A failed boolean no longer blames "coincident faces on curved bodies" whatever the cause: the exact polygon fallback runs after any failed B-rep boolean (faces that touch, or cross at a shallow angle) and takes planar faces only, but its refusal named coincident faces and curved bodies regardless. It now says which operand is in the way and why: "the tool has 2 curved faces (cylinder)" (kinds: cylinder, cone, sphere, torus, freeform), a face that could not be meshed, a planar face whose mesh is not flat, or a mesh too detailed. Test: planar_fallback_names_the_curved_faces

crates/engine/src/fuzz.rs

@@ -82,7 +82,7 @@ fn classify(e: &EngineError) -> Outcome {
     match e {
         EngineError::Internal(..) => Outcome::new("panic", msg),
         EngineError::BadParams { .. } | EngineError::Disabled(..) | EngineError::UnknownCommand(_) => Outcome::new("rejected", msg),
-        // A failed boolean is a failure even when it says "not supported" (coincident faces on
+        // A failed boolean is a failure even when it says "not supported" (the planar fallback on
         // curved bodies): those are the cases to fix. Features the kernel doesn't do yet (a
         // fillet between curved faces) are limitations.
         // Picks the generator got wrong (a centroid off its face).