feat: bounded self-recursion (transitive closure) for evidence

An evidence whose config contains a chain step referencing ITSELF is now
unrolled at compile time into a bounded transitive closure: a union of paths
— base, hop+base, hop²+base, …, hop^N+base — where `hop` is the recursive
chain's steps before the self-reference and the depth N comes from the
pattern's `limit N` (or the compiler's maxRecursionDepth default, 3). The
base (the evidence's non-recursive statements) is verified as a condition
step at each path's terminal node, so the engine needs no new machinery.

- Chain configs carry the pattern's `limit` as maxDepth.
- resolveEvidenceReferences detects a self-reference (_findSelfReference),
  extracts the base (_extractBase), and unrolls (_unrollRecursiveEvidence).
- Pure recursion with no base case is a compile-time error; mutual cycles
  between distinct evidence remain a compile-time error.

Example: can_access_via = can_access OR (reports_to + can_access_via) up to
the declared limit grants access inherited up a reporting chain.

Tests: Recursion (unroll shape, base + multi-hop grants, depth-limit
enforcement, default depth, pure-recursion error, mutual-cycle guard).

package-lock.json

@@ -1,15 +1,15 @@
 {
   "name": "@arbiter/evidence-dsl",
-  "version": "1.1.0",
+  "version": "1.6.0",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "@arbiter/evidence-dsl",
-      "version": "1.1.0",
+      "version": "1.6.0",
       "license": "ISC",
       "dependencies": {
-        "@arbiter/core": "^1.0.2"
+        "@arbiter/core": "^1.0.4"
       },
       "devDependencies": {
         "@rigor/core": "^3.1.0",
@@ -17,9 +17,9 @@
       }
     },
     "node_modules/@arbiter/core": {
-      "version": "1.0.2",
-      "resolved": "https://hub.kl1.tenere.ai/api/packages/Arbiter/npm/%40arbiter%2Fcore/-/1.0.2/core-1.0.2.tgz",
-      "integrity": "sha512-N1duiHy1Rlsxqpvu8uPf4tMaLOQ2tNXvGs53jLkRcIAYqafIAMvcf0BPS2iE2xVKNsqY92+F05bZZEAO5jnbyQ==",
+      "version": "1.0.4",
+      "resolved": "https://hub.kl1.tenere.ai/api/packages/Arbiter/npm/%40arbiter%2Fcore/-/1.0.4/core-1.0.4.tgz",
+      "integrity": "sha512-1zXy3mZACjwELptsV8QpYvZJmMU7BhUQ4FsKNfp3/oJDwjfMqAImcAF3mJ+HNZpQnLQXScmELTwow5VduvN27g==",
       "license": "ISC",
       "dependencies": {
         "@tenere/pltc-core": "^0.6.3",

package.json

@@ -1,6 +1,6 @@
 {
   "name": "@arbiter/evidence-dsl",
-  "version": "1.2.0",
+  "version": "1.11.0",
   "description": "Evidence DSL v2 compiler: translates the natural Evidence DSL (ADR-000) into @arbiter/core relation configurations.",
   "license": "ISC",
   "type": "module",
@@ -24,7 +24,7 @@
     "generate:parser": "node scripts/generate-parser.js"
   },
   "dependencies": {
-    "@arbiter/core": "^1.0.2"
+    "@arbiter/core": "^1.0.4"
   },
   "devDependencies": {
     "@rigor/core": "^3.1.0",

src/DSLCompiler.js

@@ -7,10 +7,10 @@ import { validateDslText } from './validation/DSLValidation.js';
  * Compiles DSL text into rule configurations for the zanzibar-graph system
  */
 export class DSLCompiler {
-  constructor(arbiter) {
+  constructor(arbiter, options = {}) {
     this.arbiter = arbiter;
     this.parser = parse;
-    this.generator = new RuleGenerator(arbiter);
+    this.generator = new RuleGenerator(arbiter, options);
     this.compiledPrograms = new Map();
   }
 

src/generator/RuleGenerator.js

@@ -5,12 +5,14 @@ import { ProgramNode, DefinitionNode, FactNode, EvidenceNode, MeasureNode, Direc
  * Generates rule configurations that interface with the existing rule system
  */
 export class RuleGenerator {
-  constructor(arbiter) {
+  constructor(arbiter, options = {}) {
     this.arbiter = arbiter;
     this.generatedRules = new Map();
     this.errors = [];
     this.dependencyIndex = new Map();
     this.evidenceNames = new Set();
+    // Default depth for bounded self-recursion when the DSL `limit N` is absent.
+    this.maxRecursionDepth = options.maxRecursionDepth ?? 3;
   }
 
   /**
@@ -155,6 +157,7 @@ export class RuleGenerator {
         for (const step of rule.steps) {
           if (typeof step === 'string') targetSet.add(step);
           else if (step && typeof step.relation === 'string') targetSet.add(step.relation);
+          else if (step && step.rule) collect(step.rule, targetSet);
         }
       }
       if (rule.type === 'relational_comparator') {
@@ -485,14 +488,21 @@ export class RuleGenerator {
       reverse: false
     };
 
-    // Subject-scoped (unary) call: the predicate call's args omit the
-    // evidence's object parameter (user_risk(user, 1) inside a binary
-    // evidence) → check the relation on the subject itself.
+    // Unary predicate calls check the relation as a self-edge on the call's
+    // subject entity (the graph stores unary facts as self-edges). The subject
+    // entity may be the evidence's SUBJECT or its OBJECT parameter — mark the
+    // matching rewrite flag.
     const evidenceParams = (evidence && evidence.params) || [];
     const objectVar = evidenceParams[1] && evidenceParams[1].name;
     const argName = a => a && (a.name !== undefined ? a.name : a.value);
-    if (objectVar !== undefined && !(predicate.arguments || []).some(a => argName(a) === objectVar)) {
-      rule._subjectAsObject = true;
+    const args = predicate.arguments || [];
+    if (objectVar !== undefined) {
+      const hasObjectArg = args.some(a => argName(a) === objectVar);
+      if (args.length === 1 && argName(args[0]) === objectVar) {
+        rule._subjectIsObject = true;
+      } else if (!hasObjectArg) {
+        rule._subjectAsObject = true;
+      }
     }
 
     return rule;
@@ -621,7 +631,8 @@ export class RuleGenerator {
       type: 'chain',
       steps,
       aggregator: 'max',
-      collectValues: true
+      collectValues: true,
+      maxDepth: patternMatch.limit || null
     };
   }
 
@@ -662,7 +673,10 @@ export class RuleGenerator {
       type: 'chain',
       steps,
       aggregator: 'max',
-      collectValues: true
+      collectValues: true,
+      // Carry the pattern's `limit N` as a max depth so a self-referential
+      // chain step can be unrolled into bounded transitive closure.
+      maxDepth: patternMatch.limit || null
     };
   }
 
@@ -982,13 +996,113 @@ export class RuleGenerator {
   resolveEvidenceReferences() {
     for (const name of this.evidenceNames) {
       if (!this.generatedRules.has(name)) continue;
+      let config = this.generatedRules.get(name);
+      // Bounded self-recursion (transitive closure): an evidence whose config
+      // contains a chain step referencing ITSELF is unrolled into a union of
+      // bounded paths — base, hop+base, hop²+base, …, hop^N+base — where `hop`
+      // is the recursive chain's steps before the self-reference and the depth
+      // N comes from the pattern's `limit N` (or the compiler default).
+      const selfRef = this._findSelfReference(config, name);
+      if (selfRef) {
+        const depth = selfRef.limit ?? this.maxRecursionDepth;
+        const unrolled = this._unrollRecursiveEvidence(name, config, selfRef.hop, depth);
+        if (unrolled) {
+          config = unrolled;
+          this.generatedRules.set(name, config);
+        }
+      }
       const stack = new Set([name]);
-      const resolved = this._resolveRule(this.generatedRules.get(name), stack);
+      const resolved = this._resolveRule(config, stack);
       this.generatedRules.set(name, resolved);
       this._annotateDependencies(name, resolved);
     }
   }
 
+  /**
+   * Find the first chain step within `config` that references `name` (a
+   * self-reference). Returns { hop, limit } where hop is the chain's steps
+   * before the self-reference and limit is the chain's declared max depth.
+   * Returns null when there is no self-reference.
+   */
+  _findSelfReference(config, name) {
+    let found = null;
+    const walk = (rule) => {
+      if (!rule || typeof rule !== 'object' || found) return;
+      if (rule.type === 'chain' && Array.isArray(rule.steps)) {
+        const idx = rule.steps.findIndex(s => (typeof s === 'string' ? s : s && s.relation) === name);
+        if (idx >= 0) {
+          const lim = rule.maxDepth;
+          const limit = lim && typeof lim === 'object' ? lim.value : lim;
+          found = { hop: rule.steps.slice(0, idx), limit: Number.isFinite(limit) ? limit : null };
+          return;
+        }
+      }
+      for (const key of ['union', 'intersection', 'exclusion', 'never', 'always', 'requires', 'when', 'unless']) {
+        const node = rule[key];
+        if (!node) continue;
+        if (Array.isArray(node.rules)) for (const c of node.rules) walk(c);
+        if (Array.isArray(node.union?.rules)) for (const c of node.union.rules) walk(c);
+        if (Array.isArray(node.intersection?.rules)) for (const c of node.intersection.rules) walk(c);
+        if (node.direct) walk(node.direct);
+        if (node.rule) walk(node.rule);
+      }
+    };
+    walk(config);
+    return found;
+  }
+
+  /**
+   * Unroll a self-recursive evidence into a bounded transitive closure.
+   * The recursive chain is removed from the config; the remainder is the base.
+   * Result: union([base, hop+base, hop²+base, …, hop^depth+base]) where the
+   * base is verified as a condition step at each path's terminal node.
+   */
+  _unrollRecursiveEvidence(name, config, hop, depth) {
+    if (hop.length === 0) {
+      this.errors.push(`Recursive evidence '${name}' has an empty recursion hop (no steps before the self-reference).`);
+      return null;
+    }
+    const base = this._extractBase(config, name);
+    if (!base) {
+      this.errors.push(`Recursive evidence '${name}' has no base case — pure recursion cannot grant. Add a non-recursive statement.`);
+      return null;
+    }
+    const rules = [this._deepCloneRule(base)];
+    for (let d = 1; d <= depth; d++) {
+      const steps = [];
+      for (let h = 0; h < d; h++) steps.push(...hop.map(s => this._deepCloneRule(s)));
+      steps.push({ rule: this._deepCloneRule(base), conditionStep: true });
+      rules.push({ type: 'chain', steps, aggregator: 'max', collectValues: true });
+    }
+    return { type: 'logical', union: { rules, aggregator: 'max' } };
+  }
+
+  /**
+   * Remove the recursive chain (the chain containing a self-reference) from an
+   * evidence config and return the remainder as the base case. Returns null if
+   * there is no base (pure recursion).
+   */
+  _extractBase(config, name) {
+    if (config.type === 'chain') {
+      const hasSelf = (config.steps || []).some(s => (typeof s === 'string' ? s : s && s.relation) === name);
+      return hasSelf ? null : this._deepCloneRule(config);
+    }
+    if (config.type === 'logical' && config.intersection) {
+      const remaining = (config.intersection.rules || []).filter(r => {
+        // keep rules that are not (or do not contain) the recursive chain
+        return !this._containsSelfReference(r, name);
+      });
+      if (remaining.length === 0) return null;
+      if (remaining.length === 1) return this._deepCloneRule(remaining[0]);
+      return { type: 'logical', intersection: { rules: remaining.map(r => this._deepCloneRule(r)), aggregator: config.intersection.aggregator || 'min' } };
+    }
+    return this._containsSelfReference(config, name) ? null : this._deepCloneRule(config);
+  }
+
+  _containsSelfReference(rule, name) {
+    return this._findSelfReference(rule, name) !== null;
+  }
+
   /**
    * Recursively rewrite a rule tree, inlining references to derived evidence
    * configs. `stack` holds the evidence names currently being expanded so a
@@ -1054,6 +1168,74 @@ export class RuleGenerator {
       if (out.left?.rule) out.left = { ...out.left, rule: this._resolveRule(out.left.rule, stack) };
       if (out.right?.rule) out.right = { ...out.right, rule: this._resolveRule(out.right.rule, stack) };
     }
+    // Chain steps may reference a derived evidence; expand those steps
+    // (direct evidence → underlying relation, chain evidence → spliced steps).
+    if (rule.type === 'chain' && Array.isArray(out.steps)) {
+      out.steps = this._expandChainSteps(out.steps, stack);
+    }
+    return out;
+  }
+
+  /**
+   * Expand chain steps that reference a derived evidence:
+   *   - direct evidence  → rename the step to the underlying relation
+   *     (member_of(user,*g){ group_read(g,doc) } where group_read = can_view
+   *      becomes step 'can_view');
+   *   - chain evidence   → splice its steps into this chain (flattening)
+   *     (a step that is itself a sub-path becomes its steps, preserving the
+   *      linear source→…→object traversal);
+   *   - logical / defeasible / comparator evidence → only expressible as a
+   *     FINAL condition-gated step (the object is known, so the engine can
+   *     verify the condition at (intermediate, object) instead of traversing
+   *     an edge). Emitted as a `{ rule: <config> }` step the ChainRule
+   *     evaluates as a condition hop. Non-final such steps are a compile
+   *     error: a condition cannot discover intermediate nodes.
+   */
+  _expandChainSteps(steps, stack) {
+    const out = [];
+    for (let idx = 0; idx < steps.length; idx++) {
+      const step = steps[idx];
+      const stepName = typeof step === 'string' ? step : step.relation;
+      if (stepName && this.evidenceNames.has(stepName)) {
+        if (stack.has(stepName)) {
+          this.errors.push(`Cyclic evidence reference involving '${stepName}'. Evidence composition must be acyclic.`);
+          out.push(step);
+          continue;
+        }
+        const referencedConfig = this.generatedRules.get(stepName);
+        if (referencedConfig) {
+          const refStack = new Set(stack);
+          refStack.add(stepName);
+          const resolved = this._resolveRule(referencedConfig, refStack);
+          if (resolved.type === 'direct' && resolved.relation && resolved.relation !== stepName) {
+            out.push(typeof step === 'string'
+              ? resolved.relation
+              : { ...step, relation: resolved.relation });
+            continue;
+          }
+          if (resolved.type === 'chain' && Array.isArray(resolved.steps)) {
+            out.push(...this._expandChainSteps(resolved.steps, refStack));
+            continue;
+          }
+          if (resolved.type === 'relational_comparator' && idx !== steps.length - 1) {
+            // A comparator compares values at (src, candidate) but provides no
+            // candidate set — it cannot enumerate intermediate nodes, so only
+            // a FINAL comparator step (verified at the known object) lowers.
+            this.errors.push(`Chain step '${stepName}' references a comparator evidence at a non-final position. ` +
+              'Comparators can only be the final chain step (the object is known); intermediate positions are not enumerable.');
+            out.push(step);
+            continue;
+          }
+          // Condition step: inline the evidence's config as a rule step. As the
+          // FINAL step the engine verifies it at (intermediate, object); as an
+          // INTERMEDIATE step the engine EXPANDS it from the current node
+          // (rule-based reachability) and continues from each discovered node.
+          out.push({ rule: this._deepCloneRule(resolved), conditionStep: true });
+          continue;
+        }
+      }
+      out.push(step);
+    }
     return out;
   }
 
