diff --git a/src/app/(dashboard)/dashboard/costs/quota-share/components/PoolCard.tsx b/src/app/(dashboard)/dashboard/costs/quota-share/components/PoolCard.tsx
index 6bae71c651..bd131e0841 100644
--- a/src/app/(dashboard)/dashboard/costs/quota-share/components/PoolCard.tsx
+++ b/src/app/(dashboard)/dashboard/costs/quota-share/components/PoolCard.tsx
@@ -24,8 +24,9 @@ export interface PoolCardProps {
 }
 
 function computeStatus(usage: PoolUsageSnapshot | null): "green" | "amber" | "red" {
-  if (!usage || usage.dimensions.length === 0) return "green";
-  const utilizations = usage.dimensions.map((d) =>
+  const dims = usage?.dimensions ?? [];
+  if (dims.length === 0) return "green";
+  const utilizations = dims.map((d) =>
     d.limit > 0 ? (d.consumedTotal / d.limit) * 100 : 0
   );
   const avg = utilizations.reduce((s, u) => s + u, 0) / utilizations.length;
@@ -54,7 +55,7 @@ export default function PoolCard({
   const { icon: statusIcon, cls: statusCls } = STATUS_ICONS[status];
 
   // Check for plan dimensions from usage
-  const hasDimensions = usage && usage.dimensions.length > 0;
+  const hasDimensions = !!usage?.dimensions?.length;
 
   return (
     <Card padding="md">
@@ -103,10 +104,10 @@ export default function PoolCard({
         <div
           className="grid gap-3 mb-3"
           style={{
-            gridTemplateColumns: `repeat(${Math.min(usage.dimensions.length, 3)}, 1fr)`,
+            gridTemplateColumns: `repeat(${Math.min(usage?.dimensions?.length ?? 0, 3)}, 1fr)`,
           }}
         >
-          {usage.dimensions.map((dim, i) => (
+          {(usage?.dimensions ?? []).map((dim, i) => (
             <DimensionBar
               key={`${dim.unit}-${dim.window}-${i}`}
               dimension={{ unit: dim.unit, window: dim.window, limit: dim.limit }}
diff --git a/src/app/(dashboard)/dashboard/costs/quota-share/hooks/usePoolsUsageAggregate.ts b/src/app/(dashboard)/dashboard/costs/quota-share/hooks/usePoolsUsageAggregate.ts
index 545016466e..ad00893cfd 100644
--- a/src/app/(dashboard)/dashboard/costs/quota-share/hooks/usePoolsUsageAggregate.ts
+++ b/src/app/(dashboard)/dashboard/costs/quota-share/hooks/usePoolsUsageAggregate.ts
@@ -40,12 +40,12 @@ export function usePoolsUsageAggregate(pools: QuotaPool[]): PoolsUsageAggregate
         let utilCount = 0;
         let borrowing = 0;
         for (const { usage } of valid) {
-          for (const dim of usage.dimensions) {
+          for (const dim of usage.dimensions ?? []) {
             if (dim.limit > 0) {
               totalUtil += (dim.consumedTotal / dim.limit) * 100;
               utilCount += 1;
             }
-            for (const key of dim.perKey) {
+            for (const key of dim.perKey ?? []) {
               if (key.borrowing) borrowing += 1;
             }
           }
diff --git a/tests/unit/v388-quota-share-usage-guard.test.ts b/tests/unit/v388-quota-share-usage-guard.test.ts
new file mode 100644
index 0000000000..206379e22c
--- /dev/null
+++ b/tests/unit/v388-quota-share-usage-guard.test.ts
@@ -0,0 +1,23 @@
+import test from "node:test";
+import assert from "node:assert/strict";
+import { readFileSync } from "node:fs";
+import { join } from "node:path";
+
+// Regression guard: quota-share crashed with "Cannot read properties of undefined
+// (reading 'length')" because PoolCard/aggregate read usage.dimensions without a
+// guard when the usage snapshot came back without a dimensions array.
+const root = join(import.meta.dirname, "../..");
+const read = (p: string) => readFileSync(join(root, p), "utf8");
+
+test("quota-share PoolCard guards usage.dimensions", () => {
+  const pc = read("src/app/(dashboard)/dashboard/costs/quota-share/components/PoolCard.tsx");
+  assert.ok(pc.includes("usage?.dimensions ?? []"), "computeStatus normalizes dimensions to []");
+  assert.ok(pc.includes("!!usage?.dimensions?.length"), "hasDimensions guards dimensions");
+  assert.equal(/[^?.]usage\.dimensions\.length/.test(pc), false, "no unguarded usage.dimensions.length");
+});
+
+test("quota-share aggregate hook guards dimensions/perKey", () => {
+  const agg = read("src/app/(dashboard)/dashboard/costs/quota-share/hooks/usePoolsUsageAggregate.ts");
+  assert.ok(agg.includes("usage.dimensions ?? []"), "iterates dimensions with ?? []");
+  assert.ok(agg.includes("dim.perKey ?? []"), "iterates perKey with ?? []");
+});