Harden skill
Portable, single-purpose skills for coding agents that orient, map, plan, review, and reason over your code — read / plan / report, never editing behind your back.
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What its author says it does
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Use when an agent needs to harden a skill's instructions so they reliably change agent behavior; diagnoses each intended behavior's baseline failure, matches it to the right instruction form, hardens discipline rules against rationalization, and specifies a micro-test protocol rather than editing the skill or running the tests itself.
SKILL.md
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Harden a skill
Use this skill to make a skill's wording bind. Authoring a skill is only half done when the prose reads well; the other half is whether an agent under load actually does what the prose intends. This skill finds where the guidance will fail under pressure or be rationalized away, and prescribes the instruction form that holds.
Governing intuition: you cannot harden a behavior you have not named, and you should not add guidance for a failure you have not seen. State the behavior each passage is trying to produce, the failure an agent falls into without it, and match the form to that failure — do not reach for a prohibition by reflex.
It produces a hardening plan: per-behavior verdicts, recommended rewrites, and a verification protocol the agent (or user) then applies as a separate act.
Input: the skill instructions under authoring or revision — a SKILL.md (draft or existing), a specific rule or section, or a proposed wording change; if none is given, ask which skill or passage to harden.
Boundary: diagnoses and prescribes only — produces a hardening plan; does not edit the target skill or run the tests.
Workflow
Phase 1: Inventory the intended behaviors
Walk the target prose and, for each passage of guidance, write one line: what agent behavior is this trying to produce? Guidance that maps to no concrete behavior is decoration — flag it. A passage may carry several behaviors; split them, because different behaviors may need different forms.
Phase 2: Classify each baseline failure
For each behavior, name what an agent naturally does without this guidance — the baseline failure. This is the crux: the form that bulletproofs one failure type backfires on another. Sort each into one type:
| Failure type | Signature |
|---|---|
| Discipline violation | Agent knows the rule and skips it under pressure (time, sunk cost, authority, exhaustion) |
| Wrong-shaped output | Agent complies, but the output has the wrong shape (buried verdict, bloated prompt, restated input) |
| Omitted element | Agent leaves out a required part of something it already produces |
| Condition-dependent | The correct behavior depends on a predicate the agent must first observe |
If you cannot state a plausible baseline failure for a behavior, that behavior may need no guidance at all — say so rather than inventing a rule.
Phase 3: Match the form to the failure
Prescribe the form that fits each failure type, and flag any current wording whose form is mismatched (it will backfire, not just underperform). Load references/hardening.md for the full table with examples and the evidence behind it.
| Baseline failure | Right form | Backfiring form |
|---|---|---|
| Discipline violation | Prohibition + rationalization table + red-flags list | Soft guidance ("prefer…", "consider…") |
| Wrong-shaped output | Positive recipe / contract: name the output's parts, in order | Prohibition list ("don't restate", "never narrate") |
| Omitted element | Structural REQUIRED slot in the template they fill in | Prose reminder near the template |
| Condition-dependent | Conditional keyed to an observable predicate | Unconditional rule + exemption clauses |
Phase 4: Harden discipline rules against rationalization
Only for discipline-violation behaviors. For each, load the toolkit in references/hardening.md and produce: the specific loopholes to close explicitly, a rationalization table (excuse → reality) drawn from the baseline, a red-flags self-check list, and a spirit-vs-letter clause. Do not apply this prohibition toolkit to shape or omission failures — there it measurably backfires.
Phase 5: Specify the verification
No rewrite ships on faith. Specify a micro-test for the changed wording:
- Fresh-context samples — system prompt = the realistic context the guidance lives in (the full skill, not the clause alone); user message = a task that tempts the failure.
- A no-guidance control is mandatory. If the control does not exhibit the failure, there is nothing to fix — drop the guidance.
- 5+ reps per variant; single samples lie. Read every flagged match by hand (template echoes and quoted counter-examples masquerade as hits).
- Variance is a metric — five different interpretations across five reps means the wording is not binding yet.
For discipline skills, full pressure scenarios (combined time + sunk-cost + authority) are the final gate after micro-tests pass. This protocol is executed as a separate step after the hardening plan ships — where the host has subagent tools the agent can run it then; otherwise hand it to the user. Keep this dependency out of the target skill's core workflow.
Output Format
# Hardening Plan — [skill or passage]
**Scope**: [what was hardened]
| Intended behavior | Baseline failure | Failure type | Current form | Verdict | Prescribed form |
|---|---|---|---|---|---|
| … | … | discipline / shape / omission / conditional | … | binds / will backfire / untested | … |
## Recommended rewrites (not applied)
- [behavior] → concrete wording in the prescribed form.
## Discipline hardening (discipline rules only)
- Loopholes to close · rationalization-table entries · red-flags list · spirit-vs-letter clause.
## Verification protocol
- Micro-test spec (system prompt, tempting task, no-guidance control, 5+ reps).
- Pressure scenarios — discipline skills only.
## Open assumptions
- [Behaviors whose baseline failure was assumed rather than observed.]
Rules
- Read-only. Recommend wording and tests; do not edit the target skill or run the tests as part of this skill — the agent applies them as a separate, explicit step.
- Name a baseline failure for every behavior. A behavior with no plausible failure needs no guidance; put it under open assumptions, do not manufacture a rule.
- Do not reach for a prohibition by default. Prohibitions bind discipline failures and backfire on shape and omission failures.
- No nuance clauses, no exemption clauses. "Don't X unless it matters" and "this doesn't apply to Y" both reopen the negotiation — express a real exception as its own conditional on an observable predicate, or restructure so the rule cannot reach the exempt part.
- Every micro-test includes a no-guidance control; guidance that beats nothing is the only guidance worth keeping.
- Stay in lane. To decide whether a skill should exist or what shape it takes at all, point to
scope-new-skill; to test whether governance prose should become enforcement elsewhere, point toaudit-governance. Structural and mechanical checks (frontmatter, links, naming) are covered byscripts/validate_skills.py, not by this skill — hardening is about whether the wording binds.