Harness Creator
Use this skill to make a repository easier for coding agents to start, stay in scope, verify work, and resume across sessions. Keep the harness small enough that agents actually follow it.
Not for model selection, prompt tuning in isolation, chat UI design, or general app architecture.
Core Model
Every useful coding-agent harness has five subsystems:
| Subsystem | Minimal artifact | Purpose |
|---|---|---|
| Instructions | AGENTS.md or CLAUDE.md |
Startup path, working rules, definition of done |
| State | feature_list.json, progress.md |
Current feature, status, evidence, next step |
| Verification | init.sh or documented commands |
Tests/checks the agent must run before claiming done |
| Scope | Feature dependencies and done criteria | Prevents overreach and half-finished work |
| Lifecycle | session-handoff.md, end-of-session routine |
Makes the next session restartable |
First Move
- Inspect what already exists: instruction files, feature/state files, verification commands, docs, package manifests.
- Ask only for missing context that cannot be inferred safely: target agent, desired file name, tolerance for structure, and whether overwriting is allowed.
- Prefer a minimal harness first. Add memory, tool safety, multi-agent, or benchmark details only when the user's problem calls for them.
Common Tasks
Create a harness
Use the bundled script when working on a local repository:
node skills/harness-creator/scripts/create-harness.mjs --target /path/to/project
Options:
--agent-file CLAUDE.mdfor Claude-oriented projects.--package-manager npm|pnpm|yarn|bunwhen detection is wrong.--commands "cmd one,cmd two"for custom verification.--forceonly after confirming overwrites are acceptable.
Then explain what was created and how the user should replace placeholder feature entries.
Audit an existing harness
Run:
node skills/harness-creator/scripts/validate-harness.mjs --target /path/to/project
Report the five subsystem scores, the lowest-scoring area, and the first 2-3 changes that would improve reliability. Treat the lowest score as a candidate bottleneck; confirm with failures, logs, or task outcomes before claiming causality.
Produce a report
Use when the user wants a shareable assessment:
node skills/harness-creator/scripts/render-assessment-html.mjs --target /path/to/project
node skills/harness-creator/scripts/run-benchmark.mjs --target /path/to/project --html /path/to/report.html
Be clear that this is a structural benchmark. Real effectiveness still needs before/after agent sessions on representative tasks.
When to Read References
Load only the reference needed for the user's problem:
- Memory across sessions: Memory Persistence
- Reusable workflows as skills: Skill Runtime
- Permissions, tools, concurrency: Tool Registry & Safety
- Context budget and progressive disclosure: Context Engineering
- Delegation and parallel agents: Multi-Agent Coordination
- Hooks, startup, long-running work: Lifecycle & Bootstrap
- Non-obvious failure modes: Gotchas
Design Rules
- Keep the root instruction file short: routing and invariants, not a full manual.
- Put project facts in project docs, not in the skill.
- Make verification commands explicit and runnable.
- Require evidence before marking a feature done.
- Use one active feature unless the harness has explicit multi-agent ownership boundaries.
- Prefer append/update state files over relying on chat history.
- Never hide destructive behavior in scripts; overwrites require explicit user approval.
Deliverable Checklist
For a usable minimal harness, leave the target project with:
-
AGENTS.mdorCLAUDE.md -
feature_list.json -
progress.md -
init.sh - Optional
session-handoff.mdfor multi-session work - Documented verification evidence or next action
If you cannot create files, provide exact file contents and commands instead.
Source: walkinglabs/learn-harness-engineering — distributed by TomeVault.