Living Docs

Generate documentation driven by actual code changes. Every document traces to specific commits and files. When code changes, docs change.

Language policy: Generate all documentation in English. Include Spanish translations in the aliases frontmatter field.

Folder Structure

All generated docs live under ${GIT_REPO_ROOT}/docs/ (relative to the repository root). Create this structure if it doesn't exist:

docs/
├── components/          # Component Docs (services, apps, libraries)
│   ├── auth-service.md
│   ├── user-service.md
│   └── shared-utils.md
├── changelogs/          # Changelogs and release notes
│   ├── changelog-auth-service-2026-02-13.md
│   └── changelog-global-2026-02-13.md
├── adrs/                # Architecture Decision Records
│   ├── adr-001-redis-caching.md
│   └── adr-002-event-driven-auth.md
├── runbooks/            # Runbooks and SOPs
│   ├── runbook-deploy-auth-service.md
│   └── runbook-database-migration.md
└── index.md             # Auto-generated index linking all docs

File Naming Conventions

Index File

After generating or updating docs, update docs/index.md with links to all docs:

# Documentation Index

> Auto-generated. Last updated: YYYY-MM-DD

## Components
- [[auth-service]] — Authentication and authorization service
- [[shared-utils]] — Shared utility library

## Recent Changelogs
- [[changelog-auth-service-2026-02-13]] — Added OAuth2 support

## Architecture Decisions
- [[adr-001-redis-caching]] — Accepted

## Runbooks
- [[runbook-deploy-auth-service]] — Deployment procedure

Workflow

1. Gather context     → Determine diff scope
2. Extract diff data  → Run extract-diff.sh or git commands
3. Classify changes   → Identify what matters (see references/analysis-patterns.md)
4. Select templates   → Pick doc types (see references/templates.md)
5. Generate docs      → Write markdown with full YAML frontmatter
6. Verify output      → Cross-check generated docs against diff
7. Present summary    → Show what was generated and why

Step 1: Gather Context

Determine from the user's message (ask only if not inferrable):

• •Diff scope: Branch comparison (e.g., feature/X vs Develop) or last N commits?
• •Existing docs: Any docs to update rather than create from scratch?

Defaults (when not specified):

• •Diff scope: Current branch vs default branch (auto-detected from repo)
• •Output path: Always ${GIT_REPO_ROOT}/docs/ (using the folder structure above)
• •Existing docs: Search ${GIT_REPO_ROOT}/docs/ for matching filenames before creating new docs

Step 2: Extract Diff Data

Run the extraction script from this skill's directory:

# Branch comparison (auto-detects default branch)
bash <this-skill-path>/scripts/extract-diff.sh <repo-path> --branch <target>

# Last N commits
bash <this-skill-path>/scripts/extract-diff.sh <repo-path> --commits 20

# Filtered by path (for monorepos)
bash <this-skill-path>/scripts/extract-diff.sh <repo-path> --branch Develop --path services/auth/

For multi-repo workspaces, run per repository.

Large Diff Strategy

When the diff is large (100+ files changed or output exceeds ~50KB):

1. •Start with --stat only — Use the file list and change counts to plan
2. •Read full diff only for high-impact files — APIs, schemas, configs, contracts, new files
3. •Read only changed hunks for medium-impact files — Business logic, services
4. •Skip full diff for low-impact files — Tests, formatting, comments
5. •Split by directory — If still too large, analyze one component/service at a time

Step 3: Classify Changes

Read references/analysis-patterns.md for the full classification guide.

Priority: High-impact changes (new components, public API changes, business logic changes, schema migrations, new dependencies, infra changes) are always documented. Medium-impact (internal refactors, test changes) only if significant. Low-impact (formatting, comments, patch bumps) are skipped.

Key distinctions (from analysis-patterns.md):

• •Business logic vs refactor: Did test expectations change? → business logic. Same tests pass? → refactor.
• •Interface exposure: External (public API) > Inter-component (shared packages) > Internal (same module). Document proportionally.

Map each significant change to doc types:

Step 4: Select and Fill Templates

Read references/templates.md for all templates and the frontmatter schema.

