diff --git a/integration/test/Test/MLS/KeyPackage.hs b/integration/test/Test/MLS/KeyPackage.hs
index 7c58110921f..31d3a8641e9 100644
--- a/integration/test/Test/MLS/KeyPackage.hs
+++ b/integration/test/Test/MLS/KeyPackage.hs
@@ -9,6 +9,7 @@ import API.BrigInternal
 import MLS.Util
 import SetupHelpers
 import Testlib.Prelude
+import UnliftIO (pooledForConcurrentlyN)
 
 testDeleteKeyPackages :: App ()
 testDeleteKeyPackages = do
@@ -452,3 +453,37 @@ testReplaceKeyPackagesV7 = do
     testErrorCases (Just [suite]) altSuiteKeyPackages
     testErrorCases (Just [suite]) (oldSuiteKeyPackages <> altSuiteKeyPackages <> suiteKeyPackages)
     testErrorCases (Just [suite]) []
+
+testUploadClaim1000KeyPackages :: App ()
+testUploadClaim1000KeyPackages = do
+  let suite = def
+      keyPackageCount = 1000
+
+  alice <- randomUser OwnDomain def
+  alice1 <- createMLSClient def {ciphersuites = [suite]} alice
+
+  bob <- randomUser OwnDomain def
+  bob1 <- createMLSClient def {ciphersuites = [suite]} bob
+
+  -- Generate 1000 key packages in parallel (16 concurrent workers)
+  kps <- map fst <$> pooledForConcurrentlyN 16 [1 .. keyPackageCount] \_ -> do
+    generateKeyPackage alice1 suite
+
+  -- Upload all 1000 key packages in one batched call
+  void $ uploadKeyPackages alice1 kps >>= getBody 201
+
+  -- Verify count is 1000
+  bindResponse (countKeyPackages suite alice1) $ \resp -> do
+    resp.status `shouldMatchInt` 200
+    resp.json %. "count" `shouldMatchInt` keyPackageCount
+
+  -- Bob claims one key package from alice
+  bindResponse (claimKeyPackages suite bob1 alice) $ \resp -> do
+    resp.status `shouldMatchInt` 200
+    kpBundles <- resp.json %. "key_packages" & asList
+    length kpBundles `shouldMatchInt` 1
+
+  -- Verify count is now 999 (one claimed)
+  bindResponse (countKeyPackages suite alice1) $ \resp -> do
+    resp.status `shouldMatchInt` 200
+    resp.json %. "count" `shouldMatchInt` (keyPackageCount - 1)