parallel-yak-implementation

parallel-yak-implementation is a skill for Claude Code, Codex from mattwynne/yaks. It costs 29 tokens per session (660 once invoked), scanned A, original, MIT.

A workflow for handling survived mutants in mutation testing. Mutation testing makes small changes to code to see whether the tests detect them; a survived mutant is a change the tests did not catch.

In plain words
What is it for?
Investigating mutation-testing results, deciding whether to add tests or improve the design, and documenting equivalent mutants that need no change.
Why use it?
It helps distinguish a missing test from a weak design or a change that behaves exactly like the original.

Skill for Claude CodeCodex

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

Good fit Investigating mutation-testing results, deciding whether to add tests or improve the design, and documenting equivalent mutants that need no change.

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Install with agentmods
npx agentmods add skills/mattwynne/yaks/parallel-yak-implementation
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 mattwynne/yaks --skill parallel-yak-implementation
Clone the repo
git clone --depth 1 https://github.com/mattwynne/yaks

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 parallel-yak-implementation

README.md
[![agentmods](https://agentmods.dev/badge/skills/mattwynne/yaks/parallel-yak-implementation.svg)](https://agentmods.dev/skills/mattwynne/yaks/parallel-yak-implementation)
Your own site
<a href="https://agentmods.dev/skills/mattwynne/yaks/parallel-yak-implementation"><img src="https://agentmods.dev/badge/skills/mattwynne/yaks/parallel-yak-implementation.svg" alt="Measured on agentmods" height="20"></a>
Per session 29 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 660 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. Third-party audits
  • NVIDIA SkillSpector pass 7 Sept 2026
How audits are shown
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 $0.00029 $0.00660
Opus 5 $0.00015 $0.00330
Sonnet 5 $0.00006 $0.00132
Haiku 4.5 $0.00003 $0.00066

Measured 8d ago against content hash abc6f2b23a54, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-07, from the pricing page.

Security

Grade A, and why

parallel-yak-implementation 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 8d 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/parallel-yak-implementation/SKILL.md · 93 lines

How it starts

The opening of the file, as written. The whole thing — 93 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Parallel Yak Implementation

Overview

When multiple leaf yaks are independent and have plans, dispatch one agent per yak in parallel worktrees. This skill wraps superpowers-dev:dispatching-parallel-agents with yak-specific lifecycle steps.

When to Use

  • 2+ leaf yaks are ready (have plans, no children)
  • The yaks don't modify the same files
  • You want to maximize throughput

The Process

1. Identify Ready Leaves

yx ls

Leaf yaks (no children) with plans are candidates. Verify independence: check their plans don't touch the same files.

2. Mark ALL as WIP Before Dispatching

This is the FIRST thing you do after identifying yaks.

yx state "<yak-name>" wip

Do this for EVERY yak BEFORE launching any agents. This signals to the human (and future sessions) what's being worked on.

Verify with yx ls - all target yaks should show as wip before you proceed to step 3.

3. Dispatch One Agent Per Yak

REQUIRED: Use superpowers-dev:dispatching-parallel-agents for the dispatch pattern.

Each agent prompt should include:

  • The yak's plan (from yx field --show "<name>" plan)
  • Instruction to invoke superpowers-dev:using-git-worktrees
  • Instruction to invoke superpowers-dev:executing-plans
  • Project context (test commands, commit conventions)
  • Clear scope: only work on this yak's files

4. When Agents Complete

For each returning agent:

  1. Review the summary
  2. Verify with dev check in the worktree
  3. Mark yak done: yx state "<name>" done
  4. Use superpowers-dev:finishing-a-development-branch

If an agent fails, keep the yak as wip and investigate.

⛔ The Main Branch Rule

Neither you nor your subagents may modify main's working tree. Main is for merging finished branches only.

  • Subagents must each work in their own worktree
  • The orchestrating agent (you) must not stash, clean, or edit files on main
  • If you see uncommitted changes on main, stop and ask the user — they belong to someone else

Read the full file on GitHub · 93 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. 8d ago First seen · 93 lines · 29 tokens per session scan A abc6f2b23a54

Subscribe to this mod's changes

parallel-yak-implementation is a skill published in the GitHub repository mattwynne/yaks (58 stars, last pushed 26d ago), licensed MIT. It adds 29 tokens to every session and 660 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.