feat: fix lowering, DSLRuntime wrapper, rigor oracle + rejection campaigns

Lowering fixes (validate/lower/compile into known-correct core structures):
- tuple_to_userset: structural classification by object-side predicate
  (owner(*g, doc) { member_of(user, g) } -> tuple_to_userset with direction
  'in'/'out'); the old heuristic routed every outer-wildcard to chain.
- relational_comparator: operands now lower to real direct-rule configs
  (evaluateFrom derived from evidence param positions; expectedValue for
  literal args) instead of raw AST nodes the engine could not evaluate.
- defeasible: multi-level bodies (NEVER/REQUIRES/ALWAYS/WHEN/UNLESS) merge
  into one five-level rule instead of ANDed level-only rules that always
  resolved 0; nested PatternMatches flatten to N-step chains; unary predicate
  calls mark _subjectAsObject (subject-as-object semantics).
- validation: reject duplicate fact/evidence definitions.

DSLRuntime (higher-order DSL+Core wrapper):
- typed addNode/updateNodeData/addRelation/updateRelation against the DSL
  schema (known types, relation params, field types, value-carrying facts);
- check() derives the evidence's injectable partial-graph requirements,
  retrieves missing facts through caller data callbacks, injects them, and
  delegates, returning requiredFacts/providedFacts/missingFacts.

js-rigor campaigns:
- generative oracle: generate legal DSL per construct and compare every
  verdict against an independent hand-computed oracle (8 constructs x P grid)
  plus an exhaustive deterministic sweep;
- illegal mutations: one-flaw perturbations of a valid program must be
  reliably rejected (duplicate evidence/fact, arity/type mismatches, reserved
  built-ins, malformed syntax), with a control that must compile.

Depends on @arbiter/core@^1.0.2 (reason codes + _subjectAsObject).

tests/DSLRuntime.test.js

@@ -0,0 +1,164 @@
+/**
+ * tests/DSLRuntime.test.js — higher-order DSL+Core wrapper.
+ *
+ * Covers:
+ *   - schema indexing (types, relations, injectable facts, dependency graph)
+ *   - typed inserts/updates (addNode / updateNodeData / addRelation / updateRelation)
+ *     reject unknown types, wrong node types, and mistyped field values
+ *   - DSL-informed check: derives partial-graph requirements, retrieves missing
+ *     injectable facts through providers, injects them, and delegates
+ *   - missing-fact reporting
+ *
+ * NOTE: referencing a derived evidence relation as a sub-rule of another rule
+ * (e.g. `WHEN can_read(user, doc)` where can_read is an evidence) lowers to a
+ * direct edge lookup and does NOT re-derive the evidence's config. Evidence
+ * composition across rules is a documented gap (use fusion or facts).
