diff --git a/Channel/Sources/EDOSocketChannel.m b/Channel/Sources/EDOSocketChannel.m
index 8ddf9c4..ea0be10 100644
--- a/Channel/Sources/EDOSocketChannel.m
+++ b/Channel/Sources/EDOSocketChannel.m
@@ -67,9 +67,16 @@ - (instancetype)initWithHandlerQueue:(dispatch_queue_t)handlerQueue {
   if (self) {
     // For internal IO and event handlers, it is equivalent to creating it as a serial queue as they
     // are not reentrant and only one block will be scheduled by dispatch io and dispatch source.
-    _handlerQueue =
-        handlerQueue
-            ?: dispatch_queue_create("com.google.edo.socketChannel.handler", DISPATCH_QUEUE_SERIAL);
+    if (handlerQueue) {
+      _handlerQueue = handlerQueue;
+    } else {
+      // Use QOS_CLASS_USER_INITIATED as the default because eDO communication is often in the
+      // critical path of user-driven test execution, and using a lower QoS can lead to priority
+      // inversion issues.
+      dispatch_queue_attr_t attributes = dispatch_queue_attr_make_with_qos_class(
+          DISPATCH_QUEUE_SERIAL, QOS_CLASS_USER_INITIATED, 0);
+      _handlerQueue = dispatch_queue_create("com.google.edo.socketChannel.handler", attributes);
+    }
   }
   return self;
 }
diff --git a/Service/Tests/FunctionalTests/EDOServiceUIBlockTest.m b/Service/Tests/FunctionalTests/EDOServiceUIBlockTest.m
index de40fab..16de740 100644
--- a/Service/Tests/FunctionalTests/EDOServiceUIBlockTest.m
+++ b/Service/Tests/FunctionalTests/EDOServiceUIBlockTest.m
@@ -156,7 +156,7 @@ - (void)testBlockResolveToLocalAddress {
 
   // Sending block to remote process through background eDO host.
   dispatch_sync(backgroundQueue, ^{
-    pthread_set_qos_class_self_np(QOS_CLASS_DEFAULT, 0);
+    pthread_set_qos_class_self_np(QOS_CLASS_USER_INITIATED, 0);
     remoteDummy.block = localBlock;
   });
 
diff --git a/Service/Tests/FunctionalTests/EDOServiceUITest.m b/Service/Tests/FunctionalTests/EDOServiceUITest.m
index afafab4..ce1388b 100644
--- a/Service/Tests/FunctionalTests/EDOServiceUITest.m
+++ b/Service/Tests/FunctionalTests/EDOServiceUITest.m
@@ -226,7 +226,7 @@ - (void)testTemporaryServiceHandlesRecursiveCall {
   EDOTestDummy *remoteDummy = [EDOClientService rootObjectWithPort:EDOTEST_APP_SERVICE_PORT];
   // Align QoS with eDO internal threads to avoid priority inversion.
   dispatch_queue_attr_t attr =
-      dispatch_queue_attr_make_with_qos_class(DISPATCH_QUEUE_SERIAL, QOS_CLASS_DEFAULT, 0);
+      dispatch_queue_attr_make_with_qos_class(DISPATCH_QUEUE_SERIAL, QOS_CLASS_USER_INITIATED, 0);
   dispatch_queue_t testQueue = dispatch_queue_create("com.google.edotest", attr);
 
   XCTestExpectation *expectation = [self expectationWithDescription:@"recursive call completes."];