Ensemble Rule Review

Ensemble Rule Review

A skill-design pattern for rule-following work. Instead of one agent holding the whole ruleset in a single pass, partition the ruleset across multiple rigid, parallel sub-agents whose coverage deliberately overlaps. Collect findings in a fixed schema, then weight by cross-agent corroboration and drop the low-weight tail. Worker model tier is a knob: the cheapest tier is the default for mechanical-matching slices; escalate to a more capable tier or heterogeneous families when a slice needs judgment or when de-correlating shared-model bias matters more than cost.

The Invariant

One move underlies every variant: partition the attention surface across a shared goal. Each agent attends to less and therefore attends better; aggregating the results averages out the spikiness of any single agent's reliability. Focus and agent attention are the same thing — a finite budget over the context that degrades as the surface grows (exactly the failure named below). Everything else is a knob on this invariant: what you partition (rule slices, personas, files), how fine each slice is, which tier attends to it, how diverse the attenders are, and how you recombine — corroboration for bounded / mechanical work, synthesis for unbounded / judgment work. Cheap, homogeneous, rule-sliced workers are one common setting of those knobs, not the invariant itself.

The Problem It Solves

A single agent holding a large ruleset (10+ criteria) and reviewing non-trivial input:

• Is slow (it reasons across the whole rubric serially).
• Silently drops criteria — attention degrades as the rule list grows, so coverage is incomplete and you cannot tell which rules were actually applied.

This is the same failure mode as instruction bloat: more rules in one context window means higher probability each individual rule is under-applied.

The Mechanism (6 Parts)

1. Control header. One line at the top compiles an effort/scale parameter into concrete knobs: worker count, candidates per worker, verify policy, output cap. The same skill body scales rigor by the parameter. Two further knobs — worker model tier and worker diversity (homogeneous vs heterogeneous families / temperature / prompt framing) — are selected separately, by error-correlation structure and stakes rather than by the effort parameter, so they do not auto-scale with it. See "Model and Effort Guidance" for their selection criteria.

2. Deliberate overlap, not just partition. Worker scenarios are engineered so their goals INTERSECT. A genuine finding falls inside multiple workers' coverage and is reported more than once. A hallucination falls inside one worker's blank-filling and is reported once. Overlap converts N cheap opinions into a signal-to-noise instrument. Pure non-overlapping partition gives speed but NOT denoising. For the overlap construction, use a balanced rotating assignment (cyclic block design — N groups, N agents, each agent a window of w groups) so every rule gets equal redundancy; see the playbook's "Balanced rotating overlap" section.

3. Zero-creativity workers. Each sub-agent gets a rigid, explicit process and a PARTIAL rule set — stated methodology, fixed output schema, no interpretation latitude. Shrink each worker's job until it is mechanical matching, which is the band where a cheap model is reliable.

4. Match worker tier to inference load. The load-bearing invariants are rigid + partial ruleset + parallel — they are what make this pattern work, and they hold at any tier. Worker tier is a knob layered on top: the cheapest tier is the default because the design has already removed inference from the worker's job, so a model that is unreliable at open-ended inference is reliable at mechanical matching. Cheapness is an economics enabler — it makes running several overlapping workers over the same input affordable — not a core mechanism. Escalate the tier (or go heterogeneous) when a slice still requires judgment or when shared-model error must be de-correlated; the invariants stay fixed, only the tier knob moves.

5. Fixed candidate schema. Every worker emits the same shape (e.g., rule_id, location, verdict, evidence). This contract makes dedup, corroboration counting, and merge possible.

6. Corroboration weighting + drop the tail (the reducer). The orchestrator collects all findings, deduplicates near-identical ones, raises weight for findings corroborated across overlapping workers and sinks lone-worker findings, trashes the low-weight tail, keeps the high-weight set. A single worker's random hallucination sinks below the keep threshold ONLY when the precision gate is set (keep_threshold = window); the default keep_threshold = 1 is recall-biased — it dedups and ranks but drops nothing. Caveat: the precision gate drops lone findings of ALL kinds, including a true critical that only one worker's slice happened to cover — so exempt critical/high severity from the tail cut and surface them flagged-but-uncorroborated rather than silently dropping them.

