cadenza: Skill for Claude Code

.claude/skills/cadenza/SKILL.md

cadenza is a skill for Claude Code, Codex from rkttu/cadenza. It costs 78 tokens per session (3,637 once invoked), scanned B, original, MIT.

A family of .NET 10 or newer single-file scripting tools. Each program can run from one C# file and can be published as a standalone executable.

In plain words
What is it for?
Use it for shell automation, background workers, small HTTP APIs, webhooks, MCP servers, and local AI agents. It is not intended for multi-project solutions or libraries distributed as DLLs.
Why use it?
It provides a compact way to build small utilities and services without setting up a full multi-project application.

Skill for Claude CodeCodex

Written for Claude Code and Codex: installed under .claude/, but also reads ~/.codex or $CODEX_HOME. Also seen: mentions Codex; built for aider.

This is rkttu/cadenza's own configuration. It tells Claude Code and Codex how to work on cadenza 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 cadenza configures →

Reuse

Borrowing it

Nothing to install: this file belongs to rkttu/cadenza. 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/rkttu/cadenza/main/.claude/skills/cadenza/SKILL.md
Clone the repo
git clone --depth 1 https://github.com/rkttu/cadenza

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 cadenza

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

Your own site · 80×15
<a href="https://agentmods.dev/skills/rkttu/cadenza/cadenza"><img src="https://agentmods.dev/badge/skills/rkttu/cadenza/cadenza.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 78 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 3,637 The whole file, excluding the scripts and references it only reads on demand.
Security scan B 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 $0.00078 $0.03637
Opus 5 $0.00039 $0.01818
Sonnet 5 $0.00016 $0.00727
Haiku 4.5 $0.00008 $0.00364

Measured 11d ago against content hash d7550bafbf70, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-11, from the pricing page.

Security

Grade B, and why

cadenza scanned grade B 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 11d 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.

Reads agent configuration directoriesmediumAgent snooping

.claude/, .codex/, .gemini/ hold keys, settings and other credentials a mod has no legitimate need for.

Configure Codex at `~/.codex/config.toml`:
.claude/skills/cadenza/SKILL.md · 308 lines

How it starts

The opening of the file, as written. The whole thing — 308 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Cadenza skill

Cadenza is .NET's answer to "Python for scripting" with "Go-like single-binary distribution". Every Cadenza program is one .cs file that runs with dotnet run app.cs and publishes to a ~30–40 MB self-contained binary with dotnet publish app.cs -r <rid> -c Release.

Repo: https://github.com/rkttu/cadenza

When to suggest Cadenza

Pick Cadenza when the user wants:

Goal SDK Use case
CLI / shell automation / build glue Cadenza git deploy guards, file processing, devops scripts
Background service / daemon Cadenza.Worker heartbeat, polling, scheduled work
Minimal HTTP API / webhook Cadenza.Web a 30-line REST endpoint, internal tool
MCP server (AI tool integration) Cadenza.Mcp tools / resources / prompts for Claude Desktop, Cursor, VS Code AI
Local AI agent Cadenza.Agent OpenAI-compatible HTTP server fronting Ollama / OpenAI / Anthropic / Azure OpenAI — Codex / Aider / Continue / Cursor talk to it as if it were OpenAI

Skip Cadenza for multi-project solutions, libraries that ship as DLLs, or anything that needs a full csproj. Cadenza is for the "single file = whole program" case.

Critical: exact version pinning

MSBuild SDK references do NOT support wildcards (1.*). Always pin an exact SemVer version. Check nuget.org for the latest, then write the exact version on the #:sdk line:

#:sdk [email protected]           // console
#:sdk [email protected]    // worker
#:sdk [email protected]       // web
#:sdk [email protected]       // MCP server
#:sdk [email protected]     // AI agent (OpenAI-compatible HTTP)

Latest versions (as of this skill update): all five SDKs at 1.0.15.

Tier 1 — bare names per variant (no namespace prefix needed)

Cadenza (console)

Name Signature Purpose
Run int Run(string cmd, bool throwOnError = false) Run a shell command, return exit code
Capture string Capture(string cmd) Run a shell command, return stdout (throws on non-zero)
ReadText string ReadText(string path) Read a UTF-8 text file
WriteText void WriteText(string path, string content) Write a UTF-8 text file
Glob IEnumerable<string> Glob(string pattern) Match files; supports ** and *
TempDir TempDirectory TempDir() using var t = TempDir(); auto-cleanup
WriteLine / Write / ReadLine (standard System.Console) stdout / stdin

Read the full file on GitHub · 308 lines

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. 11d ago First seen · 308 lines · 78 tokens per session scan B d7550bafbf70

Subscribe to this mod's changes

cadenza is a skill published in the GitHub repository rkttu/cadenza (4 stars, last pushed 3mo ago), licensed MIT. It adds 78 tokens to every session and 3,637 once invoked, about $0.0004 per session on Opus 5. A static security scan graded it B with 1 finding (reads agent configuration directories). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.

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