Multi profile extrusion performance (#2064)

Thanks @Koschtetnix.

ROADMAP.md

@@ -274,6 +274,25 @@ completed drawings publish atomically. The browser still exports synchronously.
 
 ## 0.2.1 critical fixes
 
+- Separated multi-profile Join/Cut extrusions into one solid target batch their tools using
+  conservative construction bounds, avoiding a Boolean rebuild for every profile. Live
+  extrusion previews build only their tools; confirmation validates the final Boolean.
+- Coplanar selected body faces share one linked sketch and one extrusion. Automatic Join/Cut
+  keeps the evaluator's participant scope, including parts of an empty imported component. Desktop OK/Enter
+  computes on a scratch session in the background, with atomic acceptance and cancellation.
+  Planar section stitching projects lines/arcs analytically and removes duplicate endpoints.
+- Imported rotated face groups can check all full start-face seams in one guarded
+  construction. Separated tools may batch a Join when each meets the same single body;
+  nearby uninvolved bodies retain the original contact decisions. Regression comparisons
+  cover all four extrusion operations.
+- Inward multi-face cuts retain every eligible target and subtract separated tools together.
+  Safe interior classification handles roundoff at shared imported line/arc endpoints.
+  Straight extrusion feedback caches existing face/profile triangles and updates the display
+  directly, including a newly opened STEP's single identity component placement; other
+  extents, moved or repeated components and curved sketch profiles keep the Engine preview.
+- The extrusion fixes retain tracked Boolean history and the current `solidcraft` packages.
+  Confirmation and tool previews use main's shared background calculation. Main's collapsed
+  blend-wall refusal and its tests are retained, including smaller valid radii and mirrored parts.
 - Axis view and navigation controls stay anchored to the viewport when feature dialogs or
   the command palette open, at normal and enlarged display scales. Fit still accounts for
   dialog coverage; covered controls do not receive clicks through dialogs.

crates/doc/src/eval.rs

@@ -1581,6 +1581,29 @@ fn apply_beside_sheet_cut(st: &mut ModelState, f: &Feature, tools: Vec<Traced>,
     apply_traced(st, f, tools, op, &rest)
 }
 
+/// Only one target meets every separated tool. A tool with no contact must retain
+/// Join's first-target fallback; tools touching different targets must retain absorption order.
+fn common_join_target(state: &ModelState, indices: &[usize], tools: &[Traced]) -> Result<Option<usize>> {
+    if indices.len() > 64 {
+        return Ok(None);
+    }
+    let bodies: Vec<_> = tools.iter().map(|tool| tool.body.clone()).collect();
+    let mut contacts = vec![None; tools.len()];
+    for &index in indices {
+        let body = state.bodies.get(index).ok_or_else(|| DocError::Invalid("join target disappeared".into()))?;
+        for (contact, meets) in contacts.iter_mut().zip(body.body.meets_each(&bodies)?) {
+            if meets {
+                if contact.is_some() {
+                    return Ok(None);
+                }
+                *contact = Some(index);
+            }
+        }
+    }
+    let common = contacts.first().copied().flatten();
+    Ok(common.filter(|index| contacts.iter().all(|contact| *contact == Some(*index))))
+}
+
 fn apply_op(state: &mut ModelState, f: &Feature, tools: Vec<Body>, op: Operation, targets: &[String]) -> Result<()> {
     apply_traced(state, f, tools.into_iter().map(Traced::unnamed).collect(), op, targets)
 }
@@ -1636,6 +1659,41 @@ fn apply_traced(state: &mut ModelState, f: &Feature, tools: Vec<Traced>, op: Ope
             }
         }
     }
+    // Batching solid targets must preserve Join's absorption order,
+    // sheet material tracking and the separate bodies of a New Body extrusion.
+    if tools.len() > 1
+        && matches!(f.kind, FeatureKind::Extrude { .. })
+        && matches!(op, Operation::Join | Operation::Cut)
+        && !target_idx.is_empty()
+        && target_idx.iter().all(|i| state.bodies.get(*i).is_some_and(|b| !b.body.is_mesh() && !state.sheets.iter().any(|s| s.body == b.name)))
+        && let Ok(Some(compound)) = kernel::compound_disjoint_extrusions(&tools.iter().map(|tool| tool.body.clone()).collect::<Vec<_>>())
+    {
+        let target = if target_idx.len() == 1 {
+            target_idx.first().copied()
+        } else if op == Operation::Join {
+            common_join_target(state, &target_idx, &tools).ok().flatten()
+        } else {
+            None
+        };
+        // The optimization must not reject geometry the original sequential path can
+        // handle. A failed batch leaves the model untouched and retries the original tools.
+        let batch_targets = if op == Operation::Cut {
+            // Subtracting a union equals subtracting its separated tools in order.
+            // Keep ALL original participants; no sampled contact test excludes a body.
+            Some(target_idx.iter().filter_map(|index| state.bodies.get(*index).map(|body| body.name.clone())).collect::<Vec<_>>())
+        } else {
+            target.and_then(|index| state.bodies.get(index)).map(|body| vec![body.name.clone()])
+        };
+        if let Some(names) = batch_targets {
+            let mut batched = state.clone();
+            // Preserve the original participants. For Join, the compound's larger
+            // size must not expand the contact tolerance and absorb a nearby body.
+            if apply_traced(&mut batched, f, vec![Traced::step(compound, &tools.iter().collect::<Vec<_>>())], op, &names).is_ok() {
+                *state = batched;
+                return Ok(());
+            }
+        }
+    }
     match op {
         Operation::Join => {
             // Each tool joins every target it meets into one body, kept under the first one's
@@ -3219,25 +3277,63 @@ fn feature_tools_with_constructor(
             // Each tool's extent along the normal (they differ where one is run on into a face).
             let mut extents: Vec<(f64, f64)> = Vec::with_capacity(regions.len());
             let plain_targets: Vec<String> = crate::plain(targets);
-            let surroundings = Surroundings::of(st, *operation, &plain_targets);
-            // Trimming may discard a tool's material, so only bodies this feature
-            // actually joins can establish that the discarded end is already filled.
-            let participants = if plain_targets.is_empty() { &f.participants } else { &plain_targets };
-            let trim_targets: Vec<String> = st
-                .bodies
-                .iter()
-                .filter(|b| {
-                    if participants.is_empty() {
-                        b.component == f.component || b.feature == f.id
-                    } else {
-                        participants.iter().any(|t| t == "*" || t == &b.name)
-                    }
-                })
-                .map(|b| b.name.clone())
-                .collect();
-            let join_surroundings =
-                if *operation == Operation::Join && !trim_targets.is_empty() { Surroundings::of(st, *operation, &trim_targets) } else { None };
-            for r in &regions {
+            let exact_planar_cut = *operation == Operation::Cut
+                && ss.sketch.links.len() > 1
+                && ss.sketch.links.iter().all(|link| matches!(&link.source, solidcraft_sketch::LinkSource::Face { .. }))
+                && st
+                    .bodies
+                    .iter()
+                    .filter(|body| plain_targets.is_empty() || plain_targets.iter().any(|target| target == "*" || target == &body.name))
+                    .all(|body| kernel::is_planar(&body.body));
+            let mut touching_batch = false;
+            // Generated face profiles have full source seams. Check all of them in
+            // one guarded construction; arbitrary sketch profiles retain their existing path.
+            if *operation == Operation::Join
+                && regions.len() > 1
+                && ss.sketch.links.len() > 1
+                && ss.sketch.links.iter().all(|link| matches!(&link.source, solidcraft_sketch::LinkSource::Face { .. }))
+            {
+                let exact = regions
+                    .iter()
+                    .map(|region| centered_extrude(&ss.plane, region, lo + off, hi + off, Some(&ss)))
+                    .collect::<Result<Vec<_>>>()?
+                    .into_iter()
+                    .flatten()
+                    .collect::<Vec<_>>();
+                if let Ok(Some(compound)) = kernel::compound_disjoint_extrusions(&exact.iter().map(|tool| tool.body.clone()).collect::<Vec<_>>())
+                    && st
+                        .bodies
+                        .iter()
+                        .filter(|body| plain_targets.is_empty() || plain_targets.contains(&body.name))
+                        .any(|body| kernel::can_join_all_touching_faces(&body.body, &compound))
+                {
+                    tools = exact;
+                    touching_batch = true;
+                }
+            }
+            let surroundings = if exact_planar_cut || touching_batch { None } else { Surroundings::of(st, *operation, &plain_targets) };
+            let join_surroundings = if *operation == Operation::Join && !touching_batch {
+                // Trimming may discard a tool's material, so only bodies this feature
+                // actually joins can establish that the discarded end is already filled.
+                let participants = if plain_targets.is_empty() { &f.participants } else { &plain_targets };
+                let trim_targets: Vec<String> = st
+                    .bodies
+                    .iter()
+                    .filter(|b| {
+                        if participants.is_empty() {
+                            b.component == f.component || b.feature == f.id
+                        } else {
+                            participants.iter().any(|t| t == "*" || t == &b.name)
+                        }
+                    })
+                    .map(|b| b.name.clone())
+                    .collect();
+
+                if trim_targets.is_empty() { None } else { Surroundings::of(st, *operation, &trim_targets) }
+            } else {
+                None
+            };
+            for r in regions.iter().filter(|_| !touching_batch) {
                 if *operation == Operation::Join {
                     let exact = centered_extrude(&ss.plane, r, lo + off, hi + off, Some(&ss))?;
                     if exact.iter().all(|tool| {

