# Harness — The Team-Architecture Factory for Claude Code
**English** | [한국어](README_KO.md) | [日本語](README_JA.md)
> **Harness is a team-architecture factory for Claude Code.** Say **"build a harness for this project"** (English) or **"하네스 구성해줘"** (한국어) or **"ハーネスを構成して"** (日本語), and the plugin turns your domain description into an agent team and the skills they use — picked from six pre-defined team-architecture patterns.
## Overview
Harness leverages Claude Code's agent team system to decompose complex tasks into coordinated teams of specialized agents. Say "build a harness for this project" and it automatically generates agent definitions (`.claude/agents/`) and skills (`.claude/skills/`) tailored to your domain.
## Category — Where Harness Sits
Harness lives at the **L3 Meta-Factory** layer of the Claude Code ecosystem — the layer that generates other harnesses rather than being one. Inside L3, we pick a specific sub-layer: **Team-Architecture Factory**.
| Layer | What it does | Neighbors we coexist with |
|-------|--------------|---------------------------|
| **L3 — Meta-Factory / Team-Architecture Factory** (us) | Domain sentence → agent team + skills, via 6 pre-defined team patterns | — |
| L3 — Meta-Factory / Runtime-Configuration Factory | Deterministic, repeatable runtime configurations | [coleam00/Archon](https://github.com/coleam00/Archon) |
| L3 — Meta-Factory / Codex Runtime Port | Same concept, Codex runtime | [SaehwanPark/meta-harness](https://github.com/SaehwanPark/meta-harness) |
| L2 — Cross-Harness Workflow | Standardize skills/rules/hooks across multiple harnesses | [affaan-m/ECC](https://github.com/affaan-m/everything-claude-code) |
> Archon generates deterministic runtime configurations. Harness generates team architectures (pipeline, fan-out/fan-in, expert pool, producer-reviewer, supervisor, hierarchical delegation) plus the skills agents use. Different sub-layers of the same L3. Pick Archon for runtime determinism, Harness for team architecture, or combine them.
## Star History
## Key Features
- **Agent Team Design** — 6 architectural patterns: Pipeline, Fan-out/Fan-in, Expert Pool, Producer-Reviewer, Supervisor, and Hierarchical Delegation
- **Skill Generation** — Auto-generates skills with Progressive Disclosure for efficient context management
- **Orchestration** — Inter-agent data passing, error handling, and team coordination protocols
- **Validation** — Trigger verification, dry-run testing, and with-skill vs without-skill comparison tests
## Harness Evolution Mechanism
The harness evolution mechanism feeds deltas (what worked / what didn't) back into the factory, so the next generation is measurably better. When a generated harness is used in a real project, the `/harness:evolve` skill captures the delta between the initial architecture and the shipped one, and feeds it back into the factory so the next generation for a similar domain starts closer to the shipped state.
```
Initial harness ──▶ Real project use ──▶ Shipped harness
│
▼ (delta capture via /harness:evolve)
┌───────────────┐
│ Factory │◀── better next-gen draft
└───────────────┘
```
We call this the **Harness Evolution Mechanism** (KR: 하네스 진화 메커니즘; JA: ハーネス進化メカニズム).
