harness-engineering-playbook

harness-engineering-playbook is a skill for Claude Code, Codex from broomva/harness-engineering. It costs 54 tokens per session (516 once invoked), scanned A, original, MIT.

A playbook for making a software repository easier for coding agents to work in reliably. It adds documented rules, repeatable checks, clear module boundaries, and structured logging.

In plain words
What is it for?
Setting up AGENTS.md and PLANS.md, documenting architecture and observability, adding smoke/check/CI commands, and auditing repository health.
Why use it?
It reduces inconsistent agent runs, unclear architecture, flaky checks, missing visibility, and gradual documentation drift.

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/broomva/harness-engineering/harness-engineering
Any agent
npx skills add broomva/harness-engineering --skill harness-engineering
Clone the repo
git clone --depth 1 https://github.com/broomva/harness-engineering

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 harness-engineering-playbook

README.md
[![agentmods](https://agentmods.dev/badge/skills/broomva/harness-engineering/harness-engineering.svg)](https://agentmods.dev/skills/broomva/harness-engineering/harness-engineering)
Your own site
<a href="https://agentmods.dev/skills/broomva/harness-engineering/harness-engineering"><img src="https://agentmods.dev/badge/skills/broomva/harness-engineering/harness-engineering.svg" alt="Measured on agentmods" height="20"></a>
Per session 54 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 516 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 $0.00054 $0.00516
Opus 5 $0.00027 $0.00258
Sonnet 5 $0.00011 $0.00103
Haiku 4.5 $0.00005 $0.00052

Measured 5d ago against content hash 8d6fe3e3e5e4, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

harness-engineering-playbook 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 5d 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.

SKILL.md · 60 lines

How it starts

The opening of the file, as written. The whole thing — 60 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Harness Engineering Playbook

A skills.sh-compatible skill that operationalizes the practices from OpenAI's Harness Engineering guide. Use it to set up or refactor agent-first workflows so that autonomous runs are repeatable, observable, and safe.

Install

npx skills add broomva/harness-engineering-skill --skill harness-engineering-playbook

What It Does

  • Bootstraps harness artifacts: AGENTS.md, PLANS.md, docs/ARCHITECTURE.md, docs/OBSERVABILITY.md, Makefile.harness, and CI workflows.
  • Wraps deterministic commands behind make smoke, make check, make ci so agents can run them reliably.
  • Enforces strict module boundaries and data-shape contracts.
  • Wires structured observability (correlation IDs, key transitions) from day 1.
  • Adds entropy-control audits and nightly harness checks to prevent docs drift and flaky scripts.

Workflow

  1. Baseline the target repo — detect language, toolchain, and existing CI.
  2. Bootstrap harness artifacts from templates (interactive wizard or shell script).
  3. Apply the nine Harness Engineering practices across repo artifacts.
  4. Validate with audit — treat any MISSING or FAIL as blocking.
  5. Iterate after real agent runs — patch gaps and re-audit.

Quick Start

# Interactive wizard (recommended)
python3 .agents/skills/harness-engineering-playbook/scripts/harness_wizard.py init <repo-path> --profile control

# Shell fallback
./scripts/bootstrap_harness.sh <repo-path>

# Audit
python3 .agents/skills/harness-engineering-playbook/scripts/harness_wizard.py audit <repo-path>

Profiles

Profile Scope
baseline Core harness artifacts only
control Baseline + control-system primitives
full Control + entropy controls, nightly audit, CI

Source

OpenAI Harness Engineering guide: https://openai.com/index/harness-engineering/

Read the full file on GitHub · 60 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. 5d ago First seen · 60 lines · 54 tokens per session scan A 8d6fe3e3e5e4

Subscribe to this mod's changes

harness-engineering-playbook is a skill published in the GitHub repository broomva/harness-engineering (25 stars, last pushed 2mo ago), licensed MIT. It adds 54 tokens to every session and 516 once invoked, about $0.0003 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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