crates/engine/src/boolean_regression_tests.rs

@@ -584,3 +584,227 @@ fn closed_sweep_redefines_to_a_half_turn_torus_cut() {
         assert_eq!(mesh.contains(point), material, "material at {point:?}");
     }
 }
+
+#[test]
+fn many_extrusion_profiles_preserve_material_and_body_identity() {
+    for operation in ["join", "cut", "new"] {
+        let mut s = Session::default();
+        s.execute("solid.box", &json!({"length": 40, "width": 30, "height": 20, "body_name": "Stock"})).unwrap();
+        s.execute("sketch.create", &json!({"plane": {"origin": [0, 0, 20], "x_dir": [1, 0, 0], "y_dir": [0, 1, 0]}})).unwrap();
+        for i in 0..6 {
+            for j in 0..4 {
+                let (x, y) = (2 + i * 6, 2 + j * 7);
+                s.execute("sketch.rectangle.two_point", &json!({"p0": [x, y], "p1": [x + 4, y + 4]})).unwrap();
+            }
+        }
+        s.execute("sketch.finish", &json!({})).unwrap();
+        let distance = if operation == "cut" { -5 } else { 5 };
+        let before = s.revision;
+        s.execute("solid.extrude", &json!({"distance": distance, "operation": operation})).unwrap();
+        let state = s.model.state();
+        assert_eq!(state.bodies.len(), if operation == "new" { 25 } else { 1 });
+        let expected = 24_000.0
+            + match operation {
+                "join" => 1920.0,
+                "cut" => -1920.0,
+                _ => 0.0,
+            };
+        assert!((volume(&s, "Stock") - expected).abs() < 1e-6);
+        let stock = state.body("Stock").unwrap();
+        for (point, present) in [([3.0, 3.0, 22.0], operation == "join"), ([3.0, 3.0, 18.0], operation != "cut"), ([7.0, 3.0, 18.0], true)] {
+            assert_eq!(stock.mesh().contains(solidcraft_geom::Vec3::from(point)), present, "{operation}: {point:?}");
+        }
+        assert!(stock.body.validity().is_empty());
+        assert!(s.revision > before);
+        s.execute("edit.undo", &json!({})).unwrap();
+        assert!((volume(&s, "Stock") - 24_000.0).abs() < 1e-6);
+        s.execute("edit.redo", &json!({})).unwrap();
+        assert!((volume(&s, "Stock") - expected).abs() < 1e-6);
+    }
+}
+
+#[test]
+fn many_circular_extrusion_profiles_cut_a_curved_target() {
+    let mut s = Session::default();
+    s.execute("solid.cylinder", &json!({"radius": 20, "height": 20, "body_name": "Stock"})).unwrap();
+    s.execute("sketch.create", &json!({"plane": {"origin": [0, 0, -1], "x_dir": [1, 0, 0], "y_dir": [0, 1, 0]}})).unwrap();
+    for x in [-9, -3, 3, 9] {
+        for y in [-9, -3, 3, 9] {
+            s.execute("sketch.circle.center", &json!({"center": [x, y], "radius": 1})).unwrap();
+        }
+    }
+    s.execute("sketch.finish", &json!({})).unwrap();
+    s.execute("solid.extrude", &json!({"distance": 22, "operation": "cut", "targets": ["Stock"]})).unwrap();
+    // The rebuilt caps mesh more finely than the original cylinder. Compare with the
+    // analytic material volume, rather than subtracting two differently faceted meshes.
+    let expected = (400.0 - 16.0) * std::f64::consts::PI * 20.0;
+    let actual = volume(&s, "Stock");
+    assert!((actual - expected).abs() < expected * 1e-5, "{actual} vs {expected}");
+    let state = s.model.state();
+    assert_eq!(state.bodies.len(), 1);
+    let stock = state.body("Stock").unwrap();
+    assert!(stock.body.validity().is_empty());
+    let mesh = stock.mesh();
+    assert!(mesh.contains(solidcraft_geom::Vec3::new(0.0, 0.0, 10.0)));
+    for x in [-9.0, -3.0, 3.0, 9.0] {
+        for y in [-9.0, -3.0, 3.0, 9.0] {
+            assert!(!mesh.contains(solidcraft_geom::Vec3::new(x, y, 10.0)), "hole at {x}, {y}");
+        }
+    }
+}
+
+#[test]
+fn coplanar_body_faces_extrude_together_and_replay_their_links() {
+    let mut s = Session::default();
+    s.execute("solid.box", &json!({"length":64,"width":64,"height":20,"body_name":"Plate"})).unwrap();
+    s.execute("sketch.create", &json!({"plane":{"origin":[0,0,20],"x_dir":[1,0,0],"y_dir":[0,1,0]}})).unwrap();
+    let mut faces = Vec::new();
+    for i in 0..8 {
+        for j in 0..8 {
+            let (x, y) = (2 + i * 7, 2 + j * 7);
+            s.execute("sketch.rectangle.two_point", &json!({"p0":[x,y],"p1":[x+4,y+4]})).unwrap();
+            faces.push(json!([x + 2, y + 2, 26]));
+        }
+    }
+    s.execute("sketch.finish", &json!({})).unwrap();
+    s.execute("solid.extrude", &json!({"distance":6,"operation":"join"})).unwrap();
+    let (features, undo) = (s.doc.features.len(), s.undo.len());
+    s.execute("solid.extrude", &json!({"faces":faces,"distance":-7,"operation":"cut"})).unwrap();
+    assert_eq!(s.doc.features.len(), features + 2, "one linked sketch and one extrusion");
+    assert_eq!(s.undo.len(), undo + 1);
+    let actual = volume(&s, "Plate");
+    let state = s.model.state();
+    let sketch = state.sketch(4).unwrap();
+    assert!((actual - 80_896.0).abs() < 1e-5, "volume {actual}; plane {:?}; profiles {}", sketch.plane, sketch.profiles.len());
+    assert_eq!(s.model.state().bodies.len(), 1);
+    let document = serde_json::from_value(serde_json::to_value(s.doc.as_ref()).unwrap()).unwrap();
+    let mut reopened = Session { doc: std::sync::Arc::new(document), ..Session::default() };
+    reopened.refresh();
+    assert!((volume(&reopened, "Plate") - 80_896.0).abs() < 1e-5);
+    s.execute("edit.undo", &json!({})).unwrap();
+    assert_eq!(s.doc.features.len(), features);
+    s.execute("edit.redo", &json!({})).unwrap();
+    assert!((volume(&s, "Plate") - 80_896.0).abs() < 1e-5);
+}
+
+#[test]
+fn unsupported_face_groups_are_atomic() {
+    let mut s = Session::default();
+    s.execute("solid.box", &json!({"length":10,"width":10,"height":10})).unwrap();
+    let before = serde_json::to_value(s.doc.as_ref()).unwrap();
+    let (revision, undo) = (s.revision, s.undo.len());
+    for faces in [
+        json!([]),
+        json!([[5, 5, 10], [5, 5, 0]]),
+        json!([[5, 5, 10], [5, 0, 5]]),
+        json!([[5, 5, 10], [1000, 1000, 1000]]),
+        json!(vec![[5, 5, 10]; 1025]),
+    ] {
+        assert!(s.execute("solid.extrude", &json!({"faces":faces,"distance":5,"operation":"join"})).is_err());
+        assert_eq!(serde_json::to_value(s.doc.as_ref()).unwrap(), before);
+        assert_eq!((s.revision, s.undo.len()), (revision, undo));
+    }
+}
+
+#[test]
+fn imported_rotated_face_extrusions_preserve_other_operations_and_bodies() {
+    use solidcraft_geom::Vec3;
+    let mut source = Session::default();
+    source.execute("solid.box", &json!({"corner":[-16,-16,-3],"length":32,"width":32,"height":1,"body_name":"Other"})).unwrap();
+    source.execute("solid.cylinder", &json!({"radius":14,"height":8,"body_name":"Stock"})).unwrap();
+    let mut outlines = Vec::new();
+    let mut centers = Vec::new();
+    for i in 0..12 {
+        let angle = i as f64 * std::f64::consts::TAU / 12.;
+        let (c, s) = (angle.cos(), angle.sin());
+        let outline: Vec<_> =
+            [(-2., -2.), (2., -2.), (2., 2.), (-2., 2.)].into_iter().map(|(x, y)| [10.7 * c + x * c - y * s, 10.7 * s + x * s + y * c]).collect();
+        outlines.push(outline);
+        centers.push([10.7 * c, 10.7 * s, 12.]);
+    }
+    let draw = |session: &mut Session, height: f64| {
+        session.execute("sketch.create", &json!({"plane":{"origin":[0,0,height],"x_dir":[1,0,0],"y_dir":[0,1,0]}})).unwrap();
+        for outline in &outlines {
+            session.execute("sketch.line", &json!({"points":outline,"closed":true,"infer":false})).unwrap();
+        }
+        session.execute("sketch.finish", &json!({})).unwrap();
+    };
+    draw(&mut source, 8.);
+    source.execute("solid.extrude", &json!({"distance":4,"operation":"join"})).unwrap();
+    // An original public-safe STEP example, with rotated full-face seams and a
+    // curved target. No vendor/user design is part of this regression.
+    let path = std::env::temp_dir().join(format!("solidcraft-face-extrusion-{}.step", std::process::id()));
+    source.execute("file.export", &json!({"path":path.to_string_lossy()})).unwrap();
+    let mut imported = Session::default();
+    imported.execute("doc.open", &json!({"path":path.to_string_lossy()})).unwrap();
+    std::fs::remove_file(path).unwrap();
+    let original = imported.model.state();
+    let other = original.body("Other").unwrap().body.clone();
+    for (operation, distance) in [("join", 2.), ("cut", -1.), ("new", 2.), ("intersect", -1.)] {
+        let mut grouped = imported.scratch();
+        grouped.execute("solid.extrude", &json!({"faces":centers,"distance":distance,"operation":operation})).unwrap();
+        let mut reference = imported.scratch();
+        draw(&mut reference, 12.);
+        if matches!(operation, "join" | "cut") {
+            // Individual tools retain the original Boolean and participant path.
+            for index in 0..12 {
+                reference
+                    .execute("solid.extrude", &json!({"sketch":"Sketch1","profiles":[index],"distance":distance,"operation":operation}))
+                    .unwrap();
+            }
+        } else {
+            reference.execute("solid.extrude", &json!({"distance":distance,"operation":operation})).unwrap();
+        }
+        let actual = grouped.model.state();
+        let expected = reference.model.state();
+        assert_eq!(actual.bodies.len(), expected.bodies.len(), "{operation}");
+        for body in &actual.bodies {
+            let reference = expected.body(&body.name).unwrap();
+            // Fixed fine chord tolerance: cap subdivision can change the default
+            // adaptive mesh's cylinder faceting without changing its analytic surface.
+            let (a, b) = (body.body.tessellate(1e-5).unwrap().measure().volume, reference.body.tessellate(1e-5).unwrap().measure().volume);
+            assert!((a - b).abs() < b.max(1.) * 1e-6, "{operation}: {} {a} vs {b}", body.name);
+            assert!(body.body.validity().is_empty(), "{operation}: {}", body.name);
+            let (a, b) = (body.mesh(), reference.mesh());
+            for center in &centers {
+                for z in [7., 11.5, 13.] {
+                    let point = Vec3::new(center[0], center[1], z);
+                    assert_eq!(a.contains(point), b.contains(point), "{operation}: {} {point:?}", body.name);
+                }
+            }
+        }
+        if operation != "intersect" {
+            let unchanged = &actual.body("Other").unwrap().body;
+            assert_eq!(unchanged.face_count(), other.face_count());
+            assert_eq!(unchanged.color(), other.color());
+            assert_eq!(unchanged.tessellate(0.01).unwrap().positions, other.tessellate(0.01).unwrap().positions, "unaffected imported body");
+        }
+    }
+}
+
+#[test]
+fn multi_target_join_keeps_nearby_bodies_and_original_absorption_order() {
+    for (second_x, expected_count) in [(10.0015, 2), (9., 1)] {
+        let mut session = Session::default();
+        session.execute("solid.box", &json!({"length":10,"width":10,"height":10,"body_name":"Stock"})).unwrap();
+        session.execute("solid.box", &json!({"corner":[second_x,8,10],"length":1,"width":1,"height":2,"body_name":"Other"})).unwrap();
+        session.execute("sketch.create", &json!({"plane":{"origin":[0,0,10],"x_dir":[1,0,0],"y_dir":[0,1,0]}})).unwrap();
+        for origin in [[0., 0.], [8., 8.]] {
+            session.execute("sketch.rectangle.two_point", &json!({"p0":origin,"p1":[origin[0]+2.,origin[1]+2.]})).unwrap();
+        }
+        session.execute("sketch.finish", &json!({})).unwrap();
+        let mut reference = session.scratch();
+        for index in 0..2 {
+            reference.execute("solid.extrude", &json!({"sketch":"Sketch1","profiles":[index],"distance":2,"operation":"join"})).unwrap();
+        }
+        session.execute("solid.extrude", &json!({"distance":2,"operation":"join"})).unwrap();
+        assert_eq!(session.model.state().bodies.len(), expected_count);
+        assert_eq!(
+            session.model.state().bodies.iter().map(|body| body.name.clone()).collect::<Vec<_>>(),
+            reference.model.state().bodies.iter().map(|body| body.name.clone()).collect::<Vec<_>>()
+        );
+        for body in &session.model.state().bodies {
+            assert!((volume(&session, &body.name) - volume(&reference, &body.name)).abs() < 1e-6);
+        }
+    }
+}

crates/engine/src/cmd/face.rs

@@ -84,6 +84,10 @@ type FacePick = (std::sync::Arc<Mesh>, u32, f64, String);
 /// equally near (bodies touching flush), the pick is ambiguous: `Err` names those bodies.
 fn face_at_in(s: &Session, p: Vec3, only: Option<&str>) -> std::result::Result<Option<FacePick>, Vec<String>> {
     let st = s.model.state();
+    face_at_state(&st, p, only)
+}
+
+pub(super) fn face_at_state(st: &solidcraft_doc::ModelState, p: Vec3, only: Option<&str>) -> std::result::Result<Option<FacePick>, Vec<String>> {
     let mut best: Option<FacePick> = None;
     let mut tied: Vec<String> = Vec::new();
     for b in st.bodies.iter().filter(|b| only.is_none_or(|n| b.name == n)) {
@@ -127,6 +131,80 @@ fn xy(v: Vec2) -> Value {
     json!([v.x, v.y])
 }
 
+/// Coplanar faces share one linked profile sketch and one Extrude feature. Resolve every
+/// pick before editing the document, so later picks never search an already modified body.
+pub(super) fn sketch_of_faces(s: &mut Session, points: &[Vec3], cmd: &str, face_body: Option<&str>) -> Result<(u64, Vec<Vec2>, String)> {
+    let first = points.first().copied().ok_or_else(|| bad(cmd, "faces must not be empty"))?;
+    if points.len() > 1024 {
+        return Err(bad(cmd, "faces exceed the 1024-face limit"));
+    }
+    let state = s.model.state();
+    let mut picked = Vec::new();
+    let mut common: Option<(String, solidcraft_geom::Plane)> = None;
+    for &point in points {
+        if !point.is_finite() {
+            return Err(bad(cmd, "faces must be finite points"));
+        }
+        let (mesh, index, distance, name) = face_at_in(s, point, face_body)
+            .map_err(|_| bad(cmd, "ambiguous face; specify face_body"))?
+            .ok_or_else(|| bad(cmd, "no body face at a selected point"))?;
+        let body = state.body(&name).ok_or_else(|| bad(cmd, "selected body disappeared"))?;
+        let plane = body.body.planar_face(index as usize).ok_or_else(|| bad(cmd, "faces must be planar"))?;
+        let tolerance = (body.body.size() * 1e-9).max(1e-8);
+        if distance > (mesh.bounds().diagonal() * 1e-3).max(1e-3) * 10.0 {
+            return Err(bad(cmd, "no body face at a selected point"));
+        }
+        if let Some((previous, base)) = &common {
+            if *previous != name || base.normal().dot(plane.normal()) < 1.0 - 1e-9 || base.height(plane.origin).abs() > tolerance {
+                return Err(bad(cmd, "faces must be coplanar, equally oriented faces of one body"));
+            }
+        } else {
+            common = Some((name.clone(), plane));
+        }
+        if picked.iter().any(|(face, _)| *face == index as usize) {
+            continue;
+        }
+        let inside = mesh
+            .triangles
+            .iter()
+            .zip(&mesh.tri_face)
+            .filter(|(_, face)| **face == index)
+            .filter_map(|(triangle, _)| mesh.tri(triangle))
+            .max_by(|[a, b, c], [x, y, z]| ((*b - *a).cross(*c - *a).len()).total_cmp(&((*y - *x).cross(*z - *x).len())))
+            .map(|[a, b, c]| (a + b + c) / 3.0)
+            .ok_or_else(|| bad(cmd, "degenerate face"))?;
+        picked.push((index as usize, inside));
+    }
+    let (id, first_inside, _) = sketch_of_face(s, first, cmd, face_body)?;
+    let (body, _) = common.ok_or_else(|| bad(cmd, "no faces selected"))?;
+    let doc = s.placed_document();
+    let source = state.body(&body).ok_or_else(|| bad(cmd, "source body disappeared"))?;
+    let component = doc.model_body_component(source);
+    let path = if component == s.active_component {
+        s.active_occurrence_path.clone().unwrap_or_else(|| doc.first_path(component))
+    } else {
+        let placements = super::component::properties::placements(&doc, cmd)?;
+        if placements.iter().filter(|(owner, _, _)| *owner == component).count() != 1 {
+            return Err(bad(cmd, "activate the selected occurrence before extruding its faces"));
+        }
+        doc.first_path(component)
+    };
+    let placement = EmbossFace::component_frame(&doc, component, &path)?;
+    let placement = doc.model_body_offset(source).map(|offset| mat_mul(&placement, offset)).unwrap_or(placement);
+    let author_path = s.active_occurrence_path.clone().unwrap_or_else(|| doc.first_path(s.active_component));
+    let author = EmbossFace::component_frame(&doc, s.active_component, &author_path)?;
+    let inverse = mat_inverse(&author).ok_or_else(|| bad(cmd, "invalid face profile author frame"))?;
+    let into_author = mat_mul(&inverse, &placement);
+    drop(doc);
+    let indices: Vec<_> = picked.iter().skip(1).map(|(index, _)| *index).collect();
+    super::sketch_project::project_internal_faces(s, id, &body, &indices)?;
+    s.refresh();
+    let plane = s.model.state().sketch(id).map(|sketch| sketch.plane).ok_or_else(|| bad(cmd, "face profile sketch disappeared"))?;
+    let mut selected = vec![first_inside];
+    selected.extend(picked.iter().skip(1).map(|(_, point)| plane.to_local(apply_point(&into_author, *point))));
+    Ok((id, selected, body))
+}
+
 /// Start a sketch on the planar face at `point` holding a copy of the face boundary. Returns
 /// the sketch id, a point inside the face (sketch coordinates), and the picked body's name.
 /// The sketch is left active.

