embedded3 PERF-3 P1-5 (c) part 2 + (d): the device tables persist across steps and are updated in place within the band — one DeviceCut with both phases' aperture / open / activity buffers (the predictor phase is a flag); the faces of the changed cells for apertures, distances, shifts and open flags, the imposition band's faces for the surface velocities, the changed cells for activity and owner, the changed and wall cells for the wall flux, the merged-cell CSR whole; RTX_E3_BAND_CHECK=1 compares every table against a full build (passed); slab CSV byte-identical, device moving/cg green; ny 124 rebuild block 1,910 → 1,578 ms per step (tables 442 → 132)

Co-Authored-By: Claude Fable 5.1 <[email protected]>

crates/specialized/rtx-cfd/src/solvers/incompressible/embedded3/wall.rs

@@ -578,6 +578,12 @@ impl Mask {
             _ => None,
         }
     }
+    /// The space-time open flags per u / v / w face (a moving cut wall).
+    #[must_use]
+    pub fn step_open_flags(&self) -> Option<[&[bool]; 3]> {
+        self.step_open.as_ref().map(|o| [o.0.as_slice(), o.1.as_slice(), o.2.as_slice()])
+    }
+
     /// The cells whose operator rows may have changed since the previous
     /// step (P1-4), or `None` when every row must be rebuilt.
     #[must_use]