git:20260603.4031ba1 to git:20260610.fa97770

11 added, 8 removed. Audit A to A.

---

name: prompt-regression

description: Detects harness regressions by running standard prompt probes after rule/skill changes and comparing outputs against saved baselines. Triggers on "prompt regression", "did my changes break anything", "regression check", "test harness changes".

user-invocable: true

allowed-tools: ["Read", "Bash", "Glob", "Grep"]

model: sonnet

complexity_routing:

base: sonnet

high: opus

escalate_when:

- full_suite

- cross_skill_impact

---

# prompt-regression — Harness Regression Detection

After CLAUDE.md edits, rule changes, or new skill additions, harness behavior can silently regress. This skill runs a lightweight probe suite against the changed assets and compares outputs against saved baselines to surface regressions before they reach production.

> **Scope distinction**

> - harness-doctor: structural completeness (files, links, drift)

> - prompt-regression: **behavioral correctness** — did the change alter expected AI response patterns?

---

## Triggers

- `/prompt-regression`

- "prompt regression", "regression check", "regression test"

- "did my rule change break anything", "test harness changes", "verify harness behavior", "make sure my edit didn't change behavior"

- After significant CLAUDE.md edits or new skill commits

---

## Execution Steps

### Step 1. Identify Changed Assets

```bash

# What changed since last commit (or last N commits)

git diff HEAD~1 --name-only -- CLAUDE.md .claude/ plugins/

```

Classify each changed file:

- `CLAUDE.md` → **core behavior** (high impact)

- `.claude/rules/*.md` → **rule layer** (medium impact)

- `plugins/*/skills/*/SKILL.md` → **skill behavior** (scoped impact)

- `plugins/*/skills/*/SKILL.md` (trigger phrases changed) → **trigger routing** (high impact)

If no changes detected: report "No harness changes since last commit — regression check skipped."

---

### Step 2. Load Probe Suite

Check for custom probes:

```bash

ls .claude/regression/probes.md 2>/dev/null || echo "NO_CUSTOM_PROBES"

```

- **If custom probes exist**: load and use them.

+ **If custom probes exist**: load and use them. The hub repo ships its golden probe set

+ (known-answer offline eval, 28 probes with check classes) at exactly this path — when

+ present it is canonical and supersedes the default matrix below.

- **If no custom probes**: use the default probe matrix below.

+ **If no custom probes** (e.g. Mode C install without the hub repo): use the default

+ probe matrix below.

#### Default Probe Matrix

|---|---|---|---|

| `P-CHAIN-01` | `/field-harvest` | harvest-loop close-chain referenced (wrap-up deferred to CLAUDE.md session-close chain — field-harvest has no inline sim-conductor gate) | field-harvest SKILL.md |

---

### Step 3. Map Changes → Affected Probes

| Changed File | Affected Probes |

|---|---|

| `CLAUDE.md` §Onboarding | P-GREET-01 |

| `CLAUDE.md` §Autonomous Initiative | P-TRIGGER-* |

| `CLAUDE.md` §Wrap-up | P-CLOSE-01 |

| `CLAUDE.md` §New Skill Gate | P-GATE-01 |

| `plugins/fh-meta/skills/*/SKILL.md` | P-CHAIN-* matching skill |

If change scope is `CLAUDE.md` core (10+ lines changed): run **full suite** (all probes).

---

### Step 4. Run Affected Probes

For each affected probe, evaluate:

**4-a. Trigger routing check** — Does the trigger phrase still map to the expected skill/behavior?

- Read the changed file

- Locate trigger section

- Confirm the probe's input pattern still appears in the trigger list

**4-b. Chain integrity check** — Are mandatory chains still present?

- For skill chains: confirm `→ chain:` or `Mandatory:` gate lines exist

- For session close chain: confirm all 4 steps in CLAUDE.md §Wrap-up

**4-c. Gate presence check** — Are gate conditions still enforced?

- - Pre-commit gate: confirm all 5 items present in CLAUDE.md

+ - Pre-commit gate: confirm all 6 items present in CLAUDE.md (incl. check-class declared)

- Conditional-pass gate: confirm `CONDITIONAL_PASS` logic in affected SKILL.md

Output per probe:

```

[PASS] P-TRIGGER-01 — plugin-recommender trigger phrase found in CLAUDE.md

[FAIL] P-CHAIN-01 — field-harvest SKILL.md no longer references the harvest-loop close chain after edit

[SKIP] P-GREET-01 — §Onboarding not in changed files

```

---

### Step 5. Regression Report

```

## Prompt-Regression Report — YYYY-MM-DD

### Changed Assets

- CLAUDE.md (§Autonomous Initiative — 3 trigger phrases modified)

- plugins/fh-meta/skills/field-harvest/SKILL.md

### Probes Run: 4 | Pass: 3 | Fail: 1 | Skip: 4

### FAIL Details

|---|---|---|---|

### Verdict

⚠️ REGRESSION DETECTED — 1 probe failed. Fix required before merge.

```

If all probes pass:

```

✅ NO REGRESSION — All N probes passed. Safe to merge.

```

---

### Step 6. Baseline Update (on explicit user approval)

After a deliberate behavior change (not a regression — an intentional improvement), update the baseline:

```bash

# Baseline stored as markdown in .claude/regression/

mkdir -p .claude/regression

# Write updated probe expectations

```

Prompt user: *"Probe P-CHAIN-01 now expects the new gate format. Update baseline? (y/n)"*

Only update on explicit `y` — never auto-update.

---

## Done When

- - All affected probes are evaluated (PASS / FAIL / SKIP)

- - Regression report is output with clear PASS/FAIL verdict

- - If FAIL: specific file + line fix is recommended

- - Baseline updated only on explicit user approval

+ - All affected probes are evaluated (PASS / FAIL / SKIP) — class: mandatory-pass

+ - Regression report is output with clear PASS/FAIL verdict — class: mandatory-pass

+ - If FAIL: specific file + line fix is recommended — class: judged, paired with verify-bidirectional (the fix recommendation is re-checked, not trusted as-is)

+ - Baseline updated only on explicit user approval — class: mandatory-pass (HITL)

---

## Chains

**Upstream** (runs before this skill):

- Automatically triggered after significant harness commits (Step 1 detects via git diff)

**Downstream** (runs after FAIL verdict):

- → `harness-doctor` for structural fixes if L1/L2 issues found

- → `verify-bidirectional` to confirm fix resolved the regression