## Workflow
```
Phase 1: Domain Analysis
↓
Phase 2: Team Architecture Design (Agent Teams vs Subagents)
↓
Phase 3: Agent Definition Generation (.claude/agents/)
↓
Phase 4: Skill Generation (.claude/skills/)
↓
Phase 5: Integration & Orchestration
↓
Phase 6: Validation & Testing
```
## Installation
### Via Marketplace
#### Add the marketplace
```shell
/plugin marketplace add revfactory/harness
```
#### Install the plugin
```shell
/plugin install harness@harness
```
### Direct Installation as Global Skill
```shell
# Copy the skills directory to ~/.claude/skills/harness/
cp -r skills/harness ~/.claude/skills/harness
```
## Plugin Structure
```
harness/
├── .claude-plugin/
│ └── plugin.json # Plugin manifest
├── skills/
│ └── harness/
│ ├── SKILL.md # Main skill definition (6-Phase workflow)
│ └── references/
│ ├── agent-design-patterns.md # 6 architectural patterns
│ ├── orchestrator-template.md # Team/subagent orchestrator templates
│ ├── team-examples.md # 5 real-world team configurations
│ ├── skill-writing-guide.md # Skill authoring guide
│ ├── skill-testing-guide.md # Testing & evaluation methodology
│ └── qa-agent-guide.md # QA agent integration guide
└── README.md
```
## Usage
Trigger in Claude Code with prompts like:
```
Build a harness for this project
Design an agent team for this domain
Set up a harness
```
### Execution Modes
| Mode | Description | Recommended For |
|------|-------------|-----------------|
| **Agent Teams** (default) | TeamCreate + SendMessage + TaskCreate | 2+ agents requiring collaboration |
| **Subagents** | Direct Agent tool invocation | One-off tasks, no inter-agent communication needed |
### Architecture Patterns
| Pattern | Description |
|---------|-------------|
| Pipeline | Sequential dependent tasks |
| Fan-out/Fan-in | Parallel independent tasks |
| Expert Pool | Context-dependent selective invocation |
| Producer-Reviewer | Generation followed by quality review |
| Supervisor | Central agent with dynamic task distribution |
| Hierarchical Delegation | Top-down recursive delegation |
## Output
Files generated by Harness:
```
your-project/
├── .claude/
│ ├── agents/ # Agent definition files
│ │ ├── analyst.md
│ │ ├── builder.md
│ │ └── qa.md
│ └── skills/ # Skill files
│ ├── analyze/
│ │ └── SKILL.md
│ └── build/
│ ├── SKILL.md
│ └── references/
```
## Use Cases — Try These Prompts
Copy any prompt below into Claude Code after installing Harness:
**Deep Research**
```
Build a harness for deep research. I need an agent team that can investigate
any topic from multiple angles — web search, academic sources, community
sentiment — then cross-validate findings and produce a comprehensive report.
```
**Website Development**
```
Build a harness for full-stack website development. The team should handle
design, frontend (React/Next.js), backend (API), and QA testing in a
coordinated pipeline from wireframe to deployment.
```
**Webtoon / Comic Production**
```
Build a harness for webtoon episode production. I need agents for story
writing, character design prompts, panel layout planning, and dialogue
editing. They should review each other's work for style consistency.
```
**YouTube Content Planning**
```
Build a harness for YouTube content creation. The team should research
trending topics, write scripts, optimize titles/tags for SEO, and plan
thumbnail concepts — all coordinated by a supervisor agent.
```
**Code Review & Refactoring**
```
Build a harness for comprehensive code review. I want parallel agents
checking architecture, security vulnerabilities, performance bottlenecks,
and code style — then merging all findings into a single report.
```
**Technical Documentation**
```
Build a harness that generates API documentation from this codebase.
Agents should analyze endpoints, write descriptions, generate usage
examples, and review for completeness.
```
**Data Pipeline Design**
```
Build a harness for designing data pipelines. I need agents for schema
design, ETL logic, data validation rules, and monitoring setup that
delegate sub-tasks hierarchically.
```
**Marketing Campaign**
```
Build a harness for marketing campaign creation. The team should research
the target market, write ad copy, design visual concepts, and set up
A/B test plans with iterative quality review.
```
## Coexistence — Harness and Neighbors
Harness is not alone in the Claude Code / agent-framework ecosystem. The following repos live in adjacent layers; each is described in a parallel "X is …, Harness is …" form so you can pick the one that fits your need or combine several.
| Repo | Their position | Relationship to Harness |
|------|----------------|-------------------------|
| [coleam00/Archon](https://github.com/coleam00/Archon) | "harness builder" — deterministic, repeatable runtime configurations | **Same L3, neighbor sub-layer.** Archon is a Runtime-Configuration Factory, Harness is a Team-Architecture Factory. Pick Archon for runtime determinism, Harness for team architecture, or combine them. |
| [SaehwanPark/meta-harness](https://github.com/SaehwanPark/meta-harness) | Codex port of the same concept | **Same L3, different runtime.** Use Harness on Claude Code, meta-harness on Codex. |
| [affaan-m/ECC](https://github.com/affaan-m/everything-claude-code) | "Agent harness performance & workflow layer" (sits on top of existing harnesses) | **Different layer.** ECC is a standardization layer across harnesses; Harness is a factory that generates harnesses. Serial combination possible. |
| [wshobson/agents](https://github.com/wshobson/agents) | Subagent / skill catalog (182 agents, 149 skills) | **Factory ↔ parts supply.** wshobson is a catalog to shop from; Harness designs the team. Absorb wshobson entries as parts inside a Harness-generated team. |
| [LangGraph](https://langchain-ai.github.io/langgraph/) | State-graph orchestration, LLM-agnostic | **Different track.** LangGraph is for long-running, state-recoverable orchestration; Harness is for fast Claude-Code-native team design. |
## Built with Harness
### Harness 100
**[revfactory/harness-100](https://github.com/revfactory/harness-100)** — 100 production-ready agent team harnesses across 10 domains, available in both English and Korean (200 packages total). Each harness ships with 4-5 specialist agents, an orchestrator skill, and domain-specific skills — all generated by this plugin. 1,808 markdown files covering content creation, software development, data/AI, business strategy, education, legal, health, and more.
