diff --git a/gitnexus/src/core/ingestion/scope-resolution/passes/unique-name-properties.ts b/gitnexus/src/core/ingestion/scope-resolution/passes/unique-name-properties.ts
index a46c71497..604383b27 100644
--- a/gitnexus/src/core/ingestion/scope-resolution/passes/unique-name-properties.ts
+++ b/gitnexus/src/core/ingestion/scope-resolution/passes/unique-name-properties.ts
@@ -140,6 +140,7 @@ export interface UniqueNamePropertyStats {
  */
 function indexPropertyNodesByName(
   graph: KnowledgeGraph,
+  ownFilePaths: ReadonlySet<string>,
 ): ReadonlyMap<string, readonly PropertyCandidate[] | null> {
   const byName = new Map<string, PropertyCandidate[] | null>();
   for (const node of graph.iterNodes()) {
@@ -147,12 +148,21 @@ function indexPropertyNodesByName(
     const name = node.properties.name;
     if (typeof name !== 'string' || name.length === 0) continue;
     const filePath = node.properties.filePath;
+    // SAME LANGUAGE ONLY. The graph is shared across every language in the
+    // repo, and `fieldFallbackOnMethodLookup` only decides whether this pass
+    // RUNS for a language — it never restricted which nodes could be TARGETS.
+    // So a Java backend declaring `private int loyaltyPoints` was the unique
+    // carrier of that name, and a JS frontend writing `cfg.loyaltyPoints` on an
+    // untyped parameter got an edge to it: no owner, file, or language evidence,
+    // and inference across a language boundary that has no call path at all.
+    // The confidence tier does not save it, since `minConfidence` defaults to 0.
+    //
+    // `parsedFiles` is exactly this language's file set, so matching on it is a
+    // precise restriction rather than a heuristic — no node property needed.
+    if (typeof filePath !== 'string' || !ownFilePaths.has(filePath)) continue;
     const existing = byName.get(name);
     if (existing === OVERSATURATED) continue;
-    const candidate: PropertyCandidate = {
-      id: node.id,
-      filePath: typeof filePath === 'string' ? filePath : '',
-    };
+    const candidate: PropertyCandidate = { id: node.id, filePath };
     if (existing === undefined) {
       byName.set(name, [candidate]);
       continue;
@@ -245,7 +255,7 @@ export function emitUniqueNamePropertyAccesses(
   /** Finalized import graph; narrows a name carried by several definitions. */
   finalized?: FinalizedImportView,
 ): UniqueNamePropertyStats {
-  const byName = indexPropertyNodesByName(graph);
+  const byName = indexPropertyNodesByName(graph, new Set(parsedFiles.map((p) => p.filePath)));
   if (byName.size === 0) {
     return { emitted: 0, ambiguous: 0, narrowed: 0, ambiguousNames: [] };
   }
diff --git a/gitnexus/test/fixtures/lang-resolution/polyglot-property-isolation/Loyalty.java b/gitnexus/test/fixtures/lang-resolution/polyglot-property-isolation/Loyalty.java
new file mode 100644
index 000000000..16d731460
--- /dev/null
+++ b/gitnexus/test/fixtures/lang-resolution/polyglot-property-isolation/Loyalty.java
@@ -0,0 +1,11 @@
+// RV-5: the ONLY declaration of `loyaltyPointsBalance` in the workspace, and it
+// is Java. Nothing in the JS file below can call into it.
+package shop;
+
+public class Loyalty {
+    private int loyaltyPointsBalance;
+
+    public int read() {
+        return loyaltyPointsBalance;
+    }
+}
diff --git a/gitnexus/test/fixtures/lang-resolution/polyglot-property-isolation/settings.js b/gitnexus/test/fixtures/lang-resolution/polyglot-property-isolation/settings.js
new file mode 100644
index 000000000..f6e16684d
--- /dev/null
+++ b/gitnexus/test/fixtures/lang-resolution/polyglot-property-isolation/settings.js
@@ -0,0 +1,16 @@
+// A JS read of the same name through an untyped receiver. Workspace-wide the
+// name is unique, so unique-name inference resolved it — to a Java private
+// field, across a language boundary with no call path.
+export function renderLoyalty(cfg) {
+  return cfg.loyaltyPointsBalance;
+}
+
+// CONTROL: a same-language target the pass SHOULD still reach, so the fix is
+// shown to restrict by language rather than to disable the pass.
+export const jsConfig = {
+  jsOnlyThreshold: 10,
+};
+
+export function readsJsOnly(bag) {
+  return bag.jsOnlyThreshold;
+}
diff --git a/gitnexus/test/integration/resolvers/polyglot-property-isolation.test.ts b/gitnexus/test/integration/resolvers/polyglot-property-isolation.test.ts
new file mode 100644
index 000000000..0d1ecd66e
--- /dev/null
+++ b/gitnexus/test/integration/resolvers/polyglot-property-isolation.test.ts
@@ -0,0 +1,43 @@
+/**
+ * RV-5 — unique-name property inference must not cross a language boundary.
+ *
+ * The pass indexed `Property` nodes from the whole shared graph. Per-language
+ * gating (`fieldFallbackOnMethodLookup`) decides whether the pass RUNS for a
+ * language; it never restricted which nodes could be TARGETS. So the only
+ * carrier of a name might be in another language entirely, and a read here
+ * resolved to it on name uniqueness alone — no owner, no file, no call path.
+ *
+ * Confidence does not mitigate it: `minConfidence` defaults to 0, so a consumer
+ * gets the edge unless it opts out explicitly.
+ *
+ * Every other fixture is single-language, so this could not be caught by
+ * construction anywhere in the suite.
+ */
+import { describe, it, expect, beforeAll } from 'vitest';
+import path from 'path';
+import { FIXTURES, getRelationships, runPipelineFromRepo, type PipelineResult } from './helpers.js';
+
+describe('cross-language property inference (RV-5)', () => {
+  let result: PipelineResult;
+
+  beforeAll(async () => {
+    result = await runPipelineFromRepo(
+      path.join(FIXTURES, 'polyglot-property-isolation'),
+      () => {},
+    );
+  }, 60000);
+
+  const readersOf = (field: string): string[] =>
+    getRelationships(result, 'ACCESSES')
+      .filter((e) => e.target === field)
+      .map((e) => e.source);
+
+  it('does not link a JS read to a Java field of the same name', () => {
+    expect(readersOf('loyaltyPointsBalance')).not.toContain('renderLoyalty');
+  });
+
+  // The other half: restricting by language must not disable the pass.
+  it('still resolves a same-language unique name', () => {
+    expect(readersOf('jsOnlyThreshold')).toContain('readsJsOnly');
+  });
+});