harness

name	harness
description	Structured development harness that guides feature implementation through 5 phases — Clarify, Context Gather, Plan, Generate, Evaluate. Each phase runs as an independent sub-agent that produces artifacts for the next phase. Use this skill when starting a new feature, building a project from scratch, or implementing a complex requirement that benefits from structured planning before coding. Triggers on phrases like "build me X", "implement X", "new feature", "create an app that", or when the user explicitly invokes /harness.
disable-model-invocation	true
user-invocable	true
argument-hint	["feature description"]

Development Harness — Orchestrator

A structured 5-phase workflow where each phase is executed by an independent sub-agent. Artifacts flow between phases via .harness/artifacts/.

Overview

Phase 1: Clarify      → Sub-Agent → artifacts/01-clarify.md
Phase 2: Context      → Sub-Agent → artifacts/02-context.md
Phase 3: Plan         → Sub-Agent → artifacts/03-plan.md + phases.json + tasks.json
Phase 4: Generate     → Sub-Agent (per phase) → artifacts/04-generate.md
Phase 5: Evaluate     → Sub-Agent → artifacts/05-evaluate.md

Artifact Pipeline

Each sub-agent reads previous phase artifacts and produces its own. All artifacts live in .harness/artifacts/.

01-clarify.md ──→ 02-context.md ──→ 03-plan.md ──→ 04-generate.md ──→ 05-evaluate.md
                                     phases.json
                                     tasks.json

How to use

The user provides a feature description as $ARGUMENTS. Execute each phase by spawning a sub-agent using the Agent tool. Get explicit user approval before advancing to the next phase.

---

Orchestration Flow

Step 0: Initialize

Create .harness/artifacts/ directory if it doesn't exist:

mkdir -p .harness/artifacts

Step 1: Clarify Phase

Spawn a sub-agent with the following:

• description: "Clarify phase - surface questions"
• prompt: Read the instructions from .claude/skills/harness/phases/01-clarify.md and include $ARGUMENTS as the $FEATURE_DESCRIPTION. Tell the agent to write its output to .harness/artifacts/01-clarify.md.

After the agent completes:

1. Read .harness/artifacts/01-clarify.md and present the questions to the user
2. Wait for the user's answers
3. Update .harness/artifacts/01-clarify.md — fill in the "User Decisions" section with the user's answers

Gate: Wait for explicit user approval before proceeding.

Step 2: Context Gather Phase

Spawn a sub-agent with the following:

• description: "Context gather - scan codebase"
• prompt: Read the instructions from .claude/skills/harness/phases/02-context.md. The agent should read .harness/artifacts/01-clarify.md as input and write its output to .harness/artifacts/02-context.md.

After the agent completes:

1. Read .harness/artifacts/02-context.md and present the summary to the user

Gate: Wait for explicit user approval before proceeding.

Step 3: Plan Phase

Spawn a sub-agent with the following:

• description: "Plan phase - create execution plan"
• prompt: Read the instructions from .claude/skills/harness/phases/03-plan.md. The agent should read .harness/artifacts/01-clarify.md and .harness/artifacts/02-context.md as input, then produce:
  • .harness/phases.json
  • .harness/tasks.json
  • .harness/artifacts/03-plan.md

After the agent completes:

1. Read .harness/artifacts/03-plan.md and present the plan summary table to the user
2. If the user requests changes, spawn the Plan agent again with the feedback

Gate: Wait for explicit user approval before proceeding.

Step 4: Generate Phase

This phase runs one sub-agent per execution phase defined in .harness/phases.json.

For each phase in phases.json (in order):

1. Spawn a sub-agent with the following:

   • description: "Generate phase - {phase_name}"
   • prompt: Read the instructions from .claude/skills/harness/phases/04-generate.md. Set $PHASE_ID to the current phase ID (e.g., "phase-1"). The agent should read all previous artifacts and implement only the tasks in that phase. It should update tasks.json statuses and append to .harness/artifacts/04-generate.md.

2. After the agent completes, briefly report progress to the user:

   • Which tasks were completed
   • Current overall progress (e.g., "Phase 2/6 complete, 4/9 tasks done")

3. Initialize .harness/artifacts/04-generate.md with a header before the first generate sub-agent:

   # Phase 4: Generate — Artifact
   

Note: Each generate sub-agent runs sequentially (phase by phase), but tasks within a phase that have no inter-dependencies can be implemented in parallel by the agent.

Gate: After ALL phases are generated, wait for user approval before proceeding to evaluation.

Step 5: Evaluate Phase

Spawn a sub-agent with the following:

• description: "Evaluate phase - verify output"
• prompt: Read the instructions from .claude/skills/harness/phases/05-evaluate.md. The agent should read all artifacts, run available checks, verify acceptance criteria, fix errors, and write results to .harness/artifacts/05-evaluate.md.

After the agent completes:

1. Read .harness/artifacts/05-evaluate.md and present the results to the user
2. If there are remaining issues, report them clearly

---

Error Handling

• If a sub-agent fails or reports a blocker, present the issue to the user and ask how to proceed
• If a sub-agent's artifact is missing or malformed, re-run the phase
• The user can always say "redo phase N" to re-run any specific phase

State Management

All harness state lives in .harness/ at the project root:

.harness/
├── artifacts/
│   ├── 01-clarify.md      # Phase 1 output: questions + user decisions
│   ├── 02-context.md      # Phase 2 output: codebase context
│   ├── 03-plan.md         # Phase 3 output: plan summary
│   ├── 04-generate.md     # Phase 4 output: generation log
│   └── 05-evaluate.md     # Phase 5 output: evaluation results
├── phases.json            # Phase definitions (from Phase 3)
├── tasks.json             # Task definitions with status (from Phase 3)
└── log.md                 # Legacy execution log (optional)

This directory can be safely deleted after the feature is complete, or kept for reference.