ADD AGENTS.md Skill v0.9.7

ADD AGENTS.md Skill v0.9.7

Generate a portable AGENTS.md at project root from the project's .add/ state. AGENTS.md is the cross-tool open standard for project-level agent instructions — any agent (Claude Code, Cursor, Codex CLI, Windsurf, Amp, Devin, Copilot) will read it on session start. Publishing one lets mixed-toolchain teams respect the same invariants without installing ADD.

This skill is the only way to regenerate AGENTS.md. A PostToolUse hook marks the file stale when source inputs change — the human triggers the actual regeneration.

Invocation

/add:agents-md               # default: --write
/add:agents-md --check       # drift detection, CI-friendly (exit 1 on drift)
/add:agents-md --merge       # prepend ADD block to an existing hand-curated AGENTS.md
/add:agents-md --import      # one-time absorption (same as --merge; explicit intent)
/add:agents-md --dry-run     # preview without writing (combines with any mode)

Pre-Flight Checks

1. Read .add/config.json

   • Load project.name, project.description
   • Load maturity.level (poc | alpha | beta | ga)
   • Load architecture.languages — determines whether the TDD Discipline section applies
   • Load environments.*.autoPromote — determines the autonomy ceiling summary

2. Read docs/prd.md if present

   • The H1 + first paragraph become the project identity section
   • If absent, fall back to project.description from config

3. Read .add/handoff.md if present

   • Extract the currently-active spec reference (first specs/*.md match in the file)
   • If absent, pick the most recently mutated specs/*.md by mtime

4. Check .add/agents-md.stale

   • If present, announce the stale state and the source files that changed since the last regen
   • This marker is removed automatically after a successful --write

5. Detect existing AGENTS.md

   • No file → default --write creates it fresh
   • File with ADD marker block → --write replaces managed content, preserves user-authored content outside the markers
   • File without ADD marker → --write aborts with guidance to use --merge or --import
   • Frontmatter (YAML / TOML / +++) at top is preserved verbatim

Generator Invocation

The skill delegates to scripts/generate-agents-md.py:

python3 scripts/generate-agents-md.py              # --write (default)
python3 scripts/generate-agents-md.py --check
python3 scripts/generate-agents-md.py --merge
python3 scripts/generate-agents-md.py --import
python3 scripts/generate-agents-md.py --dry-run

The script is deterministic given the same inputs plus --generated and --skill-version overrides (used by fixture tests for reproducibility). Normal invocation stamps the current UTC timestamp and reads the skill version from core/VERSION.

Marker Block Convention

<!-- ADD:MANAGED:START version=0.9.0 maturity=beta generated=2026-04-22T14:32:01Z -->
... ADD-owned content ...
<!-- ADD:MANAGED:END -->

• HTML comments — invisible in rendered markdown, durable across editors
• Opening marker carries skill version, maturity level at render time, ISO timestamp
• --check can short-circuit on metadata mismatch before full diff

User-authored content lives outside these markers and is never touched by regeneration. --merge wraps existing content in <!-- USER:AUTHORED:START --> / <!-- USER:AUTHORED:END --> below the ADD block for clarity.

Maturity-Aware Verbosity

The generator selects a rendering branch based on maturity.level:

Maturity	Sections	Target
poc	Project identity, 3–5 critical rules as bullets, pointers	<500 tokens
alpha	Identity, Engagement Protocol, Spec-First Invariants, pointers	<1K tokens
beta	All Alpha sections + TDD Discipline (when applicable), Maturity & Autonomy Ceiling, Currently Active Spec	<2K tokens
ga	All Beta sections + Team Conventions, Environment Promotion Ladder	<2.5K tokens

TDD Discipline is omitted when architecture.languages contains only Markdown / JSON / YAML / TOML — the project is documentation-only, strict TDD does not apply.

Modes

--write (default)

1. Read state (config + PRD + handoff + specs).
2. Render the managed body at the project's maturity level.
3. Build the full file: frontmatter (preserved) + user-head (preserved) + ADD marker block + user-tail (preserved).
4. Write AGENTS.md.
5. Clear .add/agents-md.stale if present.

--check

1. Read state.
2. Re-render what the file should be.
3. Diff against the on-disk AGENTS.md.
4. In sync → exit 0, print "AGENTS.md in sync."
5. Drift → exit 1, print a unified diff.

