fix(io): deduplicate circles and full-circle arcs during DXF import

Duplicate circle entities at the same location inflated pierce counts
and cut pricing (e.g. SULLYS-035 showed 9 pierces instead of 8).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

OpenNest.Console/Program.cs

@@ -41,7 +41,6 @@ static class NestConsole
             }
         }
 
-        using var log = SetUpLog(options);
         var nest = LoadOrCreateNest(options);
 
         if (nest == null)
@@ -68,10 +67,6 @@ static class NestConsole
 
         var overlapCount = CheckOverlaps(plate, options);
 
-        // Flush and close the log before printing results.
-        Trace.Flush();
-        log?.Dispose();
-
         PrintResults(success, plate, elapsed);
         Save(nest, options);
         PostProcess(nest, options);
@@ -112,9 +107,6 @@ static class NestConsole
                 case "--no-save":
                     o.NoSave = true;
                     break;
-                case "--no-log":
-                    o.NoLog = true;
-                    break;
                 case "--keep-parts":
                     o.KeepParts = true;
                     break;
@@ -153,28 +145,14 @@ static class NestConsole
         return o;
     }
 
-    static StreamWriter SetUpLog(Options options)
-    {
-        if (options.NoLog)
-            return null;
-
-        var baseDir = Path.GetDirectoryName(options.InputFiles[0]);
-        var logDir = Path.Combine(baseDir, "test-harness-logs");
-        Directory.CreateDirectory(logDir);
-        var logFile = Path.Combine(logDir, $"debug-{DateTime.Now:yyyyMMdd-HHmmss}.log");
-        var writer = new StreamWriter(logFile) { AutoFlush = true };
-        Trace.Listeners.Add(new TextWriterTraceListener(writer));
-        Console.WriteLine($"Debug log: {logFile}");
-        return writer;
-    }
-
     static Nest LoadOrCreateNest(Options options)
     {
         var nestFile = options.InputFiles.FirstOrDefault(f =>
             f.EndsWith(NestFormat.FileExtension, StringComparison.OrdinalIgnoreCase)
             || f.EndsWith(".zip", StringComparison.OrdinalIgnoreCase));
         var dxfFiles = options.InputFiles.Where(f =>
-            f.EndsWith(".dxf", StringComparison.OrdinalIgnoreCase)).ToList();
+            f.EndsWith(".dxf", StringComparison.OrdinalIgnoreCase) ||
+            f.EndsWith(".dwg", StringComparison.OrdinalIgnoreCase)).ToList();
 
         // If we have a nest file, load it and optionally add DXFs.
         if (nestFile != null)
@@ -210,7 +188,7 @@ static class NestConsole
         // DXF-only mode: create a fresh nest.
         if (dxfFiles.Count == 0)
         {
-            Console.Error.WriteLine("Error: no nest (.nest) or DXF (.dxf) files specified");
+            Console.Error.WriteLine("Error: no nest (.nest) or CAD (.dxf/.dwg) files specified");
             return null;
         }
 
@@ -484,7 +462,7 @@ static class NestConsole
         Console.Error.WriteLine("Usage: OpenNest.Console <input-files...> [options]");
         Console.Error.WriteLine();
         Console.Error.WriteLine("Arguments:");
-        Console.Error.WriteLine("  input-files            One or more .nest nest files or .dxf drawing files");
+        Console.Error.WriteLine("  input-files            One or more .nest nest files or .dxf/.dwg drawing files");
         Console.Error.WriteLine();
         Console.Error.WriteLine("Modes:");
         Console.Error.WriteLine("  <nest.nest>             Load nest and fill (existing behavior)");
@@ -503,7 +481,6 @@ static class NestConsole
         Console.Error.WriteLine("  --keep-parts           Don't clear existing parts before filling");
         Console.Error.WriteLine("  --check-overlaps       Run overlap detection after fill (exit code 1 if found)");
         Console.Error.WriteLine("  --no-save              Skip saving output file");
-        Console.Error.WriteLine("  --no-log               Skip writing debug log file");
         Console.Error.WriteLine("  --post <name>          Run a post processor after nesting");
         Console.Error.WriteLine("  --post-output <path>   Output file for post processor (default: <input>.cnc)");
         Console.Error.WriteLine("  --posts-dir <path>     Directory containing post processor DLLs (default: Posts/)");
@@ -522,7 +499,6 @@ static class NestConsole
         public Size? PlateSize;
         public bool CheckOverlaps;
         public bool NoSave;
-        public bool NoLog;
         public bool KeepParts;
         public bool AutoNest;
         public string TemplateFile;

OpenNest.Core/CNC/CuttingStrategy/ContourCuttingStrategy.cs

@@ -69,8 +69,16 @@ namespace OpenNest.CNC.CuttingStrategy
             EmitScribeContours(result, scribeEntities);
 
             foreach (var entry in cutoutEntries)
+            {
+                if (!entry.Shape.IsClosed())
+                    EmitRawContour(result, entry.Shape);
+                else
                     EmitContour(result, entry.Shape, entry.Point, entry.Entity);
+            }
 
+            if (!profile.Perimeter.IsClosed())
+                EmitRawContour(result, profile.Perimeter);
+            else
                 EmitContour(result, profile.Perimeter, perimeterPt, perimeterEntity, ContourType.External);
 
             result.Mode = Mode.Incremental;
@@ -99,10 +107,14 @@ namespace OpenNest.CNC.CuttingStrategy
             // Find the target shape that contains the clicked entity
             var (targetShape, matchedEntity) = FindTargetShape(profile, point, entity);
 
-            // Emit cutouts — only the target gets lead-in/out
+            // Emit cutouts — only the target gets lead-in/out (skip open contours)
             foreach (var cutout in profile.Cutouts)
             {
-                if (cutout == targetShape)
+                if (!cutout.IsClosed())
+                {
+                    EmitRawContour(result, cutout);
+                }
+                else if (cutout == targetShape)
                 {
                     var ct = DetectContourType(cutout);
                     EmitContour(result, cutout, point, matchedEntity, ct);
@@ -114,7 +126,11 @@ namespace OpenNest.CNC.CuttingStrategy
             }
 
             // Emit perimeter
-            if (profile.Perimeter == targetShape)
+            if (!profile.Perimeter.IsClosed())
+            {
+                EmitRawContour(result, profile.Perimeter);
+            }
+            else if (profile.Perimeter == targetShape)
             {
                 EmitContour(result, profile.Perimeter, point, matchedEntity, ContourType.External);
             }
@@ -289,9 +305,6 @@ namespace OpenNest.CNC.CuttingStrategy
                 subPgm.Codes.AddRange(leadIn.Generate(relativePoint, normal, winding));
                 var reindexed = relativeShape.ReindexAt(relativePoint, relativeCircle);
 
-                if (Parameters.TabsEnabled && Parameters.TabConfig != null)
-                    reindexed = TrimShapeForTab(reindexed, relativePoint, Parameters.TabConfig.Size);
-
                 subPgm.Codes.AddRange(ConvertShapeToMoves(reindexed, relativePoint));
                 subPgm.Codes.AddRange(leadOut.Generate(relativePoint, normal, winding));
                 subPgm.Mode = Mode.Incremental;
@@ -315,7 +328,7 @@ namespace OpenNest.CNC.CuttingStrategy
 
             var reindexedShape = shape.ReindexAt(point, entity);
 
-            if (Parameters.TabsEnabled && Parameters.TabConfig != null)
+            if (Parameters.TabsEnabled && Parameters.TabConfig != null && contourType == ContourType.External)
                 reindexedShape = TrimShapeForTab(reindexedShape, point, Parameters.TabConfig.Size);
 
             program.Codes.AddRange(ConvertShapeToMoves(reindexedShape, point));

OpenNest.Core/CNC/RapidEnumerator.cs

@@ -0,0 +1,80 @@
+using OpenNest.Geometry;
+using System.Collections.Generic;
+
+namespace OpenNest.CNC
+{
+    public static class RapidEnumerator
+    {
+        public readonly record struct Segment(Vector From, Vector To);
+
+        public static List<Segment> Enumerate(Program pgm, Vector basePos, Vector startPos)
+        {
+            var results = new List<Segment>();
+
+            // Draw the rapid from the previous tool position to the program's first
+            // pierce point. This also primes pos so the interior walk interprets
+            // Incremental deltas from the correct absolute location (basePos), which
+            // matters for raw pre-lead-in programs that are emitted Incremental.
+            var firstPierce = FirstPiercePoint(pgm, basePos);
+            results.Add(new Segment(startPos, firstPierce));
+
+            var pos = firstPierce;
+            Walk(pgm, basePos, ref pos, skipFirst: true, results);
+            return results;
+        }
+
+        private static Vector FirstPiercePoint(Program pgm, Vector basePos)
+        {
+            for (var i = 0; i < pgm.Length; i++)
+            {
+                if (pgm[i] is SubProgramCall call && call.Program != null)
+                    return FirstPiercePoint(call.Program, basePos + call.Offset);
+
+                if (pgm[i] is Motion motion)
+                    return motion.EndPoint + basePos;
+            }
+            return basePos;
+        }
+
+        private static void Walk(Program pgm, Vector basePos, ref Vector pos, bool skipFirst, List<Segment> results)
+        {
+            var skipped = !skipFirst;
+
+            for (var i = 0; i < pgm.Length; ++i)
+            {
+                var code = pgm[i];
+
+                if (code is SubProgramCall { Program: { } program } call)
+                {
+                    var holeBase = basePos + call.Offset;
+                    var firstPierce = FirstPiercePoint(program, holeBase);
+
+                    if (!skipped)
+                        skipped = true;
+                    else
+                        results.Add(new Segment(pos, firstPierce));
+
+                    var subPos = holeBase;
+                    Walk(program, holeBase, ref subPos, skipFirst: true, results);
+                    pos = subPos;
+                }
+                else if (code is Motion motion)
+                {
+                    var endpt = pgm.Mode == Mode.Incremental
+                        ? motion.EndPoint + pos
+                        : motion.EndPoint + basePos;
+
+                    if (code.Type == CodeType.RapidMove)
+                    {
+                        if (!skipped)
+                            skipped = true;
+                        else
+                            results.Add(new Segment(pos, endpt));
+                    }
+
+                    pos = endpt;
+                }
+            }
+        }
+    }
+}

OpenNest.Core/CanonicalAngle.cs

@@ -0,0 +1,78 @@
+using OpenNest.Converters;
+using OpenNest.Geometry;
+using System.Linq;
+
+namespace OpenNest
+{
+    /// <summary>
+    /// Computes the rotation that maps a drawing to its canonical (MBR-axis-aligned) frame.
+    /// Lives in OpenNest.Core so Drawing.Program setter can invoke it directly without
+    /// a circular dependency on OpenNest.Engine.
+    /// </summary>
+    public static class CanonicalAngle
+    {
+        /// <summary>Angles with |v| below this (radians) are snapped to 0.</summary>
+        public const double SnapToZero = 0.001;
+
+        /// <summary>
+        /// Derives the canonical angle from a pre-computed MBR. Used both by Compute (which
+        /// computes the MBR itself) and by PartClassifier (which already has one). Single formula
+        /// across both callers.
+        /// </summary>
+        public static double FromMbr(BoundingRectangleResult mbr)
+        {
+            if (mbr.Area <= OpenNest.Math.Tolerance.Epsilon)
+                return 0.0;
+
+            // The MBR edge angle can represent any of four equivalent orientations
+            // (edge-i, edge-i + π/2, edge-i + π, edge-i - π/2) depending on which hull
+            // edge the algorithm happened to pick. Normalize -mbr.Angle to the
+            // representative in [-π/4, π/4] so snap-to-zero works for inputs near
+            // ANY of the equivalent orientations.
+            var angle = -mbr.Angle;
+            const double halfPi = System.Math.PI / 2.0;
+            angle -= halfPi * System.Math.Round(angle / halfPi);
+
+            if (System.Math.Abs(angle) < SnapToZero)
+                return 0.0;
+
+            return angle;
+        }
+
+        public static double Compute(Drawing drawing)
+        {
+            if (drawing?.Program == null)
+                return 0.0;
+
+            var entities = ConvertProgram.ToGeometry(drawing.Program)
+                .Where(e => e.Layer != SpecialLayers.Rapid);
+
+            var shapes = ShapeBuilder.GetShapes(entities);
+            if (shapes.Count == 0)
+                return 0.0;
+
+            var perimeter = shapes[0];
+            var perimeterArea = perimeter.Area();
+            for (var i = 1; i < shapes.Count; i++)
+            {
+                var area = shapes[i].Area();
+                if (area > perimeterArea)
+                {
+                    perimeter = shapes[i];
+                    perimeterArea = area;
+                }
+            }
+
+            var polygon = perimeter.ToPolygonWithTolerance(0.1);
+            if (polygon == null || polygon.Vertices.Count < 3)
+                return 0.0;
+
+            var hull = ConvexHull.Compute(polygon.Vertices);
+            if (hull.Vertices.Count < 3)
+                return 0.0;
+
+            var mbr = RotatingCalipers.MinimumBoundingRectangle(hull);
+            return FromMbr(mbr);
+        }
+    }
+}

OpenNest.Core/Converters/ConvertGeometry.cs

@@ -1,5 +1,6 @@
 using OpenNest.CNC;
 using OpenNest.Geometry;
+using OpenNest.Math;
 using System.Collections.Generic;
 
 namespace OpenNest.Converters
@@ -81,12 +82,21 @@ namespace OpenNest.Converters
             var startpt = arc.StartPoint();
             var endpt = arc.EndPoint();
 
-            if (startpt != lastpt)
+            if (startpt.DistanceTo(lastpt) > Tolerance.ChainTolerance)
                 pgm.MoveTo(startpt);
 
             lastpt = endpt;
 
+            var sweep = System.Math.Abs(arc.SweepAngle());
+            if (sweep < Tolerance.Epsilon || sweep.IsEqualTo(Angle.TwoPI))
+            {
+                pgm.LineTo(endpt);
+            }
+            else
+            {
                 pgm.ArcTo(endpt, arc.Center, arc.IsReversed ? RotationType.CW : RotationType.CCW);
+            }
+
             return lastpt;
         }
 
@@ -94,7 +104,7 @@ namespace OpenNest.Converters
         {
             var startpt = new Vector(circle.Center.X + circle.Radius, circle.Center.Y);
 
-            if (startpt != lastpt)
+            if (startpt.DistanceTo(lastpt) > Tolerance.ChainTolerance)
                 pgm.MoveTo(startpt);
 
             pgm.ArcTo(startpt, circle.Center, circle.Rotation);
@@ -105,7 +115,7 @@ namespace OpenNest.Converters
 
         private static Vector AddLine(Program pgm, Vector lastpt, Line line)
         {
-            if (line.StartPoint != lastpt)
+            if (line.StartPoint.DistanceTo(lastpt) > Tolerance.ChainTolerance)
                 pgm.MoveTo(line.StartPoint);
 
             var move = new LinearMove(line.EndPoint);

OpenNest.Core/Drawing.cs

@@ -16,7 +16,7 @@ namespace OpenNest
         private static int nextColorIndex;
         private Program program;
 
-        public static readonly Color[] PartColors = new Color[]
+        public static Color[] PartColors = new Color[]
         {
             Color.FromArgb(205, 92, 92),    // Indian Red
             Color.FromArgb(148, 103, 189),  // Medium Purple
@@ -54,9 +54,9 @@ namespace OpenNest
             Id = Interlocked.Increment(ref nextId);
             Name = name;
             Material = new Material();
-            Program = pgm;
             Constraints = new NestConstraints();
             Source = new SourceInfo();
+            Program = pgm;
         }
 
         public int Id { get; }
@@ -78,9 +78,29 @@ namespace OpenNest
             {
                 program = value;
                 UpdateArea();
+                RecomputeCanonicalAngle();
             }
         }
 
+        /// <summary>
+        /// Recomputes and stores the canonical angle from the current Program.
+        /// Callers that mutate Program in place (rather than reassigning it) must invoke this explicitly.
+        /// Cut-off drawings are left with Angle=0.
+        /// </summary>
+        public void RecomputeCanonicalAngle()
+        {
+            if (Source == null)
+                Source = new SourceInfo();
+
+            if (program == null || IsCutOff)
+            {
+                Source.Angle = 0.0;
+                return;
+            }
+
+            Source.Angle = CanonicalAngle.Compute(this);
+        }
+
         public Color Color { get; set; }
 
         public bool IsCutOff { get; set; }
@@ -163,5 +183,15 @@ namespace OpenNest
         /// Offset distances to the original location.
         /// </summary>
         public Vector Offset { get; set; }
+
+        /// <summary>
+        /// Rotation (radians) that maps the source program geometry to its canonical
+        /// (MBR-axis-aligned) frame. Populated automatically by the <see cref="Drawing.Program"/>
+        /// setter via <see cref="CanonicalAngle.Compute"/>. A value of 0 means the drawing is
+        /// already canonical or <see cref="Drawing.IsCutOff"/> is true. Callers that mutate
+        /// <see cref="Drawing.Program"/> in place must invoke
+        /// <see cref="Drawing.RecomputeCanonicalAngle"/> to refresh.
+        /// </summary>
+        public double Angle { get; set; }
     }
 }

OpenNest.Core/Geometry/Arc.cs

@@ -93,6 +93,9 @@ namespace OpenNest.Geometry
             }
         }
 
+        public bool IsFullCircle() =>
+            SweepAngle() >= Angle.TwoPI - Tolerance.Epsilon;
+
         /// <summary>
         /// Angle in radians between start and end angles.
         /// </summary>
@@ -267,6 +270,13 @@ namespace OpenNest.Geometry
             get { return Diameter * System.Math.PI * SweepAngle() / Angle.TwoPI; }
         }
 
+        public override Entity Clone()
+        {
+            var copy = new Arc(center, radius, startAngle, endAngle, reversed);
+            CopyBaseTo(copy);
+            return copy;
+        }
+
         /// <summary>
         /// Reverses the rotation direction.
         /// </summary>
@@ -397,10 +407,12 @@ namespace OpenNest.Geometry
                 maxY = startpt.Y;
             }
 
+            var sweep = SweepAngle();
+            if (sweep > Tolerance.Epsilon)
+            {
                 var angle1 = StartAngle;
                 var angle2 = EndAngle;
 
-            // switch the angle to counter clockwise.
                 if (IsReversed)
                     Generic.Swap(ref angle1, ref angle2);
 
@@ -417,6 +429,7 @@ namespace OpenNest.Geometry
 
                 if (Angle.IsBetweenRad(Angle.TwoPI, angle1, angle2))
                     maxX = Center.X + Radius;
+            }
 
             boundingBox.X = minX;
             boundingBox.Y = minY;

OpenNest.Core/Geometry/Box.cs

@@ -1,8 +1,9 @@
-using OpenNest.Math;
+using System;
+using OpenNest.Math;
 
 namespace OpenNest.Geometry
 {
-    public class Box
+    public class Box : IComparable<Box>
     {
         public static readonly Box Empty = new Box();
 
@@ -214,5 +215,19 @@ namespace OpenNest.Geometry
         {
             return string.Format("[Box: X={0}, Y={1}, Width={2}, Length={3}]", X, Y, Width, Length);
         }
+
+        public int CompareTo(Box other)
+        {
+            var cmp = Width.CompareTo(other.Width);
+            return cmp != 0 ? cmp : Length.CompareTo(other.Length);
+        }
+
+        public static bool operator >(Box a, Box b) => a.CompareTo(b) > 0;
+
+        public static bool operator <(Box a, Box b) => a.CompareTo(b) < 0;
+
+        public static bool operator >=(Box a, Box b) => a.CompareTo(b) >= 0;
+
+        public static bool operator <=(Box a, Box b) => a.CompareTo(b) <= 0;
     }
 }

OpenNest.Core/Geometry/Circle.cs

@@ -165,6 +165,13 @@ namespace OpenNest.Geometry
             get { return Circumference(); }
         }
 
+        public override Entity Clone()
+        {
+            var copy = new Circle(center, radius) { Rotation = Rotation };
+            CopyBaseTo(copy);
+            return copy;
+        }
+
         /// <summary>
         /// Reverses the rotation direction.
         /// </summary>

OpenNest.Core/Geometry/EllipseConverter.cs

@@ -173,7 +173,11 @@ namespace OpenNest.Geometry
 
             if (maxDev <= tolerance)
             {
-                results.Add(CreateArc(arcCenter, radius, center, semiMajor, semiMinor, rotation, t0, t1));
+                var arc = CreateArc(arcCenter, radius, center, semiMajor, semiMinor, rotation, t0, t1);
+                if (arc.SweepAngle() < Tolerance.Epsilon)
+                    results.Add(new Line(p0, p1));
+                else
+                    results.Add(arc);
             }
             else
             {

OpenNest.Core/Geometry/Entity.cs

@@ -251,6 +251,23 @@ namespace OpenNest.Geometry
         /// <returns></returns>
         public abstract bool Intersects(Shape shape, out List<Vector> pts);
 
+        /// <summary>
+        /// Creates a deep copy of the entity with a new Id.
+        /// </summary>
+        public abstract Entity Clone();
+
+        /// <summary>
+        /// Copies common Entity properties from this instance to the target.
+        /// </summary>
+        protected void CopyBaseTo(Entity target)
+        {
+            target.Color = Color;
+            target.Layer = Layer;
+            target.LineTypeName = LineTypeName;
+            target.IsVisible = IsVisible;
+            target.Tag = Tag;
+        }
+
         /// <summary>
         /// Type of entity.
         /// </summary>
@@ -259,6 +276,14 @@ namespace OpenNest.Geometry
 
     public static class EntityExtensions
     {
+        public static List<Entity> CloneAll(this IEnumerable<Entity> entities)
+        {
+            var result = new List<Entity>();
+            foreach (var e in entities)
+                result.Add(e.Clone());
+            return result;
+        }
+
         public static List<Vector> CollectPoints(this IEnumerable<Entity> entities)
         {
             var points = new List<Vector>();

OpenNest.Core/Geometry/GeometryOptimizer.cs

@@ -17,6 +17,38 @@ namespace OpenNest.Geometry
                 (list, item, i) => list.GetCollinearLines(item, i),
                 (Line a, Line b, out Line joined) => TryJoinLines(a, b, out joined));
 
+        public static void Deduplicate(IList<Circle> circles)
+        {
+            for (var i = circles.Count - 1; i >= 1; i--)
+            {
+                for (var j = i - 1; j >= 0; j--)
+                {
+                    if (circles[i].Center.DistanceTo(circles[j].Center) <= Tolerance.Epsilon
+                        && circles[i].Radius.IsEqualTo(circles[j].Radius))
+                    {
+                        circles.RemoveAt(i);
+                        break;
+                    }
+                }
+            }
+        }
+
+        public static void Deduplicate(IList<Circle> circles, IList<Arc> arcs)
+        {
+            for (var i = circles.Count - 1; i >= 0; i--)
+            {
+                for (var j = arcs.Count - 1; j >= 0; j--)
+                {
+                    if (arcs[j].Center.DistanceTo(circles[i].Center) <= Tolerance.Epsilon
+                        && arcs[j].Radius.IsEqualTo(circles[i].Radius)
+                        && arcs[j].IsFullCircle())
+                    {
+                        arcs.RemoveAt(j);
+                    }
+                }
+            }
+        }
+
         private delegate bool TryJoin<T>(T a, T b, out T joined);
 
         private static void MergePass<T>(IList<T> items,

OpenNest.Core/Geometry/Line.cs

@@ -257,6 +257,13 @@ namespace OpenNest.Geometry
             }
         }
 
+        public override Entity Clone()
+        {
+            var copy = new Line(pt1, pt2);
+            CopyBaseTo(copy);
+            return copy;
+        }
+
         /// <summary>
         /// Reversed the line.
         /// </summary>

OpenNest.Core/Geometry/Polygon.cs

@@ -168,6 +168,13 @@ namespace OpenNest.Geometry
             get { return Perimeter(); }
         }
 
+        public override Entity Clone()
+        {
+            var copy = new Polygon { Vertices = new List<Vector>(Vertices) };
+            CopyBaseTo(copy);
+            return copy;
+        }
+
         /// <summary>
         /// Reverses the rotation direction of the polygon.
         /// </summary>

OpenNest.Core/Geometry/Shape.cs

@@ -349,6 +349,15 @@ namespace OpenNest.Geometry
             return polygon;
         }
 
+        public override Entity Clone()
+        {
+            var copy = new Shape();
+            foreach (var e in Entities)
+                copy.Entities.Add(e.Clone());
+            CopyBaseTo(copy);
+            return copy;
+        }
+
         /// <summary>
         /// Reverses the rotation direction of the shape.
         /// </summary>

OpenNest.Core/Geometry/ShapeBuilder.cs

@@ -1,12 +1,13 @@
 using OpenNest.Math;
 using System.Collections.Generic;
 using System.Diagnostics;
+using System.Linq;
 
 namespace OpenNest.Geometry
 {
     public static class ShapeBuilder
     {
-        public static List<Shape> GetShapes(IEnumerable<Entity> entities)
+        public static List<Shape> GetShapes(IEnumerable<Entity> entities, double? weldTolerance = null)
         {
             var lines = new List<Line>();
             var arcs = new List<Arc>();
@@ -57,6 +58,9 @@ namespace OpenNest.Geometry
             entityList.AddRange(lines);
             entityList.AddRange(arcs);
 
