU cache implementation | - |

Missing action verb:

| `parser.py` | Input parsing | Input parsing and format handling |

Correct Examples

| `cache.rs` | LRU cache with O(1) get/set | Implementing caching, debugging misses, tuning eviction |
| `config/` | YAML config parsing, env overrides | Adding config options, changing defaults, debugging config loading |

When NOT to Use This Skill

• Single file documentation (inline comments, docstrings) - handle directly
• Code comments - handle directly
• Function/module docstrings - handle directly
• This skill is for CLAUDE.md/README.md synchronization specifically

Reference

For additional trigger pattern examples, see references/trigger-patterns.md.