harness

harness is a skill for Claude Code from hamzaPixl/pixl-ai. It costs 62 tokens per session (1,753 once invoked), scanned A, original, MIT.

A development loop in which one agent generates an application and another evaluates it with Playwright, a tool for testing web pages in a browser. The evaluation covers design, originality, implementation quality, and functionality, then sends feedback for another iteration.

In plain words
What is it for?
Use it when building applications automatically, testing generated interfaces, and iterating until the results meet defined quality thresholds.
Why use it?
It provides a repeatable way to find weaknesses in autonomously generated applications and improve them through several review cycles.

Skill for Claude Code

Written for Claude Code: allowed-tools in frontmatter. Also seen: mentions subagents; names the AskUserQuestion tool.

Part of the pixl-crew plugin — 93 skills, 14 agents, 6 hooks shipped together

Good fit Use it when building applications automatically, testing generated interfaces, and iterating until the results meet defined quality thresholds.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/hamzapixl/pixl-ai/harness
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 hamzaPixl/pixl-ai --skill harness
Clone the repo
git clone --depth 1 https://github.com/hamzaPixl/pixl-ai

Made for: Claude Code.

Or install pixl-crew, the plugin that ships this one along with the rest of its 93 skills, 14 agents, 6 hooks.

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

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

Your own site · 80×15
<a href="https://agentmods.dev/skills/hamzapixl/pixl-ai/harness"><img src="https://agentmods.dev/badge/skills/hamzapixl/pixl-ai/harness.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 62 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,753 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 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 $0.00062 $0.01753
Opus 5.5 $0.00025 $0.00701
Sonnet 5.5 $0.00012 $0.00351
Haiku 4.5 $0.00006 $0.00175

Measured 1mo ago against content hash 310674b4fe14, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

harness 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 1mo 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.

packages/crew/skills/harness/SKILL.md · 151 lines

How it starts

The opening of the file, as written. The whole thing — 151 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Harness

GAN-inspired generate-evaluate-iterate loop. A generator agent builds the application, then an independent evaluator agent grades the output on four axes. If any score falls below threshold, the evaluator's critique feeds back into the generator for another pass. The loop continues until all scores pass or max iterations are reached.

Required References

Before starting, read ALL of these:

  • references/grading-rubric.md -- 4-axis scoring criteria (design quality, originality, craft, functionality)
  • references/anti-rationalization.md -- rules for honest evaluation, common rationalization traps
  • references/integrity-protocol.md -- no-hack rules, zero-assumption debugging, consensus validation, escalation protocol

Step 1: Input & Configuration

Accept a 1-4 sentence product description as the skill argument.

Ask the user (via AskUserQuestion) for optional configuration overrides. Use these defaults if the user skips:

Parameter Default Description
Threshold 7/10 Minimum score on each axis to pass
Max iterations 5 Maximum generate-evaluate cycles before hard stop
Budget cap $150 Total spend limit across all iterations
Aesthetic direction (none) Optional style guidance (e.g., "museum quality", "minimal dark mode")

Step 2: Execute via Engine Workflow (preferred path)

If the pixl CLI is available, delegate to the engine DAG:

pixl workflow run harness --prompt "<user prompt>" --yes

This runs the full DAG: plan -> generate -> evaluate -> score-gate -> (loop on failure).

Use --stream for real-time progress output. Monitor cost with pixl cost summary after completion.

If the engine workflow succeeds, skip to Step 4 (report).

Step 3: Fallback -- Direct Agent Loop (when pixl CLI unavailable)

Read the full file on GitHub · 151 lines

Files

What ships with it

4 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

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. 1mo ago First seen · 151 lines · 62 tokens per session scan A 310674b4fe14

Subscribe to this mod's changes

harness is a skill published in the GitHub repository hamzaPixl/pixl-ai (2 stars, last pushed 6mo ago), licensed MIT. It adds 62 tokens to every session and 1,753 once invoked, about $0.0002 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 2026-09-03.

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