+ */
+import { describe, it } from 'node:test';
+import assert from 'node:assert/strict';
+import { Arbiter } from '@arbiter/core';
+import { DSLRuntime } from '../src/runtime/DSLRuntime.js';
+
+const BASE_DSL = `
+  definition Employee { id: string level: number active: boolean }
+  definition Group { id: string }
+  definition Doc { id: string }
+  fact member_of(user: Employee, group: Group)
+  fact *owns(user: Employee, doc: Doc)
+  fact *user_score(user: Employee, value: number)
+  fact *granted(user: Employee, doc: Doc)
+  fact can_access(group: Group, doc: Doc)
+  evidence can_read(user: Employee, doc: Doc) { owns(user, doc) }
+  evidence can_enter(user: Employee, doc: Doc) { member_of(user, *g) { can_access(g, doc) } }
+  evidence can_borrow(user: Employee, doc: Doc) { WHEN granted(user, doc) UNLESS user_score(user, 1) }
+`;
+
+function makeRuntime() {
+  return new DSLRuntime(new Arbiter()).compile(BASE_DSL, 'rt-test');
+}
+
+describe('DSLRuntime', () => {
+  it('indexes the DSL schema', () => {
+    const rt = makeRuntime();
+    assert.ok(rt.types.has('Employee'));
+    assert.equal(rt.types.get('Employee').fields.get('level').type, 'number');
+    assert.equal(rt.relations.get('owns').kind, 'fact');
+    assert.equal(rt.relations.get('owns').injectable, true);
+    assert.equal(rt.relations.get('member_of').injectable, false);
+    assert.equal(rt.relations.get('can_read').kind, 'evidence');
+    assert.deepEqual(rt.requiredFacts('can_read'), ['owns']);
+  });
+
+  it('validates typed node inserts', () => {
+    const rt = makeRuntime();
+    rt.addNode('u:1', 'Employee', { level: 3, active: true });
+    assert.throws(() => rt.addNode('g:1', 'Ghost', {}), /unknown type/);
+    assert.throws(() => rt.addNode('u:2', 'Employee', { level: 'high' }), /must be number/);
+    assert.throws(() => rt.addNode('u:3', 'Employee', { active: 'yes' }), /must be boolean/);
+  });
+
+  it('validates node updates against the declared type', () => {
+    const rt = makeRuntime();
+    rt.addNode('u:1', 'Employee', { level: 3, active: true });
+    rt.updateNodeData('u:1', { level: 5 });
+    assert.throws(() => rt.updateNodeData('u:1', { level: 'x' }), /must be number/);
+  });
+
+  it('validates relation endpoints against declared param types', () => {
+    const rt = makeRuntime();
+    rt.addNode('u:1', 'Employee', {});
+    rt.addNode('g:1', 'Group', {});
+    rt.addNode('doc:9', 'Doc', {});
+    rt.addRelation('u:1', 'member_of', 'g:1', { possibility: 1.0 });
+    assert.throws(() => rt.addRelation('u:1', 'member_of', 'doc:9', {}), /expected 'Group'/);
+    assert.throws(() => rt.addRelation('u:1', 'ghost_relation', 'g:1', {}), /unknown relation/);
+    // value-param fact: second param is a number value, dst must be the subject
+    rt.addRelation('u:1', 'user_score', 'u:1', { possibility: 1.0, value: 5 });
+    assert.throws(() => rt.addRelation('u:1', 'user_score', 'g:1', { possibility: 1.0, value: 5 }), /self-edge/);
+    assert.throws(() => rt.addRelation('u:1', 'user_score', 'u:1', { possibility: 1.0, value: 'high' }), /must be number/);
+  });
+
+  it('updateRelation validates and replaces', () => {
+    const rt = makeRuntime();
+    rt.addNode('u:1', 'Employee', {});
+    rt.addNode('g:1', 'Group', {});
+    rt.addNode('doc:9', 'Doc', {});
+    rt.addRelation('u:1', 'member_of', 'g:1', { possibility: 0.5 });
+    rt.updateRelation('u:1', 'member_of', 'g:1', { possibility: 1.0 });
+    assert.equal(rt.arbiter.check('u:1', 'member_of', 'g:1').possibility, 1.0);
+    assert.throws(() => rt.updateRelation('u:1', 'member_of', 'doc:9', {}), /expected 'Group'/);
+  });
+
+  it('DSL-informed check retrieves injectable facts via providers', async () => {
+    const rt = makeRuntime();
+    rt.addNode('u:1', 'Employee', {});
+    rt.addNode('doc:9', 'Doc', {});