Why It Works

More total facts pass through cheap/fast workers, and corroboration weighting cancels the noise — for ONE of two error sources. Overlapping rule slices denoise coverage / attention variance: a rule a worker under-applies in one pass is caught by another worker holding an overlapping slice. This is bagging / majority-vote ensembling applied to LLM rule-checking, and it is the genuine win.

It does NOT cancel shared-model bias. A construct the worker model systematically misreads is misread the same way by every worker that shares that model, so corroboration weighting boosts that shared error instead of cancelling it. The variance of an N-worker average floors at the correlated-error term ρσ² — the part adding workers cannot average away (the random-forest / correlated-Condorcet result). Net: the surviving set is more reliable than one cheap agent on attention errors, and no more reliable on systematic ones. The rule partition is a real de-correlation axis, but it varies which rules each worker checks, not how it reasons over the shared input — so to denoise the second source it must be paired with diversity on the axes it does NOT vary (worker model family, temperature, prompt framing) and a keep threshold calibrated on labelled data.

SOURCE: User-reported result (conversation 2026-05-30, not independently reproduced): a scientific-journal review skill — one Sonnet agent holding the full ruleset took 14-18 minutes on a 300-line file and returned 13 findings. Splitting the rules into 4 categories and running 4 Haiku agents (each with a partial rule list) on the same file returned 14 findings in 25 seconds — comparable recall, ~35x faster.

Pipeline Phases

flowchart TD
    P0["Phase 0 — Scope<br>Deterministically define the exact<br>input set (script / git diff / file)<br>No reasoning yet"] --> P1
    P1["Phase 1 — Fan-out (map)<br>Dispatch N rigid workers<br>Each has a partial overlapping rule set<br>Each emits up to K candidates<br>in the fixed schema<br>Recall comes from here"] --> P2
    P2["Phase 2 — Reduce<br>Dedup → weight by corroboration<br>→ drop low-weight tail<br>Optional: one-vote verifier per<br>surviving candidate<br>(CONFIRMED / PLAUSIBLE / REFUTED)<br>Precision comes from here"] --> OUT
    OUT["Output<br>Ranked, capped, structured<br>Empty result is a valid terminal"]

Degrees of Freedom

Model and Effort Guidance

Tier and worker diversity are knobs, not fixed values. Select them by matching to per-rule competence, error-correlation structure, and stakes — the same axis the experiment matrix names as THE de-correlation lever (./references/experiment-matrix.md, "worker model" row) and the fit gate tests as a mandatory converse (./references/candidate-fit.md, Q5 + rubric #5). Set the chosen tier in the worker agent's frontmatter model: field — never as a prose mandate (./references/instruction-hygiene.md §3).

• Workers — cost default (mechanical-matching slices): cheapest tier, effort low. When the design has shrunk the job to mechanical matching, a homogeneous fleet at the cheapest tier is correct: the rigidity makes it reliable and the overlap denoises single-worker attention errors. This is the right default for most slices. Don't overpay for mechanical work.
• Workers — escalate (judgment-heavy slices, high-stakes review, very large rulesets): raise to a more capable tier and/or use heterogeneous model families (and varied temperature / prompt framing) to de-correlate shared-model error. Escalate when a slice cannot be reduced to mechanical matching, when the cost of a shared systematic miss exceeds the cost of stronger workers, or when the ruleset is large enough that even a strong single agent's attention degrades across it. Don't underpay for judgment work — a cheap homogeneous fleet on a judgment slice just corroborates the same blind spot.
• Reducer / orchestrator: mid tier, effort medium. It weights and merges; this job needs more inference than a worker slice and is not parallelized N-fold, so the cost case differs.
• The economics rule is "match worker tier to inference load," not "always cheapest." Running one capable or different-family worker alongside cheap workers is a deliberate de-correlation choice, not waste.