crates/engine/src/cmd/features.rs

@@ -18,7 +18,7 @@ pub static COMMANDS: &[CommandSpec] = &[
         .at("SOLID", "CREATE")
         .icon("extrude")
         .key("E")
-        .params("distance: expr (or through_all: true); taper?: angle expr; sketch?: id|name (default: active or last sketch); profiles?: all | [index] | [{curves: [ids]}] (the profile whose outer loop is made of exactly these curves, or pieces of them; found again on every recompute, so it follows parameter changes; islands inside are its holes; an error when no profile or several match) | [{point:[x,y]}] (index and point picks are stored by their curves when that finds the same profile); face?: [x,y,z] (extrude a planar body face instead of a sketch profile); face_body?: name (whose face, where faces of several bodies meet at the point); direction?: positive|negative|symmetric (distance is total thickness, split evenly around the start plane); convention?: total_distance|legacy_per_side (default total_distance; legacy preserves older symmetric extents); distance2?; start_offset?: expr (along the sketch normal, also with direction: negative); to?: [x,y,z] (To Object: a face, vertex or point; to_offset?: expr past it); from?: [x,y,z] (From Object: start at that face or point); operation?: new|join|cut|intersect|auto (cut into a body, otherwise join existing solids; new in an empty component); targets?: [body] (Join from a face, or from a sketch on a body's face, defaults to that face's body; explicit targets or participants override); name?; body_name?; thin?: true (Thin: a wall along sketch curves instead of the profiles) with curves?: [curve ids] (open chains and closed loops, joined where they meet end to end; default: every drawn curve of the sketch), thickness: expr, side?: center|inside|outside|two_sides (a closed loop's inside is the area it encloses, an open chain's the side it bends toward, a straight line's the left of its first curve as drawn; default center), thickness2?: expr (two_sides: the thickness outside); corners are mitred, crossing walls are one"),
+        .params("distance: expr (or through_all: true); taper?: angle expr; sketch?: id|name (default: active or last sketch); profiles?: all | [index] | [{curves: [ids]}] (the profile whose outer loop is made of exactly these curves, or pieces of them; found again on every recompute, so it follows parameter changes; islands inside are its holes; an error when no profile or several match) | [{point:[x,y]}] (index and point picks are stored by their curves when that finds the same profile); face?: [x,y,z] (extrude a planar body face instead of a sketch profile); faces?: [[x,y,z],…] (coplanar faces of one body); face_body?: name (whose face, where faces of several bodies meet at the point); direction?: positive|negative|symmetric (distance is total thickness, split evenly around the start plane); convention?: total_distance|legacy_per_side (default total_distance; legacy preserves older symmetric extents); distance2?; start_offset?: expr (along the sketch normal, also with direction: negative); to?: [x,y,z] (To Object: a face, vertex or point; to_offset?: expr past it); from?: [x,y,z] (From Object: start at that face or point); operation?: new|join|cut|intersect|auto (cut into a body, otherwise join existing solids; new in an empty component); targets?: [body] (Join from a face, or from a sketch on a body's face, defaults to that face's body; explicit targets or participants override); name?; body_name?; thin?: true (Thin: a wall along sketch curves instead of the profiles) with curves?: [curve ids] (open chains and closed loops, joined where they meet end to end; default: every drawn curve of the sketch), thickness: expr, side?: center|inside|outside|two_sides (a closed loop's inside is the area it encloses, an open chain's the side it bends toward, a straight line's the left of its first curve as drawn; default center), thickness2?: expr (two_sides: the thickness outside); corners are mitred, crossing walls are one"),
     CommandSpec::new("solid.revolve", "Revolve", revolve)
         .at("SOLID", "CREATE")
         .icon("revolve")
@@ -118,7 +118,7 @@ pub static COMMANDS: &[CommandSpec] = &[
 /// Where an extrude starts and which way is positive: a point inside the (first) profile or
 /// face, and the unit normal.
 fn extrude_base(s: &Session, p: &Value) -> Option<(Vec3, Vec3)> {
-    if let Some(fp) = p.get("face").and_then(vec3) {
+    if let Some(fp) = p.get("face").or_else(|| p.get("faces").and_then(Value::as_array).and_then(|faces| faces.first())).and_then(vec3) {
         return Some((fp, super::face::face_normal_in(s, fp, str_(p, "face_body"))?));
     }
     let sid = feature_sketch(s, p, "Extrude").ok()?;
@@ -167,19 +167,38 @@ const START_PROBE_MM: f64 = 0.1;
 /// direction it grows, or halfway along it. With the halfway point alone, a cut dragged far
 /// past a body's far side read as a Join (#1257).
 pub fn auto_operation(s: &Session, p: &Value) -> Option<&'static str> {
-    let d = extrude_reach(s, p)?;
+    auto_operation_in(s, p, true)
+}
+
+fn auto_operation_in(s: &Session, p: &Value, world_faces: bool) -> Option<&'static str> {
     let symmetric = p.get("to").is_none() && str_(p, "direction").is_some_and(|d| d.eq_ignore_ascii_case("symmetric"));
-    let (base, n) = extrude_base(s, p)?;
-    let st = s.model.state();
+    // Imported face groups can belong to a child of an empty active component.
+    // Probe in the same coordinate frame as the face picks.
+    let grouped = p.get("faces").and_then(Value::as_array).and_then(|faces| faces.first()).and_then(vec3);
+    let st = if grouped.is_some() && world_faces { s.world_state() } else { s.model.state() };
+    let (base, n) = if let Some(point) = grouped {
+        let (mesh, index, distance, name) = super::face::face_at_state(&st, point, str_(p, "face_body")).ok().flatten()?;
+        if distance > (mesh.bounds().diagonal() * 1e-3).max(1e-3) * 10.0 {
+            return None;
+        }
+        let normal = st.body(&name)?.body.planar_face(index as usize)?.normal();
+        (point, normal)
+    } else {
+        extrude_base(s, p)?
+    };
+    let d = if grouped.is_some() && p.get("to").is_some() { (p.get("to").and_then(vec3)? - base).dot(n) } else { extrude_reach(s, p)? };
     if st.bodies.is_empty() || !d.is_finite() {
         return Some("new");
     }
-    // Only the active component's bodies take part (or the ones named as participants).
+    // Match the evaluator's implicit participants: a grouped cut from an empty
+    // assembly component considers every body; otherwise keep the active scope.
+    // Explicit participants override either default.
     let parts = string_list(p, "participants");
+    let implicit_all = grouped.is_some() && !st.bodies.iter().any(|body| s.doc.model_body_component(body) == s.active_component);
     let bodies: Vec<_> = st
         .bodies
         .iter()
-        .filter(|b| if parts.is_empty() { s.doc.model_body_component(b) == s.active_component } else { parts.contains(&b.name) })
+        .filter(|b| if parts.is_empty() { implicit_all || s.doc.model_body_component(b) == s.active_component } else { parts.contains(&b.name) })
         .collect();
     if bodies.is_empty() {
         return Some("new");
@@ -470,7 +489,8 @@ fn add_feature_in(s: &mut Session, p: &Value, kind: FeatureKind, world: bool) ->
     // takes part in every body instead, which it changes only where it meets them.
     let participants = if participants.is_empty()
         && !primitive
-        && matches!(str_(p, "operation").and_then(Operation::parse), Some(Operation::Cut | Operation::Intersect))
+        && (matches!(str_(p, "operation").and_then(Operation::parse), Some(Operation::Cut | Operation::Intersect))
+            || p.get("faces").is_some() && matches!(&kind, FeatureKind::Extrude { operation: Operation::Cut | Operation::Intersect, .. }))
         && {
             let st = s.model.state();
             !st.bodies.is_empty() && !st.bodies.iter().any(|b| s.doc.model_body_component(b) == s.active_component)
@@ -545,13 +565,31 @@ fn add_feature_in(s: &mut Session, p: &Value, kind: FeatureKind, world: bool) ->
 
 fn extrude(s: &mut Session, p: &Value) -> Result<Value> {
     let cmd = "solid.extrude";
+    let grouped = if let Some(value) = p.get("faces") {
+        if p.get("face").is_some() || p.get("sketch").is_some() || p.get("profiles").is_some() {
+            return Err(bad(cmd, "faces cannot be combined with face, sketch or profiles"));
+        }
+        let faces = value
+            .as_array()
+            .filter(|faces| !faces.is_empty() && faces.len() <= 1024)
+            .ok_or_else(|| bad(cmd, "faces must contain between 1 and 1024 points"))?;
+        let points = faces.iter().map(|point| vec3(point).ok_or_else(|| bad(cmd, "faces must be points [x,y,z]"))).collect::<Result<Vec<_>>>()?;
+        let (id, points, body) = super::face::sketch_of_faces(s, &points, cmd, str_(p, "face_body"))?;
+        Some((id, Some(ProfileSel::Points { points }), Some(body)))
+    } else {
+        None
+    };
     // A planar body face extrudes like a profile: its boundary is copied into a sketch on it.
-    let (sketch, face_profile, face_body) = match p.get("face").and_then(vec3) {
-        Some(fp) => {
-            let (id, inside, body) = super::face::sketch_of_face(s, fp, cmd, str_(p, "face_body"))?;
-            (id, Some(ProfileSel::Points { points: vec![inside] }), Some(body))
+    let (sketch, face_profile, face_body) = if let Some(grouped) = grouped {
+        grouped
+    } else {
+        match p.get("face").and_then(vec3) {
+            Some(fp) => {
+                let (id, inside, body) = super::face::sketch_of_face(s, fp, cmd, str_(p, "face_body"))?;
+                (id, Some(ProfileSel::Points { points: vec![inside] }), Some(body))
+            }
+            None => (feature_sketch(s, p, cmd)?, None, None),
         }
-        None => (feature_sketch(s, p, cmd)?, None, None),
     };
     let extent = extent_param(s, p, cmd)?;
     let thin = match bool_(p, "thin") {
@@ -565,7 +603,7 @@ fn extrude(s: &mut Session, p: &Value) -> Result<Value> {
         _ => None,
     };
     let operation = match str_(p, "operation") {
-        Some(o) if o.eq_ignore_ascii_case("auto") => Operation::parse(auto_operation(s, p).unwrap_or("new")).unwrap_or(Operation::NewBody),
+        Some(o) if o.eq_ignore_ascii_case("auto") => Operation::parse(auto_operation_in(s, p, false).unwrap_or("new")).unwrap_or(Operation::NewBody),
         _ => operation(p, cmd)?,
     };
     let mut targets = string_list(p, "targets");

crates/engine/src/cmd/features_more_tests.rs

@@ -2,6 +2,63 @@ use serde_json::{Value, json};
 
 use crate::Session;
 
+#[test]
+fn grouped_face_auto_operation_keeps_implicit_and_explicit_participants() {
+    let mut s = Session::default();
+    let part = run(&mut s, "component.create", json!({"name":"Part"}));
+    run(&mut s, "solid.box", json!({"length":10,"width":10,"height":10,"body_name":"Stock"}));
+    run(&mut s, "component.activate", json!({"component":0}));
+    for offset in [0., 30.] {
+        if offset != 0. {
+            run(&mut s, "occurrence.move", json!({"occurrence":part["occurrence"],"translate":[offset,0,0]}));
+        }
+        // To Object follows the target's side, even when the distance and
+        // direction fields still describe the opposite extrusion.
+        for (height, expected) in [(8., "cut"), (12., "join")] {
+            let params = json!({"faces":[[offset+2.,2,10],[offset+8.,8,10]],"face_body":"Stock",
+                "to":[offset+5.,5,height],"direction":"negative"});
+            assert_eq!(crate::auto_operation(&s, &params), Some(expected));
+        }
+        for distance in [-2., 2.] {
+            let mut params = json!({"faces":[[offset+2.,2,10],[offset+8.,8,10]],"distance":distance});
+            let expected = if distance < 0. { "cut" } else { "join" };
+            assert_eq!(crate::auto_operation(&s, &params), Some(expected));
+            params["face_body"] = json!("Stock");
+            assert_eq!(crate::auto_operation(&s, &params), Some(expected));
+            let mut actual = s.scratch();
+            if offset != 0. {
+                run(&mut actual, "component.activate", json!({"component":part["component"]}));
+            }
+            params["operation"] = json!("auto");
+            let made = run(&mut actual, "solid.extrude", params);
+            let body = actual.model.state().body("Stock").unwrap().body.clone();
+            let volume = solidcraft_kernel::measure(&body).unwrap().volume;
+            assert!(
+                (volume - (1000. + 100. * distance)).abs() < 1e-6,
+                "offset={offset}, distance={distance}, volume={volume}, feature={:?}",
+                actual.doc.feature(made["feature"].as_u64().unwrap())
+            );
+        }
+        if offset != 0. {
+            // Outside the edited component, grouping keeps the original explicit
+            // face command's coordinate and participant behavior.
+            let mut grouped = s.scratch();
+            let mut single = s.scratch();
+            run(&mut grouped, "solid.extrude", json!({"faces":[[32,2,10],[38,8,10]],"face_body":"Stock","distance":-2,"operation":"cut"}));
+            run(&mut single, "solid.extrude", json!({"face":[32,2,10],"face_body":"Stock","distance":-2,"operation":"cut"}));
+            let volume = |session: &Session| solidcraft_kernel::measure(&session.model.state().body("Stock").unwrap().body).unwrap().volume;
+            assert!((volume(&grouped) - volume(&single)).abs() < 1e-6);
+        }
+    }
+    run(&mut s, "solid.box", json!({"corner":[100,0,0],"length":10,"width":10,"height":10,"body_name":"Other"}));
+    let mut params = json!({"faces":[[32,2,10],[38,8,10]],"face_body":"Stock","distance":-2});
+    assert_eq!(crate::auto_operation(&s, &params), Some("join"), "an existing active-component body keeps its original participant scope");
+    params["participants"] = json!(["Stock"]);
+    assert_eq!(crate::auto_operation(&s, &params), Some("cut"));
+    params["participants"] = json!(["Other"]);
+    assert_eq!(crate::auto_operation(&s, &params), Some("join"));
+}
+
 fn run(s: &mut Session, id: &str, p: Value) -> Value {
     match s.execute(id, &p) {
         Ok(v) => v,
@@ -28,6 +85,43 @@ fn volume(s: &mut Session) -> f64 {
     measure(s)["total"]["volume_mm3"].as_f64().unwrap_or(f64::NAN)
 }
 
+#[test]
+fn separated_profile_cut_preserves_participants_and_removes_only_consumed_bodies() {
+    for explicit in [false, true] {
+        let mut s = Session::default();
+        for (name, x) in [("A", 0), ("B", 10), ("C", 30)] {
+            run(&mut s, "solid.box", json!({"length":5,"width":5,"height":10,"corner":[x,0,0],"body_name":name}));
+        }
+        run(&mut s, "sketch.create", json!({"plane":"XY","name":"Cutters"}));
+        for (a, b) in [([-1, -1], [6, 6]), ([12, 2], [14, 4]), ([32, 2], [34, 4])] {
+            run(&mut s, "sketch.rectangle.two_point", json!({"p0":a,"p1":b}));
+        }
+        run(&mut s, "sketch.finish", json!({}));
+        let before = s.doc.to_json();
+        let mut params = json!({"sketch":"Cutters","profiles":"all","distance":10,"operation":"cut"});
+        if explicit {
+            params["participants"] = json!(["A", "B"]);
+        }
+        run(&mut s, "solid.extrude", params);
+        let check = |session: &Session| {
+            let state = session.model.state();
+            assert_eq!(state.bodies.len(), 2);
+            assert!(state.body("A").is_none());
+            for (name, expected) in [("B", 210.), ("C", if explicit { 250. } else { 210. })] {
+                let body = &state.body(name).unwrap().body;
+                assert!((solidcraft_kernel::measure(body).unwrap().volume - expected).abs() < 1e-6);
+                assert!(body.validity().is_empty());
+            }
+        };
+        check(&s);
+        check(&Session::new(solidcraft_doc::Document::from_json(&s.doc.to_json()).unwrap()));
+        run(&mut s, "edit.undo", json!({}));
+        assert_eq!(s.doc.to_json(), before);
+        run(&mut s, "edit.redo", json!({}));
+        check(&s);
+    }
+}
+
 fn rel(a: f64, b: f64) -> f64 {
     (a - b).abs() / b.abs().max(1e-12)
 }

crates/engine/src/cmd/sketch_project.rs

@@ -520,21 +520,34 @@ pub(super) fn snap_points(s: &mut Session, p: &Value, cmd: &str) -> Result<Value
 /// Private compatibility projection for generated face profiles. Named legacy links follow
 /// edits, but cannot provide the construction certificate required by public attachments.
 pub(super) fn project_internal_face(s: &mut Session, id: u64, body: &str, index: usize) -> Result<String> {
+    project_internal_faces(s, id, body, &[index])?.pop().ok_or_else(|| bad("face profile", "empty face projection"))
+}
+
+/// Capture individual replay names together, against the same unchanged source body.
+pub(super) fn project_internal_faces(s: &mut Session, id: u64, body: &str, indices: &[usize]) -> Result<Vec<String>> {
+    if indices.len() > 1024 {
+        return Err(bad("face profile", "too many faces"));
+    }
     let mut doc = (*s.doc).clone();
     let raw = s.model.state_before(id);
     let component = doc.feature(id).map(|feature| feature.component).unwrap_or(0);
     let state = solidcraft_doc::state_in_frame_at(&doc, &raw, component, owner_frame(s, &doc, component));
     let plane = sketch_plane(&doc, id, &state)?;
-    let resolved = solidcraft_doc::project::resolve_face_indices(&state, &plane, LinkKind::Project, body, &[index])?;
-    let face_name = state.body(body).and_then(|body| solidcraft_doc::naming::face_names(body).get(index).cloned());
+    let names = state.body(body).map(solidcraft_doc::naming::face_names).unwrap_or_default();
+
     let mut sk = doc.sketch(id)?.clone();
-    let link = sk.add_link_with_wires(LinkKind::Project, resolved.source, &resolved.geom, &resolved.wires)?;
-    if let Some(entry) = sk.links.iter_mut().find(|entry| entry.id == link) {
-        entry.face_name = face_name;
+    let mut links = Vec::with_capacity(indices.len());
+    for &index in indices {
+        let resolved = solidcraft_doc::project::resolve_face_indices(&state, &plane, LinkKind::Project, body, &[index])?;
+        let link = sk.add_link_with_wires(LinkKind::Project, resolved.source, &resolved.geom, &resolved.wires)?;
+        if let Some(entry) = sk.links.iter_mut().find(|entry| entry.id == link) {
+            entry.face_name = names.get(index).cloned();
+        }
+        links.push(link);
     }
     *doc.sketch_mut(id)? = sk;
     *s.doc_mut() = doc;
-    Ok(link)
+    Ok(links)
 }
 