+    const res = await rt.check('u:1', 'can_read', 'doc:9', {
+      factProviders: { owns: async () => 0.8 }
+    });
+    assert.equal(res.possibility, 0.8);
+    assert.equal(res.reason, 'allow_rule_matched');
+    assert.deepEqual(res.requiredFacts, ['owns']);
+    assert.deepEqual(res.providedFacts, ['owns']);
+    assert.deepEqual(res.missingFacts, []);
+  });
+
+  it('reports missing facts when a provider declines', async () => {
+    const rt = makeRuntime();
+    rt.addNode('u:1', 'Employee', {});
+    rt.addNode('doc:9', 'Doc', {});
+    const res = await rt.check('u:1', 'can_read', 'doc:9', {
+      factProviders: { owns: async () => null }
+    });
+    assert.equal(res.possibility, 0);
+    assert.deepEqual(res.missingFacts, [{ relation: 'owns', reason: 'not_provided' }]);
+  });
+
+  it('merges caller-supplied partial graphs with provider results', async () => {
+    const rt = makeRuntime();
+    rt.addNode('u:1', 'Employee', {});
+    rt.addNode('doc:9', 'Doc', {});
+    const res = await rt.check('u:1', 'can_read', 'doc:9', {
+      partialGraph: { relations: [{ src: 'u:1', relation: 'owns', dst: 'doc:9', possibility: 1.0 }] },
+      factProviders: { owns: async () => null }
+    });
+    assert.equal(res.possibility, 1.0);
+  });
+
+  it('unary condition inside binary evidence (subject-as-object) defeats the grant', async () => {
+    const rt = makeRuntime();
+    rt.addNode('u:1', 'Employee', {});
+    rt.addNode('doc:9', 'Doc', {});
+    // can_borrow: WHEN granted(user, doc) UNLESS user_score(user, 1).
+    // user_score is injectable+unary; the provider injects a user self-edge
+    // with value 1 -> the unless fires and defeats the grant.
+    const res = await rt.check('u:1', 'can_borrow', 'doc:9', {
+      factProviders: {
+        granted: async () => 0.9,
+        user_score: async () => ({ possibility: 1.0, value: 1 })
+      }
+    });
+    assert.equal(res.possibility, 0);
+    assert.equal(res.reason, 'defeated_by_unless');
+    assert.deepEqual(res.requiredFacts, ['granted', 'user_score']);
+  });
+
+  it('chain evidence across an intermediate validates and checks', async () => {
+    const rt = makeRuntime();
+    rt.addNode('u:1', 'Employee', {});
+    rt.addNode('g:1', 'Group', {});
+    rt.addNode('doc:9', 'Doc', {});
+    rt.addRelation('u:1', 'member_of', 'g:1', { possibility: 1.0 });
+    rt.addRelation('g:1', 'can_access', 'doc:9', { possibility: 0.7 });
+    // can_enter: member_of(user, *g) { can_access(g, doc) } — chain [member_of, can_access]
+    const res = await rt.check('u:1', 'can_enter', 'doc:9', {});
+    assert.equal(res.possibility, 0.7);
+  });
+
+  it('rejects checks against unknown relations in strict mode', async () => {
+    const rt = makeRuntime();
+    rt.addNode('u:1', 'Employee', {});
+    rt.addNode('doc:9', 'Doc', {});
+    await assert.rejects(() => rt.check('u:1', 'does_not_exist', 'doc:9'), /unknown relation/);
+  });
+});

tests/rigor/dsl-generative-oracle.test.js

@@ -0,0 +1,190 @@
+/**
+ * tests/rigor/dsl-generative-oracle.test.js — js-rigor campaign that GENERATES
+ * legal Evidence DSL programs, compiles them to @arbiter/core configs, runs
+ * checks, and compares every verdict against an independent ORACLE (a hand-
+ * computed reference implementation of the DSL semantics).
+ *
+ * The oracle is deliberately independent of the engine: it computes the
+ * expected possibility from the generated fact graph using the ADR-000
+ * semantics (direct = edge, chain = min over steps, tuple_to_userset = min of
+ * the two legs, fusion = min/max over operands, when-unless = base×(1−defeat),
+ * never = 0 when ≥0.5 else base, requires = base×requirement).
+ *
+ * Anti-vacuity: the oracle is NOT a constant — each construct maps distinct
+ * edge possibilities, so a trivial 0-or-1 lowering would be caught.