Designed for CI: python3 scripts/generate-agents-md.py --check can gate builds.

--merge

Used when the project already has a hand-curated AGENTS.md without ADD markers.

1. Read the existing file.
2. Preserve frontmatter (if any).
3. Wrap the existing body in <!-- USER:AUTHORED:START --> / <!-- USER:AUTHORED:END -->.
4. Prepend the ADD-managed marker block at the top (after frontmatter).
5. Write the merged file.

Future --write regenerations only touch content between the ADD markers. User-authored content is preserved forever.

--import

Alias for --merge with explicit "one-time migration" intent. Identical behavior; separate flag for documentation and audit clarity.

--dry-run

Combines with any mode. Prints the output to stdout without touching disk.

Staleness Marker

A PostToolUse hook (see runtimes/claude/hooks/post-write.sh) writes .add/agents-md.stale when any of these source files changes and AGENTS.md exists:

• .add/config.json
• core/rules/*.md (ADD-managed projects)
• core/skills/*/SKILL.md (ADD-managed projects)

Marker contents:

{
  "timestamp": "2026-04-22T14:32:01Z",
  "changed": ["core/rules/tdd-enforcement.md"]
}

The hook does not rewrite AGENTS.md. The next /add:agents-md invocation announces the stale state, lists the changed sources, then regenerates when the human runs --write.

Integration With Other Skills

• /add:init — calls /add:agents-md at the end of the init flow to write the initial AGENTS.md.
• /add:spec — after a new spec becomes the "spec under work", prompts: "Update AGENTS.md active-spec pointer? (Y/n)". On yes, runs /add:agents-md --write.
• /add:verify — opt-in Gate 4.5: if agentsMd.gateOnVerify: true is set in .add/config.json, /add:verify runs --check and fails the gate on drift. Off by default.
• /add:promote — maturity bumps recommend a regen (since the verbosity level changes) but do not auto-rewrite.

Configuration

{
  "agentsMd": {
    "gateOnVerify": false,
    "autoInitOnPromote": false
  }
}

Both keys are optional. If absent, defaults apply (gate off, no auto-init).

Edge Cases

Case	Behavior
No AGENTS.md exists	--write creates it fresh; no merge prompt needed
File with marker block	--write regenerates only the ADD section
File without marker block	--write aborts with exit 2 and a directive to use --merge
Frontmatter present	Preserved verbatim; ADD block is placed after it
No PRD	project.description from config is used as project identity
Maturity poc + no rules	Minimal identity-only output; 5 critical rules baked into the skill
Markdown/JSON-only project	TDD Discipline section omitted
Multiple specs	Most recently mutated wins; others not listed in v0.9.0
Marker partially deleted	Treated as missing; --merge required to recover
User edits inside ADD block	Overwritten on next --write; --check warns about this
Hook fires mid-task	.add/agents-md.stale write is atomic; no race
.add/agents-md.stale exists but file is in sync	Regen is idempotent; marker cleared
Nested per-subdirectory AGENTS.md	Out of scope for v0.9.0; single root file only

Output Format

After a successful --write:

Wrote AGENTS.md

Maturity: alpha
Sections rendered: Identity, Engagement Protocol, Spec-First Invariants, Pointers
Marker block: ADD:MANAGED (version=0.9.0, generated=2026-04-22T14:32:01Z)
Staleness marker: cleared

After --check drift:

AGENTS.md drift detected.
--- AGENTS.md (current)
+++ AGENTS.md (would-be)
@@ ... @@
 ...unified diff...

Run /add:agents-md --write to regenerate.
Exit code: 1

Process Observation

After completing this skill, do BOTH:

1. Observation Line

Append one observation line to .add/observations.md:

{YYYY-MM-DD HH:MM} | agents-md | {mode} | {write|check|merge|import} | {notes}

If .add/observations.md does not exist, create it with a # Process Observations header first.

2. Learning Checkpoint

Write a structured JSON learning entry per the checkpoint trigger in rules/learning.md if the session surfaced anything that should persist (e.g., AGENTS.md marker convention, rules summary gaps, first-time merge workflow friction). Classify scope, write to the appropriate JSON file, and regenerate the markdown view.