diff --git a/.gitignore b/.gitignore
index 4df2626..cbcbae1 100644
--- a/.gitignore
+++ b/.gitignore
@@ -10,3 +10,4 @@ demo_render/
 CLAUDE.md
 .claude/
 .agents/
+skyseg.onnx
\ No newline at end of file
diff --git a/README.md b/README.md
index cc78637..b507a28 100644
--- a/README.md
+++ b/README.md
@@ -115,13 +115,30 @@ python demo.py --model_path /path/to/checkpoint.pt \
 ```
 
 
-### With Sky Masking
+### Sky Masking
+
+Sky masking uses an ONNX sky segmentation model to filter out sky points from the reconstructed point cloud, which improves visualization quality for outdoor scenes.
+
+**Setup:**
+
+```bash
+# Install onnxruntime (required)
+pip install onnxruntime        # CPU
+# or
+pip install onnxruntime-gpu    # GPU (faster for large image sets)
+```
+
+The sky segmentation model (`skyseg.onnx`) will be automatically downloaded from [HuggingFace](https://huggingface.co/JianyuanWang/skyseg/resolve/main/skyseg.onnx) on first use.
+
+**Usage:**
 
 ```bash
 python demo.py --model_path /path/to/checkpoint.pt \
     --image_folder /path/to/images/ --mask_sky
 ```
 
+Sky masks are cached in `<image_folder>_sky_masks/` so subsequent runs skip regeneration.
+
 ### Without FlashInfer (SDPA fallback)
 
 ```bash
diff --git a/demo.py b/demo.py
index 338321e..14dbe44 100644
--- a/demo.py
+++ b/demo.py
@@ -138,9 +138,8 @@ _BATCHED_NDIMS = {
     "world_points_conf": 4,
     "extrinsic": 4,
     "intrinsic": 4,
-    "chunk_sim3_scales": 2,
-    "chunk_sim3_poses": 4,
-    "chunk_se3_poses": 4,
+    "chunk_scales": 2,
+    "chunk_transforms": 4,
     "images": 5,
 }
 
@@ -256,14 +255,13 @@ def main():
     # Windowed options
     parser.add_argument("--window_size", type=int, default=64, help="Frames per window (windowed mode)")
     parser.add_argument("--overlap_size", type=int, default=16, help="Overlap between windows")
-    parser.add_argument("--sim3", action="store_true", default=True, help="Use Sim(3) alignment between windows")
-    parser.add_argument("--no_sim3", dest="sim3", action="store_false", help="Disable Sim(3), use SE(3) instead")
+
 
     # Visualization
     parser.add_argument("--port", type=int, default=8080)
-    parser.add_argument("--conf_threshold", type=float, default=1.0)
+    parser.add_argument("--conf_threshold", type=float, default=1.5)
     parser.add_argument("--downsample_factor", type=int, default=10)
-    parser.add_argument("--point_size", type=float, default=0.005)
+    parser.add_argument("--point_size", type=float, default=0.0007)
     parser.add_argument("--mask_sky", action="store_true", help="Apply sky segmentation to filter out sky points")
 
     args = parser.parse_args()
@@ -314,8 +312,6 @@ def main():
                 window_size=args.window_size,
                 overlap_size=args.overlap_size,
                 num_scale_frames=args.num_scale_frames,
-                sim3=args.sim3,
-                se3=not args.sim3,
             )
 
     t_infer = time.time() - t0
@@ -330,7 +326,7 @@ def main():
         viewer = PointCloudViewer(
             pred_dict=prepare_for_visualization(predictions, images_cpu),
             port=args.port,
-            init_conf_threshold=args.conf_threshold,
+            vis_threshold=args.conf_threshold,
             downsample_factor=args.downsample_factor,
             point_size=args.point_size,
             mask_sky=args.mask_sky,
diff --git a/lingbot_map/layers/flashinfer_cache.py b/lingbot_map/layers/flashinfer_cache.py
index 1660f97..d8e7b13 100644
--- a/lingbot_map/layers/flashinfer_cache.py
+++ b/lingbot_map/layers/flashinfer_cache.py
@@ -169,6 +169,11 @@ class FlashInferKVCacheManager:
         # Frame counter per block (determines scale vs window routing)
         self.frame_count: List[int] = [0] * num_blocks
 