SOURCE: /plugin-creator:agentskills — degrees-of-freedom guidance and model selection by task cognitive requirement. Tier/diversity-as-knob criteria: ./references/experiment-matrix.md (worker-model de-correlation lever) and ./references/candidate-fit.md (Q5 + rubric #5 diversity gate).

Composition Framework (tier × diversity × stage)

A compact selection aid: pick a fleet composition by matching the dominant error source and the stakes of the slice, not by a blanket cost rule. The flowchart branches on the discriminator (error-correlation structure / stakes / cost); the four compositions below are the leaves.

flowchart TD
    Start([Configure the worker fleet for a slice]) --> Q1{"Is the slice reducible to<br>mechanical matching after<br>thin slicing?"}
    Q1 -->|"Yes — mechanical"| Q2{"High stakes OR shared-model<br>systematic miss likely<br>on this construct?"}
    Q1 -->|"No — needs judgment"| Q3{"Can you inject diversity<br>(heterogeneous families /<br>temperature / framing)?"}
    Q2 -->|"No — low stakes,<br>cost dominates"| CH["Cheap-homogeneous (DEFAULT)<br>Cheapest tier x N, same family<br>Rigidity + overlap denoise attention errors<br>Right for most slices"]
    Q2 -->|"Yes — de-correlation matters"| HET["Heterogeneous-capable<br>Different model families and/or<br>varied temperature/framing<br>Breaks shared-model bias the vote<br>cannot otherwise cancel"]
    Q3 -->|"Yes"| MIX["Mixed-tier fleet<br>Cheap workers on mechanical sub-slices<br>+ one or more capable/different-family<br>workers on the judgment sub-slice<br>Diversity is mandatory here (candidate-fit Q5)"]
    Q3 -->|"No — cannot inject diversity"| Single["Not an ensemble fit<br>Keep a single capable agent<br>Corroboration would boost shared bias<br>(candidate-fit Q5 -> Stop)"]
    CH --> Verify{"Need an independent<br>precision check on<br>surviving findings?"}
    HET --> Verify
    MIX --> Verify
    Verify -->|"Yes — false positives costly"| IndV["Add independent different-model verifier<br>One capable worker from a different family<br>than the workers, voting CONFIRMED/PLAUSIBLE/REFUTED<br>per surviving candidate<br>A same-model verifier shares the workers' blind spot"]
    Verify -->|"No — recall-biased, low stakes"| NoV["No separate verifier<br>Reducer keep-threshold handles precision"]

Diversity is multi-axis. Worker diversity is not only model family / temperature / prompt framing — it ALSO includes role / persona / expert-framework diversity (e.g. distinct advisor personas, each carrying a different expert lens, over one unbounded problem). Treat role/persona as a first-class diversity axis alongside the model-level axes when de-correlation matters.

Reduce method follows boundedness. Bounded / mechanical rule-checking → corroboration-weight + drop-tail over a cheap homogeneous swarm (this skill); unbounded / judgment problems → escalate to synthesis across diverse lenses (a capable, role-diverse panel), whose reduce step is synthesis, not corroboration counting (see ./references/methodology-selection.md). Example: a cheap mechanical codebase-rule swarm (this skill) vs a role-diverse strong advisor panel on an open design question (synthesis, not this skill's reducer).

