diff --git a/gitnexus-shared/src/scope-resolution/method-dispatch-index.ts b/gitnexus-shared/src/scope-resolution/method-dispatch-index.ts
index d09e8fa89..dcaa45055 100644
--- a/gitnexus-shared/src/scope-resolution/method-dispatch-index.ts
+++ b/gitnexus-shared/src/scope-resolution/method-dispatch-index.ts
@@ -40,11 +40,27 @@ export interface MethodDispatchIndex {
   readonly mroByOwnerDefId: ReadonlyMap<DefId, readonly DefId[]>;
   /** Interfaces / traits → classes that implement them. */
   readonly implsByInterfaceDefId: ReadonlyMap<DefId, readonly DefId[]>;
+  /**
+   * Optional parallel MRO view that EXCLUDES mixin-like augmentation
+   * (e.g., PHP traits). Populated only when the input supplies
+   * `computeExtendsOnlyMro`. Used by the super-branch dispatch in
+   * `receiver-bound-calls` so that `parent::method()` walks the
+   * inheritance chain only, not the trait-augmented one. Undefined for
+   * languages without mixin-like semantics — callers should fall back
+   * to `mroFor` when this is missing.
+   */
+  readonly extendsOnlyMroByOwnerDefId?: ReadonlyMap<DefId, readonly DefId[]>;
 
   /** `mroByOwnerDefId.get`, with an empty frozen array on miss. */
   mroFor(ownerDefId: DefId): readonly DefId[];
   /** `implsByInterfaceDefId.get`, with an empty frozen array on miss. */
   implementorsOf(interfaceDefId: DefId): readonly DefId[];
+  /**
+   * `extendsOnlyMroByOwnerDefId.get`, with an empty frozen array on miss.
+   * Undefined when `extendsOnlyMroByOwnerDefId` was not populated; callers
+   * should treat this as equivalent to `mroFor` for non-mixin languages.
+   */
+  readonly extendsOnlyMroFor?: (ownerDefId: DefId) => readonly DefId[];
 }
 
 export interface MethodDispatchInput {
@@ -81,12 +97,25 @@ export interface MethodDispatchInput {
    * write-wins policy and fires at most once per unique owner.
    */
   readonly implementsOf: (ownerDefId: DefId) => readonly DefId[];
+  /**
+   * Optional: return the EXTENDS-only ancestor chain for `ownerDefId`,
+   * excluding the owner itself AND any mixin-like augmentation (e.g.,
+   * PHP traits). Languages without mixin semantics leave this undefined
+   * and the index's `extendsOnlyMroByOwnerDefId` stays unpopulated.
+   *
+   * Same contract as `computeMro`: pure, deterministic, `[]` on no parents.
+   * Called at most once per unique owner (first-write-wins).
+   */
+  readonly computeExtendsOnlyMro?: (ownerDefId: DefId) => readonly DefId[];
 }
 
 // ─── Builder ────────────────────────────────────────────────────────────────
 
 export function buildMethodDispatchIndex(input: MethodDispatchInput): MethodDispatchIndex {
   const mroByOwnerDefId = new Map<DefId, readonly DefId[]>();
+  const extendsOnlyByOwnerDefId = input.computeExtendsOnlyMro
+    ? new Map<DefId, readonly DefId[]>()
+    : undefined;
   const implsBuilding = new Map<DefId, DefId[]>();
   const implsSeen = new Map<DefId, Set<DefId>>();
 
@@ -97,6 +126,14 @@ export function buildMethodDispatchIndex(input: MethodDispatchInput): MethodDisp
       const chain = input.computeMro(ownerId);
       mroByOwnerDefId.set(ownerId, Object.freeze(chain.slice()));
     }
+    if (
+      input.computeExtendsOnlyMro !== undefined &&
+      extendsOnlyByOwnerDefId !== undefined &&
+      !extendsOnlyByOwnerDefId.has(ownerId)
+    ) {
+      const extOnly = input.computeExtendsOnlyMro(ownerId);
+      extendsOnlyByOwnerDefId.set(ownerId, Object.freeze(extOnly.slice()));
+    }
 
     for (const ifaceId of input.implementsOf(ownerId)) {
       let seen = implsSeen.get(ifaceId);
@@ -121,7 +158,7 @@ export function buildMethodDispatchIndex(input: MethodDispatchInput): MethodDisp
     implsByInterfaceDefId.set(ifaceId, Object.freeze(owners.slice()));
   }
 
-  return wrapIndex(mroByOwnerDefId, implsByInterfaceDefId);
+  return wrapIndex(mroByOwnerDefId, implsByInterfaceDefId, extendsOnlyByOwnerDefId);
 }
 
 // ─── Internal ───────────────────────────────────────────────────────────────
@@ -131,8 +168,9 @@ const EMPTY: readonly DefId[] = Object.freeze([]);
 function wrapIndex(
   mroByOwnerDefId: Map<DefId, readonly DefId[]>,
   implsByInterfaceDefId: Map<DefId, readonly DefId[]>,
+  extendsOnlyMroByOwnerDefId: Map<DefId, readonly DefId[]> | undefined,
 ): MethodDispatchIndex {
-  return {
+  const base: MethodDispatchIndex = {
     mroByOwnerDefId,
     implsByInterfaceDefId,
     mroFor(ownerDefId: DefId): readonly DefId[] {
@@ -142,4 +180,14 @@ function wrapIndex(
       return implsByInterfaceDefId.get(interfaceDefId) ?? EMPTY;
     },
   };
+  if (extendsOnlyMroByOwnerDefId !== undefined) {
+    return {
+      ...base,
+      extendsOnlyMroByOwnerDefId,
+      extendsOnlyMroFor(ownerDefId: DefId): readonly DefId[] {
+        return extendsOnlyMroByOwnerDefId.get(ownerDefId) ?? EMPTY;
+      },
+    };
+  }
+  return base;
 }
diff --git a/gitnexus-shared/src/scope-resolution/registries/lookup-core.ts b/gitnexus-shared/src/scope-resolution/registries/lookup-core.ts
index a18ad4930..fff3e7adb 100644
--- a/gitnexus-shared/src/scope-resolution/registries/lookup-core.ts
+++ b/gitnexus-shared/src/scope-resolution/registries/lookup-core.ts
@@ -423,13 +423,30 @@ function applyArityFilter(
   }
 
   let anyCompatible = false;
+  let anyUnknown = false;
   for (const state of perCandidate.values()) {
     const verdict = arityFn(callsite, state.def);
     state.signals.arityVerdict = verdict;
     if (verdict === 'compatible') anyCompatible = true;
+    else if (verdict === 'unknown') anyUnknown = true;
   }
 
-  if (!anyCompatible) return;
+  // When ALL candidates are 'incompatible' (none compatible, none unknown),
+  // the call is genuinely arity-broken — drop every candidate so the
+  // registry returns no resolution. This matches the PHP variadic case
+  // f(int $req, ...$rest) called with zero args: every candidate definitively
+  // rejects, and emitting an edge to a definitively-rejected callable is
+  // a false positive. When some candidates are 'unknown' (missing metadata),
+  // keep the set so downstream evidence can break the tie — that's the
+  // original safety-fallback behavior.
+  if (!anyCompatible) {
+    if (!anyUnknown) {
+      for (const defId of perCandidate.keys()) {
+        perCandidate.delete(defId);
+      }
+    }
+    return;
+  }
 