+        # Deferred eviction support for flow-based keyframe selection.
+        # When True, evict_frames() becomes a no-op; caller must later call
+        # execute_deferred_eviction() or rollback_last_frame().
+        self._defer_eviction: bool = False
+
         # ── FlashInfer wrapper ───────────────────────────────────────────────
         # plan() is called once per frame step (block_idx == 0).
         # run() is called per layer, reusing the same aux structures.
@@ -237,11 +242,64 @@ class FlashInferKVCacheManager:
         Special pages are NEVER evicted.
         Scale pages are NEVER evicted.
         Only live_window_patch_pages beyond `sliding_window` are recycled.
+
+        When ``_defer_eviction`` is True, this method is a no-op.  The caller
+        is expected to later call ``execute_deferred_eviction()`` (keep frame)
+        or ``rollback_last_frame()`` (discard frame).
         """
+        if self._defer_eviction:
+            return
         while len(self.live_window_patch_pages[block_idx]) > sliding_window:
             old_page = self.live_window_patch_pages[block_idx].popleft()
             self.free_patch_pages[block_idx].append(old_page)
 
+    def execute_deferred_eviction(
+        self,
+        block_idx: int,
+        scale_frames: int,
+        sliding_window: int,
+        **kwargs,
+    ) -> None:
+        """Run the eviction that was skipped while ``_defer_eviction`` was True."""
+        while len(self.live_window_patch_pages[block_idx]) > sliding_window:
+            old_page = self.live_window_patch_pages[block_idx].popleft()
+            self.free_patch_pages[block_idx].append(old_page)
+
+    def rollback_last_frame(self, block_idx: int) -> None:
+        """Undo the most recent ``append_frame()`` for *block_idx*.
+
+        This reverses all three sub-operations of ``append_frame``:
+        patch page allocation, special-token write, and frame_count increment.
+        It must be called **before** any eviction for that frame (i.e. while
+        ``_defer_eviction`` is True or before ``evict_frames`` is called).
+        """
+        assert self.frame_count[block_idx] > 0, (
+            f"block {block_idx}: cannot rollback, frame_count is 0"
+        )
+
+        # 1) Undo patch page ── pop from whichever deque it was routed to.
+        if self.frame_count[block_idx] > self.scale_frames:
+            page_id = self.live_window_patch_pages[block_idx].pop()
+        else:
+            page_id = self.scale_patch_pages[block_idx].pop()
+        self.free_patch_pages[block_idx].append(page_id)
+
+        # 2) Undo special tokens
+        n = self.num_special_tokens
+        new_count = self.special_token_count[block_idx] - n
+        assert new_count >= 0, (
+            f"block {block_idx}: special_token_count underflow "
+            f"({self.special_token_count[block_idx]} - {n})"
+        )
+        new_num_pages = math.ceil(new_count / self.page_size) if new_count > 0 else 0
+        while len(self.all_special_pages[block_idx]) > new_num_pages:
+            freed = self.all_special_pages[block_idx].pop()
+            self.free_special_pages[block_idx].append(freed)
+        self.special_token_count[block_idx] = new_count
+
+        # 3) Decrement frame count
+        self.frame_count[block_idx] -= 1
+
     def _gather_kv(self, block_idx: int):
         """
         Gather all visible K and V tokens from the paged cache into dense tensors.
diff --git a/lingbot_map/vis/point_cloud_viewer.py b/lingbot_map/vis/point_cloud_viewer.py
index b90f281..ed19434 100644
--- a/lingbot_map/vis/point_cloud_viewer.py
+++ b/lingbot_map/vis/point_cloud_viewer.py
@@ -1486,7 +1486,7 @@ class PointCloudViewer:
             aspect=aspect,
             wxyz=q,
             position=t,
-            scale=0.1,
+            scale=0.03,
             color=camera_color_rgb,
         )