diff --git a/src/AcDream.Core/Physics/TransitionTypes.cs b/src/AcDream.Core/Physics/TransitionTypes.cs
index f2c4f6c..1a3a12f 100644
--- a/src/AcDream.Core/Physics/TransitionTypes.cs
+++ b/src/AcDream.Core/Physics/TransitionTypes.cs
@@ -1389,6 +1389,7 @@ public sealed class Transition
 
         var sp = SpherePath;
         var oi = ObjectInfo;
+        var ci = CollisionInfo;
 
         // #42 diagnostic (2026-05-05): identify which static object causes
         // the airborne first-frame ~1m push. Capture sphere check pos at
@@ -1460,6 +1461,14 @@ public sealed class Transition
             if (CollisionExemption.ShouldSkip(obj.State, obj.Flags, ObjectInfo.State))
                 continue;
 
+            // L.2a slice 3 (2026-05-12): snapshot collision-normal state so
+            // we can tell whether THIS object's BSP/CylSphere test produced a
+            // new collision (BSPQuery sets the normal but may still return OK
+            // for slide cases). Together with the `result != OK` check below
+            // this populates ci.CollideObjectGuids + LastCollidedObjectGuid so
+            // the [resolve] probe surfaces the responsible entity id.
+            bool collisionWasValidPre = ci.CollisionNormalValid;
+
             TransitionState result;
 
             if (obj.CollisionType == ShadowCollisionType.BSP)
@@ -1523,6 +1532,22 @@ public sealed class Transition
                 result = CylinderCollision(obj, sp);
             }
 
+            // L.2a slice 3: attribute the collision (if any) to this entity.
+            // Two cases:
+            //   - result != OK: the object stopped the transition (hard-block).
+            //   - result == OK but the normal flipped from invalid→valid during
+            //     this call: BSPQuery captured a slide normal without halting.
+            // Either way this object is responsible for the hit, so add its
+            // entity id. CollideObjectGuids carries the full chain; the last
+            // assignment to LastCollidedObjectGuid wins which matches retail's
+            // "most recent" semantics for the probe.
+            if (result != TransitionState.OK
+                || (!collisionWasValidPre && ci.CollisionNormalValid))
+            {
+                ci.CollideObjectGuids.Add(obj.EntityId);
+                ci.LastCollidedObjectGuid = obj.EntityId;
+            }
+
             if (result != TransitionState.OK)
             {
                 if (airborneDiag)