# Lean Plan > > - **Type:** Skill - **Install:** `agentstack add skill-nstungdev-claude-skills-lean-plan` - **Verified:** Yes — security-reviewed for prompt injection and unsafe behavior - **Seller:** [nstungdev](https://agentstack.voostack.com/s/nstungdev) - **Installs:** 0 - **Category:** [Agent Skills](https://agentstack.voostack.com/c/agent-skills) - **Latest version:** 0.1.0 - **License:** MIT - **Upstream author:** [nstungdev](https://github.com/nstungdev) - **Source:** https://github.com/nstungdev/claude-skills/tree/master/skills/dev-toolkit/skills/lean-plan ## Install ```sh agentstack add skill-nstungdev-claude-skills-lean-plan ``` Requires the [AgentStack CLI](https://agentstack.voostack.com/docs/cli). Works with Claude Code, Cursor, and any MCP-compatible agent. ## About # Lean Plan Write a PLAN.md that a reviewer can approve or reject in 30–60 seconds, answering four questions: **what** gets built, **how** (briefly), **what it affects**, and **what it explicitly won't do**. It does not answer why or who — that's already in `SPEC.md`. Link to it, don't repeat it. **Written for a reviewing supervisor, not a line-by-line coder.** The user delegates implementation to Claude and reviews checkpoints rather than reading code directly — so even though `PLAN.md` is more technical than `SPEC.md`, it must stay a fast approve/reject read. Full technical breakdown (step-by-step approach, data flow, rationale per decision) does NOT belong here — that level of detail is for `lean-task` once implementation actually starts. `PLAN.md`'s "How" section is a 2–4 line summary of approach, not the full breakdown. The Components table doubles as input for later task breakdown — each row must stand on its own well enough to become a task later, but the plan itself stays short. --- ## Modes ### Step 0 — Check current state Check whether `specs/{feature-name}/SPEC.md` exists before doing anything else. - No `SPEC.md` → stop. A plan built on an unscoped feature just encodes assumptions as fact. Tell the user to run `lean-spec` first. - `SPEC.md` exists, no `PLAN.md` → **`init`** - `PLAN.md` exists → **`update`** ## Mode: init ### Step 1 — Extract, don't interrogate Read the feature's `SPEC.md` — it already carries the domain and user context; don't re-derive it here. Extract what's already available from the conversation: - Components or modules already mentioned - The high-level approach, if already discussed - Existing systems/features/data likely to be touched - Anything already ruled out or marked as technically out of scope - Hard constraints already stated Only ask about what is **genuinely missing**: the component breakdown, the approach, impact, and any hard constraints. Ask everything in a single message. If a decision isn't final yet, don't write it down as one — send it back to `SPEC.md`'s Open Questions instead. ### Step 2 — Generate PLAN.md Read `references/plan-template.md` and fill it in, using the same `{feature-name}` slug as the feature's `SPEC.md`. Rules: - One page max, tables and short bullets only — the four review sections must read in under a minute - **What** (Components): one row per unit of work, with the action (create / modify / delete) and any key detail - **How**: 2–4 lines, plain language, high-level approach only — no options, no per-decision rationale, no step-by-step. If it's growing past 4 lines, that detail belongs in `lean-task`, not here - **Impact**: existing systems, files, features, or data this touches — this is what lets a reviewer judge blast radius without reading code - **Won't Do**: explicit technical exclusions, not soft preferences - **Constraints**: hard rules only ### Step 3 — Confirm and save Show the full generated PLAN.md to the user. Ask if anything needs adjusting. Once confirmed, save as `specs/{feature-name}/PLAN.md` — the same feature folder as its `SPEC.md`. --- ## Mode: update `PLAN.md` is a frozen blueprint, not a progress tracker — it records what was decided, not what's done. Once tasks are underway, only touch it if the technical design itself changes. ### When to update - A component gets added, split, or removed - The approach changes - The blast radius (impact) turns out to be different than planned - A new hard constraint is discovered mid-build ### How to update 1. Read the existing `PLAN.md` 2. Edit only the affected row or section — do not rewrite the whole file 3. Append a row to the Revision Log with the absolute date (`YYYY-MM-DD`, resolved from the current date — never a relative term like "today") and a short description of what changed and why 4. Trim the Revision Log to the 10 most recent entries 5. Update `Last updated` at the top If nothing about the technical design has actually changed, don't edit — progress alone (a component getting built) is not a reason to touch this file. --- ## Principles - **A blueprint, not a tracker** — `PLAN.md` records what was decided, not what's done; don't add status columns or checkboxes - **Built on the spec, not a copy of it** — link to `SPEC.md`, don't restate its problem, users, or scope - **Written for the reviewer's 60 seconds, not the implementer's hour** — the four review sections (What / How / Impact / Won't Do) are the whole point; anything that only serves implementation detail belongs in `lean-task` - **"How" is a summary, not a spec** — if it needs step-by-step or per-decision rationale to make sense, that's too much detail for this file - **Decisions are final when written** — an unresolved choice belongs in `SPEC.md`'s Open Questions, not here - **Components are future task units** — write each row specific enough that it could be handed off as a task as-is, not vague enough to need re-interpreting later - **Frozen once tasks start** — edit only when the plan itself changes, never to reflect progress ## Source & license This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code. - **Author:** [nstungdev](https://github.com/nstungdev) - **Source:** [nstungdev/claude-skills](https://github.com/nstungdev/claude-skills) - **License:** MIT Install and usage instructions live in the source repository linked above. ## Pricing - **Free** — Free ## Security capabilities Automated source analysis of v0.1.0 — what this tool can access: - **Network access:** no - **Filesystem access:** no - **Shell / process execution:** no - **Environment & secrets:** no - **Dynamic code execution:** no *"Yes" means the capability is present in the source — more access means more to trust, not that it is unsafe.* ## Versions - **0.1.0** — security scan: passed — Imported from the upstream source. ## Links - Listing page: https://agentstack.voostack.com/l/skill-nstungdev-claude-skills-lean-plan - Seller: https://agentstack.voostack.com/s/nstungdev - Browse the marketplace: https://agentstack.voostack.com/browse --- Listed on AgentStack — the marketplace for AI agent skills and MCP servers. Every listing is security-reviewed. Creators keep 70%.