C31-plan

C31-plan is a skill for Claude Code, Codex from ChianW/C31. It costs 34 tokens per session (5,596 once invoked), scanned A, original, MIT.

A planning guide that turns requirements into validated, step-by-step implementation plans. It separates deciding what to build from deciding how to build it, and includes coverage checks, dependency analysis, and threat modeling.

In plain words
What is it for?
Use it to plan a feature, project, bug fix, or implementation phase. It can deepen an existing plan and produce an execution sequence in the user's language.
Why use it?
It helps prevent missing requirements, overlooked dependencies, and security risks in multi-step work. It uses existing requirements or strategy documents as the source of truth when they are available.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one. Also seen: mentions CLAUDE.md; mentions subagents; mentions AGENTS.md.

Good fit Use it to plan a feature, project, bug fix, or implementation phase.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/chianw/c31/c31-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 ChianW/C31 --skill c31-plan
Clone the repo
git clone --depth 1 https://github.com/ChianW/C31

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 C31-plan

README.md
[![agentmods](https://agentmods.dev/badge/skills/chianw/c31/c31-plan.svg)](https://agentmods.dev/skills/chianw/c31/c31-plan)
Your own site
<a href="https://agentmods.dev/skills/chianw/c31/c31-plan"><img src="https://agentmods.dev/badge/skills/chianw/c31/c31-plan.svg" alt="Measured on agentmods" height="20"></a>
Per session 34 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 5,596 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 1 finding. 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 $0.00034 $0.05596
Opus 5 $0.00017 $0.02798
Sonnet 5 $0.00007 $0.01119
Haiku 4.5 $0.00003 $0.00560

Measured 6d ago against content hash 87fed42b4037, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-06, from the pricing page.

Security

Grade A, and why

C31-plan scanned grade A with 1 finding 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 6d 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.

Makes network callslowCapability

Not a fault in itself. Listed so you know the mod talks to something, and to what.

| `kimi_search` | `exec` + `curl` | `RATE_LIMITED` persists |
skills/core/C31-plan/SKILL.md · 463 lines

How it starts

The opening of the file, as written. The whole thing — 463 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Multilingual Triggers

Language Trigger phrases
EN plan, 制定计划, 实现方案, 怎么实现, 分步, plan-phase, roadmap
ZH 制定计划, 规划, 怎么实现, 分步
JA 計画を立てる, プランニング, 実装方法を考える

Output language: Respond automatically in the user's conversation language.

C31-plan

Turn requirements into validated, executable plans. C31-brainstorm defines WHAT; C31-plan defines HOW — with coverage gates, wave analysis, and threat modeling.

Trigger

User says "plan", "制定计划", "实现方案", "怎么实现", "分步", "plan-phase", "roadmap", or any request to break down a task into an executable plan.

Inputs

Gather before proceeding. If not provided, ask:

  1. What to plan — task, goal, feature, or project. Accepts a feature description, a requirements doc path, a brainstorm output, or a bug report.
  2. Upstream document (optional) — path to a *-requirements.md or STRATEGY.md in docs/brainstorms/ or memory/.planning/. Read first; treat as source of truth.
  3. Existing plan to deepen (optional) — identify target in memory/.planning/phases/ and short-circuit to Plan-Checker (Phase 5).

Core Principles

  1. Requirements as source of truth — Build from upstream docs; never re-invent behavior.
  2. Decisions, not code — Capture approach, boundaries, files, dependencies, risks, and test scenarios.
  3. Research before structuring — Explore codebase, docs/solutions/, AGENTS.md, CLAUDE.md.
  4. Nyquist validation — Map test coverage to every requirement before execution.
  5. Decision coverage gate (blocking) — Every CONTEXT.md decision must appear in the plan.
  6. Package legitimacy gate — Audit external dependencies with [OK] / [SUS] / [SLOP] tagging.
  7. Right-size the artifact — Same philosophy at every depth.
  8. Separate planning from execution discovery — Resolve planning-time questions here.
  9. Keep the plan portable — Repo-relative paths only.
  10. Doubt-Driven Development — Every non-trivial decision must survive adversarial scrutiny before it enters the plan.

Read the full file on GitHub · 463 lines

Files

What ships with it

1 file beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

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. 6d ago First seen · 463 lines · 34 tokens per session scan A 87fed42b4037

Subscribe to this mod's changes

C31-plan is a skill published in the GitHub repository ChianW/C31 (1 stars, last pushed 11d ago), licensed MIT. It adds 34 tokens to every session and 5,596 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 1 finding (makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.

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