The four compositions, by selection criterion:

• Cheap-homogeneous (the default): mechanical-matching slice, low stakes, cost dominates. Cheapest tier, one family, N workers. The rigidity plus overlap denoise attention errors; this is correct for most slices.
• Heterogeneous-capable: mechanical or near-mechanical slice where a shared-model systematic miss is the dominant risk, or stakes are high. Vary model family / temperature / prompt framing to de-correlate the error the vote cannot otherwise cancel (the floor at ρσ²; see "Why It Works").
• Mixed-tier fleet: the slice has both mechanical and judgment sub-parts. Run cheap workers on the mechanical sub-slices and one or more capable / different-family workers on the judgment sub-slice. Per candidate-fit.md Q5, diversity is mandatory once judgment is involved.
• Independent different-model verifier (Phase 2 add-on): when false positives are costly, add one capable verifier from a different family than the workers to vote on each surviving candidate. A same-family verifier shares the workers' blind spot and adds little.

Criterion in one line: mechanical + low-stakes → cheap-homogeneous; shared-bias risk or high stakes → heterogeneous; mixed work → mixed-tier; costly false positives → add an independent different-model verifier. Set the chosen tiers via each worker agent's frontmatter model: field. Full factor sweep: ./references/experiment-matrix.md.

When to Use / When Not to Use

For the full go/no-go decision — candidate signals, the ensemble-denoising-vs-other-flavor alignment check, and the fit-killer where corroboration boosts shared-model bias — load ./references/candidate-fit.md. To choose among the wider family of fan-out methodologies (work-partition, Best-of-N, debate, DAG) when this skill is not the right one, load ./references/methodology-selection.md.

Use when:

• Rule-following / checklist / rubric work with 10+ independent criteria.
• A single agent currently applies the whole ruleset in one pass (slow + silent drops).
• The ruleset can be split into scenario-bound jobs with some overlap.

Do NOT use when:

• Single-pass transforms with no ruleset (map-reduce overhead exceeds the return).
• Tasks needing one coherent creative judgment that cannot be partitioned without losing whole-picture context.
• Rulesets under ~5 criteria (splitting yields little).

Multi-phase / sequential workflows are NOT disqualified. Do not score the whole pipeline as one unit — score each phase. A sequential workflow is the conductor; each rule-following phase becomes its own internal ensemble and each independent-work phase becomes a work-partition fan-out, while the phase ordering stays sequential. There are two fan-out flavors:

• Ensemble-denoising (this skill's core) — same input, overlapping rule slices, corroboration weighting. For checking / review / rubric phases.
• Work-partition — disjoint independent work items in parallel, no corroboration, pure speedup. For generative phases (implement N functions, write N test files, scan N docs).

See ./references/composing-in-workflows.md for the per-phase classification rule and a worked map of a 9-phase workflow.

How to Partition the Ruleset

Explicit lists — partition is free. When the ruleset already names its categories, those categories ARE the worker boundaries. Examples:

• Named principle frameworks: the 12 factors of twelve-factor; the 5 SOLID principles; OWASP categories for a security review; WCAG criteria for accessibility; Nielsen's 10 usability heuristics for a UI critique.
• An enumerated ## Checklist or ## Quality Criteria section.

Implicit lists — enumerate first, then partition. A rubric is named but not enumerated; make it explicit, then split. Examples:

• "look for modernization opportunities" → an explicit PEP roster (585 generics, 604 unions, 572 walrus, 634 match, 673 Self, StrEnum, tomllib, pathlib, dataclasses) → buckets.
• "ensure it's pythonic / idiomatic" → comprehensions, context managers, EAFP, enumerate/zip, mutable-default-arg, truthiness.
• "review for quality" → correctness / error-handling / naming / dead-code / structure.
• "follow best practices" / "avoid anti-patterns" → enumerate the named patterns.

The tell: any instruction containing "ensure … follows", "review for", "look for … opportunities", or a named framework is an implicit (or pre-partitioned) checklist.

For the full typology of implicit-checklist patterns grouped by partition-readiness — named principle sets, "modernization / idiomatic / pythonic", "review X for quality", and prompt-engineering / skill-quality self-review (with per-pattern examples) — load ./references/partitioning-patterns.md.