@@ -1215,16 +1397,23 @@ export class RuleGenerator {
       reverse: false
     };
 
-    // Subject-scoped (unary) predicate call: the call's variable args omit the
-    // evidence's object parameter (banned(user) inside can_open(user, doc)).
-    // Mark _subjectAsObject so the engine checks the relation on the subject
-    // itself — the unary fact's self-edge — instead of (subject, object).
+    // Unary predicate calls check the relation as a self-edge on the call's
+    // subject entity (the graph stores unary facts as self-edges). The subject
+    // entity may be the evidence's SUBJECT or its OBJECT parameter:
+    //   banned(user)   in can_open(user, doc)   -> self-edge on the user
+    //   trusted(other) in peer_trusted(user, other) -> self-edge on the other
+    // Mark _subjectAsObject (subject-as-object on the subject entity) or
+    // _subjectIsObject (the subject entity IS the object parameter) so the
+    // engine rewrites the pair accordingly.
     const evidenceParams = (evidence && evidence.params) || [];
     const objectVar = evidenceParams[1] && evidenceParams[1].name;
+    const argName = a => a && (a.name !== undefined ? a.name : a.value);
     if (objectVar !== undefined) {
-      const hasObjectArg = (expression.args || []).some(a =>
-        a && a.type === 'Variable' && a.name === objectVar);
-      if (!hasObjectArg) {
+      const args = expression.args || [];
+      const hasObjectArg = args.some(a => a && a.type === 'Variable' && a.name === objectVar);
+      if (args.length === 1 && argName(args[0]) === objectVar) {
+        rule._subjectIsObject = true;
+      } else if (!hasObjectArg) {
         rule._subjectAsObject = true;
       }
     }

src/grammar/dsl.peggy

@@ -54,11 +54,14 @@ Definition "A type definition"
     }
 
 Field
-  = name:Identifier _ ":" _ fieldType:Type _ isArray:("[]")? _ behavior:Behavior? _ cache:CacheDirective? {
+  = name:Identifier _ ":" _ fieldType:Type optional:("?")? _ isArray:("[]")? _ behavior:Behavior? _ cache:CacheDirective? {
       return {
         type: "Field",
         name,
         fieldType,
+        // `field: type` is REQUIRED on node insert; `field: type?` is optional.
+        // Presence is enforced by the DSLRuntime when a node is created.
+        required: !optional,
         isArray: !!isArray,
         behavior: behavior || null,
         cache: cache || null
@@ -248,6 +251,13 @@ BehaviorAnnotation
   = "BEHAVES" __ "AS" __ behavior:("edge" / "transitive" / "hierarchical" / "symmetrical_graph") {
       return { type: "BehaviorAnnotation", behavior };
     }
+  / "BEHAVES" __ "{" _ behavior:(TTLBehavior) _ "}" {
+      // Fact-level freshness: `fact balance(user, amount) BEHAVES { ttl 1h }`
+      // declares the relation's value-freshness window, which the runtime uses
+      // as the provider-result cache TTL. The behavior is wrapped like the
+      // `BEHAVES AS` form so consumers read `behavior.behaviorType`.
+      return { type: "BehaviorAnnotation", behavior };
+    }
 
 FactProperty
   = "transitive" { return "transitive"; }
@@ -385,7 +395,7 @@ Boolean "A boolean literal"
   = value:("true" / "false") { return { type: "Literal", value: value === "true" }; }
 
 Duration "A time duration literal"
-  = value:([0-9]+ ("h" / "d" / "w" / "m")) { return { type: "Literal", value: text(), unit: text().slice(-1) }; }
+  = value:([0-9]+ ("s" / "m" / "h" / "d" / "w")) { return { type: "Literal", value: text(), unit: text().slice(-1) }; }
 
 
 // -- Core Tokens & Whitespace --

src/runtime/DSLRuntime.js

@@ -1,6 +1,6 @@
 import { DSLCompiler } from '../DSLCompiler.js';
 
-const PRIMITIVE_TYPES = new Set(['string', 'number', 'boolean']);
+const VALUE_TYPES = new Set(['string', 'number', 'boolean', 'timestamp', 'duration', 'object', 'any']);
 
 /**
  * DSLRuntime — higher-order wrapper combining the Evidence DSL with an
@@ -12,13 +12,19 @@ const PRIMITIVE_TYPES = new Set(['string', 'number', 'boolean']);
  * check). A raw Arbiter accepts untyped inserts; this wrapper adds the
  * DSL-informed layer:
  *
- *   - addNode / updateNodeData / addRelation / updateRelation validate their
- *     arguments against the compiled schema — known types, known relations,
- *     matching param types, typed field values — before mutating the arbiter.
- *   - check() validates the request, derives the injectable facts the
- *     evidence requires (its partial-graph requirements), retrieves the
- *     missing facts through caller-provided data callbacks, injects them into
- *     a partial graph, then delegates to the arbiter.
+ *   - schema introspection: getSchema() exposes the compiled type system
+ *     (entity types/fields, facts, evidence, dependencies, providers);
+ *   - typed mutations: addNode / updateNodeData / addRelation / updateRelation
+ *     validate their arguments against the compiled schema — known types,
+ *     known relations, matching param types, typed field values — before
+ *     mutating the arbiter; removeNode / removeRelation pass through;
+ *   - per-relation data retrieval: registerFact(relation, asyncFn) registers a
+ *     provider that retrieves the missing partial-graph edges for a fact; a
+ *     bounded retrieval loop runs providers to a fixed point so a provider's
+ *     edges can satisfy another required fact;
+ *   - DSL-informed check: derives the evidence's injectable facts, retrieves
+ *     them via providers, injects them into a partial graph, and delegates to
+ *     the arbiter; require() throws on denial for middleware use.
  *
  * Trust boundary follows the core: caller-supplied evidence (partial graph /
  * provider results) is trusted, never policed; only structure is validated.
@@ -41,8 +47,27 @@ export class DSLRuntime {
     this.strictTypes = options.policy?.strictTypes !== false;
     this.program = null;
     this.types = new Map();      // typeName -> { fields: Map(field -> {type,isArray}) }
-    this.relations = new Map();  // relation -> { kind: 'fact'|'evidence', params, injectable }
+    this.relations = new Map();  // relation -> { kind: 'fact'|'evidence', params, injectable, ttlMs }
     this.dependsOn = new Map();  // evidence relation -> Set(fact relations)
+
+    // Provider-result cache: relation|subject|object -> { edges, fetchedAt }.
+    // Provider retrieval is a data-store read (balance lookups, session
+    // checks, etc.) — caching results with a time expiry avoids hammering the
+    // underlying store on every check. The clock is injectable (default wall
+    // clock) and drives cache freshness, mirroring the core's unpinned-clock
+    // contract.
+    this.providerCache = new Map();
+    this.clock = typeof options.clock === 'function' ? options.clock : (() => Date.now());
+    // Default provider-result TTL in ms (0 disables caching).
+    this.defaultProviderCacheTTL = options.policy?.providerCacheTTL ?? options.providerCacheTTL ?? 30_000;
+    // Provider caching is a STORE-RETRIEVAL cache (wall-clock), deliberately
+    // independent of the caller's decision `{ now }` — a provider returns the
+    // store's current data, not a time-travel snapshot. Callers who pin time
+    // or otherwise want fresh retrieval can disable it per-check
+    // (options.cacheProviderResults: false) or globally (policy).
+    this.cacheProviderResults = options.policy?.cacheProviderResults ?? options.cacheProviderResults ?? true;
+    // Per-fact overrides (ms). DSL-declared ttl behaviors are indexed here too.
+    this.factTTLs = new Map(Object.entries(options.factTTLs || {}));
   }
 
   /**
@@ -62,6 +87,44 @@ export class DSLRuntime {
     return this;
   }
 
+  // ---------------------------------------------------------------------------
+  // Schema introspection
+  // ---------------------------------------------------------------------------
+
+  /**
+   * A serializable snapshot of the compiled type system: entity types with
+   * typed fields, facts, evidence (with their dependencies), and registered
+   * providers. Callers can use this to render forms, build clients, or audit
+   * a compiled program without reaching into the internal Maps.
+   */
+  getSchema() {
+    const types = [...this.types.entries()].map(([name, { fields }]) => ({
+      name,
+      fields: [...fields.entries()].map(([fieldName, f]) => ({
+        name: fieldName,
+        type: f.type,
+        isArray: f.isArray,
+        required: f.required !== false
+      }))
+    }));
+    const facts = [...this.relations.entries()]
+      .filter(([, r]) => r.kind === 'fact')
+      .map(([name, r]) => ({ name, params: r.params, injectable: r.injectable }));
+    const evidence = [...this.relations.entries()]
+      .filter(([, r]) => r.kind === 'evidence')
+      .map(([name, r]) => ({
+        name,
+        params: r.params,
+        dependsOn: [...(this.dependsOn.get(name) || [])]
+      }));
+    return { types, facts, evidence, providers: this.registeredFacts() };
+  }
+
+  /** All relation names declared by the program (facts + evidence). */
+  relationNames() {
+    return [...this.relations.keys()];
+  }
+
   _indexSchema() {
     this.types.clear();
     this.relations.clear();
@@ -70,16 +133,18 @@ export class DSLRuntime {
     for (const def of this.program.definitions || []) {
       const fields = new Map();
       for (const field of def.fields || []) {
-        fields.set(field.name, { type: field.fieldType, isArray: !!field.isArray });
+        fields.set(field.name, { type: field.fieldType, isArray: !!field.isArray, required: field.required !== false });
       }
       this.types.set(def.name, { fields });
     }
 
     for (const fact of this.program.facts || []) {
+      const ttlMs = this._ttlFromBehavior(fact.behavior);
       this.relations.set(fact.name, {
         kind: 'fact',
         params: (fact.params || []).map(p => ({ name: p.name, type: p.paramType, isArray: !!p.isArray })),
-        injectable: !!fact.injectable
+        injectable: !!fact.injectable,
+        ttlMs
       });
     }
 
@@ -103,7 +168,11 @@ export class DSLRuntime {
           if (rule.computedRelation) deps.add(rule.computedRelation);
         }
         if (rule.type === 'chain' && Array.isArray(rule.steps)) {
-          for (const s of rule.steps) deps.add(typeof s === 'string' ? s : s.relation);
+          for (const s of rule.steps) {
+            if (typeof s === 'string') deps.add(s);
+            else if (s && s.relation) deps.add(s.relation);
+            else if (s && s.rule) collect(s.rule);
+          }
         }
         if (rule.type === 'parent' && rule.parentRelation) deps.add(rule.parentRelation);
         if (rule.type === 'multi_hop' && rule.relation) deps.add(rule.relation);
@@ -132,12 +201,178 @@ export class DSLRuntime {
     }
   }
 