   // Filter: when at least one compatible candidate exists, drop incompatibles.
   for (const [defId, state] of perCandidate) {
diff --git a/gitnexus/src/core/ingestion/languages/php/arity-metadata.ts b/gitnexus/src/core/ingestion/languages/php/arity-metadata.ts
index 9dc07b98c..6b80a057d 100644
--- a/gitnexus/src/core/ingestion/languages/php/arity-metadata.ts
+++ b/gitnexus/src/core/ingestion/languages/php/arity-metadata.ts
@@ -8,7 +8,10 @@
  *     `undefined`, which `phpArityCompatibility` then treats as
  *     "max unknown" — the candidate stays eligible at `argCount >= required`.
  *   - Defaulted parameters (`= expr`) contribute to `optionalCount`;
- *     `requiredParameterCount = total − optionalCount`.
+ *     `requiredParameterCount = total − optionalCount − (variadic ? 1 : 0)`.
+ *     The variadic slot itself accepts zero args so it is subtracted from
+ *     the required count — `f(int $a, ...$rest)` requires exactly 1 arg,
+ *     not 2, and `f(...$rest)` requires 0.
  *   - `property_promotion_parameter` (constructor-promoted) is counted
  *     the same as `simple_parameter` since both consume an argument slot.
  *   - `parameterTypes` collects declared type names; a literal `'...'`
@@ -46,7 +49,10 @@ export function computePhpArityMetadata(fnNode: SyntaxNode): PhpArityMetadata {
   // Variadic methods accept any arg count ≥ required — leave `parameterCount`
   // undefined so the registry treats max as unknown.
   const parameterCount = hasVariadic ? undefined : total;
-  const requiredParameterCount = hasVariadic ? undefined : total - optionalCount;
+  // The variadic slot itself accepts zero args; subtract it from the required
+  // count so PHP's ArgumentCountError-equivalent calls (too few args before
+  // the variadic) are correctly rejected by arity compatibility.
+  const requiredParameterCount = total - optionalCount - (hasVariadic ? 1 : 0);
 
   return {
     parameterCount,
diff --git a/gitnexus/src/core/ingestion/languages/php/namespace-siblings.ts b/gitnexus/src/core/ingestion/languages/php/namespace-siblings.ts
index edf06519a..6ebfbde2a 100644
--- a/gitnexus/src/core/ingestion/languages/php/namespace-siblings.ts
+++ b/gitnexus/src/core/ingestion/languages/php/namespace-siblings.ts
@@ -106,6 +106,24 @@ export interface PhpSiblingInputs {
   readonly treeCache?: { get(filePath: string): unknown };
 }
 
+/**
+ * Side-channel cache populated by `populatePhpNamespaceSiblings` so that
+ * later visibility-check hooks (e.g., `isCallableVisibleFromCaller`) can
+ * look up a file's PHP namespace without re-parsing. Cleared at the start
+ * of every populate run so stale entries don't leak across resolutions.
+ */
+const namespaceByFilePath = new Map<string, string>();
+
+/**
+ * Read the cached PHP namespace for a given filePath. Returns `''` (global)
+ * when the file has no namespace_definition or hasn't been processed yet.
+ * Callers should only consult this AFTER `populatePhpNamespaceSiblings` has
+ * run for the current resolution.
+ */
+export function getPhpNamespaceForFile(filePath: string): string {
+  return namespaceByFilePath.get(filePath) ?? '';
+}
+
 /**
  * Inject same-namespace class defs and return-type bindings into each
  * PHP file's Module scope's `bindingAugmentations`. This makes classes
@@ -120,13 +138,17 @@ export function populatePhpNamespaceSiblings(
   indexes: ScopeResolutionIndexes,
   inputs: PhpSiblingInputs,
 ): void {
-  // Step 1: extract namespace structure for each file.
+  // Step 1: extract namespace structure for each file. Also seed the
+  // side-channel cache used by visibility-check hooks downstream.
+  namespaceByFilePath.clear();
   const structureByFile = new Map<string, PhpFileStructure>();
   for (const parsed of parsedFiles) {
     const content = inputs.fileContents.get(parsed.filePath);
     if (content === undefined) continue;
     const cachedTree = inputs.treeCache?.get(parsed.filePath);
-    structureByFile.set(parsed.filePath, extractPhpFileStructure(content, cachedTree));
+    const struct = extractPhpFileStructure(content, cachedTree);
+    structureByFile.set(parsed.filePath, struct);
+    namespaceByFilePath.set(parsed.filePath, struct.namespace);
   }
 
   // Step 2: group class-like defs and module scopes by namespace.
diff --git a/gitnexus/src/core/ingestion/languages/php/scope-resolver.ts b/gitnexus/src/core/ingestion/languages/php/scope-resolver.ts
index b0c2a666e..fd053506a 100644
--- a/gitnexus/src/core/ingestion/languages/php/scope-resolver.ts
+++ b/gitnexus/src/core/ingestion/languages/php/scope-resolver.ts
@@ -33,12 +33,14 @@ import {
   resolveCallerGraphId,
   resolveDefGraphId,
 } from '../../scope-resolution/graph-bridge/ids.js';
+import { narrowOverloadCandidates } from '../../scope-resolution/passes/overload-narrowing.js';
 import type { SemanticModel } from '../../model/semantic-model.js';
 import type { ScopeResolutionIndexes } from '../../model/scope-resolution-indexes.js';
+import type { SymbolDefinition } from 'gitnexus-shared';
 import { phpProvider } from '../php.js';
 import { phpArityCompatibility, phpMergeBindings } from './index.js';
 import { resolvePhpImportTargetInternal, loadPhpComposerConfig } from './import-target.js';
-import { populatePhpNamespaceSiblings } from './namespace-siblings.js';
+import { populatePhpNamespaceSiblings, getPhpNamespaceForFile } from './namespace-siblings.js';
 