### Research: A/B Testing Harness Effectiveness
**[revfactory/claude-code-harness](https://github.com/revfactory/claude-code-harness)** — A controlled experiment across 15 software engineering tasks measuring the impact of structured pre-configuration on LLM code agent output quality.
| Metric | Without Harness | With Harness | Improvement |
|--------|:-:|:-:|:-:|
| Average Quality Score | 49.5 | 79.3 | **+60%** |
| Win Rate | — | — | **100%** (15/15) |
| Output Variance | — | — | **-32%** |
Key finding: effectiveness scales with task complexity — the harder the task, the greater the improvement (+23.8 Basic, +29.6 Advanced, +36.2 Expert).
**Exact phrasing to use everywhere:** +60% avg quality (49.5 → 79.3), 15/15 win-rate, −32% variance (n=15, author-measured A/B, third-party replications pending).
> Full paper: *Hwang, M. (2026). Harness: Structured Pre-Configuration for Enhancing LLM Code Agent Output Quality.*
## Requirements
- [Agent Teams enabled](https://code.claude.com/docs/en/agent-teams): `CLAUDE_CODE_EXPERIMENTAL_AGENT_TEAMS=1`
## FAQ
Q1. Isn't "+60%" oversold?
**A.** The +60% figure comes from an **author-measured A/B (n=15, 15 tasks, measured on the sister repo `claude-code-harness`)**. Every citation in this repo pairs the number with the disclosure "n=15, author-measured, third-party replications pending" in the same sentence. For adoption decisions, we recommend running a 2–4 week internal pilot and measuring your own numbers.
**Evidence:**
- Author A/B: [revfactory/claude-code-harness](https://github.com/revfactory/claude-code-harness)
- Paper: *Hwang, M. (2026). Harness: Structured Pre-Configuration for Enhancing LLM Code Agent Output Quality*
Q2. Why "harness factory" and not "harness builder"? Isn't this competing with Archon?
**A.** Archon generates deterministic runtime configurations — it's a **Runtime-Configuration Factory**. Harness generates agent team architectures (team structure, message protocols, review gates) — it's a **Team-Architecture Factory**. They are **neighbor sub-layers of the same L3 Meta-Factory** and serve different needs. Pick Archon for runtime determinism, Harness for team-architecture patterns, or combine them (design architecture with Harness → deploy runtime with Archon).
**Evidence:**
- Archon self-definition: [clawfit docs/reference-levels.md](https://github.com/hongsw/clawfit/blob/main/docs/reference-levels.md)
- Sub-layer declaration: see the **Category — Where Harness Sits** section above
- Archon repo: [github.com/coleam00/Archon](https://github.com/coleam00/Archon)
Q3. Isn't "Claude Code only" too narrow? What about Gemini/Codex?
**A.** Currently the official runtime is Claude Code only. A Codex port of the same concept — [SaehwanPark/meta-harness](https://github.com/SaehwanPark/meta-harness) — is already public, so Codex teams can start there. Harness chose "Claude-Code-native, deep" over "multi-runtime, shallow"; cross-runtime collaboration with sibling repos (meta-harness, harness-init, OpenRig) is on the roadmap.
**Evidence:**
- Codex port: [github.com/SaehwanPark/meta-harness](https://github.com/SaehwanPark/meta-harness)
- Cross-runtime scaffolder: [github.com/Gizele1/harness-init](https://github.com/Gizele1/harness-init)
## License
Apache 2.0
