Maintaining Project Context

REQUIRED SUB-SKILL: Use ed3d-extending-claude:writing-claude-md-files for all context file creation and updates.

Core Principle

Context files (CLAUDE.md or AGENTS.md) document contracts and architectural intent. When code changes contracts, the documentation must update. Stale documentation is worse than no documentation.

Trigger: End of development phase, branch completion, or any work that changed contracts, APIs, or domain structure.

Format Detection (MANDATORY FIRST STEP)

Before any updates, detect what format this repository uses:

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:

• Read AGENTS.md first before making any updates

• Write content to AGENTS.md using our standard structure

• Create companion CLAUDE.md next to each AGENTS.md with exactly this content:

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

When to Update Context Files

Change Type Update Required? What to Update

New domain/module Yes Create domain context file

API/interface change Yes Contracts section

Architectural decision Yes Key Decisions section

Invariant change Yes Invariants section

Dependency change Yes Dependencies section

Bug fix (no contract change) No

Refactor (same behavior) No

Test additions No

The Process

Step 1: Identify What Changed

Diff against the base (branch start or phase start):

Get changed files

git diff --name-only <base-sha> HEAD

Get detailed changes

git diff <base-sha> HEAD --stat

Categorize changes:

• Structural: New directories, moved files

• Contract: Changed exports, interfaces, public APIs

• Behavioral: Changed invariants, guarantees

• Internal: Implementation details only

Step 2: Map Changes to Context Files

For each significant change, determine which context file should document it:

Change Location Context File Location

Project-wide pattern Root context file

New domain <domain>/ context file (create)

Existing domain contract <domain>/ context file (update)

Cross-domain dependency Both affected domains

Hierarchy rule: Information belongs at the lowest level where it applies. Domain-specific contracts go in domain files, not root.

For AGENTS.md-canonical repos: When creating new domain context files, create both AGENTS.md (with content) and CLAUDE.md (companion pointer).

Step 3: Verify Contracts Still Hold

For each affected context file, verify:

• Contracts section: Do exposes/guarantees/expects match current code?

• Dependencies section: Are uses/used-by/boundary accurate?

• Invariants section: Are all invariants still enforced?

• Key Decisions section: Any new decisions to document?

Find domain's public exports

grep -r "export" <domain>/index.ts

Find domain's imports (dependencies)

grep -r "from '.." <domain>/

Step 4: Update or Create Context Files

For updates:

• Read existing file first (especially for AGENTS.md)

• Update freshness date via date +%Y-%m-%d

• Update affected sections

• Remove stale content

• Verify under token budget (<100 lines for domain files)

For new domains (CLAUDE.md-canonical repos):

• Create <domain>/CLAUDE.md using template from writing-claude-md-files

• Document purpose, contracts, dependencies, invariants

• Set freshness date

For new domains (AGENTS.md-canonical repos):

• Create <domain>/AGENTS.md using template from writing-claude-md-files

• Document purpose, contracts, dependencies, invariants

• Set freshness date

• Create companion <domain>/CLAUDE.md : Read @./AGENTS.md and treat its contents as if they were in CLAUDE.md

Step 5: Commit Documentation Updates

git add <affected CLAUDE.md files> git commit -m "docs: update project context for <branch-name>"

Decision Tree

Has code changed? ├─ No → Skip (nothing to update) └─ Yes → Detect format first (AGENTS.md at root?) │ └─ What changed? ├─ Only tests/internal details → Skip └─ Contracts/APIs/structure → Continue │ ├─ New domain created? │ ├─ AGENTS.md repo → Create AGENTS.md + companion CLAUDE.md │ └─ CLAUDE.md repo → Create CLAUDE.md │ ├─ Existing domain changed? │ └─ Update domain context file (read first!) │ └─ Project-wide pattern changed? └─ Update root context file

Quick Reference

Always update when:

• New public exports added

• Interface signatures changed

• Invariants added/removed

• Dependencies changed

• Architectural decisions made

Never update for:

• Internal refactoring

• Bug fixes that don't change contracts

• Test file changes

• Comment/documentation-only changes

Common Mistakes

Mistake Fix

Updating for every change Only update for contract changes

Forgetting freshness date Always use date +%Y-%m-%d

Documenting implementation Document contracts and intent

Putting domain info in root Use domain context files for domain contracts

Skipping verification Read the code, confirm contracts hold

Skipping format detection Always check for AGENTS.md first

Writing AGENTS.md without reading Always read existing content before updating

Forgetting companion CLAUDE.md AGENTS.md repos need both files

Integration Points

Called by:

• project-claude-librarian agent - Uses this skill to coordinate updates

• executing-an-implementation-plan (Step 5b) - After all tasks complete

• finishing-a-development-branch (Step 4b) - Before merge/PR

Uses:

• writing-claude-md-files - For actual context file creation/updates (works for both CLAUDE.md and AGENTS.md)