mechanism-audit

name	mechanism-audit
description	Audit the **mechanistic experiment rigor** for a specific claim. Catalogue currently has six slots A–F: A (steering coefficient sweep) is implemented; B–F are reserved for future checks (direction extraction quality, site/layer selection, n_effective sufficiency, probe-vs-causal disentanglement, intervention scope). Uses cross-model review (external LLM reviewer via llm-chat MCP). Complementary to `/experiment-audit` (which audits evaluation methodology, not mechanism tuning). The output `overall_verdict` (PASS/WARN/FAIL/N/A) is THIS claim's mechanism-rigor verdict — i.e., whether the interpretability mechanism backing this claim was tuned with the necessary controls. Returns N/A when the claim's experiment does not use any mechanism intervention (e.g., pure dataset evaluation). Does NOT judge methodology honesty (that is `/experiment-audit`'s job) or semantic claim support (that is `/result-to-claim`'s job).
argument-hint	<experiment-dir-or-results-path> — claim <Cx> [— output-dir <path>]
allowed-tools	Bash(*), Read, Write, Edit, Grep, Glob, Agent, mcp__llm-chat__chat

Mechanism Audit: Per-Claim Cross-Model Mechanism-Rigor Verification

Audit the mechanistic-experiment rigor for one claim: $ARGUMENTS

Why This Exists

/experiment-audit audits evaluation methodology — did the experiment honestly measure what it claims to measure (GT provenance, score normalization, file existence, scope, eval type). It treats the interpretability machinery as a black box: if the pipeline runs and the numbers are reported faithfully, it passes. That leaves an entire failure surface unchecked — the mechanism itself can be mis-extracted, mis-sited, mis-scaled, or mis-applied, and the methodology audit will still wave the result through.

This skill is the mechanistic-interpretability domain audit. It asks a different question from /experiment-audit: given that the evaluation was clean, was the mechanism under test actually exercised in a regime where its effect can be measured and trusted? Mechanism rigor spans roughly six dimensions — direction extraction quality, site/layer selection, intervention scaling, control baselines, scope of intervention, and probe-vs-causal disentanglement — which map onto Checks A–F below. Most failures in this vertical do not look like fraud; they look like "the feature doesn't matter," "the random direction beat the learned one," or "specificity fails." The honest evaluation faithfully reports an artifact of an under-tuned mechanism, and downstream readers update on noise.

Each invocation scopes to one claim's runs and returns a PASS/WARN/FAIL/N/A verdict on that claim's mechanism rigor; non-mechanistic claims (e.g., pure dataset evaluation) return N/A and are not penalized downstream.

Core Principle

The executor (Claude) collects file paths scoped to the target claim. The external LLM reviewer reads code and judges mechanism rigor. The executor does NOT participate in the rigor judgment.

This follows shared-references/reviewer-independence.md and mirrors /experiment-audit's reviewer-independence pattern.

Relationship to /experiment-audit

Skill	Audits	Outputs
/experiment-audit	Evaluation methodology honesty (A–F: GT, normalization, file existence, dead code, scope, eval type)	EXPERIMENT_AUDIT.{md,json}
/mechanism-audit	Mechanism / intervention rigor (A: coefficient sweep; B–F reserved)	MECHANISM_AUDIT.{md,json}

Both write into the same per-claim audit directory (e.g., verify/<claim_dir>/main_experiment_audit/). The two verdicts are combined by the caller (e.g., /auto-verify) via combined = max_severity(exp, mech) where fail > warn > pass > n/a. N/A is treated as PASS for the purposes of combination (a claim that doesn't use any mechanism intervention should not be penalized).

Check Catalogue

This catalogue is the single source of truth for what /mechanism-audit audits. Each row declares one check via five fields: Trigger (when does it apply?), Required artifacts (what files does the reviewer need?), Audit questions + Criteria (how is PASS/WARN/FAIL decided?), Evidence (what must the report cite?), and Structured fields (the named slots the reviewer fills in the JSON output). The Workflow below (Steps 2–4) walks this catalogue mechanically.

Extension recipe. Adding a new check requires three template-level edits, all driven by this catalogue:

1. Add a row to the table above + a full five-field subsection below.
2. In Step 4's reviewer prompt, add one more dashed ## Check X block following the same paste-verbatim recipe used for Check A — the loop is mechanical, no per-check logic.
3. In Step 5's report templates (Markdown + JSON), add a per-check section mirroring the new check's Structured fields.