Operational Use

Two procedures and one reusable contract turn this pattern from concept into action:

• Convert an existing single-pass skill into the ensemble form — follow ./references/conversion-workflow.md. (Also the recipe for standardizing the multi-perspective-review prior art below.)
• Run an ensemble ad hoc, mid-task, as an orchestrator — follow ./references/orchestrator-playbook.md: the recognize → decompose → dispatch → reduce loop, the partition knobs, and the corroboration-weighting reducer algorithm.
• Reusable worker contract — copy ./assets/worker-prompt-skeleton.md: the rigid worker prompt and the fixed candidate schema both procedures share.
• Planner script — run ./scripts/plan_ensemble.py RULES.json --report-dir /abs/dir (tested; ./scripts/test_plan_ensemble.py) to compute the rotating-overlap assignment deterministically. It assigns each worker its groups + an absolute OUTFILE, tags rules per-group, verifies uniform redundancy, and prints the recommended --keep-threshold — removing the manual bookkeeping that caused this session's bugs (wrong paths, drifted group ids, ad-hoc overlap, per-worker tagging).
• Reducer script — run ./scripts/reduce.py (tested; ./scripts/test_reduce.py) over the worker output files to dedup, corroboration-weight on (group, location), drop the tail, and rank. Workers emit a stable group id (the corroboration key) plus a free-form rule slug (descriptive only) — keying on the slug would never corroborate, since workers name rules differently.
• Measure whether it actually works — follow ./references/measuring-success.md: the free no-gold-set weight-distribution diagnostic, precision/recall/F1 against a labelled set, and the falsification tests. Never measure by finding count.
• Tune weighting, workers, prompts, and output schema — use the factor matrix and cheapest-first ablation order in ./references/experiment-matrix.md.
• Keep prompts, skills, and agents clean before shipping — run the pre-ship checklist in ./references/instruction-hygiene.md on every prompt, skill, and agent (and any A/B harness arms) to catch leaked implementation detail and inconsistent instruction sets.

The two scripts are deterministic bookends around the only fuzzy step (the LLM workers' rule matching): plan_ensemble.py → spawn focused-reviewer ×N → reduce.py.

The worker agent

Spawn the plugin-creator:focused-reviewer agent as each map worker — a lean haiku agent with minimal tools (Read, Grep, Glob, Bash, Write) and no inherited skills, built to apply one rule slice and emit the fixed schema. Do NOT use general-purpose workers: they inherit every skill and MCP tool description, adding a large constant token cost to every one of the N parallel workers. For web/API targets, the spawner adds the one specific MCP tool to the worker's tools.

Partition the ruleset, not the input

Every worker reviews the SAME input; only its rule slice differs. The denoising comes from overlapping rule coverage on shared input — multiple workers independently reaching the same finding, which the reducer counts as corroboration. Sharding the input instead (different files per worker) buys speed but NOT denoising, because no two workers can corroborate the same location. Shard input only as a secondary axis when one worker cannot hold the whole input, and keep rule-overlap within each shard.

Prior Art and Reference Implementation

The pattern is already running in-repo as a partial implementation:

• plugins/development-harness/skills/multi-perspective-review/SKILL.md — a working 4-worker parallel review fan-out (Security, Performance, Quality, Accessibility) with per-worker SOPs and a merge gate.
• plugins/development-harness/agents/reviewer-{security,quality,performance,accessibility}.md — the rigid worker agents.

It lacks two pieces vs the full pattern: a fixed candidate schema and an explicit corroboration-weight reducer (it merges by any-REJECT, not corroboration weighting).

The control-header + finder-angles + constrained-verdict-verify + capped-output structure originates in the Anthropic-bundled /code-review built-in skill.

SOURCE: /plugin-creator:agentskills — progressive disclosure, lean SKILL.md, skill packaging discipline.

For the ranked catalog of in-repo conversion candidates (Tier 0-3, clusters C1-C9), load ./references/conversion-candidates.md.