Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx skills add pproenca/dot-skills --skill harness-engineeringgit clone --depth 1 https://github.com/pproenca/dot-skillsWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/pproenca/dot-skills/harness-engineering)<a href="https://agentmods.dev/skills/pproenca/dot-skills/harness-engineering"><img src="https://agentmods.dev/badge/skills/pproenca/dot-skills/harness-engineering.svg" alt="Measured on agentmods" height="20"></a>What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00207 | $0.04691 |
| Opus 5 | $0.00103 | $0.02346 |
| Sonnet 5 | $0.00041 | $0.00938 |
| Haiku 4.5 | $0.00021 | $0.00469 |
Grade A, and why
harness-engineering scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 3d ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
How it starts
The opening of the file, as written. The whole thing — 460 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Harness: Agent-First Engineering Scaffolding
The harness is the scaffolding that makes coding agents effective in a repository. It encodes the knowledge, boundaries, and rules that an agent needs to reason about the full business domain directly from the repo itself.
The philosophy: agents execute, humans steer. The engineer's job is not to write code but to design environments, specify intent, and build feedback loops. The harness is what makes this possible.
Why It Matters
From the agent's point of view, anything it can't access in-context while running effectively doesn't exist. Slack discussions, Google Docs, tacit team knowledge — all invisible. The harness makes this knowledge legible by encoding it as repository-local, versioned artifacts.
A well-harnessed repo gives agents:
- A map (AGENTS.md) — where to look, not what to memorize
- Boundaries (domain specs) — what can depend on what
- Rules (golden principles) — taste encoded as enforceable invariants
- Quality baselines (scoring) — where the gaps are
Without this scaffolding, agents replicate whatever patterns they find — including bad ones. The harness is what prevents entropy from compounding.
Harness Maturity Model
The harness is built incrementally. Each level builds on the previous — don't try to jump from Level 0 to Level 4 in one pass. Assess the current level and build toward the next.
| Level | Name | What it enables | Key artifacts |
|---|---|---|---|
| 0 | Unharnessed | Agents guess everything — no map, no rules | Nothing |
| 1 | Map | Agents know where to look and what the codebase does | AGENTS.md, ARCHITECTURE.md, docs/ |
| 2 | Rules | Agents know what's allowed and what isn't | .harness/principles.yml, enforcement.yml, domains.yml |
| 3 | Feedback | Agents self-correct via quality signals and process patterns | .harness/quality.yml, doc-gardening, GC sweeps |
| 4 | Autonomy | Agents operate independently with defined escalation boundaries | Worktree isolation, escalation rules, agent-to-agent review |
What ships with it
9 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
- metadata.json 1.1 KB
- references/architecture-layer.md 11 KB
- references/assessment.md 5.5 KB
- references/core-beliefs.md 5.6 KB
- references/enforcement-layer.md 7.9 KB
- references/knowledge-layer.md 8.1 KB
- references/process-patterns.md 8.5 KB
- references/quality-scoring.md 3.6 KB
- references/yml-schemas.md 12 KB
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 3d ago First seen · 460 lines · 207 tokens per session scan A f03bdc76a481
harness-engineering is a skill published in the GitHub repository pproenca/dot-skills (203 stars, last pushed 22d ago), licensed MIT. It adds 207 tokens to every session and 4,691 once invoked, about $0.0010 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-03.
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