+            if (weldTolerance.HasValue)
+                WeldEndpoints(entityList, weldTolerance.Value);
+
             while (entityList.Count > 0)
             {
                 var next = entityList[0];
@@ -107,6 +111,93 @@ namespace OpenNest.Geometry
             return shapes;
         }
 
+        public static void WeldEndpoints(List<Entity> entities, double tolerance)
+        {
+            var endpointGroups = new List<List<(Entity entity, bool isStart, Vector point)>>();
+
+            foreach (var entity in entities)
+            {
+                var (start, end) = GetEndpoints(entity);
+                if (!start.IsValid() || !end.IsValid())
+                    continue;
+
+                AddToGroup(endpointGroups, entity, true, start, tolerance);
+                AddToGroup(endpointGroups, entity, false, end, tolerance);
+            }
+
+            foreach (var group in endpointGroups)
+            {
+                if (group.Count <= 1)
+                    continue;
+
+                var avgX = group.Average(g => g.point.X);
+                var avgY = group.Average(g => g.point.Y);
+                var weldedPoint = new Vector(avgX, avgY);
+
+                foreach (var (entity, isStart, _) in group)
+                    ApplyWeld(entity, isStart, weldedPoint);
+            }
+        }
+
+        private static void AddToGroup(
+            List<List<(Entity entity, bool isStart, Vector point)>> groups,
+            Entity entity, bool isStart, Vector point, double tolerance)
+        {
+            foreach (var group in groups)
+            {
+                if (group[0].point.DistanceTo(point) <= tolerance)
+                {
+                    group.Add((entity, isStart, point));
+                    return;
+                }
+            }
+
+            groups.Add(new List<(Entity, bool, Vector)> { (entity, isStart, point) });
+        }
+
+        private static (Vector start, Vector end) GetEndpoints(Entity entity)
+        {
+            switch (entity.Type)
+            {
+                case EntityType.Arc:
+                    var arc = (Arc)entity;
+                    return (arc.StartPoint(), arc.EndPoint());
+
+                case EntityType.Line:
+                    var line = (Line)entity;
+                    return (line.StartPoint, line.EndPoint);
+
+                default:
+                    return (Vector.Invalid, Vector.Invalid);
+            }
+        }
+
+        private static void ApplyWeld(Entity entity, bool isStart, Vector weldedPoint)
+        {
+            switch (entity.Type)
+            {
+                case EntityType.Line:
+                    var line = (Line)entity;
+                    if (isStart)
+                        line.StartPoint = weldedPoint;
+                    else
+                        line.EndPoint = weldedPoint;
+                    break;
+
+                case EntityType.Arc:
+                    var arc = (Arc)entity;
+                    var deltaX = weldedPoint.X - arc.Center.X;
+                    var deltaY = weldedPoint.Y - arc.Center.Y;
+                    var angle = System.Math.Atan2(deltaY, deltaX);
+
+                    if (isStart)
+                        arc.StartAngle = angle;
+                    else
+                        arc.EndAngle = angle;
+                    break;
+            }
+        }
+
         internal static Entity GetConnected(Vector pt, IEnumerable<Entity> geometry)
         {
             var tol = Tolerance.ChainTolerance;

OpenNest.Core/Geometry/ShapeProfile.cs

@@ -75,7 +75,8 @@ namespace OpenNest.Geometry
         /// </summary>
         public static List<Entity> NormalizeEntities(IEnumerable<Entity> entities)
         {
-            var profile = new ShapeProfile(entities.ToList());
+            var cloned = entities.CloneAll();
+            var profile = new ShapeProfile(cloned);
             return profile.ToNormalizedEntities();
         }
 

OpenNest.Core/Geometry/SpatialQuery.cs

@@ -306,50 +306,39 @@ namespace OpenNest.Geometry
             var minDist = double.MaxValue;
             var vx = vertex.X;
             var vy = vertex.Y;
+            var horizontal = IsHorizontalDirection(direction);
 
-            // Pruning: edges are sorted by their perpendicular min-coordinate in PartBoundary.
+            // Pruning: edges are sorted by their perpendicular min-coordinate.
-            if (direction == PushDirection.Left || direction == PushDirection.Right)
+            // For horizontal push, prune by Y range; for vertical push, prune by X range.
-            {
             for (var i = 0; i < edges.Length; i++)
             {
                 var e1 = edges[i].start + edgeOffset;
                 var e2 = edges[i].end + edgeOffset;
 
-                    var minY = e1.Y < e2.Y ? e1.Y : e2.Y;
+                double perpValue, edgeMin, edgeMax;
-                    var maxY = e1.Y > e2.Y ? e1.Y : e2.Y;
+                if (horizontal)
+                {
+                    perpValue = vy;
+                    edgeMin = e1.Y < e2.Y ? e1.Y : e2.Y;
+                    edgeMax = e1.Y > e2.Y ? e1.Y : e2.Y;
+                }
+                else
+                {
+                    perpValue = vx;
+                    edgeMin = e1.X < e2.X ? e1.X : e2.X;
+                    edgeMax = e1.X > e2.X ? e1.X : e2.X;
+                }
 
-                    // Since edges are sorted by minY, if vy < minY, then vy < all subsequent minY.
+                // Since edges are sorted by edgeMin, if perpValue < edgeMin, all subsequent edges are also past.
-                    if (vy < minY - Tolerance.Epsilon)
+                if (perpValue < edgeMin - Tolerance.Epsilon)
                     break;
 
-                    if (vy > maxY + Tolerance.Epsilon)
+                if (perpValue > edgeMax + Tolerance.Epsilon)
                     continue;
 
                 var d = RayEdgeDistance(vx, vy, e1.X, e1.Y, e2.X, e2.Y, direction);
                 if (d < minDist) minDist = d;
             }
-            }
-            else // Up/Down
-            {
-                for (var i = 0; i < edges.Length; i++)
-                {
-                    var e1 = edges[i].start + edgeOffset;
-                    var e2 = edges[i].end + edgeOffset;
-
-                    var minX = e1.X < e2.X ? e1.X : e2.X;
-                    var maxX = e1.X > e2.X ? e1.X : e2.X;
-
-                    // Since edges are sorted by minX, if vx < minX, then vx < all subsequent minX.
-                    if (vx < minX - Tolerance.Epsilon)
-                        break;
-
-                    if (vx > maxX + Tolerance.Epsilon)
-                        continue;
-
-                    var d = RayEdgeDistance(vx, vy, e1.X, e1.Y, e2.X, e2.Y, direction);
-                    if (d < minDist) minDist = d;
-                }
-            }
 
             return minDist;
         }
@@ -642,22 +631,49 @@ namespace OpenNest.Geometry
         {
             for (var i = 0; i < arcEntities.Count; i++)
             {
-                if (arcEntities[i] is Arc arc)
+                if (arcEntities[i] is not Arc arc)
-                {
+                    continue;
+
+                var cx = arc.Center.X;
+                var cy = arc.Center.Y;
+                var r = arc.Radius;
+
                 for (var j = 0; j < lineEntities.Count; j++)
                 {
-                        if (lineEntities[j] is Line line)
+                    if (lineEntities[j] is not Line line)
+                        continue;
+
+                    var p1x = line.pt1.X;
+                    var p1y = line.pt1.Y;
+                    var ex = line.pt2.X - p1x;
+                    var ey = line.pt2.Y - p1y;
+
+                    var det = ex * dirY - ey * dirX;
+                    if (System.Math.Abs(det) < Tolerance.Epsilon)
+                        continue;
+
+                    // The directional distance from an arc point at angle θ to the
+                    // line is t(θ) = [A + r·(ey·cosθ − ex·sinθ)] / det.
+                    // dt/dθ = 0 at θ = atan2(−ex, ey) and θ + π.
+                    var theta1 = Angle.NormalizeRad(System.Math.Atan2(-ex, ey));
+                    var theta2 = Angle.NormalizeRad(theta1 + System.Math.PI);
+
+                    for (var k = 0; k < 2; k++)
                     {
-                            var linePt = line.ClosestPointTo(arc.Center);
+                        var theta = k == 0 ? theta1 : theta2;
-                            var arcPt = arc.ClosestPointTo(linePt);
+
-                            var d = RayEdgeDistance(arcPt.X, arcPt.Y,
+                        if (!Angle.IsBetweenRad(theta, arc.StartAngle, arc.EndAngle, arc.IsReversed))
-                                line.pt1.X, line.pt1.Y, line.pt2.X, line.pt2.Y,
+                            continue;
+
+                        var qx = cx + r * System.Math.Cos(theta);
+                        var qy = cy + r * System.Math.Sin(theta);
+
+                        var d = RayEdgeDistance(qx, qy, p1x, p1y, line.pt2.X, line.pt2.Y,
                             dirX, dirY);
                         if (d < minDist) { minDist = d; if (d <= 0) return 0; }
                     }
                 }
             }
-            }
             return minDist;
         }
 

OpenNest.Core/Math/Fraction.cs

@@ -3,7 +3,7 @@ using System.Linq;
 using System.Text;
 using System.Text.RegularExpressions;
 
-namespace OpenNest.IO.Bom
+namespace OpenNest.Math
 {
     public static class Fraction
     {

OpenNest.Core/PartGeometry.cs

@@ -126,20 +126,10 @@ namespace OpenNest
         {
             var result = new List<Entity>(source.Count);
 
-            for (var i = 0; i < source.Count; i++)
+            foreach (var entity in source)
             {
-                var entity = source[i];
+                var copy = entity.Clone();
-                Entity copy;
+                copy.Offset(location);
-
-                if (entity is Line line)
-                    copy = new Line(line.StartPoint + location, line.EndPoint + location);
-                else if (entity is Arc arc)
-                    copy = new Arc(arc.Center + location, arc.Radius, arc.StartAngle, arc.EndAngle, arc.IsReversed);
-                else if (entity is Circle circle)
-                    copy = new Circle(circle.Center + location, circle.Radius);
-                else
-                    continue;
-
                 result.Add(copy);
             }
 

OpenNest.Core/Plate.cs

@@ -1,6 +1,7 @@
 using OpenNest.Collections;
 using OpenNest.Geometry;
 using OpenNest.Math;
+using OpenNest.Shapes;
 using System;
 using System.Collections.Generic;
 using System.Linq;
@@ -548,6 +549,65 @@ namespace OpenNest
                 Rounding.RoundUpToNearest(xExtent, roundingFactor));
         }
 
+        /// <summary>
+        /// Sizes the plate using the <see cref="PlateSizes"/> catalog: small
+        /// layouts snap to an increment, larger ones round up to the next
+        /// standard mill sheet. The plate's long-axis orientation (X vs Y)
+        /// is preserved. Does nothing if the plate has no parts.
+        /// </summary>
+        public PlateSizeResult SnapToStandardSize(PlateSizeOptions options = null)
+        {
+            if (Parts.Count == 0)
+                return default;
+
+            var bounds = Parts.GetBoundingBox();
+
+            // Quadrant-aware extents relative to the plate origin, matching AutoSize.
+            double xExtent;
+            double yExtent;
+
+            switch (Quadrant)
+            {
+                case 1:
+                    xExtent = System.Math.Abs(bounds.Right) + EdgeSpacing.Right;
+                    yExtent = System.Math.Abs(bounds.Top) + EdgeSpacing.Top;
+                    break;
+
+                case 2:
+                    xExtent = System.Math.Abs(bounds.Left) + EdgeSpacing.Left;
+                    yExtent = System.Math.Abs(bounds.Top) + EdgeSpacing.Top;
+                    break;
+
+                case 3:
+                    xExtent = System.Math.Abs(bounds.Left) + EdgeSpacing.Left;
+                    yExtent = System.Math.Abs(bounds.Bottom) + EdgeSpacing.Bottom;
+                    break;
+
+                case 4:
+                    xExtent = System.Math.Abs(bounds.Right) + EdgeSpacing.Right;
+                    yExtent = System.Math.Abs(bounds.Bottom) + EdgeSpacing.Bottom;
+                    break;
+
+                default:
+                    return default;
+            }
+
+            // PlateSizes.Recommend takes (short, long); canonicalize then map
+            // the result back so the plate's long axis stays aligned with the
+            // parts' long axis.
+            var shortDim = System.Math.Min(xExtent, yExtent);
+            var longDim = System.Math.Max(xExtent, yExtent);
+            var result = PlateSizes.Recommend(shortDim, longDim, options);
+
+            // Plate convention: Length = X axis, Width = Y axis.
+            if (xExtent >= yExtent)
+                Size = new Size(result.Width, result.Length);   // X is the long axis
+            else
+                Size = new Size(result.Length, result.Width);   // Y is the long axis
+
+            return result;
+        }
+
         /// <summary>
         /// Gets the area of the top surface of the plate.
         /// </summary>

OpenNest.Core/Shapes/CircleShape.cs

@@ -7,6 +7,8 @@ namespace OpenNest.Shapes
     {
         public double Diameter { get; set; }
 
+        public override string GenerateName() => $"Circle {Dim(Diameter)} Dia";
+
         public override void SetPreviewDefaults()
         {
             Diameter = 8;

OpenNest.Core/Shapes/IsoscelesTriangleShape.cs

@@ -8,6 +8,8 @@ namespace OpenNest.Shapes
         public double Base { get; set; }
         public double Height { get; set; }
 
+        public override string GenerateName() => $"Isosceles Triangle {Dim(Base)}x{Dim(Height)}";
+
         public override void SetPreviewDefaults()
         {
             Base = 8;

OpenNest.Core/Shapes/LShape.cs

@@ -10,6 +10,8 @@ namespace OpenNest.Shapes
         public double LegWidth { get; set; }
         public double LegHeight { get; set; }
 
+        public override string GenerateName() => $"L {Dim(Width)}x{Dim(Height)}";
+
         public override void SetPreviewDefaults()
         {
             Width = 8;

OpenNest.Core/Shapes/NgonShape.cs

@@ -3,33 +3,40 @@ using System.Collections.Generic;
 
 namespace OpenNest.Shapes
 {
-    public class OctagonShape : ShapeDefinition
+    public class NgonShape : ShapeDefinition
     {
+        public int Sides { get; set; }
         public double Width { get; set; }
 
+        public override string GenerateName() => $"{Sides}-Sided Polygon {Dim(Width)}";
+
         public override void SetPreviewDefaults()
         {
+            Sides = 8;
             Width = 8;
         }
 
         public override Drawing GetDrawing()
         {
+            var n = Sides < 3 ? 3 : Sides;
             var center = Width / 2.0;
-            var circumRadius = Width / (2.0 * System.Math.Cos(System.Math.PI / 8.0));
+            var circumRadius = Width / (2.0 * System.Math.Cos(System.Math.PI / n));
+            var step = 2.0 * System.Math.PI / n;
+            var start = System.Math.PI / n;
 
-            var vertices = new Vector[8];
+            var vertices = new Vector[n];
-            for (var i = 0; i < 8; i++)
+            for (var i = 0; i < n; i++)
             {
-                var angle = System.Math.PI / 8.0 + i * System.Math.PI / 4.0;
+                var angle = start + i * step;
                 vertices[i] = new Vector(
                     center + circumRadius * System.Math.Cos(angle),
                     center + circumRadius * System.Math.Sin(angle));
             }
 
             var entities = new List<Entity>();
-            for (var i = 0; i < 8; i++)
+            for (var i = 0; i < n; i++)
             {
-                var next = (i + 1) % 8;
+                var next = (i + 1) % n;
                 entities.Add(new Line(vertices[i], vertices[next]));
             }
 

OpenNest.Core/Shapes/PipeFlangeShape.cs

@@ -3,31 +3,41 @@ using System.Collections.Generic;
 
 namespace OpenNest.Shapes
 {
-    public class FlangeShape : ShapeDefinition
+    public class PipeFlangeShape : ShapeDefinition
     {
-        public double NominalPipeSize { get; set; }
         public double OD { get; set; }
         public double HoleDiameter { get; set; }
         public double HolePatternDiameter { get; set; }
         public int HoleCount { get; set; }
+        public string PipeSize { get; set; }
+        public double PipeClearance { get; set; }
+        public bool Blind { get; set; }
+
+        public override string GenerateName()
+        {
+            var name = $"Pipe Flange {Dim(OD)} OD";
+            if (!string.IsNullOrEmpty(PipeSize))
+                name += $" {PipeSize} Pipe";
+            return name;
+        }
 
         public override void SetPreviewDefaults()
         {
-            NominalPipeSize = 2;
             OD = 7.5;
             HoleDiameter = 0.875;
             HolePatternDiameter = 5.5;
             HoleCount = 8;
+            PipeSize = "2";
+            PipeClearance = 0.0625;
+            Blind = false;
         }
 
         public override Drawing GetDrawing()
         {
             var entities = new List<Entity>();
 
-            // Outer circle
             entities.Add(new Circle(0, 0, OD / 2.0));
 
-            // Bolt holes evenly spaced on the bolt circle
             var boltCircleRadius = HolePatternDiameter / 2.0;
             var holeRadius = HoleDiameter / 2.0;
             var angleStep = 2.0 * System.Math.PI / HoleCount;
@@ -40,6 +50,12 @@ namespace OpenNest.Shapes
                 entities.Add(new Circle(cx, cy, holeRadius));
             }
 
+            if (!Blind && !string.IsNullOrEmpty(PipeSize) && PipeSizes.TryGetOD(PipeSize, out var pipeOD))
+            {
+                var boreDiameter = pipeOD + PipeClearance;
+                entities.Add(new Circle(0, 0, boreDiameter / 2.0));
+            }
+
             return CreateDrawing(entities);
         }
     }

OpenNest.Core/Shapes/PipeSizes.cs

@@ -0,0 +1,78 @@
+using System.Collections.Generic;
+
+namespace OpenNest.Shapes
+{
+    public static class PipeSizes
+    {
+        public readonly record struct Entry(string Label, double OuterDiameter);
+
+        public static IReadOnlyList<Entry> All { get; } = new[]
+        {
+            new Entry("1/8",    0.405),
+            new Entry("1/4",    0.540),
+            new Entry("3/8",    0.675),
+            new Entry("1/2",    0.840),
+            new Entry("3/4",    1.050),
+            new Entry("1",      1.315),
+            new Entry("1 1/4",  1.660),
+            new Entry("1 1/2",  1.900),
+            new Entry("2",      2.375),
+            new Entry("2 1/2",  2.875),
+            new Entry("3",      3.500),
+            new Entry("3 1/2",  4.000),
+            new Entry("4",      4.500),
+            new Entry("4 1/2",  5.000),
+            new Entry("5",      5.563),
+            new Entry("6",      6.625),
+            new Entry("7",      7.625),
+            new Entry("8",      8.625),
+            new Entry("9",      9.625),
+            new Entry("10",    10.750),
+            new Entry("11",    11.750),
+            new Entry("12",    12.750),
+            new Entry("14",    14.000),
+            new Entry("16",    16.000),
+            new Entry("18",    18.000),
+            new Entry("20",    20.000),
+            new Entry("24",    24.000),
+            new Entry("26",    26.000),
+            new Entry("28",    28.000),
+            new Entry("30",    30.000),
+            new Entry("32",    32.000),
+            new Entry("34",    34.000),
+            new Entry("36",    36.000),
+            new Entry("42",    42.000),
+            new Entry("48",    48.000),
+        };
+
+        public static bool TryGetOD(string label, out double outerDiameter)
+        {
+            foreach (var entry in All)
+            {
+                if (entry.Label == label)
+                {
+                    outerDiameter = entry.OuterDiameter;
+                    return true;
+                }
+            }
+
+            outerDiameter = 0;
+            return false;
+        }
+
+        /// <summary>
+        /// Returns all pipe sizes whose outer diameter is less than or equal to <paramref name="maxOD"/>.
+        /// The bound is inclusive.
+        /// </summary>
+        public static IEnumerable<Entry> GetFittingSizes(double maxOD)
+        {
+            foreach (var entry in All)
+            {
+                if (entry.OuterDiameter <= maxOD)
+                {
+                    yield return entry;
+                }
+            }
+        }
+    }
+}

OpenNest.Core/Shapes/PlateSizes.cs

@@ -0,0 +1,255 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using OpenNest.Geometry;
+
+namespace OpenNest.Shapes
+{
+    /// <summary>
+    /// Catalog of standard mill sheet sizes (inches) with helpers for matching
+    /// a bounding box to a recommended plate size. Uses the project-wide
+    /// (Width, Length) convention where Width is the short dimension and
+    /// Length is the long dimension.
+    /// </summary>
+    public static class PlateSizes
+    {
+        public readonly record struct Entry(string Label, double Width, double Length)
+        {
+            public double Area => Width * Length;
+
+            /// <summary>
+            /// Returns true if a part of the given dimensions fits within this entry
+            /// in either orientation.
+            /// </summary>
+            public bool Fits(double width, double length) =>
+                (width <= Width && length <= Length) || (width <= Length && length <= Width);
+        }
+
+        /// <summary>
+        /// Standard mill sheet sizes (inches), sorted by area ascending.
+        /// Canonical orientation: Width &lt;= Length.
+        /// </summary>
+        public static IReadOnlyList<Entry> All { get; } = new[]
+        {
+            new Entry("48x96",   48,  96),   // 4608
+            new Entry("48x120",  48, 120),   // 5760
+            new Entry("48x144",  48, 144),   // 6912
+            new Entry("60x120",  60, 120),   // 7200
+            new Entry("60x144",  60, 144),   // 8640
+            new Entry("72x120",  72, 120),   // 8640
+            new Entry("72x144",  72, 144),   // 10368
+            new Entry("96x240",  96, 240),   // 23040
+        };
+
+        /// <summary>
+        /// Looks up a standard size by label. Case-insensitive.
+        /// </summary>
+        public static bool TryGet(string label, out Entry entry)
+        {
+            if (!string.IsNullOrWhiteSpace(label))
+            {
+                foreach (var candidate in All)
+                {
+                    if (string.Equals(candidate.Label, label, StringComparison.OrdinalIgnoreCase))
+                    {
+                        entry = candidate;
+                        return true;
+                    }
+                }
+            }
+
+            entry = default;
+            return false;
+        }
+
+        /// <summary>
+        /// Recommends a plate size for the given bounding box. The box's
+        /// spatial axes are normalized to (short, long) so neither the bbox
+        /// orientation nor Box's internal Length/Width naming matters.
+        /// </summary>
+        public static PlateSizeResult Recommend(Box bbox, PlateSizeOptions options = null)
+        {
+            var a = bbox.Width;
+            var b = bbox.Length;
+            return Recommend(System.Math.Min(a, b), System.Math.Max(a, b), options);
+        }
+
+        /// <summary>
+        /// Recommends a plate size for the envelope of the given boxes.
+        /// </summary>
+        public static PlateSizeResult Recommend(IEnumerable<Box> boxes, PlateSizeOptions options = null)
+        {
+            if (boxes == null)
+                throw new ArgumentNullException(nameof(boxes));
+
+            var hasAny = false;
+            var minX = double.PositiveInfinity;
+            var minY = double.PositiveInfinity;
+            var maxX = double.NegativeInfinity;
+            var maxY = double.NegativeInfinity;
+
+            foreach (var box in boxes)
+            {
+                hasAny = true;
+                if (box.Left < minX) minX = box.Left;
+                if (box.Bottom < minY) minY = box.Bottom;
+                if (box.Right > maxX) maxX = box.Right;
+                if (box.Top > maxY) maxY = box.Top;
+            }
+
+            if (!hasAny)
+                throw new ArgumentException("At least one box is required.", nameof(boxes));
+
+            var b = maxX - minX;
+            var a = maxY - minY;
+            return Recommend(System.Math.Min(a, b), System.Math.Max(a, b), options);
+        }
+
+        /// <summary>
+        /// Recommends a plate size for a (width, length) pair.
+        /// Inputs are treated as orientation-independent.
+        /// </summary>
+        public static PlateSizeResult Recommend(double width, double length, PlateSizeOptions options = null)
+        {
+            options ??= new PlateSizeOptions();
+
+            var w = width + 2 * options.Margin;
+            var l = length + 2 * options.Margin;
+
+            // Canonicalize (short, long) — Fits handles rotation anyway, but
+            // normalizing lets the below-min comparison use the narrower
+            // MinSheet dimensions consistently.
+            if (w > l)
+                (w, l) = (l, w);
+
+            // Below full-sheet threshold: snap each dimension up to the nearest increment.
+            if (w <= options.MinSheetWidth && l <= options.MinSheetLength)
+                return SnapResult(w, l, options.SnapIncrement);
+
+            var catalog = BuildCatalog(options.AllowedSizes);
+
+            var best = PickBest(catalog, w, l, options.Selection);
+            if (best.HasValue)
+                return new PlateSizeResult(best.Value.Width, best.Value.Length, best.Value.Label);
+
+            // Nothing in the catalog fits - fall back to snap-up (ad-hoc oversize sheet).
+            return SnapResult(w, l, options.SnapIncrement);
+        }
+
+        private static PlateSizeResult SnapResult(double width, double length, double increment)
+        {
+            if (increment <= 0)
+                return new PlateSizeResult(width, length, null);
+
+            return new PlateSizeResult(SnapUp(width, increment), SnapUp(length, increment), null);
+        }
+
+        private static double SnapUp(double value, double increment)
+        {
+            var steps = System.Math.Ceiling(value / increment);
+            return steps * increment;
+        }
+
+        private static IReadOnlyList<Entry> BuildCatalog(IReadOnlyList<string> allowedSizes)
+        {
+            if (allowedSizes == null || allowedSizes.Count == 0)
+                return All;
+
+            var result = new List<Entry>(allowedSizes.Count);
+            foreach (var label in allowedSizes)
+            {
+                if (TryParseEntry(label, out var entry))
+                    result.Add(entry);
+            }
+
+            return result;
+        }
+
+        private static bool TryParseEntry(string label, out Entry entry)
+        {
+            if (TryGet(label, out entry))
+                return true;
+
+            // Accept ad-hoc "WxL" strings (e.g. "50x100", "50 x 100").
+            if (!string.IsNullOrWhiteSpace(label))
+            {
+                var parts = label.Split(new[] { 'x', 'X' }, 2);
+                if (parts.Length == 2
+                    && double.TryParse(parts[0].Trim(), System.Globalization.NumberStyles.Float, System.Globalization.CultureInfo.InvariantCulture, out var a)
+                    && double.TryParse(parts[1].Trim(), System.Globalization.NumberStyles.Float, System.Globalization.CultureInfo.InvariantCulture, out var b)
+                    && a > 0 && b > 0)
+                {
+                    var width = System.Math.Min(a, b);
+                    var length = System.Math.Max(a, b);
+                    entry = new Entry(label.Trim(), width, length);
+                    return true;
+                }
+            }
+
+            entry = default;
+            return false;
+        }
+
+        private static Entry? PickBest(IReadOnlyList<Entry> catalog, double width, double length, PlateSizeSelection selection)
+        {
+            var fitting = catalog.Where(e => e.Fits(width, length));
+
+            fitting = selection switch
+            {
+                PlateSizeSelection.NarrowestFirst => fitting.OrderBy(e => e.Width).ThenBy(e => e.Area),
+                _ => fitting.OrderBy(e => e.Area).ThenBy(e => e.Width),
+            };
+
+            foreach (var candidate in fitting)
+                return candidate;
+
+            return null;
+        }
+    }
+
+    public readonly record struct PlateSizeResult(double Width, double Length, string MatchedLabel)
+    {
+        public bool IsStandard => MatchedLabel != null;
+    }
+
+    public sealed class PlateSizeOptions
+    {
+        /// <summary>
+        /// If the margin-adjusted bounding box fits within MinSheetWidth x MinSheetLength
+        /// the result is snapped to <see cref="SnapIncrement"/> instead of routed to a
+        /// standard sheet. Default 48" x 48".
+        /// </summary>
+        public double MinSheetWidth { get; set; } = 48;
+        public double MinSheetLength { get; set; } = 48;
+
+        /// <summary>
+        /// Increment used for below-threshold rounding and oversize fallback. Default 1".
+        /// </summary>
+        public double SnapIncrement { get; set; } = 1.0;
+
+        /// <summary>
+        /// Extra clearance added to each side of the bounding box before matching.
+        /// </summary>
+        public double Margin { get; set; } = 0;
+
+        /// <summary>
+        /// Optional whitelist. When non-empty, only these sizes are considered.
+        /// Entries may be standard catalog labels (e.g. "48x96") or arbitrary
+        /// "WxL" strings (e.g. "50x100").
+        /// </summary>
+        public IReadOnlyList<string> AllowedSizes { get; set; }
+
+        /// <summary>
+        /// Tiebreaker when multiple sheets can contain the bounding box.
+        /// </summary>
+        public PlateSizeSelection Selection { get; set; } = PlateSizeSelection.SmallestArea;
+    }
+
+    public enum PlateSizeSelection
+    {
+        /// <summary>Pick the cheapest sheet that contains the bbox (smallest area).</summary>
+        SmallestArea,
+        /// <summary>Prefer narrower-width sheets (e.g. 48-wide before 60-wide).</summary>
+        NarrowestFirst,
+    }
+}

