# Harness > 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. - Skill: `greatsumini/harness` (Agent Skill, multi-file: 6 files) - Install (CLI): `npx skillmds@latest add greatsumini/harness` - Raw SKILL.md: https://api.skillmd.com/api/skills/greatsumini/harness/raw - Safety review: pending - Works with: Claude Code, Claude.ai, OpenAI Codex - Category: AI & ML - Author: greatsumini (https://skillmd.com/u/greatsumini) - Updated: 2026-09-17 - Page: https://skillmd.com/skills/greatsumini/harness --- # 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 `$ARGUMENTS`. Execute each phase by spawning a sub-agent using the **Agent tool**. Get explicit user approval before advancing to the next phase. --- ## Orchestration Flow ### Step 0: Initialize Create `.harness/artifacts/` directory if it doesn't exist: ```bash mkdir -p .harness/artifacts ``` ### Step 1: Clarify Phase Spawn a sub-agent with the following: - **description**: "Clarify phase - surface questions" - **prompt**: Read the instructions from `.claude/skills/harness/phases/01-clarify.md` and include `$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: ```markdown # 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.