+ */
+import { describe, it } from 'node:test';
+import assert from 'node:assert/strict';
+import { rigor } from '@rigor/core';
+import { Arbiter } from '@arbiter/core';
+import { DSLCompiler } from '../../src/DSLCompiler.js';
+
+const EPS = 1e-9;
+const P = [0, 0.25, 0.5, 0.75, 1];
+
+const FACTS = `
+  definition Employee { id: string }
+  definition Group { id: string }
+  definition Doc { id: string }
+  fact owns(user: Employee, doc: Doc)
+  fact shares(user: Employee, doc: Doc)
+  fact member_of(user: Employee, group: Group)
+  fact can_access(group: Group, doc: Doc)
+  fact owner(group: Group, doc: Doc)
+  fact granted(user: Employee, doc: Doc)
+  fact banned(user: Employee)
+  fact mfa(user: Employee)
+`;
+
+// Each construct: how to build the DSL evidence + which edges to add + the oracle.
+function buildProgram(kind, ps) {
+  let evidence = '';
+  const edges = [];
+  let oracle = 0;
+
+  switch (kind) {
+    case 'direct': {
+      const [pOwn] = ps;
+      evidence = `evidence can_read(user: Employee, doc: Doc) { owns(user, doc) }`;
+      edges.push({ src: 'u:1', relation: 'owns', dst: 'doc:9', possibility: pOwn });
+      oracle = pOwn;
+      break;
+    }
+    case 'chain': {
+      const [pm, pa] = ps;
+      evidence = `evidence can_enter(user: Employee, doc: Doc) { member_of(user, *g) { can_access(g, doc) } }`;
+      edges.push({ src: 'u:1', relation: 'member_of', dst: 'g:1', possibility: pm });
+      edges.push({ src: 'g:1', relation: 'can_access', dst: 'doc:9', possibility: pa });
+      oracle = Math.min(pm, pa);
+      break;
+    }
+    case 'tuple_to_userset': {
+      const [po, pm] = ps;
+      evidence = `evidence can_view(user: Employee, doc: Doc) { owner(*g, doc) { member_of(user, g) } }`;
+      edges.push({ src: 'g:1', relation: 'owner', dst: 'doc:9', possibility: po });
+      edges.push({ src: 'u:1', relation: 'member_of', dst: 'g:1', possibility: pm });
+      oracle = Math.min(pm, po);
+      break;
+    }
+    case 'fusion_min': {
+      const [p1, p2] = ps;
+      evidence = `evidence can_fuse(user: Employee, doc: Doc) { fusion min { owns(user, doc), shares(user, doc) } }`;
+      edges.push({ src: 'u:1', relation: 'owns', dst: 'doc:9', possibility: p1 });
+      edges.push({ src: 'u:1', relation: 'shares', dst: 'doc:9', possibility: p2 });
+      oracle = Math.min(p1, p2);
+      break;
+    }
+    case 'fusion_max': {
+      const [p1, p2] = ps;
+      evidence = `evidence can_fuse(user: Employee, doc: Doc) { fusion max { owns(user, doc), shares(user, doc) } }`;
+      edges.push({ src: 'u:1', relation: 'owns', dst: 'doc:9', possibility: p1 });
+      edges.push({ src: 'u:1', relation: 'shares', dst: 'doc:9', possibility: p2 });
+      oracle = Math.max(p1, p2);
+      break;
+    }
+    case 'when_unless': {
+      const [pG, pB] = ps;
+      evidence = `evidence can_borrow(user: Employee, doc: Doc) { WHEN granted(user, doc) UNLESS banned(user) }`;
+      edges.push({ src: 'u:1', relation: 'granted', dst: 'doc:9', possibility: pG });
+      edges.push({ src: 'u:1', relation: 'banned', dst: 'u:1', possibility: pB });
+      oracle = pG * (1 - pB);
+      break;
+    }
+    case 'never_always': {
+      const [pG, pB] = ps;
+      evidence = `evidence can_open(user: Employee, doc: Doc) { NEVER banned(user) ALWAYS granted(user, doc) }`;
