---
name: skill-counterfactual-audit
description: >
Audit a skill by running a paired probe — the same task once with the
skill loaded and once without — segment both traces into goal-directed
phases, align phases, and emit a SIP report (surface anchoring,
template copy, excess planning, task recovery, off-task artifact).
Use whenever a skill is created, modified, or proposed for retirement.
Pass-rate is BLIND to most skill effects: CTA (arxiv 2605.11946v1)
shows a single skill can produce 522 measurable behavioural changes
across 49 tasks while pass-rate moves only +0.3%. Triggers: "audit
this skill", "is this skill helping", "retire skill", "before shipping
skill", "behavioural impact of skill X", or any skill review event.
user-invocable: true
version: 1.0.0
format: 2025-10-02
triggers:
- "audit this skill"
- "is this skill helping"
- "behavioural impact of skill"
- "retire this skill"
- "before shipping a skill"
updated: 2026-05-16
status: ACTIVE
source: arxiv 2605.11946v1 (Counterfactual Trace Audit / CTA)
---
# Skill Counterfactual Audit
## Why
When you ship a skill, pass-rate is the easy metric — and it's *blind* to almost everything that matters. CTA (arxiv 2605.11946v1) shows a single skill can produce **522 measurable behavioural changes** across 49 tasks while pass-rate moves only **+0.3%**. The interesting effects (surface anchoring on the skill's vocabulary, template copy without adaptation, excess planning loops, recovery from off-task drift, generation of off-task artifacts) live entirely below pass-rate.
The remedy is a paired-trace audit: run the same probe task twice, with and without the skill, and *compare the behaviours directly* rather than the headline metric.
## How
For each skill under audit:
1. **Curate a probe-task bank** (3-5 small tasks per skill domain). Each task should have:
- A clear goal (a single instruction)
- An expected category of behaviour
- A "phase decomposition" (rough segmentation rules)
2. **Run paired** — same prompt, same task, run A *with* skill loaded, run B *without*.
3. **Segment each trace** — phases like {plan, retrieve, edit, verify, fix-loop, summary}.
4. **Align phases** — match B phases to A phases; mark new/dropped/displaced phases.
5. **Classify SIP (Skill Influence Pattern)** — for each aligned phase, label the effect:
- **surface-anchoring** — A copies vocabulary/structure from the skill itself
- **template-copy** — A reproduces a skill template literally without adaptation
- **excess-planning** — A adds extra planning steps absent in B
- **task-recovery** — A recovers from drift that B falls into
- **off-task-artifact** — A produces artifacts unrelated to the goal
6. **Emit report** to `.planning/patterns/skill-audits/<skill>-<timestamp>.md` with phase comparison table + SIP distribution + retire/refine/keep recommendation.
## Recommendation rule of thumb
| Dominant SIP | Verdict |
|---|---|
| task-recovery + correct artifacts | **keep** (genuine value) |
| surface-anchoring with no task-recovery | **refine** (skill is leaking style, not capability) |
| template-copy on most tasks | **refine** (lower template specificity) |
| off-task-artifact on >25% of probes | **retire** (skill is causing distraction) |
| excess-planning with no completion delta | **refine** (skill adds ceremony) |
## When to skip
- The skill is a workflow guide that doesn't directly shape output (e.g., `loop`, `schedule`) — audit dominant SIPs would always be "task-recovery" trivially.
- No probe-task bank exists for the domain (build one first; defer audit).
- The skill was just created and has no historical baseline. Run the audit when the skill has been active for ≥3 sessions.
## Integration
- `done-retirement` — required gate before retiring a skill.
- `gsd-cleanup` — sweeps audits on a milestone-close cadence.
- Companion to `simplify`, `code-review` — those audit code; this audits skill behaviour.
## Cross-references
- Rosetta concept #9 (Execution-Grounded Selection) — paired-trace audit is the skill-domain instantiation
- College: `agent-systems / integration-evaluation / agent-paired-trace-audit`
- Related skills: `skill-integration` (manages the skill lifecycle that this audits)