diff --git a/src/AcDream.Core/Physics/TransitionTypes.cs b/src/AcDream.Core/Physics/TransitionTypes.cs
index a2f5a5ce..9879e624 100644
--- a/src/AcDream.Core/Physics/TransitionTypes.cs
+++ b/src/AcDream.Core/Physics/TransitionTypes.cs
@@ -1070,18 +1070,33 @@ public sealed class Transition
                 }
                 else
                 {
-                    // Retail CSphere::slide_sphere — the full retail version
-                    // adjusts sphere position via add_offset_to_check_pos +
-                    // returns Adjusted (on success) or Collided (degenerate).
-                    // Our simpler response: record the collision normal +
-                    // return Collided. The outer engine sees Collided and
-                    // does NOT advance the sphere position — block achieved.
+                    // Retail neg_step_up==0 (HEAD-sphere near-miss) → CSphere::slide_sphere,
+                    // then the insert loop continues (re-tests at the slid position):
+                    // CTransition::transitional_insert, acclient_2013_pseudo_c.txt:273350-273351
+                    //   if (sphere_path.neg_step_up == 0)
+                    //     edi = CSphere::slide_sphere(global_sphere, sphere_path,
+                    //                                 collision_info, neg_collision_normal,
+                    //                                 global_curr_center);
                     //
-                    // A6.P4 door inside-out fix (2026-05-25): user-visible
-                    // blocking is the goal (retail behavior); the full
-                    // slide-position adjustment can be a later iteration.
-                    ci.SetCollisionNormal(sp.NegCollisionNormal);
-                    return TransitionState.Collided;
+                    // Earlier (A6.P4, 2026-05-25) this branch returned Collided as a
+                    // simplification so closed doors would block. But that hard stop
+                    // ALSO wedged a grounded mover whose HEAD sphere brushed a wall
+                    // while moving along it — e.g. exiting the Holtburg cottage cellar:
+                    // the body reached the cottage floor (Z=94) but oscillated against
+                    // the stairwell walls with no slide (2026-06-04 live capture, 16k
+                    // frames: 274 (0,-1,0) + 78 (1,0,0) hits, out==current). The
+                    // faithful slide_sphere slides tangentially along the wall (crease =
+                    // collisionNormal × contactPlane.Normal), which un-wedges the cellar
+                    // AND still blocks a closed door — the into-door (+Y) component is
+                    // removed and only the tangential X slide survives, so there is no
+                    // walkthrough.
+                    var slideRes = SlideSphereInternal(
+                        sp.NegCollisionNormal, sp.GlobalCurrCenter[0].Origin);
+                    if (slideRes == TransitionState.Collided)
+                        return TransitionState.Collided;   // degenerate slide → hard stop
+                    // Slid / Adjusted / OK → re-test at the (slid) CheckPos, mirroring
+                    // retail's insert-loop continuation after slide_sphere.
+                    continue;
                 }
             }