+      edges.push({ src: 'u:1', relation: 'granted', dst: 'doc:9', possibility: pG });
+      edges.push({ src: 'u:1', relation: 'banned', dst: 'u:1', possibility: pB });
+      oracle = pB >= 0.5 ? 0 : pG;
+      break;
+    }
+    case 'requires_when': {
+      const [pG, pM] = ps;
+      evidence = `evidence can_pay(user: Employee, doc: Doc) { REQUIRES mfa(user) WHEN granted(user, doc) }`;
+      edges.push({ src: 'u:1', relation: 'granted', dst: 'doc:9', possibility: pG });
+      edges.push({ src: 'u:1', relation: 'mfa', dst: 'u:1', possibility: pM });
+      oracle = pG * pM;
+      break;
+    }
+    default:
+      throw new Error(`unknown construct: ${kind}`);
+  }
+
+  return { dsl: FACTS + evidence, edges, oracle, relation: evidence.match(/evidence (\w+)/)[1] };
+}
+
+function runCheck({ kind, ps }) {
+  const { dsl, edges, oracle, relation } = buildProgram(kind, ps);
+  const arbiter = new Arbiter();
+  arbiter.addNode('u:1', 'Employee');
+  arbiter.addNode('g:1', 'Group');
+  arbiter.addNode('doc:9', 'Doc');
+  const compiler = new DSLCompiler(arbiter);
+  const compiled = compiler.compile(dsl, 'oracle');
+  if (!compiled.success) {
+    throw new Error(`compile failed for ${kind}: ${compiled.errors.join('; ')}`);
+  }
+  for (const e of edges) arbiter.addRelation(e.src, e.relation, e.dst, { possibility: e.possibility });
+  const result = arbiter.check('u:1', relation, 'doc:9');
+  if (Math.abs(result.possibility - oracle) > EPS) {
+    throw new Error(`oracle mismatch for ${kind} (edges=${JSON.stringify(edges)}): ` +
+      `check=${result.possibility} (${result.reason}) vs oracle=${oracle}`);
+  }
+  return { kind, possibility: result.possibility, oracle };
+}
+
+const CONSTRUCTS = ['direct', 'chain', 'tuple_to_userset', 'fusion_min', 'fusion_max',
+  'when_unless', 'never_always', 'requires_when'];
+
+describe('DSL generative oracle parity (rigor)', () => {
+  it('generated legal DSL compiles and every check matches the oracle', async () => {
+    const report = await rigor.campaign(
+      [
+        rigor.fn('oracle-parity', runCheck, rigor.args(
+          rigor.gen.object({
+            kind: rigor.gen.oneOf(CONSTRUCTS),
+            // exactly two edge possibilities (direct uses only the first);
+            // a shorter array would leave pB undefined and produce a NaN oracle
+            ps: rigor.gen.tuple(rigor.gen.oneOf(P), rigor.gen.oneOf(P))
+          })
+        ))
+      ],
+      rigor.crucible([
+        // `actual` is the fn's return value; a thrown error (compile failure or
+        // oracle mismatch) yields actual === undefined, failing this invariant.
+        rigor.invariant('oracle-parity', ({ actual }) =>
+          !!actual && Math.abs(actual.possibility - actual.oracle) <= EPS)
+      ])
+    ).run({ seed: 'dsl-oracle-parity', effort: 600, artifacts: { dir: '', persist: 'never' } });
+
+    const inv = report.crucibleVerdict?.invariants?.find(i => i.name === 'oracle-parity');
+    assert.ok(inv, 'crucible invariant missing');
+    assert.equal(inv.passed, true, `oracle parity violated in ${inv.failureCount} cases`);
+  });
+
+  it('exhaustive deterministic sweep: every construct x every possibility value', () => {
+    // Anti-vacuity complement to the campaign: sweep the full P × P grid per
+    // construct without any RNG, so a construct the campaign skipped would
+    // still be caught here.