 /**
  * PHP MRO builder — extends the generic EXTENDS-only MRO with trait-use
@@ -58,6 +60,72 @@ import { populatePhpNamespaceSiblings } from './namespace-siblings.js';
  * a trait method shadows the parent-class method but is overridden by the
  * using class's own methods).
  */
+/**
+ * PHP free-call visibility check for `pickUniqueGlobalCallable`. Returns
+ * true when the candidate function is reachable from the caller's PHP
+ * namespace context, false when the cross-namespace bridge would be a
+ * false positive (e.g., `\App\Utils\format` is not visible from `\App`
+ * without an explicit `use function App\Utils\format;`).
+ *
+ * Rules (PHP semantics):
+ *   1. Same-namespace candidates are always visible.
+ *   2. Global-namespace candidates (no namespace prefix) are visible from
+ *      every caller — PHP's global fallback for functions/constants.
+ *   3. Candidates in a different namespace are visible only when the
+ *      caller has a `use function` import that matches the candidate's
+ *      fully-qualified name.
+ */
+function phpIsCallableVisibleFromCaller(ctx: {
+  callerParsed: ParsedFile;
+  candidate: SymbolDefinition;
+}): boolean {
+  const { callerParsed, candidate } = ctx;
+  const callerNs = getPhpNamespaceForFile(callerParsed.filePath);
+  const candNs = getPhpNamespaceForFile(candidate.filePath);
+
+  // Global-namespace candidate: PHP falls back to global for functions
+  // and constants when the local namespace doesn't define them.
+  if (candNs === '') return true;
+
+  // Same-namespace: caller can see the candidate without an explicit use.
+  if (candNs === callerNs) return true;
+
+  // Cross-namespace: require an explicit `use function` import in the
+  // caller's parsedImports that matches the candidate's fully-qualified
+  // name. interpret.ts maps `use function Foo\bar` to a named import with
+  // localName = 'bar' and targetRaw = 'Foo\\bar'.
+  const candQualified =
+    candidate.qualifiedName === undefined
+      ? ''
+      : candNs !== '' && !candidate.qualifiedName.includes('\\')
+        ? `${candNs}\\${candidate.qualifiedName}`
+        : candidate.qualifiedName;
+  if (candQualified === '') return false;
+  return callerParsed.parsedImports.some(
+    (imp) =>
+      imp.kind === 'named' &&
+      imp.targetRaw.replace(/^\\+/, '') === candQualified.replace(/^\\+/, ''),
+  );
+}
+
+/**
+ * Compute the EXTENDS-only ancestor chain for every class — no trait
+ * augmentation. PHP semantics: `parent::method()` walks this view so
+ * that `parent::` resolves to the parent class's method, even when a
+ * composed trait shadows the same name.
+ *
+ * Returns the same shape as `buildPhpMro` so callers can swap views
+ * without changing dispatch logic. Just `buildMro` + `defaultLinearize`
+ * — no trait IMPLEMENTS edge walk.
+ */
+function buildPhpExtendsOnlyMro(
+  graph: KnowledgeGraph,
+  parsedFiles: readonly ParsedFile[],
+  nodeLookup: GraphNodeLookup,
+): Map<string, string[]> {
+  return buildMro(graph, parsedFiles, nodeLookup, defaultLinearize);
+}
+
 function buildPhpMro(
   graph: KnowledgeGraph,
   parsedFiles: readonly ParsedFile[],
@@ -104,34 +172,25 @@ function buildPhpMro(
   }
 
   // Step 4: augment every class's MRO by prepending the traits used by
-  // any class in its ancestor chain (transitively). PHP semantics:
-  // a trait used by a parent class is also visible on the child.
+  // any class in its ancestor chain (transitively closed). PHP semantics:
+  // a trait used by a parent class is also visible on the child, and a
+  // trait-using-trait chain is flattened to a single ancestor set.
   //
   // For each class, walk its (already-computed) EXTENDS-based MRO and
-  // collect all transitively-used traits. Prepend them before the
-  // EXTENDS ancestors so the method dispatch index finds trait methods
-  // before checking the parent class hierarchy.
+  // collect all transitively-used traits via BFS — `trait A { use B; }
+  // trait B { use C; } class X { use A; }` must include C in X's MRO.
+  // Prepend them before the EXTENDS ancestors so the method dispatch
+  // index finds trait methods before falling back to the parent class
+  // hierarchy.
   for (const [classDefId, extendsMro] of mro) {
-    const allTraits: string[] = [];
-    const seen = new Set<string>();
-
-    // Collect traits from this class itself and from each ancestor.
     const ancestorChain = [classDefId, ...extendsMro];
+    const seeds: string[] = [];
     for (const ancestorId of ancestorChain) {
       for (const traitId of directTraitUse.get(ancestorId) ?? []) {
-        if (!seen.has(traitId)) {
-          seen.add(traitId);
-          allTraits.push(traitId);
-          // Traits can use other traits — include transitively.
-          for (const transitiveTrait of directTraitUse.get(traitId) ?? []) {
-            if (!seen.has(transitiveTrait)) {
-              seen.add(transitiveTrait);
-              allTraits.push(transitiveTrait);
-            }
-          }
-        }
+        seeds.push(traitId);
       }
     }
+    const allTraits = collectTransitiveTraits(seeds, directTraitUse);
 
     if (allTraits.length > 0) {
       // Prepend traits before EXTENDS ancestors: own class's traits first,
@@ -146,20 +205,7 @@ function buildPhpMro(
   for (const [classDefId, traits] of directTraitUse) {
     if (!mro.has(classDefId) && !traitDefIds.has(classDefId)) {
       // Class with no EXTENDS but with trait-use — add to MRO map.
-      const allTraits: string[] = [];
-      const seen = new Set<string>();
-      for (const traitId of traits) {
-        if (!seen.has(traitId)) {
-          seen.add(traitId);
-          allTraits.push(traitId);
-          for (const transitiveTrait of directTraitUse.get(traitId) ?? []) {
-            if (!seen.has(transitiveTrait)) {
-              seen.add(transitiveTrait);
-              allTraits.push(transitiveTrait);
-            }
-          }
-        }
-      }
+      const allTraits = collectTransitiveTraits([...traits], directTraitUse);
       mro.set(classDefId, allTraits);
     }
   }
@@ -167,6 +213,32 @@ function buildPhpMro(
   return mro;
 }
 
+/**
+ * Collect the transitive closure of traits reachable from the seed set.
+ * BFS over `directTraitUse` until fixpoint. The `seen` set guards against
+ * cycles (invalid PHP but defensively handled) and prevents duplicate
+ * entries when multiple seeds converge on the same trait. Insertion order
+ * is preserved — first-seen wins for MRO ordering.
+ */
+function collectTransitiveTraits(
+  seeds: readonly string[],
+  directTraitUse: ReadonlyMap<string, readonly string[]>,
+): string[] {
+  const out: string[] = [];
+  const seen = new Set<string>();
+  const queue: string[] = [...seeds];
+  while (queue.length > 0) {
+    const t = queue.shift()!;
+    if (seen.has(t)) continue;
+    seen.add(t);
+    out.push(t);
+    for (const next of directTraitUse.get(t) ?? []) {
+      if (!seen.has(next)) queue.push(next);
+    }
+  }
+  return out;
+}
+
 /**
  * Emit CALLS edges for PHP member-call sites whose receiver has no type
  * binding (e.g. `mixed`-typed parameters, untyped variables).
@@ -222,6 +294,15 @@ function phpEmitUnresolvedReceiverEdges(
       const fnDef = candidates[0];
       if (fnDef === undefined) continue;
 
+      // Apply arity narrowing — a unique method name match is not enough
+      // when arity says the call is definitively incompatible (e.g., PHP
+      // f(int $req, ...$rest) called with zero args). This prevents the
+      // fallback from emitting edges that the receiver-bound pass already
+      // rejected for arity reasons.
+      if (narrowOverloadCandidates([fnDef], site.arity, site.argumentTypes).length === 0) {
+        continue;
+      }
+
       const callerGraphId = resolveCallerGraphId(site.inScope, scopes, nodeLookup);
       if (callerGraphId === undefined) continue;
       const tgtGraphId = resolveDefGraphId(fnDef.filePath, fnDef, nodeLookup);
@@ -265,6 +346,19 @@ const phpScopeResolver: ScopeResolver = {
 
   buildMro: (graph, parsedFiles, nodeLookup) => buildPhpMro(graph, parsedFiles, nodeLookup),
 