+  // ---------------------------------------------------------------------------
+  // Provider registration (per-relation data retrieval)
+  // ---------------------------------------------------------------------------
+
+  /**
+   * Register (or replace) an async provider for a relation name. When a check
+   * needs that relation's facts and they are not in the graph, the provider is
+   * invoked to retrieve the missing partial-graph edges.
+   *
+   * @param {string} relation - fact relation name
+   * @param {Function} provider - async (subject, object, ctx) => edges
+   */
+  registerFact(relation, provider) {
+    if (typeof provider !== 'function') {
+      throw new Error(`DSLRuntime: provider for '${relation}' must be a function`);
+    }
+    this.factProviders[relation] = provider;
+    // A new provider supersedes any cached retrieval for this fact.
+    this.invalidateProviderCache(relation);
+    return this;
+  }
+
+  /** Remove a registered provider. */
+  unregisterFact(relation) {
+    delete this.factProviders[relation];
+    this.invalidateProviderCache(relation);
+    return this;
+  }
+
+  /** Relation names that currently have a registered provider. */
+  registeredFacts() {
+    return Object.keys(this.factProviders);
+  }
+
+  // ---------------------------------------------------------------------------
+  // Provider-result caching
+  // ---------------------------------------------------------------------------
+
+  /**
+   * Set a per-fact provider-result TTL (ms). Overrides the policy default and
+   * the DSL-declared ttl behavior for that fact.
+   */
+  setFactTTL(relation, ms) {
+    this.factTTLs.set(relation, ms);
+    return this;
+  }
+
+  /** The effective provider-result TTL (ms) for a fact: DSL > per-fact > policy default. */
+  _ttlFor(relation) {
+    if (this.factTTLs.has(relation)) return this.factTTLs.get(relation);
+    const meta = this.relations.get(relation);
+    if (meta && meta.ttlMs != null) return meta.ttlMs;
+    return this.defaultProviderCacheTTL;
+  }
+
+  /**
+   * Invalidate cached provider results — all, or for a single relation.
+   * Callers use this when the underlying data store changes out-of-band.
+   */
+  invalidateProviderCache(relation) {
+    if (relation === undefined) {
+      this.providerCache.clear();
+      return this;
+    }
+    const prefix = `${relation}\u0000`;
+    for (const key of [...this.providerCache.keys()]) {
+      if (key.startsWith(prefix)) this.providerCache.delete(key);
+    }
+    return this;
+  }
+
+  _providerCacheKey(relation, subject, object) {
+    return `${relation}\u0000${subject}\u0000${object}`;
+  }
+
+  _providerCacheGet(relation, subject, object) {
+    const ttl = this._ttlFor(relation);
+    if (ttl <= 0) return null;
+    const entry = this.providerCache.get(this._providerCacheKey(relation, subject, object));
+    if (!entry) return null;
+    if (this.clock() - entry.fetchedAt >= ttl) {
+      this.providerCache.delete(this._providerCacheKey(relation, subject, object));
+      return null;
+    }
+    return entry;
+  }
+
+  _providerCacheSet(relation, subject, object, edges) {
+    const ttl = this._ttlFor(relation);
+    if (ttl <= 0) return;
+    this.providerCache.set(this._providerCacheKey(relation, subject, object), {
+      edges,
+      fetchedAt: this.clock()
+    });
+  }
+
+  /** Convert a DSL `BEHAVES { ttl <duration> }` behavior (or `BEHAVES AS`) into ms. */
+  _ttlFromBehavior(behavior) {
+    if (!behavior || typeof behavior !== 'object') return null;
+    const b = behavior.behavior || behavior;
+    if (b && b.behaviorType === 'ttl' && b.duration) {
+      const n = parseInt(String(b.duration.value), 10);
+      const mult = { s: 1000, m: 60_000, h: 3600_000, d: 86_400_000, w: 604_800_000 }[b.duration.unit];
+      if (!Number.isNaN(n) && mult) return n * mult;
+    }
+    return null;
+  }
+
+  /**
+   * Normalize a provider result (boolean / number / { possibility, value } /
+   * array of edge objects) into an array of partial-graph edge objects. The
+   * destination follows the DSL fact's declared shape: unary and value-carrying
+   * facts are self-edges on the subject; binary entity facts go subject → object.
+   * Provider-returned edges are validated against the fact's declared typing:
+   * a value-carrying fact must return an object with a value of the declared
+   * type, and possibilities must be in [0, 1]. A violation throws — it is a
+   * provider-authoring error, not a denial.
+   */
+  _normalizeProviderEdges(result, factMeta, fact, user, object) {
+    const edges = Array.isArray(result) ? result : [result];
+    const secondParamType = factMeta.params[1] && factMeta.params[1].type;
+    const isValueFact = factMeta.params.length >= 2 && this._isValueType(secondParamType);
+    const defaultDst = isValueFact ? user : (factMeta.params.length >= 2 ? object : user);
+    const label = `provider for '${fact}'`;
+    const out = [];
+    for (const edge of edges) {
+      const normalized = typeof edge === 'boolean' || typeof edge === 'number'
+        ? (() => {
+            if (isValueFact) {
+              throw new Error(`DSLRuntime: ${label} is a value-carrying fact — return { value, possibility } (got a bare ${typeof edge === 'number' ? 'number' : 'boolean'})`);
+            }
+            const possibility = edge === true ? 1 : edge;
+            this._checkPossibility(possibility, label);
+            return { src: user, dst: defaultDst, possibility };
+          })()
+        : (() => {
+            const possibility = edge.possibility ?? 1;
+            this._checkPossibility(possibility, label);
+            if (edge.value !== undefined) {
+              if (!isValueFact) {
+                throw new Error(`DSLRuntime: ${label} returned a value for a non-value fact '${fact}'`);
+              }
+              this._checkScalarValue(secondParamType, edge.value, `${label}.value`);
+            } else if (isValueFact) {
+              throw new Error(`DSLRuntime: ${label} must supply a 'value' of type ${secondParamType}`);
+            }
+            return {
+              ...(edge.relation ? { relation: edge.relation } : {}),
+              src: edge.src ?? user,
+              dst: edge.dst ?? defaultDst,
+              possibility,
+              ...(edge.value !== undefined ? { value: edge.value } : {}),
+              ...(edge.reliability !== undefined ? { reliability: edge.reliability } : {})
+            };
+          })();
+      out.push(normalized);
+    }
+    return out;
+  }
+
+  _checkPossibility(possibility, label) {
+    if (typeof possibility !== 'number' || !Number.isFinite(possibility) || possibility < 0 || possibility > 1) {
+      throw new Error(`DSLRuntime: ${label} returned invalid possibility ${possibility} (expected a number in [0, 1])`);
+    }
+  }
+
   // ---------------------------------------------------------------------------
   // Schema validation helpers
   // ---------------------------------------------------------------------------
 
-  _isPrimitive(typeName) {
-    return PRIMITIVE_TYPES.has(typeName);
+  _isValueType(typeName) {
+    return VALUE_TYPES.has(typeName);
   }
 
   _nodeType(key) {
@@ -154,7 +389,7 @@ export class DSLRuntime {
   }
 
   _checkNodeType(key, expectedType, position) {
-    if (this._isPrimitive(expectedType)) return; // value positions are validated separately
+    if (this._isValueType(expectedType)) return; // value positions are validated separately
     const actual = this._nodeType(key);
     if (actual === null) {
       this._checkNodeExists(key, position);
@@ -180,7 +415,9 @@ export class DSLRuntime {
     const ok = type === 'string' ? typeof value === 'string'
       : type === 'number' ? typeof value === 'number'
       : type === 'boolean' ? typeof value === 'boolean'
-      : true; // entity-typed fields accept any key
+      : (type === 'timestamp' || type === 'duration')
+        ? (typeof value === 'number' || typeof value === 'string')
+        : true; // object / any / entity-typed fields accept any value
     if (!ok) {
       throw new Error(`DSLRuntime: field '${path}' must be ${type}, got ${typeof value}`);
     }
@@ -198,11 +435,18 @@ export class DSLRuntime {
     if (this.types.has(typeName)) {
       const { fields } = this.types.get(typeName);
       for (const [name, field] of fields) {
+        // Required fields must be present on insert (`field: type` in the DSL;
+        // `field?: type` marks a field optional).
+        if (field.required && data[name] === undefined) {
+          throw new Error(`DSLRuntime: missing required field '${typeName}.${name}' on node insert`);
+        }
         if (data[name] !== undefined) this._checkFieldValue(field, data[name], `${typeName}.${name}`);
       }
     } else if (this.strictTypes) {
       throw new Error(`DSLRuntime: unknown type '${typeName}'`);
     }
+    // A graph mutation can make previously-retrieved facts stale.
+    this.invalidateProviderCache();
     return this.arbiter.addNode(key, typeName, data);
   }
 
@@ -217,9 +461,19 @@ export class DSLRuntime {
         if (data[name] !== undefined) this._checkFieldValue(field, data[name], `${typeName}.${name}`);
       }
     }
+    this.invalidateProviderCache();
     return this.arbiter.updateNodeData(key, data);
   }
 
+  /** Remove a node (passthrough to the arbiter's node manager). */
+  removeNode(key) {
+    this.invalidateProviderCache();
+    if (this.arbiter.nodeManager && typeof this.arbiter.nodeManager.removeNode === 'function') {
+      return this.arbiter.nodeManager.removeNode(key);
+    }
+    return this.arbiter.removeNode?.(key);
+  }
+
   _relationOrThrow(relation) {
     const meta = this.relations.get(relation);
     if (!meta) {
@@ -239,6 +493,7 @@ export class DSLRuntime {
     if (meta) {
       this._validateRelationEndpoints(relation, meta, src, dst, attrs);
     }
+    this.invalidateProviderCache();
     return this.arbiter.addRelation(src, relation, dst, attrs);
   }
 
@@ -250,10 +505,17 @@ export class DSLRuntime {
     if (meta) {
       this._validateRelationEndpoints(relation, meta, src, dst, attrs);
     }
+    this.invalidateProviderCache();
     this.arbiter.removeRelation(src, relation, dst);
     return this.arbiter.addRelation(src, relation, dst, attrs);
   }
 
+  /** Remove a relation edge (passthrough to the arbiter). */
+  removeRelation(src, relation, dst) {
+    this.invalidateProviderCache();
+    return this.arbiter.removeRelation(src, relation, dst);
+  }
+
   _validateRelationEndpoints(relation, meta, src, dst, attrs) {
     const params = meta.params;
     if (params.length === 0) {
@@ -261,14 +523,14 @@ export class DSLRuntime {
     }
     // First param is always the subject (entity).
     const subjectType = params[0].type;
-    if (this._isPrimitive(subjectType)) {
+    if (this._isValueType(subjectType)) {
       throw new Error(`DSLRuntime: relation '${relation}' subject param must be an entity type, got '${subjectType}'`);
     }
     this._checkNodeType(src, subjectType, 'subject');
 
     if (params.length >= 2) {
       const secondType = params[1].type;
-      if (this._isPrimitive(secondType)) {
+      if (this._isValueType(secondType)) {
         // Value-carrying fact (e.g. session(user, token: string)): the value
         // lives on the edge's `value` field; the graph edge is a self-edge on
         // the subject so the value is discoverable by value extraction.
@@ -309,6 +571,13 @@ export class DSLRuntime {
    * evidence's injectable facts, inject them into a partial graph, and delegate
    * to the arbiter.
    *
+   * Providers run in a bounded fixed-point loop: each round invokes the
+   * provider for every required fact whose edges are not yet in the partial
+   * graph. Because a provider may return edges for relations other than its
+   * own name, an edge injected in one round can satisfy another required fact
+   * (or unblock another provider) in a later round. The loop stops when a
+   * round injects no new relation or the round budget is exhausted.
+   *
    * @param {string} user - subject key
    * @param {string} relation - evidence (or fact) relation name
    * @param {string} object - object key
@@ -316,71 +585,110 @@ export class DSLRuntime {
    * @param {object} options.partialGraph - caller-supplied partial graph edges
    *   ({ relations: [{ src, relation, dst, possibility, value }], nodes, challenges })
    * @param {object} options.factProviders - per-call provider overrides
+   *   (merged over registered providers)
+   * @param {number} options.maxProviderRounds - fixed-point loop budget (default 3)
    * @returns {object} core check result extended with { requiredFacts, providedFacts, missingFacts }
    */
   async check(user, relation, object, options = {}) {
     const meta = this.relations.get(relation);
     if (!meta) {
       if (this.strictTypes) throw new Error(`DSLRuntime: unknown relation '${relation}'`);
-    } else if (meta.kind === 'evidence') {
-      if (meta.params.length === 2) {
-        this._checkNodeType(user, meta.params[0].type, 'subject');
-        this._checkNodeType(object, meta.params[1].type, 'object');
-      }
+    } else if (meta.params.length === 2) {
+      this._checkNodeType(user, meta.params[0].type, 'subject');
+      this._checkNodeType(object, meta.params[1].type, 'object');
+    } else if (meta.params.length === 1) {
+      this._checkNodeType(user, meta.params[0].type, 'subject');
     }
 
-    const required = this.requiredFacts(relation);
-    const providers = options.factProviders || this.factProviders;
-    const injectedRelations = [];
-    const missingFacts = [];
+    // Retrieval set: for an evidence, the injectable facts it depends on; for
+    // a direct FACT check, the fact itself is the retrieval target (its
+    // provider, if registered, supplies the edge — checking `owns` directly
+    // must consult the `owns` provider, not only evidence-mediated checks).
+    const required = new Set(this.requiredFacts(relation));
+    if (meta && meta.kind === 'fact') required.add(relation);
+    const requiredList = [...required];
+    const providers = { ...this.factProviders, ...(options.factProviders || {}) };
+    const maxRounds = options.maxProviderRounds ?? 3;
     const partialRelations = [];
+    const injectedRelations = []; // { relation, edges, round }
+    const missingFacts = [];
+    const satisfied = new Set();  // facts whose edges are in the partial graph
 
     if (options.partialGraph && Array.isArray(options.partialGraph.relations)) {
-      partialRelations.push(...options.partialGraph.relations);
+      for (const rel of options.partialGraph.relations) {
+        partialRelations.push(rel);
+        if (rel && rel.relation) satisfied.add(rel.relation);
+      }
     }
 
