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 tienenwu/fables --skill harness-writinggit clone --depth 1 https://github.com/tienenwu/fablesWrote 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/tienenwu/fables/harness-writing)<a href="https://agentmods.dev/skills/tienenwu/fables/harness-writing"><img src="https://agentmods.dev/badge/skills/tienenwu/fables/harness-writing/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/tienenwu/fables/harness-writing"><img src="https://agentmods.dev/badge/skills/tienenwu/fables/harness-writing.svg" alt="Reviewed on agentmods" width="80" 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 | $0.00033 | $0.01413 |
| Opus 5 | $0.00016 | $0.00707 |
| Sonnet 5 | $0.00007 | $0.00283 |
| Haiku 4.5 | $0.00003 | $0.00141 |
Grade A, and why
harness-writing 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 9d 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 — 91 lines — stays where its author put it; the contents beside it link to each section on GitHub.
🌐 繁體中文（canonical） · English mirror
Harness Writing — Generate a Repository-Specific Evidence-Driven Workflow
Core Model
The Harness is the sole orchestration kernel: the always-on kernel keeps only routing and invariants while standard/high-risk details load on demand; risk conditions and claim→evidence gates control state transitions, and evidence does not mean creating a repository artifact every time. Profiles select required states; adapters describe available capabilities; contracts retain project judgments; domain playbooks provide techniques inside a state.
Do not reinvent invariants or invent project parameters. File count is only a supporting signal; route primarily by reversibility, blast radius, ambiguity, external side effects, and verifiability.
When to Use
- A new project needs a Harness, contract index, and mechanical-check baseline.
- An existing project needs AI workflow adoption or recalibration.
- An existing Harness needs an audit for dual sources of truth, fake evidence, review ceremony, or contract pollution.
- Not for adding one already-decided project contract; edit it through the existing lifecycle.
Generation Workflow
1. Discover (read-only)
- Inventory structure, CI, existing rules, integration points, public interfaces, production resources, and release paths.
- Assess side effects before build/test/lint; run each safe command once and record duration, output, and baseline failures. Do not run commands that may write production resources; record the limitation.
- Inventory capabilities rather than product names: isolated writes, shell execution, tests, fresh reviewers, persistent artifacts, and access to another model family.
- Derive every quick eligibility condition and absolute high-risk trigger from real project evidence. Do not manufacture precision with numeric totals; record absent items as "none."
- If a Harness exists, modify it instead of generating a second one.
What ships with it
3 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.
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.
- 9d ago First seen · 91 lines · 33 tokens per session scan A 8528d03fa8bb
harness-writing is a skill published in the GitHub repository tienenwu/fables (4 stars, last pushed 1mo ago), licensed MIT. It adds 33 tokens to every session and 1,413 once invoked, about $0.0002 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 2026-08-31.
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