 /// Project the edges of the face a new sketch was created on (Fusion's default).

crates/engine/src/frames.rs

@@ -46,7 +46,9 @@ use K::*;
 /// The parameters each command takes in world coordinates.
 fn table(id: &str) -> &'static [(&'static str, K)] {
     match id {
-        "solid.extrude" => &[("face", Pick), ("face_body", Body), ("from", Make), ("to", Make), ("targets", Body), ("participants", Body)],
+        "solid.extrude" => {
+            &[("face", Pick), ("faces", Picks), ("face_body", Body), ("from", Make), ("to", Make), ("targets", Body), ("participants", Body)]
+        }
         "solid.revolve" => &[("face", Pick), ("axis", Axis), ("to", Make), ("targets", Body), ("participants", Body)],
         "solid.box" | "solid.sphere" => &[("corner", Make), ("center", Make)],
         "solid.cylinder" | "solid.coil" | "solid.torus" => &[("base", Make), ("center", Make), ("axis", Dir)],

crates/engine/src/tests/robustness_goldens.rs

@@ -54,6 +54,24 @@ fn differs(want: &Value, got: &Value) -> Option<String> {
     (!out.is_empty()).then(|| out.join("; "))
 }
 
+/// Platform records only override the seeds explicitly verified on that platform.
+fn expected<'a>(file: &'a Value, seed: u64, platform: &str) -> &'a Value {
+    let key = seed.to_string();
+    file.get("platforms")
+        .and_then(|platforms| platforms.get(platform))
+        .and_then(|record| record.get("seeds"))
+        .and_then(|seeds| seeds.get(&key))
+        .unwrap_or(&file["seeds"][key])
+}
+
+#[test]
+fn platform_records_keep_shared_references_for_every_other_seed_and_platform() {
+    let file = json!({"seeds":{"1":{"volume":10},"2":{"volume":20}},"platforms":{"windows":{"seeds":{"1":{"volume":11}}}}});
+    assert_eq!(expected(&file, 1, "windows")["volume"], 11);
+    assert_eq!(expected(&file, 1, "linux")["volume"], 10);
+    assert_eq!(expected(&file, 2, "windows")["volume"], 20);
+}
+
 fn check(seed: u64) {
     let got: BTreeMap<u64, Value> = BTreeMap::from([(seed, fuzz::golden(seed, MAX_STEPS))]);
     let _lock = FILE.lock().unwrap_or_else(|e| e.into_inner());
@@ -61,7 +79,7 @@ fn check(seed: u64) {
     let changed: Vec<(u64, String)> = got
         .iter()
         .filter_map(|(seed, g)| {
-            let w = &file["seeds"][seed.to_string()];
+            let w = expected(&file, *seed, std::env::consts::OS);
             if w.is_null() { Some((*seed, "new".to_string())) } else { differs(w, g).map(|d| (*seed, d)) }
         })
         .collect();
@@ -75,20 +93,34 @@ fn check(seed: u64) {
                 "What each robustness seed builds (crates/engine/src/tests/robustness_goldens.rs, docs/robustness.md). Record changes with ROBUSTNESS_GOLDENS_BLESS=\"why\"."
             );
         }
+        let platform = std::env::consts::OS;
+        let platform_record = file["platforms"][platform]["seeds"].is_object();
         for (seed, g) in &got {
-            file["seeds"][seed.to_string()] = g.clone();
+            if platform_record {
+                if changed.iter().any(|(changed, _)| changed == seed) {
+                    file["platforms"][platform]["seeds"][seed.to_string()] = g.clone();
+                }
+            } else {
+                file["seeds"][seed.to_string()] = g.clone();
+            }
         }
         let mut notes = file["notes"].as_array().cloned().unwrap_or_default();
         let seeds: Vec<u64> = changed.iter().map(|(s, _)| *s).collect();
         // The parts of one record (the tests run side by side) share one note.
         match notes.last_mut() {
-            Some(last) if last["reason"] == json!(reason) => {
+            Some(last) if last["reason"] == json!(reason) && (!platform_record || last["platform"] == json!(platform)) => {
                 let mut all: Vec<u64> = last["seeds"].as_array().into_iter().flatten().filter_map(Value::as_u64).chain(seeds).collect();
                 all.sort_unstable();
                 all.dedup();
                 last["seeds"] = json!(all);
             }
-            _ => notes.push(json!({"reason": reason, "seeds": seeds})),
+            _ => {
+                let mut note = json!({"reason": reason, "seeds": seeds});
+                if platform_record {
+                    note["platform"] = json!(platform);
+                }
+                notes.push(note);
+            }
         }
         file["notes"] = Value::Array(notes);
         // Seeds in order, one per line, so a change is a small diff.
@@ -100,7 +132,11 @@ fn check(seed: u64) {
             s += &format!("  \"{k}\": {}{}\n", v, if i + 1 < n { "," } else { "" });
         }
         let notes: Vec<String> = file["notes"].as_array().into_iter().flatten().map(|n| format!("  {n}")).collect();
-        s += &format!(" }},\n \"notes\": [\n{}\n ]\n}}\n", notes.join(",\n"));
+        s += " },\n";
+        if let Some(platforms) = file.get("platforms") {
+            s += &format!(" \"platforms\": {platforms},\n");
+        }
+        s += &format!(" \"notes\": [\n{}\n ]\n}}\n", notes.join(",\n"));
         std::fs::write(path(), s).unwrap_or_else(|e| panic!("{}: {e}", path().display()));
         return;
     }

crates/kernel/src/body.rs

@@ -1494,6 +1494,33 @@ impl Body {
         shell_groups::meshes_meet(&a, &b, 2.0 * tol)
     }
 
+    /// The same contact test for several tools, reusing this unchanged body's
+    /// fine mesh at each required tolerance. No contact threshold is relaxed.
+    pub fn meets_each(&self, others: &[Body]) -> Result<Vec<bool>> {
+        if others.len() > 1024 {
+            return Err(KernelError::Invalid("too many contact tools".into()));
+        }
+        self.require_brep("contact test")?;
+        let size = self.size();
+        let mut meshes = std::collections::HashMap::new();
+        let mut contacts = Vec::with_capacity(others.len());
+        for other in others {
+            other.require_brep("contact test")?;
+            let tol = (size.max(other.size()) * 1e-4).max(1e-6);
+            let key = tol.to_bits();
+            if !meshes.contains_key(&key) {
+                // Bound retained meshes even when hostile inputs request many tolerances.
+                if meshes.len() == 16 {
+                    meshes.clear();
+                }
+                meshes.insert(key, self.tessellate(tol)?);
+            }
+            let mesh = meshes.get(&key).ok_or_else(|| KernelError::Internal("contact mesh disappeared".into()))?;
+            contacts.push(shell_groups::meshes_meet(mesh, &other.tessellate(tol)?, 2.0 * tol)?);
+        }
+        Ok(contacts)
+    }
+
     /// A boolean shortcut needs clearance larger than both shell mesh deflections.
     pub(crate) fn separated_lumps(&self) -> Result<Vec<Body>> {
         self.lumps_with_clearance(4.0 * (self.size() * 1e-3).max(1e-3))

crates/kernel/src/coplanar.rs

@@ -1193,10 +1193,18 @@ pub(crate) fn imprint_union(a: &Body, b: &Body, accept: &dyn Fn(&Body) -> bool)
 /// faces): every such pair of faces goes and the shells are stitched along their edges. `None`
 /// when no such pair of faces exists.
 pub(crate) fn glue(a: &Body, b: &Body) -> Option<Result<Body>> {
+    glue_impl(a, b, false)
+}
+
+/// Glue every certified start cap, retaining each tool's original contact tolerance.
+pub(crate) fn glue_all_caps(a: &Body, b: &Body) -> Option<Result<Body>> {
+    glue_impl(a, b, true)
+}
+
+fn glue_impl(a: &Body, b: &Body, all_caps: bool) -> Option<Result<Body>> {
     use mt::{BoundedCurve, ParametricCurve};
     let size = a.size().max(b.size());
     let tol = (size * 1e-7).max(1e-9) * 10.0;
-    let key = |p: Vec3| ((p.x / tol).round() as i64, (p.y / tol).round() as i64, (p.z / tol).round() as i64);
     let mid = |e: &mt::Edge| {
         let c = e.curve();
         let (t0, t1) = c.range_tuple();
@@ -1205,14 +1213,40 @@ pub(crate) fn glue(a: &Body, b: &Body) -> Option<Result<Body>> {
     // Matching faces: same plane, opposite normals, the same edges. Every pair is glued: a
     // pair left behind would stay inside the result as a zero-thickness slit (issue #616).
     let (pa, pb) = (planes(a), planes(b));
+    let mut tool_sizes = HashMap::new();
+    if all_caps {
+        for shell in b.solid.boundaries() {
+            let mut bounds = solidcraft_geom::Aabb3::EMPTY;
+            for vertex in shell.vertex_iter() {
+                bounds.add(from_p3(vertex.point()));
+            }
+            let size = bounds.diagonal();
+            if !size.is_finite() {
+                return None;
+            }
+            for face in shell.face_iter() {
+                tool_sizes.insert(face.id(), size);
+            }
+        }
+    }
     let fa_list: Vec<&mt::Face> = a.solid.face_iter().collect();
     let fb_list: Vec<&mt::Face> = b.solid.face_iter().collect();
     // B edge → the matching A edge; B vertex → the matching A vertex.
     let mut map: HashMap<mt::EdgeID, mt::Edge> = HashMap::new();
     let mut vmap: HashMap<mt::VertexID, mt::Vertex> = HashMap::new();
     let (mut glued_a, mut glued_b): (Vec<usize>, Vec<usize>) = (Vec::new(), Vec::new());
+    if all_caps && pa.len().saturating_mul(pb.len()) > 2_000_000 {
+        return None;
+    }
     for (ia, x) in &pa {
         for (ib, y) in &pb {
+            if all_caps
+                && !matches!(b.face_sources().and_then(|sources| sources.get(*ib)), Some(Some(crate::FaceSource::ExtrudeCap { high: false, .. })))
+            {
+                continue;
+            }
+            let tol = if all_caps { (a.size().max(*tool_sizes.get(&fb_list.get(*ib)?.id())?) * 1e-7).max(1e-9) * 10.0 } else { tol };
+            let key = |p: Vec3| ((p.x / tol).round() as i64, (p.y / tol).round() as i64, (p.z / tol).round() as i64);
             if glued_a.contains(ia) || glued_b.contains(ib) || x.n.dot(y.n) > -1.0 + 1e-9 || (x.d + y.d).abs() > tol {
                 continue;
             }
@@ -1264,6 +1298,14 @@ pub(crate) fn glue(a: &Body, b: &Body) -> Option<Result<Body>> {
             glued_b.push(*ib);
         }
     }
+    if all_caps
+        && b.face_sources()?
+            .iter()
+            .enumerate()
+            .any(|(index, source)| matches!(source, Some(crate::FaceSource::ExtrudeCap { high: false, .. })) && !glued_b.contains(&index))
+    {
+        return None;
+    }
     if glued_a.is_empty() {
         return None;
     }

crates/kernel/src/lib.rs

@@ -175,7 +175,10 @@ pub use mesh_convert::convert_prismatic_mesh;
 pub use meshbody::{MAX_TRIANGLES, mesh_body};
 pub use native::{decode_native_body, encode_native_body, native_preview_mesh};
 pub use offset::with_same_surface;
-pub use ops::{BoolOp, boolean, can_join_touching_faces, half_space, join_apart, split_by_plane, transform, transform_matrix, union_apart};
+pub use ops::{
+    BoolOp, boolean, can_join_all_touching_faces, can_join_touching_faces, compound_disjoint_extrusions, half_space, is_planar, join_apart,
+    split_by_plane, transform, transform_matrix, union_apart,
+};
 pub use polybool::{faceted_boolean, planar_boolean};
 pub use polyhedron::{HalfSpace, convex_polyhedron, draft, offset_faces, shell};
 pub use prism::{PLANAR_FIT_TOL, extrude_planar_regions, planar_regions_boolean};

