Harness

---
name: mk:harness
version: 1.0.0
preamble-tier: 3
description: >-
  Use when running an autonomous multi-hour build of a green-field product —
  orchestrates planner → contract → generator ⇄ evaluator loop with adaptive
  scaffolding density per model tier. Triggers on /mk:harness, "build me a
  kanban app", "build a retro game maker", "autonomous build", or any
  green-field product spec. NOT for scoped single-task work (see mk:cook);
  NOT for initial project scaffolding only (see mk:bootstrap).
argument-hint: "[task description] [--tier auto|full|lean|minimal] [--max-iter N] [--budget USD] [--tdd]"
allowed-tools:
  - Bash
  - Read
  - Edit
  - Write
  - Grep
  - Glob
  - Agent
  - AskUserQuestion
source: local
keywords: [harness, autonomous-build, green-field, generator-evaluator, harness-contract, adaptive-density]
when_to_use: "Use when running an autonomous multi-hour build of a green-field product (planner→contract→generator⇄evaluator loop). NOT for scoped single-task work (see mk:cook) or initial scaffolding only (see mk:bootstrap)."
user-invocable: true
meowkit:
  portability: provider-only
  providers:
    include: [claude-code]
  requires:
    surfaces: [skills]
    commands: [Agent, AskUserQuestion, Bash]
    env: [CLAUDE_PROJECT_DIR]
  context_cost: high
---

# mk:harness — Autonomous Multi-Hour Build Orchestration

Step-file workflow that runs the complete generator/evaluator harness pipeline as an autonomous build. Handles green-field product builds (Phase 1 product-level plan → Phase 4 sprint contract → Phase 3 evaluator loop → ship decision) with adaptive scaffolding density based on detected model tier.

## When to Use

Activate when:
- User runs `/mk:harness "build a X"` (or any green-field product description)
- Existing kit detection routes a green-field "build me an app" intent here instead of `mk:cook`
- A multi-hour autonomous build is requested with no manual handholding

Skip when:
- The task is a single feature, bug fix, or refactor → use `/mk:cook` instead
- The task is a doc update → use the existing doc skills
- The request is "explain X" or "review Y" → use the appropriate single-shot skill

## Hard Constraints

1. **Adaptive density** — picks scaffolding density via `mk:scale-routing` (or `density-select.sh`); honors `MEOWKIT_HARNESS_MODE` env override
2. **Budget caps** — warns at $30 spent, requires explicit approval at $100, hard-blocks at user-set `--budget` value
3. **6-hour wall-clock timeout** — hard limit per Anthropic's observed runs <!-- research-citation -->; checkpoints every step for resumability
4. **Max 3 iteration rounds** between generator and evaluator before escalating to human (configurable via `--max-iter`)
5. **Run report mandatory** — every harness run produces `tasks/harness-runs/YYMMDD-{slug}/run.md` with full audit trail
6. **Coexists with `mk:cook`** — does not replace it; both route through Gate 1 + Gate 2
7. **TDD opt-in (parallel to cook):** harness respects `--tdd` like other flows. Default: no RED-phase gate. With `--tdd`: writes the `.claude/session-state/tdd-mode` sentinel and the developer waits on tester before each generator iteration. Active-verification HARD GATE (Rule 8 of `harness-rules.md`) is independent of TDD mode and always applies.

## Workflow

Execute via `workflow.md`. Step-file architecture — load one step at a time.

```
Step 0: Tier Detection      → call mk:scale-routing; pick density (MINIMAL|FULL|LEAN)
Step 1: Plan                → invoke mk:plan-creator --product-level
Step 2: Contract            → invoke mk:sprint-contract (skipped if LEAN + small)
Step 3: Generate            → spawn developer subagent w/ 4-subphase pattern
Step 4: Evaluate            → invoke mk:evaluate
Step 5: Iterate or Ship     → PASS → shipper; FAIL → loop to step-3 (max --max-iter)
Step 6: Run Report          → write the audit trail
```