Steps 2–3 (trigger detection + artifact collection) iterate the catalogue and need no code change. The repeated paste-mimicry in Steps 4–5 is intentional: it keeps the LLM prompt and the report schema self-contained and inspectable.

ID	Name	Trigger (one-line)	Required artifacts
A	Steering coefficient sweep	Any additive activation intervention with a scalar coefficient α (steering, CAA, DAS, RepE, SAE feature scaling, activation patching, ROME).	intervention/hook script(s); sweep config or α grid; per-α run outputs with target + capability metrics; direction-extraction site (for the coefficient's unit).
B	Reserved	— (future: direction-extraction quality)	—
C	Reserved	— (future: site / layer selection rationale)	—
D	Reserved	— (future: n_effective sufficiency)	—
E	Reserved	— (future: probe-vs-causal disentanglement)	—
F	Reserved	— (future: intervention scope / multi-site coverage)	—

Check A — Steering coefficient sweep

Trigger keywords / signals — scan EXPERIMENT_PLAN.md's <Cx> methodology section, the filtered <Cx> tracker rows, and scripts referenced by those rows. Check A fires if ANY match:

• plan declarations — any methodology phrasing naming: steering vector, CAA, contrastive activation addition, DAS, interchange intervention, RepE, representation engineering, SAE feature scaling, activation patching, ROME.
• identifier keywords (case-insensitive grep on scripts): steer, steering_vector, \bCAA\b, contrastive_activation, \bDAS\b, interchange, \bRepE\b, representation_engineering, sae_feature, feature_scaling, activation_patch, \bROME\b.
• code patterns: a scalar (commonly alpha, coeff, dose, magnitude) multiplying an additive contribution to a hidden state, e.g. activations += alpha * v, hidden_states[..., site] += alpha * direction, h = h + coeff * steering_vec.

Required artifacts (Step 3 collects these only if triggered):

1. Intervention / hook script(s) implementing the additive update.
2. Sweep config or in-code α grid (yaml / json / Python list literal).
3. Per-α run outputs containing the target metric AND any capability / coherence metric (perplexity, val-acc on an unrelated task, fluency, NaN rate, repetition rate, output-confidence).
4. Direction-extraction code — wherever the steering direction is computed, and wherever the coefficient's unit is established (a raw multiplier on the direction as extracted, a multiple of the site's activation norm, or a projection-std / σ scaling).
5. Sampled post-steering output cases — raw model completions for representative prompts at several α values (especially α = 0, mid-plateau, near-collapse, and the locked α), if logged. These let the reviewer eyeball whether the metric story matches the actual text — e.g., a target-metric "win" at large α paired with repetition / garbled output / off-topic drift indicates the metric is reading OOD collapse as behavior. If too many cases were logged, Step 3 samples a few per α value (e.g. 5 prompts × the α grid).

Audit questions (the reviewer answers all 8):

1. Was a sweep performed (multiple α tried), not a single hardcoded value?
2. Asked only when the run did not meet its target criteria. Did the sweep span a wide, geometrically spaced range — ratio of largest to smallest nonzero |α| ≥ 30× (e.g. [1, 2, 4, 8, 16, 32]) — and include an α = 0 baseline? The ratio is computed on absolute values, so a signed grid such as [−2, −1, 0, 1, 2] scores 2×, not 4×. (Sign coverage — whether the negative direction was tried at all — is not asked by any of the 8 questions; question 8 asks only whether a deliberately asymmetric protocol kept its signs.) If the run met its criteria, this question is satisfied as asked — a narrow sweep that found a working coefficient needs no widening, and the smallest sufficient α is the right one to lock. Sweep width matters only as the diagnosis for a shortfall: criteria unmet on a narrow grid is unresolved, not negative. Never treat a larger α as more rigorous than a smaller one that already works.
3. Is the coefficient's unit stated unambiguously, so the grid is reproducible and comparable? Raw numbers are acceptable — a raw multiplier on the extracted direction, a multiple of the site's activation norm, and σ / projection-std units are all valid, and none is preferred over the others. What is not acceptable is an undeclared unit, or the same numeric α transplanted to a different site / direction / model without re-sweeping there.
4. Was BOTH a target metric AND an independent capability / coherence metric logged at every sweep point?
5. Was a usable plateau identified — target clearly above baseline noise AND capability within tolerance (< ~10% degradation; no collapse)? (If raw post-steering output cases are available — artifact #5 — spot-check them: at the locked α the text should read coherently and express the target behavior; at near-collapse α the metric should track visible degradation. A capability metric that says "fine" while sampled outputs are garbled / repetitive / off-topic is a broken metric, not a successful steer.)
6. Was the locked α placed in the MIDDLE of the plateau (not at its edge)?
7. (Recommended) Was a random-direction control run at the locked α with n_random ≥ 30, and does the learned direction's effect statistically beat random?
8. If the protocol is asymmetric across sites (+α at one group, −α at another), is the sign pattern preserved, not flattened into uniform-push?