-    for (const fact of required) {
-      const factMeta = this.relations.get(fact);
-      const provider = providers[fact];
-      let result = null;
-      let error = null;
-      if (typeof provider === 'function') {
-        try {
-          result = await provider(user, object, { relation: fact, params: factMeta.params, runtime: this, options });
-        } catch (err) {
-          error = err;
+    // Fixed-point provider retrieval loop.
+    for (let round = 1; round <= maxRounds; round++) {
+      let newRelationsThisRound = 0;
+      for (const fact of requiredList) {
+        if (satisfied.has(fact)) continue;
+        const factMeta = this.relations.get(fact);
+        const provider = providers[fact];
+
+        // Provider-result cache: reuse fresh edges without re-invoking the
+        // data store. A cached entry stores the NORMALIZED edges. Per-check
+        // provider overrides are one-off observations — they bypass the cache
+        // entirely (no read, no write) so a fresh override is never masked by
+        // a cached registered-provider result, nor does it pollute the cache.
+        // options.cacheProviderResults:false (or the policy default) disables
+        // the cache for this check.
+        const cachingEnabled = options.cacheProviderResults ?? this.cacheProviderResults;
+        const isPerCheckOverride = !!(options.factProviders && fact in options.factProviders);
+        const cacheHit = (cachingEnabled && !isPerCheckOverride) ? this._providerCacheGet(fact, user, object) : null;
+        let edges = null;
+        let fromCache = false;
+        if (cacheHit) {
+          edges = cacheHit.edges;
+          fromCache = true;
+        } else if (typeof provider === 'function') {
+          let result = null;
+          let error = null;
+          try {
+            result = await provider(user, object, {
+              relation: fact,
+              params: factMeta.params,
+              runtime: this,
+              options,
+              round,
+              alreadyInjected: [...satisfied]
+            });
+          } catch (err) {
+            error = err;
+          }
+          if (error) {
+            missingFacts.push({ relation: fact, reason: error.message });
+            satisfied.add(fact);
+            continue;
+          }
+          if (result === false || result === null || result === undefined) {
+            missingFacts.push({ relation: fact, reason: 'not_provided' });
+            satisfied.add(fact);
+            continue;
+          }
+          edges = this._normalizeProviderEdges(result, factMeta, fact, user, object);
+          if (cachingEnabled && !isPerCheckOverride) this._providerCacheSet(fact, user, object, edges);
+        } else {
+          missingFacts.push({ relation: fact, reason: 'no_provider' });
+          satisfied.add(fact);
+          continue;
         }
+
+        // A provider may return edges for relations other than its own; the
+        // injected relation names satisfy those facts too (fixed point).
+        for (const normalized of edges) {
+          const injectedRelation = normalized.relation ?? fact;
+          partialRelations.push({ relation: injectedRelation, ...normalized });
+          satisfied.add(injectedRelation);
+        }
+        injectedRelations.push({ relation: fact, edges: edges.length, round, cacheHit: fromCache });
+        newRelationsThisRound += edges.length;
+        satisfied.add(fact);
       }
-      if (error) {
-        missingFacts.push({ relation: fact, reason: error.message });
-        continue;
-      }
-      if (result === false || result === null || result === undefined) {
-        missingFacts.push({ relation: fact, reason: 'not_provided' });
-        continue;
-      }
-      const edges = Array.isArray(result) ? result : [result];
-      // Resolve the edge destination the same way the DSL declares the fact:
-      //   - unary fact (1 param)        -> self-edge on the subject
-      //   - value fact (2nd param value) -> self-edge on the subject carrying the value
-      //   - binary entity fact          -> subject → object
-      const secondParamType = factMeta.params[1] && factMeta.params[1].type;
-      const defaultDst = factMeta.params.length >= 2 && this._isPrimitive(secondParamType)
-        ? user
-        : (factMeta.params.length >= 2 ? object : user);
-      for (const edge of edges) {
-        const normalized = typeof edge === 'boolean' || typeof edge === 'number'
-          ? { src: user, dst: defaultDst, possibility: edge === true ? 1 : edge }
-          : {
-            src: edge.src ?? user,
-            dst: edge.dst ?? defaultDst,
-            possibility: edge.possibility ?? 1,
-            ...(edge.value !== undefined ? { value: edge.value } : {}),
-            ...(edge.reliability !== undefined ? { reliability: edge.reliability } : {})
-          };
-        partialRelations.push({ relation: fact, ...normalized });
-      }
-      injectedRelations.push({ relation: fact, edges: edges.length });
+      if (newRelationsThisRound === 0) break;
     }
 
     const checkOptions = { ...options };
@@ -395,9 +703,24 @@ export class DSLRuntime {
 
     return {
       ...result,
-      requiredFacts: required,
+      requiredFacts: requiredList,
       providedFacts: injectedRelations.map(r => r.relation),
       missingFacts
     };
   }
+
+  /**
+   * Check and throw on denial — convenience for middleware / guards.
+   * @returns {object} the check result on success.
+   * @throws {Error} with `.result` attached when the decision denies.
+   */
+  async require(user, relation, object, options = {}) {
+    const result = await this.check(user, relation, object, options);
+    if (result.possibility <= 0) {
+      const error = new Error(`DSLRuntime: authorization denied for '${relation}' (${result.reason || 'denied'})`);
+      error.result = result;
+      throw error;
+    }
+    return result;
+  }
 }

tests/ChainConditionStep.test.js

@@ -0,0 +1,129 @@
+/**
+ * tests/ChainConditionStep.test.js — a chain whose FINAL (object-side) hop
+ * references a defeasible/logical evidence. The compiler lowers it to a
+ * condition step: `{ rule: <config>, conditionStep: true }`, which the engine
+ * verifies at (intermediate, object) rather than traversing an edge.
+ *
+ * Only the final step may be a condition (the object is known); an
+ * intermediate condition cannot discover nodes and is a compile error.
+ */
+import { describe, it } from 'node:test';
+import assert from 'node:assert/strict';
+import { Arbiter } from '@arbiter/core';
+import { DSLCompiler } from '../src/DSLCompiler.js';
+
+const DEFS = `
+  definition Employee { id: string }
+  definition Group { id: string }
+  definition Doc { id: string }
+  fact member_of(user: Employee, group: Group)
+  fact can_view(group: Group, doc: Doc)
+  fact banned(group: Group)
+  fact can_edit(group: Group, doc: Doc)
+`;
+
+function compile(dsl, name = 'chain-cond') {
+  const arb = new Arbiter();
+  const compiler = new DSLCompiler(arb);
+  const result = compiler.compile(dsl, name);
+  return { arb, result };
+}
+
+describe('Chain condition step (logical evidence as final hop)', () => {
+  it('lowers a defeasible final step to a condition step and grants', () => {
+    const { arb, result } = compile(`
+      ${DEFS}
+      evidence gated(group: Group, doc: Doc) { WHEN can_view(group, doc) UNLESS banned(group) }
+      evidence can_via(user: Employee, doc: Doc) { member_of(user, *g) { gated(g, doc) } }
+    `);
+    assert.ok(result.success, JSON.stringify(result.errors));
+    const steps = arb.relationConfigs.get('can_via').steps;
+    assert.equal(steps[0], 'member_of');
+    assert.equal(steps[1].conditionStep, true);
+    assert.equal(steps[1].rule.type, 'logical');
+    // transitive dependency collection through the condition step
+    assert.deepEqual(arb.relationConfigs.get('can_via').dependsOn, ['member_of', 'can_view', 'banned']);
+
+    arb.addNode('u:1', 'Employee'); arb.addNode('g:1', 'Group'); arb.addNode('doc:9', 'Doc');
+    arb.addRelation('u:1', 'member_of', 'g:1', { possibility: 1.0 });
+    arb.addRelation('g:1', 'can_view', 'doc:9', { possibility: 0.7 });
+    assert.equal(arb.check('u:1', 'can_via', 'doc:9').possibility, 0.7);
+
+    // banning the intermediate defeats the condition hop
+    arb.addRelation('g:1', 'banned', 'g:1', { possibility: 1.0 });
+    assert.equal(arb.check('u:1', 'can_via', 'doc:9').possibility, 0);
+  });
+
+  it('supports ALWAYS/NEVER evidence as a condition step', () => {
+    const { arb, result } = compile(`
+      ${DEFS}
+      evidence gated(group: Group, doc: Doc) { ALWAYS can_edit(group, doc) }
+      evidence can_via(user: Employee, doc: Doc) { member_of(user, *g) { gated(g, doc) } }
+    `);
+    assert.ok(result.success, JSON.stringify(result.errors));
+    const steps = arb.relationConfigs.get('can_via').steps;
+    assert.equal(steps[1].conditionStep, true);
+    arb.addNode('u:1', 'Employee'); arb.addNode('g:1', 'Group'); arb.addNode('doc:9', 'Doc');
+    arb.addRelation('u:1', 'member_of', 'g:1', { possibility: 1.0 });
+    arb.addRelation('g:1', 'can_edit', 'doc:9', { possibility: 0.6 });
+    assert.equal(arb.check('u:1', 'can_via', 'doc:9').possibility, 0.6);
+    arb.removeRelation('g:1', 'can_edit', 'doc:9');
+    assert.equal(arb.check('u:1', 'can_via', 'doc:9').possibility, 0);
+  });
+
+  it('keeps the condition evidence checkable in its own right', () => {
+    const { arb, result } = compile(`
+      ${DEFS}
+      evidence gated(group: Group, doc: Doc) { WHEN can_view(group, doc) UNLESS banned(group) }
+      evidence can_via(user: Employee, doc: Doc) { member_of(user, *g) { gated(g, doc) } }
+    `);
+    assert.ok(result.success, JSON.stringify(result.errors));
+    arb.addNode('g:1', 'Group'); arb.addNode('doc:9', 'Doc');
+    arb.addRelation('g:1', 'can_view', 'doc:9', { possibility: 0.8 });
+    assert.equal(arb.check('g:1', 'gated', 'doc:9').possibility, 0.8);
+  });
+
+  it('parallel intermediates aggregate through the condition step', () => {
+    const { arb, result } = compile(`
+      ${DEFS}
+      evidence gated(group: Group, doc: Doc) { can_view(group, doc) }
+      evidence can_via(user: Employee, doc: Doc) { member_of(user, *g) { gated(g, doc) } }
+    `);
+    assert.ok(result.success, JSON.stringify(result.errors));
+    arb.addNode('u:1', 'Employee'); arb.addNode('g:1', 'Group'); arb.addNode('g2:2', 'Group'); arb.addNode('doc:9', 'Doc');
+    arb.addRelation('u:1', 'member_of', 'g:1', { possibility: 0.5 });
+    arb.addRelation('g:1', 'can_view', 'doc:9', { possibility: 0.7 });
+    arb.addRelation('u:1', 'member_of', 'g2:2', { possibility: 1.0 });
+    arb.addRelation('g2:2', 'can_view', 'doc:9', { possibility: 0.8 });
+    // max over paths: min(0.5,0.7)=0.5, min(1.0,0.8)=0.8 -> 0.8
+    assert.equal(arb.check('u:1', 'can_via', 'doc:9').possibility, 0.8);
+  });
+
+  it('expands an INTERMEDIATE condition step via rule-based reachability', () => {
+    const { arb, result } = compile(`
+      definition Employee { id: string }
+      definition Doc { id: string }
+      fact peer(user: Employee, other: Employee)
+      fact trusted(other: Employee)
+      fact can_read(user: Employee, doc: Doc)
+      evidence peer_trusted(user: Employee, other: Employee) { WHEN peer(user, other) UNLESS trusted(other) }
+      evidence can_access(user: Employee, doc: Doc) { peer_trusted(user, *p) { can_read(p, doc) } }
+    `);
+    assert.ok(result.success, JSON.stringify(result.errors));
+    const steps = arb.relationConfigs.get('can_access').steps;
+    assert.equal(steps[0].conditionStep, true);
+    assert.equal(steps[0].rule.type, 'logical');
+
+    arb.addNode('u:1', 'Employee'); arb.addNode('p:1', 'Employee'); arb.addNode('p:2', 'Employee'); arb.addNode('doc:9', 'Doc');
+    arb.addRelation('u:1', 'peer', 'p:1', { possibility: 1.0 });
+    arb.addRelation('u:1', 'peer', 'p:2', { possibility: 1.0 });
+    arb.addRelation('p:1', 'trusted', 'p:1', { possibility: 1.0 }); // p:1 filtered
+    arb.addRelation('p:1', 'can_read', 'doc:9', { possibility: 0.9 });
+    arb.addRelation('p:2', 'can_read', 'doc:9', { possibility: 0.7 });
+    // only untrusted peer p:2 survives the intermediate condition -> 0.7
+    assert.equal(arb.check('u:1', 'can_access', 'doc:9').possibility, 0.7);
+    // trusting p:2 too removes all intermediates -> 0
+    arb.addRelation('p:2', 'trusted', 'p:2', { possibility: 1.0 });
+    assert.equal(arb.check('u:1', 'can_access', 'doc:9').possibility, 0);
+  });
+});

