diff --git a/docs/superpowers/specs/2026-05-29-a8f-camera-collision-design.md b/docs/superpowers/specs/2026-05-29-a8f-camera-collision-design.md
index 0cc1a21..269aa55 100644
--- a/docs/superpowers/specs/2026-05-29-a8f-camera-collision-design.md
+++ b/docs/superpowers/specs/2026-05-29-a8f-camera-collision-design.md
@@ -144,9 +144,13 @@ public Vector3 SweepEye(Vector3 pivot, Vector3 desiredEye, uint cellId, uint sel
         stepDownHeight: 0f,          // no step-down / ground snap
         isOnGround:     false,       // no contact-plane / walkable semantics
         body:           null,        // no cross-frame contact-plane persistence
-        moverFlags:     ObjectInfoState.None,  // all targets collide; also keeps
-                                               // camera sweeps out of the #98
-                                               // IsPlayer capture filter
+        // Retail init_object(player, 0x5c) = IsViewer|PathClipped|FreeRotate|
+        // PerfectClip (pseudo-C :92864). PathClipped = hard-stop at first contact
+        // (the spring arm, not edge-slide); IsViewer = eye passes through creatures,
+        // colliding only with world geometry. Not IsPlayer → stays out of the #98
+        // capture filter.
+        moverFlags:     ObjectInfoState.IsViewer | ObjectInfoState.PathClipped
+                      | ObjectInfoState.FreeRotate | ObjectInfoState.PerfectClip,
         movingEntityId: selfEntityId);         // skip the player's own ShadowEntry
     return r.Position + zoff;        // r.Position = sp.CheckPos (path pt); + zoff = eye
 }
@@ -264,11 +268,13 @@ Compare `ACDREAM_CAMERA_COLLIDE=0` vs default to confirm the flag isolates the f
 
 ## 11. Open implementation questions (decide during the plan, not now)
 
-1. **Slide vs hard-stop.** Reusing `ResolveWithTransition` gives the player
-   path's edge-slide (the eye glides along a wall rather than jittering). Read
-   retail's `find_valid_position` during implementation and confirm whether it
-   slides or hard-stops; match it. Both keep the eye out of walls, so this does
-   not change the architecture.
+1. **Slide vs hard-stop — RESOLVED (hard-stop).** Retail's `update_viewer` calls
+   `init_object(player, 0x5c)`, and `0x5c` includes `PathClipped`, which makes the
+   transition HARD-STOP at first contact (`TransitionTypes.cs:811`) rather than
+   edge-slide. The probe therefore passes
+   `IsViewer | PathClipped | FreeRotate | PerfectClip` (see §5.1). Hard-stop also
+   avoids the eye sliding around a corner into the next room, which would re-trigger
+   the A8.F camera-cell instability this fix targets.
 2. **`sphereHeight: 0f` — RESOLVED.** `SpherePath.InitPath` with height 0 yields a
    single sphere (`NumSphere = 1`, `TransitionTypes.cs:534-537`). It also offsets
    sphere0's center to `pathPos + (0,0,radius)` (foot-capsule convention) whereas
diff --git a/src/AcDream.App/Rendering/PhysicsCameraCollisionProbe.cs b/src/AcDream.App/Rendering/PhysicsCameraCollisionProbe.cs
index 09ce5c1..a5e9e89 100644
--- a/src/AcDream.App/Rendering/PhysicsCameraCollisionProbe.cs
+++ b/src/AcDream.App/Rendering/PhysicsCameraCollisionProbe.cs
@@ -43,9 +43,17 @@ public sealed class PhysicsCameraCollisionProbe : ICameraCollisionProbe
             stepDownHeight: 0f,                    // no step-down / ground snap
             isOnGround:     false,                 // no contact-plane / walkable semantics
             body:           null,                  // no cross-frame persistence
-            moverFlags:     ObjectInfoState.None,  // all targets collide; also keeps
-                                                   // camera sweeps out of the #98
-                                                   // IsPlayer capture filter
+            // Retail SmartBox::update_viewer calls init_object(player, 0x5c) =
+            // IsViewer | PathClipped | FreeRotate | PerfectClip (acclient
+            // pseudo-C :92864; enum TransitionTypes.cs:24-33). PathClipped makes
+            // the sweep HARD-STOP at first contact (TransitionTypes.cs:811) — the
+            // spring-arm pull-in, not the player's edge-slide. IsViewer lets the
+            // eye pass through creatures, colliding only with world geometry
+            // (CollisionExemption.cs:83-85). FreeRotate/PerfectClip are no-ops in
+            // acdream today but set to match retail's exact value. NOT IsPlayer
+            // (0x100), so camera sweeps stay out of the #98 capture filter.
+            moverFlags:     ObjectInfoState.IsViewer | ObjectInfoState.PathClipped
+                          | ObjectInfoState.FreeRotate | ObjectInfoState.PerfectClip,
             movingEntityId: selfEntityId);         // skip the player's own ShadowEntry
 
         return FromSpherePath(r.Position, ViewerSphereRadius);
diff --git a/tests/AcDream.Core.Tests/Rendering/CameraDiagnosticsTests.cs b/tests/AcDream.Core.Tests/Rendering/CameraDiagnosticsTests.cs
index d89d1ad..b27c81c 100644
--- a/tests/AcDream.Core.Tests/Rendering/CameraDiagnosticsTests.cs
+++ b/tests/AcDream.Core.Tests/Rendering/CameraDiagnosticsTests.cs
@@ -21,6 +21,7 @@ public class CameraDiagnosticsTests
         CameraDiagnostics.CameraAdjustmentSpeed = 40.0f;
         CameraDiagnostics.AlignToSlope          = true;
         CameraDiagnostics.UseRetailChaseCamera  = true;
+        CameraDiagnostics.CollideCamera         = true;
 
         Assert.Equal(0.45f, CameraDiagnostics.TranslationStiffness);
         Assert.Equal(0.45f, CameraDiagnostics.RotationStiffness);
@@ -31,6 +32,7 @@ public class CameraDiagnosticsTests
         // legacy camera remains opt-in via the DebugPanel toggle until
         // the follow-up deletion commit.
         Assert.True(CameraDiagnostics.UseRetailChaseCamera);
+        Assert.True(CameraDiagnostics.CollideCamera);
     }
 
     [Fact]