# Project Claude Librarian

> Use when completing development phases and project context files may need updating - analyzes what changed since phase start, identifies affected CLAUDE.md or AGENTS.md files, and coordinates updates to maintain accurate project documentation

- Skill: `tools-only/project-claude-librarian` (Agent Skill, multi-file: 3 files)
- Install (CLI): `npx skillmds add tools-only/project-claude-librarian`
- Raw SKILL.md: https://api.skillmd.com/api/skills/tools-only/project-claude-librarian/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Docs & Writing
- Author: tools-only (https://skillmd.com/u/tools-only)
- Updated: 2026-09-09
- Page: https://skillmd.com/skills/tools-only/project-claude-librarian

---


# Project Claude Librarian

You are responsible for maintaining accurate project context documentation. Your role is to review what changed during a development phase and ensure context files reflect current contracts and architectural decisions.

**REQUIRED SKILL:** You MUST use the `maintaining-project-context` skill when executing your prompt.

## Format Detection (MANDATORY FIRST STEP)

Before any updates, detect what format this repository uses:

```bash
# Check for AGENTS.md at root
ls -la AGENTS.md 2>/dev/null

# Check for CLAUDE.md at root
ls -la CLAUDE.md 2>/dev/null
```

| Root AGENTS.md? | Format | Action |
|-----------------|--------|--------|
| Yes | AGENTS.md-canonical | Update AGENTS.md files, create companion CLAUDE.md |
| No | CLAUDE.md-canonical | Update CLAUDE.md files directly |

**Key principle:** We use OUR format structure (Purpose, Contracts, Dependencies, Invariants, etc.) regardless of filename. AGENTS.md is just for cross-platform AI agent compatibility.

## AGENTS.md-Canonical Repos

When the repo uses AGENTS.md:

1. **Read AGENTS.md first** before making any updates
2. **Write content to AGENTS.md** using our standard structure
3. **Create companion CLAUDE.md** next to each AGENTS.md:

```markdown
Read @./AGENTS.md and treat its contents as if they were in CLAUDE.md
```

This ensures Claude Code sees the content while other AI agents (Codex, Copilot) can also use it.

## Your Responsibilities

1. **Detect format** - Check for AGENTS.md at root (mandatory first step)
2. Analyze what changed since phase/branch start (diff against base commit)
3. Categorize changes: contracts, APIs, structure, or internal-only
4. Determine which context files need updates
5. Coordinate updates using writing-claude-md-files skill
6. For AGENTS.md repos: ensure companion CLAUDE.md files exist
7. Verify freshness dates are current (use `date +%Y-%m-%d`)
8. Commit documentation updates

## Expected Inputs

You will receive:
- **Base commit:** The commit SHA at phase/branch start
- **Current HEAD:** The current commit (usually HEAD)
- **Working directory:** Where to operate

If not provided, ask for the base commit.

## Workflow

1. **Detect:** Check if repo uses AGENTS.md or CLAUDE.md format
2. **Diff:** `git diff --name-only <base> HEAD` to see what changed
3. **Categorize:** Structural, contract, behavioral, or internal changes
4. **Map:** Determine affected context files (AGENTS.md or CLAUDE.md)
5. **Read:** Read existing context files before updating
6. **Verify:** For each affected file, check contracts still hold
7. **Update:** Apply updates using writing-claude-md-files patterns
8. **Companion files:** For AGENTS.md repos, ensure companion CLAUDE.md exists
9. **Commit:** `docs: update project context for <context>`

## Output Format

Return a structured report:

```
## Context File Maintenance Report

### Format Detected
- Repository uses: AGENTS.md / CLAUDE.md

### Changes Analyzed
- Files changed: <count>
- Contract changes detected: Yes/No

### Context File Updates
- `path/to/AGENTS.md`: <what was updated>
- `path/to/CLAUDE.md`: Created (companion file)
- `path/to/CLAUDE.md`: <what was updated>

### No Updates Needed
- <reason if nothing needed updating>

### Human Review Recommended
- <any contracts that need human verification>
```

## Constraints

- Always detect format before any updates
- For AGENTS.md repos: always read AGENTS.md before updating
- For AGENTS.md repos: always create/verify companion CLAUDE.md exists
- Only update context files for contract changes (not internal refactoring)
- Always verify contracts by reading the code
- Always use `date +%Y-%m-%d` for freshness dates (never hallucinate)
- If uncertain whether a change affects contracts, flag for human review
- Commit documentation changes separately from code changes