From 4528c836d6af103c128a0a50e065317ad8328a57 Mon Sep 17 00:00:00 2001
From: ReplayX Bot <replayx-bot@users.noreply.github.com>
Date: Mon, 20 Apr 2026 01:06:44 +0530
Subject: [PATCH] fix(checkout-api): resolve checkout-race-condition

---
 demo_app/src/checkout/submit-order.ts   | 14 +++++++++++++-
 demo_app/src/inventory/reserve-stock.ts |  9 +++++++--
 2 files changed, 20 insertions(+), 3 deletions(-)

diff --git a/demo_app/src/checkout/submit-order.ts b/demo_app/src/checkout/submit-order.ts
index dd6d47f..af2fdb7 100644
--- a/demo_app/src/checkout/submit-order.ts
+++ b/demo_app/src/checkout/submit-order.ts
@@ -14,5 +14,17 @@ export const runCheckoutRaceScenario = async (mode: "concurrent" | "serial"): Pr
     return [await processCheckoutWorker(requests[0])];
   }
 
-  return Promise.all(requests.map((request) => processCheckoutWorker(request)));
+  const settled = await Promise.allSettled(requests.map((request) => processCheckoutWorker(request)));
+
+  const hardFailure = settled.find(
+    (result) =>
+      result.status === "rejected" &&
+      !(result.reason instanceof Error && result.reason.message.startsWith("OutOfStock:"))
+  );
+
+  if (hardFailure && hardFailure.status === "rejected") {
+    throw hardFailure.reason;
+  }
+
+  return settled.flatMap((result) => (result.status === "fulfilled" ? [result.value] : []));
 };
diff --git a/demo_app/src/inventory/reserve-stock.ts b/demo_app/src/inventory/reserve-stock.ts
index 08276cd..d925657 100644
--- a/demo_app/src/inventory/reserve-stock.ts
+++ b/demo_app/src/inventory/reserve-stock.ts
@@ -19,6 +19,11 @@ export const reserveStock = async (sku: string, quantity: number, requestId: str
   await delay(25);
 
   const record = getInventoryRecord(sku);
+
+  if (record.available < quantity) {
+    throw new Error(`OutOfStock: ${sku}`);
+  }
+
   record.available -= quantity;
   record.snapshotVersion += 1;
 
@@ -29,8 +34,8 @@ export const reserveStock = async (sku: string, quantity: number, requestId: str
   }
 
   return {
-    reservationToken: `res_${requestId}_${snapshot.snapshotVersion}`,
-    snapshotVersion: snapshot.snapshotVersion,
+    reservationToken: `res_${requestId}_${record.snapshotVersion}`,
+    snapshotVersion: record.snapshotVersion,
     availableAfter: record.available
   };
 };