tests/ChainStepComposition.test.js

@@ -0,0 +1,127 @@
+/**
+ * tests/ChainStepComposition.test.js — evidence composition inside CHAIN
+ * steps. A chain step that references a derived evidence is expanded at
+ * compile time:
+ *   - a DIRECT evidence step → renamed to its underlying relation
+ *     (member_of(user,*g){ group_read(g,doc) } where group_read = can_view
+ *      becomes step 'can_view');
+ *   - a CHAIN evidence step → its steps are spliced into the parent chain
+ *     (a sub-path flattens into the linear source→…→object traversal);
+ *   - a DEFEASIBLE / LOGICAL / COMPARATOR evidence step is not an edge
+ *     traversal and is rejected at compile time;
+ *   - cycles and self-references through chain steps are compile errors.
+ */
+import { describe, it } from 'node:test';
+import assert from 'node:assert/strict';
+import { Arbiter } from '@arbiter/core';
+import { DSLCompiler } from '../src/DSLCompiler.js';
+
+const DEFS = `
+  definition Employee { id: string }
+  definition Group { id: string }
+  definition Doc { id: string }
+  fact member_of(user: Employee, group: Group)
+  fact group_has(group: Group, sub: Group)
+  fact can_view(group: Group, doc: Doc)
+  fact can_access(group: Group, doc: Doc)
+  fact banned(group: Group)
+`;
+
+function compile(dsl, name = 'chain-compose') {
+  const arb = new Arbiter();
+  const compiler = new DSLCompiler(arb);
+  const result = compiler.compile(dsl, name);
+  return { arb, result };
+}
+
+describe('Chain step composition', () => {
+  it('renames a direct-evidence chain step to its underlying relation', () => {
+    const { arb, result } = compile(`
+      ${DEFS}
+      evidence group_read(group: Group, doc: Doc) { can_view(group, doc) }
+      evidence can_via(user: Employee, doc: Doc) { member_of(user, *g) { group_read(g, doc) } }
+    `);
+    assert.ok(result.success, JSON.stringify(result.errors));
+    // step 'group_read' → 'can_view'
+    assert.deepEqual(arb.relationConfigs.get('can_via').steps, ['member_of', 'can_view']);
+    arb.addNode('u:1', 'Employee'); arb.addNode('g:1', 'Group'); arb.addNode('doc:9', 'Doc');
+    arb.addRelation('u:1', 'member_of', 'g:1', { possibility: 1.0 });
+    arb.addRelation('g:1', 'can_view', 'doc:9', { possibility: 0.7 });
+    assert.equal(arb.check('u:1', 'can_via', 'doc:9').possibility, 0.7);
+  });
+
+  it('splices a chain-evidence step into the parent chain', () => {
+    const { arb, result } = compile(`
+      ${DEFS}
+      evidence group_enter(group: Group, doc: Doc) { group_has(group, *s) { can_access(s, doc) } }
+      evidence can_deep(user: Employee, doc: Doc) { member_of(user, *g) { group_enter(g, doc) } }
+    `);
+    assert.ok(result.success, JSON.stringify(result.errors));
+    // step 'group_enter' → its steps [group_has, can_access]
+    assert.deepEqual(arb.relationConfigs.get('can_deep').steps, ['member_of', 'group_has', 'can_access']);
+    arb.addNode('u:1', 'Employee'); arb.addNode('g:1', 'Group'); arb.addNode('g2:2', 'Group'); arb.addNode('doc:9', 'Doc');
+    arb.addRelation('u:1', 'member_of', 'g:1', { possibility: 1.0 });
+    arb.addRelation('g:1', 'group_has', 'g2:2', { possibility: 0.9 });
+    arb.addRelation('g2:2', 'can_access', 'doc:9', { possibility: 0.8 });
+    assert.equal(arb.check('u:1', 'can_deep', 'doc:9').possibility, 0.8);
+  });
+
+  it('expands a chain step whose direct evidence is itself composed', () => {
+    const { arb, result } = compile(`
+      ${DEFS}
+      evidence group_view(group: Group, doc: Doc) { can_view(group, doc) }
+      evidence group_read(group: Group, doc: Doc) { group_view(group, doc) }
+      evidence can_via(user: Employee, doc: Doc) { member_of(user, *g) { group_read(g, doc) } }
+    `);
+    assert.ok(result.success, JSON.stringify(result.errors));
+    assert.deepEqual(arb.relationConfigs.get('can_via').steps, ['member_of', 'can_view']);
+    arb.addNode('u:1', 'Employee'); arb.addNode('g:1', 'Group'); arb.addNode('doc:9', 'Doc');
+    arb.addRelation('u:1', 'member_of', 'g:1', { possibility: 1.0 });
+    arb.addRelation('g:1', 'can_view', 'doc:9', { possibility: 0.6 });
+    assert.equal(arb.check('u:1', 'can_via', 'doc:9').possibility, 0.6);
+  });
+
+  it('lowers a logical evidence FINAL step to a condition step', () => {
+    const { arb, result } = compile(`
+      ${DEFS}
+      evidence gated(group: Group, doc: Doc) { WHEN can_view(group, doc) UNLESS banned(group) }
+      evidence can_via(user: Employee, doc: Doc) { member_of(user, *g) { gated(g, doc) } }
+    `);
+    assert.ok(result.success, JSON.stringify(result.errors));
+    // final-step logical evidence → condition step (verified at the object)
+    const steps = arb.relationConfigs.get('can_via').steps;
+    assert.equal(steps[0], 'member_of');
+    assert.equal(steps[1].conditionStep, true);
+    assert.equal(steps[1].rule.type, 'logical');
+  });
+
+  it('rejects a mutual cycle through chain steps', () => {
+    const { result } = compile(`
+      ${DEFS}
+      evidence cyc_a(group: Group, doc: Doc) { group_has(group, *g) { cyc_b(g, doc) } }
+      evidence cyc_b(group: Group, doc: Doc) { cyc_a(group, doc) }
+    `);
+    assert.equal(result.success, false);
+    assert.ok(result.errors.some(e => /[Cc]yclic/.test(e)), JSON.stringify(result.errors));
+  });
+
+  it('rejects a self-reference through its own chain step', () => {
+    const { result } = compile(`
+      ${DEFS}
+      evidence cyc_c(group: Group, doc: Doc) { group_has(group, *g) { cyc_c(g, doc) } }
+    `);
+    assert.equal(result.success, false);
+    assert.ok(result.errors.some(e => /[Cc]yclic/.test(e)), JSON.stringify(result.errors));
+  });
+
+  it('re-derives transitive dependencies through expanded chain steps', () => {
+    const { arb, result } = compile(`
+      ${DEFS}
+      evidence group_read(group: Group, doc: Doc) { can_view(group, doc) }
+      evidence can_via(user: Employee, doc: Doc) { member_of(user, *g) { group_read(g, doc) } }
+    `);
+    assert.ok(result.success, JSON.stringify(result.errors));
+    // dependsOn reflects the expanded step, not the evidence reference
+    assert.deepEqual(arb.relationConfigs.get('can_via').dependsOn, ['member_of', 'can_view']);
+  });
+});

tests/DSLRuntime.test.js

@@ -20,9 +20,9 @@ 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 }
+  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)
@@ -164,8 +164,8 @@ describe('DSLRuntime', () => {
 
   it('derives transitive required facts through evidence composition', async () => {
     const dsl = `
-      definition Employee { id: string }
-      definition Doc { id: string }
+      definition Employee { id: string? }
+      definition Doc { id: string? }
       fact *owns(user: Employee, doc: Doc)
       fact *banned(user: Employee)
       evidence can_read(user: Employee, doc: Doc) { owns(user, doc) }
@@ -188,4 +188,21 @@ describe('DSLRuntime', () => {
     assert.equal(denied.possibility, 0);
     assert.equal(denied.reason, 'defeated_by_unless');
   });
+
+  it('derives transitive required facts through a condition-step chain', () => {
+    const dsl = `
+      definition Employee { id: string? }
+      definition Group { id: string? }
+      definition Doc { id: string? }
+      fact *member_of(user: Employee, group: Group)
+      fact *can_view(group: Group, doc: Doc)
+      fact *banned(group: Group)
+      evidence gated(group: Group, doc: Doc) { WHEN can_view(group, doc) UNLESS banned(group) }
+      evidence can_via(user: Employee, doc: Doc) { member_of(user, *g) { gated(g, doc) } }
+    `;
+    const rt = new DSLRuntime(new Arbiter()).compile(dsl, 'rt-cond');
+    // The condition step's facts (can_view, banned) reach through to the
+    // evidence's requirements, alongside the edge-traversal fact.
+    assert.deepEqual(rt.requiredFacts('can_via'), ['member_of', 'can_view', 'banned']);
+  });
 });

tests/DSLRuntimeCache.test.js

@@ -0,0 +1,203 @@
+/**
+ * tests/DSLRuntimeCache.test.js — provider-result caching with time expiry.
+ *
+ * Registered providers retrieve missing facts from a data store; caching the
+ * retrieval avoids hammering the store on repeated checks. TTL resolution:
+ * DSL-declared `BEHAVES { ttl <duration> }` on a fact > per-fact setFactTTL >
+ * policy default (30s). Per-check factProviders are cache-transparent (one-off
+ * observations: no cache read, no cache write). Registering a provider or
+ * mutating the graph invalidates the cache.
+ */
+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? }
+  definition Doc { id: string? }
+  fact *owns(user: Employee, doc: Doc)
+  evidence can_read(user: Employee, doc: Doc) { owns(user, doc) }
+`;
+
+function makeRuntime(options = {}) {
+  let t = 0;
+  const clock = () => t;
+  const rt = new DSLRuntime(new Arbiter(), { clock, ...options }).compile(BASE_DSL, 'rt-cache');
+  rt._test_advance = (ms) => { t += ms; };
+  return rt;
+}
+
+describe('DSLRuntime provider-result caching', () => {
+  it('reuses a registered provider result within the TTL', async () => {
+    const rt = makeRuntime();
+    rt.addNode('u:1', 'Employee', {});
+    rt.addNode('doc:9', 'Doc', {});
+    let calls = 0;
+    rt.registerFact('owns', async () => { calls++; return 0.9; });
+    await rt.check('u:1', 'can_read', 'doc:9');
+    await rt.check('u:1', 'can_read', 'doc:9');
+    assert.equal(calls, 1, 'provider should be invoked once within TTL');
+  });
+
+  it('re-invokes the provider after the TTL expires', async () => {
+    const rt = makeRuntime();
+    rt.setFactTTL('owns', 100);
+    rt.addNode('u:1', 'Employee', {});
+    rt.addNode('doc:9', 'Doc', {});
+    let calls = 0;
+    let value = 0.9;
+    rt.registerFact('owns', async () => { calls++; return value; });
+    const first = await rt.check('u:1', 'can_read', 'doc:9');
+    assert.equal(first.possibility, 0.9);
+    rt._test_advance(50);
+    await rt.check('u:1', 'can_read', 'doc:9'); // within TTL -> cached
+    assert.equal(calls, 1);
+    rt._test_advance(60); // past TTL (110 total)
+    value = 0.4;
+    const after = await rt.check('u:1', 'can_read', 'doc:9');
+    assert.equal(calls, 2);
+    assert.equal(after.possibility, 0.4);
+  });
+
+  it('per-check factProviders override the cache (fresh observation)', async () => {
+    const rt = makeRuntime();
+    rt.addNode('u:1', 'Employee', {});
+    rt.addNode('doc:9', 'Doc', {});
+    rt.registerFact('owns', async () => 0.9);
+    await rt.check('u:1', 'can_read', 'doc:9');
+    // Per-check override is cache-transparent: it must NOT be masked by the
+    // cached 0.9, and it must NOT overwrite the cached value.
+    const over = await rt.check('u:1', 'can_read', 'doc:9', {
+      factProviders: { owns: async () => 0.2 }
+    });
+    assert.equal(over.possibility, 0.2);
+    const next = await rt.check('u:1', 'can_read', 'doc:9');
+    assert.equal(next.possibility, 0.9, 'registered provider cache untouched by per-check override');
+  });
+
+  it('registerFact invalidates the cached result for that relation', async () => {
+    const rt = makeRuntime();
+    rt.addNode('u:1', 'Employee', {});
+    rt.addNode('doc:9', 'Doc', {});
+    rt.registerFact('owns', async () => 0.9);
+    await rt.check('u:1', 'can_read', 'doc:9');
+    rt.registerFact('owns', async () => 0.3); // re-register -> cache invalidated
+    const res = await rt.check('u:1', 'can_read', 'doc:9');
+    assert.equal(res.possibility, 0.3);
+  });
+
+  it('invalidates cached results on graph mutations', async () => {
+    const rt = makeRuntime();
+    rt.addNode('u:1', 'Employee', {});
+    rt.addNode('doc:9', 'Doc', {});
+    let calls = 0;
+    rt.registerFact('owns', async () => { calls++; return 0.9; });
+    await rt.check('u:1', 'can_read', 'doc:9');
+    assert.equal(calls, 1);
+    rt.addRelation('u:1', 'owns', 'doc:9', { possibility: 1.0 }); // mutation clears cache
+    const res = await rt.check('u:1', 'can_read', 'doc:9');
+    assert.equal(calls, 2, 'graph mutation should invalidate the provider cache');
+  });
+
+  it('invalidateProviderCache() clears all or per relation', async () => {
+    const dsl = `
+      definition Employee { id: string? }
+      definition Doc { id: string? }
+      fact *owns(user: Employee, doc: Doc)
+      fact *banned(user: Employee)
+      evidence can_read(user: Employee, doc: Doc) { owns(user, doc) }
+      evidence can_open(user: Employee, doc: Doc) { WHEN can_read(user, doc) UNLESS banned(user) }
+    `;
+    const rt = new DSLRuntime(new Arbiter()).compile(dsl, 'rt-cache2');
+    rt.addNode('u:1', 'Employee', {});
+    rt.addNode('doc:9', 'Doc', {});
+    let ownsCalls = 0, bannedCalls = 0;
+    rt.registerFact('owns', async () => { ownsCalls++; return 0.9; });
+    rt.registerFact('banned', async () => { bannedCalls++; return 0; });
+    await rt.check('u:1', 'can_open', 'doc:9');
+    assert.equal(ownsCalls, 1);
+    assert.equal(bannedCalls, 1);
+    // Invalidate a non-dependency relation: can_open's cache (owns+banned) survives.
+    rt.invalidateProviderCache('does_not_exist');
+    await rt.check('u:1', 'can_open', 'doc:9');
+    assert.equal(ownsCalls, 1);
+    assert.equal(bannedCalls, 1);
+    // Invalidate owns only: banned survives, owns re-fetched.
+    rt.invalidateProviderCache('owns');
+    await rt.check('u:1', 'can_open', 'doc:9');
+    assert.equal(ownsCalls, 2, 'owns cache cleared by per-relation invalidation');
+    assert.equal(bannedCalls, 1, 'banned cache survives per-relation invalidation');
+    // Clear all.
+    rt.invalidateProviderCache();
+    await rt.check('u:1', 'can_open', 'doc:9');
+    assert.equal(bannedCalls, 2, 'full invalidation clears every relation');
+  });
+
+  it('policy default TTL applies when no per-fact TTL is set', async () => {
+    const rt = makeRuntime({ policy: { providerCacheTTL: 50 } });
+    rt.addNode('u:1', 'Employee', {});
+    rt.addNode('doc:9', 'Doc', {});
+    let calls = 0;
+    rt.registerFact('owns', async () => { calls++; return 0.9; });
+    await rt.check('u:1', 'can_read', 'doc:9');
+    rt._test_advance(40);
+    await rt.check('u:1', 'can_read', 'doc:9');
+    assert.equal(calls, 1, 'within 50ms policy TTL -> cached');
+    rt._test_advance(20);
+    await rt.check('u:1', 'can_read', 'doc:9');
+    assert.equal(calls, 2, 'past 50ms policy TTL -> re-invoked');
+  });
+
+  it('uses the DSL-declared fact TTL (BEHAVES { ttl X })', async () => {
+    const dsl = `
+      definition Employee { id: string? }
+      definition Doc { id: string? }
+      fact *balance(user: Employee, amount: number) BEHAVES { ttl 1h }
+      evidence can_spend(user: Employee, doc: Doc) { balance(user, 1) }
+    `;
+    let t = 0;
+    const rt = new DSLRuntime(new Arbiter(), { clock: () => t }).compile(dsl, 'rt-dsl-ttl');
+    // The DSL declares a 1h TTL for the balance fact.
+    assert.equal(rt.relations.get('balance').ttlMs, 3600_000);
+    rt.addNode('u:1', 'Employee', {});
+    rt.addNode('doc:9', 'Doc', {});
+    let calls = 0;
+    rt.registerFact('balance', async () => { calls++; return { possibility: 1.0, value: 50 }; });
+    await rt.check('u:1', 'can_spend', 'doc:9');
+    assert.equal(calls, 1);
+    t += 60 * 60 * 1000 - 1; // just under 1h
+    await rt.check('u:1', 'can_spend', 'doc:9');
+    assert.equal(calls, 1, 'cached within DSL-declared 1h TTL');
+    t += 2;
+    await rt.check('u:1', 'can_spend', 'doc:9');
+    assert.equal(calls, 2, 're-invoked past the DSL-declared 1h TTL');
+  });
+
+  it('cacheProviderResults:false bypasses the cache per check', async () => {
+    const rt = makeRuntime();
+    rt.addNode('u:1', 'Employee', {});
+    rt.addNode('doc:9', 'Doc', {});
+    let calls = 0;
+    rt.registerFact('owns', async () => { calls++; return 0.9; });
+    await rt.check('u:1', 'can_read', 'doc:9');
+    assert.equal(calls, 1);
+    // Bypass forces a fresh retrieval without clearing the cache.
+    await rt.check('u:1', 'can_read', 'doc:9', { cacheProviderResults: false });
+    assert.equal(calls, 2);
+    // Cache still intact for the next default check.
+    await rt.check('u:1', 'can_read', 'doc:9');
+    assert.equal(calls, 2);
+  });
+
+  it('policy.cacheProviderResults:false disables caching globally', async () => {
+    const rt = makeRuntime({ policy: { cacheProviderResults: false } });
+    rt.addNode('u:1', 'Employee', {});
+    rt.addNode('doc:9', 'Doc', {});
+    let calls = 0;
+    rt.registerFact('owns', async () => { calls++; return 0.9; });
+    await rt.check('u:1', 'can_read', 'doc:9');
+    await rt.check('u:1', 'can_read', 'doc:9');
+    assert.equal(calls, 2, 'no caching when disabled globally');
+  });
+});