OpenNest.Core/Shapes/RectangleShape.cs

@@ -8,6 +8,8 @@ namespace OpenNest.Shapes
         public double Length { get; set; }
         public double Width { get; set; }
 
+        public override string GenerateName() => $"Rectangle {Dim(Length)}x{Dim(Width)}";
+
         public override void SetPreviewDefaults()
         {
             Length = 12;

OpenNest.Core/Shapes/RightTriangleShape.cs

@@ -8,6 +8,8 @@ namespace OpenNest.Shapes
         public double Width { get; set; }
         public double Height { get; set; }
 
+        public override string GenerateName() => $"Right Triangle {Dim(Width)}x{Dim(Height)}";
+
         public override void SetPreviewDefaults()
         {
             Width = 8;

OpenNest.Core/Shapes/RingShape.cs

@@ -8,6 +8,8 @@ namespace OpenNest.Shapes
         public double OuterDiameter { get; set; }
         public double InnerDiameter { get; set; }
 
+        public override string GenerateName() => $"Ring {Dim(OuterDiameter)}x{Dim(InnerDiameter)}";
+
         public override void SetPreviewDefaults()
         {
             OuterDiameter = 10;

OpenNest.Core/Shapes/RoundedRectangleShape.cs

@@ -10,6 +10,8 @@ namespace OpenNest.Shapes
         public double Width { get; set; }
         public double Radius { get; set; }
 
+        public override string GenerateName() => $"Rounded Rectangle {Dim(Length)}x{Dim(Width)} R{Dim(Radius)}";
+
         public override void SetPreviewDefaults()
         {
             Length = 12;

OpenNest.Core/Shapes/ShapeDefinition.cs

@@ -26,6 +26,14 @@ namespace OpenNest.Shapes
 
         public abstract Drawing GetDrawing();
 
+        public virtual string GenerateName()
+        {
+            var typeName = GetType().Name;
+            return typeName.EndsWith("Shape")
+                ? typeName.Substring(0, typeName.Length - 5)
+                : typeName;
+        }
+
         public virtual void SetPreviewDefaults() { }
 
         public static List<T> LoadFromJson<T>(string path) where T : ShapeDefinition
@@ -34,6 +42,8 @@ namespace OpenNest.Shapes
             return JsonSerializer.Deserialize<List<T>>(json, JsonOptions);
         }
 
+        protected static string Dim(double value) => value.ToString("0.###");
+
         protected Drawing CreateDrawing(List<Entity> entities)
         {
             var pgm = ConvertGeometry.ToProgram(entities);

OpenNest.Core/Shapes/TShape.cs

@@ -10,6 +10,8 @@ namespace OpenNest.Shapes
         public double StemWidth { get; set; }
         public double BarHeight { get; set; }
 
+        public override string GenerateName() => $"T {Dim(Width)}x{Dim(Height)}";
+
         public override void SetPreviewDefaults()
         {
             Width = 10;

OpenNest.Core/Shapes/TrapezoidShape.cs

@@ -9,6 +9,8 @@ namespace OpenNest.Shapes
         public double BottomWidth { get; set; }
         public double Height { get; set; }
 
+        public override string GenerateName() => $"Trapezoid {Dim(TopWidth)}x{Dim(BottomWidth)}x{Dim(Height)}";
+
         public override void SetPreviewDefaults()
         {
             TopWidth = 6;

OpenNest.Core/Splitting/DrawingSplitter.cs

@@ -32,12 +32,20 @@ public static class DrawingSplitter
         var regions = BuildClipRegions(sortedLines, bounds);
         var feature = GetFeature(parameters.Type);
 
+        // Polygonize cutouts once. Used for trimming feature edges (so cut lines
+        // don't travel through a cutout interior) and for hole/containment tests
+        // in the final component-assembly pass.
+        var cutoutPolygons = profile.Cutouts
+            .Select(c => c.ToPolygon())
+            .Where(p => p != null)
+            .ToList();
+
         var results = new List<Drawing>();
         var pieceIndex = 1;
 
         foreach (var region in regions)
         {
-            var pieceEntities = ClipPerimeterToRegion(perimeter, region, sortedLines, feature, parameters);
+            var pieceEntities = ClipPerimeterToRegion(perimeter, region, sortedLines, feature, parameters, cutoutPolygons);
             if (pieceEntities.Count == 0)
                 continue;
 
@@ -47,10 +55,17 @@ public static class DrawingSplitter
             allEntities.AddRange(pieceEntities);
             allEntities.AddRange(cutoutEntities);
 
-            var piece = BuildPieceDrawing(drawing, allEntities, pieceIndex, region);
+            // A single region may yield multiple physically-disjoint pieces when an
+            // interior cutout spans across it. Group the region's entities into
+            // connected closed loops, nest holes by containment, and emit one
+            // Drawing per outer loop (with its contained holes).
+            foreach (var pieceOfRegion in AssemblePieces(allEntities))
+            {
+                var piece = BuildPieceDrawing(drawing, pieceOfRegion, pieceIndex, region);
                 results.Add(piece);
                 pieceIndex++;
             }
+        }
 
         return results;
     }
@@ -218,98 +233,106 @@ public static class DrawingSplitter
     /// and stitching in feature edges. No polygon clipping library needed.
     /// </summary>
     private static List<Entity> ClipPerimeterToRegion(Shape perimeter, Box region,
-        List<SplitLine> splitLines, ISplitFeature feature, SplitParameters parameters)
+        List<SplitLine> splitLines, ISplitFeature feature, SplitParameters parameters,
+        List<Polygon> cutoutPolygons)
     {
         var boundarySplitLines = GetBoundarySplitLines(region, splitLines);
         var entities = new List<Entity>();
-        var splitPoints = new List<(Vector Point, SplitLine Line, bool IsExit)>();
 
         foreach (var entity in perimeter.Entities)
-        {
+            ProcessEntity(entity, region, entities);
-            ProcessEntity(entity, region, boundarySplitLines, entities, splitPoints);
-        }
 
         if (entities.Count == 0)
             return new List<Entity>();
 
-        InsertFeatureEdges(entities, splitPoints, region, boundarySplitLines, feature, parameters);
+        InsertFeatureEdges(entities, region, boundarySplitLines, feature, parameters, cutoutPolygons);
-        EnsurePerimeterWinding(entities);
+        // Winding is handled later in AssemblePieces, once connected components
+        // are known. At this stage the piece may still be multiple disjoint loops.
         return entities;
     }
 
-    private static void ProcessEntity(Entity entity, Box region,
+    private static void ProcessEntity(Entity entity, Box region, List<Entity> entities)
-        List<SplitLine> boundarySplitLines, List<Entity> entities,
-        List<(Vector Point, SplitLine Line, bool IsExit)> splitPoints)
-    {
-        // Find the first boundary split line this entity crosses
-        SplitLine crossedLine = null;
-        Vector? intersectionPt = null;
-
-        foreach (var sl in boundarySplitLines)
-        {
-            if (SplitLineIntersect.CrossesSplitLine(entity, sl))
-            {
-                var pt = SplitLineIntersect.FindIntersection(entity, sl);
-                if (pt != null)
-                {
-                    crossedLine = sl;
-                    intersectionPt = pt;
-                    break;
-                }
-            }
-        }
-
-        if (crossedLine != null)
-        {
-            // Entity crosses a split line — split it and keep the half inside the region
-            var regionSide = RegionSideOf(region, crossedLine);
-            var startPt = GetStartPoint(entity);
-            var startSide = SplitLineIntersect.SideOf(startPt, crossedLine);
-            var startInRegion = startSide == regionSide || startSide == 0;
-
-            SplitEntityAtPoint(entity, intersectionPt.Value, startInRegion, crossedLine, entities, splitPoints);
-        }
-        else
-        {
-            // Entity doesn't cross any boundary split line — check if it's inside the region
-            var mid = MidPoint(entity);
-            if (region.Contains(mid))
-                entities.Add(entity);
-        }
-    }
-
-    private static void SplitEntityAtPoint(Entity entity, Vector point, bool startInRegion,
-        SplitLine crossedLine, List<Entity> entities,
-        List<(Vector Point, SplitLine Line, bool IsExit)> splitPoints)
     {
         if (entity is Line line)
         {
-            var (first, second) = line.SplitAt(point);
+            var clipped = ClipLineToBox(line.StartPoint, line.EndPoint, region);
-            if (startInRegion)
+            if (clipped == null) return;
+            if (clipped.Value.Start.DistanceTo(clipped.Value.End) < Math.Tolerance.Epsilon) return;
+            entities.Add(new Line(clipped.Value.Start, clipped.Value.End));
+            return;
+        }
+
+        if (entity is Arc arc)
         {
-                if (first != null) entities.Add(first);
+            foreach (var sub in ClipArcToRegion(arc, region))
-                splitPoints.Add((point, crossedLine, true));
+                entities.Add(sub);
+            return;
         }
-            else
+    }
+
+    /// <summary>
+    /// Clips an arc against the four edges of a region box. Returns the sub-arcs
+    /// whose midpoints lie inside the region. Uses line-arc intersection to find
+    /// split points, then iteratively bisects the arc at each crossing.
+    /// </summary>
+    private static List<Arc> ClipArcToRegion(Arc arc, Box region)
     {
-                splitPoints.Add((point, crossedLine, false));
+        var edges = new[]
-                if (second != null) entities.Add(second);
-            }
-        }
-        else if (entity is Arc arc)
         {
-            var (first, second) = arc.SplitAt(point);
+            new Line(new Vector(region.Left, region.Bottom), new Vector(region.Right, region.Bottom)),
-            if (startInRegion)
+            new Line(new Vector(region.Right, region.Bottom), new Vector(region.Right, region.Top)),
+            new Line(new Vector(region.Right, region.Top), new Vector(region.Left, region.Top)),
+            new Line(new Vector(region.Left, region.Top), new Vector(region.Left, region.Bottom))
+        };
+
+        var arcs = new List<Arc> { arc };
+
+        foreach (var edge in edges)
         {
-                if (first != null) entities.Add(first);
+            var next = new List<Arc>();
-                splitPoints.Add((point, crossedLine, true));
+            foreach (var a in arcs)
-            }
-            else
             {
-                splitPoints.Add((point, crossedLine, false));
+                if (!Intersect.Intersects(a, edge, out var pts) || pts.Count == 0)
-                if (second != null) entities.Add(second);
+                {
+                    next.Add(a);
+                    continue;
                 }
+
+                // Split the arc at each intersection that actually lies on one of
+                // the working sub-arcs. Prior splits may make some original hits
+                // moot for the sub-arc that now holds them.
+                var working = new List<Arc> { a };
+                foreach (var pt in pts)
+                {
+                    var replaced = new List<Arc>();
+                    foreach (var w in working)
+                    {
+                        var onArc = OpenNest.Math.Angle.IsBetweenRad(
+                            w.Center.AngleTo(pt), w.StartAngle, w.EndAngle, w.IsReversed);
+                        if (!onArc)
+                        {
+                            replaced.Add(w);
+                            continue;
                         }
+
+                        var (first, second) = w.SplitAt(pt);
+                        if (first != null && first.SweepAngle() > Math.Tolerance.Epsilon) replaced.Add(first);
+                        if (second != null && second.SweepAngle() > Math.Tolerance.Epsilon) replaced.Add(second);
+                    }
+                    working = replaced;
+                }
+                next.AddRange(working);
+            }
+            arcs = next;
+        }
+
+        var result = new List<Arc>();
+        foreach (var a in arcs)
+        {
+            if (region.Contains(a.MidPoint()))
+                result.Add(a);
+        }
+        return result;
     }
 
     /// <summary>
@@ -365,104 +388,157 @@ public static class DrawingSplitter
     }
 
     /// <summary>
-    /// Groups split points by split line, pairs exits with entries, and generates feature edges.
+    /// For each boundary split line of the region, generates a feature edge that
+    /// spans the full region boundary along that split line and trims it against
+    /// interior cutouts. This produces one (or zero) feature edge per contiguous
+    /// material interval on the boundary, handling corner regions (one perimeter
+    /// crossing), spanning cutouts (two holes puncturing the line), and
+    /// normal mid-part splits uniformly.
     /// </summary>
     private static void InsertFeatureEdges(List<Entity> entities,
-        List<(Vector Point, SplitLine Line, bool IsExit)> splitPoints,
         Box region, List<SplitLine> boundarySplitLines,
-        ISplitFeature feature, SplitParameters parameters)
+        ISplitFeature feature, SplitParameters parameters,
+        List<Polygon> cutoutPolygons)
     {
-        // Group split points by their split line
+        foreach (var sl in boundarySplitLines)
-        var groups = new Dictionary<SplitLine, List<(Vector Point, bool IsExit)>>();
-        foreach (var sp in splitPoints)
         {
-            if (!groups.ContainsKey(sp.Line))
+            var isVertical = sl.Axis == CutOffAxis.Vertical;
-                groups[sp.Line] = new List<(Vector, bool)>();
+            var extentStart = isVertical ? region.Bottom : region.Left;
-            groups[sp.Line].Add((sp.Point, sp.IsExit));
+            var extentEnd = isVertical ? region.Top : region.Right;
-        }
 
-        foreach (var kvp in groups)
+            if (extentEnd - extentStart < Math.Tolerance.Epsilon)
-        {
-            var sl = kvp.Key;
-            var points = kvp.Value;
-
-            // Pair each exit with the next entry
-            var exits = points.Where(p => p.IsExit).Select(p => p.Point).ToList();
-            var entries = points.Where(p => !p.IsExit).Select(p => p.Point).ToList();
-
-            if (exits.Count == 0 || entries.Count == 0)
                 continue;
 
-            // For each exit, find the matching entry to form the feature edge span
-            // Sort exits and entries by their position along the split line
-            var isVertical = sl.Axis == CutOffAxis.Vertical;
-            exits = exits.OrderBy(p => isVertical ? p.Y : p.X).ToList();
-            entries = entries.OrderBy(p => isVertical ? p.Y : p.X).ToList();
-
-            // Pair them up: each exit with the next entry (or vice versa)
-            var pairCount = System.Math.Min(exits.Count, entries.Count);
-            for (var i = 0; i < pairCount; i++)
-            {
-                var exitPt = exits[i];
-                var entryPt = entries[i];
-
-                var extentStart = isVertical
-                    ? System.Math.Min(exitPt.Y, entryPt.Y)
-                    : System.Math.Min(exitPt.X, entryPt.X);
-                var extentEnd = isVertical
-                    ? System.Math.Max(exitPt.Y, entryPt.Y)
-                    : System.Math.Max(exitPt.X, entryPt.X);
-
             var featureResult = feature.GenerateFeatures(sl, extentStart, extentEnd, parameters);
-
             var isNegativeSide = RegionSideOf(region, sl) < 0;
             var featureEdge = isNegativeSide ? featureResult.NegativeSideEdge : featureResult.PositiveSideEdge;
 
-                if (featureEdge.Count > 0)
+            // Trim any line segments that cross a cutout — cut lines must never
-                    featureEdge = AlignFeatureDirection(featureEdge, exitPt, entryPt, sl.Axis);
+            // travel through a hole.
+            featureEdge = TrimFeatureEdgeAgainstCutouts(featureEdge, cutoutPolygons);
 
             entities.AddRange(featureEdge);
         }
     }
-    }
 
-    private static List<Entity> AlignFeatureDirection(List<Entity> featureEdge, Vector start, Vector end, CutOffAxis axis)
+    /// <summary>
+    /// Subtracts any portions of line entities in <paramref name="featureEdge"/> that
+    /// lie inside any of the supplied cutout polygons. Non-line entities (arcs) are
+    /// passed through unchanged; a tighter fix for arcs in feature edges (weld-gap
+    /// tabs, spike-groove) can be added later if a test demands it.
+    /// </summary>
+    private static List<Entity> TrimFeatureEdgeAgainstCutouts(List<Entity> featureEdge, List<Polygon> cutoutPolygons)
     {
-        var featureStart = GetStartPoint(featureEdge[0]);
+        if (cutoutPolygons.Count == 0 || featureEdge.Count == 0)
-        var featureEnd = GetEndPoint(featureEdge[^1]);
-        var isVertical = axis == CutOffAxis.Vertical;
-
-        var edgeGoesForward = isVertical ? start.Y < end.Y : start.X < end.X;
-        var featureGoesForward = isVertical ? featureStart.Y < featureEnd.Y : featureStart.X < featureEnd.X;
-
-        if (edgeGoesForward != featureGoesForward)
-        {
-            featureEdge = new List<Entity>(featureEdge);
-            featureEdge.Reverse();
-            foreach (var e in featureEdge)
-                e.Reverse();
-        }
-
             return featureEdge;
+
+        var result = new List<Entity>();
+        foreach (var entity in featureEdge)
+        {
+            if (entity is Line line)
+                result.AddRange(SubtractCutoutsFromLine(line, cutoutPolygons));
+            else
+                result.Add(entity);
+        }
+        return result;
     }
 
-    private static void EnsurePerimeterWinding(List<Entity> entities)
+    /// <summary>
+    /// Returns the sub-segments of <paramref name="line"/> that lie outside every
+    /// cutout polygon. Handles the common axis-aligned feature-edge case exactly.
+    /// </summary>
+    private static List<Line> SubtractCutoutsFromLine(Line line, List<Polygon> cutoutPolygons)
     {
-        var shape = new Shape();
+        // Collect parameter values t in [0,1] where the line crosses any cutout edge.
-        shape.Entities.AddRange(entities);
+        var ts = new List<double> { 0.0, 1.0 };
-        var poly = shape.ToPolygon();
+        foreach (var poly in cutoutPolygons)
-        if (poly != null && poly.RotationDirection() != RotationType.CW)
+        {
-            shape.Reverse();
+            var polyLines = poly.ToLines();
+            foreach (var edge in polyLines)
+            {
+                if (TryIntersectSegments(line.StartPoint, line.EndPoint, edge.StartPoint, edge.EndPoint, out var t))
+                {
+                    if (t > Math.Tolerance.Epsilon && t < 1.0 - Math.Tolerance.Epsilon)
+                        ts.Add(t);
+                }
+            }
+        }
 
-        entities.Clear();
+        ts.Sort();
-        entities.AddRange(shape.Entities);
+
+        var segments = new List<Line>();
+        for (var i = 0; i < ts.Count - 1; i++)
+        {
+            var t0 = ts[i];
+            var t1 = ts[i + 1];
+            if (t1 - t0 < Math.Tolerance.Epsilon) continue;
+
+            var tMid = (t0 + t1) * 0.5;
+            var mid = new Vector(
+                line.StartPoint.X + (line.EndPoint.X - line.StartPoint.X) * tMid,
+                line.StartPoint.Y + (line.EndPoint.Y - line.StartPoint.Y) * tMid);
+
+            var insideCutout = false;
+            foreach (var poly in cutoutPolygons)
+            {
+                if (poly.ContainsPoint(mid))
+                {
+                    insideCutout = true;
+                    break;
+                }
+            }
+            if (insideCutout) continue;
+
+            var p0 = new Vector(
+                line.StartPoint.X + (line.EndPoint.X - line.StartPoint.X) * t0,
+                line.StartPoint.Y + (line.EndPoint.Y - line.StartPoint.Y) * t0);
+            var p1 = new Vector(
+                line.StartPoint.X + (line.EndPoint.X - line.StartPoint.X) * t1,
+                line.StartPoint.Y + (line.EndPoint.Y - line.StartPoint.Y) * t1);
+
+            segments.Add(new Line(p0, p1));
+        }
+
+        return segments;
+    }
+
+    /// <summary>
+    /// Segment-segment intersection. On hit, returns the parameter t along segment AB
+    /// (0 = a0, 1 = a1) via <paramref name="tOnA"/>.
+    /// </summary>
+    private static bool TryIntersectSegments(Vector a0, Vector a1, Vector b0, Vector b1, out double tOnA)
+    {
+        tOnA = 0;
+        var rx = a1.X - a0.X;
+        var ry = a1.Y - a0.Y;
+        var sx = b1.X - b0.X;
+        var sy = b1.Y - b0.Y;
+
+        var denom = rx * sy - ry * sx;
+        if (System.Math.Abs(denom) < Math.Tolerance.Epsilon)
+            return false;
+
+        var dx = b0.X - a0.X;
+        var dy = b0.Y - a0.Y;
+        var t = (dx * sy - dy * sx) / denom;
+        var u = (dx * ry - dy * rx) / denom;
+
+        if (t < -Math.Tolerance.Epsilon || t > 1 + Math.Tolerance.Epsilon) return false;
+        if (u < -Math.Tolerance.Epsilon || u > 1 + Math.Tolerance.Epsilon) return false;
+
+        tOnA = t;
+        return true;
     }
 
     private static bool IsCutoutInRegion(Shape cutout, Box region)
     {
         if (cutout.Entities.Count == 0) return false;
-        var pt = GetStartPoint(cutout.Entities[0]);
+        var bb = cutout.BoundingBox;
-        return region.Contains(pt);
+        // Fully contained iff the cutout's bounding box fits inside the region.
+        return bb.Left >= region.Left - Math.Tolerance.Epsilon
+            && bb.Right <= region.Right + Math.Tolerance.Epsilon
+            && bb.Bottom >= region.Bottom - Math.Tolerance.Epsilon
+            && bb.Top <= region.Top + Math.Tolerance.Epsilon;
     }
 
     private static bool DoesCutoutCrossSplitLine(Shape cutout, List<SplitLine> splitLines)
@@ -479,57 +555,135 @@ public static class DrawingSplitter
     }
 
