diff --git a/Source/Mods/QualityBuilder.cs b/Source/Mods/QualityBuilder.cs
index f54646b..49fc206 100644
--- a/Source/Mods/QualityBuilder.cs
+++ b/Source/Mods/QualityBuilder.cs
@@ -1,4 +1,4 @@
-using System;
+using System;
 using HarmonyLib;
 using Multiplayer.API;
 using Verse;
@@ -12,27 +12,72 @@ namespace Multiplayer.Compat
     [MpCompatFor("hatti.qualitybuilder")]
     class QualityBuilder
     {
+        // The skilled-builder designator remembers the min-quality the player picked from its
+        // right-click menu in an instance field (curQualityCat). This ref lets us serialize that
+        // choice so a designation resolves to the same quality on every client.
+        private static AccessTools.FieldRef<Designator, QualityCategory?> desiredQualityField;
+
         public QualityBuilder(ModContentPack mod)
         {
-            Type builderCompType = AccessTools.TypeByName("QualityBuilder.CompQualityBuilder");
-            Type toggleCommandType = AccessTools.TypeByName("QualityBuilder.CompQualityBuilder+ToggleCommand+<>c");
-            Type designatorType = AccessTools.TypeByName("QualityBuilder._Designator_SkilledBuilder+<>c");
-
             Type[] argTypes = { typeof(QualityCategory) };
 
-            MethodInfo toggleCommandMethod = MpMethodUtil.GetFirstMethodBySignature(toggleCommandType, argTypes);
-            MethodInfo designatorMethod = MpMethodUtil.GetFirstMethodBySignature(designatorType, argTypes);
+            // --- "Skilled" toggle gizmo on the building comp ---
+            Type builderCompType = AccessTools.TypeByName("QualityBuilder.CompQualityBuilder");
+            if (builderCompType != null)
+                MP.RegisterSyncMethod(builderCompType, "ToggleSkilled");
 
-            //my decompiler shows the method name is <get_RightClickFloatMenuOptions>b__3_0 
-            //while harmony saids it is <get_RightClickFloatMenuOptions>b__2_0, weird..."
+            // The gizmo's right-click "set min quality" lambda is non-capturing, so it still lives in a
+            // cached <>c closure. Match it by signature rather than by a brittle lambda ordinal.
+            Type toggleCommandType = AccessTools.TypeByName("QualityBuilder.CompQualityBuilder+ToggleCommand+<>c");
+            MethodInfo toggleCommandMethod = toggleCommandType != null
+                ? MpMethodUtil.GetFirstMethodBySignature(toggleCommandType, argTypes)
+                : null;
+            if (toggleCommandMethod != null)
+            {
+                MP.RegisterSyncWorker<object>(SyncTypes, toggleCommandType);
+                MP.RegisterSyncMethod(toggleCommandMethod).SetContext(SyncContext.MapSelected);
+            }
+            else
+            {
+                Log.Warning("MPCompat :: QualityBuilder: couldn't resolve the ToggleCommand right-click sync method; the min-quality gizmo menu won't be synced.");
+            }
 
-            MP.RegisterSyncWorker<object>(SyncTypes, toggleCommandType);
-            MP.RegisterSyncWorker<object>(SyncTypes, designatorType);
+            // --- "Skilled builder" designator (right-click min-quality choice) ---
+            // Previously this synced the choice-setting lambda through its <>c closure. QualityBuilder made
+            // curQualityCat a non-static (per-instance) field, so that lambda now captures 'this' and the
+            // <>c closure no longer exists -- looking it up returned null and NRE'd the whole patch. Instead,
+            // sync the designator's state directly: MP replays the designation with this worker, so every
+            // client resolves the same desired quality. This mirrors how other modded designators are synced
+            // (e.g. Dubs Bad Hygiene) and is robust to that closure refactor.
+            Type designatorType = AccessTools.TypeByName("QualityBuilder._Designator_SkilledBuilder");
+            if (designatorType != null)
+            {
+                desiredQualityField = AccessTools.FieldRefAccess<QualityCategory?>(designatorType, "curQualityCat");
+                MP.RegisterSyncWorker<Designator>(SyncSkilledDesignator, designatorType, shouldConstruct: true);
+            }
+            else
+            {
+                Log.Warning("MPCompat :: QualityBuilder: couldn't find _Designator_SkilledBuilder; its designations won't be synced.");
+            }
+        }
 
-            MP.RegisterSyncMethod(builderCompType, "ToggleSkilled");
-            MP.RegisterSyncMethod(toggleCommandMethod).SetContext(SyncContext.MapSelected);
-            MP.RegisterSyncMethod(designatorMethod);
-        
+        // Serializes the skilled-builder designator's chosen min quality (a nullable QualityCategory).
+        // The designator is freshly constructed (shouldConstruct: true), so curQualityCat starts null;
+        // only overwrite it when the writer actually had a value.
+        private static void SyncSkilledDesignator(SyncWorker sync, ref Designator designator)
+        {
+            if (sync.isWriting)
+            {
+                QualityCategory? chosen = desiredQualityField(designator);
+                sync.Write(chosen.HasValue);
+                if (chosen.HasValue)
+                    sync.Write(chosen.Value);
+            }
+            else
+            {
+                if (sync.Read<bool>())
+                    desiredQualityField(designator) = sync.Read<QualityCategory>();
+            }
         }
 
         void SyncTypes(SyncWorker sync, ref object c)