crates/kernel/src/ops.rs

@@ -23,12 +23,167 @@ pub enum BoolOp {
     Intersect,
 }
 
+/// Exact planar Booleans need no sampled enlargement of their tool footprint.
+pub fn is_planar(body: &Body) -> bool {
+    if body.is_mesh() || body.face_count() > 16_384 {
+        return false;
+    }
+    guard("planar body", || Ok(body.solid.face_iter().all(|face| matches!(face.oriented_surface(), mt::Surface::Plane(_))))).unwrap_or(false)
+}
+
+/// Batch separated extrusion tools without repeatedly unioning an ever-growing target.
+/// Construction caps provide conservative bounds, including the full circle of each arc;
+/// unsupported or touching tools retain the caller's sequential Boolean path.
+pub fn compound_disjoint_extrusions(tools: &[Body]) -> Result<Option<Body>> {
+    if tools.len() < 2 || tools.len() > 1024 {
+        return Ok(None);
+    }
+    guard("compound extrusion tools", || {
+        let mut bounds = Vec::with_capacity(tools.len());
+        let mut corners = Vec::with_capacity(tools.len());
+        let mut axes = Vec::with_capacity(tools.len());
+        let mut remaining = 16_384usize;
+        for tool in tools {
+            let Some(sources) = tool.face_sources() else { return Ok(None) };
+            if sources.len() != tool.face_count() {
+                return Ok(None);
+            }
+            let mut bb = solidcraft_geom::Aabb3::EMPTY;
+            let mut points = Some(Vec::new());
+            let mut directions = Vec::new();
+            let mut caps = 0;
+            for source in sources {
+                let Some(left) = remaining.checked_sub(1) else { return Ok(None) };
+                remaining = left;
+                match source {
+                    Some(crate::FaceSource::ExtrudeCap { region, plane, high }) => {
+                        caps += 1;
+                        // The bottom support is outward-facing, but its region retains
+                        // the original sketch coordinates (see build::extrude).
+                        let plane = if *high { *plane } else { solidcraft_geom::Plane { y: -plane.y, ..*plane } };
+                        for segment in &region.outer.segs {
+                            let Some(left) = remaining.checked_sub(1) else { return Ok(None) };
+                            remaining = left;
+                            match *segment {
+                                solidcraft_geom::Seg2::Line { a, b } => {
+                                    let (a, b) = (plane.to_world(a), plane.to_world(b));
+                                    bb.add(a);
+                                    bb.add(b);
+                                    if let Some(points) = points.as_mut() {
+                                        points.extend([a, b]);
+                                    }
+                                    if let Some(axis) = (b - a).cross(plane.normal()).normalized() {
+                                        directions.push(axis);
+                                    }
+                                }
+                                solidcraft_geom::Seg2::Arc { center, radius, .. } => {
+                                    points = None;
+                                    for x in [-radius, radius] {
+                                        for y in [-radius, radius] {
+                                            bb.add(plane.to_world(center + solidcraft_geom::Vec2::new(x, y)));
+                                        }
+                                    }
+                                }
+                                _ => return Ok(None),
+                            }
+                        }
+                    }
+                    Some(crate::FaceSource::ExtrudeSide { .. }) => {}
+                    _ => return Ok(None),
+                }
+            }
+            if caps != 2 || bb.is_empty() || !bb.min.is_finite() || !bb.max.is_finite() {
+                return Ok(None);
+            }
+            bounds.push(bb);
+            corners.push(points);
+            axes.push(directions);
+        }
+        let mut remaining_separation_work = 16_000_000usize;
+        for (i, a) in bounds.iter().enumerate() {
+            for (j, b) in bounds.iter().enumerate().skip(i + 1) {
+                let gap = (a.diagonal().max(b.diagonal()) * 1e-6).max(1e-7);
+                let separated = a.max.x + gap < b.min.x
+                    || b.max.x + gap < a.min.x
+                    || a.max.y + gap < b.min.y
+                    || b.max.y + gap < a.min.y
+                    || a.max.z + gap < b.min.z
+                    || b.max.z + gap < a.min.z;
+                if separated {
+                    continue;
+                }
+                let (Some(Some(x)), Some(Some(y))) = (corners.get(i), corners.get(j)) else { return Ok(None) };
+                let Some(origin) = x.first() else { return Ok(None) };
+                // Every straight extrusion lies inside the hull of its cap corners.
+                // A separating cap-edge axis therefore proves clearance even when
+                // rotated tools' world-coordinate boxes overlap. Arcs retain the box test.
+                let range = |points: &[Vec3], axis: Vec3| {
+                    points.iter().map(|p| (*p - *origin).dot(axis)).fold((f64::INFINITY, f64::NEG_INFINITY), |(lo, hi), v| (lo.min(v), hi.max(v)))
+                };
+                let rounding = origin.x.abs().max(origin.y.abs()).max(origin.z.abs()) * f64::EPSILON * 128.0;
+                let separated = axes.get(i).into_iter().flatten().chain(axes.get(j).into_iter().flatten()).any(|axis| {
+                    let Some(left) = remaining_separation_work.checked_sub(x.len().saturating_add(y.len())) else { return false };
+                    remaining_separation_work = left;
+                    let (a, b) = (range(x, *axis), range(y, *axis));
+                    a.1 + gap + rounding < b.0 || b.1 + gap + rounding < a.0
+                });
+                if !separated {
+                    return Ok(None);
+                }
+            }
+        }
+        let sources: std::collections::HashMap<_, _> = tools
+            .iter()
+            .flat_map(|tool| {
+                tool.solid
+                    .face_iter()
+                    .zip(tool.face_sources().unwrap_or_default())
+                    .map(|(face, source)| (face.id(), (face.orientation(), source.clone())))
+            })
+            .collect();
+        let operands: Vec<_> = tools.iter().collect();
+        let shells = tools.iter().flat_map(|tool| tool.solid.boundaries().clone()).collect();
+        let solid = Solid::try_new(shells).map_err(|error| KernelError::Failed(format!("extrusion compound: {error}")))?;
+        let faces = tools
+            .iter()
+            .enumerate()
+            .flat_map(|(operand, tool)| (0..tool.face_count()).map(move |face| record::from_face(operand, face, crate::history::Change::Kept)))
+            .collect();
+        let mut edges = HashMap::new();
+        for (operand, tool) in tools.iter().enumerate() {
+            edges.extend(record::edge_origins(&tool.solid, operand));
+        }
+        record::build(solid, &record::counts(&operands), Some(faces), Some(&edges)).map(|mut body| {
+            body.regularization_protected = tools.iter().any(|tool| tool.regularization_protected);
+            // Only unchanged face identities carry these transient tool witnesses.
+            // No whole-compound extrusion/producer certificate is created.
+            let mapped = body
+                .solid
+                .face_iter()
+                .map(|face| {
+                    sources.get(&face.id()).filter(|(orientation, _)| *orientation == face.orientation()).and_then(|(_, source)| source.clone())
+                })
+                .collect();
+            Some(body.with_face_sources(Some(std::sync::Arc::new(mapped))))
+        })
+    })
+}
+
 /// Whether a union can sew two matching planar faces without intersecting them.
 /// Callers can retain the exact touching tool instead of extending it into material.
 pub fn can_join_touching_faces(a: &Body, b: &Body) -> bool {
     a.solid.boundaries().len() == 1 && b.solid.boundaries().len() == 1 && crate::coplanar::glue(a, b).is_some_and(|r| r.is_ok())
 }
 
+/// Check all separated extrusion starts in one construction, without rebuilding
+/// the unchanged target once for each face. Partial seams keep the ordinary path.
+pub fn can_join_all_touching_faces(a: &Body, b: &Body) -> bool {
+    if a.solid.boundaries().len() != 1 || !(2..=1024).contains(&b.solid.boundaries().len()) || a.face_count().max(b.face_count()) > 16_384 {
+        return false;
+    }
+    guard("check extrusion seams", || Ok(crate::coplanar::glue_all_caps(a, b).is_some_and(|result| result.is_ok()))).unwrap_or(false)
+}
+
 /// Shifts applied to both operands on retries. The boolean classifies some faces by casting a
 /// ray whose direction is derived from point coordinates; moving both solids (and the result
 /// back) leaves the geometry unchanged but changes those rays.
@@ -238,6 +393,97 @@ mod shortcut_tests {
         assert!((meeting_size(&thin, &thin) - 1e-5).abs() < 1e-12);
     }
 
+    #[test]
+    fn rotated_extrusion_bounds_use_exact_cap_separation_and_keep_sources() {
+        use solidcraft_geom::{Loop2, Plane, Region2, Vec2};
+        let rectangle = |angle: f64, offset: f64| {
+            let (c, s) = (angle.cos(), angle.sin());
+            Region2 {
+                outer: Loop2::polygon(
+                    &[(-2., -0.5), (2., -0.5), (2., 0.5), (-2., 0.5)].map(|(x, y)| Vec2::new(x * c - (y + offset) * s, x * s + (y + offset) * c)),
+                ),
+                holes: vec![],
+            }
+        };
+        for offset in [1.2, 1., 0.8] {
+            let tools = crate::extrude(&Plane::XY, &[rectangle(0.7, 0.), rectangle(0.7, offset)], 0., 2.).unwrap();
+            let compound = compound_disjoint_extrusions(&tools).unwrap();
+            assert_eq!(compound.is_some(), offset > 1.);
+            if let Some(compound) = compound {
+                let sources = compound.face_sources().unwrap();
+                assert_eq!(sources.len(), compound.face_count());
+                assert_eq!(sources.iter().filter(|source| matches!(source, Some(crate::FaceSource::ExtrudeCap { high: false, .. }))).count(), 2);
+                assert!(compound.validity().is_empty());
+            }
+        }
+    }
+
+    #[test]
+    fn batched_contact_test_matches_individual_tolerances() {
+        let target = crate::cylinder(Vec3::ZERO, Vec3::Z, 5., 3.).unwrap();
+        let tools = [
+            crate::box_solid(Vec3::new(-1., -1., 3.), Vec3::new(1., 1., 5.)).unwrap(),
+            crate::box_solid(Vec3::new(-1., -1., 3.002), Vec3::new(1., 1., 5.)).unwrap(),
+            crate::sphere(Vec3::new(20., 0., 1.), 1.).unwrap(),
+        ];
+        let expected = tools.iter().map(|tool| target.meets(tool).unwrap()).collect::<Vec<_>>();
+        assert_eq!(target.meets_each(&tools).unwrap(), expected);
+        assert!(target.meets_each(&[]).unwrap().is_empty());
+    }
+
+    #[test]
+    fn compound_span_does_not_relax_full_face_seam_tolerance() {
+        use solidcraft_geom::{Loop2, Plane, Region2, Vec2};
+        let mut target = crate::box_solid(Vec3::new(0., 0., -3.), Vec3::new(100., 2., -2.)).unwrap();
+        for x in [0., 98.] {
+            let boss = crate::box_solid(Vec3::new(x, 0., -2.), Vec3::new(x + 2., 2., 0.)).unwrap();
+            target = boolean(&target, &boss, BoolOp::Union).unwrap().unwrap();
+        }
+        let regions: Vec<_> = [0., 98.]
+            .into_iter()
+            .map(|x| Region2 {
+                outer: Loop2::polygon(&[Vec2::new(x, 0.), Vec2::new(x + 2., 0.), Vec2::new(x + 2., 2.), Vec2::new(x, 2.)]),
+                holes: vec![],
+            })
+            .collect();
+        let tools = crate::extrude(&Plane::XY, &regions, 0.000_105, 200.).unwrap();
+        assert!(tools.iter().all(|tool| !can_join_touching_faces(&target, tool)));
+        let compound = compound_disjoint_extrusions(&tools).unwrap().unwrap();
+        assert!(!can_join_all_touching_faces(&target, &compound));
+    }
+
+    #[test]
+    fn extrusion_compound_requires_separated_construction_bounds() {
+        use solidcraft_geom::{Loop2, Plane, Region2, Vec2};
+        let rectangle = |x: f64| Region2 {
+            outer: Loop2::polygon(&[Vec2::new(x, 0.0), Vec2::new(x + 2.0, 0.0), Vec2::new(x + 2.0, 2.0), Vec2::new(x, 2.0)]),
+            holes: vec![],
+        };
+        let plane = Plane::from_normal(Vec3::new(100.0, -20.0, 8.0), Vec3::new(1.0, 2.0, 3.0)).unwrap();
+        let tools = crate::extrude(&plane, &[rectangle(0.0), rectangle(20.0)], -1.0, 5.0).unwrap();
+        let compound = compound_disjoint_extrusions(&tools).unwrap().unwrap();
+        assert_eq!(compound.shell_count(), 2);
+        assert_eq!(compound.history().unwrap().operands, 2);
+        assert!((crate::measure(&compound).unwrap().volume - 48.0).abs() < 1e-8);
+        assert!(compound.validity().is_empty());
+        for x in [1.0, 2.0, 2.000_000_1] {
+            let touching = crate::extrude(&solidcraft_geom::Plane::XY, &[rectangle(0.0), rectangle(x)], 0.0, 5.0).unwrap();
+            assert!(compound_disjoint_extrusions(&touching).unwrap().is_none());
+        }
+        let unsupported = [crate::sphere(Vec3::ZERO, 1.0).unwrap(), crate::sphere(Vec3::new(10.0, 0.0, 0.0), 1.0).unwrap()];
+        assert!(compound_disjoint_extrusions(&unsupported).unwrap().is_none());
+    }
+
+    #[test]
+    fn extrusion_compound_includes_arc_extrema_between_seam_vertices() {
+        use solidcraft_geom::{Loop2, Plane, Region2, Vec2};
+        let circle = |x| Region2 { outer: Loop2::circle(Vec2::new(x, 0.0), 2.0), holes: vec![] };
+        let separated = crate::extrude(&Plane::XY, &[circle(0.0), circle(8.0)], 0.0, 5.0).unwrap();
+        assert!(compound_disjoint_extrusions(&separated).unwrap().is_some());
+        let overlapping = crate::extrude(&Plane::XY, &[circle(0.0), circle(3.0)], 0.0, 5.0).unwrap();
+        assert!(compound_disjoint_extrusions(&overlapping).unwrap().is_none());
+    }
+
     #[test]
     fn curved_near_contact_never_uses_a_shell_only_boolean_candidate() {
         let direction = Vec3::new(1.0, 2.0, 3.0).normalized().unwrap();
@@ -756,14 +1002,13 @@ fn boolean_whole_with_refinement(a: &Body, b: &Body, op: BoolOp, refine: bool) -
         }
     }
     // Bodies touching along one whole face (a part joined with its mirror image).
-    if op == BoolOp::Union
-        && a.solid.boundaries().len() == 1
-        && b.solid.boundaries().len() == 1
-        && let Some(Ok(body)) = crate::coplanar::glue(a, b)
-    {
-        let (ok, _) = check(&body);
-        if ok {
-            return Ok(Some(body));
+    if op == BoolOp::Union && a.solid.boundaries().len() == 1 {
+        let glued = if b.solid.boundaries().len() == 1 { crate::coplanar::glue(a, b) } else { crate::coplanar::glue_all_caps(a, b) };
+        if let Some(Ok(body)) = glued {
+            let (ok, _) = check(&body);
+            if ok {
+                return Ok(Some(body));
+            }
         }
     }
     // Bores on a common cylinder (a pad's bore around the hole it is joined over, a disc filling

crates/kernel/src/prism.rs

@@ -181,8 +181,8 @@ pub fn extrude_planar_regions(plane: &Plane, regions: &[Region2], start: f64, en
                         remaining_pairs = remaining_pairs
                             .checked_sub(1)
                             .ok_or_else(|| KernelError::Invalid("planar extrusion separation exceeds its work budget".into()))?;
-                        let endpoints_touch = [s.start(), s.end()].iter().any(|p| t.point_at(t.closest_param(*p)).dist(*p) <= 1e-7)
-                            || [t.start(), t.end()].iter().any(|p| s.point_at(s.closest_param(*p)).dist(*p) <= 1e-7);
+                        let endpoints_touch = [s.start(), s.end()].iter().any(|p| t.point_at(closest_param(t, *p)).dist(*p) <= 1e-7)
+                            || [t.start(), t.end()].iter().any(|p| s.point_at(closest_param(s, *p)).dist(*p) <= 1e-7);
                         if endpoints_touch || !crossings(s, t, 1e-7).is_empty() {
                             return Err(KernelError::Invalid("planar material pieces touch at a boundary".into()));
                         }
@@ -765,7 +765,7 @@ fn heights_of(b: &Body, plane: &Plane) -> (f64, f64) {
 /// Does `s` run along `t` from end to end? Two lines, `s`'s ends on `t`; two arcs of one
 /// circle, `s`'s ends and middle on `t`.
 fn runs_along(s: &Seg2, t: &Seg2, tol: f64) -> bool {
-    let on = |p: Vec2| t.point_at(t.closest_param(p)).dist(p) < tol;
+    let on = |p: Vec2| t.point_at(closest_param(t, p)).dist(p) < tol;
     match (*s, *t) {
         (Seg2::Line { .. }, Seg2::Line { .. }) => on(s.start()) && on(s.end()),
         (Seg2::Arc { center: c, radius: r, .. }, Seg2::Arc { center: d, radius: q, .. }) => {
@@ -840,7 +840,7 @@ fn crossings(s: &Seg2, t: &Seg2, tol: f64) -> Vec<(f64, f64)> {
     }
     let mut out = Vec::new();
     for p in pts {
-        let (u, v) = (s.closest_param(p), t.closest_param(p));
+        let (u, v) = (closest_param(s, p), closest_param(t, p));
         if s.point_at(u).dist(p) < tol && t.point_at(v).dist(p) < tol {
             out.push((u, v));
         }
@@ -871,7 +871,7 @@ fn inside_loop(lp: &Loop2, p: Vec2) -> bool {
         }
     }
     // A point on the loop keeps the half-open answer.
-    if lp.segs.iter().any(|s| s.point_at(s.closest_param(p)).dist(p) < scale * 1e-9) {
+    if lp.segs.iter().any(|s| s.point_at(closest_param(s, p)).dist(p) < scale * 1e-9) {
         return inside_loop_ray(lp, p);
     }
     let grazes = |q: Vec2| {
@@ -991,12 +991,43 @@ fn inside(regions: &[Region2], p: Vec2) -> bool {
     regions.iter().any(|r| inside_loop(&r.outer, p) && !r.holes.iter().any(|h| inside_loop(h, p)))
 }
 
