HttpTimeoutPolicy: Fixes aggressive 500ms first-attempt timeout in HttpTimeoutPolicyControlPlaneRetriableHotPath

Microsoft.Azure.Cosmos/src/HttpClient/HttpTimeoutPolicyControlPlaneRetriableHotPath.cs

@@ -20,9 +20,14 @@ private HttpTimeoutPolicyControlPlaneRetriableHotPath(bool shouldThrow503OnTimeo
             this.shouldThrow503OnTimeout = shouldThrow503OnTimeout;
         }
 
+        // The first-attempt timeout was raised from 500ms to 1s to align with HttpTimeoutPolicyForThinClient
+        // (see issue #5642). The original 500ms value caused spurious TaskCanceledException retries on
+        // .NET 10 due to changes in HttpConnectionPool behavior and any environment with moderate network
+        // latency. The 5s and 65s tail attempts are preserved to keep the existing retry budget for slow
+        // control-plane operations.
         private readonly IReadOnlyList<(TimeSpan requestTimeout, TimeSpan delayForNextRequest)> TimeoutsAndDelays = new List<(TimeSpan requestTimeout, TimeSpan delayForNextRequest)>()
         {
-            (TimeSpan.FromSeconds(.5), TimeSpan.Zero),
+            (TimeSpan.FromSeconds(1), TimeSpan.Zero),
             (TimeSpan.FromSeconds(5), TimeSpan.FromSeconds(1)),
             (TimeSpan.FromSeconds(65), TimeSpan.Zero),
         };

Microsoft.Azure.Cosmos/tests/Microsoft.Azure.Cosmos.Tests/CosmosHttpClientCoreTests.cs

@@ -75,7 +75,7 @@ public async Task RetryTransientIssuesTestAsync()
                 }},
                 {HttpTimeoutPolicyControlPlaneRetriableHotPath.Instance,  new List<TimeSpan>()
                 {
-                    TimeSpan.FromSeconds(1),
+                    TimeSpan.FromSeconds(2),
                     TimeSpan.FromSeconds(6),
                     TimeSpan.FromSeconds(66)
                 }},