tests/DSLRuntimeExt.test.js

@@ -0,0 +1,168 @@
+/**
+ * tests/DSLRuntimeExt.test.js — extended DSLRuntime capabilities:
+ *   - schema introspection (getSchema)
+ *   - per-relation provider registration (registerFact/unregisterFact)
+ *   - provider merging (registered + per-check overrides)
+ *   - bounded fixed-point provider retrieval loop (edges satisfy other facts)
+ *   - require() throw-on-deny
+ *   - removal passthroughs and fact-relation check validation
+ *   - timestamp/duration field typing
+ */
+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 Doc { id: string? created: timestamp? }
+  fact *owns(user: Employee, doc: Doc)
+  fact *banned(user: Employee)
+  evidence can_read(user: Employee, doc: Doc) { owns(user, doc) }
+  evidence can_open(user: Employee, doc: Doc) { WHEN can_read(user, doc) UNLESS banned(user) }
+`;
+
+function makeRuntime() {
+  return new DSLRuntime(new Arbiter()).compile(BASE_DSL, 'rt-ext');
+}
+
+describe('DSLRuntime extended', () => {
+  it('exposes a serializable schema snapshot', () => {
+    const rt = makeRuntime();
+    const schema = rt.getSchema();
+    assert.ok(Array.isArray(schema.types));
+    const employee = schema.types.find(t => t.name === 'Employee');
+    assert.ok(employee);
+    assert.ok(employee.fields.some(f => f.name === 'level' && f.type === 'number'));
+    const owns = schema.facts.find(f => f.name === 'owns');
+    assert.equal(owns.injectable, true);
+    assert.equal(owns.params[1].type, 'Doc');
+    const can_open = schema.evidence.find(e => e.name === 'can_open');
+    assert.ok(can_open.dependsOn.includes('owns'));
+    assert.deepEqual(schema.providers, []);
+    assert.ok(rt.relationNames().includes('owns') && rt.relationNames().includes('can_read'));
+  });
+
+  it('registers, lists, and unregisters per-relation providers', () => {
+    const rt = makeRuntime();
+    rt.registerFact('owns', async () => 0.8);
+    assert.deepEqual(rt.registeredFacts(), ['owns']);
+    rt.registerFact('banned', async () => 0);
+    assert.deepEqual(rt.registeredFacts().sort(), ['banned', 'owns']);
+    rt.unregisterFact('banned');
+    assert.deepEqual(rt.registeredFacts(), ['owns']);
+    assert.throws(() => rt.registerFact('owns', 'not a function'), /must be a function/);
+  });
+
+  it('merges registered providers with per-check overrides', async () => {
+    const rt = makeRuntime();
+    rt.registerFact('owns', async () => 0.5);
+    rt.registerFact('banned', async () => 0);
+    rt.addNode('u:1', 'Employee', {});
+    rt.addNode('doc:9', 'Doc', {});
+    // registered owns (0.5) wins over nothing; per-check banned overrides
+    const res = await rt.check('u:1', 'can_open', 'doc:9', {
+      factProviders: { banned: async () => 0 }
+    });
+    assert.equal(res.possibility, 0.5);
+    assert.deepEqual(res.providedFacts.sort(), ['banned', 'owns']);
+  });
+
+  it('runs providers to a fixed point when edges satisfy other required facts', async () => {
+    // can_open needs owns (injectable). A registered owns provider returns an
+    // edge for a DIFFERENT injectable fact that can_open also requires via
+    // composition — here we add a transitive requirement to prove the loop.
+    const dsl = `
+      definition Employee { id: string? }
+      definition Doc { id: string? }
+      fact *owns(user: Employee, doc: Doc)
+      fact *granted(user: Employee, doc: Doc)
+      evidence base_read(user: Employee, doc: Doc) { owns(user, doc) }
+      evidence can_open(user: Employee, doc: Doc) { WHEN base_read(user, doc) UNLESS granted(user, doc) }
+    `;
+    const rt = new DSLRuntime(new Arbiter()).compile(dsl, 'rt-loop');
+    rt.addNode('u:1', 'Employee', {});
+    rt.addNode('doc:9', 'Doc', {});
+    let ownsCalls = 0;
+    let grantedCalls = 0;
+    rt.registerFact('owns', async () => {
+      ownsCalls++;
+      // First round the owns provider also supplies the granted edge (a
+      // fixed-point dependency: granted needs owns to have been retrieved).
+      return [
+        { src: 'u:1', relation: 'owns', dst: 'doc:9', possibility: 0.9 },
+        { src: 'u:1', relation: 'granted', dst: 'doc:9', possibility: 0 }
+      ];
+    });
+    rt.registerFact('granted', async () => { grantedCalls++; return 0; });
+    const res = await rt.check('u:1', 'can_open', 'doc:9', { maxProviderRounds: 3 });
+    assert.equal(res.possibility, 0.9);
+    // granted was satisfied by the owns provider's extra edge, so its own
+    // provider was never needed in a later round.
+    assert.equal(grantedCalls, 0);
+    assert.ok(ownsCalls >= 1);
+    assert.deepEqual(res.providedFacts, ['owns']);
+    assert.deepEqual(res.missingFacts, []);
+  });
+
+  it('require() throws on denial and returns the result on grant', async () => {
+    const rt = makeRuntime();
+    rt.addNode('u:1', 'Employee', {});
+    rt.addNode('doc:9', 'Doc', {});
+    rt.registerFact('owns', async () => 0.9);
+    const ok = await rt.require('u:1', 'can_read', 'doc:9');
+    assert.equal(ok.possibility, 0.9);
+    rt.registerFact('owns', async () => 0);
+    await assert.rejects(
+      () => rt.require('u:1', 'can_read', 'doc:9'),
+      (err) => err.result && err.result.possibility === 0 && /denied/.test(err.message)
+    );
+  });
+
+  it('passes through node/relation removal', () => {
+    const rt = makeRuntime();
+    rt.addNode('u:1', 'Employee', {});
+    rt.addNode('doc:9', 'Doc', {});
+    rt.addRelation('u:1', 'owns', 'doc:9', { possibility: 1.0 });
+    rt.removeRelation('u:1', 'owns', 'doc:9');
+    assert.equal(rt.arbiter.check('u:1', 'owns', 'doc:9').possibility, 0);
+    rt.removeNode('u:1');
+    assert.equal(rt.arbiter.nodeIdByKey.has('u:1'), false);
+  });
+
+  it('validates fact-relation check endpoints like evidence', async () => {
+    const rt = makeRuntime();
+    rt.addNode('u:1', 'Employee', {});
+    rt.addNode('doc:9', 'Doc', {});
+    // can_read is evidence; owns is a fact — checking a fact still validates.
+    await assert.rejects(() => rt.check('u:1', 'owns', 'u:1', {}), /expected 'Doc'/);
+  });
+
+  it('accepts timestamp field values and rejects mistyped ones', () => {
+    const rt = makeRuntime();
+    rt.addNode('doc:9', 'Doc', { created: 1720000000000 });
+    rt.updateNodeData('doc:9', { created: '2026-08-03T00:00:00Z' });
+    assert.throws(() => rt.addNode('doc:8', 'Doc', { created: {} }), /must be timestamp/);
+  });
+
+  it('direct FACT checks consult the registered provider', async () => {
+    const rt = makeRuntime();
+    rt.addNode('u:1', 'Employee', {});
+    rt.addNode('doc:9', 'Doc', {});
+    let calls = 0;
+    rt.registerFact('owns', async () => { calls++; return 0.9; });
+    // Checking the fact directly (not via an evidence) must retrieve it.
+    const res = await rt.check('u:1', 'owns', 'doc:9');
+    assert.equal(res.possibility, 0.9);
+    assert.equal(calls, 1);
+    assert.deepEqual(res.requiredFacts, ['owns']);
+    assert.deepEqual(res.providedFacts, ['owns']);
+    // Without a provider and without an edge, it reports the missing fact.
+    const rt2 = new DSLRuntime(new Arbiter()).compile(BASE_DSL, 'rt-fact-miss');
+    rt2.addNode('u:1', 'Employee', {});
+    rt2.addNode('doc:9', 'Doc', {});
+    const missed = await rt2.check('u:1', 'owns', 'doc:9');
+    assert.equal(missed.possibility, 0);
+    assert.deepEqual(missed.missingFacts, [{ relation: 'owns', reason: 'no_provider' }]);
+  });
+});