+  // PHP-specific: parent::method() must walk inheritance only, skipping
+  // composed traits. See buildPhpExtendsOnlyMro and the super-branch use
+  // in `passes/receiver-bound-calls.ts`.
+  buildExtendsOnlyMro: (graph, parsedFiles, nodeLookup) =>
+    buildPhpExtendsOnlyMro(graph, parsedFiles, nodeLookup),
+
+  // PHP free-call visibility: cross-namespace candidates are blocked
+  // unless explicitly `use function`-imported by the caller. Prevents
+  // false-positive CALLS edges between unrelated namespaces sharing a
+  // function name. Same-namespace and global-namespace candidates pass
+  // unchanged.
+  isCallableVisibleFromCaller: phpIsCallableVisibleFromCaller,
+
   populateOwners: (parsed: ParsedFile) => populateClassOwnedMembers(parsed),
 
   // PHP same-namespace cross-file visibility — classes in the same
diff --git a/gitnexus/src/core/ingestion/scope-resolution/contract/scope-resolver.ts b/gitnexus/src/core/ingestion/scope-resolution/contract/scope-resolver.ts
index de3bfbddf..99e7145ae 100644
--- a/gitnexus/src/core/ingestion/scope-resolution/contract/scope-resolver.ts
+++ b/gitnexus/src/core/ingestion/scope-resolution/contract/scope-resolver.ts
@@ -386,6 +386,26 @@ export interface ScopeResolver {
     nodeLookup: GraphNodeLookup,
   ): Map<string /* DefId */, string[] /* ancestor DefIds */>;
 
+  /**
+   * Optional parallel MRO that EXCLUDES mixin-like augmentation (e.g., PHP
+   * traits). Returns the inheritance-only ancestor chain — the same kind
+   * of map as `buildMro` but built only from inheritance edges (EXTENDS).
+   *
+   * Used by the shared super-branch dispatch in `receiver-bound-calls`
+   * so that `parent::method()` walks the inheritance chain only, not the
+   * trait-augmented one. PHP semantics: `parent::` explicitly bypasses
+   * traits, even when a composed trait shadows a same-named parent method.
+   *
+   * Languages without mixin-like semantics leave this undefined — callers
+   * fall back to `buildMro`/`mroFor`, which for those languages is already
+   * the inheritance chain.
+   */
+  readonly buildExtendsOnlyMro?: (
+    graph: KnowledgeGraph,
+    parsedFiles: readonly ParsedFile[],
+    nodeLookup: GraphNodeLookup,
+  ) => Map<string /* DefId */, string[] /* ancestor DefIds */>;
+
   /**
    * Mutate `parsed.localDefs[i].ownerId` to point at the structural
    * owner. Python's rule: methods (Function defs whose parent scope
@@ -484,6 +504,26 @@ export interface ScopeResolver {
    */
   readonly isFileLocalDef?: (def: SymbolDefinition) => boolean;
 
+  /**
+   * Optional predicate to gate free-call fallback emission by caller-side
+   * visibility. When provided, `pickUniqueGlobalCallable` rejects candidates
+   * the caller cannot legally reach — e.g., a PHP function in a different
+   * namespace with no `use function` import, which PHP runtime would treat
+   * as `Call to undefined function`. Returning `false` blocks the candidate;
+   * returning `true` allows it; undefined-default keeps current behavior
+   * (no visibility filtering, equivalent to "all candidates visible").
+   *
+   * The hook receives the caller's `ParsedFile` (so it can consult
+   * `parsedImports`, `moduleScope`, etc.) and the candidate `SymbolDefinition`.
+   * The predicate must be pure: same inputs → same answer.
+   *
+   * Languages without namespace-scoped function resolution leave this undefined.
+   */
+  readonly isCallableVisibleFromCaller?: (ctx: {
+    readonly callerParsed: ParsedFile;
+    readonly candidate: SymbolDefinition;
+  }) => boolean;
+
   /**
    * Optional post-finalize hook to inject cross-file bindings that
    * aren't modeled via explicit imports. Runs after
diff --git a/gitnexus/src/core/ingestion/scope-resolution/graph-bridge/method-dispatch.ts b/gitnexus/src/core/ingestion/scope-resolution/graph-bridge/method-dispatch.ts
index 164147ac6..419ab478f 100644
--- a/gitnexus/src/core/ingestion/scope-resolution/graph-bridge/method-dispatch.ts
+++ b/gitnexus/src/core/ingestion/scope-resolution/graph-bridge/method-dispatch.ts
@@ -22,8 +22,9 @@ const EMPTY_DEFS: readonly string[] = Object.freeze([]);
 
 export function buildPopulatedMethodDispatch(
   mroByDefId: ReadonlyMap<string, readonly string[]>,
+  extendsOnlyMroByDefId?: ReadonlyMap<string, readonly string[]>,
 ): MethodDispatchIndex {
-  return {
+  const base: MethodDispatchIndex = {
     mroByOwnerDefId: mroByDefId,
     implsByInterfaceDefId: new Map(),
     mroFor(ownerDefId) {
@@ -33,4 +34,14 @@ export function buildPopulatedMethodDispatch(
       return EMPTY_DEFS;
     },
   };
+  if (extendsOnlyMroByDefId !== undefined) {
+    return {
+      ...base,
+      extendsOnlyMroByOwnerDefId: extendsOnlyMroByDefId,
+      extendsOnlyMroFor(ownerDefId) {
+        return extendsOnlyMroByDefId.get(ownerDefId) ?? EMPTY_DEFS;
+      },
+    };
+  }
+  return base;
 }
diff --git a/gitnexus/src/core/ingestion/scope-resolution/passes/free-call-fallback.ts b/gitnexus/src/core/ingestion/scope-resolution/passes/free-call-fallback.ts
index 350eabc3c..401b3fe1c 100644
--- a/gitnexus/src/core/ingestion/scope-resolution/passes/free-call-fallback.ts
+++ b/gitnexus/src/core/ingestion/scope-resolution/passes/free-call-fallback.ts
@@ -39,6 +39,10 @@ export function emitFreeCallFallback(
   options: {
     readonly allowGlobalFallback?: boolean;
     readonly isFileLocalDef?: (def: SymbolDefinition) => boolean;
+    readonly isCallableVisibleFromCaller?: (ctx: {
+      readonly callerParsed: ParsedFile;
+      readonly candidate: SymbolDefinition;
+    }) => boolean;
   } = {},
 ): number {
   let emitted = 0;
@@ -83,6 +87,10 @@ export function emitFreeCallFallback(
           parsed.filePath,
           options.isFileLocalDef,
           site.arity,
+          options.isCallableVisibleFromCaller !== undefined
+            ? (candidate) =>
+                options.isCallableVisibleFromCaller!({ callerParsed: parsed, candidate })
+            : undefined,
         );
       }
       if (fnDef === undefined) continue;
@@ -120,6 +128,7 @@ function pickUniqueGlobalCallable(
   callerFilePath: string,
   isFileLocalDef?: (def: SymbolDefinition) => boolean,
   callArity?: number,
+  isCallerVisible?: (candidate: SymbolDefinition) => boolean,
 ): SymbolDefinition | undefined {
   const scopeDefs: SymbolDefinition[] = [];
   const scopeSeen = new Set<string>();
@@ -132,6 +141,13 @@ function pickUniqueGlobalCallable(
     if (isFileLocalDef !== undefined && def.filePath !== callerFilePath && isFileLocalDef(def)) {
       continue;
     }
+    // Caller-side visibility filter (e.g., PHP namespace + use-function
+    // import gating). When defined, blocks candidates the caller cannot
+    // legally reach. Languages without namespace-scoped function resolution
+    // leave this undefined → no filtering.
+    if (isCallerVisible !== undefined && !isCallerVisible(def)) {
+      continue;
+    }
     const key = logicalCallableKey(def);
     if (scopeSeen.has(key)) continue;
     scopeSeen.add(key);
@@ -158,6 +174,10 @@ function pickUniqueGlobalCallable(
       if (isFileLocalDef !== undefined && def.filePath !== callerFilePath && isFileLocalDef(def)) {
         continue;
       }
+      // Same caller-visibility filter applied to the model-side pool.
+      if (isCallerVisible !== undefined && !isCallerVisible(def)) {
+        continue;
+      }
       const key = logicalCallableKey(def);
       if (seen.has(key)) continue;
       seen.add(key);
diff --git a/gitnexus/src/core/ingestion/scope-resolution/passes/overload-narrowing.ts b/gitnexus/src/core/ingestion/scope-resolution/passes/overload-narrowing.ts
index 922afb36c..ae448e326 100644
--- a/gitnexus/src/core/ingestion/scope-resolution/passes/overload-narrowing.ts
+++ b/gitnexus/src/core/ingestion/scope-resolution/passes/overload-narrowing.ts
@@ -13,9 +13,13 @@
  *   2. Exact-required-match wins over variadic. Variadic is detected
  *      via a `parameterTypes` entry equal to `'params'` or starting
  *      with `'params '` (C# `params` / variadic marker).
- *   3. If the arity filter empties the set, fall back to the full
- *      overload list rather than returning nothing — the caller still
- *      needs a best-effort candidate.
+ *   3. If the arity filter empties the set AND any candidate had
+ *      unknown bounds (both `parameterCount` and `requiredParameterCount`
+ *      undefined), fall back to the full overload list — the empty
+ *      result may be due to missing metadata rather than a real mismatch.
+ *      If EVERY rejected candidate had definite arity bounds, trust the
+ *      filter and return empty — the call is genuinely arity-incompatible
+ *      (e.g., PHP `f(int $req, ...$rest)` called with zero args).
  *   4. If `argTypes` is present, filter further by per-slot type
  *      equality. An empty string in `argTypes[i]` means "unknown" and
  *      counts as a match. Mismatches disqualify. A non-empty typed
@@ -48,8 +52,16 @@ export function narrowOverloadCandidates(
           return true;
         });
 
