From b691663e2fbb62ea864c9788a18f7547c8001002 Mon Sep 17 00:00:00 2001
From: deltanedas <@deltanedas:goida.zip>
Date: Tue, 25 Aug 2026 06:25:26 +0100
Subject: [PATCH 1/2] make BoundUserInterfaceMessageAttempt by ref struct

---
 .../UserInterface/UserInterfaceComponent.cs   | 27 ++++++++++---------
 .../Systems/SharedUserInterfaceSystem.cs      |  4 +--
 2 files changed, 17 insertions(+), 14 deletions(-)

diff --git a/Robust.Shared/GameObjects/Components/UserInterface/UserInterfaceComponent.cs b/Robust.Shared/GameObjects/Components/UserInterface/UserInterfaceComponent.cs
index df823bd550f..7a739bffd0c 100644
--- a/Robust.Shared/GameObjects/Components/UserInterface/UserInterfaceComponent.cs
+++ b/Robust.Shared/GameObjects/Components/UserInterface/UserInterfaceComponent.cs
@@ -144,20 +144,23 @@ public InterfaceData(InterfaceData data)
     }
 
     /// <summary>
-    ///     Raised whenever the server receives a BUI message from a client relating to a UI that requires input
-    ///     validation.
+    /// Raised whenever the server receives a BUI message from a client relating to a UI that requires input validation.
+    /// This is first broadcast then, if not cancelled already, raised directly on the BUI's owner.
     /// </summary>
-    public sealed class BoundUserInterfaceMessageAttempt(
-        EntityUid actor,
-        EntityUid target,
-        Enum uiKey,
-        BoundUserInterfaceMessage message)
-        : CancellableEntityEventArgs
+    [ByRefEvent]
+    public record struct BoundUserInterfaceMessageAttempt(EntityUid Actor, EntityUid Target, Enum UiKey, BoundUserInterfaceMessage Message)
     {
-        public readonly EntityUid Actor = actor;
-        public readonly EntityUid Target = target;
-        public readonly Enum UiKey = uiKey;
-        public readonly BoundUserInterfaceMessage Message = message;
+        public bool Cancelled { get; private set; }
+
+        public void Cancel()
+        {
+            Cancelled = true;
+        }
+
+        public void Uncancel()
+        {
+            Cancelled = false;
+        }
     }
 
     /// <summary>
diff --git a/Robust.Shared/GameObjects/Systems/SharedUserInterfaceSystem.cs b/Robust.Shared/GameObjects/Systems/SharedUserInterfaceSystem.cs
index d1a4d829669..95e89e59ecc 100644
--- a/Robust.Shared/GameObjects/Systems/SharedUserInterfaceSystem.cs
+++ b/Robust.Shared/GameObjects/Systems/SharedUserInterfaceSystem.cs
@@ -123,11 +123,11 @@ private void OnMessageReceived(BoundUIWrapMessage msg, EntityUid sender)
         {
             var attempt = new BoundUserInterfaceMessageAttempt(sender, uid, msg.UiKey, msg.Message);
 
-            RaiseLocalEvent(attempt);
+            RaiseLocalEvent(ref attempt);
             if (attempt.Cancelled)
                 return;
 
-            RaiseLocalEvent(uid, attempt);
+            RaiseLocalEvent(uid, ref attempt);
             if (attempt.Cancelled)
                 return;
         }

From fc62f8b92b13075e79a5a00775c0ea0a9953f1c5 Mon Sep 17 00:00:00 2001
From: deltanedas <@deltanedas:goida.zip>
Date: Tue, 25 Aug 2026 06:25:34 +0100
Subject: [PATCH 2/2] update release notes

---
 RELEASE-NOTES.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/RELEASE-NOTES.md b/RELEASE-NOTES.md
index a261504b8c9..48d40615989 100644
--- a/RELEASE-NOTES.md
+++ b/RELEASE-NOTES.md
@@ -35,7 +35,7 @@ END TEMPLATE-->
 
 ### Breaking changes
 
-*None yet*
+* `BoundUserInterfaceMessageAttempt` is now a by-ref struct. It can no longer be assigned to `CancellableEntityEventArgs`.
 
 ### New features