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Arch4: Skill for Cursor

.cursor/skills/c4/SKILL.md

c4 is a skill for Cursor from P451M/Arch4. It costs 18 tokens per session (707 once invoked), scanned A, original, no licence file.

A guide to the C4 model, a way to show software architecture at different levels of detail using diagrams.

In plain words
What is it for?
It helps describe systems, containers, components, and code-level relationships in architecture diagrams.
Why use it?
It gives architecture diagrams a shared structure and vocabulary, making them easier to create and review.

Skill for Cursor

Written for Cursor: installed under .cursor/.

This is P451M/Arch4's own configuration. It tells Cursor how to work on Arch4 itself, so it is not a mod to install elsewhere. Copy it as a starting point and replace the rules that are about this project. Everything Arch4 configures →

not rated 4repo 4mo ago A scan 18 tokens custom licence
View source ↗ P451M/Arch4
Reuse

Borrowing it

Nothing to install: this file belongs to P451M/Arch4. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.

Copy the file
curl -O https://raw.githubusercontent.com/P451M/Arch4/main/.cursor/skills/c4/SKILL.md
Clone the repo
git clone --depth 1 https://github.com/P451M/Arch4

Made for: Cursor.

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 c4

README.md
[![agentmods](https://agentmods.dev/badge/skills/p451m/arch4/c4/github.svg)](https://agentmods.dev/skills/p451m/arch4/c4)
Your own site
<a href="https://agentmods.dev/skills/p451m/arch4/c4"><img src="https://agentmods.dev/badge/skills/p451m/arch4/c4/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 c4

Your own site · 80×15
<a href="https://agentmods.dev/skills/p451m/arch4/c4"><img src="https://agentmods.dev/badge/skills/p451m/arch4/c4.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 18 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 707 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 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 5.1 $0.00018 $0.00707
Opus 5.5 $0.00007 $0.00283
Sonnet 5.5 $0.00004 $0.00141
Haiku 4.5 $0.00002 $0.00071

Measured 2mo ago against content hash 52015756223d, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

c4 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 2mo 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.

.cursor/skills/c4/SKILL.md · 71 lines

The source is not reproduced here

A licence we could not identify

The repository carries a LICENSE file, but it is custom or dual enough that GitHub cannot name it and neither can this catalogue. Unknown terms are not permission, so the body is not copied here. Read the licence at the source and decide for yourself.

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. 2mo ago First seen · 71 lines · 18 tokens per session scan A 52015756223d

Subscribe to this mod's changes

c4 is a skill published in the GitHub repository P451M/Arch4 (4 stars, last pushed 4mo ago), with no licence file. It adds 18 tokens to every session and 707 once invoked, about $0.0001 per session on Opus 5.5. 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.

architecturearchitecture-mapc4cursordiagramsstructurizr
Related

c4 compared with skills from other repositories

c4 next to 6 skills from other repositories
ModTypeStarsLast pushLicenceScanTokensWorks with
c4P451M/Arch4Skill44mo agononeA18Cursor
kroki-diagramssmoldrago/kroki-diagramsSkill610d agoMITA111Claude Code, Codex
Architecture Diagrams Readinesss977043/river-reviewSkill7yesterdayMITA27Claude Code
architecture-diagram-creatorbookforge-ai/bookforge-skillsSkill426mo agoCC-BY-SA-4.0A128Claude Code
architecture-diagrammateaix/mateclawSkill1.2kyesterdayApache-2.0A15Claude Code, Codex
editing-model-diagramsgoadesign/modelSkill4674d agoMITA69Claude Code, Codex
init-workspace-documentationgriddynamics/rosettaSkill370todayApache-2.0A10Claude Code