+  // When the arity filter empties the set, only fall back to the full
+  // overload list if some candidate had unknown bounds — otherwise the
+  // empty result is authoritative (every candidate definitively failed
+  // arity, e.g., PHP variadic with required-prefix called with too few
+  // args).
+  const anyUnknownBounds = overloads.some(
+    (d) => d.parameterCount === undefined && d.requiredParameterCount === undefined,
+  );
   const candidates: readonly SymbolDefinition[] =
-    arityMatches.length > 0 ? arityMatches : overloads;
+    arityMatches.length > 0 ? arityMatches : anyUnknownBounds ? overloads : [];
 
   if (argTypes !== undefined && argTypes.length > 0) {
     const typed = candidates.filter((d) => {
diff --git a/gitnexus/src/core/ingestion/scope-resolution/passes/receiver-bound-calls.ts b/gitnexus/src/core/ingestion/scope-resolution/passes/receiver-bound-calls.ts
index 925151b6c..283f93b51 100644
--- a/gitnexus/src/core/ingestion/scope-resolution/passes/receiver-bound-calls.ts
+++ b/gitnexus/src/core/ingestion/scope-resolution/passes/receiver-bound-calls.ts
@@ -165,7 +165,16 @@ export function emitReceiverBoundCalls(
       if (provider.isSuperReceiver(receiverName)) {
         const enclosingClass = findEnclosingClassDef(site.inScope, scopes);
         if (enclosingClass !== undefined) {
-          const ancestors = scopes.methodDispatch.mroFor(enclosingClass.nodeId);
+          // For super-receiver dispatch (`parent::`, `base.`, `super()`),
+          // walk the inheritance-only ancestor chain when the language
+          // exposes it. PHP's `parent::` semantically bypasses composed
+          // traits; other languages without mixin augmentation have no
+          // `extendsOnlyMroFor` and fall back to `mroFor`.
+          const extendsOnly = scopes.methodDispatch.extendsOnlyMroFor;
+          const ancestors =
+            extendsOnly !== undefined
+              ? extendsOnly(enclosingClass.nodeId)
+              : scopes.methodDispatch.mroFor(enclosingClass.nodeId);
           let memberDef: SymbolDefinition | undefined;
           for (const ownerId of ancestors) {
             memberDef = findOwnedMember(ownerId, memberName, model);
@@ -283,7 +292,19 @@ export function emitReceiverBoundCalls(
         let memberDef: SymbolDefinition | undefined;
         for (const ownerId of chain) {
           memberDef = findOwnedMember(ownerId, memberName, model);
-          if (memberDef !== undefined) break;
+          if (memberDef !== undefined) {
+            // Reject when arity is definitively incompatible (e.g., PHP
+            // f(int $req, ...$rest) called with zero args). Falls through
+            // to the next owner in the chain — a subclass may shadow with
+            // a different arity.
+            if (
+              narrowOverloadCandidates([memberDef], site.arity, site.argumentTypes).length === 0
+            ) {
+              memberDef = undefined;
+              continue;
+            }
+            break;
+          }
         }
         if (memberDef !== undefined) {
           const reason =
diff --git a/gitnexus/src/core/ingestion/scope-resolution/pipeline/run.ts b/gitnexus/src/core/ingestion/scope-resolution/pipeline/run.ts
index 933fa43d9..637624232 100644
--- a/gitnexus/src/core/ingestion/scope-resolution/pipeline/run.ts
+++ b/gitnexus/src/core/ingestion/scope-resolution/pipeline/run.ts
@@ -153,6 +153,7 @@ export function runScopeResolution(
   const allFilePaths = new Set(parsedFiles.map((f) => f.filePath));
   const nodeLookup = buildGraphNodeLookup(graph);
   const mroByClassDefId = provider.buildMro(graph, parsedFiles, nodeLookup);
+  const extendsOnlyMroByClassDefId = provider.buildExtendsOnlyMro?.(graph, parsedFiles, nodeLookup);
 
   const resolutionConfig = input.resolutionConfig;
   const finalized = finalizeScopeModel(parsedFiles, {
@@ -174,7 +175,7 @@ export function runScopeResolution(
   // the type system.
   const indexes = {
     ...finalized,
-    methodDispatch: buildPopulatedMethodDispatch(mroByClassDefId),
+    methodDispatch: buildPopulatedMethodDispatch(mroByClassDefId, extendsOnlyMroByClassDefId),
   };
 