Frontmatter rules:

• •ALWAYS include all required fields: aliases, type, layer, status, owner, tech_stack, last_updated, source_branch, commit_range
• •Use [[wiki-links]] for owner, tech_stack, and cross-references
• •Set last_updated to today's date
• •Set source_branch and commit_range from the actual diff
• •Set status honestly: active, debt, zombie, or gap
• •Populate aliases with English keywords + Spanish equivalents
• •Infer owner and tech_stack using the heuristics in templates.md → "Inferring Frontmatter from Diffs"
• •Omit template sections that don't apply (e.g., don't include "Events Published" for a REST-only service)

Step 5: Generate Docs

Write docs to the folder structure defined above.

Updating existing docs: Read first, preserve frontmatter structure, update last_updated and commit_range, modify only affected sections, append to "Recent Changes".

Merge Strategy for Incremental Updates

When a doc already exists:

Step 6: Verify Output

Before presenting to the user, cross-check:

• • Every endpoint/export mentioned in docs exists in the diff or codebase
• • All frontmatter required fields are populated (no empty or placeholder values except owner: "[[TBD]]")
• • File paths referenced in "Key Files" actually exist
• • Breaking changes flagged in Changelog match actual contract changes in the diff
• • No duplicate docs (check existing files before creating new ones)

Step 7: Present Summary

Show the user what was generated:

## Documentation Generated

| File | Type | Reason |
|------|------|--------|
| docs/components/auth-service.md | Component Doc | New endpoints in routes/users.ts |
| docs/changelogs/changelog-auth-2026-02-13.md | Changelog | 12 commits with 3 features, 2 fixes |

### Key Changes Documented
- [bullets]

### Skipped (Low Impact)
- [what and why]

Always update ${GIT_REPO_ROOT}/docs/index.md with links to all generated docs (for multi-repo workspaces, do this per repository).

Quality Rules

• •No fluff: Every sentence carries information. Cut filler.
• •Trace to code: Every claim references a file, commit, or config.
• •Tables over prose: For endpoints, env vars, dependencies — always tables.
• •Be honest: If the diff reveals tech debt, set status: debt. Living docs tell the truth.
• •Aliases matter: Include concept name, Spanish translation, common abbreviations.
• •Omit empty sections: Don't include template sections that have no content for this component.

Few-Shot Example

Input: Diff Summary

=== FILE STATS ===
 services/auth/src/routes/auth.ts   | 45 +++++++++--
 services/auth/src/services/oauth.ts | 120 ++++++++++++++++++++++++++++
 services/auth/src/types/auth.dto.ts |  15 ++++
 packages/shared-types/src/user.ts   |   8 ++--
 services/auth/package.json          |   2 +  (added passport-google-oauth20)
 services/auth/tests/oauth.test.ts   |  85 ++++++++++++++++++++

=== COMMIT LOG ===
a1b2c3d feat: add Google OAuth2 login flow
d4e5f6g feat: add OAuth callback handler
h7i8j9k fix: handle missing email in OAuth profile
l0m1n2o chore: add passport-google-oauth20 dependency

Output: Classification

1. •New OAuth service file (oauth.ts, 120 lines) → High impact, new feature → Component Doc update
2. •Route changes (auth.ts, 45 lines) → Public API change → Component Doc + Changelog
3. •Shared types change (packages/shared-types/user.ts) → Inter-component interface → Component Doc + flag consumers
4. •New major dependency (passport-google-oauth20) → ADR candidate
5. •New tests with different expectations → Confirms business logic change, not refactor

Output: Generated Docs

• •docs/components/auth-service.md — Updated: added OAuth endpoints, new dependency, new key files
• •docs/changelogs/changelog-auth-2026-02-13.md — New: 2 features (OAuth login, callback handler), 1 fix
• •docs/adrs/adr-003-google-oauth.md — New: Decision to use passport-google-oauth20 for social login
• •docs/components/shared-types.md — Updated: flag that UserDTO interface changed (consumed by 2 services)

Resources

• •scripts/extract-diff.sh — Extract structured diff data (file stats, commit log, full diff)
• •references/templates.md — All doc templates with frontmatter schema
• •references/analysis-patterns.md — How to classify changes from diffs