maintaining-project-context

name	maintaining-project-context
description	Use when completing development phases or branches to identify and update AGENTS.md files that may have become stale - analyzes what changed, determines affected contracts and documentation, and coordinates updates

Maintaining Project Context

REQUIRED SUB-SKILL: Use the writing-agents-md-files skill for all context file creation and updates.

Core Principle

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

We use OUR format structure (Purpose, Contracts, Dependencies, Invariants, etc.) — AGENTS.md is the cross-platform AI agent context filename.

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

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 AGENTS.md
New domain	<domain>/AGENTS.md (create)
Existing domain contract	<domain>/AGENTS.md (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.

Step 3: Verify Contracts Still Hold

For each affected context file, verify:

1. Contracts section: Do exposes/guarantees/expects match current code?
2. Dependencies section: Are uses/used-by/boundary accurate?
3. Invariants section: Are all invariants still enforced?
4. 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:

1. Read the existing file first
2. Update freshness date via date +%Y-%m-%d
3. Update affected sections
4. Remove stale content
5. Verify under token budget (<100 lines for domain files)

For new domains:

1. Create <domain>/AGENTS.md using the template from writing-agents-md-files
2. Document purpose, contracts, dependencies, invariants
3. Set freshness date

Step 5: Commit Documentation Updates

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

Decision Tree

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

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

Integration Points

Called by:

• ed3d-project-opencode-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-agents-md-files - For actual context file creation/updates