   // Build the workspace resolution index ONCE — scope-valued lookups
@@ -275,6 +276,7 @@ export function runScopeResolution(
     {
       allowGlobalFallback: provider.allowGlobalFreeCallFallback === true,
       isFileLocalDef: provider.isFileLocalDef,
+      isCallableVisibleFromCaller: provider.isCallableVisibleFromCaller,
     },
   );
   const { emitted, skipped } = emitReferencesViaLookup(
diff --git a/gitnexus/src/core/ingestion/tree-sitter-queries.ts b/gitnexus/src/core/ingestion/tree-sitter-queries.ts
index 8e165a837..d65229808 100644
--- a/gitnexus/src/core/ingestion/tree-sitter-queries.ts
+++ b/gitnexus/src/core/ingestion/tree-sitter-queries.ts
@@ -1020,6 +1020,16 @@ export const PHP_QUERIES = `
     (use_declaration
       [(name) (qualified_name)] @heritage.trait))) @heritage
 
+; ── Heritage: trait uses another trait (transitive trait composition) ────────
+; PHP allows a trait body to contain "use OtherTrait;". The trait-uses-trait
+; IMPLEMENTS edge is required by buildPhpMro to compute the full transitive
+; trait closure (depth 3+ chains).
+(trait_declaration
+  name: (name) @heritage.class
+  body: (declaration_list
+    (use_declaration
+      [(name) (qualified_name)] @heritage.trait))) @heritage
+
 ; PHP HTTP consumers: file_get_contents('/path'), curl_init('/path')
 (function_call_expression
   function: (name) @_php_http (#match? @_php_http "^(file_get_contents|curl_init)$")
diff --git a/gitnexus/test/fixtures/lang-resolution/php-calls/app/Services/UserService.php b/gitnexus/test/fixtures/lang-resolution/php-calls/app/Services/UserService.php
index fa0a1b8be..882e12d64 100644
--- a/gitnexus/test/fixtures/lang-resolution/php-calls/app/Services/UserService.php
+++ b/gitnexus/test/fixtures/lang-resolution/php-calls/app/Services/UserService.php
@@ -2,10 +2,13 @@
 
 namespace App\Services;
 
-use function App\Utils\OneArg\log;
-use function App\Utils\ZeroArg\log as zero_log;
+use function App\Utils\OneArg\write_audit;
+use function App\Utils\ZeroArg\write_audit as zero_write_audit;
 
