diff --git a/gitnexus/src/core/ingestion/languages/r/package-config.ts b/gitnexus/src/core/ingestion/languages/r/package-config.ts
index 490dcf7b6..7b2294146 100644
--- a/gitnexus/src/core/ingestion/languages/r/package-config.ts
+++ b/gitnexus/src/core/ingestion/languages/r/package-config.ts
@@ -1,3 +1,4 @@
+import type { Dirent } from 'fs';
 import fs from 'fs/promises';
 import path from 'path';
 import {
@@ -18,7 +19,13 @@ export interface RDroppedExportPattern {
 
 /** R package config parsed from DESCRIPTION files in a multi-package repo */
 export interface RPackageConfig {
-  /** Map of package name to directory path relative to repo root */
+  /**
+   * Map of package name to directory path relative to repo root, in discovery
+   * order. When several directories declare the same `Package:` name the
+   * shallowest directory wins and, among equal depths, the path that sorts
+   * first; the others are not entries here (their NAMESPACE is still recorded
+   * in {@link namespaceInfoByPackageDir}, which is keyed by directory).
+   */
   packages: Map<string, string>;
   /** Package-scoped NAMESPACE config keyed by package dir relative to repo root. */
   namespaceInfoByPackageDir: Map<string, RNamespaceInfo>;
@@ -105,6 +112,16 @@ export function reportRExportPatternProblems(config: RPackageConfig): void {
 /** Directories never descended into, by the main walk and the hidden-package scan alike. */
 const SKIPPED_DIR_NAMES: ReadonlySet<string> = new Set(['node_modules', '.git', '.Rproj.user']);
 
+/**
+ * Directory entries in code-unit name order. `readdir` order is filesystem-dependent
+ * (and `localeCompare` is locale-dependent), so every walk below reads through this to
+ * make what it visits, and what it finds first, the same on every machine.
+ */
+async function readDirSorted(dir: string): Promise<Dirent[]> {
+  const entries = await fs.readdir(dir, { withFileTypes: true });
+  return entries.sort((a, b) => (a.name < b.name ? -1 : a.name > b.name ? 1 : 0));
+}
+
 /** Global directory budget for {@link hidesUndiscoveredPackage} across all its roots. */
 const HIDDEN_SCAN_BUDGET = 5000;
 
@@ -117,6 +134,9 @@ const HIDDEN_SCAN_BUDGET = 5000;
  * directory or `DESCRIPTION` cannot be read, or when a `DESCRIPTION` declares a
  * `Package:` name that is not in `knownPackageNames`. Returns `false` when every
  * subtree was scanned and holds no such package. Deterministic and read-only.
+ * The answer is a property of the set of directories, not of the order they are
+ * visited in (every `true` condition is order-independent and a `false` means the
+ * whole forest was read), but the walk still reads sorted so that it is reproducible.
  */
 export async function hidesUndiscoveredPackage(
   roots: readonly string[],
@@ -129,7 +149,7 @@ export async function hidesUndiscoveredPackage(
     if (--remaining < 0) return true;
     let entries;
     try {
-      entries = await fs.readdir(dir, { withFileTypes: true });
+      entries = await readDirSorted(dir);
     } catch {
       return true;
     }
@@ -172,7 +192,7 @@ export async function loadRPackageConfig(repoRoot: string): Promise<RPackageConf
     const { dir, depth } = scanQueue.shift()!;
     dirsScanned++;
     try {
-      const entries = await fs.readdir(dir, { withFileTypes: true });
+      const entries = await readDirSorted(dir);
       for (const entry of entries) {
         if (entry.isDirectory()) {
           if (SKIPPED_DIR_NAMES.has(entry.name)) continue;
@@ -192,9 +212,14 @@ export async function loadRPackageConfig(repoRoot: string): Promise<RPackageConf
             if (pkgMatch) {
               const pkgName = pkgMatch[1];
               const pkgDir = path.relative(repoRoot, dir).replace(/\\/g, '/');
-              packages.set(pkgName, pkgDir);
-              if (isDev) {
-                logger.info(`📦 Found R package: ${pkgName} at ${pkgDir}`);
+              // Same name in several directories: the walk is breadth-first over sorted
+              // entries, so the first one seen is the shallowest and, at equal depth, the
+              // one whose path sorts first. Keep it; never let a later copy replace it.