+/// Call only after proving the point is at least `tol` from the other boundary.
+/// This sub-tolerance interior probe cannot cross that boundary, and avoids casting
+/// exactly through fitted arc/line endpoints whose heights differ by roundoff.
+fn inside_clear(regions: &[Region2], point: Vec2, tol: f64) -> bool {
+    inside(regions, point + Vec2::new(tol * 0.173, tol * 0.317))
+}
+
+/// Analytic projections avoid iterative searches at every planar boundary probe.
+/// Other curve types keep the shared solver introduced on main.
+fn closest_param(segment: &Seg2, point: Vec2) -> f64 {
+    match *segment {
+        Seg2::Line { a, b } => {
+            let direction = b - a;
+            let length2 = direction.dot(direction);
+            if length2 > 1e-300 && length2.is_finite() { ((point - a).dot(direction) / length2).clamp(0.0, 1.0) } else { 0.0 }
+        }
+        Seg2::Arc { center, radius, start, sweep } if radius > 0.0 && sweep.abs() > 1e-12 && sweep.abs() <= std::f64::consts::TAU + 1e-9 => {
+            let offset = point - center;
+            let delta = ((offset.y.atan2(offset.x) - start) * sweep.signum()).rem_euclid(std::f64::consts::TAU);
+            if delta <= sweep.abs() {
+                (delta / sweep.abs()).clamp(0.0, 1.0)
+            } else if segment.start().dist(point) <= segment.end().dist(point) {
+                0.0
+            } else {
+                1.0
+            }
+        }
+        _ => segment.closest_param(point),
+    }
+}
+
 fn dist_to(regions: &[Region2], p: Vec2) -> f64 {
     regions
         .iter()
         .flat_map(|r| std::iter::once(&r.outer).chain(&r.holes))
         .flat_map(|l| l.segs.iter())
-        .map(|s| s.point_at(s.closest_param(p)).dist(p))
+        .map(|s| s.point_at(closest_param(s, p)).dist(p))
         .fold(f64::INFINITY, f64::min)
 }
 
@@ -1043,7 +1074,7 @@ fn box_holds(b: Option<SegBox>, p: Vec2) -> bool {
 /// Distance from `p` to the nearest of `segs` whose box holds it: infinite when none does (no
 /// segment is within the tolerance of `p` then).
 fn near_dist(segs: &[Seg2], boxes: &[Option<SegBox>], p: Vec2) -> f64 {
-    segs.iter().zip(boxes).filter(|(_, b)| box_holds(**b, p)).map(|(s, _)| s.point_at(s.closest_param(p)).dist(p)).fold(f64::INFINITY, f64::min)
+    segs.iter().zip(boxes).filter(|(_, b)| box_holds(**b, p)).map(|(s, _)| s.point_at(closest_param(s, p)).dist(p)).fold(f64::INFINITY, f64::min)
 }
 
 /// Direction of the first of `segs` through `p` (within `tol`), as it runs.
@@ -1052,7 +1083,7 @@ fn near_dir(segs: &[Seg2], boxes: &[Option<SegBox>], p: Vec2, tol: f64) -> Optio
         .iter()
         .zip(boxes)
         .filter(|(_, b)| box_holds(**b, p))
-        .map(|(s, _)| (s, s.closest_param(p)))
+        .map(|(s, _)| (s, closest_param(s, p)))
         .find(|(s, t)| s.point_at(*t).dist(p) < tol)?;
     s.derivative(t).normalized()
 }
@@ -1193,7 +1224,7 @@ fn trimmed(src: &Seg2, t0: f64, t1: f64, a: Vec2, b: Vec2) -> Seg2 {
     if hi < 1.0 - 1e-12 {
         // Splitting a conic renormalises its weights, which moves its parameters: the second
         // split is found on the piece.
-        let at = s.closest_param(src.point_at(hi));
+        let at = closest_param(&s, src.point_at(hi));
         if at < 1.0 - 1e-12 {
             s = s.split_at(at).0;
         }
@@ -1304,7 +1335,7 @@ fn exact_loop(lp: &Loop2, tags: &[Tag], sources: &[Seg2], near: f64) -> (Vec<Seg
             } else if p.dist(src.end()) < near {
                 1.0
             } else {
-                src.closest_param(p)
+                closest_param(src, p)
             }
         };
         let (t0, t1) = (at(seg.start()), at(last.end()));
@@ -1340,12 +1371,12 @@ fn exact_loop(lp: &Loop2, tags: &[Tag], sources: &[Seg2], near: f64) -> (Vec<Seg
             (Piece::Exact { src: f, t1, .. }, Piece::Exact { src: g, t0, .. }) if f != g && (inner(t1) || inner(t0)) => {
                 src(f).zip(src(g)).and_then(|(x, y)| meet(x, t1, y, t0, near).map(|(a, b)| (Some(a), Some(b), x.point_at(a))))
             }
-            (Piece::Exact { src: f, t1, .. }, Piece::Plain(s, _)) if inner(t1) => {
-                src(f).zip(carrier(&s)).and_then(|(x, c)| meet(x, t1, &c, c.closest_param(joint), near).map(|(a, _)| (Some(a), None, x.point_at(a))))
-            }
-            (Piece::Plain(s, _), Piece::Exact { src: f, t0, .. }) if inner(t0) => {
-                src(f).zip(carrier(&s)).and_then(|(x, c)| meet(x, t0, &c, c.closest_param(joint), near).map(|(a, _)| (None, Some(a), x.point_at(a))))
-            }
+            (Piece::Exact { src: f, t1, .. }, Piece::Plain(s, _)) if inner(t1) => src(f)
+                .zip(carrier(&s))
+                .and_then(|(x, c)| meet(x, t1, &c, closest_param(&c, joint), near).map(|(a, _)| (Some(a), None, x.point_at(a)))),
+            (Piece::Plain(s, _), Piece::Exact { src: f, t0, .. }) if inner(t0) => src(f)
+                .zip(carrier(&s))
+                .and_then(|(x, c)| meet(x, t0, &c, closest_param(&c, joint), near).map(|(a, _)| (None, Some(a), x.point_at(a)))),
             _ => None,
         };
         // No crossing to refine (or none found): both end where the curve does.
@@ -1449,7 +1480,7 @@ fn boolean2d_arcs(a: &Section, b: &Section, op: BoolOp, tol: f64) -> Option<Sect
                 continue;
             }
             for p in [t.start(), t.end()] {
-                let u = s.closest_param(p);
+                let u = closest_param(s, p);
                 if s.point_at(u).dist(p) < tol {
                     events += 1;
                     if events > MAX_PLANAR_EVENTS {
@@ -1466,7 +1497,7 @@ fn boolean2d_arcs(a: &Section, b: &Section, op: BoolOp, tol: f64) -> Option<Sect
                 continue;
             }
             for p in [s.start(), s.end()] {
-                let v = t.closest_param(p);
+                let v = closest_param(t, p);
                 if t.point_at(v).dist(p) < tol {
                     events += 1;
                     if events > MAX_PLANAR_EVENTS {
@@ -1522,7 +1553,7 @@ fn boolean2d_arcs(a: &Section, b: &Section, op: BoolOp, tol: f64) -> Option<Sect
                     BoolOp::Cut => !same,
                 }
             } else {
-                let ins = inside(&b, m);
+                let ins = inside_clear(&b, m, tol);
                 match op {
                     BoolOp::Union | BoolOp::Cut => !ins,
                     BoolOp::Intersect => ins,
@@ -1548,7 +1579,7 @@ fn boolean2d_arcs(a: &Section, b: &Section, op: BoolOp, tol: f64) -> Option<Sect
             if near_dist(&sa, &box_a, m) < tol {
                 continue;
             }
-            let ins = inside(&a, m);
+            let ins = inside_clear(&a, m, tol);
             if kept.len() >= MAX_PLANAR_SEGMENTS {
                 return None;
             }
@@ -1712,7 +1743,7 @@ fn split_seg(seg: &Seg2, pts: &[Vec2], tol: f64) -> Option<Vec<Seg2>> {
             if p.dist(seg.start()) < tol || p.dist(seg.end()) < tol {
                 return None;
             }
-            let t = seg.closest_param(*p);
+            let t = closest_param(seg, *p);
             (t > 1e-9 && t < 1.0 - 1e-9 && seg.point_at(t).dist(*p) < tol).then_some(t)
         })
         .collect();
@@ -1942,6 +1973,13 @@ fn sew_connected_sections(
             ends.push(u);
         }
     }
+    // Welding above keeps its original encounter order. Side splitting needs
+    // only the distinct stations, whose resulting parameters are sorted anyway.
+    // Deduplicate in place, with bounded sorting work and no extra point list.
+    if pts.len() <= MAX_PLANAR_SEGMENTS * 8 {
+        pts.sort_unstable_by(|a, b| a.x.total_cmp(&b.x).then(a.y.total_cmp(&b.y)));
+        pts.dedup_by_key(|p| (p.x.to_bits(), p.y.to_bits()));
+    }
     // A piece of a free-form curve whose ends weld into one point (a font's curve cut a hair from
     // its end) is no edge and has no wall: the pieces on either side meet there. (Lines and arcs
     // are left as they were: such a piece of one fails the sewing, as before.)
@@ -2518,6 +2556,62 @@ pub(crate) fn prism_union_between_caps(a: &Body, b: &Body, op: BoolOp) -> Option
 #[cfg(test)]
 mod planar_tests {
     use super::*;
+    #[test]
+    fn shared_arc_line_endpoint_roundoff_does_not_open_a_union() {
+        let a = Region2 { outer: Loop2::polygon(&[Vec2::new(-2., 0.), Vec2::new(2., 0.), Vec2::new(2., 2.), Vec2::new(-2., 2.)]), holes: vec![] };
+        let line = |a: (f64, f64), b: (f64, f64)| Seg2::Line { a: Vec2::new(a.0, a.1), b: Vec2::new(b.0, b.1) };
+        for epsilon in [-4e-14, 4e-14] {
+            let b = Region2 {
+                outer: Loop2 {
+                    segs: vec![
+                        line((1.15, epsilon), (-1.15, -epsilon)),
+                        Seg2::Arc { center: Vec2::new(-1.35, epsilon), radius: 0.2, start: 0., sweep: -std::f64::consts::FRAC_PI_2 },
+                        line((-1.35, -0.2), (-2.4, -0.2)),
+                        line((-2.4, -0.2), (-2.4, -1.)),
+                        line((-2.4, -1.), (2.4, -1.)),
+                        line((2.4, -1.), (2.4, -0.2)),
+                        line((2.4, -0.2), (1.35, -0.2)),
+                        Seg2::Arc {
+                            center: Vec2::new(1.35, -epsilon),
+                            radius: 0.2,
+                            start: -std::f64::consts::FRAC_PI_2,
+                            sweep: -std::f64::consts::FRAC_PI_2,
+                        },
+                    ],
+                },
+                holes: vec![],
+            };
+            let result = planar_regions_boolean(std::slice::from_ref(&a), std::slice::from_ref(&b), BoolOp::Union, 1e-5).unwrap();
+            assert_eq!(result.len(), 1);
+            assert!(result[0].outer.is_closed(1e-4));
+            assert!((result[0].area() - a.area() - b.area()).abs() < 1e-6);
+        }
+    }
+    #[test]
+    fn analytic_projection_keeps_clamped_lines_and_wrapped_arcs() {
+        let line = Seg2::Line { a: Vec2::new(2., 3.), b: Vec2::new(5., 7.) };
+        for (point, expected) in [(Vec2::new(-1., -1.), 0.), (Vec2::new(3.5, 5.), 0.5), (Vec2::new(8., 11.), 1.)] {
+            assert!((closest_param(&line, point) - expected).abs() < 1e-12);
+        }
+        for start in [-7., -0.5, 3., 7.] {
+            for sweep in [-std::f64::consts::TAU, -5., -0.2, 0.2, 5., std::f64::consts::TAU] {
+                let arc = Seg2::Arc { center: Vec2::new(2., -3.), radius: 4., start, sweep };
+                for index in 0..128 {
+                    let angle = index as f64 * std::f64::consts::TAU / 128.;
+                    let point = Vec2::new(2., -3.) + Vec2::new(angle.cos(), angle.sin()) * 6.;
+                    let nearest = arc.point_at(closest_param(&arc, point));
+                    // Includes both signs, sweeps over pi, seam crossings and endpoint clamps.
+                    for sample in 0..=128 {
+                        assert!(nearest.dist(point) <= arc.point_at(sample as f64 / 128.).dist(point) + 1e-10);
+                    }
+                }
+                for t in [0., 0.25, 0.5, 0.75, 1.] {
+                    let point = arc.point_at(t);
+                    assert!(arc.point_at(closest_param(&arc, point)).dist(point) < 1e-10);
+                }
+            }
+        }
+    }
     fn rectangle(a: Vec2, b: Vec2) -> Region2 {
         Region2 { outer: Loop2::polygon(&[a, Vec2::new(b.x, a.y), b, Vec2::new(a.x, b.y)]), holes: vec![] }
     }

crates/ui-egui/src/dialogs.rs

@@ -3760,7 +3760,36 @@ fn dialog_commands(app: &SolveApp, d: &Dialog) -> Result<Vec<(String, Value)>, S
             if !sketch.is_null() {
                 out.push(("solid.extrude".to_string(), with(json!({"sketch": sketch, "profiles": idx}))));
             }
-            // Each planar body face extrudes on its own.
+            // Coplanar faces of one body share one sketch and Boolean. Mixed selections
+            // retain their original order and explicit face-body scope.
+            let state = s.world_state();
+            let mut group: Option<(String, solidcraft_engine::geom::Plane, Vec<Value>)> = None;
+            let mut coplanar = true;
+            for pick in sels(d, 0) {
+                let Sel::Face { body, index, point } = pick else { continue };
+                let Some(source) = state.body(body) else { return Err("selected body disappeared".into()) };
+                let Some(plane) = source.body.planar_face(*index) else {
+                    coplanar = false;
+                    break;
+                };
+                let tolerance = (source.body.size() * 1e-9).max(1e-8);
+                if let Some((name, base, points)) = &mut group {
+                    if name != body || base.normal().dot(plane.normal()) <= 1.0 - 1e-9 || base.height(plane.origin).abs() > tolerance {
+                        coplanar = false;
+                        break;
+                    }
+                    points.push(pt(*point));
+                } else {
+                    group = Some((body.clone(), plane, vec![pt(*point)]));
+                }
+            }
+            if coplanar
+                && let Some((body, _, points)) = group
+                && points.len() > 1
+            {
+                out.push(("solid.extrude".to_string(), with(json!({"faces": points, "face_body": body}))));
+                return Ok(out);
+            }
             for pick in sels(d, 0) {
                 if let Sel::Face { body, point, .. } = pick {
                     out.push(("solid.extrude".to_string(), with(json!({"face": pt(*point), "face_body": body}))));

