diff --git a/src/shared/constants/sidebarVisibility.ts b/src/shared/constants/sidebarVisibility.ts
index 613d3805a8..42aed0cfdc 100644
--- a/src/shared/constants/sidebarVisibility.ts
+++ b/src/shared/constants/sidebarVisibility.ts
@@ -195,6 +195,13 @@ const OMNI_PROXY_ITEMS: readonly SidebarItemDefinition[] = [
     subtitleKey: "providerQuotaSubtitle",
     icon: "tune",
   },
+  {
+    id: "costs-quota-share",
+    href: "/dashboard/costs/quota-share",
+    i18nKey: "costsQuotaShare",
+    subtitleKey: "costsQuotaShareSubtitle",
+    icon: "pie_chart",
+  },
 ];
 
 const COMPRESSION_CONTEXT_GROUP: SidebarItemGroup = {
@@ -454,13 +461,6 @@ const COSTS_ITEMS: readonly SidebarItemDefinition[] = [
     subtitleKey: "costsBudgetSubtitle",
     icon: "savings",
   },
-  {
-    id: "costs-quota-share",
-    href: "/dashboard/costs/quota-share",
-    i18nKey: "costsQuotaShare",
-    subtitleKey: "costsQuotaShareSubtitle",
-    icon: "pie_chart",
-  },
 ];
 
 const AUDIT_GROUP: SidebarItemGroup = {
diff --git a/tests/unit/sidebar-quota-share-placement.test.ts b/tests/unit/sidebar-quota-share-placement.test.ts
new file mode 100644
index 0000000000..8118e5ade6
--- /dev/null
+++ b/tests/unit/sidebar-quota-share-placement.test.ts
@@ -0,0 +1,77 @@
+/**
+ * tests/unit/sidebar-quota-share-placement.test.ts
+ *
+ * Task 3 — source-scan assertions for Quota Share nav item placement.
+ *
+ * Asserts that `costs-quota-share` sits immediately after `quota` (Provider Quota)
+ * in the SAME array, and is no longer in the costs section array.
+ *
+ * Pattern mirrors: tests/unit/quota-groups-ui.test.ts (readFileSync style)
+ *
+ * Node.js native test runner — no DOM setup required.
+ */
+
+import test from "node:test";
+import assert from "node:assert/strict";
+import { readFileSync } from "node:fs";
+import { join, dirname } from "node:path";
+import { fileURLToPath } from "node:url";
+
+const ROOT = join(dirname(fileURLToPath(import.meta.url)), "..", "..");
+
+const SIDEBAR_PATH = join(ROOT, "src/shared/constants/sidebarVisibility.ts");
+
+const src = readFileSync(SIDEBAR_PATH, "utf8");
+
+// ── Placement order: costs-quota-share must come AFTER quota ─────────────────
+
+test("sidebar: costs-quota-share appears after quota in source", () => {
+  const idxQuota = src.indexOf('id: "quota"');
+  const idxQuotaShare = src.indexOf('id: "costs-quota-share"');
+  assert.ok(idxQuota >= 0, 'Could not find id: "quota" in sidebarVisibility.ts');
+  assert.ok(idxQuotaShare >= 0, 'Could not find id: "costs-quota-share" in sidebarVisibility.ts');
+  assert.ok(
+    idxQuotaShare > idxQuota,
+    `costs-quota-share (idx ${idxQuotaShare}) must appear AFTER quota (idx ${idxQuota})`
+  );
+});
+
+// ── Same array: no array-close ]; between quota and costs-quota-share ─────────
+
+test("sidebar: no array close ]; between quota and costs-quota-share (same array)", () => {
+  const idxQuota = src.indexOf('id: "quota"');
+  const idxQuotaShare = src.indexOf('id: "costs-quota-share"');
+  assert.ok(idxQuota >= 0, 'Could not find id: "quota"');
+  assert.ok(idxQuotaShare >= 0, 'Could not find id: "costs-quota-share"');
+  const between = src.slice(idxQuota, idxQuotaShare);
+  assert.ok(
+    !between.includes("];"),
+    `There must be NO array-close ]; between quota and costs-quota-share. Found one, meaning they are in different arrays.\nSlice between them:\n${between}`
+  );
+});
+
+// ── Costs section no longer contains costs-quota-share ───────────────────────
+
+test("sidebar: costs section does not have costs-quota-share right after costs-budget", () => {
+  // costs-budget and costs-quota-share should NOT be close neighbours (within 200 chars)
+  const idxBudget = src.indexOf('id: "costs-budget"');
+  const idxQuotaShare = src.indexOf('id: "costs-quota-share"');
+  assert.ok(idxBudget >= 0, 'Could not find id: "costs-budget"');
+  assert.ok(idxQuotaShare >= 0, 'Could not find id: "costs-quota-share"');
+  const gap = Math.abs(idxQuotaShare - idxBudget);
+  assert.ok(
+    gap > 200,
+    `costs-quota-share must NOT be immediately after costs-budget in the costs section (gap: ${gap} chars, expected > 200)`
+  );
+});
+
+// ── Exactly one occurrence of costs-quota-share ───────────────────────────────
+
+test("sidebar: exactly one occurrence of costs-quota-share", () => {
+  const occurrences = src.split('id: "costs-quota-share"').length - 1;
+  assert.equal(
+    occurrences,
+    1,
+    `Expected exactly 1 occurrence of id: "costs-quota-share", found ${occurrences}`
+  );
+});