# Align Documentation

> Sync documentation with code after implementation changes. Keep AGENTS.md, API docs, and architecture docs accurate by mapping code changes to their documentation impact.

## When to Use

- After completing a feature implementation (post-merge or post-commit)
- After fixing a bug that changes observable behavior
- After a refactoring that renames, moves, or restructures code
- When detect-doc-drift reports findings that need fixing
- When `on_post_feature` or `on_post_merge` triggers fire
- NOT during active development — wait until the code is stable
- NOT for creating documentation for a brand-new project (use validate-context-engineering for initial setup)
- NOT for fixing code — this skill only changes documentation

## Process

### Phase 1: Detect — Identify What Changed

1. **Run `git diff` against the appropriate baseline.** Choose the baseline based on context:
   - After a feature: diff against the branch point (`git diff main...HEAD`)
   - After a bug fix: diff against the commit before the fix
   - After a refactoring: diff against the commit before refactoring started
   - Periodic sync: diff against the last documentation sync commit

2. **Extract the list of changed files.** For each changed file, note:
   - File path (current and previous if renamed/moved)
   - Nature of change (added, modified, deleted, renamed)
   - Changed exports (new, removed, renamed, signature changed)
   - Changed behavior (different return values, new error types, new side effects)

3. **Run `harness check-docs`** to identify any documentation that already has broken references due to the changes.

### Phase 2: Map — Connect Code Changes to Documentation

For each changed file, identify all documentation that references it:

**AGENTS.md sections:**

- Knowledge map entries that reference the file path
- Architecture descriptions that mention the module
- Constraint documentation that references the file's layer or patterns
- Onboarding guides that walk through the file

**API documentation:**

- JSDoc/TSDoc comments in the changed files themselves
- Generated API doc pages that pull from the changed files
- README examples that demonstrate the changed functions
- Tutorial or guide pages that use the changed code

**Architecture documentation:**

- Diagrams that include the changed module
- Data flow descriptions that reference the changed functions
- Layer descriptions that list the changed file
- Dependency documentation that references the changed imports

**Inline code comments:**

- Comments in OTHER files that reference the changed file or function
- TODO comments that reference the changed behavior
- Workaround comments that may no longer apply after the change

### Phase 3: Generate — Draft Documentation Updates

For each affected documentation location:

1. **Draft the specific text change.** Show the old text and the new text. Keep the existing style and tone — documentation updates should be invisible in terms of voice.

2. **Preserve context.** When updating a section, do not just change the specific reference — read the surrounding paragraph and ensure it still makes sense. A renamed function may require updating the explanatory text around it, not just the function name.

3. **Handle deletions carefully.** When code is deleted, do not just delete the documentation reference. Consider whether the section should be removed entirely, replaced with information about the replacement, or noted as deprecated.

4. **Add new sections when needed.** If a new module was added, draft a complete documentation section following the existing AGENTS.md structure and style.

### Phase 4: Validate — Verify Documentation Accuracy

1. **Run `harness check-docs`** to verify all links and references resolve correctly after the updates.

2. **Cross-check each update against the actual code.** Read the updated documentation and verify every claim by looking at the code. Documentation that is wrong is worse than documentation that is missing.

3. **Verify no orphaned references remain.** Search documentation files for any remaining references to old names, old paths, or deleted features.

4. **Run `harness fix-drift`** to catch any remaining simple drift issues that manual review missed.

5. **Commit the documentation update.** Use a commit message that references the original change: "docs: update AGENTS.md for notification service refactoring" or "docs: sync API docs after auth module rename."

## What to Update

### AGENTS.md Knowledge Map

- File paths and module names (renamed or moved files)
- Module purpose descriptions (changed responsibilities)
- Constraint descriptions (new or changed rules)
- Relationship descriptions (new or changed dependencies)
- Gotcha sections (resolved gotchas, new gotchas)

### Inline Code Comments

- Function/class doc comments in the changed files (JSDoc, TSDoc)
- Comments in other files that reference the changed code
- TODO comments that reference completed or changed work
- Workaround comments for issues that may now be resolved

### Documentation Pages (docs/)

- API reference pages that describe changed functions
- Architecture pages that diagram changed modules
- Tutorial and guide pages that demonstrate changed code
- Getting-started guides if entry points changed
- Changelog entries for user-facing changes

## Harness Integration

- **`harness check-docs`** — Run before and after updates. Identifies broken references and validates that all documentation links resolve.
- **`harness fix-drift`** — Auto-fix simple drift issues (broken file paths, renamed references) after manual review confirms correctness.
- **`harness fix-drift --json`** — Machine-readable output for tracking what was auto-fixed.
- **`harness validate`** — Run after documentation changes to verify overall project health is maintained.

## Success Criteria

- `harness check-docs` passes with zero errors after documentation updates
- Every code change from the diff has been mapped to its documentation impact
- All file paths in documentation match current file locations
- All function/class names in documentation match current code
- All behavioral descriptions in documentation match current implementation
- Documentation updates are committed with clear references to the triggering code change
- No orphaned references to old names, paths, or deleted features remain

## Examples

### Example: Syncing docs after a module rename

**Code change:** `src/services/mailer.ts` renamed to `src/services/email-service.ts`. Functions `sendMail()` and `formatMailBody()` renamed to `sendEmail()` and `formatEmailBody()`.

**Documentation impact map:**

```
AGENTS.md:34      — "mailer.ts handles email delivery" → update path and description
AGENTS.md:78      — "Use sendMail() for all outbound email" → update function name
docs/api.md:156   — sendMail() API reference → update name and import path
docs/arch.md:45   — architecture diagram lists "mailer" → update to "email-service"
src/controllers/user-controller.ts:12 — comment "// delegates to mailer" → update
```

**Updates applied:**

- AGENTS.md: updated two sections with new file path and function names
- docs/api.md: updated function reference and import example
- docs/arch.md: updated module name in architecture description
- src/controllers/user-controller.ts: updated inline comment

**Validation:** `harness check-docs` passes. All references resolve. Commit: "docs: sync documentation after mailer rename to email-service"

### Example: Syncing docs after adding error handling

**Code change:** `createUser()` in `src/services/user-service.ts` now throws `ValidationError` instead of returning `null` on invalid input.

**Documentation impact map:**

```
docs/api.md:89    — "Returns null if validation fails" → update to describe thrown error
AGENTS.md:52      — No mention of error handling → add note about ValidationError
src/services/user-service.ts:15 — JSDoc @returns tag → update, add @throws tag
```

**Updates applied:**

- docs/api.md: replaced "returns null" with "throws ValidationError" and added example
- AGENTS.md: added note about error handling pattern in user-service section
- JSDoc: updated @returns, added @throws ValidationError

**Validation:** `harness check-docs` passes. Commit: "docs: update documentation for createUser error handling change"

## Escalation

- **When you cannot determine what documentation is affected:** Run `harness check-docs` for automated detection. For manual analysis, search all `.md` files and code comments for the old name/path. If the change is large, use detect-doc-drift first to get a complete inventory.
- **When documentation is in an external system (wiki, Confluence):** Document the needed change and flag it for manual update. Include the specific text that needs changing and the correct replacement.
- **When the code change is so large that documentation needs a rewrite:** Break the documentation update into sections. Update one section at a time, validating after each. Do not attempt a full rewrite in one pass.
- **When you disagree with the existing documentation style:** Follow the existing style. Documentation alignment is about accuracy, not style improvement. Style changes should be a separate, deliberate effort.