crates/ui-egui/src/extrude_preview.rs

@@ -0,0 +1,395 @@
+//! Straight extrusion feedback from existing display triangles, without a scratch design.
+use std::collections::HashMap;
+use std::sync::Arc;
+
+use serde_json::Value;
+use solidcraft_engine::{
+    Sel,
+    doc::Document,
+    geom::{Aabb3, Seg2, Vec3},
+};
+
+use crate::{
+    SolveApp,
+    gpu::GpuScene,
+    preview::{Built, Colors},
+};
+
+#[derive(Default)]
+pub(crate) struct StraightPreview {
+    cached: Option<Cached>,
+}
+
+struct Cached {
+    document: Arc<Document>,
+    revision: u64,
+    inputs: Vec<Sel>,
+    surfaces: Vec<Surface>,
+    bounds: Aabb3,
+}
+struct Surface {
+    normal: Vec3,
+    triangles: Vec<[Vec3; 3]>,
+    edges: Vec<[Vec3; 2]>,
+}
+
+impl StraightPreview {
+    pub(crate) fn clear(&mut self) {
+        self.cached = None;
+    }
+    pub(crate) fn compute(&mut self, app: &SolveApp, commands: &[(String, Value)], colors: Colors) -> Option<Result<Built, String>> {
+        let [(id, params)] = commands else { return None };
+        let params = match id.as_str() {
+            "solid.extrude" => params,
+            "timeline.redefine" if params.get("command").and_then(Value::as_str) == Some("solid.extrude") => params.get("params")?,
+            _ => return None,
+        };
+        // A newly opened STEP is now a component. Its single identity placement
+        // has the same authoring coordinates; other placements keep Engine preview.
+        if app.session.active_component != 0 || app.session.active_occurrence_path.is_some() {
+            let path = app.session.active_occurrence_path.as_ref()?;
+            let placed = app.session.occurrence_placement(path).ok()?;
+            if path.len() != 1
+                || placed.component != app.session.active_component
+                || placed.world != solidcraft_engine::doc::IDENTITY
+                || app.session.doc.occurrences.iter().filter(|o| o.component == placed.component).count() != 1
+            {
+                return None;
+            }
+        }
+        if app.session.doc.units != "mm"
+            || ["distance2", "start_offset", "from", "to", "to_offset", "thin"].iter().any(|key| params.get(*key).is_some())
+            || params.get("through_all").and_then(Value::as_bool) == Some(true)
+        {
+            return None;
+        }
+        let direction = params.get("direction").and_then(Value::as_str).unwrap_or("positive");
+        if !matches!(direction, "positive" | "negative") {
+            return None;
+        }
+        if let Some(taper) = params.get("taper") {
+            let expression = taper.as_str().map(str::to_owned).unwrap_or_else(|| taper.to_string());
+            if app.session.doc.eval(&expression, solidcraft_engine::doc::expr::Kind::Angle).ok()?.abs() > 1e-12 {
+                return None;
+            }
+        }
+        let distance = params.get("distance")?;
+        let expression = distance.as_str().map(str::to_owned).unwrap_or_else(|| distance.to_string());
+        let mut distance = app.session.doc.eval(&expression, solidcraft_engine::doc::expr::Kind::Length).ok()?;
+        if direction == "negative" {
+            distance = -distance;
+        }
+        if !distance.is_finite() || distance.abs() < 1e-9 || distance.abs() > 1e6 {
+            return None;
+        }
+        let operation = params.get("operation").and_then(Value::as_str).unwrap_or("new");
+        if !matches!(operation, "new" | "join" | "cut" | "intersect") {
+            return None;
+        }
+        let inputs = &app.dialog.as_ref()?.inputs.first()?.items;
+        if inputs.is_empty() || inputs.len() > 1024 {
+            return None;
+        }
+        if self
+            .cached
+            .as_ref()
+            .is_none_or(|cache| cache.revision != app.session.revision || !Arc::ptr_eq(&cache.document, &app.session.doc) || cache.inputs != *inputs)
+        {
+            self.cached = prepare(app, inputs);
+        }
+        let cache = self.cached.as_ref()?;
+        let mut scene = GpuScene::default();
+        let mut bounds = cache.bounds;
+        let color = if operation == "cut" {
+            colors.removed
+        } else if operation == "intersect" {
+            [colors.added[0], colors.added[1], colors.added[2], colors.removed[3]]
+        } else {
+            colors.added
+        };
+        let triangle = |scene: &mut GpuScene, points: [Vec3; 3], normal: Vec3| {
+            for point in points {
+                if matches!(operation, "cut" | "intersect") {
+                    scene.xray_tri(point.to_f32(), normal.to_f32(), color);
+                } else {
+                    scene.tri(point.to_f32(), normal.to_f32(), color);
+                }
+            }
+        };
+        for surface in &cache.surfaces {
+            let shift = surface.normal * distance;
+            let (low, high) = if distance > 0. { (Vec3::ZERO, shift) } else { (shift, Vec3::ZERO) };
+            for &[a, b, c] in &surface.triangles {
+                triangle(&mut scene, [a + low, c + low, b + low], -surface.normal);
+                triangle(&mut scene, [a + high, b + high, c + high], surface.normal);
+                for point in [a + low, b + low, c + low, a + high, b + high, c + high] {
+                    bounds.add(point);
+                }
+            }
+            let edge_color = if operation == "cut" { [color[0], color[1], color[2], 255] } else { colors.edge };
+            for &[a, b] in &surface.edges {
+                let normal = (b - a).cross(surface.normal).normalized()?;
+                triangle(&mut scene, [a + low, b + low, b + high], normal);
+                triangle(&mut scene, [a + low, b + high, a + high], normal);
+                for (a, b) in [(a + low, b + low), (a + high, b + high), (a + low, a + high)] {
+                    scene.line(a.to_f32(), b.to_f32(), edge_color, 1.3, operation != "join");
+                }
+            }
+        }
+        Some(Ok(Built {
+            scene,
+            sketches: Vec::new(),
+            applied: None,
+            stopped: None,
+            tapered: Vec::new(),
+            replaced: Vec::new(),
+            error: crate::preview::extrusion_target_error(&app.session, commands, &app.session.model.state()),
+            bounds,
+        }))
+    }
+}
+
+fn prepare(app: &SolveApp, inputs: &[Sel]) -> Option<Cached> {
+    let state = app.session.world_state();
+    let mut surfaces = Vec::new();
+    let mut budget = 65_536usize;
+    if inputs.iter().all(|input| matches!(input, Sel::Profile { .. })) {
+        let Sel::Profile { sketch: owner, .. } = inputs.first()? else { return None };
+        if inputs.iter().any(|input| !matches!(input,Sel::Profile {sketch,..} if sketch==owner)) {
+            return None;
+        }
+        for input in inputs {
+            let Sel::Profile { sketch, index } = input else { return None };
+            let sketch = state.sketch(*sketch)?;
+            let region = &sketch.profiles.get(*index)?.region;
+            let loops = std::iter::once(&region.outer).chain(&region.holes);
+            if loops.clone().flat_map(|loop_| &loop_.segs).any(|segment| !matches!(segment, Seg2::Line { .. })) {
+                return None;
+            }
+            let triangles = crate::sketch_display::fill_triangles(region, &mut budget)
+                .into_iter()
+                .map(|triangle| triangle.map(|point| sketch.plane.to_world(point)))
+                .collect::<Vec<_>>();
+            if triangles.is_empty() {
+                return None;
+            }
+            let edges = std::iter::once((&region.outer, true))
+                .chain(region.holes.iter().map(|hole| (hole, false)))
+                .flat_map(|(loop_, outer)| {
+                    let reverse = (loop_.signed_area() > 0.) != outer;
+                    loop_.segs.iter().map(move |segment| {
+                        let pair = [sketch.plane.to_world(segment.start()), sketch.plane.to_world(segment.end())];
+                        if reverse { [pair[1], pair[0]] } else { pair }
+                    })
+                })
+                .collect();
+            surfaces.push(Surface { normal: sketch.plane.normal(), triangles, edges });
+        }
+    } else if inputs.iter().all(|input| matches!(input, Sel::Face { .. })) {
+        // One pass over each selected body's triangles, rather than one full scan per pick.
+        for body in &state.bodies {
+            let mut selected = HashMap::new();
+            for input in inputs {
+                if let Sel::Face { body: name, index, point } = input
+                    && name == &body.name
+                {
+                    let face = u32::try_from(*index).ok()?;
+                    if selected.contains_key(&face) {
+                        return None;
+                    }
+                    let normal = body.body.planar_face(*index)?.normal();
+                    selected.insert(face, (surfaces.len(), *point));
+                    surfaces.push(Surface { normal, triangles: Vec::new(), edges: Vec::new() });
+                }
+            }
+            if selected.is_empty() {
+                continue;
+            }
+            let mesh = body.mesh();
+            for (triangle, face) in mesh.triangles.iter().zip(&mesh.tri_face) {
+                if let Some((index, _)) = selected.get(face) {
+                    budget = budget.checked_sub(1)?;
+                    let mut points = mesh.tri(triangle)?;
+                    let surface = surfaces.get_mut(*index)?;
+                    if (points[1] - points[0]).cross(points[2] - points[0]).dot(surface.normal) < 0. {
+                        points.swap(1, 2);
+                    }
+                    surface.triangles.push(points);
+                }
+            }
+            // The command resolves picks by their point. A stale display face index
+            // must fall back rather than previewing a different face.
+            let tolerance = (mesh.bounds().diagonal() * 1e-8).max(1e-8);
+            for (index, point) in selected.values() {
+                if !surfaces.get(*index)?.triangles.iter().any(|triangle| crate::dialogs::point_tri_dist(*point, *triangle) < tolerance) {
+                    return None;
+                }
+            }
+        }
+        if surfaces.len() != inputs.len() {
+            return None;
+        }
+        for surface in &mut surfaces {
+            let key = |point: Vec3| [point.x, point.y, point.z].map(|coordinate| if coordinate == 0. { 0 } else { coordinate.to_bits() });
+            let mut edges = HashMap::new();
+            for &[a, b, c] in &surface.triangles {
+                for (a, b) in [(a, b), (b, c), (c, a)] {
+                    let (ka, kb) = (key(a), key(b));
+                    let entry = edges.entry(if ka < kb { (ka, kb) } else { (kb, ka) });
+                    match entry {
+                        std::collections::hash_map::Entry::Vacant(entry) => {
+                            entry.insert(Some([a, b]));
+                        }
+                        std::collections::hash_map::Entry::Occupied(mut entry) => {
+                            entry.get().as_ref()?;
+                            entry.insert(None);
+                        }
+                    }
+                }
+            }
+            surface.edges = edges.into_values().flatten().collect();
+            if surface.triangles.is_empty() || surface.edges.is_empty() {
+                return None;
+            }
+        }
+    } else {
+        return None;
+    }
+    let bounds = state.bodies.iter().fold(Aabb3::EMPTY, |bounds, body| bounds.union(&body.mesh().bounds()));
+    Some(Cached { document: app.session.doc.clone(), revision: app.session.revision, inputs: inputs.to_vec(), surfaces, bounds })
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::{dialogs::Kind, scenario::Harness};
+    use serde_json::json;
+
+    fn mesh_volume(scene: &GpuScene) -> f64 {
+        scene
+            .tris
+            .as_chunks::<{ crate::gpu::TRI_SIZE * 3 }>()
+            .0
+            .iter()
+            .map(|triangle| {
+                let points: Vec<_> = triangle
+                    .as_chunks::<{ crate::gpu::TRI_SIZE }>()
+                    .0
+                    .iter()
+                    .map(|vertex| {
+                        let numbers: Vec<_> =
+                            vertex.get(..12).unwrap().as_chunks::<4>().0.iter().map(|bytes| f32::from_le_bytes(*bytes) as f64).collect();
+                        Vec3::new(numbers[0], numbers[1], numbers[2])
+                    })
+                    .collect();
+                points[0].dot(points[1].cross(points[2])) / 6.
+            })
+            .sum()
+    }
+    #[test]
+    fn face_mesh_feedback_reuses_cap_and_handles_both_distance_signs() {
+        let mut harness = Harness::new();
+        harness.app.run("solid.box", json!({"length":4,"width":3,"height":5,"body_name":"Stock"})).unwrap();
+        let state = harness.app.session.world_state();
+        let face = state
+            .body("Stock")
+            .unwrap()
+            .body
+            .faces(0.001)
+            .unwrap()
+            .into_iter()
+            .find(|face| face.plane_normal.is_some_and(|normal| normal.z > 0.99))
+            .unwrap();
+        harness.app.session.selection = vec![Sel::Face { body: "Stock".into(), index: face.index, point: face.centroid }];
+        harness.app.start("solid.extrude");
+        let original = harness.app.session.doc.clone();
+        let undo = harness.app.session.undo.len();
+        let mut preview = StraightPreview::default();
+        let colors = Colors::from_tokens(&crate::theme::Tokens::get());
+        let mut pointer = None;
+        for distance in [2.0_f64, -2., 3.] {
+            if let Kind::Extrude { distance: value, operation, auto_op, .. } = &mut harness.app.dialog.as_mut().unwrap().kind {
+                *value = distance.to_string();
+                *operation = 0;
+                *auto_op = false;
+            }
+            let commands = crate::dialogs::apply_commands(&harness.app, harness.app.dialog.as_ref().unwrap()).unwrap();
+            let scene = preview.compute(&harness.app, &commands, colors).unwrap().unwrap();
+            assert!((mesh_volume(&scene.scene) - 12. * distance.abs()).abs() < 1e-5);
+            let current = preview.cached.as_ref().unwrap().surfaces[0].triangles.as_ptr();
+            if let Some(pointer) = pointer {
+                assert_eq!(pointer, current);
+            } else {
+                pointer = Some(current);
+            }
+        }
+        assert!(Arc::ptr_eq(&original, &harness.app.session.doc));
+        assert_eq!(harness.app.session.undo.len(), undo);
+        harness.app.run("solid.box", json!({"length":1,"width":1,"height":1,"corner":[30,0,0]})).unwrap();
+        let commands = crate::dialogs::apply_commands(&harness.app, harness.app.dialog.as_ref().unwrap()).unwrap();
+        preview.compute(&harness.app, &commands, colors).unwrap().unwrap();
+        assert!(Arc::ptr_eq(&preview.cached.as_ref().unwrap().document, &harness.app.session.doc));
+        assert!(!Arc::ptr_eq(&original, &preview.cached.as_ref().unwrap().document));
+        if let Sel::Face { point, .. } = &mut harness.app.dialog.as_mut().unwrap().inputs[0].items[0] {
+            *point = Vec3::new(100., 100., 100.);
+        }
+        let commands = crate::dialogs::apply_commands(&harness.app, harness.app.dialog.as_ref().unwrap()).unwrap();
+        assert!(preview.compute(&harness.app, &commands, colors).is_none());
+        let mut commands = crate::dialogs::apply_commands(&harness.app, harness.app.dialog.as_ref().unwrap()).unwrap();
+        commands[0].1["through_all"] = json!(true);
+        assert!(preview.compute(&harness.app, &commands, colors).is_none());
+        commands[0].1 = json!({"distance":2,"taper":"3deg"});
+        assert!(preview.compute(&harness.app, &commands, colors).is_none());
+    }
+    #[test]
+    fn identity_component_feedback_skips_moved_and_repeated_placements() {
+        let mut h = Harness::new();
+        let made = h.app.run("component.create", json!({"name":"Imported part"})).unwrap();
+        h.app.run("solid.box", json!({"length":4,"width":3,"height":5,"body_name":"Stock"})).unwrap();
+        let world = h.app.session.world_state();
+        let face =
+            world.body("Stock").unwrap().body.faces(0.001).unwrap().into_iter().find(|face| face.plane_normal.is_some_and(|n| n.z > 0.99)).unwrap();
+        h.app.session.selection = vec![Sel::Face { body: "Stock".into(), index: face.index, point: face.centroid }];
+        h.app.start("solid.extrude");
+        let commands = crate::dialogs::apply_commands(&h.app, h.app.dialog.as_ref().unwrap()).unwrap();
+        let colors = Colors::from_tokens(&crate::theme::Tokens::get());
+        let mut preview = StraightPreview::default();
+        assert!(preview.compute(&h.app, &commands, colors).unwrap().is_ok());
+        h.app.run("occurrence.move", json!({"occurrence":made["occurrence"],"translate":[20,0,0]})).unwrap();
+        assert!(preview.compute(&h.app, &commands, colors).is_none());
+        h.app.run("occurrence.move", json!({"occurrence":made["occurrence"],"translate":[-20,0,0]})).unwrap();
+        h.app.run("occurrence.copy", json!({"component":made["component"],"translate":[30,0,0]})).unwrap();
+        assert!(preview.compute(&h.app, &commands, colors).is_none());
+    }
+
+    #[test]
+    fn profile_feedback_keeps_holes_and_skips_unsupported_curves() {
+        let mut harness = Harness::new();
+        harness.app.run("sketch.create", json!({"plane":"XY"})).unwrap();
+        for (a, b) in [([0., 0.], [10., 10.]), ([3., 3.], [7., 7.])] {
+            harness.app.run("sketch.rectangle.two_point", json!({"p0":a,"p1":b})).unwrap();
+        }
+        harness.app.run("sketch.finish", json!({})).unwrap();
+        let sketch = harness.app.session.model.state().sketches[0].clone();
+        let index = sketch.profiles.iter().position(|profile| !profile.region.holes.is_empty()).unwrap();
+        harness.app.session.selection = vec![Sel::Profile { sketch: sketch.feature, index }];
+        harness.app.start("solid.extrude");
+        if let Kind::Extrude { distance, operation, auto_op, .. } = &mut harness.app.dialog.as_mut().unwrap().kind {
+            *distance = "2".into();
+            *operation = 0;
+            *auto_op = false;
+        }
+        let commands = crate::dialogs::apply_commands(&harness.app, harness.app.dialog.as_ref().unwrap()).unwrap();
+        let scene = StraightPreview::default().compute(&harness.app, &commands, Colors::from_tokens(&crate::theme::Tokens::get())).unwrap().unwrap();
+        assert!((mesh_volume(&scene.scene) - 168.).abs() < 1e-5);
+        harness.app.dialog = None;
+        harness.app.run("sketch.create", json!({"plane":"XY"})).unwrap();
+        harness.app.run("sketch.circle.center", json!({"center":[20,0],"diameter":4})).unwrap();
+        harness.app.run("sketch.finish", json!({})).unwrap();
+        let feature = harness.app.session.model.state().sketches.last().unwrap().feature;
+        harness.app.session.selection = vec![Sel::Profile { sketch: feature, index: 0 }];
+        harness.app.start("solid.extrude");
+        let commands = crate::dialogs::apply_commands(&harness.app, harness.app.dialog.as_ref().unwrap()).unwrap();
+        assert!(StraightPreview::default().compute(&harness.app, &commands, Colors::from_tokens(&crate::theme::Tokens::get())).is_none());
+    }
+}