 function create_user(): string
 {
+    // Two visible write_audit candidates (different arities). Arity narrowing
+    // must pick the 1-arg OneArg version. This validates that visibility +
+    // arity together correctly disambiguate.
     return write_audit('hello');
 }
diff --git a/gitnexus/test/fixtures/lang-resolution/php-namespace-fallback-isolation/composer.json b/gitnexus/test/fixtures/lang-resolution/php-namespace-fallback-isolation/composer.json
new file mode 100644
index 000000000..3675b0d1c
--- /dev/null
+++ b/gitnexus/test/fixtures/lang-resolution/php-namespace-fallback-isolation/composer.json
@@ -0,0 +1,8 @@
+{
+  "autoload": {
+    "psr-4": {
+      "App\\": "src/App/",
+      "Vendor\\": "src/Vendor/"
+    }
+  }
+}
diff --git a/gitnexus/test/fixtures/lang-resolution/php-namespace-fallback-isolation/src/App/Caller.php b/gitnexus/test/fixtures/lang-resolution/php-namespace-fallback-isolation/src/App/Caller.php
new file mode 100644
index 000000000..6fecabb3c
--- /dev/null
+++ b/gitnexus/test/fixtures/lang-resolution/php-namespace-fallback-isolation/src/App/Caller.php
@@ -0,0 +1,19 @@
+<?php
+namespace App;
+
+use function Vendor\Utils\format as vendorFormat;
+
+class Caller {
+    public function callNoImport(): string {
+        // No use function for `format`. Caller is in \App, candidates live
+        // in \App\Utils and \Vendor\Utils. PHP runtime: Call to undefined
+        // function App\format. Resolver must emit NO edge.
+        return format('x');
+    }
+
+    public function callImported(): string {
+        // Imported via `use function Vendor\Utils\format as vendorFormat`.
+        // Resolver must emit an edge to Vendor\Utils\format.
+        return vendorFormat('x', 80);
+    }
+}
diff --git a/gitnexus/test/fixtures/lang-resolution/php-namespace-fallback-isolation/src/App/Utils/Caller.php b/gitnexus/test/fixtures/lang-resolution/php-namespace-fallback-isolation/src/App/Utils/Caller.php
new file mode 100644
index 000000000..b68ce2502
--- /dev/null
+++ b/gitnexus/test/fixtures/lang-resolution/php-namespace-fallback-isolation/src/App/Utils/Caller.php
@@ -0,0 +1,10 @@
+<?php
+namespace App\Utils;
+
+class Caller {
+    public function callSameNamespace(): string {
+        // Caller is in \App\Utils, calls `format('x')`. Same-namespace
+        // resolution: emit edge to \App\Utils\format.
+        return format('x');
+    }
+}
diff --git a/gitnexus/test/fixtures/lang-resolution/php-namespace-fallback-isolation/src/App/Utils/Format.php b/gitnexus/test/fixtures/lang-resolution/php-namespace-fallback-isolation/src/App/Utils/Format.php
new file mode 100644
index 000000000..5bd6c1172
--- /dev/null
+++ b/gitnexus/test/fixtures/lang-resolution/php-namespace-fallback-isolation/src/App/Utils/Format.php
@@ -0,0 +1,6 @@
+<?php
+namespace App\Utils;
+
+function format(string $s): string {
+    return $s;
+}
diff --git a/gitnexus/test/fixtures/lang-resolution/php-namespace-fallback-isolation/src/Vendor/Utils/Format.php b/gitnexus/test/fixtures/lang-resolution/php-namespace-fallback-isolation/src/Vendor/Utils/Format.php
new file mode 100644
index 000000000..4379e3f59
--- /dev/null
+++ b/gitnexus/test/fixtures/lang-resolution/php-namespace-fallback-isolation/src/Vendor/Utils/Format.php
@@ -0,0 +1,6 @@
+<?php
+namespace Vendor\Utils;
+
+function format(string $s, int $width): string {
+    return str_pad($s, $width);
+}
diff --git a/gitnexus/test/fixtures/lang-resolution/php-parent-vs-trait/app/Auditable.php b/gitnexus/test/fixtures/lang-resolution/php-parent-vs-trait/app/Auditable.php
new file mode 100644
index 000000000..15a0ef4b1
--- /dev/null
+++ b/gitnexus/test/fixtures/lang-resolution/php-parent-vs-trait/app/Auditable.php
@@ -0,0 +1,8 @@
+<?php
+namespace App;
+
+trait Auditable {
+    public function record(): string {
+        return 'trait';
+    }
+}
diff --git a/gitnexus/test/fixtures/lang-resolution/php-parent-vs-trait/app/Base.php b/gitnexus/test/fixtures/lang-resolution/php-parent-vs-trait/app/Base.php
new file mode 100644
index 000000000..ce9f31bde
--- /dev/null
+++ b/gitnexus/test/fixtures/lang-resolution/php-parent-vs-trait/app/Base.php
@@ -0,0 +1,8 @@
+<?php
+namespace App;
+
+class Base {
+    public function record(): string {
+        return 'base';
+    }
+}
diff --git a/gitnexus/test/fixtures/lang-resolution/php-parent-vs-trait/app/Child.php b/gitnexus/test/fixtures/lang-resolution/php-parent-vs-trait/app/Child.php
new file mode 100644
index 000000000..dc770899c
--- /dev/null
+++ b/gitnexus/test/fixtures/lang-resolution/php-parent-vs-trait/app/Child.php
@@ -0,0 +1,14 @@
+<?php
+namespace App;
+
+class Child extends Base {
+    use Auditable;
+
+    public function callViaParent(): string {
+        return parent::record();
+    }
+
+    public function callViaThis(): string {
+        return $this->record();
+    }
+}
diff --git a/gitnexus/test/fixtures/lang-resolution/php-parent-vs-trait/composer.json b/gitnexus/test/fixtures/lang-resolution/php-parent-vs-trait/composer.json
new file mode 100644
index 000000000..386b0bd2d
--- /dev/null
+++ b/gitnexus/test/fixtures/lang-resolution/php-parent-vs-trait/composer.json
@@ -0,0 +1,7 @@
+{
+  "autoload": {
+    "psr-4": {
+      "App\\": "app/"
+    }
+  }
+}
diff --git a/gitnexus/test/fixtures/lang-resolution/php-transitive-traits/app/Models/Consumer.php b/gitnexus/test/fixtures/lang-resolution/php-transitive-traits/app/Models/Consumer.php
new file mode 100644
index 000000000..86d330173
--- /dev/null
+++ b/gitnexus/test/fixtures/lang-resolution/php-transitive-traits/app/Models/Consumer.php
@@ -0,0 +1,20 @@
+<?php
+namespace App\Models;
+
+use App\Traits\TraitA;
+
+class Consumer {
+    use TraitA;
+
+    public function callDepthOne(): string {
+        return $this->aMethod();
+    }
+
+    public function callDepthTwo(): string {
+        return $this->bMethod();
+    }
+
+    public function callDepthThree(): string {
+        return $this->deepMethod();
+    }
+}
diff --git a/gitnexus/test/fixtures/lang-resolution/php-transitive-traits/app/Traits/TraitA.php b/gitnexus/test/fixtures/lang-resolution/php-transitive-traits/app/Traits/TraitA.php
new file mode 100644
index 000000000..4408b8dfb
--- /dev/null
+++ b/gitnexus/test/fixtures/lang-resolution/php-transitive-traits/app/Traits/TraitA.php
@@ -0,0 +1,10 @@
+<?php
+namespace App\Traits;
+
+trait TraitA {
+    use TraitB;
+
+    public function aMethod(): string {
+        return 'from A';
+    }
+}
diff --git a/gitnexus/test/fixtures/lang-resolution/php-transitive-traits/app/Traits/TraitB.php b/gitnexus/test/fixtures/lang-resolution/php-transitive-traits/app/Traits/TraitB.php
new file mode 100644
index 000000000..24414252a
--- /dev/null
+++ b/gitnexus/test/fixtures/lang-resolution/php-transitive-traits/app/Traits/TraitB.php
@@ -0,0 +1,10 @@
+<?php
+namespace App\Traits;
+
+trait TraitB {
+    use TraitC;
+
+    public function bMethod(): string {
+        return 'from B';
+    }
+}
diff --git a/gitnexus/test/fixtures/lang-resolution/php-transitive-traits/app/Traits/TraitC.php b/gitnexus/test/fixtures/lang-resolution/php-transitive-traits/app/Traits/TraitC.php
new file mode 100644
index 000000000..be3ba8318
--- /dev/null
+++ b/gitnexus/test/fixtures/lang-resolution/php-transitive-traits/app/Traits/TraitC.php
@@ -0,0 +1,8 @@
+<?php
+namespace App\Traits;
+
+trait TraitC {
+    public function deepMethod(): string {
+        return 'from C';
+    }
+}
diff --git a/gitnexus/test/fixtures/lang-resolution/php-transitive-traits/composer.json b/gitnexus/test/fixtures/lang-resolution/php-transitive-traits/composer.json
new file mode 100644
index 000000000..386b0bd2d
--- /dev/null
+++ b/gitnexus/test/fixtures/lang-resolution/php-transitive-traits/composer.json
@@ -0,0 +1,7 @@
+{
+  "autoload": {
+    "psr-4": {
+      "App\\": "app/"
+    }
+  }
+}
diff --git a/gitnexus/test/fixtures/lang-resolution/php-variadic-arity-minimum/app/Services/Caller.php b/gitnexus/test/fixtures/lang-resolution/php-variadic-arity-minimum/app/Services/Caller.php
new file mode 100644
index 000000000..1da29a43a
--- /dev/null
+++ b/gitnexus/test/fixtures/lang-resolution/php-variadic-arity-minimum/app/Services/Caller.php
@@ -0,0 +1,30 @@
+<?php
+namespace App\Services;
+
+use App\Utils\Logger;
+
+class Caller {
+    public function callValidRecord(): void {
+        Logger::record('info', 'started', 'processing', 'done');
+    }
+
+    public function callValidRecordMin(): void {
+        Logger::record('info');
+    }
+
+    public function callTooFewRecord(): void {
+        Logger::record();
+    }
+
+    public function callPureVariadic(): string {
+        return Logger::format();
+    }
+
+    public function callPadMin(): string {
+        return Logger::pad('x');
+    }
+
+    public function callPadTooFew(): string {
+        return Logger::pad();
+    }
+}
diff --git a/gitnexus/test/fixtures/lang-resolution/php-variadic-arity-minimum/app/Utils/Logger.php b/gitnexus/test/fixtures/lang-resolution/php-variadic-arity-minimum/app/Utils/Logger.php
new file mode 100644
index 000000000..469679111
--- /dev/null
+++ b/gitnexus/test/fixtures/lang-resolution/php-variadic-arity-minimum/app/Utils/Logger.php
@@ -0,0 +1,19 @@
+<?php
+namespace App\Utils;
+
+class Logger {
+    public static function record(string $level, string ...$messages): void {
+        foreach ($messages as $msg) {
+            echo "[$level] $msg\n";
+        }
+    }
+
+    public static function format(...$parts): string {
+        return implode('', array_map('strval', $parts));
+    }
+
+    public static function pad(string $s, int $w = 80, string ...$chars): string {
+        $pad = empty($chars) ? ' ' : implode('', $chars);
+        return str_pad($s, $w, $pad);
+    }
+}
diff --git a/gitnexus/test/fixtures/lang-resolution/php-variadic-arity-minimum/composer.json b/gitnexus/test/fixtures/lang-resolution/php-variadic-arity-minimum/composer.json
new file mode 100644
index 000000000..386b0bd2d
--- /dev/null
+++ b/gitnexus/test/fixtures/lang-resolution/php-variadic-arity-minimum/composer.json
@@ -0,0 +1,7 @@
+{
+  "autoload": {
+    "psr-4": {
+      "App\\": "app/"
+    }
+  }
+}
diff --git a/gitnexus/test/integration/resolvers/php.test.ts b/gitnexus/test/integration/resolvers/php.test.ts
index d930c9599..09fdac660 100644
--- a/gitnexus/test/integration/resolvers/php.test.ts
+++ b/gitnexus/test/integration/resolvers/php.test.ts
@@ -443,6 +443,162 @@ describe('PHP variadic call resolution', () => {
   });
 });
 
