skill-evolve

skill-evolve is a skill for Claude Code, Codex from yologdev/yoyo-evolve. It costs 21 tokens per session (7,197 once invoked), scanned A, original, MIT.

A tool for improving, creating, or retiring coding-agent skills based on patterns from previous sessions. It may only change skills marked as created by yoyo.

In plain words
What is it for?
Use it to review past session patterns and refine, deprecate, or retire eligible skills through the specified evolution process.
Why use it?
It keeps recurring skills aligned with what has been learned while preventing unrelated skills from being changed.

Skill for Claude CodeCodex

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/yologdev/yoyo-evolve/skill-evolve
Any agent
npx skills add yologdev/yoyo-evolve --skill skill-evolve
Clone the repo
git clone --depth 1 https://github.com/yologdev/yoyo-evolve

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 skill-evolve

README.md
[![agentmods](https://agentmods.dev/badge/skills/yologdev/yoyo-evolve/skill-evolve.svg)](https://agentmods.dev/skills/yologdev/yoyo-evolve/skill-evolve)
Your own site
<a href="https://agentmods.dev/skills/yologdev/yoyo-evolve/skill-evolve"><img src="https://agentmods.dev/badge/skills/yologdev/yoyo-evolve/skill-evolve.svg" alt="Measured on agentmods" height="20"></a>
Per session 21 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 7,197 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
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 $0.00021 $0.07197
Opus 5 $0.00010 $0.03599
Sonnet 5 $0.00004 $0.01439
Haiku 4.5 $0.00002 $0.00720

Measured 4d ago against content hash c4aa1f6099bb, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

skill-evolve 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 4d 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/skill-evolve/SKILL.md · 487 lines

How it starts

The opening of the file, as written. The whole thing — 487 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Skill Evolution

You are evolving your own skills. This is the only skill that modifies other skills. Treat every cycle with care — what you write here shapes how every future yoyo session behaves.

When to use

Only when invoked via scripts/skill_evolve.sh. The harness gates on session count and cooldown; it sets up the audit-log worktree and composes the prompt. Do not run this skill opportunistically from inside a normal evolve session.

Hard rules (read first, every cycle)

These three rules cannot be violated. Each cycle either honors all three or writes a refused event and exits.

HARD RULE #1 — Eligible targets only (allow-list)

You may refine, deprecate, or retire only skills whose frontmatter declares origin: yoyo. Any other value, OR a missing origin: field, means the skill is off-limits. This is an allow-list: silence means "don't touch."

Three categories of skill exist:

origin: value Source You may edit?
creator Written by the human creator (Yuanhao or a fork creator) Never
yoyo Written by yoyo (this skill, or in past evolutions like social/family/release) Yes — eligible
marketplace, gh:user/repo, etc. Installed from a third party Never — upstream owns it
(missing) Unknown provenance Never (default-safe)

Today the eligible set is exactly the skills whose SKILL.md declares origin: yoyo:

  • social
  • family
  • release
  • any skill you previously spawned (which inherit origin: yoyo from the Create template)

Defense in depth: if a skill has core: true set, refuse even if origin: yoyo is also somehow present. The two flags should never co-occur, but the conservative move is to honor the deny-flag.

If a recurring pattern suggests a non-eligible skill needs change (e.g., a core skill, or an installed marketplace skill), do not edit it. Instead, write a learning to memory/learnings.jsonl with source: "skill-evolve" and a clear pattern_key, and append a meta-suggestion block to skills/_journal.md. The human creator will decide.

Read the full file on GitHub · 487 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. 4d ago First seen · 487 lines · 21 tokens per session scan A c4aa1f6099bb

Subscribe to this mod's changes

skill-evolve is a skill published in the GitHub repository yologdev/yoyo-evolve (1,870 stars, last pushed 2d ago), licensed MIT. It adds 21 tokens to every session and 7,197 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 2026-08-30.

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