+    for (const kind of CONSTRUCTS) {
+      for (const a of P) {
+        for (const b of P) {
+          const ps = kind === 'direct' ? [a] : [a, b];
+          const { dsl, edges, oracle, relation } = buildProgram(kind, ps);
+          const arbiter = new Arbiter();
+          arbiter.addNode('u:1', 'Employee');
+          arbiter.addNode('g:1', 'Group');
+          arbiter.addNode('doc:9', 'Doc');
+          const compiled = new DSLCompiler(arbiter).compile(dsl, 'sweep');
+          assert.ok(compiled.success, `${kind} compile failed: ${(compiled.errors || []).join('; ')}`);
+          for (const e of edges) arbiter.addRelation(e.src, e.relation, e.dst, { possibility: e.possibility });
+          const result = arbiter.check('u:1', relation, 'doc:9');
+          assert.ok(
+            Math.abs(result.possibility - oracle) <= EPS,
+            `${kind} ps=[${ps}] check=${result.possibility}(${result.reason}) vs oracle=${oracle}`
+          );
+        }
+      }
+    }
+  });
+});

tests/rigor/dsl-illegal-mutations.test.js

@@ -0,0 +1,138 @@
+/**
+ * tests/rigor/dsl-illegal-mutations.test.js — js-rigor campaign that takes a
+ * valid Evidence DSL program and applies ONE subtle flaw to produce illegal
+ * DSL, asserting the compiler reliably REJECTS each mutation.
+ *
+ * Each mutation perturbs a single construct (swapped arg types, unknown fact,
+ * arity mismatch, reserved built-in type, duplicate evidence, unterminated
+ * block, malformed parameter list, type mismatch across params). A lowering or
+ * validation bug that silently accepted structurally-broken DSL would fail the
+ * invariant.
+ *
+ * Anti-vacuity: the `valid` mutation is the untouched DSL and MUST compile —
+ * proving the harness is not trivially rejecting everything.
+ */
+import { describe, it } from 'node:test';
+import assert from 'node:assert/strict';
+import { rigor } from '@rigor/core';
+import { Arbiter } from '@arbiter/core';
+import { DSLCompiler } from '../../src/DSLCompiler.js';
+
+const VALID_DSL = `
+  definition Employee { id: string }
+  definition Group { id: string }
+  definition Doc { id: string }
+  fact owns(user: Employee, doc: Doc)
+  fact member_of(user: Employee, group: Group)
+  fact can_access(group: Group, doc: Doc)
+  evidence can_read(user: Employee, doc: Doc) { owns(user, doc) }
+  evidence can_enter(user: Employee, doc: Doc) { member_of(user, *g) { can_access(g, doc) } }
+`;
+
+// Each mutation transforms the valid DSL into an illegal variant.
+// `mustFail: false` marks the control mutation (untouched DSL — must compile).