+              if (!packages.has(pkgName)) {
+                packages.set(pkgName, pkgDir);
+                if (isDev) {
+                  logger.info(`📦 Found R package: ${pkgName} at ${pkgDir}`);
+                }
               }
 
               const nsPath = path.join(dir, 'NAMESPACE');
diff --git a/gitnexus/test/unit/r-package-discovery-order.test.ts b/gitnexus/test/unit/r-package-discovery-order.test.ts
new file mode 100644
index 000000000..e5c2c2f6d
--- /dev/null
+++ b/gitnexus/test/unit/r-package-discovery-order.test.ts
@@ -0,0 +1,178 @@
+/**
+ * R package discovery must not depend on the order in which the filesystem lists
+ * directory entries (ext4 hash order, APFS, NTFS and overlayfs all differ).
+ *
+ * `readdir` is intercepted so a real temporary tree is listed in ascending,
+ * descending and seeded-shuffled order; the discovery result has to be the same
+ * for every order. A one-order test could pass by accident on a filesystem that
+ * happens to list entries sorted.
+ */
+import { afterAll, beforeAll, beforeEach, describe, expect, it, vi } from 'vitest';
+import fsReal from 'node:fs/promises';
+import os from 'node:os';
+import path from 'node:path';
+import {
+  hidesUndiscoveredPackage,
+  loadRPackageConfig,
+  type RPackageConfig,
+} from '../../src/core/ingestion/languages/r/package-config.js';
+
+type Order = 'asc' | 'desc' | number;
+const box = vi.hoisted(() => ({ order: 'asc' as 'asc' | 'desc' | number }));
+
+/** Reproducible Fisher-Yates (LCG seeded), so a failing order can be replayed. */
+function reorder<T extends { name: string }>(entries: readonly T[], order: Order): T[] {
+  const out = [...entries].sort((a, b) => (a.name < b.name ? -1 : a.name > b.name ? 1 : 0));
+  if (order === 'asc') return out;
+  if (order === 'desc') return out.reverse();
+  let s = order;
+  const rand = (): number => {
+    s = (s * 1103515245 + 12345) & 0x7fffffff;
+    return s / 0x7fffffff;
+  };
+  for (let i = out.length - 1; i > 0; i--) {
+    const j = Math.floor(rand() * (i + 1));
+    [out[i], out[j]] = [out[j]!, out[i]!];
+  }
+  return out;
+}
+
+vi.mock('fs/promises', async (importOriginal) => {
+  const actual = await importOriginal<typeof import('fs/promises')>();
+  const base = (actual as unknown as { default: typeof actual }).default ?? actual;
+  const readdir = (async (...args: Parameters<typeof actual.readdir>) => {
+    const entries = await (base.readdir as (...a: unknown[]) => Promise<unknown>)(...args);
+    return Array.isArray(entries) && entries.every((e) => typeof e === 'object' && e !== null)
+      ? reorder(entries as { name: string }[], box.order)
+      : entries;
+  }) as typeof actual.readdir;
+  return { ...actual, readdir, default: { ...base, readdir } };
+});
+
+const ORDERS: readonly Order[] = ['asc', 'desc', 1, 2, 3, 4, 5];
+
+let tmp: string;
+let counter = 0;
+
+async function write(root: string, rel: string, content: string): Promise<void> {
+  const full = path.join(root, rel);
+  await fsReal.mkdir(path.dirname(full), { recursive: true });
+  await fsReal.writeFile(full, content);
+}
+
+const desc = (name: string): string => `Package: ${name}\nVersion: 1.0\n`;
+
+async function newRepo(): Promise<string> {
+  const root = path.join(tmp, `repo${counter++}`);
+  await fsReal.mkdir(root, { recursive: true });
+  return root;
+}
+
+/** Everything observable about a config, including Map iteration order. */
+function snapshot(cfg: RPackageConfig): unknown {
+  return {
+    packages: [...cfg.packages],
+    namespaces: [...cfg.namespaceInfoByPackageDir.keys()],
+    truncated: cfg.truncated,
+  };
+}
+
+async function discover(root: string, order: Order): Promise<RPackageConfig> {
+  box.order = order;
+  return loadRPackageConfig(root);
+}
+
+describe('R package discovery is independent of readdir order', () => {
+  beforeAll(async () => {
+    tmp = await fsReal.mkdtemp(path.join(os.tmpdir(), 'gn-r-order-'));
+  });
