---
model_tier: inherit
name: corpus-grounding
description: "Shared corpus-grounding engine — BM25 + structured filters + decision rules over CSV corpora via a domain manifest. Use when a skill needs grounded pre-action option-space constraints."
domain: engineering
workspaces:
  - engineering
packs:
  - engineering-base
trust:
  level: professional
install:
  removable: true
execution:
  type: manual
---

# corpus-grounding

> The reusable grounding layer from ADR-061: one pure-stdlib engine
> (BM25 retrieval + structured pre-filters + decision-rule evaluation)
> that any domain plugs into via a **manifest** — frontend design is its
> first consumer ([`design-intelligence`](../design-intelligence/SKILL.md)).
> A corpus **grounds** (pre-action, constrains the option space); it never
> replaces mid-action reference (RAG), post-action validation (rules), or
> the method itself (a framework skill).

Engine provenance: ported from `nextlevelbuilder/ui-ux-pro-max-skill`
@ `b7e3af80f6e331f6fb456667b82b12cade7c9d35` (MIT, last checked
2026-06-07) — BM25 de-duplicated, slide-only paths stripped, every
frontend-hardcoded axis moved into the manifest. Full license obligations:
[`design-intelligence/ATTRIBUTION.md`](../design-intelligence/ATTRIBUTION.md).

## When to use

- A skill needs **pre-action selection** grounded in curated knowledge
  ("which layout pattern / threat class / index strategy applies here").
- You are authoring a **new domain corpus** — write a manifest + CSVs,
  validate with the grounding CLI (`ground validate` via ./scripts-run),
  never fork the engine.
- You need stack-scoped Do/Don't guidance (`--stack react …`).

## Do NOT

- Do NOT use the corpus for mid-task fact lookup — that is reference
  (`references/` docs / RAG).
- Do NOT use it for output validation — write a rule/linter.
- Do NOT build a corpus that fits in 5 lines of an always-on rule.
- Do NOT fork the engine per domain — plug in via a manifest.
- Do NOT merge a manifest without owner + refresh cadence (validator
  refuses it anyway).

## Procedure: Consult a corpus

1. Locate the domain manifest (`<domain-skill>/data/manifest.json`).
2. Run `search` (one domain / stack axis) or `ground` (reasoning plan).
3. Read `confidence` + `evidence_gap` before trusting any row.
4. Propose grounded options; the human confirms (Tier-1 default).

### Invocation (consumer runtime)

Scripts resolve all paths **skill-relative** (per
[`docs/contracts/skill-bundled-assets.md`](../../../docs/contracts/skill-bundled-assets.md))
— they work from any cwd:

```bash
./scripts-run <skills-root>/corpus-grounding/scripts/ground search \
  --manifest <skills-root>/<domain-skill>/data/manifest.json \
  "fintech dashboard" [--domain style] [--stack react] \
  [--filter "Severity=HIGH"] [--max-results 3] [--json]

./scripts-run <skills-root>/corpus-grounding/scripts/ground ground \
  --manifest <skills-root>/<domain-skill>/data/manifest.json \
  "luxury e-commerce" [--context '{"data_heavy": true}'] [--persist DIR] \
  [--variance 1-10] [--motion 1-10] [--density 1-10]

./scripts-run <skills-root>/corpus-grounding/scripts/ground validate --manifest …
```

`<skills-root>` is wherever skills are deployed (`~/.claude/skills/` for
Claude Code installs; `src/skills/` inside this repo).

**The three `ground` dials are optional 1-10 preferences, and unset means
unset** — a dial you do not pass changes nothing, so the no-flag result is
byte-identical to what it was before they existed. `--variance` biases which
style is **selected** from the rows the corpus returned (never which rows come
back), and when it changes the pick away from the grounding rule's own choice
the run says so in its evidence gaps. `--motion` needs a `gsap` domain in the
manifest and reports when a tier matches nothing. `--density` overrides the
spacing scale. All three render in the text output and in a persisted
`MASTER.md`, not only under `--json`.

## Output format

**Interface contract v1 — stability promise.** Per ADR-061 §2 ("Opus
condition"), this interface is **versioned**; domains may depend on it. Breaking any item below requires a major bump
(`manifest_version: 2`), a migration note here, and updates to every
consuming skill in the same PR. Additive fields are allowed anytime.

Stable v1 surface:

1. **Modules + public names** — `bm25_search.{BM25, load_csv, apply_filters,
   search_rows, RETRIEVERS}`, `decision_engine.{detect_domain, search_domain,
   search_stack, evaluate_rules, ground, persist_grounding}`,
   `schema_validator.{load_manifest, validate_manifest, resolve_data_path,
   ManifestError, MANIFEST_VERSION, TIERS}`.
2. **CLI** — the grounding CLI (`ground {search|ground|validate}` via
   ./scripts-run) with the flags shown above.
3. **Result shape** — search: `{domain|stack, query, file, count, results,
   scores, filtered_from, confidence{label,score}, evidence_gap[]}`;
   ground: `{domain, query, category, rule, rules_evaluation{matched,
   unmatched}, selections{<domain>: {best, alternatives, confidence}},
   confidence{label,score}, evidence_gap[]}`.
4. **Contract invariants** — every output carries `confidence` **and**
   `evidence_gap`; retrievers are name-selected (`bm25` default,
   `structured`, `hybrid`); no network, no subprocess, read-only except
   the opt-in `--persist DIR`.

