plan

An architecture-planning helper for Claude's planning mode. It turns requirements, limits, team details, timing, assumptions, and tradeoffs into shared architecture documents and, when useful, an interactive diagram.

In plain words
What is it for?
Use it when designing a new system or making a major change and you need to record decisions, constraints, and tradeoffs.
Why use it?
It gives a planned software system a clear written structure before implementation begins.

Skill for Claude CodeCodex

Part of the architect plugin — 4 skills shipped together

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.

agentmods
npx agentmods add skills/willhennessy/architect/plan
Any agent
npx skills add willhennessy/architect --skill plan
Clone the repo
git clone --depth 1 https://github.com/willhennessy/architect

Made for: Claude Code, Codex.

Or install architect, the plugin that ships this one along with the rest of its 4 skills.

Per session 101 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 4,070 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin unknown 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 $0.00101 $0.04070
Opus 5 $0.00051 $0.02035
Sonnet 5 $0.00020 $0.00814
Haiku 4.5 $0.00010 $0.00407

Measured 3d ago against content hash 09179b6794f6, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

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 3d 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.

claude-plugin/architect/skills/plan/SKILL.md · 343 lines

The source is not reproduced here

No licence file

A repository with no LICENSE is all rights reserved by default, so the body is not copied here. The metadata, the measurements and the link are.

Read it on GitHub

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. 3d ago First seen · 343 lines · 101 tokens per session scan A 09179b6794f6

Subscribe to this mod's changes

plan is a skill published in the GitHub repository willhennessy/architect (46 stars, last pushed 3mo ago), with no licence file. It adds 101 tokens to every session and 4,070 once invoked, about $0.0005 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 2026-08-30.

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