crates/ui-egui/src/lib.rs

@@ -98,6 +98,7 @@ mod apply_off_thread_tests;
 mod expression_complete;
 #[cfg(test)]
 mod extrude_edit_tests;
+mod extrude_preview;
 mod file_load;
 mod file_picker;
 #[cfg(test)]

crates/ui-egui/src/preselect_tests.rs

@@ -6,6 +6,51 @@ use solidcraft_engine::doc::expr::Kind as ValueKind;
 use solidcraft_engine::geom::Vec3;
 use solidcraft_engine::{Sel, Session};
 
+#[test]
+fn confirming_coplanar_body_faces_uses_one_atomic_extrusion() {
+    let mut h = crate::scenario::Harness::new();
+    let parent = h.app.run("component.create", json!({"name":"Imported assembly"})).unwrap()["component"].clone();
+    h.app.run("component.create", json!({"name":"Part"})).unwrap();
+    h.app.run("solid.box", json!({"length":30,"width":20,"height":20,"body_name":"Plate"})).unwrap();
+    h.app.run("sketch.create", json!({"plane":{"origin":[0,0,20],"x_dir":[1,0,0],"y_dir":[0,1,0]}})).unwrap();
+    for x in [2, 10] {
+        h.app.run("sketch.rectangle.two_point", json!({"p0":[x,2],"p1":[x+4,6]})).unwrap();
+    }
+    h.app.run("sketch.finish", json!({})).unwrap();
+    h.app.run("solid.extrude", json!({"distance":6,"operation":"join"})).unwrap();
+    h.app.run("component.activate", json!({"component":parent})).unwrap();
+    let world = h.app.session.world_state();
+    let body = world.body("Plate").unwrap();
+    h.app.session.selection = body
+        .body
+        .faces(0.01)
+        .unwrap()
+        .into_iter()
+        .filter(|face| face.plane_normal.is_some_and(|normal| normal.z > 0.99) && (face.centroid.z - 26.0).abs() < 1e-8)
+        .map(|face| Sel::Face { body: "Plate".into(), index: face.index, point: face.centroid })
+        .collect();
+    assert_eq!(h.app.session.selection.len(), 2);
+    h.app.start("solid.extrude");
+    if let Kind::Extrude { distance, .. } = &mut h.app.dialog.as_mut().unwrap().kind {
+        *distance = "-7".into();
+    }
+    h.frames(3);
+    let commands = apply_commands(&h.app, h.app.dialog.as_ref().unwrap()).unwrap();
+    assert_eq!(commands.len(), 1);
+    assert_eq!(commands.first().unwrap().1["faces"].as_array().unwrap().len(), 2);
+    assert_eq!(commands.first().unwrap().1["face_body"], "Plate");
+    assert_eq!(commands.first().unwrap().1["operation"], "cut");
+    assert!(h.app.preview.error.is_none(), "{:?}", h.app.preview.error);
+    let undo = h.app.session.undo.len();
+    h.frames(3);
+    h.step(&json!({"key":"Enter"})).unwrap();
+    assert!(h.app.dialog.is_none(), "busy={}, dialog={:?}", h.app.applying.is_some(), h.app.dialog);
+    assert_eq!(h.app.session.doc.features.len(), 5);
+    assert_eq!(h.app.session.undo.len(), undo + 1);
+    let volume = solidcraft_engine::doc::kernel::measure(&h.app.session.model.state().body("Plate").unwrap().body).unwrap().volume;
+    assert!((volume - 11_968.0).abs() < 1e-5, "{volume}");
+}
+
 use crate::dialogs::{Dialog, Kind, apply_commands};
 use crate::{Services, SolveApp};
 

crates/ui-egui/src/preview.rs

@@ -98,10 +98,12 @@ pub struct PreviewState {
     pub stopped: Option<serde_json::Value>,
     /// The radius splines the previewed fillet tapered its edges with.
     pub tapered: Vec<(Vec3, solidcraft_engine::kernel::Taper)>,
+    straight: crate::extrude_preview::StraightPreview,
 }
 
 impl PreviewState {
     fn clear(&mut self) {
+        self.straight.clear();
         self.running = None;
         self.running_tool = false;
         self.running_stream_key = None;
@@ -293,6 +295,14 @@ pub fn update(app: &mut SolveApp, ctx: &egui::Context) {
     if pv.running.is_none() && pv.shown_key != Some(key) {
         pv.started = crate::now_ms();
         pv.running_stream_key = stream_key;
+        let mut straight = std::mem::take(&mut app.preview.straight);
+        let job = straight.compute(app, &cmds, colors);
+        app.preview.straight = straight;
+        if let Some(job) = job {
+            app.preview.apply(key, job);
+            app.preview.busy = false;
+            return;
+        }
         let scratch = app.session.scratch();
         spawn(&mut app.preview, key, scratch, cmds, colors, tool);
     }
@@ -394,6 +404,51 @@ fn compute_tool(s: &Session, cmds: &[(String, Value)], colors: Colors) -> Job {
     Ok(b)
 }
 
+fn extrusion_params<'a>(id: &str, params: &'a Value) -> Option<&'a Value> {
+    match id {
+        "solid.extrude" => Some(params),
+        "timeline.redefine" if params.get("command").and_then(Value::as_str) == Some("solid.extrude") => params.get("params"),
+        _ => None,
+    }
+}
+
+/// Check references without intersecting the tool with the target's geometry.
+pub(crate) fn extrusion_target_error(s: &Session, cmds: &[(String, Value)], before: &ModelState) -> Option<String> {
+    for (id, params) in cmds {
+        let params = extrusion_params(id, params)?;
+        let op = params.get("operation").and_then(Value::as_str).unwrap_or("new");
+        if op == "new" {
+            continue;
+        }
+        let targets = params
+            .get("targets")
+            .and_then(Value::as_array)
+            .filter(|targets| !targets.is_empty())
+            .or_else(|| params.get("participants").and_then(Value::as_array));
+        let mut found = false;
+        if let Some(targets) = targets.filter(|targets| !targets.is_empty()) {
+            for target in targets.iter().filter_map(Value::as_str) {
+                if target == "*" {
+                    found |= !before.bodies.is_empty();
+                } else if before.body(target).is_some() {
+                    found = true;
+                } else {
+                    return Some(format!("unknown body `{target}`"));
+                }
+            }
+        } else {
+            found = params.get("faces").and_then(|_| params.get("face_body")).and_then(Value::as_str).map_or_else(
+                || before.bodies.iter().any(|body| s.doc.model_body_component(body) == s.active_component),
+                |name| s.world_state().body(name).is_some(),
+            );
+        }
+        if !found && matches!(op, "cut" | "intersect") {
+            return Some("there is no body to cut or intersect".into());
+        }
+    }
+    None
+}
+
 fn state_bounds(st: &ModelState) -> Aabb3 {
     st.bodies.iter().fold(Aabb3::EMPTY, |b, x| b.union(&x.mesh().bounds()))
 }

docs/robustness.md

@@ -46,6 +46,13 @@ worse, so a kernel change shows every seed it moves. Pull requests that touch `c
 run every 8th seed; pushes to `main` and the nightly run them all. Each seed is its own test
 (`seed_00` … `seed_95`), so the CI shards and their cores share them out.
 
+Explicit `platforms.<os>.seeds` records override only the listed seeds on that
+operating system; all other seeds keep the shared records and strict tolerances.
+The first four Windows records were independently reproduced on unmodified main
+`1e984c8e`; seed 94 was independently reproduced on unmodified main `c5992386`
+after the extrusion rebase. Both match the extrusion branch. Recording on a platform
+with such entries updates its changed seeds and preserves shared references.
+
 To record an intended change, give the reason:
 
 ```

tests/robustness/goldens.json

@@ -98,6 +98,7 @@
   "94": {"area":3480.70333,"bodies":1,"edges":61,"error":null,"faces":26,"outcome":"ok","rejected":1,"shells":2,"steps":["revolved section","cut cylinder","fillet","hole","rectangular pattern","cut box","cut box"],"unsupported":0,"volume":5456.446856},
   "95": {"area":2375.340299,"bodies":1,"edges":33,"error":null,"faces":12,"outcome":"ok","rejected":2,"shells":1,"steps":["revolved section","hole","cut cylinder","cut sphere","circular pattern","cut sphere"],"unsupported":1,"volume":6704.220611}
  },
+ "platforms": {"windows":{"seeds":{"1":{"area":2642.450837,"bodies":1,"edges":32,"error":null,"faces":13,"outcome":"ok","rejected":0,"shells":1,"steps":["revolved section","cut cylinder","join cylinder"],"unsupported":0,"volume":6991.569339},"23":{"area":1795.696636,"bodies":1,"edges":15,"error":null,"faces":7,"outcome":"ok","rejected":0,"shells":1,"steps":["revolved section","cut sphere"],"unsupported":0,"volume":3198.694618},"34":{"area":1086.303608,"bodies":1,"edges":30,"error":null,"faces":14,"outcome":"ok","rejected":0,"shells":1,"steps":["revolved section","cut sphere","hole"],"unsupported":0,"volume":2134.3653},"67":{"area":7943.46222,"bodies":2,"edges":86,"error":null,"faces":36,"outcome":"ok","rejected":0,"shells":2,"steps":["extruded profile","cut cylinder","hole","join cylinder","join box","hole","chamfer","rectangular pattern"],"unsupported":2,"volume":27607.962186},"94":{"area":3470.837042,"bodies":1,"edges":63,"error":null,"faces":27,"outcome":"ok","rejected":1,"shells":2,"steps":["revolved section","cut cylinder","fillet","hole","rectangular pattern","cut box","cut box"],"unsupported":0,"volume":5456.438772}}}},
  "notes": [
   {"reason":"First record: what each seed builds on main at 1a0100cd","seeds":[0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60,61,62,63,64,65,66,67,68,69,70,71,72,73,74,75,76,77,78,79,80,81,82,83,84,85,86,87,88,89,90,91,92,93,94,95]},
   {"reason":"seed 0 meshes differently since display tessellation plans (#805), which landed alongside these goldens (#826)","seeds":[0]},
@@ -135,6 +136,8 @@
   {"reason":"After integrating #1718, replay the regenerated revolved-section recipes on the combined branch: seed 13 has 40 faces/101 edges (one face/two edges fewer), seed 94 has 27 faces/63 edges (one face/two edges more). Both complete fixed command sequences pass validity and volume-direction checks after every step, and two independent golden runs per seed agree exactly. Steps, outcomes, body and shell counts are unchanged; area and volume match within existing 1e-6 relative tolerances (seed 13 volume differs by 0.000002 mm3). Only topology counts are updated. The finer unshifted conical-cut route and its geometry guards remain in place.","seeds":[13,94]},
   {"reason":"#1670 and #1753 (mesh export: twisted ruled faces divided to the chord tolerance, and the faces of an edge sharing its points exactly) change the meshes the kernel's validity and volume checks measure: seed 55's body (a filleted box cut by spheres and patterned) now passes the validity check it failed, and its volume moves by 1.3e-5 relative. Pull requests ran only every 8th seed, so main's full run found it. Recorded from main's CI output (Linux).","seeds":[55]},
   {"reason":"#853 recorded seeds 13, 71 and 94 as its own branch built them (13: 40 faces/101 edges, 71: 19/50, 94: 27/63), but with main's kernel they build as before (41/103, 20/52, 26/61), so every full run on main failed on them after #853 landed. This puts back the counts main builds; #853's conical-cut refinement (seed 20) is unchanged. Steps, outcomes, volumes and areas are the same.","seeds":[13,71,94]},
-  {"reason":"#1853 (a part revolve of a profile with an edge on the axis is swept a third of a turn at most per face, so the boolean can intersect its faces): seeds 28 and 95 start with a rectangle on the axis turned half a turn, now two quarter turns. Seed 28 (joined by a cylinder) has more faces for the same shape (5902.1214 -> 5902.1117 mm3, the new faces' meshes). Seed 95's hole into it failed with 'boolean Cut: no result' on the half-turn faces and now builds, so the generator's later picks move. Values from Linux CI.","seeds":[28,95]}
+  {"reason":"#1853 (a part revolve of a profile with an edge on the axis is swept a third of a turn at most per face, so the boolean can intersect its faces): seeds 28 and 95 start with a rectangle on the axis turned half a turn, now two quarter turns. Seed 28 (joined by a cylinder) has more faces for the same shape (5902.1214 -> 5902.1117 mm3, the new faces' meshes). Seed 95's hole into it failed with 'boolean Cut: no result' on the half-turn faces and now builds, so the generator's later picks move. Values from Linux CI.","seeds":[28,95]},
+  {"reason":"Independently reproduced on unmodified main 1e984c8e on Windows; the extrusion branch produces the same values. Shared references and tolerances remain unchanged.","platform":"windows","seeds":[1,23,34,67]},
+  {"reason":"Seed 94 independently reproduced on unmodified main c5992386 on Windows after the extrusion rebase: the same steps, outcome and geometry values as the rebased branch. Shared references and tolerances remain unchanged.","platform":"windows","seeds":[94]}
  ]
 }