thin-plan

thin-plan is a skill for Claude Code, Codex from tmusser/ai-engineering-skills. It costs 16 tokens per session (309 once invoked), scanned A, original, MIT.

A planning skill that turns a mini-specification into three to seven small implementation slices. A mini-spec is a short description of what should be built and how its behavior should be checked.

In plain words
What is it for?
Use it when a repository has a SPEC.md file and you need a PLAN.md and TODO.md for implementing the work.
Why use it?
It breaks a broad coding task into smaller pieces that each produce visible progress and can be verified independently. It also records dependencies, risks, and the checks to run.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one.

Good fit Use it when a repository has a SPEC.md file and you need a PLAN.md and TODO.md for implementing the work.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/tmusser/ai-engineering-skills/thin-plan
Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Any agent
npx skills add tmusser/ai-engineering-skills --skill thin-plan
Clone the repo
git clone --depth 1 https://github.com/tmusser/ai-engineering-skills

Made for: Claude Code, Codex.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for thin-plan

README.md
[![agentmods](https://agentmods.dev/badge/skills/tmusser/ai-engineering-skills/thin-plan/github.svg)](https://agentmods.dev/skills/tmusser/ai-engineering-skills/thin-plan)
Your own site
<a href="https://agentmods.dev/skills/tmusser/ai-engineering-skills/thin-plan"><img src="https://agentmods.dev/badge/skills/tmusser/ai-engineering-skills/thin-plan/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for thin-plan

Your own site · 80×15
<a href="https://agentmods.dev/skills/tmusser/ai-engineering-skills/thin-plan"><img src="https://agentmods.dev/badge/skills/tmusser/ai-engineering-skills/thin-plan.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 16 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 309 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00016 $0.00309
Opus 5 $0.00008 $0.00154
Sonnet 5 $0.00003 $0.00062
Haiku 4.5 $0.00002 $0.00031

Measured 8d ago against content hash 414700479f5e, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-08, from the pricing page.

Security

Grade A, and why

thin-plan scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 8d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

skills/thin-plan/SKILL.md · 51 lines

What it actually says

Thin Plan

Purpose

Convert the mini-spec into 3-7 vertical implementation slices.

When to use

Use when SPEC.md exists and implementation needs a short, ordered path.

Inputs

  • SPEC.md
  • CONTEXT.md
  • Existing repo structure
  • Available verification commands

Workflow

  1. If SPEC.md has an active Contract ID, copy that ID exactly into PLAN.md. Do not invent an ID when SPEC has none.
  2. Identify the smallest end-to-end behavior.
  3. Create 3-7 slices that each produce observable behavior.
  4. Make every slice independently verifiable.
  5. Keep each slice to the fewest files possible.
  6. Avoid horizontal architecture-only tasks unless required.
  7. Record dependencies, risks, and verification strategy.
  8. Write PLAN.md and TODO.md.

Outputs

  • PLAN.md
  • TODO.md
  • Active Contract ID in PLAN.md only when SPEC opted into contract identity

Stop conditions

  • Each task has a visible result and a check.
  • Planning reveals a missing spec decision.

Anti-patterns

  • Planning all backend, then all frontend, then all tests.
  • Creating broad tasks that cannot be finished in one session.
  • Treating setup work as progress when no behavior changes.
  • Inventing contract identity for work whose SPEC did not opt in.
Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 8d ago First seen · 51 lines · 16 tokens per session scan A 414700479f5e

Subscribe to this mod's changes

thin-plan is a skill published in the GitHub repository tmusser/ai-engineering-skills (4 stars, last pushed yesterday), licensed MIT. It adds 16 tokens to every session and 309 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.

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