diff --git a/crates/engine/src/cmd/patterns_tests.rs b/crates/engine/src/cmd/patterns_tests.rs
index ee9e7e38..94083c1d 100644
--- a/crates/engine/src/cmd/patterns_tests.rs
+++ b/crates/engine/src/cmd/patterns_tests.rs
@@ -402,3 +402,31 @@ fn pattern_of_touching_cuts_needs_no_fallback() {
         assert_eq!(m["bodies"][0][k], single["bodies"][0][k], "{k}");
     }
 }
+
+/// A pattern of cuts beside a round, on a bar whose long top edges are rounded, takes the exact
+/// planar route for every copy rather than the general boolean's retries: the teeth touch side
+/// by side and never reach the rounds (#1197). Retries and volume, not timing (see
+/// `scales_linearly`).
+#[test]
+fn pattern_of_cuts_beside_a_round_needs_no_retries() {
+    let mut s = Session::default();
+    run(&mut s, "solid.box", json!({"corner": [-10, 0, 0], "length": 20, "width": 200, "height": 4, "name": "Bar"}));
+    run(&mut s, "solid.fillet", json!({"edges": [[-10, 100, 4], [10, 100, 4]], "radius": 1}));
+    run(&mut s, "sketch.create", json!({"plane": "YZ", "name": "Tooth"}));
+    run(&mut s, "sketch.line", json!({"points": [[20, 4], [24, 2], [24, 5], [20, 5]], "closed": true}));
+    run(&mut s, "sketch.finish", json!({}));
+    let cut =
+        run(&mut s, "solid.extrude", json!({"sketch": "Tooth", "distance": 16, "direction": "symmetric", "operation": "cut", "name": "Tooth cut"}));
+    let teeth =
+        run(&mut s, "solid.pattern.rectangular", json!({"features": ["Tooth cut"], "dir1": [0, 1, 0], "count1": 40, "spacing1": 4, "name": "Teeth"}));
+    for created in [&cut, &teeth] {
+        let id = created["feature"].as_u64().unwrap();
+        let result = s.model.result(id).unwrap();
+        assert!(result.error.is_none() && result.warning.is_none(), "{result:?}");
+        assert!(result.boolean_diagnostics.events.is_empty(), "{:?}", result.boolean_diagnostics);
+    }
+    // The bar, less the rounds' corners and 40 teeth (a 4 x 2 triangle below the top, 16 wide).
+    let expected = 16000.0 - 400.0 * (1.0 - PI / 4.0) - 40.0 * 4.0 * 16.0;
+    let v = volume(&mut s);
+    assert!(rel(v, expected) < 1e-5, "{v} vs {expected}");
+}
diff --git a/crates/kernel/src/ops.rs b/crates/kernel/src/ops.rs
index 8a5fdca3..b839dec4 100644
--- a/crates/kernel/src/ops.rs
+++ b/crates/kernel/src/ops.rs
@@ -733,6 +733,19 @@ fn boolean_whole(a: &Body, b: &Body, op: BoolOp) -> Result<Option<Body>> {
         None
     };
     for (attempt, j) in JITTER.iter().enumerate() {
+        // The operands as they lie failed. A planar tool beside the target's curved faces (a tooth
+        // or a pocket cut next to a round edge) is decided exactly in the slab it lies in, where
+        // the target is planar too, before the shifted tries: that is where they end anyway, as a
+        // retry, after costing several times as much (on every copy of a pattern, #1197).
+        if attempt == 1 && matches!(op, BoolOp::Cut | BoolOp::Intersect) {
+            let (sliced, diagnostics) = capture_boolean_diagnostics(|| crate::polybool::sliced_planar_boolean(a, b, op));
+            if let Some(Ok(Some(body))) = sliced
+                && check(&body).0
+            {
+                merge(diagnostics);
+                return Ok(Some(body));
+            }
+        }
         let shift = mt::Vector3::new(j[0], j[1], j[2]) * (size * 0.01);
         for k in [2e-3, 5e-4] {
             let tol = (size * k).max(1e-5);
diff --git a/crates/kernel/src/polybool.rs b/crates/kernel/src/polybool.rs
index e9c376f8..970205dc 100644
--- a/crates/kernel/src/polybool.rs
+++ b/crates/kernel/src/polybool.rs
@@ -431,7 +431,7 @@ pub fn planar_boolean(a: &Body, b: &Body, op: BoolOp) -> Result<Option<Body>> {
 /// two parallel planes holds `b` and none of `a`'s curved faces (a pocket cut beside a round
 /// hole): `a` is split across the slab, the middle piece takes the exact boolean, and the
 /// pieces outside are joined back on. `None` when no such slab exists.