FAIL if ANY of:

• Single hardcoded α copied from another paper, no sweep at all.
• Sweep done but NO capability metric logged (collapse cannot be detected; large-α "effect" may be OOD drift, not steering).
• α chosen where capability has crashed (> 2× baseline degradation — collapse range).
• α chosen where target effect is within baseline-noise floor (effect drowned out).
• Asymmetric protocol flattened into uniform-push (sign pattern broken).

WARN if ANY of (and no FAIL):

• Target criteria not met, and the sweep is narrow in either sense — largest-to-smallest nonzero |α| ratio < 30×, or fewer than 5 grid points — so the shortfall is unresolved rather than negative. Both conditions sit inside the "criteria not met" gate: when the criteria were met, neither a narrow range nor a small point count is a WARN.
• Coefficient unit undeclared, OR the same numeric α transplanted to a different site / direction / model without re-sweeping there (the usable range is site-dependent, so a transplanted number is not comparable). Note: a raw coefficient with its unit stated is not a WARN.
• Plateau identified but α sits at the plateau edge (not middle).
• No random-direction control at the locked α.

PASS if all 8 questions are satisfied AND the chosen α is mid-plateau with both behavior expression and capability preservation evidence. When target_criteria_met = true on a sweep too narrow to map a plateau, questions 2 and 6 count as satisfied and question 5 is judged at the locked α alone; do not ask such a run to sweep wider.

Evidence to report: file:line for the sweep-grid definition, the logged α values, the chosen α, plateau range [α_min, α_collapse], the capability metric used, random-baseline result (if any), and where the coefficient's unit is established (direction-normalization / activation-norm / σ computation site, as applicable).

Structured fields (the reviewer MUST return these named slots — they map 1:1 to the Check A JSON node in Step 5):

Field	Type	Example
status	"pass" | "warn" | "fail"	"warn"
intervention_type	"steering" | "CAA" | "DAS" | "RepE" | "SAE_feature" | "activation_patch" | "ROME" | "other"	"CAA"
sweep_grid	number[] (α values tried; [α₀] if single-value)	[0, 0.3, 1.0, 3.0]
target_criteria_met	true | false | "unknown" — did the run meet the claim's / task.md's pass criteria? Gates question 2: when true, a narrow sweep is not a finding	false
coefficient_unit	"raw_multiplier" | "activation_norm_multiple" | "sigma_proj" | "unstated"	"raw_multiplier"
capability_metric	string | null	"perplexity_holdout" or null if none logged
plateau_range	[number, number] | null	[0.3, 3.0]
locked_alpha	number | null	3.0
alpha_position	"middle" | "edge" | "outside" | "n/a"	"edge"
random_baseline	{run: bool, n_random: number|null, passed: bool|null}	{run: false, n_random: null, passed: null}
sign_pattern	"preserved" | "broken" | "n/a"	"n/a"
output_case_spotcheck	{cases_available: bool, verdict: "metric_text_consistent"|"metric_text_mismatch"|"no_cases_logged", note: string}

When triggered=false for Check A (handled by executor on early N/A exit, not by reviewer), the JSON node degenerates to {"status": "n/a", "triggered": false, "trigger_match": []} — no structured fields are emitted.

Checks B–F — Reserved

Not yet implemented. Fill in by mirroring Check A's five-field template (Trigger / Required artifacts / Audit questions + Criteria / Evidence / Structured fields). Until then they are recorded as not_implemented in the report and do not influence overall_verdict.

Constants

• REVIEWER_BACKEND = llm-chat — External LLM reviewer via llm-chat MCP (model defers to LLM_MODEL env). Always ask the external reviewer for strict, high-rigor feedback. Override with — reviewer: oracle-pro via Oracle MCP.