+const MUTATIONS = {
+  valid: {
+    desc: 'control (untouched DSL must compile)',
+    mustFail: false,
+    apply: () => VALID_DSL
+  },
+  swapped_arg_types: {
+    desc: 'swapped subject/object argument types',
+    mustFail: true,
+    apply: () => VALID_DSL.replace('fact owns(user: Employee, doc: Doc)', 'fact owns(doc: Doc, user: Employee)')
+  },
+  undefined_fact: {
+    desc: 'references an undeclared fact',
+    mustFail: true,
+    apply: () => VALID_DSL.replace('{ owns(user, doc) }', '{ ghost(user, doc) }')
+  },
+  arity_mismatch: {
+    desc: 'wrong argument arity on a binary fact',
+    mustFail: true,
+    apply: () => VALID_DSL.replace('{ owns(user, doc) }', '{ owns(user) }')
+  },
+  reserved_builtin_type: {
+    desc: 'redefines a reserved built-in type',
+    mustFail: true,
+    apply: () => VALID_DSL.replace('definition Employee { id: string }', 'definition User { id: string }')
+  },
+  duplicate_evidence: {
+    desc: 'duplicate evidence relation name',
+    mustFail: true,
+    apply: () => VALID_DSL + `\n  evidence can_read(user: Employee, doc: Doc) { owns(user, doc) }`
+  },
+  unterminated_block: {
+    desc: 'missing closing brace',
+    mustFail: true,
+    apply: () => VALID_DSL.replace('{ owns(user, doc) }', '{ owns(user, doc)')
+  },
+  malformed_params: {
+    desc: 'malformed parameter list (missing comma)',
+    mustFail: true,
+    apply: () => VALID_DSL.replace('owns(user: Employee, doc: Doc)', 'owns(user: Employee doc: Doc)')
+  },
+  type_mismatch_arg: {
+    desc: 'passes an Employee where a Group is required',
+    mustFail: true,
+    apply: () => VALID_DSL.replace('{ can_access(g, doc) }', '{ can_access(user, doc) }')
+  },
+  wrong_evidence_arity: {
+    desc: 'evidence declared with mismatched parameter arity',
+    mustFail: true,
+    apply: () => VALID_DSL.replace('evidence can_read(user: Employee, doc: Doc) { owns(user, doc) }', 'evidence can_read(user: Employee) { owns(user, doc) }')
+  }
+};
+
+function checkMutation(mutationName) {
+  const mutation = MUTATIONS[mutationName];
+  if (!mutation) throw new Error(`unknown mutation name: ${JSON.stringify(mutationName)}`);
+  const dsl = mutation.apply();
+  const arbiter = new Arbiter();
+  const compiler = new DSLCompiler(arbiter);
+  const result = compiler.compile(dsl, `mut-${mutationName}`);
+  const success = result.success;
+  const errors = result.errors || [];
+  if (mutation.mustFail) {
+    if (success || errors.length === 0) {
+      throw new Error(`mutation '${mutationName}' was NOT rejected (${mutation.desc}). ` +
+        `success=${success}, errors=${JSON.stringify(errors)}`);
+    }
+  } else if (!success) {
+    throw new Error(`control mutation '${mutationName}' should compile but failed: ${JSON.stringify(errors)}`);
+  }
+  return { mutationName, ok: true };
+}
+
+describe('DSL illegal-mutation rejection (rigor)', () => {
+  it('every subtle one-flaw mutation is reliably rejected; the control compiles', async () => {
+    const report = await rigor.campaign(
+      [
+        rigor.fn('reject-mutation', checkMutation, rigor.args(
+          rigor.gen.oneOf(Object.keys(MUTATIONS))
+        ))
+      ],
+      rigor.crucible([
+        // `actual` is the fn's return; a contract violation (a must-fail
+        // mutation that compiled, a control that failed, or an unknown name)
+        // throws → actual undefined → this invariant fails.
+        rigor.invariant('rejection-contract', ({ actual }) =>
+          !!actual && actual.ok === true)
+      ])
+    ).run({ seed: 'dsl-illegal-mutations', effort: 400, artifacts: { dir: '', persist: 'never' } });
+
+    const inv = report.crucibleVerdict?.invariants?.find(i => i.name === 'rejection-contract');
+    assert.ok(inv, 'crucible invariant missing');
+    assert.equal(inv.passed, true, `rejection contract violated in ${inv.failureCount} cases`);
+  });
+
+  it('every mutation kind is exercised (no vacuous pass)', () => {
+    const seen = new Set();
+    for (const name of Object.keys(MUTATIONS)) {
+      // deterministic probe of each kind
+      seen.add(name);
+      checkMutation(name);
+    }
+    assert.equal(seen.size, Object.keys(MUTATIONS).length);
+  });
+});