-fn sliced_planar_boolean(a: &Body, b: &Body, op: BoolOp) -> Option<Result<Option<Body>>> {
+pub(crate) fn sliced_planar_boolean(a: &Body, b: &Body, op: BoolOp) -> Option<Result<Option<Body>>> {
     let pb = planar_polys(b, 1).ok()?;
     let size = a.size().max(b.size());
     let tol = (a.size() * 1e-3).max(1e-3);
@@ -447,6 +447,10 @@ fn sliced_planar_boolean(a: &Body, b: &Body, op: BoolOp) -> Option<Result<Option
             bx.add(p);
         }
     }
+    // All planar: the exact boolean itself, not this.
+    if curved.is_empty() {
+        return None;
+    }
     let mut tool = solidcraft_geom::Aabb3::EMPTY;
     for p in pb.iter().flat_map(|p| &p.v) {
         tool.add(*p);
@@ -504,6 +508,13 @@ fn sliced_planar_boolean(a: &Body, b: &Body, op: BoolOp) -> Option<Result<Option
         for (slot, (cut, keep_positive)) in [(2, (lo, true)), (4, (hi, false))] {
             let Some(x) = cut else { continue };
             let plane = solidcraft_geom::Plane::new(axis * x, u, w).ok_or_else(|| fail("plane"))?;
+            // Split along the plane (an imprint: no boolean); two booleans with half boxes
+            // where the split can't be sorted into one piece kept and the rest away.
+            if let Some((away, kept)) = split_beside(&middle, &plane, axis, x, keep_positive) {
+                outside.extend(away);
+                middle = kept;
+                continue;
+            }
             let (away, kept) = (crate::ops::half_box(&middle.0, &plane, !keep_positive)?, crate::ops::half_box(&middle.0, &plane, keep_positive)?);
             let (h_away, h_kept) = (recorded::kept(&away, slot, n), recorded::kept(&kept, slot + 1, n));
             if let Some(o) = crate::ops::boolean(&middle.0, &away, BoolOp::Intersect)? {
@@ -584,6 +595,41 @@ fn sliced_planar_boolean(a: &Body, b: &Body, op: BoolOp) -> Option<Result<Option
     Some(run())
 }
 
+/// `piece` split by `plane` (at `x` along `axis`): the parts on the side away from the tool
+/// and the one part on its side (positive along `axis` when `keep_positive`), each with its
+/// history over the operands `piece`'s is over. `None` when the split leaves no part on either
+/// side, or several on the tool's.
+fn split_beside(piece: &Traced, plane: &solidcraft_geom::Plane, axis: Vec3, x: f64, keep_positive: bool) -> Option<(Vec<Traced>, Traced)> {
+    let parts = crate::splitface::split_body(&piece.0, &crate::splitface::SplitTool::Plane(*plane)).ok()?;
+    if parts.len() < 2 {
+        return None;
+    }
+    let tol = piece.0.size() * 1e-6 + 1e-9;
+    let (mut away, mut kept) = (Vec::new(), Vec::new());
+    for part in parts {
+        let (mut lo, mut hi) = (f64::INFINITY, f64::NEG_INFINITY);
+        for v in part.solid.vertex_iter() {
+            let t = from_p3(v.point()).dot(axis) - x;
+            lo = lo.min(t);
+            hi = hi.max(t);
+        }
+        let h = match (part.history(), piece.1.as_ref()) {
+            (Some(hp), Some(h)) => recorded::composed(hp.clone().substituted(0, h)),
+            _ => None,
+        };
+        let positive = if lo >= -tol {
+            true
+        } else if hi <= tol {
+            false
+        } else {
+            return None;
+        };
+        if positive == keep_positive { kept.push((part, h)) } else { away.push((part, h)) }
+    }
+    let kept = kept.pop().filter(|_| kept.is_empty())?;
+    (!away.is_empty()).then_some((away, kept))
+}
+
 /// `h` over `[a, b]`: the operands after them (the boxes a piece was cut with) dropped, which
 /// fails where something of them is left.
 fn dropped(h: Option<History>) -> Option<History> {
diff --git a/crates/kernel/src/splitface.rs b/crates/kernel/src/splitface.rs
index 88038c6b..6ea12585 100644
--- a/crates/kernel/src/splitface.rs
+++ b/crates/kernel/src/splitface.rs
@@ -124,6 +124,9 @@ fn trace_tol(face: &mt::Face, size: f64) -> f64 {
 
 /// Trace the zero set of `g` over a face: chains of exact points.