+  afterAll(async () => {
+    box.order = 'asc';
+    await fsReal.rm(tmp, { recursive: true, force: true });
+  });
+  beforeEach(() => {
+    box.order = 'asc';
+  });
+
+  it('same-depth duplicate package names resolve to the path that sorts first', async () => {
+    const root = await newRepo();
+    for (const dir of ['mm', 'zz', 'aa']) await write(root, `${dir}/DESCRIPTION`, desc('dup'));
+    for (const order of ORDERS) {
+      const cfg = await discover(root, order);
+      expect(cfg.packages.get('dup'), `order ${String(order)}`).toBe('aa');
+      expect(cfg.packages.size).toBe(1);
+    }
+  });
+
+  it('the shallowest duplicate wins even when a deeper one sorts earlier', async () => {
+    const root = await newRepo();
+    await write(root, 'aaa/nested/DESCRIPTION', desc('dup'));
+    await write(root, 'zzz/DESCRIPTION', desc('dup'));
+    for (const order of ORDERS) {
+      const cfg = await discover(root, order);
+      expect(cfg.packages.get('dup'), `order ${String(order)}`).toBe('zzz');
+    }
+  });
+
+  it('a root-level package beats a nested package of the same name', async () => {
+    const root = await newRepo();
+    await write(root, 'DESCRIPTION', desc('dup'));
+    await write(root, 'inst/copy/DESCRIPTION', desc('dup'));
+    for (const order of ORDERS) {
+      expect((await discover(root, order)).packages.get('dup'), `order ${String(order)}`).toBe('');
+    }
+  });
+
+  it('packages and NAMESPACE entries come back in the same order for every listing order', async () => {
+    const root = await newRepo();
+    for (const name of ['delta', 'alpha', 'charlie', 'bravo']) {
+      await write(root, `pkgs/${name}/DESCRIPTION`, desc(name));
+      await write(root, `pkgs/${name}/NAMESPACE`, `export(${name}_fn)\n`);
+    }
+    const reference = snapshot(await discover(root, 'asc'));
+    expect((reference as { packages: [string, string][] }).packages.map(([n]) => n)).toEqual([
+      'alpha',
+      'bravo',
+      'charlie',
+      'delta',
+    ]);
+    for (const order of ORDERS) expect(snapshot(await discover(root, order))).toEqual(reference);
+  });
+
+  it('the 200-directory cap keeps the same packages and the same truncated flag', async () => {
+    const root = await newRepo();
+    // 250 sibling directories (root counts as the first scanned one): whichever 199 the
+    // walk reads first decide what is discovered. d010 is read, d240 is not.
+    for (let i = 0; i < 250; i++) {
+      const dir = `d${String(i).padStart(3, '0')}`;
+      await fsReal.mkdir(path.join(root, dir), { recursive: true });
+    }
+    await write(root, 'd010/DESCRIPTION', desc('early'));
+    await write(root, 'd240/DESCRIPTION', desc('late'));
+    const reference = await discover(root, 'asc');
+    expect([...reference.packages.keys()]).toEqual(['early']);
+    expect(reference.truncated).toBe(true);
+    for (const order of ORDERS)
+      expect(snapshot(await discover(root, order))).toEqual(snapshot(reference));
+  });
+
+  it('the hidden-package scan answers the same for every listing order', async () => {
+    const root = await newRepo();
+    await write(root, 'a/b/c/known/DESCRIPTION', desc('known'));
+    await write(root, 'a/b/c/z/deep/DESCRIPTION', desc('unknown'));
+    await write(root, 'q/none/file.txt', 'x');
+    const clean = await newRepo();
+    await write(clean, 'a/b/c/known/DESCRIPTION', desc('known'));
+    await write(clean, 'q/none/file.txt', 'x');
+    for (const order of ORDERS) {
+      box.order = order;
+      const known = new Set(['known']);
+      expect(await hidesUndiscoveredPackage([root], known), `hidden, ${String(order)}`).toBe(true);
+      expect(await hidesUndiscoveredPackage([clean], known), `clean, ${String(order)}`).toBe(false);
+      // Budget exhaustion is a count of directories, not of an order.
+      expect(await hidesUndiscoveredPackage([clean], known, 2), `budget, ${String(order)}`).toBe(
+        true,
+      );
+    }
+  });
+});