     /// <summary>
-    /// Clip a cutout shape to a region by walking entities, splitting at split line
+    /// Clip a cutout shape to a region by walking entities and splitting at split-line
-    /// intersections, keeping portions inside the region, and closing gaps with
+    /// crossings. Only returns the cutout-edge fragments that lie inside the region —
-    /// straight lines. No polygon clipping library needed.
+    /// it deliberately does NOT emit synthetic closing lines at the region boundary.
+    ///
+    /// Rationale: a closing line on the region boundary would overlap the split-line
+    /// feature edge and reintroduce a cut through the cutout interior. The feature
+    /// edge (trimmed against cutouts in <see cref="InsertFeatureEdges"/>) and these
+    /// cutout fragments are stitched together later by <see cref="AssemblePieces"/>
+    /// using endpoint connectivity, which produces the correct closed loops — one
+    /// loop per physically-connected strip of material.
     /// </summary>
     private static List<Entity> ClipCutoutToRegion(Shape cutout, Box region, List<SplitLine> splitLines)
     {
-        var boundarySplitLines = GetBoundarySplitLines(region, splitLines);
         var entities = new List<Entity>();
-        var splitPoints = new List<(Vector Point, SplitLine Line, bool IsExit)>();
-
         foreach (var entity in cutout.Entities)
-        {
+            ProcessEntity(entity, region, entities);
-            ProcessEntity(entity, region, boundarySplitLines, entities, splitPoints);
+        return entities;
     }
 
-        if (entities.Count == 0)
+    /// <summary>
-            return new List<Entity>();
+    /// Groups a region's entities into closed components and nests holes inside
-
+    /// outer loops by point-in-polygon containment. Returns one entity list per
-        // Close gaps with straight lines (connect exit→entry pairs)
+    /// output <see cref="Drawing"/> — outer loop first, then its contained holes.
-        var groups = new Dictionary<SplitLine, List<(Vector Point, bool IsExit)>>();
+    /// Each outer loop is normalized to CW winding and each hole to CCW.
-        foreach (var sp in splitPoints)
+    /// </summary>
+    private static List<List<Entity>> AssemblePieces(List<Entity> entities)
     {
-            if (!groups.ContainsKey(sp.Line))
+        var pieces = new List<List<Entity>>();
-                groups[sp.Line] = new List<(Vector, bool)>();
+        if (entities.Count == 0) return pieces;
-            groups[sp.Line].Add((sp.Point, sp.IsExit));
+
+        var shapes = ShapeBuilder.GetShapes(entities);
+        if (shapes.Count == 0) return pieces;
+
+        // Polygonize every shape once so we can run containment tests.
+        var polygons = new List<Polygon>(shapes.Count);
+        foreach (var s in shapes)
+            polygons.Add(s.ToPolygon());
+
+        // Classify each shape as outer or hole using nesting by containment.
+        // Shape A is contained in shape B iff A's bounding box is strictly inside
+        // B's bounding box AND a representative vertex of A lies inside B's polygon.
+        // The bbox pre-check avoids the ambiguity of bbox-center tests when two
+        // shapes share a center (e.g., an outer half and a centered cutout).
+        var isHole = new bool[shapes.Count];
+        for (var i = 0; i < shapes.Count; i++)
+        {
+            var bbA = shapes[i].BoundingBox;
+            var repA = FirstVertexOf(shapes[i]);
+
+            for (var j = 0; j < shapes.Count; j++)
+            {
+                if (i == j) continue;
+                if (polygons[j] == null) continue;
+                if (polygons[j].Vertices.Count < 3) continue;
+
+                var bbB = shapes[j].BoundingBox;
+                if (!BoxContainsBox(bbB, bbA)) continue;
+                if (!polygons[j].ContainsPoint(repA)) continue;
+
+                isHole[i] = true;
+                break;
+            }
         }
 
-        foreach (var kvp in groups)
+        // For each outer, attach the holes that fall inside it.
+        for (var i = 0; i < shapes.Count; i++)
         {
-            var sl = kvp.Key;
+            if (isHole[i]) continue;
-            var points = kvp.Value;
-            var isVertical = sl.Axis == CutOffAxis.Vertical;
 
-            var exits = points.Where(p => p.IsExit).Select(p => p.Point)
+            var outer = shapes[i];
-                .OrderBy(p => isVertical ? p.Y : p.X).ToList();
+            var outerPoly = polygons[i];
-            var entries = points.Where(p => !p.IsExit).Select(p => p.Point)
-                .OrderBy(p => isVertical ? p.Y : p.X).ToList();
 
-            var pairCount = System.Math.Min(exits.Count, entries.Count);
+            // Enforce perimeter winding = CW.
-            for (var i = 0; i < pairCount; i++)
+            if (outerPoly != null && outerPoly.Vertices.Count >= 3
-                entities.Add(new Line(exits[i], entries[i]));
+                && outerPoly.RotationDirection() != RotationType.CW)
+                outer.Reverse();
+
+            var piece = new List<Entity>();
+            piece.AddRange(outer.Entities);
+
+            for (var j = 0; j < shapes.Count; j++)
+            {
+                if (!isHole[j]) continue;
+                if (polygons[i] == null || polygons[i].Vertices.Count < 3) continue;
+
+                var bbJ = shapes[j].BoundingBox;
+                if (!BoxContainsBox(shapes[i].BoundingBox, bbJ)) continue;
+
+                var rep = FirstVertexOf(shapes[j]);
+                if (!polygons[i].ContainsPoint(rep)) continue;
+
+                var hole = shapes[j];
+                var holePoly = polygons[j];
+                if (holePoly != null && holePoly.Vertices.Count >= 3
+                    && holePoly.RotationDirection() != RotationType.CCW)
+                    hole.Reverse();
+
+                piece.AddRange(hole.Entities);
             }
 
-        // Ensure CCW winding for cutouts
+            pieces.Add(piece);
-        var shape = new Shape();
+        }
-        shape.Entities.AddRange(entities);
-        var poly = shape.ToPolygon();
-        if (poly != null && poly.RotationDirection() != RotationType.CCW)
-            shape.Reverse();
 
-        return shape.Entities;
+        return pieces;
+    }
+
+    /// <summary>
+    /// Returns the first vertex of a shape (start point of its first entity). Used as
+    /// a representative for containment testing: if bbox pre-check says the whole
+    /// shape is inside another, testing one vertex is sufficient to confirm.
+    /// </summary>
+    private static Vector FirstVertexOf(Shape shape)
+    {
+        if (shape.Entities.Count == 0)
+            return new Vector(0, 0);
+        return GetStartPoint(shape.Entities[0]);
+    }
+
+    /// <summary>
+    /// True iff box <paramref name="inner"/> is entirely inside box
+    /// <paramref name="outer"/> (tolerant comparison).
+    /// </summary>
+    private static bool BoxContainsBox(Box outer, Box inner)
+    {
+        var eps = Math.Tolerance.Epsilon;
+        return inner.Left >= outer.Left - eps
+            && inner.Right <= outer.Right + eps
+            && inner.Bottom >= outer.Bottom - eps
+            && inner.Top <= outer.Top + eps;
     }
 
     private static Vector GetStartPoint(Entity entity)

OpenNest.Engine/BestFit/BestFitCache.cs

@@ -24,6 +24,9 @@ namespace OpenNest.Engine.BestFit
             if (_cache.TryGetValue(key, out var cached))
                 return cached;
 
+            // Operate on the canonical frame so cached pair positions are orientation-invariant.
+            var canonical = CanonicalFrame.AsCanonicalCopy(drawing);
+
             IPairEvaluator evaluator = null;
             ISlideComputer slideComputer = null;
 
@@ -31,7 +34,7 @@ namespace OpenNest.Engine.BestFit
             {
                 if (CreateEvaluator != null)
                 {
-                    try { evaluator = CreateEvaluator(drawing, spacing); }
+                    try { evaluator = CreateEvaluator(canonical, spacing); }
                     catch { /* fall back to default evaluator */ }
                 }
 
@@ -42,7 +45,7 @@ namespace OpenNest.Engine.BestFit
                 }
 
                 var finder = new BestFitFinder(plateWidth, plateHeight, evaluator, slideComputer);
-                var results = finder.FindBestFits(drawing, spacing, StepSize);
+                var results = finder.FindBestFits(canonical, spacing, StepSize);
 
                 _cache.TryAdd(key, results);
                 return results;
@@ -86,9 +89,12 @@ namespace OpenNest.Engine.BestFit
 
             try
             {
+                // Operate on the canonical frame so cached pair positions are orientation-invariant.
+                var canonical = CanonicalFrame.AsCanonicalCopy(drawing);
+
                 if (CreateEvaluator != null)
                 {
-                    try { evaluator = CreateEvaluator(drawing, spacing); }
+                    try { evaluator = CreateEvaluator(canonical, spacing); }
                     catch { /* fall back to default evaluator */ }
                 }
 
@@ -100,7 +106,7 @@ namespace OpenNest.Engine.BestFit
 
                 // Compute candidates and evaluate once with the largest plate.
                 var finder = new BestFitFinder(maxWidth, maxHeight, evaluator, slideComputer);
-                var baseResults = finder.FindBestFits(drawing, spacing, StepSize);
+                var baseResults = finder.FindBestFits(canonical, spacing, StepSize);
 
                 // Cache a filtered copy for each plate size.
                 foreach (var size in needed)

OpenNest.Engine/BestFit/NfpSlideStrategy.cs

@@ -1,18 +1,10 @@
 using OpenNest.Geometry;
-using OpenNest.Math;
 using System.Collections.Generic;
-using System.IO;
 
 namespace OpenNest.Engine.BestFit
 {
     public class NfpSlideStrategy : IBestFitStrategy
     {
-        private static readonly string LogPath = Path.Combine(
-            System.Environment.GetFolderPath(System.Environment.SpecialFolder.Desktop),
-            "nfp-slide-debug.log");
-
-        private static readonly object LogLock = new object();
-
         private readonly double _part2Rotation;
         private readonly Polygon _stationaryPerimeter;
         private readonly Polygon _stationaryHull;
@@ -46,12 +38,6 @@ namespace OpenNest.Engine.BestFit
 
             var hull = ConvexHull.Compute(result.Polygon.Vertices);
 
-            Log($"=== Create: drawing={drawing.Name}, rotation={Angle.ToDegrees(part2Rotation):F1}deg ===");
-            Log($"  Perimeter: {result.Polygon.Vertices.Count} verts, bounds={FormatBounds(result.Polygon)}");
-            Log($"  Hull: {hull.Vertices.Count} verts, bounds={FormatBounds(hull)}");
-            Log($"  Correction: ({result.Correction.X:F4}, {result.Correction.Y:F4})");
-            Log($"  ProgramBBox: {drawing.Program.BoundingBox()}");
-
             return new NfpSlideStrategy(part2Rotation, type, description,
                 result.Polygon, hull, result.Correction);
         }
@@ -63,40 +49,17 @@ namespace OpenNest.Engine.BestFit
             if (stepSize <= 0)
                 return candidates;
 
-            Log($"--- GenerateCandidates: drawing={drawing.Name}, part2Rot={Angle.ToDegrees(_part2Rotation):F1}deg, spacing={spacing}, stepSize={stepSize} ---");
-
-            // Orbiting polygon: same shape rotated to Part2's angle.
             var orbitingPerimeter = PolygonHelper.RotatePolygon(_stationaryPerimeter, _part2Rotation, reNormalize: true);
             var orbitingPoly = ConvexHull.Compute(orbitingPerimeter.Vertices);
 
-            Log($"  Stationary hull: {_stationaryHull.Vertices.Count} verts, bounds={FormatBounds(_stationaryHull)}");
-            Log($"  Orbiting perimeter (rotated): {orbitingPerimeter.Vertices.Count} verts, bounds={FormatBounds(orbitingPerimeter)}");
-            Log($"  Orbiting hull: {orbitingPoly.Vertices.Count} verts, bounds={FormatBounds(orbitingPoly)}");
-
             var nfp = NoFitPolygon.ComputeConvex(_stationaryHull, orbitingPoly);
 
             if (nfp == null || nfp.Vertices.Count < 3)
-            {
-                Log($"  NFP failed or degenerate (verts={nfp?.Vertices.Count ?? 0})");
                 return candidates;
-            }
 
             var verts = nfp.Vertices;
             var vertCount = nfp.IsClosed() ? verts.Count - 1 : verts.Count;
 
-            Log($"  NFP: {verts.Count} verts (closed={nfp.IsClosed()}, walking {vertCount}), bounds={FormatBounds(nfp)}");
-            Log($"  Correction: ({_correction.X:F4}, {_correction.Y:F4})");
-
-            // Log NFP vertices
-            for (var v = 0; v < vertCount; v++)
-                Log($"    NFP vert[{v}]: ({verts[v].X:F4}, {verts[v].Y:F4}) -> corrected: ({verts[v].X - _correction.X:F4}, {verts[v].Y - _correction.Y:F4})");
-
-            // Compare with what RotationSlideStrategy would produce
-            var part1 = Part.CreateAtOrigin(drawing);
-            var part2 = Part.CreateAtOrigin(drawing, _part2Rotation);
-            Log($"  Part1 (rot=0): loc=({part1.Location.X:F4}, {part1.Location.Y:F4}), bbox={part1.BoundingBox}");
-            Log($"  Part2 (rot={Angle.ToDegrees(_part2Rotation):F1}): loc=({part2.Location.X:F4}, {part2.Location.Y:F4}), bbox={part2.BoundingBox}");
-
             var testNumber = 0;
 
             for (var i = 0; i < vertCount; i++)
@@ -125,20 +88,6 @@ namespace OpenNest.Engine.BestFit
                 }
             }
 
-            // Log overlap check for vertex candidates (first few)
-            var checkCount = System.Math.Min(vertCount, 8);
-            for (var c = 0; c < checkCount; c++)
-            {
-                var cand = candidates[c];
-                var p2 = Part.CreateAtOrigin(drawing, cand.Part2Rotation);
-                p2.Location = cand.Part2Offset;
-                var overlaps = part1.Intersects(p2, out _);
-                Log($"  Candidate[{c}]: offset=({cand.Part2Offset.X:F4}, {cand.Part2Offset.Y:F4}), overlaps={overlaps}");
-            }
-
-            Log($"  Total candidates: {candidates.Count}");
-            Log("");
-
             return candidates;
         }
 
@@ -160,20 +109,5 @@ namespace OpenNest.Engine.BestFit
                 Spacing = spacing
             };
         }
-
-        private static string FormatBounds(Polygon polygon)
-        {
-            polygon.UpdateBounds();
-            var bb = polygon.BoundingBox;
-            return $"[({bb.Left:F4}, {bb.Bottom:F4})-({bb.Right:F4}, {bb.Top:F4}), {bb.Width:F2}x{bb.Length:F2}]";
-        }
-
-        private static void Log(string message)
-        {
-            lock (LogLock)
-            {
-                File.AppendAllText(LogPath, message + "\n");
-            }
-        }
     }
 }

OpenNest.Engine/CanonicalFrame.cs

@@ -0,0 +1,76 @@
+using OpenNest.CNC;
+using OpenNest.Geometry;
+using OpenNest.Math;
+using System.Collections.Generic;
+
+namespace OpenNest.Engine
+{
+    /// <summary>
+    /// Produces transient canonical (MBR-axis-aligned) copies of drawings for engine consumption
+    /// and un-rotates placed parts back to the drawing's original frame.
+    /// </summary>
+    public static class CanonicalFrame
+    {
+        /// <summary>
+        /// Returns a new Drawing whose Program geometry is rotated to the canonical frame.
+        /// The source drawing is not mutated.
+        /// </summary>
+        public static Drawing AsCanonicalCopy(Drawing drawing)
+        {
+            if (drawing == null)
+                return null;
+
+            var angle = drawing.Source?.Angle ?? 0.0;
+
+            // Clone program (never mutate the source).
+            var pgm = (drawing.Program.Clone() as OpenNest.CNC.Program)
+                      ?? new OpenNest.CNC.Program();
+
+            if (!Tolerance.IsEqualTo(angle, 0))
+                pgm.Rotate(angle, pgm.BoundingBox().Center);
+
+            var copy = new Drawing(drawing.Name ?? string.Empty, pgm)
+            {
+                Color = drawing.Color,
+                Constraints = drawing.Constraints,
+                Material = drawing.Material,
+                Priority = drawing.Priority,
+                Customer = drawing.Customer,
+                IsCutOff = drawing.IsCutOff,
+                Source = new SourceInfo
+                {
+                    Path = drawing.Source?.Path,
+                    Offset = drawing.Source?.Offset ?? new Vector(0, 0),
+                    Angle = 0.0,
+                },
+            };
+            return copy;
+        }
+
+        /// <summary>
+        /// Composes the source drawing's canonical angle onto each placed part so the
+        /// returned list is in the drawing's original (visible) frame.
+        ///
+        /// Derivation: let sourceAngle = S (rotation mapping source -> canonical).
+        /// Canonical part at rotation R shows visible orientation R.
+        /// Source part at rotation R' shows visible orientation R' + (-S), because the
+        /// source geometry is already rotated by -S relative to canonical.
+        /// Setting equal gives R' = R + S, so we ADD sourceAngle to each placed part.
+        ///
+        /// Rotation is performed around the part's Location so its placement position is preserved;
+        /// only the orientation composes.
+        /// </summary>
+        public static List<Part> FromCanonical(List<Part> placed, double sourceAngle)
+        {
+            if (placed == null || placed.Count == 0)
+                return placed;
+            if (Tolerance.IsEqualTo(sourceAngle, 0))
+                return placed;
+
+            foreach (var p in placed)
+                p.Rotate(sourceAngle, p.Location);
+
+            return placed;
+        }
+    }
+}

OpenNest.Engine/DefaultNestEngine.cs

@@ -47,14 +47,29 @@ namespace OpenNest
             PhaseResults.Clear();
             AngleResults.Clear();
 
-            // Fast path: for very small quantities, skip the full strategy pipeline.
+            // Replace the item's Drawing with a canonical copy for the duration of this fill.
-            if (item.Quantity > 0 && item.Quantity <= 2)
+            // All internal methods see canonical geometry; this wrapper un-canonicalizes the final result.
+            var sourceAngle = item.Drawing?.Source?.Angle ?? 0.0;
+            var originalDrawing = item.Drawing;
+            var canonicalItem = new NestItem
             {
-                var fast = TryFillSmallQuantity(item, workArea);
+                Drawing = CanonicalFrame.AsCanonicalCopy(item.Drawing),
-                if (fast != null && fast.Count >= item.Quantity)
+                Quantity = item.Quantity,
+                Priority = item.Priority,
+                RotationStart = item.RotationStart,
+                RotationEnd = item.RotationEnd,
+                StepAngle = item.StepAngle,
+            };
+
+            // Fast path for qty 1-2.
+            if (canonicalItem.Quantity > 0 && canonicalItem.Quantity <= 2)
             {
-                    Debug.WriteLine($"[Fill] Fast path: placed {fast.Count} parts for qty={item.Quantity}");
+                var fast = TryFillSmallQuantity(canonicalItem, workArea);
+                if (fast != null && fast.Count >= canonicalItem.Quantity)
+                {
+                    Debug.WriteLine($"[Fill] Fast path: placed {fast.Count} parts for qty={canonicalItem.Quantity}");
                     WinnerPhase = NestPhase.Pairs;
+                    fast = RebindAndUnCanonicalize(fast, originalDrawing, sourceAngle);
                     ReportProgress(progress, new ProgressReport
                     {
                         Phase = WinnerPhase,
@@ -68,32 +83,30 @@ namespace OpenNest
                 }
             }
 
-            // For low quantities, shrink the work area in both dimensions to avoid
-            // running expensive strategies against the full plate.
             var effectiveWorkArea = workArea;
-            if (item.Quantity > 0)
+            if (canonicalItem.Quantity > 0)
             {
-                effectiveWorkArea = ShrinkWorkArea(item, workArea, Plate.PartSpacing);
+                effectiveWorkArea = ShrinkWorkArea(canonicalItem, workArea, Plate.PartSpacing);
-
                 if (effectiveWorkArea != workArea)
-                    Debug.WriteLine($"[Fill] Low-qty shrink: {item.Quantity} requested, " +
+                    Debug.WriteLine($"[Fill] Low-qty shrink: {canonicalItem.Quantity} requested, " +
                         $"from {workArea.Width:F1}x{workArea.Length:F1} " +
                         $"to {effectiveWorkArea.Width:F1}x{effectiveWorkArea.Length:F1}");
             }
 
-            var best = RunFillPipeline(item, effectiveWorkArea, progress, token);
+            var best = RunFillPipeline(canonicalItem, effectiveWorkArea, progress, token);
 
-            // Fallback: if the reduced area didn't yield enough, retry with full area.
+            if (canonicalItem.Quantity > 0 && best.Count < canonicalItem.Quantity && effectiveWorkArea != workArea)
-            if (item.Quantity > 0 && best.Count < item.Quantity && effectiveWorkArea != workArea)
             {
-                Debug.WriteLine($"[Fill] Low-qty fallback: got {best.Count}, need {item.Quantity}, retrying full area");
+                Debug.WriteLine($"[Fill] Low-qty fallback: got {best.Count}, need {canonicalItem.Quantity}, retrying full area");
                 PhaseResults.Clear();
                 AngleResults.Clear();
-                best = RunFillPipeline(item, workArea, progress, token);
+                best = RunFillPipeline(canonicalItem, workArea, progress, token);
             }
 
-            if (item.Quantity > 0 && best.Count > item.Quantity)
+            if (canonicalItem.Quantity > 0 && best.Count > canonicalItem.Quantity)
-                best = ShrinkFiller.TrimToCount(best, item.Quantity, TrimAxis);
+                best = ShrinkFiller.TrimToCount(best, canonicalItem.Quantity, TrimAxis);
+
+            best = RebindAndUnCanonicalize(best, originalDrawing, sourceAngle);
 
             ReportProgress(progress, new ProgressReport
             {
@@ -108,6 +121,31 @@ namespace OpenNest
             return best;
         }
 
+        /// <summary>
+        /// Single exit point for canonical -> source frame conversion. Rebinds every Part to the
+        /// original Drawing (so consumers see the user's drawing identity, not the transient canonical copy)
+        /// and composes sourceAngle onto each Part's rotation via CanonicalFrame.FromCanonical.
+        /// </summary>
+        private static List<Part> RebindAndUnCanonicalize(List<Part> parts, Drawing original, double sourceAngle)
+        {
+            if (parts == null || parts.Count == 0)
+                return parts;
+
+            for (var i = 0; i < parts.Count; i++)
+            {
+                var p = parts[i];
+                // Rebind to `original` while preserving world pose. CreateAtOrigin rotates
+                // at the origin (keeping bbox at world (0,0)) then we offset to match p's bbox.
+                var rebound = Part.CreateAtOrigin(original, p.Rotation);
+                var delta = p.BoundingBox.Location - rebound.BoundingBox.Location;
+                rebound.Offset(delta);
+                rebound.UpdateBounds();
+                parts[i] = rebound;
+            }
+
+            return CanonicalFrame.FromCanonical(parts, sourceAngle);
+        }
+
         /// <summary>
         /// Fast path for qty 1-2: place a single part or a best-fit pair
         /// without running the full strategy pipeline.
@@ -139,6 +177,10 @@ namespace OpenNest
             var bestFits = BestFitCache.GetOrCompute(
                 drawing, Plate.Size.Length, Plate.Size.Width, Plate.PartSpacing);
 
+            // Build pair candidates with a canonical drawing so their geometry matches
+            // the coordinate frame of the cached fit results.
+            var canonicalDrawing = CanonicalFrame.AsCanonicalCopy(drawing);
+
             List<Part> bestPlacement = null;
 
             foreach (var fit in bestFits)
@@ -152,7 +194,7 @@ namespace OpenNest
                 if (fit.LongestSide > System.Math.Max(workArea.Width, workArea.Length) + Tolerance.Epsilon)
                     continue;
 
-                var landscape = fit.BuildParts(drawing);
+                var landscape = fit.BuildParts(canonicalDrawing);
                 var portrait = RotatePair90(landscape);
 
                 var lFits = TryOffsetToWorkArea(landscape, workArea);
@@ -174,6 +216,8 @@ namespace OpenNest
                     bestPlacement = candidate;
             }
 
+            // Parts are returned in canonical frame, bound to the canonical drawing.
+            // The outer Fill wrapper (Task 7) rebinds to `drawing` and composes sourceAngle onto rotation.
             return bestPlacement;
         }
 

OpenNest.Engine/Fill/FillLinear.cs

@@ -61,92 +61,91 @@ namespace OpenNest.Engine.Fill
                 : NestDirection.Horizontal;
         }
 