+// ---------------------------------------------------------------------------
+// Variadic arity minimum: required-arg count must be enforced for variadic
+// functions. f(int $req, ...$rest) called as f() is an ArgumentCountError at
+// PHP runtime and must NOT emit a CALLS edge from the resolver.
+// ---------------------------------------------------------------------------
+
+describe('PHP variadic arity minimum (U1)', () => {
+  let result: PipelineResult;
+
+  beforeAll(async () => {
+    result = await runPipelineFromRepo(path.join(FIXTURES, 'php-variadic-arity-minimum'), () => {});
+  }, 60000);
+
+  const callsFrom = (source: string, target: string) =>
+    getRelationships(result, 'CALLS').filter((c) => c.source === source && c.target === target);
+
+  it('emits CALLS edge for record(level, ...msgs) with arity 4 (happy path)', () => {
+    expect(callsFrom('callValidRecord', 'record').length).toBe(1);
+  });
+
+  it('emits CALLS edge for record(level) with only the required arg (arity 1)', () => {
+    expect(callsFrom('callValidRecordMin', 'record').length).toBe(1);
+  });
+
+  it('does NOT emit CALLS edge for record() with zero args (below required=1)', () => {
+    expect(callsFrom('callTooFewRecord', 'record').length).toBe(0);
+  });
+
+  it('emits CALLS edge for format() — pure variadic, required=0', () => {
+    expect(callsFrom('callPureVariadic', 'format').length).toBe(1);
+  });
+
+  it('emits CALLS edge for pad("x") — required+optional+variadic, only required given', () => {
+    expect(callsFrom('callPadMin', 'pad').length).toBe(1);
+  });
+
+  it('does NOT emit CALLS edge for pad() with zero args (below required=1)', () => {
+    expect(callsFrom('callPadTooFew', 'pad').length).toBe(0);
+  });
+});
+
+// ---------------------------------------------------------------------------
+// Transitive trait MRO: trait A uses B uses C — Consumer using A must see C's
+// methods. Current depth-2 expansion in buildPhpMro silently drops methods
+// from 3+ level chains.
+// ---------------------------------------------------------------------------
+
+describe('PHP transitive trait MRO (U2)', () => {
+  let result: PipelineResult;
+
+  beforeAll(async () => {
+    result = await runPipelineFromRepo(path.join(FIXTURES, 'php-transitive-traits'), () => {});
+  }, 60000);
+
+  const callsFrom = (source: string, target: string) =>
+    getRelationships(result, 'CALLS').filter((c) => c.source === source && c.target === target);
+
+  it('detects 3 traits and 1 class', () => {
+    expect(getNodesByLabel(result, 'Trait')).toEqual(['TraitA', 'TraitB', 'TraitC']);
+    expect(getNodesByLabel(result, 'Class')).toContain('Consumer');
+  });
+
+  it('depth-1: $this->aMethod() resolves to TraitA::aMethod', () => {
+    expect(callsFrom('callDepthOne', 'aMethod').length).toBeGreaterThanOrEqual(1);
+  });
+
+  it('depth-2: $this->bMethod() resolves to TraitB::bMethod (TraitA uses TraitB)', () => {
+    expect(callsFrom('callDepthTwo', 'bMethod').length).toBeGreaterThanOrEqual(1);
+  });
+
+  it('depth-3: $this->deepMethod() resolves to TraitC::deepMethod (TraitA → TraitB → TraitC)', () => {
+    expect(callsFrom('callDepthThree', 'deepMethod').length).toBeGreaterThanOrEqual(1);
+  });
+});
+
+// ---------------------------------------------------------------------------
+// parent:: bypasses traits. When a class composes a trait AND extends a parent
+// that both define the same method name, parent::method() must resolve to the
+// parent class (PHP semantics), NOT the trait. $this->method() still goes to
+// the trait (PHP's own-class > trait > parent precedence).
+// ---------------------------------------------------------------------------
+
+describe('PHP parent:: bypasses traits (U3)', () => {
+  let result: PipelineResult;
+
+  beforeAll(async () => {
+    result = await runPipelineFromRepo(path.join(FIXTURES, 'php-parent-vs-trait'), () => {});
+  }, 60000);
+
+  const callsFromTo = (source: string, target: string, file: string) =>
+    getRelationships(result, 'CALLS').filter(
+      (c) => c.source === source && c.target === target && c.targetFilePath === file,
+    );
+
+  it('parent::record() resolves to Base::record, NOT Auditable::record', () => {
+    expect(callsFromTo('callViaParent', 'record', 'app/Base.php').length).toBeGreaterThanOrEqual(1);
+    expect(callsFromTo('callViaParent', 'record', 'app/Auditable.php').length).toBe(0);
+  });
+
+  it('$this->record() still resolves to Auditable::record (trait shadows parent)', () => {
+    expect(callsFromTo('callViaThis', 'record', 'app/Auditable.php').length).toBeGreaterThanOrEqual(
+      1,
+    );
+    expect(callsFromTo('callViaThis', 'record', 'app/Base.php').length).toBe(0);
+  });
+});
+
+// ---------------------------------------------------------------------------
+// Namespace-aware free-call fallback. PHP's `pickUniqueGlobalCallable` must
+// reject cross-namespace candidates that the caller can't reach without an
+// explicit `use function` import. Same-namespace and globally-imported calls
+// still emit edges.
+// ---------------------------------------------------------------------------
+
+describe('PHP namespace-aware free-call fallback (U4)', () => {
+  let result: PipelineResult;
+
+  beforeAll(async () => {
+    result = await runPipelineFromRepo(
+      path.join(FIXTURES, 'php-namespace-fallback-isolation'),
+      () => {},
+    );
+  }, 60000);
+
+  const callsFromTo = (source: string, target: string, file?: string) =>
+    getRelationships(result, 'CALLS').filter(
+      (c) =>
+        c.source === source &&
+        c.target === target &&
+        (file === undefined || c.targetFilePath === file),
+    );
+
+  it('rejects cross-namespace candidate when caller has no use-function import', () => {
+    // callNoImport (in \App) calls format('x'). Workspace has \App\Utils\format/1
+    // and \Vendor\Utils\format/2. Caller is in \App — NOT same namespace as
+    // either candidate, and no `use function` for `format` is in scope.
+    // Expected: NO CALLS edge.
+    expect(callsFromTo('callNoImport', 'format').length).toBe(0);
+  });
+
+  it('resolves same-namespace free call (caller in App\\Utils → App\\Utils\\format)', () => {
+    expect(
+      callsFromTo('callSameNamespace', 'format', 'src/App/Utils/Format.php').length,
+    ).toBeGreaterThanOrEqual(1);
+  });
+
+  it('resolves use-function-imported alias (vendorFormat → Vendor\\Utils\\format)', () => {
+    // `use function Vendor\Utils\format as vendorFormat;`. Caller in \App calls
+    // vendorFormat('x', 80) — the import target is reachable.
+    expect(
+      callsFromTo('callImported', 'vendorFormat').length +
+        callsFromTo('callImported', 'format', 'src/Vendor/Utils/Format.php').length,
+    ).toBeGreaterThanOrEqual(1);
+  });
+});
+
 // ---------------------------------------------------------------------------
 // Local shadow: same-file definition takes priority over imported name
 // ---------------------------------------------------------------------------