Arguments

• <experiment-dir-or-results-path> (positional, required) — directory containing the experiment artifacts to audit. Typically refine-logs/ (for main-experiment audit) or verify/<claim_dir>/variants/ (for variant audit).
• — claim <Cx> (required) — the claim whose mechanism rigor is being audited. The skill is inherently per-claim: each invocation produces ONE PASS/WARN/FAIL/N/A verdict for the named claim. To audit N claims, call the skill N times.
• — output-dir <path> (optional) — directory to write MECHANISM_AUDIT.{md,json} into. Defaults to current working directory. When given, the skill creates <path> if needed and writes directly to <path>/MECHANISM_AUDIT.md and <path>/MECHANISM_AUDIT.json; callers do not need a follow-up mv.

Example invocations:

/mechanism-audit "refine-logs/"                    — claim C1 — output-dir verify/C1_polysemantic/main_experiment_audit
/mechanism-audit "verify/<claim_dir>/variants/"    — claim C1 — output-dir verify/<claim_dir>/variant_audit

If — claim is omitted, abort with:

"mechanism-audit: — claim <Cx> is required. This skill is per-claim by design — to audit a whole project, run it once per claim."

Reviewer LLM Configuration (mandatory, read first)

This skill calls an external LLM reviewer. Never hardcode a model name and never read the reviewer model from task.md / project READMEs / source comments. Project-level files may list available API keys for unrelated purposes (e.g., LLM-as-judge inside experiment code); those are not the reviewer config.

Resolve LLM_MODEL, LLM_BASE_URL, LLM_API_KEY strictly in this priority order before any reviewer call:

1. Project MCP config — ${PROJECT_ROOT}/.mcp.json, field mcpServers["llm-chat"].env.{LLM_MODEL,LLM_BASE_URL,LLM_API_KEY}.
2. User MCP config — ~/.claude/settings.json, same field.
3. Shell environment — $LLM_MODEL, $LLM_BASE_URL, $LLM_API_KEY.

Pre-flight check (run before Step 4 — skip on Step 2 early N/A exit)

LLM_MODEL_SRC=""
if [ -f .mcp.json ] && jq -e '.mcpServers["llm-chat"].env.LLM_MODEL' .mcp.json >/dev/null 2>&1 ; then
  export LLM_MODEL=$(jq -r '.mcpServers["llm-chat"].env.LLM_MODEL' .mcp.json)
  export LLM_BASE_URL=$(jq -r '.mcpServers["llm-chat"].env.LLM_BASE_URL' .mcp.json)
  export LLM_API_KEY=$(jq -r '.mcpServers["llm-chat"].env.LLM_API_KEY' .mcp.json)
  LLM_MODEL_SRC="project .mcp.json"
elif [ -f ~/.claude/settings.json ] && jq -e '.mcpServers["llm-chat"].env.LLM_MODEL' ~/.claude/settings.json >/dev/null 2>&1 ; then
  export LLM_MODEL=$(jq -r '.mcpServers["llm-chat"].env.LLM_MODEL' ~/.claude/settings.json)
  export LLM_BASE_URL=$(jq -r '.mcpServers["llm-chat"].env.LLM_BASE_URL' ~/.claude/settings.json)
  export LLM_API_KEY=$(jq -r '.mcpServers["llm-chat"].env.LLM_API_KEY' ~/.claude/settings.json)
  LLM_MODEL_SRC="user ~/.claude/settings.json"
elif [ -n "$LLM_MODEL" ] && [ -n "$LLM_BASE_URL" ] && [ -n "$LLM_API_KEY" ] ; then
  LLM_MODEL_SRC="shell env"
fi
echo "[reviewer-config] LLM_MODEL=$LLM_MODEL  LLM_BASE_URL=$LLM_BASE_URL  source=$LLM_MODEL_SRC"

Skip rule. If Step 2 took the early N/A exit (no implemented check triggered), the reviewer call in Step 4 never runs — skip this pre-flight too. A pure-evaluation claim must not be aborted just because the project lacks a reviewer key it would never use.

Hard-fail rule: If the pre-flight runs (i.e., at least one check triggered) and LLM_MODEL is empty after this resolution (none of the three sources provides it), the skill MUST abort with:

"Reviewer model not configured. Add mcpServers.llm-chat.env.{LLM_MODEL,LLM_BASE_URL,LLM_API_KEY} to .mcp.json (project) or ~/.claude/settings.json (user)."

Do not guess a default. Do not fall back to a model name read from task.md or any other project file.

Workflow

The workflow is a mechanical walk over the Check Catalogue. Step 1 scopes the file universe to claim <Cx> (mirrors /experiment-audit's Step 1). Steps 2–3 iterate the catalogue: for each implemented check K, detect whether K's trigger fires; if it does, collect K's Required artifacts. Step 4 hands the per-check bundles to the reviewer with K's criteria block pasted verbatim from the catalogue. Step 5 writes the report; Step 6 prints a one-line summary to stdout for human / caller convenience.