-        /// <summary>
-        /// Computes the slide distance for the push algorithm, returning the
-        /// geometry-aware copy distance along the given axis.
-        /// </summary>
-        private double ComputeCopyDistance(double bboxDim, double slideDistance)
-        {
-            if (slideDistance >= double.MaxValue || slideDistance < 0)
-                return bboxDim + PartSpacing;
-
-            // The geometry-aware slide can produce a copy distance smaller than
-            // the part itself when inflated corner/arc vertices interact spuriously.
-            // Clamp to bboxDim + PartSpacing to prevent bounding box overlap.
-            return System.Math.Max(bboxDim - slideDistance, bboxDim + PartSpacing);
-        }
-
         /// <summary>
         /// Finds the geometry-aware copy distance between two identical parts along an axis.
-        /// Both parts are inflated by half-spacing for symmetric spacing.
+        /// Uses native Line/Arc entities (inflated by half-spacing) so curves are handled
+        /// exactly without polygon sampling error.
         /// </summary>
-        private double FindCopyDistance(Part partA, NestDirection direction, PartBoundary boundary)
+        private double FindCopyDistance(Part partA, NestDirection direction)
         {
             var bboxDim = GetDimension(partA.BoundingBox, direction);
             var pushDir = GetPushDirection(direction);
+            var startOffset = bboxDim + PartSpacing + Tolerance.Epsilon;
+            var offset = MakeOffset(direction, startOffset);
 
-            var locationBOffset = MakeOffset(direction, bboxDim);
+            var stationaryEntities = PartGeometry.GetOffsetPerimeterEntities(partA, HalfSpacing);
+            var movingEntities = PartGeometry.GetOffsetPerimeterEntities(
+                partA.CloneAtOffset(offset), HalfSpacing);
 
-            // Use the most efficient array-based overload to avoid all allocations.
             var slideDistance = SpatialQuery.DirectionalDistance(
-                boundary.GetEdges(pushDir), partA.Location + locationBOffset,
+                movingEntities, stationaryEntities, pushDir);
-                boundary.GetEdges(SpatialQuery.OppositeDirection(pushDir)), partA.Location,
-                pushDir);
 
-            return ComputeCopyDistance(bboxDim, slideDistance);
+            if (slideDistance >= double.MaxValue || slideDistance < 0)
+                return bboxDim + PartSpacing;
+
+            return startOffset - slideDistance;
         }
 
         /// <summary>
         /// Finds the geometry-aware copy distance between two identical patterns along an axis.
-        /// Checks every pair of parts across adjacent patterns so that multi-part
+        /// Checks every pair of parts across adjacent pattern copies so multi-part patterns
-        /// patterns (e.g. interlocking pairs) maintain spacing between ALL parts.
+        /// (e.g. interlocking pairs) maintain spacing between ALL parts. Uses native entity
-        /// Both sides are inflated by half-spacing for symmetric spacing.
+        /// geometry inflated by half-spacing — same primitive the Compactor uses — so arcs
+        /// are exact and no bbox clamp is needed.
         /// </summary>
-        private double FindPatternCopyDistance(Pattern patternA, NestDirection direction, PartBoundary[] boundaries)
+        private double FindPatternCopyDistance(Pattern patternA, NestDirection direction)
         {
-            if (patternA.Parts.Count <= 1)
+            if (patternA.Parts.Count == 1)
-                return FindSinglePartPatternCopyDistance(patternA, direction, boundaries[0]);
+                return FindCopyDistance(patternA.Parts[0], direction);
 
             var bboxDim = GetDimension(patternA.BoundingBox, direction);
             var pushDir = GetPushDirection(direction);
             var opposite = SpatialQuery.OppositeDirection(pushDir);
+            var dirVec = SpatialQuery.DirectionToOffset(pushDir, 1.0);
 
             // bboxDim already spans max(upper) - min(lower) across all parts,
             // so the start offset just needs to push beyond that plus spacing.
             var startOffset = bboxDim + PartSpacing + Tolerance.Epsilon;
             var offset = MakeOffset(direction, startOffset);
 
-            var maxCopyDistance = FindMaxPairDistance(
+            var parts = patternA.Parts;
-                patternA.Parts, boundaries, offset, pushDir, opposite, startOffset);
+            var stationaryBoxes = new Box[parts.Count];
+            var movingBoxes = new Box[parts.Count];
+            var stationaryEntities = new List<Entity>[parts.Count];
+            var movingEntities = new List<Entity>[parts.Count];
 
-            // The copy distance must be at least bboxDim + PartSpacing to prevent
+            for (var i = 0; i < parts.Count; i++)
-            // bounding box overlap. Cross-pair slides can underestimate when the
+            {
-            // circumscribed polygon boundary overshoots the true arc, creating
+                stationaryBoxes[i] = parts[i].BoundingBox;
-            // spurious contacts between diagonal parts in adjacent copies.
+                movingBoxes[i] = stationaryBoxes[i].Translate(offset);
-            return System.Math.Max(maxCopyDistance, bboxDim + PartSpacing);
             }
 
-        /// <summary>
-        /// Tests every pair of parts across adjacent pattern copies and returns the
-        /// maximum copy distance found. Returns 0 if no valid slide was found.
-        /// </summary>
-        private static double FindMaxPairDistance(
-            List<Part> parts, PartBoundary[] boundaries, Vector offset,
-            PushDirection pushDir, PushDirection opposite, double startOffset)
-        {
             var maxCopyDistance = 0.0;
 
             for (var j = 0; j < parts.Count; j++)
             {
-                var movingEdges = boundaries[j].GetEdges(pushDir);
+                var movingBox = movingBoxes[j];
-                var locationB = parts[j].Location + offset;
 
                 for (var i = 0; i < parts.Count; i++)
                 {
+                    var stationaryBox = stationaryBoxes[i];
+
+                    // Skip if stationary is already ahead of moving in the push direction
+                    // (sliding forward would take them further apart).
+                    if (SpatialQuery.DirectionalGap(movingBox, stationaryBox, opposite) > 0)
+                        continue;
+
+                    // Skip if bboxes can't overlap along the axis perpendicular to the push.
+                    if (!SpatialQuery.PerpendicularOverlap(movingBox, stationaryBox, dirVec))
+                        continue;
+
+                    stationaryEntities[i] ??= PartGeometry.GetOffsetPerimeterEntities(
+                        parts[i], HalfSpacing);
+                    movingEntities[j] ??= PartGeometry.GetOffsetPerimeterEntities(
+                        parts[j].CloneAtOffset(offset), HalfSpacing);
+
                     var slideDistance = SpatialQuery.DirectionalDistance(
-                        movingEdges, locationB,
+                        movingEntities[j], stationaryEntities[i], pushDir);
-                        boundaries[i].GetEdges(opposite), parts[i].Location,
-                        pushDir);
 
                     if (slideDistance >= double.MaxValue || slideDistance < 0)
                         continue;
@@ -161,86 +160,15 @@ namespace OpenNest.Engine.Fill
             return maxCopyDistance;
         }
 
-        /// <summary>
-        /// Fast path for single-part patterns — no cross-part conflicts possible.
-        /// </summary>
-        private double FindSinglePartPatternCopyDistance(Pattern patternA, NestDirection direction, PartBoundary boundary)
-        {
-            var template = patternA.Parts[0];
-            return FindCopyDistance(template, direction, boundary);
-        }
-
-        /// <summary>
-        /// Gets offset boundary lines for all parts in a pattern using a shared boundary.
-        /// </summary>
-        private static List<Line> GetPatternLines(Pattern pattern, PartBoundary boundary, PushDirection direction)
-        {
-            var lines = new List<Line>();
-
-            foreach (var part in pattern.Parts)
-                lines.AddRange(boundary.GetLines(part.Location, direction));
-
-            return lines;
-        }
-
-        /// <summary>
-        /// Gets boundary lines for all parts in a pattern, with an additional
-        /// location offset applied. Avoids cloning the pattern.
-        /// </summary>
-        private static List<Line> GetOffsetPatternLines(Pattern pattern, Vector offset, PartBoundary boundary, PushDirection direction)
-        {
-            var lines = new List<Line>();
-
-            foreach (var part in pattern.Parts)
-                lines.AddRange(boundary.GetLines(part.Location + offset, direction));
-
-            return lines;
-        }
-
-        /// <summary>
-        /// Creates boundaries for all parts in a pattern. Parts that share the same
-        /// program geometry (same drawing and rotation) reuse the same boundary instance.
-        /// </summary>
-        private PartBoundary[] CreateBoundaries(Pattern pattern)
-        {
-            var boundaries = new PartBoundary[pattern.Parts.Count];
-            var cache = new List<(Drawing drawing, double rotation, PartBoundary boundary)>();
-
-            for (var i = 0; i < pattern.Parts.Count; i++)
-            {
-                var part = pattern.Parts[i];
-                PartBoundary found = null;
-
-                foreach (var entry in cache)
-                {
-                    if (entry.drawing == part.BaseDrawing && entry.rotation.IsEqualTo(part.Rotation))
-                    {
-                        found = entry.boundary;
-                        break;
-                    }
-                }
-
-                if (found == null)
-                {
-                    found = new PartBoundary(part, HalfSpacing);
-                    cache.Add((part.BaseDrawing, part.Rotation, found));
-                }
-
-                boundaries[i] = found;
-            }
-
-            return boundaries;
-        }
-
         /// <summary>
         /// Tiles a pattern along the given axis, returning the cloned parts
         /// (does not include the original pattern's parts). For multi-part
         /// patterns, also adds individual parts from the next incomplete copy
         /// that still fit within the work area.
         /// </summary>
-        private List<Part> TilePattern(Pattern basePattern, NestDirection direction, PartBoundary[] boundaries)
+        private List<Part> TilePattern(Pattern basePattern, NestDirection direction)
         {
-            var copyDistance = FindPatternCopyDistance(basePattern, direction, boundaries);
+            var copyDistance = FindPatternCopyDistance(basePattern, direction);
 
             if (copyDistance <= 0)
                 return new List<Part>();
@@ -394,11 +322,10 @@ namespace OpenNest.Engine.Fill
         private List<Part> FillGrid(Pattern pattern, NestDirection direction)
         {
             var perpAxis = PerpendicularAxis(direction);
-            var boundaries = CreateBoundaries(pattern);
 
             // Step 1: Tile along primary axis
             var row = new List<Part>(pattern.Parts);
-            row.AddRange(TilePattern(pattern, direction, boundaries));
+            row.AddRange(TilePattern(pattern, direction));
 
             if (pattern.Parts.Count > 1 && HasOverlappingParts(row, out var a1, out var b1))
             {
@@ -410,7 +337,7 @@ namespace OpenNest.Engine.Fill
             // If primary tiling didn't produce copies, just tile along perpendicular
             if (row.Count <= pattern.Parts.Count)
             {
-                row.AddRange(TilePattern(pattern, perpAxis, boundaries));
+                row.AddRange(TilePattern(pattern, perpAxis));
 
                 if (pattern.Parts.Count > 1 && HasOverlappingParts(row, out var a2, out var b2))
                 {
@@ -427,9 +354,8 @@ namespace OpenNest.Engine.Fill
             rowPattern.Parts.AddRange(row);
             rowPattern.UpdateBounds();
 
-            var rowBoundaries = CreateBoundaries(rowPattern);
             var gridResult = new List<Part>(rowPattern.Parts);
-            gridResult.AddRange(TilePattern(rowPattern, perpAxis, rowBoundaries));
+            gridResult.AddRange(TilePattern(rowPattern, perpAxis));
 
             if (HasOverlappingParts(gridResult, out var a3, out var b3))
             {
@@ -481,9 +407,8 @@ namespace OpenNest.Engine.Fill
                 return seed;
 
             var template = seed.Parts[0];
-            var boundary = new PartBoundary(template, HalfSpacing);
 
-            var copyDistance = FindCopyDistance(template, direction, boundary);
+            var copyDistance = FindCopyDistance(template, direction);
 
             if (copyDistance <= 0)
                 return seed;

OpenNest.Engine/ML/FeatureExtractor.cs

@@ -27,7 +27,10 @@ namespace OpenNest.Engine.ML
     {
         public static PartFeatures Extract(Drawing drawing)
         {
-            var entities = OpenNest.Converters.ConvertProgram.ToGeometry(drawing.Program)
+            // Normalize to canonical frame so features are invariant to import orientation.
+            var canonical = CanonicalFrame.AsCanonicalCopy(drawing);
+
+            var entities = OpenNest.Converters.ConvertProgram.ToGeometry(canonical.Program)
                 .Where(e => e.Layer != SpecialLayers.Rapid)
                 .ToList();
 
@@ -45,18 +48,18 @@ namespace OpenNest.Engine.ML
 
             var features = new PartFeatures
             {
-                Area = drawing.Area,
+                Area = canonical.Area,
-                Convexity = drawing.Area / (hullArea > 0 ? hullArea : 1.0),
+                Convexity = canonical.Area / (hullArea > 0 ? hullArea : 1.0),
                 AspectRatio = bb.Length / (bb.Width > 0 ? bb.Width : 1.0),
-                BoundingBoxFill = drawing.Area / (bb.Area() > 0 ? bb.Area() : 1.0),
+                BoundingBoxFill = canonical.Area / (bb.Area() > 0 ? bb.Area() : 1.0),
                 VertexCount = polygon.Vertices.Count,
                 Bitmask = GenerateBitmask(polygon, 32)
             };
 
             // Circularity = 4 * PI * Area / Perimeter^2
             var perimeterLen = polygon.Perimeter();
-            features.Circularity = (4 * System.Math.PI * drawing.Area) / (perimeterLen * perimeterLen);
+            features.Circularity = (4 * System.Math.PI * canonical.Area) / (perimeterLen * perimeterLen);
-            features.PerimeterToAreaRatio = drawing.Area > 0 ? perimeterLen / drawing.Area : 0;
+            features.PerimeterToAreaRatio = canonical.Area > 0 ? perimeterLen / canonical.Area : 0;
 
             return features;
         }

OpenNest.Engine/NestEngineBase.cs

@@ -334,6 +334,12 @@ namespace OpenNest
                 var bestFits = BestFitCache.GetOrCompute(
                     item.Drawing, Plate.Size.Length, Plate.Size.Width, Plate.PartSpacing);
 
+                // BestFitCache stores pair coordinates in canonical frame. Build candidates
+                // from a canonical drawing copy so geometry and coords share a frame; rebind
+                // + un-rotate winning pair to the original drawing's frame before returning.
+                var canonicalDrawing = CanonicalFrame.AsCanonicalCopy(item.Drawing);
+                var sourceAngle = item.Drawing?.Source?.Angle ?? 0.0;
+
                 List<Part> bestPlacement = null;
                 Box bestTarget = null;
 
@@ -342,7 +348,7 @@ namespace OpenNest
                     if (!fit.Keep)
                         continue;
 
-                    var parts = fit.BuildParts(item.Drawing);
+                    var parts = fit.BuildParts(canonicalDrawing);
                     var pairBbox = ((IEnumerable<IBoundable>)parts).GetBoundingBox();
                     var pairW = pairBbox.Width;
                     var pairL = pairBbox.Length;
@@ -374,6 +380,10 @@ namespace OpenNest
 
                 if (bestPlacement == null) continue;
 
+                // Rebind to the original drawing and compose sourceAngle onto rotation so the
+                // final placed parts sit in the user's visible frame.
+                bestPlacement = RebindPairToOriginal(bestPlacement, item.Drawing, sourceAngle);
+
                 result.AddRange(bestPlacement);
                 item.Quantity = 0;
 
@@ -388,6 +398,30 @@ namespace OpenNest
             return result;
         }
 
+        /// <summary>
+        /// Rebinds each canonical-frame Part in the pair to the original Drawing at its current
+        /// world pose, then composes sourceAngle onto each via CanonicalFrame.FromCanonical so
+        /// the returned list is in the original drawing's visible frame. Mirrors
+        /// DefaultNestEngine.RebindAndUnCanonicalize.
+        /// </summary>
+        private static List<Part> RebindPairToOriginal(List<Part> parts, Drawing original, double sourceAngle)
+        {
+            if (parts == null || parts.Count == 0)
+                return parts;
+
+            for (var i = 0; i < parts.Count; i++)
+            {
+                var p = parts[i];
+                var rebound = Part.CreateAtOrigin(original, p.Rotation);
+                var delta = p.BoundingBox.Location - rebound.BoundingBox.Location;
+                rebound.Offset(delta);
+                rebound.UpdateBounds();
+                parts[i] = rebound;
+            }
+
+            return CanonicalFrame.FromCanonical(parts, sourceAngle);
+        }
+
         /// <summary>
         /// Determines whether a drawing should use grid-fill (true) or bin-pack (false).
         /// Low-quantity items whose total area is a small fraction of the plate are

OpenNest.Engine/PartClassifier.cs

@@ -64,8 +64,8 @@ namespace OpenNest.Engine
             var mbrArea = mbr.Area;
             var mbrPerimeter = 2 * (mbr.Width + mbr.Height);
 
-            // Store primary angle (negated to align MBR with axes, same as RotationAnalysis).
+            // Share the single angle formula with CanonicalAngle (no duplicate MBR compute).
-            result.PrimaryAngle = -mbr.Angle;
+            result.PrimaryAngle = CanonicalAngle.FromMbr(mbr);
 
             // Drawing perimeter for circularity and perimeter ratio.
             var drawingPerimeter = polygon.Perimeter();

OpenNest.IO/Bending/SolidWorksBendDetector.cs

@@ -133,7 +133,7 @@ namespace OpenNest.IO.Bending
         {
             return document.Entities
                 .OfType<ACadSharp.Entities.Line>()
-                .Where(l => l.Layer?.Name == "BEND"
+                .Where(l => (l.Layer?.Name == "BEND" || l.Layer?.Name == "0")
                     && (l.LineType?.Name?.Contains("CENTER") == true
                         || l.LineType?.Name == "CENTERX2"))
                 .ToList();

OpenNest.IO/Bom/BomAnalyzer.cs

@@ -42,6 +42,11 @@ namespace OpenNest.IO.Bom
                     var nameWithoutExt = Path.GetFileNameWithoutExtension(file);
                     dxfFiles[nameWithoutExt] = file;
                 }
+                foreach (var file in Directory.GetFiles(dxfFolder, "*.dwg"))
+                {
+                    var nameWithoutExt = Path.GetFileNameWithoutExtension(file);
+                    dxfFiles.TryAdd(nameWithoutExt, file);
+                }
             }
 
             // Partition items into: skipped, unmatched, or matched (grouped)
@@ -57,8 +62,8 @@ namespace OpenNest.IO.Bom
 
                 var lookupName = item.FileName;
 
-                // Strip .dxf extension if the BOM includes it
+                if (lookupName.EndsWith(".dxf", StringComparison.OrdinalIgnoreCase)
-                if (lookupName.EndsWith(".dxf", StringComparison.OrdinalIgnoreCase))
+                    || lookupName.EndsWith(".dwg", StringComparison.OrdinalIgnoreCase))
                     lookupName = Path.GetFileNameWithoutExtension(lookupName);
 
                 if (!folderExists)

OpenNest.IO/CadImportOptions.cs

@@ -16,6 +16,11 @@ namespace OpenNest.IO
         /// </summary>
         public bool DetectBends { get; set; } = true;
 
+        /// <summary>
+        /// When true, detects and identifies title block entities during import. Default true.
+        /// </summary>
+        public bool DetectTitleBlock { get; set; } = true;
+
         /// <summary>
         /// Override the drawing name. Null = filename without extension.
         /// </summary>

OpenNest.IO/CadImportResult.cs

@@ -1,4 +1,5 @@
 using System.Collections.Generic;
+using ACadSharp;
 using OpenNest.Bending;
 using OpenNest.Geometry;
 
@@ -38,5 +39,16 @@ namespace OpenNest.IO
         /// Default drawing name (filename without extension, unless overridden).
         /// </summary>
         public string Name { get; set; }
+
+        /// <summary>
+        /// The raw CAD document from the source file. Available for callers
+        /// that need access to non-geometry entities (e.g., text annotations).
+        /// </summary>
+        public CadDocument Document { get; set; }
+
+        /// <summary>
+        /// GUIDs of entities identified as part of the title block during import.
+        /// </summary>
+        public HashSet<System.Guid> TitleBlockEntityIds { get; set; }
     }
 }

OpenNest.IO/CadImporter.cs

@@ -5,6 +5,7 @@ using OpenNest.Bending;
 using OpenNest.Converters;
 using OpenNest.Geometry;
 using OpenNest.IO.Bending;
+using OpenNest.Math;
 
 namespace OpenNest.IO
 {
@@ -25,6 +26,9 @@ namespace OpenNest.IO
 
             var dxf = Dxf.Import(path);
 
+            RemoveDuplicateArcs(dxf.Entities);
+            RemoveZeroSweepArcs(dxf.Entities);
+
             var bends = new List<Bend>();
             if (options.DetectBends && dxf.Document != null)
             {
@@ -37,6 +41,10 @@ namespace OpenNest.IO
 
             Bend.UpdateEtchEntities(dxf.Entities, bends);
 
+            HashSet<System.Guid> titleBlockIds = null;
+            if (options.DetectTitleBlock)
+                titleBlockIds = TitleBlockDetector.Detect(dxf.Entities, dxf.Document);
+
             return new CadImportResult
             {
                 Entities = dxf.Entities,
@@ -44,6 +52,8 @@ namespace OpenNest.IO
                 Bounds = dxf.Entities.GetBoundingBox(),
                 SourcePath = path,
                 Name = options.Name ?? Path.GetFileNameWithoutExtension(path),
+                Document = dxf.Document,
+                TitleBlockEntityIds = titleBlockIds,
             };
         }
 
@@ -134,7 +144,51 @@ namespace OpenNest.IO
                     .Where(e => !(e.Layer != null && e.Layer.IsVisible && e.IsVisible))
                     .Select(e => e.Id));
 
+            if (result.TitleBlockEntityIds != null)
+            {
+                var sourceIds = new HashSet<System.Guid>(drawing.SourceEntities.Select(e => e.Id));
+                foreach (var id in result.TitleBlockEntityIds)
+                {
+                    if (sourceIds.Contains(id))
+                        drawing.SuppressedEntityIds.Add(id);
+                }
+            }
+
             return drawing;
         }
+
+        internal static void RemoveZeroSweepArcs(List<Entity> entities)
+        {
+            entities.RemoveAll(e =>
+                e is Arc arc && arc.StartAngle.IsEqualTo(arc.EndAngle, Tolerance.ChainTolerance));
+        }
+
+        internal static void RemoveDuplicateArcs(List<Entity> entities)
+        {
+            var circles = entities.OfType<Circle>().ToList();
+            var arcs = entities.OfType<Arc>().ToList();
+            var arcsToRemove = new List<Arc>();
+
+            foreach (var arc in arcs)
+            {
+                foreach (var circle in circles)
+                {
+                    if (arc.Layer?.Name != circle.Layer?.Name)
+                        continue;
+
+                    if (!arc.Center.DistanceTo(circle.Center).IsEqualTo(0))
+                        continue;
+
+                    if (!arc.Radius.IsEqualTo(circle.Radius))
+                        continue;
+
+                    arcsToRemove.Add(arc);
+                    break;
+                }
+            }
+
+            foreach (var arc in arcsToRemove)
+                entities.Remove(arc);
+        }
     }
 }

OpenNest.IO/Dxf.cs

@@ -27,8 +27,7 @@ namespace OpenNest.IO
         /// </summary>
         public static DxfImportResult Import(string path)
         {
-            using var reader = new DxfReader(path);
+            var doc = ReadDocument(path);
-            var doc = reader.Read();
 
             return new DxfImportResult
             {
@@ -41,8 +40,7 @@ namespace OpenNest.IO
         {
             try
             {
-                using var reader = new DxfReader(path);
+                var doc = ReadDocument(path);
-                var doc = reader.Read();
                 return ConvertEntities(doc);
             }
             catch (Exception ex)
@@ -113,11 +111,29 @@ namespace OpenNest.IO
 
         #region Private
 
+        private static bool IsDwg(string path) =>
+            Path.GetExtension(path).Equals(".dwg", StringComparison.OrdinalIgnoreCase);
+
+        private static CadDocument ReadDocument(string path)
+        {
+            if (IsDwg(path))
+            {
+                using var reader = new DwgReader(path);
+                return reader.Read();
+            }
+            else
+            {
+                using var reader = new DxfReader(path);
+                return reader.Read();
+            }
+        }
+
         private static List<Entity> ConvertEntities(CadDocument doc)
         {
             var entities = new List<Entity>();
             var lines = new List<Line>();
             var arcs = new List<Arc>();
+            var circles = new List<Circle>();
 
             foreach (var entity in doc.Entities)
             {
@@ -135,7 +151,7 @@ namespace OpenNest.IO
                         break;
 
                     case ACadSharp.Entities.Circle circle:
-                        entities.Add(circle.ToOpenNest());
+                        circles.Add(circle.ToOpenNest());
                         break;
 
                     case ACadSharp.Entities.Spline spline:
@@ -166,7 +182,10 @@ namespace OpenNest.IO
 