tests/DSLRuntimeTyping.test.js

@@ -0,0 +1,96 @@
+/**
+ * tests/DSLRuntimeTyping.test.js — duration seconds, required fields, and
+ * type validation of insertions / updates / provider retrievals.
+ *
+ * - Duration literals now accept s/m/h/d/w: `BEHAVES { ttl 30s }` is 30s.
+ * - Definition fields are REQUIRED by default (`field: type`); `field: type?`
+ *   marks a field optional. addNode enforces presence on insert.
+ * - Provider-returned edges are validated against the fact's declared typing:
+ *   a value-carrying fact must return { value, possibility } with a value of
+ *   the declared type, and possibilities must lie in [0, 1].
+ */
+import { describe, it } from 'node:test';
+import assert from 'node:assert/strict';
+import { Arbiter } from '@arbiter/core';
+import { DSLRuntime } from '../src/runtime/DSLRuntime.js';
+
+describe('DSLRuntime typing', () => {
+  it('accepts seconds/minutes/hours/days/weeks in duration literals', async () => {
+    const dsl = `
+      definition Employee { id: string? }
+      definition Doc { id: string? }
+      fact *a(user: Employee, amount: number) BEHAVES { ttl 30s }
+      fact *b(user: Employee, amount: number) BEHAVES { ttl 2m }
+      fact *c(user: Employee, amount: number) BEHAVES { ttl 1h }
+      fact *d(user: Employee, amount: number) BEHAVES { ttl 3d }
+      fact *e(user: Employee, amount: number) BEHAVES { ttl 1w }
+    `;
+    const rt = new DSLRuntime(new Arbiter()).compile(dsl, 'rt-units');
+    assert.equal(rt.relations.get('a').ttlMs, 30_000);
+    assert.equal(rt.relations.get('b').ttlMs, 120_000);
+    assert.equal(rt.relations.get('c').ttlMs, 3_600_000);
+    assert.equal(rt.relations.get('d').ttlMs, 259_200_000);
+    assert.equal(rt.relations.get('e').ttlMs, 604_800_000);
+  });
+
+  it('enforces required definition fields on node insert', () => {
+    const rt = new DSLRuntime(new Arbiter()).compile(`
+      definition Employee { id: string level: number active: boolean? }
+    `, 'rt-req');
+    // id and level are required (no `?`); active is optional.
+    assert.throws(() => rt.addNode('u:1', 'Employee', { level: 3 }), /missing required field 'Employee.id'/);
+    assert.throws(() => rt.addNode('u:2', 'Employee', { id: 'u:2' }), /missing required field 'Employee.level'/);
+    rt.addNode('u:3', 'Employee', { id: 'u:3', level: 5 }); // both required, no active -> ok
+    rt.addNode('u:4', 'Employee', { id: 'u:4', level: 5, active: true });
+  });
+
+  it('exposes requiredness in the schema snapshot', () => {
+    const rt = new DSLRuntime(new Arbiter()).compile(`
+      definition Employee { id: string level: number? }
+    `, 'rt-schema-req');
+    const employee = rt.getSchema().types.find(t => t.name === 'Employee');
+    assert.equal(employee.fields.find(f => f.name === 'id').required, true);
+    assert.equal(employee.fields.find(f => f.name === 'level').required, false);
+  });
+
+  it('validates a provider-returned value against the declared value type', async () => {
+    const rt = new DSLRuntime(new Arbiter()).compile(`
+      definition Employee { id: string? }
+      definition Doc { id: string? }
+      fact *balance(user: Employee, amount: number)
+      evidence can_spend(user: Employee, doc: Doc) { balance(user, 1) }
+    `, 'rt-valuetype');
+    rt.addNode('u:1', 'Employee', {});
+    rt.addNode('doc:9', 'Doc', {});
+    rt.registerFact('balance', async () => ({ possibility: 1.0, value: 'high' }));
+    await assert.rejects(() => rt.check('u:1', 'can_spend', 'doc:9'), /must be number/);
+  });
+
+  it('requires a value for a value-carrying fact (no bare-number shorthand)', async () => {
+    const rt = new DSLRuntime(new Arbiter()).compile(`
+      definition Employee { id: string? }
+      definition Doc { id: string? }
+      fact *balance(user: Employee, amount: number)
+      evidence can_spend(user: Employee, doc: Doc) { balance(user, 1) }
+    `, 'rt-valshape');
+    rt.addNode('u:1', 'Employee', {});
+    rt.addNode('doc:9', 'Doc', {});
+    rt.registerFact('balance', async () => 0.9);
+    await assert.rejects(() => rt.check('u:1', 'can_spend', 'doc:9'), /value-carrying fact/);
+    rt.registerFact('balance', async () => ({ possibility: 1.0 })); // missing value
+    await assert.rejects(() => rt.check('u:1', 'can_spend', 'doc:9'), /must supply a 'value'/);
+  });
+
+  it('rejects a provider-returned possibility outside [0, 1]', async () => {
+    const rt = new DSLRuntime(new Arbiter()).compile(`
+      definition Employee { id: string? }
+      definition Doc { id: string? }
+      fact *owns(user: Employee, doc: Doc)
+      evidence can_read(user: Employee, doc: Doc) { owns(user, doc) }
+    `, 'rt-poss');
+    rt.addNode('u:1', 'Employee', {});
+    rt.addNode('doc:9', 'Doc', {});
+    rt.registerFact('owns', async () => ({ possibility: 2.0 }));
+    await assert.rejects(() => rt.check('u:1', 'can_read', 'doc:9'), /invalid possibility/);
+  });
+});

tests/EvidenceTests.js

@@ -45,6 +45,7 @@ const DSL_SUPPORT = `
   fact isMember(user: any, group: any)
   fact isFriend(user: any, friend: any)
   fact similar(a: any, b: any)
+  fact reachable(user: any, doc: any)
   fact parentOf(user: any, parent: any)
   fact isEditable(doc: any)
   fact isPublic(doc: any)
@@ -159,7 +160,7 @@ describe('Evidence Rules', () => {
       {
         input: `evidence canRead(user: Employee, doc: Document) {
           isMember(user, *group) {
-            canRead(group, doc)
+            reachable(group, doc)
           }
         }`,
         description: 'Basic pattern matching with wildcard'
@@ -167,7 +168,7 @@ describe('Evidence Rules', () => {
       {
         input: `evidence canRead(user: Employee, doc: Document) {
           isMember(user, *group) {
-            canRead(group, doc)
+            reachable(group, doc)
           } limit 5
         }`,
         description: 'Pattern matching with limit'
@@ -175,7 +176,7 @@ describe('Evidence Rules', () => {
       {
         input: `evidence canRead(user: Employee, doc: Document) {
           similar(doc, *similar) |similarity| {
-            canRead(user, similar)
+            reachable(user, similar)
           } with similarity > 0.7
         }`,
         description: 'Pattern matching with binding and condition'
@@ -183,7 +184,7 @@ describe('Evidence Rules', () => {
       {
         input: `evidence canRead(user: Employee, doc: Document) {
           similar(doc, *similar) |similarity| {
-            canRead(user, similar)
+            reachable(user, similar)
           } limit 5 with similarity > 0.7
         }`,
         description: 'Pattern matching with binding, condition, and limit'
@@ -192,7 +193,7 @@ describe('Evidence Rules', () => {
         input: `evidence canRead(user: Employee, doc: Document) {
           isMember(user, *group) {
             isMember(group, *parentGroup) {
-              canRead(parentGroup, doc)
+              reachable(parentGroup, doc)
             } limit 2
           } limit 3
         }`,
@@ -202,7 +203,7 @@ describe('Evidence Rules', () => {
         input: `evidence canRead(user: Employee, doc: Document) {
           isFriend(user, *friend) {
             isMember(friend, *group) {
-              canRead(group, doc)
+              reachable(group, doc)
             } limit 1
           } limit 5
         }`,
@@ -291,15 +292,15 @@ describe('Evidence Rules', () => {
           owns(user, doc)
 
           isMember(user, *group) {
-            canRead(group, doc)
+            reachable(group, doc)
           } limit 5
 
           parentOf(user, *parent) {
-            canRead(parent, doc)
+            reachable(parent, doc)
           } limit 3
 
           similar(doc, *similar) |similarity| {
-            canRead(user, similar)
+            reachable(user, similar)
           } limit 5 with similarity > 0.7
 
           WHEN hasRole(user, 'admin') UNLESS isSuspended(user)
@@ -337,11 +338,11 @@ describe('Evidence Rules', () => {
           owns(user, doc)
 
           isMember(user, *group) {
-            canModify(group, doc)
+            reachable(group, doc)
           } limit 3
 
           similar(doc, *similar) |similarity| {
-            canModify(user, similar)
+            reachable(user, similar)
             isEditable(similar)
           } limit 2 with similarity > 0.8
 
@@ -385,7 +386,7 @@ describe('Evidence Rules', () => {
       {
         input: `evidence canRead(user: Employee, doc: Document) {
           isMember(user, *group) {
-            canRead(group, doc)
+            reachable(group, doc)
           } with
         }`,
         description: 'Incomplete with clause should fail'
@@ -393,7 +394,7 @@ describe('Evidence Rules', () => {
       {
         input: `evidence canRead(user: Employee, doc: Document) {
           isMember(user, *group) {
-            canRead(group, doc)
+            reachable(group, doc)
           } limit
         }`,
         description: 'Incomplete limit should fail'

tests/IntegrationTests.js

@@ -105,6 +105,7 @@ describe('Integration Tests', () => {
       fact hasAccess(user: Employee, resource: Resource, level: string) CACHE lazy
       fact isColleague(user: any, colleague: any) symmetrical CACHE lazy limit 50
       fact isParentOf(parent: Employee, child: Employee) transitive CACHE eager limit 3
+      fact reachable(user: any, doc: any) CACHE lazy
       fact hasClearance(user: Employee, level: string) CACHE eager
       fact parentOf(user: any, parent: any) CACHE eager
       fact similar(a: any, b: any) CACHE lazy
@@ -119,15 +120,15 @@ describe('Integration Tests', () => {
         owns(user, doc)
 
         isMember(user, *group) {
-          canRead(group, doc)
+          reachable(group, doc)
         } limit 5
 
         parentOf(user, *parent) {
-          canRead(parent, doc)
+          reachable(parent, doc)
         } limit 3
 
         similar(doc, *similar) |similarity| {
-          canRead(user, similar)
+          reachable(user, similar)
         } limit 5 with similarity > 0.7
 
         WHEN hasRole(user, 'admin') UNLESS isSuspended(user)
@@ -137,7 +138,7 @@ describe('Integration Tests', () => {
         owns(user, doc)
 
         isMember(user, *group) {
-          canWrite(group, doc)
+          reachable(group, doc)
         } limit 3
 
         WHEN hasRole(user, 'admin') UNLESS isSuspended(user)
@@ -330,6 +331,7 @@ describe('Integration Tests', () => {
 
       fact isMember(user: any, org: any) transitive CACHE lazy limit 5
       fact isParentOf(parent: Organization, child: Organization) transitive CACHE eager limit 3
+      fact reachable(user: any, doc: any) CACHE lazy
       fact hasRole(user: Employee, role: string) CACHE eager
       fact hasClearance(user: Employee, level: string) CACHE eager
       fact isSuspended(user: any) CACHE lazy
@@ -339,7 +341,7 @@ describe('Integration Tests', () => {
         isMember(user, org)
 
         isParentOf(org, *parentOrg) {
-          canAccessOrg(user, parentOrg)
+          reachable(user, parentOrg)
         } limit 3
 
         WHEN hasRole(user, 'admin') UNLESS isSuspended(user)
@@ -347,11 +349,11 @@ describe('Integration Tests', () => {
 
       evidence canAccessResource(user: Employee, resource: Resource) {
         isMember(user, *org) {
-          canAccessResource(org, resource)
+          reachable(org, resource)
         } limit 5
 
         parentOf(user, *parent) {
-          canAccessResource(parent, resource)
+          reachable(parent, resource)
         } limit 2
       }
     `;
@@ -379,6 +381,7 @@ describe('Integration Tests', () => {
       fact hasInterest(user: any, interest: string) CACHE lazy
       fact hasTag(doc: any, tag: string) CACHE lazy
       fact owns(user: any, doc: any) CACHE eager
+      fact reachable(user: any, doc: any) CACHE lazy
       fact similar(a: any, b: any) CACHE lazy
       fact isPublic(doc: any) CACHE eager
       fact hasInterests(user: any) CACHE lazy
@@ -390,12 +393,12 @@ describe('Integration Tests', () => {
         owns(user, doc)
 
         similar(doc, *similar) |similarity| {
-          canRead(user, similar)
+          reachable(user, similar)
           isPublic(similar)
         } limit 10 with similarity > 0.7
 
         isFriend(user, *friend) {
-          canRead(friend, doc)
+          reachable(friend, doc)
         } limit 5
 
         fusion majority {
@@ -406,7 +409,7 @@ describe('Integration Tests', () => {
 
       evidence canRecommend(user: Employee, doc: Document) {
         similar(user, *similarUser) |similarity| {
-          canRead(similarUser, doc)
+          reachable(similarUser, doc)
         } limit 20 with similarity > 0.8
 
         fusion average {
@@ -556,13 +559,14 @@ describe('Integration Tests', () => {
       fact isFriend(user: any, friend: any) symmetrical CACHE eager limit 50
       fact hasPermission(user: Employee, resource: Resource, action: string) CACHE eager
       fact owns(user: Employee, resource: Resource) CACHE eager
+  fact reachable(user: any, doc: any) CACHE lazy
 
       // Optimized evidence rules
       evidence canAccess(user: Employee, resource: Resource) {
         owns(user, resource)
 
         isMember(user, *group) {
-          canAccess(group, resource)
+          reachable(group, resource)
         } limit 3
 
         WHEN hasPermission(user, resource, 'read')
@@ -572,7 +576,7 @@ describe('Integration Tests', () => {
         owns(user, resource)
 
         isMember(user, *group) {
-          canModify(group, resource)
+          reachable(group, resource)
         } limit 2
 