No catalogue logic is embedded in this section. Adding a new check (B–F) means editing only the catalogue above; Steps 2–4 pick it up automatically.

Step 1: Collect <Cx>-scoped artifacts (Executor — Claude)

This skill is per-claim. Resolve <Cx> → milestones → scripts/outputs; the result is the search universe for the per-check Steps 2–3. Mirrors /experiment-audit's Step 1 (sub-steps 1a/1b are identical in intent).

1a. Resolve <Cx>'s linked milestones

1. Read EXPERIMENT_PLAN.md from the experiment-dir argument.
2. Locate the "## Claim-to-Milestone Map" table (columns typically:
   `Claim | Tests | Required milestones | Pass criterion`).
3. Find the row where the `Claim` column equals <Cx>.
4. Parse the `Required milestones` column → list of milestone IDs, e.g. ["M1", "M2"].
5. If <Cx> has no row in the map, abort with:
   "mechanism-audit: claim <Cx> not found in EXPERIMENT_PLAN.md's Claim-to-Milestone Map."

1b. Filter the tracker to <Cx>'s milestone rows

1. Read EXPERIMENT_TRACKER.md from the experiment-dir argument.
2. Keep only rows whose `Milestone` column starts with any of <Cx>'s milestone IDs.
3. From those rows, collect:
     - scripts referenced (CX_SCRIPTS): a deduped list of source files.
     - result-file paths and run directories (CX_OUTPUTS).
     - the matching tracker row text itself (CX_TRACKER_TEXT).

CX_SCRIPTS and CX_OUTPUTS are the search universe for Steps 2–3. Per-check trigger detection and artifact collection look only inside this set.

Step 2: Per-check trigger detection (Executor — Claude)

Walk the Check Catalogue. For each implemented check K, evaluate K's Trigger keywords / signals against three sources:

1. The <Cx> methodology paragraph from EXPERIMENT_PLAN.md (Step 1a).
2. CX_TRACKER_TEXT (Step 1b).
3. CX_SCRIPTS — grep for K's keyword regex:

   # K_REGEX is K's trigger keyword regex from the catalogue
   grep -rlnE "$K_REGEX" $CX_SCRIPTS 2>/dev/null
   

Record triggered[K] = true if ANY source matches; otherwise false. Also stash the match locations (file:line) — they become the starting points for Step 3's collection.

Early N/A exit. If every implemented K has triggered[K] = false:

• Set overall_verdict = n/a.
• Skip Steps 3–4 entirely (no reviewer call needed; Pre-flight is also skipped — see "Reviewer LLM Configuration" above).
• Go directly to Step 5 to write the N/A report (see "Early N/A exit rendering" there).

Step 3: Per-check artifact collection (Executor — Claude)

For each K where triggered[K] = true, collect K's Required artifacts from the catalogue, scoped to CX_SCRIPTS ∪ CX_OUTPUTS. The catalogue row tells you what kinds of files to look for; the Step-3 match locations tell you where in the codebase to start.

Large-file sampling. If a required artifact is > ~500 lines or > ~200 KB, do not pass the whole file. Pass a sampled view and record the sampling method in the bundle:

• Tabular / JSONL run outputs (e.g. per-α metric logs): stratified sample — one row per α / sweep point if the file is keyed by α; otherwise first 20 + last 20 + every 10th middle row.
• Long log files: first 50 + last 50 lines.
• Code files: pass whole (code is rarely the size problem; truncation breaks line-number evidence).

Catalogue-specific sampling overrides this generic rule. When a check's Required artifacts entry specifies a sampling recipe (e.g. Check A artifact #5 says "5 prompts × the α grid" for raw output cases), follow the catalogue recipe instead of the generic rule above. The generic rule is the fallback when the catalogue is silent.