             GeometryOptimizer.Optimize(lines);
             GeometryOptimizer.Optimize(arcs);
+            GeometryOptimizer.Deduplicate(circles);
+            GeometryOptimizer.Deduplicate(circles, arcs);
 
+            entities.AddRange(circles);
             entities.AddRange(lines);
             entities.AddRange(arcs);
 

OpenNest.IO/Extensions.cs

@@ -181,13 +181,22 @@ namespace OpenNest.IO
         {
             var center = new Vector(ellipse.Center.X, ellipse.Center.Y);
             var majorAxis = new Vector(ellipse.MajorAxisEndPoint.X, ellipse.MajorAxisEndPoint.Y);
-            var semiMajor = System.Math.Sqrt(majorAxis.X * majorAxis.X + majorAxis.Y * majorAxis.Y);
-            var semiMinor = semiMajor * ellipse.RadiusRatio;
-            var rotation = System.Math.Atan2(majorAxis.Y, majorAxis.X);
 
             var startParam = ellipse.StartParameter;
             var endParam = ellipse.EndParameter;
 
+            if (ellipse.Normal.Z < 0)
+            {
+                var newStart = OpenNest.Math.Angle.TwoPI - endParam;
+                var newEnd = OpenNest.Math.Angle.TwoPI - startParam;
+                startParam = newStart;
+                endParam = newEnd;
+            }
+
+            var semiMajor = System.Math.Sqrt(majorAxis.X * majorAxis.X + majorAxis.Y * majorAxis.Y);
+            var semiMinor = semiMajor * ellipse.RadiusRatio;
+            var rotation = System.Math.Atan2(majorAxis.Y, majorAxis.X);
+
             var layer = ellipse.Layer.ToOpenNest();
             var color = ellipse.ResolveColor();
             var lineTypeName = ellipse.ResolveLineTypeName();

OpenNest.IO/OpenNest.IO.csproj

@@ -4,6 +4,9 @@
     <RootNamespace>OpenNest.IO</RootNamespace>
     <AssemblyName>OpenNest.IO</AssemblyName>
   </PropertyGroup>
+  <ItemGroup>
+    <InternalsVisibleTo Include="OpenNest.Tests" />
+  </ItemGroup>
   <ItemGroup>
     <ProjectReference Include="..\OpenNest.Core\OpenNest.Core.csproj" />
     <ProjectReference Include="..\OpenNest.Engine\OpenNest.Engine.csproj" />

OpenNest.IO/TitleBlockDetector.cs

@@ -0,0 +1,312 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using ACadSharp;
+using OpenNest.Geometry;
+
+namespace OpenNest.IO
+{
+    public static class TitleBlockDetector
+    {
+        private static readonly HashSet<string> TitleBlockLayerNames = new(StringComparer.OrdinalIgnoreCase)
+        {
+            "TITLE", "TITLEBLOCK", "TITLE_BLOCK", "BORDER", "FRAME",
+            "TB", "INFO", "SHEET", "ANNOTATION"
+        };
+
+        public static HashSet<Guid> Detect(List<Entity> entities, CadDocument document)
+        {
+            var flagged = new HashSet<Guid>();
+            DetectByLayerName(entities, flagged);
+            DetectBorder(entities, flagged);
+            if (document != null)
+                DetectTitleBlockRegion(entities, document, flagged);
+            return flagged;
+        }
+
+        private static void DetectByLayerName(List<Entity> entities, HashSet<Guid> flagged)
+        {
+            foreach (var entity in entities)
+            {
+                if (entity.Layer?.Name != null && TitleBlockLayerNames.Contains(entity.Layer.Name))
+                    flagged.Add(entity.Id);
+            }
+        }
+
+        private static void DetectBorder(List<Entity> entities, HashSet<Guid> flagged)
+        {
+            var lines = entities.OfType<Line>().Where(l => !flagged.Contains(l.Id)).ToList();
+            if (lines.Count < 4) return;
+
+            var bounds = entities.GetBoundingBox();
+            if (bounds == null || bounds.Area() < OpenNest.Math.Tolerance.Epsilon) return;
+
+            var borderCount = 0;
+            foreach (var line in lines)
+            {
+                if (IsBorderLine(line, bounds))
+                {
+                    flagged.Add(line.Id);
+                    borderCount++;
+                }
+            }
+
+            if (borderCount >= 2)
+                DetectZoneMarkers(lines, bounds, flagged);
+        }
+
+        private static bool IsBorderLine(Line line, Box bounds)
+        {
+            var dx = line.EndPoint.X - line.StartPoint.X;
+            var dy = line.EndPoint.Y - line.StartPoint.Y;
+            var length = System.Math.Sqrt(dx * dx + dy * dy);
+            var angleRad = System.Math.Atan2(System.Math.Abs(dy), System.Math.Abs(dx));
+            var angularTolerance = OpenNest.Math.Angle.ToRadians(2.0);
+            var positionTolerance = System.Math.Max(bounds.Length, bounds.Width) * 0.01;
+
+            var isHorizontal = angleRad < angularTolerance;
+            var isVertical = System.Math.Abs(angleRad - System.Math.PI / 2) < angularTolerance;
+
+            if (!isHorizontal && !isVertical) return false;
+
+            var minSpan = isHorizontal ? bounds.Length * 0.8 : bounds.Width * 0.8;
+            if (length < minSpan) return false;
+
+            if (isHorizontal)
+            {
+                var midY = (line.StartPoint.Y + line.EndPoint.Y) / 2;
+                return System.Math.Abs(midY - bounds.Bottom) < positionTolerance
+                    || System.Math.Abs(midY - bounds.Top) < positionTolerance;
+            }
+            else
+            {
+                var midX = (line.StartPoint.X + line.EndPoint.X) / 2;
+                return System.Math.Abs(midX - bounds.Left) < positionTolerance
+                    || System.Math.Abs(midX - bounds.Right) < positionTolerance;
+            }
+        }
+
+        private static void DetectZoneMarkers(List<Line> lines, Box bounds, HashSet<Guid> flagged)
+        {
+            var positionTolerance = System.Math.Max(bounds.Length, bounds.Width) * 0.01;
+            var maxTickLength = System.Math.Max(bounds.Length, bounds.Width) * 0.05;
+            var angularTolerance = OpenNest.Math.Angle.ToRadians(2.0);
+
+            foreach (var line in lines)
+            {
+                if (flagged.Contains(line.Id)) continue;
+
+                var dx = line.EndPoint.X - line.StartPoint.X;
+                var dy = line.EndPoint.Y - line.StartPoint.Y;
+                var length = System.Math.Sqrt(dx * dx + dy * dy);
+
+                if (length > maxTickLength || length < OpenNest.Math.Tolerance.Epsilon) continue;
+
+                var angleRad = System.Math.Atan2(System.Math.Abs(dy), System.Math.Abs(dx));
+                var isVertical = System.Math.Abs(angleRad - System.Math.PI / 2) < angularTolerance;
+                var isHorizontal = angleRad < angularTolerance;
+
+                if (!isVertical && !isHorizontal) continue;
+
+                var touchesEdge = false;
+                if (isVertical)
+                {
+                    var minY = System.Math.Min(line.StartPoint.Y, line.EndPoint.Y);
+                    var maxY = System.Math.Max(line.StartPoint.Y, line.EndPoint.Y);
+                    touchesEdge = System.Math.Abs(minY - bounds.Bottom) < positionTolerance
+                               || System.Math.Abs(maxY - bounds.Top) < positionTolerance;
+                }
+                else if (isHorizontal)
+                {
+                    var minX = System.Math.Min(line.StartPoint.X, line.EndPoint.X);
+                    var maxX = System.Math.Max(line.StartPoint.X, line.EndPoint.X);
+                    touchesEdge = System.Math.Abs(minX - bounds.Left) < positionTolerance
+                               || System.Math.Abs(maxX - bounds.Right) < positionTolerance;
+                }
+
+                if (touchesEdge)
+                    flagged.Add(line.Id);
+            }
+        }
+
+        private static void DetectTitleBlockRegion(List<Entity> entities, CadDocument document, HashSet<Guid> flagged)
+        {
+            var textPositions = ExtractTextPositions(document);
+            if (textPositions.Count < 3) return;
+
+            var unflagged = entities.Where(e => !flagged.Contains(e.Id)).ToList();
+            if (unflagged.Count == 0) return;
+
+            var bounds = entities.GetBoundingBox();
+            if (bounds == null || bounds.Area() < OpenNest.Math.Tolerance.Epsilon) return;
+
+            var bestRegion = FindBestTitleBlockRegion(bounds, textPositions, unflagged);
+            if (bestRegion == null) return;
+
+            var initiallyInside = unflagged.Where(e => {
+                var c = EntityCenter(e);
+                return c.HasValue && RegionContains(bestRegion, c.Value);
+            }).ToList();
+
+            var expandedBounds = initiallyInside.Count > 0 ? initiallyInside.GetBoundingBox() : null;
+
+            foreach (var entity in unflagged)
+            {
+                var center = EntityCenter(entity);
+                if (!center.HasValue) continue;
+                if (RegionContains(bestRegion, center.Value)
+                    || (expandedBounds != null && RegionContains(expandedBounds, center.Value)))
+                    flagged.Add(entity.Id);
+            }
+        }
+
+        private static List<Vector> ExtractTextPositions(CadDocument document)
+        {
+            var positions = new List<Vector>();
+            foreach (var entity in document.Entities)
+            {
+                switch (entity)
+                {
+                    case ACadSharp.Entities.MText mtext:
+                        positions.Add(new Vector(mtext.InsertPoint.X, mtext.InsertPoint.Y));
+                        break;
+                    case ACadSharp.Entities.TextEntity text:
+                        var pt = text.HorizontalAlignment != 0 || text.VerticalAlignment != 0
+                            ? text.AlignmentPoint : text.InsertPoint;
+                        positions.Add(new Vector(pt.X, pt.Y));
+                        break;
+                }
+            }
+            return positions;
+        }
+
+        private static Box FindBestTitleBlockRegion(Box bounds, List<Vector> textPositions, List<Entity> entities)
+        {
+            var candidates = GenerateCandidateRegions(bounds);
+            Box bestRegion = null;
+            var bestScore = 0.0;
+
+            var openLines = FindOpenLines(entities);
+
+            foreach (var region in candidates)
+            {
+                var textCount = textPositions.Count(p => RegionContains(region, p));
+                if (textCount < 3) continue;
+
+                var openLineCount = openLines.Count(l => RegionContains(region, l.MidPoint));
+
+                var area = region.Area();
+                if (area < OpenNest.Math.Tolerance.Epsilon) continue;
+
+                var score = (double)textCount + openLineCount * 0.5;
+
+                var regionCenterX = (region.Left + region.Right) / 2;
+                var regionCenterY = (region.Bottom + region.Top) / 2;
+                if (regionCenterX > bounds.Center.X) score *= 1.3;
+                if (regionCenterY < bounds.Center.Y) score *= 1.3;
+
+                if (score > bestScore)
+                {
+                    bestScore = score;
+                    bestRegion = region;
+                }
+            }
+
+            return bestRegion;
+        }
+
+        private static List<Box> GenerateCandidateRegions(Box bounds)
+        {
+            var regions = new List<Box>();
+            var fractions = new[] { 0.25, 0.333, 0.5 };
+
+            foreach (var fx in fractions)
+            {
+                foreach (var fy in fractions)
+                {
+                    var w = bounds.Length * fx;
+                    var h = bounds.Width * fy;
+
+                    regions.Add(new Box(bounds.Right - w, bounds.Bottom, w, h));
+                    regions.Add(new Box(bounds.Left, bounds.Bottom, w, h));
+                    regions.Add(new Box(bounds.Right - w, bounds.Top - h, w, h));
+                    regions.Add(new Box(bounds.Left, bounds.Top - h, w, h));
+                }
+            }
+
+            foreach (var fy in fractions)
+            {
+                var h = bounds.Width * fy;
+                regions.Add(new Box(bounds.Left, bounds.Bottom, bounds.Length, h));
+            }
+
+            foreach (var fx in fractions)
+            {
+                var w = bounds.Length * fx;
+                regions.Add(new Box(bounds.Right - w, bounds.Bottom, w, bounds.Width));
+            }
+
+            return regions;
+        }
+
+        private static List<Line> FindOpenLines(List<Entity> entities)
+        {
+            var endpointUsers = new Dictionary<long, int>();
+
+            foreach (var entity in entities)
+            {
+                foreach (var ep in GetEntityEndpoints(entity))
+                {
+                    var key = QuantizePoint(ep);
+                    endpointUsers[key] = endpointUsers.GetValueOrDefault(key) + 1;
+                }
+            }
+
+            var openLines = new List<Line>();
+            foreach (var line in entities.OfType<Line>())
+            {
+                var startKey = QuantizePoint(line.StartPoint);
+                var endKey = QuantizePoint(line.EndPoint);
+
+                if (endpointUsers.GetValueOrDefault(startKey) <= 1 || endpointUsers.GetValueOrDefault(endKey) <= 1)
+                    openLines.Add(line);
+            }
+
+            return openLines;
+        }
+
+        private static List<Vector> GetEntityEndpoints(Entity entity)
+        {
+            return entity switch
+            {
+                Line line => new List<Vector> { line.StartPoint, line.EndPoint },
+                Arc arc => new List<Vector> { arc.StartPoint(), arc.EndPoint() },
+                _ => new List<Vector>()
+            };
+        }
+
+        private static long QuantizePoint(Vector pt)
+        {
+            var qx = (long)(pt.X * 1000);
+            var qy = (long)(pt.Y * 1000);
+            return qx * 100000000L + qy;
+        }
+
+        private static Vector? EntityCenter(Entity entity)
+        {
+            return entity switch
+            {
+                Line line => line.MidPoint,
+                Arc arc => arc.Center,
+                Circle circle => circle.Center,
+                _ => null
+            };
+        }
+
+        private static bool RegionContains(Box box, Vector pt)
+        {
+            return pt.X >= box.Left && pt.X <= box.Right
+                && pt.Y >= box.Bottom && pt.Y <= box.Top;
+        }
+    }
+}

OpenNest.Tests/CNC/RapidEnumeratorTests.cs

@@ -0,0 +1,84 @@
+using OpenNest.CNC;
+using OpenNest.Geometry;
+using Xunit;
+
+namespace OpenNest.Tests.CNC
+{
+    public class RapidEnumeratorTests
+    {
+        [Fact]
+        public void Enumerate_AbsoluteProgram_OffsetsMotionsByBasePos()
+        {
+            var pgm = new Program(Mode.Absolute);
+            pgm.Codes.Add(new RapidMove(1, 0));
+            pgm.Codes.Add(new LinearMove(2, 0));
+            pgm.Codes.Add(new RapidMove(3, 3));
+
+            var segments = RapidEnumerator.Enumerate(pgm, basePos: new Vector(100, 200), startPos: new Vector(0, 0));
+
+            // Origin → first pierce, then interior rapid from contour end to next rapid target.
+            Assert.Equal(2, segments.Count);
+            Assert.Equal(new Vector(0, 0), segments[0].From);
+            Assert.Equal(new Vector(101, 200), segments[0].To);
+            Assert.Equal(new Vector(102, 200), segments[1].From);
+            Assert.Equal(new Vector(103, 203), segments[1].To);
+        }
+
+        [Fact]
+        public void Enumerate_IncrementalProgram_InterpretsDeltasFromBasePos()
+        {
+            // Pre-lead-in raw program: first rapid normalized to (0,0), Mode=Incremental
+            // (matches ConvertGeometry.ToProgram output).
+            var pgm = new Program(Mode.Incremental);
+            pgm.Codes.Add(new RapidMove(0, 0));
+            pgm.Codes.Add(new LinearMove(5, 0));
+            pgm.Codes.Add(new LinearMove(0, 5));
+            pgm.Codes.Add(new RapidMove(1, 1));
+
+            var segments = RapidEnumerator.Enumerate(pgm, basePos: new Vector(100, 200), startPos: new Vector(0, 0));
+
+            Assert.Equal(2, segments.Count);
+            // First rapid: plate origin → part pierce at basePos.
+            Assert.Equal(new Vector(0, 0), segments[0].From);
+            Assert.Equal(new Vector(100, 200), segments[0].To);
+            // Interior rapid: after deltas (5,0) and (0,5) from basePos, rapid delta (1,1).
+            Assert.Equal(new Vector(105, 205), segments[1].From);
+            Assert.Equal(new Vector(106, 206), segments[1].To);
+        }
+
+        [Fact]
+        public void Enumerate_SubProgramCall_RapidEndsAtAbsoluteHolePierce()
+        {
+            // Main program: lead-in rapid, a line, then a SubProgramCall for a hole.
+            // Sub-program (incremental) starts with RapidMove(radius, 0) to the hole pierce.
+            var sub = new Program(Mode.Incremental);
+            sub.Codes.Add(new RapidMove(0.5, 0));
+            sub.Codes.Add(new LinearMove(0, 0.1));
+
+            var pgm = new Program(Mode.Absolute);
+            pgm.Codes.Add(new RapidMove(0.2, 0.3));             // first pierce (perimeter lead-in)
+            pgm.Codes.Add(new LinearMove(1.0, 1.0));             // contour move
+            pgm.Codes.Add(new SubProgramCall
+            {
+                Id = 1,
+                Program = sub,
+                Offset = new Vector(2, 2),                       // hole center (drawing-local)
+            });
+
+            var basePos = new Vector(100, 200);                  // part.Location
+            var segments = RapidEnumerator.Enumerate(pgm, basePos, startPos: new Vector(0, 0));
+
+            // Expected rapids:
+            //  1. origin → first pierce (0.2+100, 0.3+200) = (100.2, 200.3)
+            //  2. end of contour (1+100, 1+200) = (101, 201) → hole pierce (2+100+0.5, 2+200) = (102.5, 202)
+            //  The sub's internal first rapid is skipped (already drawn in #2).
+            Assert.Equal(2, segments.Count);
+
+            Assert.Equal(new Vector(0, 0), segments[0].From);
+            Assert.Equal(new Vector(100.2, 200.3), segments[0].To);
+
+            Assert.Equal(new Vector(101, 201), segments[1].From);
+            Assert.Equal(new Vector(102.5, 202), segments[1].To);
+        }
+    }
+}

OpenNest.Tests/Engine/CanonicalAngleTests.cs

@@ -0,0 +1,156 @@
+using System.Linq;
+using OpenNest.CNC;
+using OpenNest.Converters;
+using OpenNest.Engine;
+using OpenNest.Geometry;
+using OpenNest.Math;
+
+namespace OpenNest.Tests.Engine;
+
+public class CanonicalAngleTests
+{
+    private const double AngleTol = 0.002; // ~0.11°
+
+    private static Drawing MakeRect(double w, double h)
+    {
+        var pgm = new OpenNest.CNC.Program();
+        pgm.Codes.Add(new RapidMove(new Vector(0, 0)));
+        pgm.Codes.Add(new LinearMove(new Vector(w, 0)));
+        pgm.Codes.Add(new LinearMove(new Vector(w, h)));
+        pgm.Codes.Add(new LinearMove(new Vector(0, h)));
+        pgm.Codes.Add(new LinearMove(new Vector(0, 0)));
+        return new Drawing("rect", pgm);
+    }
+
+    private static Drawing RotateCopy(Drawing src, double angle)
+    {
+        var pgm = src.Program.Clone() as OpenNest.CNC.Program;
+        pgm.Rotate(angle, pgm.BoundingBox().Center);
+        return new Drawing("rotated", pgm);
+    }
+
+    [Fact]
+    public void AxisAlignedRectangle_ReturnsZero()
+    {
+        var d = MakeRect(100, 50);
+        Assert.Equal(0.0, CanonicalAngle.Compute(d), precision: 6);
+    }
+
+    // Program.BoundingBox() has a pre-existing bug where minX/minY initialize to 0 and can
+    // only decrease, so programs whose extents stay in the positive half-plane report a
+    // too-large AABB. To validate MBR-axis-alignment without tripping that bug, extract the
+    // outer perimeter polygon and compute its true AABB from vertices.
+    private static (double length, double width) TrueAabb(OpenNest.CNC.Program pgm)
+    {
+        var entities = ConvertProgram.ToGeometry(pgm).Where(e => e.Layer != SpecialLayers.Rapid);
+        var shapes = ShapeBuilder.GetShapes(entities);
+        var outer = shapes.OrderByDescending(s => s.Area()).First();
+        var poly = outer.ToPolygonWithTolerance(0.1);
+        var minX = poly.Vertices.Min(v => v.X);
+        var maxX = poly.Vertices.Max(v => v.X);
+        var minY = poly.Vertices.Min(v => v.Y);
+        var maxY = poly.Vertices.Max(v => v.Y);
+        return (maxX - minX, maxY - minY);
+    }
+
+    [Theory]
+    [InlineData(0.3)]
+    [InlineData(0.7)]
+    [InlineData(1.2)]
+    public void Rectangle_ReturnsNegatedRotation_Modulo90(double theta)
+    {
+        var rotated = RotateCopy(MakeRect(100, 50), theta);
+        var angle = CanonicalAngle.Compute(rotated);
+
+        // Applying the returned angle should leave MBR axis-aligned.
+        var canonical = rotated.Program.Clone() as OpenNest.CNC.Program;
+        canonical.Rotate(angle, canonical.BoundingBox().Center);
+
+        var (length, width) = TrueAabb(canonical);
+        var longer = System.Math.Max(length, width);
+        var shorter = System.Math.Min(length, width);
+        Assert.InRange(longer, 100 - 0.1, 100 + 0.1);
+        Assert.InRange(shorter, 50 - 0.1, 50 + 0.1);
+    }
+
+    [Fact]
+    public void NearZeroInput_SnapsToZero()
+    {
+        var rotated = RotateCopy(MakeRect(100, 50), 0.0005);
+        Assert.Equal(0.0, CanonicalAngle.Compute(rotated), precision: 6);
+    }
+
+    [Fact]
+    public void DegeneratePolygon_ReturnsZero()
+    {
+        var pgm = new OpenNest.CNC.Program();
+        pgm.Codes.Add(new RapidMove(new Vector(0, 0)));
+        pgm.Codes.Add(new LinearMove(new Vector(10, 10)));
+        var d = new Drawing("line", pgm);
+        Assert.Equal(0.0, CanonicalAngle.Compute(d), precision: 6);
+    }
+
+    [Fact]
+    public void EmptyProgram_ReturnsZero()
+    {
+        var d = new Drawing("empty", new OpenNest.CNC.Program());
+        Assert.Equal(0.0, CanonicalAngle.Compute(d), precision: 6);
+    }
+}
+
+public class DrawingCanonicalAngleWiringTests
+{
+    private static OpenNest.CNC.Program RotatedRectProgram(double w, double h, double theta)
+    {
+        var pgm = new OpenNest.CNC.Program();
+        pgm.Codes.Add(new RapidMove(new Vector(0, 0)));
+        pgm.Codes.Add(new LinearMove(new Vector(w, 0)));
+        pgm.Codes.Add(new LinearMove(new Vector(w, h)));
+        pgm.Codes.Add(new LinearMove(new Vector(0, h)));
+        pgm.Codes.Add(new LinearMove(new Vector(0, 0)));
+        if (!OpenNest.Math.Tolerance.IsEqualTo(theta, 0))
+            pgm.Rotate(theta, pgm.BoundingBox().Center);
+        return pgm;
+    }
+
+    [Fact]
+    public void Constructor_ComputesAngleOnProgramAssignment()
+    {
+        var pgm = RotatedRectProgram(100, 50, 0.5);
+        var d = new Drawing("r", pgm);
+        Assert.InRange(d.Source.Angle, -0.52, -0.48);
+    }
+
+    [Fact]
+    public void SetProgram_RecomputesAngle()
+    {
+        var d = new Drawing("r", RotatedRectProgram(100, 50, 0.0));
+        Assert.Equal(0.0, d.Source.Angle, precision: 6);
+
+        d.Program = RotatedRectProgram(100, 50, 0.5);
+        Assert.InRange(d.Source.Angle, -0.52, -0.48);
+    }
+
+    [Fact]
+    public void IsCutOff_SkipsAngleComputation()
+    {
+        var d = new Drawing("cut", RotatedRectProgram(100, 50, 0.5)) { IsCutOff = true };
+        // Re-assign after flag is set so the setter observes IsCutOff.
+        d.Program = RotatedRectProgram(100, 50, 0.5);
+        Assert.Equal(0.0, d.Source.Angle, precision: 6);
+    }
+
+    [Fact]
+    public void RecomputeCanonicalAngle_UpdatesAfterMutation()
+    {
+        var d = new Drawing("r", RotatedRectProgram(100, 50, 0.0));
+        Assert.Equal(0.0, d.Source.Angle, precision: 6);
+
+        // Mutate in-place (doesn't trigger setter).
+        d.Program.Rotate(0.5, d.Program.BoundingBox().Center);
+        Assert.Equal(0.0, d.Source.Angle, precision: 6); // still stale
+
+        d.RecomputeCanonicalAngle();
+        Assert.InRange(d.Source.Angle, -0.52, -0.48);
+    }
+}

