From aa841d58a82896d8e3bbad4bcb4882b8382550e7 Mon Sep 17 00:00:00 2001
From: Ciaran Harvey <ciaran.harvey@red-gate.com>
Date: Tue, 3 Mar 2026 16:53:36 +0000
Subject: [PATCH 1/3] Add failing test for inline continuation deadlock

---
 .../Controller/ScheduledTaskExecutorTests.cs  | 21 +++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/test/Polly.Core.Tests/CircuitBreaker/Controller/ScheduledTaskExecutorTests.cs b/test/Polly.Core.Tests/CircuitBreaker/Controller/ScheduledTaskExecutorTests.cs
index 27c854ab40d..8527e0de3ce 100644
--- a/test/Polly.Core.Tests/CircuitBreaker/Controller/ScheduledTaskExecutorTests.cs
+++ b/test/Polly.Core.Tests/CircuitBreaker/Controller/ScheduledTaskExecutorTests.cs
@@ -129,6 +129,27 @@ public void Dispose_WhenScheduledTaskExecuting()
 #pragma warning restore xUnit1031
     }
 
+    [Fact]
+    public void ScheduleTask_InlineContinuationDoesNotDeadlock()
+    {
+        var timeout = TimeSpan.FromMilliseconds(250);
+        using var scheduler = new ScheduledTaskExecutor();
+
+        var firstTask = scheduler.ScheduleTask(() => Task.CompletedTask);
+
+        var continuationTask = firstTask.ContinueWith(
+            _ =>
+            {
+                var secondTask = scheduler.ScheduleTask(() => Task.CompletedTask);
+                secondTask.Wait(timeout);
+            },
+            CancellationToken.None,
+            TaskContinuationOptions.ExecuteSynchronously,
+            TaskScheduler.Default);
+
+        continuationTask.Wait(timeout).ShouldBeTrue();
+    }
+
     [Fact]
     public async Task Dispose_EnsureNoBackgroundProcessing()
     {

From e71c0b792b510a33c5ffd0c15a75e71cbb3c6d42 Mon Sep 17 00:00:00 2001
From: Ciaran Harvey <ciaran.harvey@red-gate.com>
Date: Tue, 3 Mar 2026 16:54:05 +0000
Subject: [PATCH 2/3] Make sure we run task continuations async

---
 .../CircuitBreaker/Controller/ScheduledTaskExecutor.cs          | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/Polly.Core/CircuitBreaker/Controller/ScheduledTaskExecutor.cs b/src/Polly.Core/CircuitBreaker/Controller/ScheduledTaskExecutor.cs
index f23e450e7cd..1fdfeea4d65 100644
--- a/src/Polly.Core/CircuitBreaker/Controller/ScheduledTaskExecutor.cs
+++ b/src/Polly.Core/CircuitBreaker/Controller/ScheduledTaskExecutor.cs
@@ -26,7 +26,7 @@ public Task ScheduleTask(Func<Task> taskFactory)
         }
 #endif
 
-        var source = new TaskCompletionSource<object>();
+        var source = new TaskCompletionSource<object>(TaskCreationOptions.RunContinuationsAsynchronously);
 
         _tasks.Enqueue(new Entry(taskFactory, source));
         _semaphore.Release();

From 7e93bafe9983684189a8bfcc18bad9f04d1fae7d Mon Sep 17 00:00:00 2001
From: Ciaran Harvey <ciaran.harvey@red-gate.com>
Date: Tue, 3 Mar 2026 18:21:10 +0000
Subject: [PATCH 3/3] Use the xunit test cancellation token

---
 .../CircuitBreaker/Controller/ScheduledTaskExecutorTests.cs     | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/test/Polly.Core.Tests/CircuitBreaker/Controller/ScheduledTaskExecutorTests.cs b/test/Polly.Core.Tests/CircuitBreaker/Controller/ScheduledTaskExecutorTests.cs
index 8527e0de3ce..58e7faf1fd4 100644
--- a/test/Polly.Core.Tests/CircuitBreaker/Controller/ScheduledTaskExecutorTests.cs
+++ b/test/Polly.Core.Tests/CircuitBreaker/Controller/ScheduledTaskExecutorTests.cs
@@ -143,7 +143,7 @@ public void ScheduleTask_InlineContinuationDoesNotDeadlock()
                 var secondTask = scheduler.ScheduleTask(() => Task.CompletedTask);
                 secondTask.Wait(timeout);
             },
-            CancellationToken.None,
+            CancellationToken,
             TaskContinuationOptions.ExecuteSynchronously,
             TaskScheduler.Default);