Assemble each K's bundle as:

check_id: A
artifacts:
  - role: intervention_script
    path: src/steering.py
    sampling: full
  - role: sweep_config
    path: configs/sweep.yaml
    sampling: full
  - role: per_alpha_run_output
    path: runs/sweep_20260601/results.jsonl
    sampling: "stratified: one row per α (5 of 5)"
  - role: direction_extraction
    path: src/directions.py
    sampling: full
match_locations:    # from Step 2, for reviewer's reference
  - src/steering.py:42  # "activations += alpha * v"
  - configs/sweep.yaml:12  # "alpha: [0, 0.3, 1.0, 3.0]"

Step 4: Reviewer call (external LLM via llm-chat MCP)

For each triggered K, paste K's catalogue subsection verbatim (Audit questions + FAIL/WARN/PASS criteria + Evidence-to-report) into the prompt, followed by K's bundle from Step 3. The reviewer reads bundled files directly and judges only against the pasted criteria. Always ask for strict, high-rigor feedback.

mcp__llm-chat__chat:
  prompt: |
    You are a mechanistic-experiment rigor auditor. For each check block below,
    read the listed files and return ONE verdict (PASS | WARN | FAIL) judged
    strictly against that block's criteria.

    Audit scope: claim <Cx>, restricted to the milestones below.
    Triggering has ALREADY been decided by the executor. Do NOT skip a check
    you think shouldn't apply — every block below is one you must grade.

    Context:
    - claim: <Cx> — [claim statement]
    - milestones: [M1, M2, ...]

    (The mechanism in actual use is grounded by the trigger match locations
    inside each check block below — read those file:line citations rather
    than relying on the plan's self-description.)

    ──────────────────────────────────────────────────────────────────
    ## Check A — Steering coefficient sweep

    [PASTE VERBATIM from Catalogue §"Check A — Steering coefficient sweep":
       Audit questions (all 8)
       FAIL criteria
       WARN criteria
       PASS criteria
       Evidence to report]

    Artifacts for Check A:
      [paste the YAML bundle from Step 3 for K = A]

    Executor-found match locations (starting points):
      [file:line list from Step 2]
    ──────────────────────────────────────────────────────────────────

    [Repeat one dashed block per additional triggered check as B–F come online.]

    ## Output schema
    For each check block above, return ALL named slots listed in that block's
    "Structured fields" table — verbatim by field name and type. At minimum every
    check returns `check_id`, `status`, `evidence`, `details`; check-specific slots
    (e.g. Check A's `intervention_type`, `sweep_grid`, `target_criteria_met`, `coefficient_unit`,
    `capability_metric`, `plateau_range`, `locked_alpha`, `alpha_position`,
    `random_baseline`, `sign_pattern`, `output_case_spotcheck`) are mandatory and
    must use the exact field names from that check's Structured fields table.
    If a slot is genuinely unknowable from the artifacts (e.g. `random_baseline`
    when no random-direction control was run), return the documented null shape
    (`{run: false, n_random: null, passed: null}`) — do NOT omit the field.

    Then return:
      - overall_verdict = max severity across the blocks above
        (fail > warn > pass).

    Be thorough. Read every artifact line by line. Do not infer from filenames.

Step 5: Write report (Executor — Claude)

Output path resolution. If — output-dir <path> was given, write to <path>/MECHANISM_AUDIT.md and <path>/MECHANISM_AUDIT.json directly (create <path> with mkdir -p if needed); otherwise write to the current working directory.

Status assignment per catalogue row — walk the catalogue in order:

Check state	Reported status	Counts toward overall_verdict?
Implemented, triggered, reviewer judged	pass / warn / fail	yes
Implemented, not triggered (Step 2 = false)	n/a	no
Reserved (B–F: no implementation yet)	not_implemented	no

overall_verdict = max_severity over checks whose status ∈ {pass, warn, fail}. If that set is empty (all checks were n/a or not_implemented) → overall_verdict = n/a.

Early N/A exit rendering — when Step 2 took the early-N/A exit (no implemented check triggered), the reviewer never ran, so the per-check structured fields are unknowable by construction. Use this degenerate shape and skip the regular per-check field rendering below:

• Markdown — for each implemented check, write only:

  ### A. Steering Coefficient Sweep: N/A
  - Triggered: no (no catalogue trigger matched in <Cx>'s scope)
  

  Omit Intervention type / Sweep grid / Plateau / Output-case spot-check / Evidence / Verdict-reason rows entirely. The N/A reason already explains why every field is empty.

• JSON — for each implemented check, write:

  "steering_coefficient_sweep": {
    "status": "n/a",
    "triggered": false,
    "trigger_match": []
  }
  

  No structured fields. Top-level: "triggered_checks": [], "overall_verdict": "n/a".

When at least one check triggered, render the full per-check field block below as usual.

Write MECHANISM_AUDIT.md:

# Mechanism Audit Report — Claim <Cx>

**Date**: [today]
**Auditor**: external LLM reviewer (cross-model, via llm-chat MCP)
**Project**: [project name]
**Claim**: <Cx> — [claim statement]
**Linked milestones**: [M1, M2, ...]