OpenNest.Tests/Engine/CanonicalFrameTests.cs

@@ -0,0 +1,84 @@
+using OpenNest.CNC;
+using OpenNest.Engine;
+using OpenNest.Geometry;
+using OpenNest.Math;
+
+namespace OpenNest.Tests.Engine;
+
+public class CanonicalFrameTests
+{
+    private static Drawing MakeRect(double w, double h, double rotation)
+    {
+        var pgm = new OpenNest.CNC.Program();
+        pgm.Codes.Add(new RapidMove(new Vector(0, 0)));
+        pgm.Codes.Add(new LinearMove(new Vector(w, 0)));
+        pgm.Codes.Add(new LinearMove(new Vector(w, h)));
+        pgm.Codes.Add(new LinearMove(new Vector(0, h)));
+        pgm.Codes.Add(new LinearMove(new Vector(0, 0)));
+        if (!Tolerance.IsEqualTo(rotation, 0))
+            pgm.Rotate(rotation, pgm.BoundingBox().Center);
+        return new Drawing("rect", pgm) { Source = new SourceInfo { Angle = -rotation } };
+    }
+
+    [Fact]
+    public void AsCanonicalCopy_AxisAlignsMbr()
+    {
+        var d = MakeRect(100, 50, 0.6);
+        var canonical = CanonicalFrame.AsCanonicalCopy(d);
+
+        var bb = canonical.Program.BoundingBox();
+        var longer = System.Math.Max(bb.Length, bb.Width);
+        var shorter = System.Math.Min(bb.Length, bb.Width);
+        Assert.InRange(longer, 100 - 0.1, 100 + 0.1);
+        Assert.InRange(shorter, 50 - 0.1, 50 + 0.1);
+        Assert.Equal(0.0, canonical.Source.Angle, precision: 6);
+    }
+
+    [Fact]
+    public void AsCanonicalCopy_DoesNotMutateSource()
+    {
+        var d = MakeRect(100, 50, 0.6);
+        var originalBbox = d.Program.BoundingBox();
+        var originalAngle = d.Source.Angle;
+
+        CanonicalFrame.AsCanonicalCopy(d);
+
+        var afterBbox = d.Program.BoundingBox();
+        Assert.Equal(originalBbox.Width, afterBbox.Width, precision: 6);
+        Assert.Equal(originalBbox.Length, afterBbox.Length, precision: 6);
+        Assert.Equal(originalAngle, d.Source.Angle, precision: 6);
+    }
+
+    [Fact]
+    public void FromCanonical_ComposesSourceAngleOntoRotation()
+    {
+        var d = MakeRect(100, 50, 0.0);
+        var part = new Part(d);
+        part.Rotate(0.2); // engine returned a canonical-frame part at R = 0.2
+
+        var placed = CanonicalFrame.FromCanonical(new List<Part> { part }, sourceAngle: -0.5);
+
+        // R' = R + sourceAngle = 0.2 + (-0.5) = -0.3
+        // Part.Rotation comes from Program.Rotation which is normalized to [0, 2PI),
+        // so compare after normalizing the expected value as well.
+        Assert.Single(placed);
+        Assert.Equal(Angle.NormalizeRad(-0.3), placed[0].Rotation, precision: 4);
+    }
+
+    [Fact]
+    public void RoundTrip_RestoresGeometry()
+    {
+        var d = MakeRect(100, 50, 0.4);
+        var canonical = CanonicalFrame.AsCanonicalCopy(d);
+
+        // Place a part at origin in the canonical frame.
+        var part = Part.CreateAtOrigin(canonical);
+        var canonicalBbox = part.BoundingBox;
+
+        var placed = CanonicalFrame.FromCanonical(new List<Part> { part }, d.Source.Angle);
+
+        var originalBbox = d.Program.BoundingBox();
+        Assert.Equal(originalBbox.Width, placed[0].BoundingBox.Width, precision: 2);
+        Assert.Equal(originalBbox.Length, placed[0].BoundingBox.Length, precision: 2);
+    }
+}

OpenNest.Tests/Engine/NestInvarianceTests.cs

@@ -0,0 +1,84 @@
+using OpenNest.CNC;
+using OpenNest.Engine;
+using OpenNest.Engine.BestFit;
+using OpenNest.Geometry;
+using OpenNest.Math;
+using System.Threading;
+
+namespace OpenNest.Tests.Engine;
+
+public class NestInvarianceTests
+{
+    private static OpenNest.CNC.Program MakeLShapedProgram()
+    {
+        // L-shape: 100x50 outer rect with a 50x30 notch removed from top-right.
+        var pgm = new OpenNest.CNC.Program();
+        pgm.Codes.Add(new RapidMove(new Vector(0, 0)));
+        pgm.Codes.Add(new LinearMove(new Vector(100, 0)));
+        pgm.Codes.Add(new LinearMove(new Vector(100, 20)));
+        pgm.Codes.Add(new LinearMove(new Vector(50, 20)));
+        pgm.Codes.Add(new LinearMove(new Vector(50, 50)));
+        pgm.Codes.Add(new LinearMove(new Vector(0, 50)));
+        pgm.Codes.Add(new LinearMove(new Vector(0, 0)));
+        return pgm;
+    }
+
+    private static Drawing MakeImportedAt(double rotation)
+    {
+        var pgm = MakeLShapedProgram();
+        if (!Tolerance.IsEqualTo(rotation, 0))
+            pgm.Rotate(rotation, pgm.BoundingBox().Center);
+        return new Drawing("L", pgm);
+    }
+
+    private static Plate MakePlate() => new Plate(new Size(500, 500))
+    {
+        Quadrant = 1,
+        PartSpacing = 2,
+    };
+
+    private static int RunFillCount(Drawing drawing, Plate plate)
+    {
+        BestFitCache.Clear();
+        var engine = new DefaultNestEngine(plate);
+        var item = new NestItem { Drawing = drawing };
+        var parts = engine.Fill(item, plate.WorkArea(), progress: null, token: CancellationToken.None);
+        return parts?.Count ?? 0;
+    }
+
+    [Theory]
+    [InlineData(0.0)]
+    [InlineData(0.3)]
+    [InlineData(0.8)]
+    [InlineData(1.2)]
+    public void Fill_SameCount_AcrossImportOrientations(double theta)
+    {
+        var baseline = RunFillCount(MakeImportedAt(0.0), MakePlate());
+        var rotated = RunFillCount(MakeImportedAt(theta), MakePlate());
+
+        // Allow +/-1 tolerance for sweep quantization edge effects near plate boundaries.
+        Assert.InRange(rotated, baseline - 1, baseline + 1);
+    }
+
+    [Fact]
+    public void Fill_PlacedPartsStayWithinWorkArea_AcrossImportOrientations()
+    {
+        var plate = MakePlate();
+        var workArea = plate.WorkArea();
+
+        foreach (var theta in new[] { 0.0, 0.3, 0.8, 1.2 })
+        {
+            BestFitCache.Clear();
+            var engine = new DefaultNestEngine(plate);
+            var item = new NestItem { Drawing = MakeImportedAt(theta) };
+            var parts = engine.Fill(item, workArea, progress: null, token: CancellationToken.None);
+
+            Assert.NotNull(parts);
+            foreach (var p in parts)
+            {
+                Assert.InRange(p.BoundingBox.Left, workArea.Left - 0.5, workArea.Right + 0.5);
+                Assert.InRange(p.BoundingBox.Bottom, workArea.Bottom - 0.5, workArea.Top + 0.5);
+            }
+        }
+    }
+}

OpenNest.Tests/Fill/CompactorTests.cs

@@ -8,6 +8,76 @@ namespace OpenNest.Tests.Fill
 {
     public class CompactorTests
     {
+        [Fact]
+        public void DirectionalDistance_ArcVsInclinedLine_DoesNotOverPush()
+        {
+            // Arc (top semicircle) pushed upward toward a 45° inclined line.
+            // The critical angle on the arc gives a shorter distance than any
+            // sampled vertex (endpoints + cardinal extremes).
+            var arc = new Arc(5, 0, 2, 0, System.Math.PI);
+            var line = new Line(new Vector(3, 4), new Vector(7, 6));
+
+            var moving = new List<Entity> { arc };
+            var stationary = new List<Entity> { line };
+            var direction = new Vector(0, 1); // push up
+
+            var dist = SpatialQuery.DirectionalDistance(moving, stationary, direction);
+
+            // Move the arc up by the computed distance, then verify no overlap.
+            // The topmost reachable point on the arc at the critical angle θ ≈ 2.034
+            // (between π/2 and π) should just touch the line.
+            Assert.True(dist < double.MaxValue, "Should find a finite distance");
+            Assert.True(dist > 0, "Should be a positive distance");
+
+            // Verify: after moving, the closest point on the arc should be within
+            // tolerance of the line, not past it.
+            var theta = System.Math.Atan2(
+                line.pt2.X - line.pt1.X, -(line.pt2.Y - line.pt1.Y));
+            theta = OpenNest.Math.Angle.NormalizeRad(theta + System.Math.PI);
+            var qx = arc.Center.X + arc.Radius * System.Math.Cos(theta);
+            var qy = arc.Center.Y + arc.Radius * System.Math.Sin(theta) + dist;
+
+            // The moved point should be on or just touching the line, not past it.
+            // Line equation: (y - 4) / (x - 3) = (6 - 4) / (7 - 3) = 0.5
+            // y = 0.5x + 2.5
+            var lineYAtQx = 0.5 * qx + 2.5;
+            Assert.True(qy <= lineYAtQx + 0.001,
+                $"Arc point ({qx:F4}, {qy:F4}) should not be past line (line Y={lineYAtQx:F4} at X={qx:F4}). " +
+                $"dist={dist:F6}, overshot by {qy - lineYAtQx:F6}");
+        }
+
+        [Fact]
+        public void DirectionalDistance_ArcVsInclinedLine_BetterThanVertexSampling()
+        {
+            // Same geometry — verify the analytical Phase 3 finds a shorter
+            // distance than the Phase 1/2 vertex sampling alone would.
+            var arc = new Arc(5, 0, 2, 0, System.Math.PI);
+            var line = new Line(new Vector(3, 4), new Vector(7, 6));
+
+            // Phase 1/2 vertex-only distance: sample arc endpoints + cardinal extreme.
+            var vertices = new[]
+            {
+                new Vector(7, 0),  // arc endpoint θ=0
+                new Vector(3, 0),  // arc endpoint θ=π
+                new Vector(5, 2),  // cardinal extreme θ=π/2
+            };
+
+            var vertexMin = double.MaxValue;
+            foreach (var v in vertices)
+            {
+                var d = SpatialQuery.RayEdgeDistance(v.X, v.Y,
+                    line.pt1.X, line.pt1.Y, line.pt2.X, line.pt2.Y, 0, 1);
+                if (d < vertexMin) vertexMin = d;
+            }
+
+            // Full directional distance (includes Phase 3 arc-to-line).
+            var moving = new List<Entity> { arc };
+            var stationary = new List<Entity> { line };
+            var fullDist = SpatialQuery.DirectionalDistance(moving, stationary, new Vector(0, 1));
+
+            Assert.True(fullDist < vertexMin,
+                $"Full distance ({fullDist:F6}) should be less than vertex-only ({vertexMin:F6})");
+        }
         private static Drawing MakeRectDrawing(double w, double h)
         {
             var pgm = new OpenNest.CNC.Program();

OpenNest.Tests/Geometry/BoxComparisonTests.cs

@@ -0,0 +1,97 @@
+using System;
+using System.Collections.Generic;
+using OpenNest.Geometry;
+using Xunit;
+
+namespace OpenNest.Tests.Geometry;
+
+public class BoxComparisonTests
+{
+    [Fact]
+    public void GreaterThan_TallerBox_ReturnsTrue()
+    {
+        var tall = new Box(0, 0, 10, 20);
+        var short_ = new Box(0, 0, 10, 10);
+
+        Assert.True(tall > short_);
+        Assert.False(short_ > tall);
+    }
+
+    [Fact]
+    public void GreaterThan_SameWidthLongerBox_ReturnsTrue()
+    {
+        var longer = new Box(0, 0, 20, 10);
+        var shorter = new Box(0, 0, 10, 10);
+
+        Assert.True(longer > shorter);
+        Assert.False(shorter > longer);
+    }
+
+    [Fact]
+    public void LessThan_ShorterBox_ReturnsTrue()
+    {
+        var tall = new Box(0, 0, 10, 20);
+        var short_ = new Box(0, 0, 10, 10);
+
+        Assert.True(short_ < tall);
+        Assert.False(tall < short_);
+    }
+
+    [Fact]
+    public void GreaterThanOrEqual_EqualBoxes_ReturnsTrue()
+    {
+        var a = new Box(0, 0, 10, 20);
+        var b = new Box(0, 0, 10, 20);
+
+        Assert.True(a >= b);
+        Assert.True(b >= a);
+    }
+
+    [Fact]
+    public void LessThanOrEqual_EqualBoxes_ReturnsTrue()
+    {
+        var a = new Box(0, 0, 10, 20);
+        var b = new Box(0, 0, 10, 20);
+
+        Assert.True(a <= b);
+        Assert.True(b <= a);
+    }
+
+    [Fact]
+    public void CompareTo_TallerBox_ReturnsPositive()
+    {
+        var tall = new Box(0, 0, 10, 20);
+        var short_ = new Box(0, 0, 10, 10);
+
+        Assert.True(tall.CompareTo(short_) > 0);
+        Assert.True(short_.CompareTo(tall) < 0);
+    }
+
+    [Fact]
+    public void CompareTo_EqualBoxes_ReturnsZero()
+    {
+        var a = new Box(0, 0, 10, 20);
+        var b = new Box(0, 0, 10, 20);
+
+        Assert.Equal(0, a.CompareTo(b));
+    }
+
+    [Fact]
+    public void Sort_OrdersByWidthThenLength()
+    {
+        var boxes = new List<Box>
+        {
+            new Box(0, 0, 20, 10),
+            new Box(0, 0, 5, 30),
+            new Box(0, 0, 10, 10),
+        };
+
+        boxes.Sort();
+
+        Assert.Equal(10, boxes[0].Width);
+        Assert.Equal(10, boxes[0].Length);
+        Assert.Equal(10, boxes[1].Width);
+        Assert.Equal(20, boxes[1].Length);
+        Assert.Equal(30, boxes[2].Width);
+    }
+}

OpenNest.Tests/Geometry/EllipseConverterTests.cs

@@ -1,14 +1,19 @@
 using OpenNest.Geometry;
+using OpenNest.IO;
 using OpenNest.Math;
 using Xunit;
+using Xunit.Abstractions;
 using System.Linq;
 
 namespace OpenNest.Tests.Geometry;
 
 public class EllipseConverterTests
 {
+    private readonly ITestOutputHelper _output;
     private const double Tol = 1e-10;
 
+    public EllipseConverterTests(ITestOutputHelper output) => _output = output;
+
     [Fact]
     public void EvaluatePoint_AtZero_ReturnsMajorAxisEnd()
     {
@@ -244,6 +249,101 @@ public class EllipseConverterTests
         }
     }
 
+    [Fact]
+    public void DxfImport_ArcBoundingBoxes_Diagnostic()
+    {
+        var path = @"C:\Users\aisaacs\Desktop\11ga tab.dxf";
+        if (!System.IO.File.Exists(path)) return;
+
+        var result = Dxf.Import(path);
+        var all = (System.Collections.Generic.IEnumerable<IBoundable>)result.Entities;
+        var bbox = all.GetBoundingBox();
+        _output.WriteLine($"Overall: X={bbox.X:F4} Y={bbox.Y:F4} W={bbox.Length:F4} H={bbox.Width:F4}");
+
+        for (var i = 0; i < result.Entities.Count; i++)
+        {
+            var e = result.Entities[i];
+            var b = e.BoundingBox;
+            var flag = (b.Length > 1 || b.Width > 1) ? " ***" : "";
+            _output.WriteLine($"{i + 1,3}. {e.GetType().Name,-8} X={b.X:F4} Y={b.Y:F4} W={b.Length:F4} H={b.Width:F4}{flag}");
+        }
+    }
+
+    [Fact]
+    public void ToOpenNest_FlippedNormalZ_ProducesCorrectArcs()
+    {
+        var normal = new ACadSharp.Entities.Ellipse
+        {
+            Center = new CSMath.XYZ(-0.275, -0.245, 0),
+            MajorAxisEndPoint = new CSMath.XYZ(0.0001, 1.245, 0),
+            RadiusRatio = 0.28,
+            StartParameter = 0.017,
+            EndParameter = 1.571,
+            Normal = new CSMath.XYZ(0, 0, 1)
+        };
+
+        var flipped = new ACadSharp.Entities.Ellipse
+        {
+            Center = new CSMath.XYZ(0.275, -0.245, 0),
+            MajorAxisEndPoint = new CSMath.XYZ(-0.0001, 1.245, 0),
+            RadiusRatio = 0.28,
+            StartParameter = 0.017,
+            EndParameter = 1.571,
+            Normal = new CSMath.XYZ(0, 0, -1)
+        };
+
+        var normalArcs = normal.ToOpenNest();
+        var flippedArcs = flipped.ToOpenNest();
+
+        Assert.True(normalArcs.Count > 0);
+        Assert.True(flippedArcs.Count > 0);
+        Assert.True(normalArcs.All(e => e is Arc));
+        Assert.True(flippedArcs.All(e => e is Arc));
+
+        var normalFirst = (Arc)normalArcs.First();
+        var flippedFirst = (Arc)flippedArcs.First();
+        var normalStart = GetArcStart(normalFirst);
+        var flippedStart = GetArcStart(flippedFirst);
+
+        Assert.True(normalStart.X < 0, $"Normal ellipse start X should be negative, got {normalStart.X}");
+        Assert.True(flippedStart.X > 0, $"Flipped ellipse should bulge right, got {flippedStart.X}");
+
+        var normalBbox = GetBoundingBox(normalArcs.Cast<Arc>());
+        var flippedBbox = GetBoundingBox(flippedArcs.Cast<Arc>());
+        Assert.True(flippedBbox.minX > 0, $"Flipped ellipse should stay on positive X side, minX={flippedBbox.minX}");
+        Assert.True(normalBbox.maxX < 0, $"Normal ellipse should stay on negative X side, maxX={normalBbox.maxX}");
+    }
+
+    private static (double minX, double maxX) GetBoundingBox(IEnumerable<Arc> arcs)
+    {
+        var minX = double.MaxValue;
+        var maxX = double.MinValue;
+        foreach (var arc in arcs)
+        {
+            var s = GetArcStart(arc);
+            var e = GetArcEnd(arc);
+            minX = System.Math.Min(minX, System.Math.Min(s.X, e.X));
+            maxX = System.Math.Max(maxX, System.Math.Max(s.X, e.X));
+        }
+        return (minX, maxX);
+    }
+
+    private static Vector GetArcStart(Arc arc)
+    {
+        var angle = arc.IsReversed ? arc.EndAngle : arc.StartAngle;
+        return new Vector(
+            arc.Center.X + arc.Radius * System.Math.Cos(angle),
+            arc.Center.Y + arc.Radius * System.Math.Sin(angle));
+    }
+
+    private static Vector GetArcEnd(Arc arc)
+    {
+        var angle = arc.IsReversed ? arc.StartAngle : arc.EndAngle;
+        return new Vector(
+            arc.Center.X + arc.Radius * System.Math.Cos(angle),
+            arc.Center.Y + arc.Radius * System.Math.Sin(angle));
+    }
+
     private static double MaxDeviationFromEllipse(Arc arc, Vector ellipseCenter,
         double semiMajor, double semiMinor, double rotation, int samples)
     {

OpenNest.Tests/Geometry/WeldEndpointsTests.cs

@@ -0,0 +1,72 @@
+using System.Collections.Generic;
+using OpenNest.Geometry;
+using OpenNest.Math;
+using Xunit;
+
+namespace OpenNest.Tests.Geometry;
+
+public class WeldEndpointsTests
+{
+    [Fact]
+    public void WeldEndpoints_SnapsNearbyLineEndpoints()
+    {
+        var line1 = new Line(0, 0, 10, 0);
+        var line2 = new Line(10.0000005, 0, 20, 0);
+        var entities = new List<Entity> { line1, line2 };
+
+        ShapeBuilder.WeldEndpoints(entities, 0.000001);
+
+        Assert.True(line1.EndPoint.DistanceTo(line2.StartPoint) <= Tolerance.Epsilon);
+    }
+
+    [Fact]
+    public void WeldEndpoints_SnapsArcEndpointByAdjustingAngle()
+    {
+        var line = new Line(0, 0, 10, 0);
+        var arc = new Arc(15, 0, 5, Angle.ToRadians(180.001), Angle.ToRadians(90));
+        var entities = new List<Entity> { line, arc };
+
+        ShapeBuilder.WeldEndpoints(entities, 0.01);
+
+        var arcStart = arc.StartPoint();
+        Assert.True(line.EndPoint.DistanceTo(arcStart) <= 0.01);
+    }
+
+    [Fact]
+    public void WeldEndpoints_DoesNotWeldDistantEndpoints()
+    {
+        var line1 = new Line(0, 0, 10, 0);
+        var line2 = new Line(10.1, 0, 20, 0);
+        var entities = new List<Entity> { line1, line2 };
+
+        ShapeBuilder.WeldEndpoints(entities, 0.000001);
+
+        Assert.True(line1.EndPoint.DistanceTo(line2.StartPoint) > 0.01);
+    }
+
+    [Fact]
+    public void GetShapes_WithWeldTolerance_WeldsBeforeChaining()
+    {
+        var line1 = new Line(0, 0, 10, 0);
+        var line2 = new Line(10.0000005, 0, 10.0000005, 10);
+        var entities = new List<Entity> { line1, line2 };
+
+        var shapes = ShapeBuilder.GetShapes(entities, weldTolerance: 0.000001);
+
+        Assert.Single(shapes);
+        Assert.Equal(2, shapes[0].Entities.Count);
+    }
+
+    [Fact]
+    public void GetShapes_WithoutWeldTolerance_DefaultBehavior()
+    {
+        var line1 = new Line(0, 0, 10, 0);
+        var line2 = new Line(10, 0, 10, 10);
+        var entities = new List<Entity> { line1, line2 };
+
+        var shapes = ShapeBuilder.GetShapes(entities);
+
+        Assert.Single(shapes);
+        Assert.Equal(2, shapes[0].Entities.Count);
+    }
+}

OpenNest.Tests/IO/CadImporterTests.cs

@@ -134,5 +134,21 @@ namespace OpenNest.Tests.IO
             Assert.NotNull(drawing.Program);
             Assert.NotNull(drawing.SourceEntities);
         }
+
+        [Fact]
+        public void Import_WhenDetectTitleBlockTrue_PopulatesTitleBlockEntityIds()
+        {
+            var result = CadImporter.Import(TestDxf);
+
+            Assert.NotNull(result.TitleBlockEntityIds);
+        }
+
+        [Fact]
+        public void Import_WhenDetectTitleBlockFalse_TitleBlockEntityIdsIsNull()
+        {
+            var result = CadImporter.Import(TestDxf, new CadImportOptions { DetectTitleBlock = false });
+
+            Assert.Null(result.TitleBlockEntityIds);
+        }
     }
 }