## Density Modes

| Mode | Tier | Planner | Contract | Iteration Loop | Context Reset |
|---|---|---|---|---|---|
| **MINIMAL** | TRIVIAL (Haiku) | Skip (use plan-creator --fast) | Skip | Skip | Skip |
| **FULL** | STANDARD (Sonnet) / COMPLEX (Opus 4.5) | Required | Required | 1–3 rounds | Optional |
| **LEAN** | COMPLEX (Opus 4.6+) | Required | Optional | 0–1 rounds | Skip (auto-compact) |

## Run Report Schema

Every run writes `tasks/harness-runs/YYMMDD-{slug}/run.md`:

```markdown
---
run_id: 260408-1450-build-todo
density: LEAN
model: opus-4-6
budget_cap: 50
budget_spent: 12.40
iterations: 1
status: PASS | WARN | FAIL | ESCALATED | TIMED_OUT
started: 2026-04-08T14:50:00Z
ended: 2026-04-08T15:18:00Z
---

# Harness Run — {task description}

## Density Decision
- Detected tier: {tier}
- Detected model: {model-id}
- Density: {MINIMAL|FULL|LEAN}
- Source: scale-routing | env-override | --tier flag

## Per-Step Artifacts
- step-00: {tier-detection result}
- step-01: tasks/plans/{plan-dir}/plan.md
- step-02: tasks/contracts/{contract}.md (or "skipped — LEAN small sprint")
- step-03: handoff at tasks/handoff/{slug}-sprint-1.md
- step-04: verdict at tasks/reviews/{slug}-evalverdict.md
- step-05: iteration count + final action
- step-06: this file

## Budget Trail
| Step | Spent | Cumulative |
|---|---|---|
| ... | ... | ... |

## Final Verdict
{PASS/FAIL/ESCALATED summary + next action}
```

## Gotchas

- **Don't run on a non-green-field task.** Use `mk:cook` for single features, bug fixes, refactors. The harness is for "build me an app" scope.
- **Density override stays in scope.** `MEOWKIT_HARNESS_MODE=LEAN` does NOT skip Gate 2. Review verdict is still mandatory before ship.
- **Iteration loops are bounded.** Max 3 by default. After round 3, escalate — don't keep iterating blindly.
- **Budget check is authoritative.** If `budget-tracker.sh` says block, the harness halts even mid-iteration.
- **Run reports are append-only.** Don't edit prior steps' entries — the report is the audit trail.
- **Resumable.** If the harness is killed mid-run, `/mk:harness --resume {run-id}` picks up at the last completed step.

## References

| File | Purpose |
|---|---|
| `workflow.md` | Step sequence + variable table |
| `step-00-tier-detection.md` | Density selection via scale-routing |
| `step-01-plan.md` | Product-level planning |
| `step-02-contract.md` | Sprint contract negotiation |
| `step-03-generate.md` | Developer subagent dispatch with 4-subphase pattern |
| `step-04-evaluate.md` | Evaluator dispatch |
| `step-05-iterate-or-ship.md` | PASS/FAIL routing + iteration loop |
| `step-06-run-report.md` | Audit trail writer |
| `references/adaptive-density-matrix.md` | Full decision table per tier × model |
| `references/agent-teams-vs-subagents.md` | When to use teams vs file-based subagents |
| `scripts/density-select.sh` | Standalone density selector for scriptable use |
| `scripts/budget-tracker.sh` | Cost-log reader; threshold warnings + hard block |
| `../mk:plan-creator/` | Phase 1 — product-level planner |
| `../mk:sprint-contract/` | Phase 4 — contract negotiation |
| `../mk:rubric/` | Phase 2 — rubric library |
| `../mk:evaluate/` | Phase 3 — behavioral evaluator |
| `../mk:scale-routing/` | Tier + density emission |

## Start

Read and follow `workflow.md`.