## Overall Verdict: [PASS | WARN | FAIL | N/A]
*This is `<Cx>`'s mechanism-rigor verdict. `N/A` means no catalogue check
was triggered for `<Cx>`'s scope — either the claim uses no mechanism
intervention, or its intervention lies outside the current catalogue coverage.*

## Triggered checks (this run): [list of K with triggered = true, e.g. "A"]

## Checks

### A. Steering Coefficient Sweep: [PASS | WARN | FAIL | N/A]
- Triggered: [yes — via "src/steering.py:42 (activations += alpha * v)" | no]
- Intervention type: [steering vector | CAA | DAS | SAE feature | ROME | n/a]
- Sweep grid: [α values tried, or "single hardcoded value: ..."]
- Target criteria met: [yes → sweep width not assessed | no → width assessed | unknown]
- Coefficient unit: [raw multiplier | activation-norm multiple | σ_proj | unstated]
- Capability metric logged: [perplexity | val-acc | fluency | ... | none]
- Plateau range: [α_min, α_collapse] = [..., ...]
- Locked α: [value]   (position in plateau: middle | edge | outside)
- Random-direction control: [yes (n=...) → passed/failed | no | n/a]
- Sign pattern (if asymmetric): [preserved | broken | n/a]
- Output-case spot-check: [coherent at locked α; degraded at near-collapse — metric tracks text | metric/text mismatch (e.g. "fluency ok" but cases garbled) | no cases logged]
- Evidence: [file:line references]
- Verdict reason: [one sentence]

### B–F. Reserved (not_implemented)
Status: not yet implemented. Future checks may cover direction-extraction
quality, site / layer selection, n_effective sufficiency, probe-vs-causal
disentanglement, intervention scope.

## Action Items
- [specific fixes if WARN or FAIL]

Also write MECHANISM_AUDIT.json:

{
  "date": "2026-06-05",
  "auditor": "llm-chat",
  "audit_type": "mechanism",
  "claim_id": "C1",
  "linked_milestones": ["M1", "M2"],
  "triggered_checks": ["A"],
  "overall_verdict": "warn",
  "checks": {
    "steering_coefficient_sweep": {
      "status": "warn",
      "triggered": true,
      "trigger_match": ["src/steering.py:42 (activations += alpha * v)",
                        "configs/sweep.yaml:12 (alpha grid)"],
      "intervention_type": "CAA",
      "sweep_grid": [0, 0.3, 1.0, 3.0],
      "target_criteria_met": false,
      "coefficient_unit": "raw_multiplier",
      "capability_metric": "perplexity_holdout",
      "plateau_range": [0.3, 3.0],
      "locked_alpha": 3.0,
      "alpha_position": "edge",
      "random_baseline": {"run": false, "n_random": null, "passed": null},
      "sign_pattern": "n/a",
      "output_case_spotcheck": {
        "cases_available": true,
        "verdict": "metric_text_mismatch",
        "note": "perplexity within tolerance at α=3.0 but sampled completions show repetition / topic drift on 3 of 5 prompts."
      },
      "evidence": ["src/steering.py:42-58", "configs/sweep.yaml:12"],
      "details": "Criteria not met, and the grid spans only 10× (< 30×) over 4 points, so the shortfall is unresolved rather than negative; α also sits at the plateau edge."
    },
    "check_b_reserved": {"status": "not_implemented"},
    "check_c_reserved": {"status": "not_implemented"},
    "check_d_reserved": {"status": "not_implemented"},
    "check_e_reserved": {"status": "not_implemented"},
    "check_f_reserved": {"status": "not_implemented"}
  }
}

N/A semantics. A check with triggered: false reports status: n/a (not not_implemented). When triggered_checks is empty, set overall_verdict: n/a. Downstream /auto-verify treats n/a as pass for max_severity combination — claims with no mechanism intervention are not punished by this audit.

No Claim Impact section, no claims array. This skill audits mechanism rigor for ONE claim; overall_verdict IS that claim's mechanism verdict. Methodology honesty is /experiment-audit's job; semantic claim support is /result-to-claim's job. To audit multiple claims, invoke this skill once per claim.

Step 6: Print summary

🔧 Mechanism Audit Complete — Claim C1 (M1, M2)

  Triggered checks: A  (matches at src/steering.py:42, configs/sweep.yaml:12)

  A. Steering Coefficient Sweep: ⚠️ WARN — α at plateau edge, grid spans only 10×
  B–F. Reserved:                 — not_implemented

  Overall (C1): ⚠️ WARN

  See <output-dir>/MECHANISM_AUDIT.md for details.