         WHEN hasPermission(user, resource, 'write')

tests/Recursion.test.js

@@ -0,0 +1,136 @@
+/**
+ * tests/Recursion.test.js — bounded self-recursion (transitive closure).
+ *
+ * An evidence whose config contains a chain step referencing ITSELF is
+ * unrolled at compile time into a bounded transitive closure: a union of
+ * paths — base, hop+base, hop²+base, … — where `hop` is the recursive chain's
+ * steps before the self-reference and the depth N comes from the pattern's
+ * `limit N` (or the compiler's maxRecursionDepth default). The base (the
+ * evidence's non-recursive statements) is verified as a condition step at each
+ * path's terminal node.
+ *
+ * A pure recursion (no base case) cannot grant and is a compile-time error.
+ */
+import { describe, it } from 'node:test';
+import assert from 'node:assert/strict';
+import { Arbiter } from '@arbiter/core';
+import { DSLCompiler } from '../src/DSLCompiler.js';
+
+const BASE = `
+  definition Employee { id: string }
+  definition Doc { id: string }
+  fact can_access(user: Employee, doc: Doc)
+  fact reports_to(user: Employee, manager: Employee)
+`;
+
+const RECURSIVE = `
+  evidence can_access_via(user: Employee, doc: Doc) {
+    can_access(user, doc)
+    reports_to(user, *m) { can_access_via(m, doc) } limit 3
+  }
+`;
+
+function compile(dsl, name = 'rec') {
+  const arb = new Arbiter();
+  const result = new DSLCompiler(arb).compile(dsl, name);
+  return { arb, result };
+}
+
+describe('Bounded self-recursion', () => {
+  it('unrolls into a union of base + bounded hop chains', () => {
+    const { arb, result } = compile(BASE + RECURSIVE);
+    assert.ok(result.success, JSON.stringify(result.errors));
+    const cfg = arb.relationConfigs.get('can_access_via');
+    assert.equal(cfg.type, 'logical');
+    assert.ok(cfg.union, 'recursion should compile to a union of paths');
+    // base + 3 hops (limit 3)
+    assert.equal(cfg.union.rules.length, 4);
+  });
+
+  it('grants through the base case and through multi-hop chains', () => {
+    const { arb, result } = compile(BASE + RECURSIVE);
+    assert.ok(result.success);
+    arb.addNode('u:1', 'Employee'); arb.addNode('m:1', 'Employee'); arb.addNode('m2:1', 'Employee'); arb.addNode('doc:9', 'Doc');
+    // base
+    arb.addRelation('u:1', 'can_access', 'doc:9', { possibility: 1.0 });
+    assert.equal(arb.check('u:1', 'can_access_via', 'doc:9').possibility, 1.0);
+    // 1-hop: u -> m -> doc
+    arb.removeRelation('u:1', 'can_access', 'doc:9');
+    arb.addRelation('u:1', 'reports_to', 'm:1', { possibility: 1.0 });
+    arb.addRelation('m:1', 'can_access', 'doc:9', { possibility: 0.7 });
+    assert.equal(arb.check('u:1', 'can_access_via', 'doc:9').possibility, 0.7);
+    // 2-hop: u -> m -> m2 -> doc
+    arb.addRelation('m:1', 'reports_to', 'm2:1', { possibility: 1.0 });
+    arb.addRelation('m2:1', 'can_access', 'doc:9', { possibility: 0.5 });
+    // union takes the best path: max(0.7, 0.5) = 0.7
+    assert.equal(arb.check('u:1', 'can_access_via', 'doc:9').possibility, 0.7);
+    // 2-hop alone (remove the 1-hop can_access)
+    arb.removeRelation('m:1', 'can_access', 'doc:9');
+    assert.equal(arb.check('u:1', 'can_access_via', 'doc:9').possibility, 0.5);
+  });
+
+  it('enforces the recursion depth limit', () => {
+    const { arb, result } = compile(`
+      ${BASE}
+      evidence can_access_via(user: Employee, doc: Doc) {
+        can_access(user, doc)
+        reports_to(user, *m) { can_access_via(m, doc) } limit 2
+      }
+    `);
+    assert.ok(result.success);
+    arb.addNode('u:1', 'Employee'); arb.addNode('m:1', 'Employee'); arb.addNode('m2:1', 'Employee'); arb.addNode('m3:1', 'Employee'); arb.addNode('doc:9', 'Doc');
+    arb.addRelation('u:1', 'reports_to', 'm:1', { possibility: 1.0 });
+    arb.addRelation('m:1', 'reports_to', 'm2:1', { possibility: 1.0 });
+    arb.addRelation('m2:1', 'reports_to', 'm3:1', { possibility: 1.0 });
+    arb.addRelation('m2:1', 'can_access', 'doc:9', { possibility: 0.5 }); // 2 hops
+    arb.addRelation('m3:1', 'can_access', 'doc:9', { possibility: 0.9 }); // 3 hops
+    assert.equal(arb.check('u:1', 'can_access_via', 'doc:9').possibility, 0.5);
+    arb.removeRelation('m2:1', 'can_access', 'doc:9');
+    // only the 3-hop path remains — beyond the limit -> denied
+    assert.equal(arb.check('u:1', 'can_access_via', 'doc:9').possibility, 0);
+  });
+
+  it('uses the compiler maxRecursionDepth default when no limit is given', () => {
+    const dsl = `
+      ${BASE}
+      evidence can_access_via(user: Employee, doc: Doc) {
+        can_access(user, doc)
+        reports_to(user, *m) { can_access_via(m, doc) }
+      }
+    `;
+    const { arb, result } = compile(dsl);
+    assert.ok(result.success, JSON.stringify(result.errors));
+    // default depth 3 -> base + 3 hops
+    assert.equal(arb.relationConfigs.get('can_access_via').union.rules.length, 4);
+    // a deeper path (4 hops) is not granted
+    arb.addNode('u:1', 'Employee'); arb.addNode('m:1', 'Employee'); arb.addNode('m2:1', 'Employee'); arb.addNode('m3:1', 'Employee'); arb.addNode('m4:1', 'Employee'); arb.addNode('doc:9', 'Doc');
+    arb.addRelation('u:1', 'reports_to', 'm:1', { possibility: 1.0 });
+    arb.addRelation('m:1', 'reports_to', 'm2:1', { possibility: 1.0 });
+    arb.addRelation('m2:1', 'reports_to', 'm3:1', { possibility: 1.0 });
+    arb.addRelation('m3:1', 'reports_to', 'm4:1', { possibility: 1.0 });
+    arb.addRelation('m4:1', 'can_access', 'doc:9', { possibility: 1.0 });
+    assert.equal(arb.check('u:1', 'can_access_via', 'doc:9').possibility, 0, '4-hop path exceeds default depth');
+  });
+
+  it('rejects a pure recursion with no base case', () => {
+    const { result } = compile(`
+      ${BASE}
+      evidence can_access_via(user: Employee, doc: Doc) {
+        reports_to(user, *m) { can_access_via(m, doc) } limit 3
+      }
+    `);
+    assert.equal(result.success, false);
+    assert.ok(result.errors.some(e => /no base case/.test(e)), JSON.stringify(result.errors));
+  });
+
+  it('keeps mutual (non-self) cycles a compile error', () => {
+    const { result } = compile(`
+      ${BASE}
+      fact peer(user: Employee, other: Employee)
+      evidence a(user: Employee, doc: Doc) { peer(user, *p) { b(p, doc) } }
+      evidence b(user: Employee, doc: Doc) { peer(user, *p) { a(p, doc) } }
+    `);
+    assert.equal(result.success, false);
+    assert.ok(result.errors.some(e => /[Cc]yclic/.test(e)), JSON.stringify(result.errors));
+  });
+});

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

@@ -32,7 +32,12 @@ const FACTS = `
   fact can_access(group: Group, doc: Doc)
   fact owner(group: Group, doc: Doc)
   fact granted(user: Employee, doc: Doc)
+  fact group_perm(group: Group, doc: Doc)
+  fact group_banned(group: Group)
   fact banned(user: Employee)
+  fact peer(user: Employee, other: Employee)
+  fact trusted(other: Employee)
+  fact doc_read(user: Employee, doc: Doc)
   fact mfa(user: Employee)
 `;
 
@@ -116,6 +121,44 @@ function buildProgram(kind, ps) {
       oracle = pOwn;
       break;
     }
+    case 'chain_step_composition': {
+      // group_read (a direct evidence) used as a CHAIN STEP inside can_via:
+      // the step is expanded at compile time to the underlying can_view edge.
+      const [pm, pv] = ps;
+      evidence = `evidence group_read(group: Group, doc: Doc) { group_perm(group, doc) }
+                  evidence can_via(user: Employee, doc: Doc) { member_of(user, *g) { group_read(g, doc) } }`;
+      edges.push({ src: 'u:1', relation: 'member_of', dst: 'g:1', possibility: pm });
+      edges.push({ src: 'g:1', relation: 'group_perm', dst: 'doc:9', possibility: pv });
+      oracle = Math.min(pm, pv);
+      break;
+    }
+    case 'chain_condition_step': {
+      // gated (a defeasible evidence) as the FINAL chain step → a condition
+      // step: the engine verifies gated at (intermediate, object). The oracle
+      // is the chain's min combined with the condition's base*(1-defeat).
+      const [pm, pv, pb] = ps;
+      evidence = `evidence gated(group: Group, doc: Doc) { WHEN group_perm(group, doc) UNLESS group_banned(group) }
+                  evidence can_via(user: Employee, doc: Doc) { member_of(user, *g) { gated(g, doc) } }`;
+      edges.push({ src: 'u:1', relation: 'member_of', dst: 'g:1', possibility: pm });
+      edges.push({ src: 'g:1', relation: 'group_perm', dst: 'doc:9', possibility: pv });
+      edges.push({ src: 'g:1', relation: 'group_banned', dst: 'g:1', possibility: pb });
+      oracle = Math.min(pm, pv * (1 - pb));
+      break;
+    }
+    case 'chain_intermediate_condition': {
+      // peer_trusted (a defeasible evidence) as an INTERMEDIATE chain step:
+      // the engine expands it from the source (peer edges filtered by the
+      // trusted defeater) then continues to can_read. Oracle = min of the
+      // surviving peer leg and the read leg.
+      const [pp, pt, pr] = ps;
+      evidence = `evidence peer_trusted(user: Employee, other: Employee) { WHEN peer(user, other) UNLESS trusted(other) }
+                  evidence can_via(user: Employee, doc: Doc) { peer_trusted(user, *p) { doc_read(p, doc) } }`;
+      edges.push({ src: 'u:1', relation: 'peer', dst: 'p:1', possibility: pp });
+      edges.push({ src: 'p:1', relation: 'trusted', dst: 'p:1', possibility: pt });
+      edges.push({ src: 'p:1', relation: 'doc_read', dst: 'doc:9', possibility: pr });
+      oracle = Math.min(pp * (1 - pt), pr);
+      break;
+    }
     default:
       throw new Error(`unknown construct: ${kind}`);
   }
@@ -136,6 +179,10 @@ function runCheck({ kind, ps }) {
   arbiter.addNode('u:1', 'Employee');
   arbiter.addNode('g:1', 'Group');
   arbiter.addNode('doc:9', 'Doc');
+  for (const e of edges) {
+    arbiter.addNode(e.src, e.dst === 'doc:9' ? 'Doc' : 'Employee');
+    arbiter.addNode(e.dst, e.dst === 'doc:9' ? 'Doc' : 'Employee');
+  }
   const compiler = new DSLCompiler(arbiter);
   const compiled = compiler.compile(dsl, 'oracle');
   if (!compiled.success) {
@@ -151,7 +198,8 @@ function runCheck({ kind, ps }) {
 }
 
 const CONSTRUCTS = ['direct', 'chain', 'tuple_to_userset', 'fusion_min', 'fusion_max',
-  'when_unless', 'never_always', 'requires_when', 'composition'];
+  'when_unless', 'never_always', 'requires_when', 'composition', 'chain_step_composition',
+  'chain_condition_step', 'chain_intermediate_condition'];
 
 describe('DSL generative oracle parity (rigor)', () => {
   it('generated legal DSL compiles and every check matches the oracle', async () => {
@@ -162,7 +210,7 @@ describe('DSL generative oracle parity (rigor)', () => {
             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))
+            ps: rigor.gen.tuple(rigor.gen.oneOf(P), rigor.gen.oneOf(P), rigor.gen.oneOf(P))
           })
         ))
       ],
@@ -180,18 +228,23 @@ describe('DSL generative oracle parity (rigor)', () => {
   });
 
   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
+    // Anti-vacuity complement to the campaign: sweep the full P × 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];
+          for (const c of P) {
+          const ps = kind === 'direct' ? [a] : [a, b, c];
           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');
+          for (const e of edges) {
+            arbiter.addNode(e.src, e.dst === 'doc:9' ? 'Doc' : 'Employee');
+            arbiter.addNode(e.dst, e.dst === 'doc:9' ? 'Doc' : 'Employee');
+          }
           const compiled = new DSLCompiler(arbiter).compile(dsl, 'sweep');
           assert.ok(compiled.success, `${kind} compile failed: ${(compiled.errors || []).join('; ')}`);
           for (const e of edges) arbiter.addRelation(e.src, e.relation, e.dst, { possibility: e.possibility });
@@ -200,6 +253,7 @@ describe('DSL generative oracle parity (rigor)', () => {
             Math.abs(result.possibility - oracle) <= EPS,
             `${kind} ps=[${ps}] check=${result.possibility}(${result.reason}) vs oracle=${oracle}`
           );
+          }
         }
       }
     }