## Manifest contract (schema-agnostic plug-in)

Each domain ships `data/manifest.json` beside its CSVs — declaring its
**own** axes; the engine never assumes the frontend schema:

```json
{
  "manifest_version": 1,
  "domain": "frontend-design",
  "tier": "conditional-grounding",
  "data_dir": ".",
  "retriever": "bm25",
  "default_domain": "style",
  "domains": {
    "style": {
      "file": "styles.csv",
      "search_cols": ["Style Category", "Keywords"],
      "output_cols": ["Style Category", "Best For"],
      "max_results": 3,
      "filters": {}
    }
  },
  "detect": { "style": ["minimalism", "glassmorphism"] },
  "stacks": { "react": "stacks/react.csv" },
  "stack_cols": { "search_cols": ["…"], "output_cols": ["…"] },
  "reasoning": {
    "file": "ui-reasoning.csv",
    "category_domain": "product",
    "category_column": "Product Type",
    "match_column": "UI_Category",
    "rules_column": "Decision_Rules",
    "priority_column": "Style_Priority",
    "priority_domain": "style",
    "name_columns": { "style": "Style Category" },
    "plan": { "style": 3, "color": 2 },
    "rules_module": "rules.ts"
  },
  "owner": "package-maintainer",
  "refresh_cadence": "quarterly",
  "upstream": { "repo": "…", "sha": "…", "last_checked": "YYYY-MM-DD" }
}
```

- `tier` ∈ `lookup-only | conditional-grounding | constraint-emission`;
  `reasoning` is only legal above lookup-only.
- `owner`, `refresh_cadence`, `upstream{repo,sha,last_checked}` are
  **required** — provenance discipline per ADR-061 §6; an unowned corpus
  is not merged.
- `rules_module` (optional TypeScript escape hatch where JSON rules cap
  out — a module exposing `evaluate(rules, query, context)`; a legacy
  `.py` name in a manifest is remapped to its `.ts`/`.js` twin) must live
  beside the manifest — absolute paths and `..` are refused.
- Decision rules are surfaced as `matched` **and** `unmatched` — the full
  rule space stays auditable, never a hidden gate.

## Procedure: Author a new domain corpus

1. Pass the qualification rubric (ADR-061 §5): decision-rule utility beats
   row count; grounding must happen **before** action; "fits in 5 lines →
   it's a rule, not a corpus".
2. Write `data/manifest.json` + CSVs in your domain skill; run
   the grounding CLI (`ground validate` via ./scripts-run).
3. Name an owner + refresh cadence in the manifest, pin the upstream SHA.
4. Cite this skill from your domain skill; consult via the CLI (Tier-1
   consultation default — propose grounded options, human confirms).

## Gotchas

- An empty result is a legitimate outcome — surface the evidence gap and
  proceed on priors; never silently widen filters to force a hit.
- The structured `filters` pre-filter matches case-insensitive
  substrings; an over-specific value silently filters everything out —
  check `filtered_from` vs `count` when results look thin.
- `detect` keyword routing falls back to `default_domain`; product-shaped
  queries route best ("fintech dashboard"), generic words land on the
  default.
- BM25 tokenizer drops tokens ≤2 chars — "UI", "a11y" style queries need
  longer companions.

## Security constraints (Step 1.6 runtime-safety record)

Four scripts ship under `scripts/`: `ground.ts` (CLI), `bm25_search.ts`,
`decision_engine.ts`, `schema_validator.ts`.

- **What they may touch** — corpus CSVs and the manifest under the
  manifest's own directory. `resolve_data_path` refuses absolute paths and
  `..` escapes, so the manifest directory is the read boundary.
- **What they must never do** — read outside that directory, reach the
  network, or spawn a subprocess. Embeddings and remote retrievers are
  intentionally not implemented (ADR-061 §2), and that is a containment
  decision, not a missing feature.
- **Default invocation** — read-only. The single write surface is opt-in
  `--persist DIR`, which writes `MASTER.md` (and `pages/<page>.md` when
  `--page` is given) under `DIR/design-system/<project-slug>/`. Nothing
  else writes.
- **Outbound** — nothing. No network access at all.

One qualified exception: `rules_module` executes a manifest-adjacent
TypeScript module via dynamic `import()`. That is the same trust domain as
the skill shipping the manifest, and its containment is `resolve_data_path`.

## See also

- [`design-intelligence`](../design-intelligence/SKILL.md) — first consumer
  (frontend corpus + manifest).
- [ADR-061](../../../docs/decisions/ADR-061-corpus-grounding-layer.md) —
  architecture, qualification rubric, fork resolutions.
- [`docs/contracts/skill-bundled-assets.md`](../../../docs/contracts/skill-bundled-assets.md)
  — how bundled `scripts/` + `data/` reach consumer runtime.