When no implemented check triggered (early N/A exit from Step 2):

🔧 Mechanism Audit Complete — Claim C1 (M1, M2)

  Triggered checks: (none)

  A. Steering Coefficient Sweep: — N/A (trigger not matched)
  B–F. Reserved:                 — not_implemented

  Overall (C1): — N/A (combination treats this as PASS)

  See <output-dir>/MECHANISM_AUDIT.md for details.

Integration with Other Skills

Automatic in /auto-verify (advisory, never blocks)

This skill runs per claim, paired with /experiment-audit, at every phase where /experiment-audit is invoked. Concretely in /auto-verify:

• Phase 2 (main-experiment integrity gate): /experiment-audit followed by /mechanism-audit, both scoped to Cx, both writing to verify/<claim_dir>/main_experiment_audit/. The Phase 2 gate verdict is combined = max_severity(exp.overall_verdict, mech.overall_verdict) with the severity ordering fail > warn > pass > n/a.
• Phase 9 (variant integrity audit): symmetric — both audits run on verify/<claim_dir>/variants/, both write to verify/<claim_dir>/variant_audit/. Each variant's integrity_status in verdict.json is set to the per-variant combined verdict.

/auto-experiment → results ready
    ↓
for each Cx:
    /experiment-audit → EXPERIMENT_AUDIT.{md,json}
    /mechanism-audit  → MECHANISM_AUDIT.{md,json}
    combined = max_severity(exp.overall_verdict, mech.overall_verdict)
        ├── PASS  → continue normally for Cx
        ├── WARN  → print ⚠️ warning, continue, tag Cx as [INTEGRITY: WARN]
        └── FAIL  → print 🔴 alert, continue, tag Cx as [INTEGRITY CONCERN]
    ↓
/auto-iteration-loop

Never blocks the pipeline. Even on FAIL, the pipeline continues — but the affected claim carries a visible integrity tag.

Complementary with /experiment-audit and /result-to-claim

/experiment-audit answers "is the evaluation methodology / reporting honest?" (Checks A–F: GT, normalization, file existence, dead code, scope, eval type). /mechanism-audit answers "was the interpretability mechanism tuned with the necessary controls?" (Check A: coefficient sweep; B–F reserved). /result-to-claim answers "do the numbers semantically support the claim?" (statistical / scope reasoning).

The three are intentionally separate. Downstream skills typically read both audit JSONs and combine:

exp_verdict  = read EXPERIMENT_AUDIT.json.overall_verdict
mech_verdict = read MECHANISM_AUDIT.json.overall_verdict   # may be "n/a"
combined     = max_severity(exp_verdict, mech_verdict)     # n/a treated as pass

if combined == "fail":
    downgrade verdict display: "yes [INTEGRITY CONCERN]"

/mechanism-audit does NOT emit claim_supported. Its overall_verdict IS the target claim's mechanism-rigor verdict (PASS/WARN/FAIL/N/A); to cover N claims, invoke it N times.

Key Rules

• Reviewer independence: executor collects paths, reviewer judges. Period.
• Never block: warn loudly, never halt the pipeline.
• N/A is not a failure: a check whose trigger does not fire in <Cx>'s scope reports n/a; if no implemented check triggers, the overall verdict is n/a. Downstream combination treats N/A as PASS, so claims out of catalogue coverage are not punished.
• Catalogue is the API: extension = add one row + one subsection to the Check Catalogue. Workflow, reviewer prompt, and report writer are mechanism-agnostic and pick up the new row automatically.
• File-as-switch: no MECHANISM_AUDIT.md = skill was never run = zero impact on existing behavior.
• Cross-model: the reviewer MUST be a different model family from the executor.
• Honest about limits: only Check A (steering coefficient sweep) is implemented. B–F are reserved placeholders for future mechanism-rigor checks. A PASS today only certifies that the coefficient was swept correctly; it does not certify direction quality, site choice, or sample-size sufficiency.

Acknowledgements

Check A's failure-mode catalog and audit logic are concentrated from experiment-tips/steering-coefficient-tuning/SKILL.md.

Review Tracing

After each mcp__llm-chat__chat reviewer call, save the trace following shared-references/review-tracing.md. Write files directly to .mechanist/traces/<skill>/<date>_run<NN>/. Respect the --- trace: parameter (default: full).