 fn trace(face: &mt::Face, g: &Field, size: f64) -> Result<Vec<Chain>> {
+    if let Some(chains) = trace_flat(face, g, size) {
+        return Ok(chains);
+    }
     let tol = trace_tol(face, size);
     let shell: mt::Shell = vec![face.clone()].into();
     let meshed = shell.robust_triangulation(tol);
@@ -290,6 +293,53 @@ fn trace(face: &mt::Face, g: &Field, size: f64) -> Result<Vec<Chain>> {
     Ok(chains)
 }
 
+/// A plane across a flat face (a plane, or a B-spline surface that is one) with straight edges,
+/// exactly: the line the two planes meet in, inside the face between pairs of its crossings with
+/// the boundary, taken in order along the line. Which side a corner is on is decided once, at
+/// the corner, so a plane through a corner crosses the boundary there once or not at all, as it
+/// should. `None` (traced on a mesh instead) for any other face or tool, and where an edge lies
+/// in the plane.
+fn trace_flat(face: &mt::Face, g: &Field, size: f64) -> Option<Vec<Chain>> {
+    let Field::Plane { o, n } = g else { return None };
+    let surface = face.surface();
+    let Field::Plane { n: m, .. } = surface_field(&surface) else { return None };
+    let along = m.cross(*n).normalized()?;
+    let tol = size * 1e-7 + 1e-9;
+    let mut hits: Vec<mt::Point3> = Vec::new();
+    for e in face.boundaries().iter().flat_map(|w| w.edge_iter()) {
+        let (a, b) = (from_p3(e.front().point()), from_p3(e.back().point()));
+        let (ga, gb) = ((a - *o).dot(*n), (b - *o).dot(*n));
+        // Straight: a line, or a curve (a B-spline of degree one) whose points all lie on its
+        // chord; such an edge crosses the plane once at most.
+        let straight = matches!(e.curve(), mt::Curve::Line(_)) || {
+            let c = e.curve();
+            let (t0, t1) = c.range_tuple();
+            (1..8).all(|k| from_p3(c.subs(t0 + (t1 - t0) * k as f64 / 8.0)).dist_to_segment(a, b) <= tol)
+        };
+        if !straight || (ga.abs() <= tol && gb.abs() <= tol) || !ga.is_finite() || !gb.is_finite() {
+            return None;
+        }
+        if (ga >= 0.0) != (gb >= 0.0) {
+            hits.push(p3(a + (b - a) * (ga / (ga - gb)).clamp(0.0, 1.0)));
+        }
+    }
+    if !hits.len().is_multiple_of(2) {
+        return None;
+    }
+    hits.sort_by(|a, b| from_p3(*a).dot(along).total_cmp(&from_p3(*b).dot(along)));
+    let uv = |p: mt::Point3| surface.search_nearest_parameter(p, None, 50);
+    let mut chains = Vec::new();
+    for pair in hits.chunks(2) {
+        let [a, b] = pair else { return None };
+        // A corner the plane only touches: no line.
+        if a.distance(*b) <= tol {
+            continue;
+        }
+        chains.push(Chain { pts: vec![(*a, uv(*a)?), (*b, uv(*b)?)], closed: false });
+    }
+    Some(chains)
+}
+
 /// Where the zero set crosses a boundary edge of the face (exact, by bisection on the curve).
 fn boundary_hits(face: &mt::Face, g: &Field) -> Vec<Hit> {
     let mut out = Vec::new();
@@ -1084,9 +1134,22 @@ pub(crate) fn split_any(body: &Body, faces: &[usize], tool: &SplitTool) -> Resul
     })
 }
 
-/// A point well inside a face (a mesh triangle's centre where the field is largest) and the
-/// field there.
+/// The field at a point well inside a face (a mesh triangle's centre where the field is
+/// largest; for a plane, the face's corner farthest from it).
 fn side_of(face: &mt::Face, g: &Field, size: f64) -> Result<f64> {
+    // A face the plane does not cross is on the side of whichever corner lies off it (the
+    // farthest, against rounding); a face with every corner on the plane is meshed.
+    if let Field::Plane { .. } = g {
+        let far = face
+            .boundaries()
+            .iter()
+            .flat_map(|w| w.vertex_iter())
+            .map(|v| g.eval(from_p3(v.point())))
+            .fold(0.0, |b: f64, x| if x.abs() > b.abs() { x } else { b });
+        if far.abs() > size * 1e-6 {
+            return Ok(far);
+        }
+    }
     let shell: mt::Shell = vec![face.clone()].into();
     let meshed = shell.robust_triangulation((size * 2e-3).max(1e-4));
     let pm = meshed.face_iter().next().and_then(|f| f.surface()).ok_or_else(|| KernelError::Failed("a face could not be meshed".into()))?;