OpenNest.Tests/IO/RemoveDuplicateArcsTests.cs

@@ -0,0 +1,96 @@
+using System.Collections.Generic;
+using System.Linq;
+using OpenNest.Geometry;
+using OpenNest.IO;
+using OpenNest.Math;
+using Xunit;
+
+namespace OpenNest.Tests.IO;
+
+public class RemoveDuplicateArcsTests
+{
+    [Fact]
+    public void RemoveDuplicateArcs_RemovesArcMatchingCircle_SameLayer()
+    {
+        var layer = new Layer("0");
+        var circle = new Circle(10, 10, 5) { Layer = layer };
+        var arc = new Arc(10, 10, 5, 0, Angle.ToRadians(90)) { Layer = layer };
+        var line = new Line(0, 0, 10, 0) { Layer = layer };
+        var entities = new List<Entity> { circle, arc, line };
+
+        CadImporter.RemoveDuplicateArcs(entities);
+
+        Assert.Equal(2, entities.Count);
+        Assert.Contains(circle, entities);
+        Assert.Contains(line, entities);
+        Assert.DoesNotContain(arc, entities);
+    }
+
+    [Fact]
+    public void RemoveDuplicateArcs_KeepsArcOnDifferentLayer()
+    {
+        var layer1 = new Layer("cut");
+        var layer2 = new Layer("etch");
+        var circle = new Circle(10, 10, 5) { Layer = layer1 };
+        var arc = new Arc(10, 10, 5, 0, Angle.ToRadians(90)) { Layer = layer2 };
+        var entities = new List<Entity> { circle, arc };
+
+        CadImporter.RemoveDuplicateArcs(entities);
+
+        Assert.Equal(2, entities.Count);
+        Assert.Contains(arc, entities);
+    }
+
+    [Fact]
+    public void RemoveDuplicateArcs_KeepsArcWithDifferentRadius()
+    {
+        var layer = new Layer("0");
+        var circle = new Circle(10, 10, 5) { Layer = layer };
+        var arc = new Arc(10, 10, 3, 0, Angle.ToRadians(90)) { Layer = layer };
+        var entities = new List<Entity> { circle, arc };
+
+        CadImporter.RemoveDuplicateArcs(entities);
+
+        Assert.Equal(2, entities.Count);
+    }
+
+    [Fact]
+    public void RemoveDuplicateArcs_KeepsArcWithDifferentCenter()
+    {
+        var layer = new Layer("0");
+        var circle = new Circle(10, 10, 5) { Layer = layer };
+        var arc = new Arc(20, 20, 5, 0, Angle.ToRadians(90)) { Layer = layer };
+        var entities = new List<Entity> { circle, arc };
+
+        CadImporter.RemoveDuplicateArcs(entities);
+
+        Assert.Equal(2, entities.Count);
+    }
+
+    [Fact]
+    public void RemoveDuplicateArcs_NoCircles_NoChange()
+    {
+        var arc = new Arc(10, 10, 5, 0, Angle.ToRadians(90));
+        var line = new Line(0, 0, 10, 0);
+        var entities = new List<Entity> { arc, line };
+
+        CadImporter.RemoveDuplicateArcs(entities);
+
+        Assert.Equal(2, entities.Count);
+    }
+
+    [Fact]
+    public void RemoveDuplicateArcs_MultipleArcsMatchOneCircle_RemovesAll()
+    {
+        var layer = new Layer("0");
+        var circle = new Circle(10, 10, 5) { Layer = layer };
+        var arc1 = new Arc(10, 10, 5, 0, Angle.ToRadians(90)) { Layer = layer };
+        var arc2 = new Arc(10, 10, 5, Angle.ToRadians(90), Angle.ToRadians(180)) { Layer = layer };
+        var entities = new List<Entity> { circle, arc1, arc2 };
+
+        CadImporter.RemoveDuplicateArcs(entities);
+
+        Assert.Single(entities);
+        Assert.Contains(circle, entities);
+    }
+}

OpenNest.Tests/IO/TitleBlockDetectorTests.cs

@@ -0,0 +1,245 @@
+using System.Collections.Generic;
+using CSMath;
+using OpenNest.Geometry;
+using OpenNest.IO;
+using Xunit;
+
+namespace OpenNest.Tests.IO
+{
+    public class TitleBlockDetectorTests
+    {
+        private static Line MakeLine(double x1, double y1, double x2, double y2) =>
+            new Line(x1, y1, x2, y2);
+
+        [Fact]
+        public void DetectByLayerName_FlagsTitleLayer()
+        {
+            var line = MakeLine(0, 0, 10, 0);
+            line.Layer = new Layer("TITLE");
+            var entities = new List<Entity> { line };
+
+            var result = TitleBlockDetector.Detect(entities, null);
+
+            Assert.Contains(line.Id, result);
+        }
+
+        [Fact]
+        public void DetectByLayerName_CaseInsensitive()
+        {
+            var line = MakeLine(0, 0, 10, 0);
+            line.Layer = new Layer("border");
+            var entities = new List<Entity> { line };
+
+            var result = TitleBlockDetector.Detect(entities, null);
+
+            Assert.Contains(line.Id, result);
+        }
+
+        [Fact]
+        public void DetectByLayerName_IgnoresNonMatchingLayers()
+        {
+            var line = MakeLine(0, 0, 10, 0);
+            line.Layer = new Layer("0");
+            var entities = new List<Entity> { line };
+
+            var result = TitleBlockDetector.Detect(entities, null);
+
+            Assert.DoesNotContain(line.Id, result);
+        }
+
+        [Theory]
+        [InlineData("TITLE")]
+        [InlineData("TITLEBLOCK")]
+        [InlineData("TITLE_BLOCK")]
+        [InlineData("BORDER")]
+        [InlineData("FRAME")]
+        [InlineData("TB")]
+        [InlineData("INFO")]
+        [InlineData("SHEET")]
+        [InlineData("ANNOTATION")]
+        public void DetectByLayerName_AllKnownNames(string layerName)
+        {
+            var line = MakeLine(0, 0, 10, 0);
+            line.Layer = new Layer(layerName);
+            var entities = new List<Entity> { line };
+
+            var result = TitleBlockDetector.Detect(entities, null);
+
+            Assert.Contains(line.Id, result);
+        }
+
+        [Fact]
+        public void DetectBorder_FlagsLinesOnBoundingBoxEdges()
+        {
+            var entities = new List<Entity>
+            {
+                new Line(0, 0, 86, 0) { Layer = new Layer("0") },
+                new Line(86, 0, 86, 134) { Layer = new Layer("0") },
+                new Line(86, 134, 0, 134) { Layer = new Layer("0") },
+                new Line(0, 134, 0, 0) { Layer = new Layer("0") },
+                new Line(30, 40, 50, 90) { Layer = new Layer("0") },
+                new Line(50, 90, 70, 40) { Layer = new Layer("0") },
+                new Line(70, 40, 30, 40) { Layer = new Layer("0") },
+            };
+
+            var result = TitleBlockDetector.Detect(entities, null);
+
+            Assert.Contains(entities[0].Id, result);
+            Assert.Contains(entities[1].Id, result);
+            Assert.Contains(entities[2].Id, result);
+            Assert.Contains(entities[3].Id, result);
+            Assert.DoesNotContain(entities[4].Id, result);
+            Assert.DoesNotContain(entities[5].Id, result);
+            Assert.DoesNotContain(entities[6].Id, result);
+        }
+
+        [Fact]
+        public void DetectBorder_FlagsZoneMarkerTicks()
+        {
+            var entities = new List<Entity>
+            {
+                new Line(0, 0, 100, 0) { Layer = new Layer("0") },
+                new Line(100, 0, 100, 80) { Layer = new Layer("0") },
+                new Line(100, 80, 0, 80) { Layer = new Layer("0") },
+                new Line(0, 80, 0, 0) { Layer = new Layer("0") },
+                new Line(25, 80, 25, 77) { Layer = new Layer("0") },
+                new Line(50, 80, 50, 77) { Layer = new Layer("0") },
+                new Line(75, 80, 75, 77) { Layer = new Layer("0") },
+                new Line(40, 30, 60, 30) { Layer = new Layer("0") },
+            };
+
+            var result = TitleBlockDetector.Detect(entities, null);
+
+            Assert.Contains(entities[4].Id, result);
+            Assert.Contains(entities[5].Id, result);
+            Assert.Contains(entities[6].Id, result);
+            Assert.DoesNotContain(entities[7].Id, result);
+        }
+
+        [Fact]
+        public void DetectBorder_IgnoresWhenNoBorderPresent()
+        {
+            var entities = new List<Entity>
+            {
+                new Line(30, 40, 50, 90) { Layer = new Layer("0") },
+                new Line(50, 90, 70, 40) { Layer = new Layer("0") },
+                new Line(70, 40, 30, 40) { Layer = new Layer("0") },
+            };
+
+            var result = TitleBlockDetector.Detect(entities, null);
+
+            Assert.Empty(result);
+        }
+
+        [Fact]
+        public void DetectBorder_ToleratesSlightRotation()
+        {
+            var angleRad = OpenNest.Math.Angle.ToRadians(0.5);
+            var endY = 86 * System.Math.Sin(angleRad);
+            var entities = new List<Entity>
+            {
+                new Line(0, 0, 86, endY) { Layer = new Layer("0") },
+                new Line(86, endY, 86, 134) { Layer = new Layer("0") },
+                new Line(86, 134, 0, 134) { Layer = new Layer("0") },
+                new Line(0, 134, 0, 0) { Layer = new Layer("0") },
+                new Line(30, 40, 50, 90) { Layer = new Layer("0") },
+            };
+
+            var result = TitleBlockDetector.Detect(entities, null);
+
+            Assert.Contains(entities[0].Id, result);
+        }
+
+        [Fact]
+        public void DetectTitleBlock_FlagsEntitiesInTextDenseCorner()
+        {
+            var partLine1 = new Line(5, 70, 25, 120) { Layer = new Layer("0") };
+            var partLine2 = new Line(25, 120, 45, 70) { Layer = new Layer("0") };
+            var partLine3 = new Line(45, 70, 5, 70) { Layer = new Layer("0") };
+
+            var tbLines = new List<Entity>();
+            for (var x = 50; x <= 85; x += 5)
+                tbLines.Add(new Line(x, 0, x, 30) { Layer = new Layer("0") });
+            for (var y = 0; y <= 30; y += 5)
+                tbLines.Add(new Line(50, y, 85, y) { Layer = new Layer("0") });
+
+            var entities = new List<Entity> { partLine1, partLine2, partLine3 };
+            entities.AddRange(tbLines);
+
+            var doc = BuildDocWithTexts(
+                (60, 5, "TITLE: Test Part"),
+                (60, 10, "DWG NO: 12345"),
+                (60, 15, "SCALE: 1:1"),
+                (60, 20, "REV: A"),
+                (60, 25, "MATERIAL: STEEL"));
+
+            var result = TitleBlockDetector.Detect(entities, doc);
+
+            foreach (var tb in tbLines)
+                Assert.Contains(tb.Id, result);
+            Assert.DoesNotContain(partLine1.Id, result);
+            Assert.DoesNotContain(partLine2.Id, result);
+            Assert.DoesNotContain(partLine3.Id, result);
+        }
+
+        [Fact]
+        public void DetectTitleBlock_NoFalsePositivesWithoutText()
+        {
+            var entities = new List<Entity>
+            {
+                new Line(30, 40, 50, 90) { Layer = new Layer("0") },
+                new Line(50, 90, 70, 40) { Layer = new Layer("0") },
+                new Line(70, 40, 30, 40) { Layer = new Layer("0") },
+            };
+
+            var result = TitleBlockDetector.Detect(entities, null);
+
+            Assert.Empty(result);
+        }
+
+        [Fact]
+        public void DetectTitleBlock_BottomEdgeStrip()
+        {
+            var partLine = new Line(20, 40, 80, 40) { Layer = new Layer("0") };
+
+            var tbLines = new List<Entity>();
+            for (var x = 0; x <= 100; x += 10)
+                tbLines.Add(new Line(x, 0, x, 20) { Layer = new Layer("0") });
+            for (var y = 0; y <= 20; y += 5)
+                tbLines.Add(new Line(0, y, 100, y) { Layer = new Layer("0") });
+
+            var entities = new List<Entity> { partLine };
+            entities.AddRange(tbLines);
+
+            var doc = BuildDocWithTexts(
+                (10, 5, "TITLE"),
+                (30, 5, "DWG NO"),
+                (50, 5, "SCALE"),
+                (70, 5, "REV"),
+                (90, 5, "DATE"));
+
+            var result = TitleBlockDetector.Detect(entities, doc);
+
+            foreach (var tb in tbLines)
+                Assert.Contains(tb.Id, result);
+            Assert.DoesNotContain(partLine.Id, result);
+        }
+
+        private static ACadSharp.CadDocument BuildDocWithTexts(
+            params (double x, double y, string value)[] texts)
+        {
+            var doc = new ACadSharp.CadDocument();
+            foreach (var (x, y, value) in texts)
+            {
+                var mtext = new ACadSharp.Entities.MText
+                {
+                    InsertPoint = new XYZ(x, y, 0),
+                    Value = value,
+                    Height = 2.0
+                };
+                doc.Entities.Add(mtext);
+            }
+            return doc;
+        }
+    }
+}

OpenNest.Tests/Math/FractionTests.cs

@@ -0,0 +1,46 @@
+using OpenNest.Math;
+using Xunit;
+
+namespace OpenNest.Tests.Math;
+
+public class FractionTests
+{
+    [Theory]
+    [InlineData("3/8", 0.375)]
+    [InlineData("1 3/4", 1.75)]
+    [InlineData("1-3/4", 1.75)]
+    [InlineData("1/2", 0.5)]
+    public void Parse_ValidFraction_ReturnsDouble(string input, double expected)
+    {
+        var result = Fraction.Parse(input);
+
+        Assert.Equal(expected, result, 8);
+    }
+
+    [Theory]
+    [InlineData("3/8", true)]
+    [InlineData("abc", false)]
+    [InlineData("1 3/4", true)]
+    public void IsValid_ReturnsExpected(string input, bool expected)
+    {
+        Assert.Equal(expected, Fraction.IsValid(input));
+    }
+
+    [Fact]
+    public void TryParse_InvalidInput_ReturnsFalse()
+    {
+        var result = Fraction.TryParse("abc", out var value);
+
+        Assert.False(result);
+        Assert.Equal(0, value);
+    }
+
+    [Fact]
+    public void ReplaceFractionsWithDecimals_ReplacesFractionInString()
+    {
+        var result = Fraction.ReplaceFractionsWithDecimals("length is 1 3/4 inches");
+
+        Assert.Contains("1.75", result);
+        Assert.DoesNotContain("3/4", result);
+    }
+}

OpenNest.Tests/OpenNest.Tests.csproj

@@ -34,6 +34,9 @@
     <Content Include="Bending\TestData\**\*">
       <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
     </Content>
+    <Content Include="Splitting\TestData\**\*">
+      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
+    </Content>
   </ItemGroup>
 
 </Project>

OpenNest.Tests/PlateSnapToStandardSizeTests.cs

@@ -0,0 +1,118 @@
+using OpenNest.CNC;
+using OpenNest.Geometry;
+using OpenNest.Shapes;
+
+namespace OpenNest.Tests;
+
+public class PlateSnapToStandardSizeTests
+{
+    private static Part MakeRectPart(double x, double y, double length, double width)
+    {
+        var pgm = new Program();
+        pgm.Codes.Add(new RapidMove(new Vector(0, 0)));
+        pgm.Codes.Add(new LinearMove(new Vector(length, 0)));
+        pgm.Codes.Add(new LinearMove(new Vector(length, width)));
+        pgm.Codes.Add(new LinearMove(new Vector(0, width)));
+        pgm.Codes.Add(new LinearMove(new Vector(0, 0)));
+        var drawing = new Drawing("test", pgm);
+        var part = new Part(drawing);
+        part.Offset(x, y);
+        return part;
+    }
+
+    [Fact]
+    public void SnapToStandardSize_SmallParts_SnapsToIncrement()
+    {
+        var plate = new Plate(200, 200); // oversized starting size
+        plate.Parts.Add(MakeRectPart(0, 0, 10, 20));
+
+        var result = plate.SnapToStandardSize();
+
+        // 10x20 is well below 48x48 MinSheet -> snap to integer increment.
+        Assert.Null(result.MatchedLabel);
+        Assert.Equal(10, plate.Size.Length); // X axis
+        Assert.Equal(20, plate.Size.Width);  // Y axis
+    }
+
+    [Fact]
+    public void SnapToStandardSize_SmallPartsWithFractionalIncrement_UsesIncrement()
+    {
+        var plate = new Plate(200, 200);
+        plate.Parts.Add(MakeRectPart(0, 0, 10.3, 20.7));
+
+        var result = plate.SnapToStandardSize(new PlateSizeOptions { SnapIncrement = 0.25 });
+
+        Assert.Null(result.MatchedLabel);
+        Assert.Equal(10.5, plate.Size.Length, 4);
+        Assert.Equal(20.75, plate.Size.Width, 4);
+    }
+
+    [Fact]
+    public void SnapToStandardSize_40x90Part_SnapsToStandard48x96_XLong()
+    {
+        // Part is 90 long (X) x 40 wide (Y) -> X is the long axis.
+        var plate = new Plate(200, 200);
+        plate.Parts.Add(MakeRectPart(0, 0, 90, 40));
+
+        var result = plate.SnapToStandardSize();
+
+        Assert.Equal("48x96", result.MatchedLabel);
+        Assert.Equal(96, plate.Size.Length); // X axis = long
+        Assert.Equal(48, plate.Size.Width);  // Y axis = short
+    }
+
+    [Fact]
+    public void SnapToStandardSize_90TallPart_SnapsToStandard48x96_YLong()
+    {
+        // Part is 40 long (X) x 90 wide (Y) -> Y is the long axis.
+        var plate = new Plate(200, 200);
+        plate.Parts.Add(MakeRectPart(0, 0, 40, 90));
+
+        var result = plate.SnapToStandardSize();
+
+        Assert.Equal("48x96", result.MatchedLabel);
+        Assert.Equal(48, plate.Size.Length); // X axis = short
+        Assert.Equal(96, plate.Size.Width);  // Y axis = long
+    }
+
+    [Fact]
+    public void SnapToStandardSize_JustOver48_PicksNextStandardSize()
+    {
+        var plate = new Plate(200, 200);
+        plate.Parts.Add(MakeRectPart(0, 0, 100, 50));
+
+        var result = plate.SnapToStandardSize();
+
+        Assert.Equal("60x120", result.MatchedLabel);
+        Assert.Equal(120, plate.Size.Length); // X long
+        Assert.Equal(60, plate.Size.Width);
+    }
+
+    [Fact]
+    public void SnapToStandardSize_EmptyPlate_DoesNotModifySize()
+    {
+        var plate = new Plate(60, 120);
+
+        var result = plate.SnapToStandardSize();
+
+        Assert.Null(result.MatchedLabel);
+        Assert.Equal(60, plate.Size.Width);
+        Assert.Equal(120, plate.Size.Length);
+    }
+
+    [Fact]
+    public void SnapToStandardSize_MultipleParts_UsesCombinedEnvelope()
+    {
+        var plate = new Plate(200, 200);
+        plate.Parts.Add(MakeRectPart(0, 0, 30, 40));
+        plate.Parts.Add(MakeRectPart(30, 0, 30, 40));  // combined X-extent = 60
+        plate.Parts.Add(MakeRectPart(0, 40, 60, 60));  // combined extent = 60 x 100
+
+        var result = plate.SnapToStandardSize();
+
+        // 60 x 100 fits 60x120 standard sheet, Y is the long axis.
+        Assert.Equal("60x120", result.MatchedLabel);
+        Assert.Equal(60, plate.Size.Length); // X
+        Assert.Equal(120, plate.Size.Width); // Y long
+    }
+}

OpenNest.Tests/Shapes/FlangeShapeTests.cs

@@ -1,104 +0,0 @@
-using OpenNest.Shapes;
-
-namespace OpenNest.Tests.Shapes;
-
-public class FlangeShapeTests
-{
-    [Fact]
-    public void GetDrawing_BoundingBoxMatchesOD()
-    {
-        var shape = new FlangeShape
-        {
-            OD = 10,
-            HoleDiameter = 1,
-            HolePatternDiameter = 7,
-            HoleCount = 4
-        };
-        var drawing = shape.GetDrawing();
-
-        var bbox = drawing.Program.BoundingBox();
-        Assert.Equal(10, bbox.Width, 0.01);
-        Assert.Equal(10, bbox.Length, 0.01);
-    }
-
-    [Fact]
-    public void GetDrawing_AreaExcludesBoltHoles()
-    {
-        var shape = new FlangeShape
-        {
-            OD = 10,
-            HoleDiameter = 1,
-            HolePatternDiameter = 7,
-            HoleCount = 4
-        };
-        var drawing = shape.GetDrawing();
-
-        // Area = pi * 5^2 - 4 * pi * 0.5^2 = pi * (25 - 1) = pi * 24
-        var expectedArea = System.Math.PI * 24;
-        Assert.Equal(expectedArea, drawing.Area, 0.5);
-    }
-
-    [Fact]
-    public void GetDrawing_DefaultName_IsFlange()
-    {
-        var shape = new FlangeShape
-        {
-            OD = 10,
-            HoleDiameter = 1,
-            HolePatternDiameter = 7,
-            HoleCount = 4
-        };
-        var drawing = shape.GetDrawing();
-
-        Assert.Equal("Flange", drawing.Name);
-    }
-
-    [Fact]
-    public void LoadFromJson_ProducesCorrectDrawing()
-    {
-        var json = """
-        [
-          {
-            "Name": "2in-150#",
-            "NominalPipeSize": 2.0,
-            "OD": 6.0,
-            "HoleDiameter": 0.75,
-            "HolePatternDiameter": 4.75,
-            "HoleCount": 4
-          },
-          {
-            "Name": "2in-300#",
-            "NominalPipeSize": 2.0,
-            "OD": 6.5,
-            "HoleDiameter": 0.75,
-            "HolePatternDiameter": 5.0,
-            "HoleCount": 8
-          }
-        ]
-        """;
-
-        var tempFile = Path.GetTempFileName();
-        try
-        {
-            File.WriteAllText(tempFile, json);
-
-            var flanges = ShapeDefinition.LoadFromJson<FlangeShape>(tempFile);
-
-            Assert.Equal(2, flanges.Count);
-
-            var first = flanges[0];
-            Assert.Equal("2in-150#", first.Name);
-            var drawing = first.GetDrawing();
-            var bbox = drawing.Program.BoundingBox();
-            Assert.Equal(6, bbox.Width, 0.01);
-
-            var second = flanges[1];
-            Assert.Equal("2in-300#", second.Name);
-            Assert.Equal(8, second.HoleCount);
-        }
-        finally
-        {
-            File.Delete(tempFile);
-        }
-    }
-}

OpenNest.Tests/Shapes/NgonShapeTests.cs

@@ -0,0 +1,51 @@
+using OpenNest.Shapes;
+
+namespace OpenNest.Tests.Shapes;
+
+public class NgonShapeTests
+{
+    [Fact]
+    public void GetDrawing_Octagon_BoundingBoxFitsWithinExpectedSize()
+    {
+        var shape = new NgonShape { Sides = 8, Width = 20 };
+        var drawing = shape.GetDrawing();
+
+        var bbox = drawing.Program.BoundingBox();
+        // Corner-to-corner is larger than flat-to-flat
+        Assert.True(bbox.Width >= 20 - 0.01);
+        Assert.True(bbox.Length >= 20 - 0.01);
+        // But should not be wildly larger (corner-to-corner ~ width / cos(22.5deg) ~ width * 1.0824)
+        Assert.True(bbox.Width < 22);
+        Assert.True(bbox.Length < 22);
+    }
+
+    [Theory]
+    [InlineData(3)]
+    [InlineData(4)]
+    [InlineData(5)]
+    [InlineData(6)]
+    [InlineData(8)]
+    [InlineData(12)]
+    public void GetDrawing_HasOneLinearMovePerSide(int sides)
+    {
+        var shape = new NgonShape { Sides = sides, Width = 20 };
+        var drawing = shape.GetDrawing();
+
+        var moves = drawing.Program.Codes
+            .OfType<OpenNest.CNC.LinearMove>()
+            .Count();
+        Assert.Equal(sides, moves);
+    }
+
+    [Fact]
+    public void GetDrawing_ClampsSidesBelowThreeToTriangle()
+    {
+        var shape = new NgonShape { Sides = 2, Width = 20 };
+        var drawing = shape.GetDrawing();
+
+        var moves = drawing.Program.Codes
+            .OfType<OpenNest.CNC.LinearMove>()
+            .Count();
+        Assert.Equal(3, moves);
+    }
+}

OpenNest.Tests/Shapes/OctagonShapeTests.cs

@@ -1,34 +0,0 @@
-using OpenNest.Shapes;
-
-namespace OpenNest.Tests.Shapes;
-
-public class OctagonShapeTests
-{
-    [Fact]
-    public void GetDrawing_BoundingBoxFitsWithinExpectedSize()
-    {
-        var shape = new OctagonShape { Width = 20 };
-        var drawing = shape.GetDrawing();
-
-        var bbox = drawing.Program.BoundingBox();
-        // Corner-to-corner is larger than flat-to-flat
-        Assert.True(bbox.Width >= 20 - 0.01);
-        Assert.True(bbox.Length >= 20 - 0.01);
-        // But should not be wildly larger (corner-to-corner ~ width / cos(22.5deg) ~ width * 1.0824)
-        Assert.True(bbox.Width < 22);
-        Assert.True(bbox.Length < 22);
-    }
-
-    [Fact]
-    public void GetDrawing_HasEightEdges()
-    {
-        var shape = new OctagonShape { Width = 20 };
-        var drawing = shape.GetDrawing();
-
-        // An octagon program should have 8 linear moves (one per edge)
-        var moves = drawing.Program.Codes
-            .OfType<OpenNest.CNC.LinearMove>()
-            .Count();
-        Assert.Equal(8, moves);
-    }
-}

OpenNest.Tests/Shapes/PipeFlangeShapeTests.cs

@@ -0,0 +1,216 @@
+using System;
+using System.IO;
+using OpenNest.Shapes;
+
+namespace OpenNest.Tests.Shapes;
+
+public class PipeFlangeShapeTests
+{
+    [Fact]
+    public void GetDrawing_BoundingBoxMatchesOD()
+    {
+        var shape = new PipeFlangeShape
+        {
+            OD = 10,
+            HoleDiameter = 1,
+            HolePatternDiameter = 7,
+            HoleCount = 4
+        };
+        var drawing = shape.GetDrawing();
+
+        var bbox = drawing.Program.BoundingBox();
+        Assert.Equal(10, bbox.Width, 0.01);
+        Assert.Equal(10, bbox.Length, 0.01);
+    }
+
+    [Fact]
+    public void GetDrawing_AreaExcludesBoltHoles()
+    {
+        var shape = new PipeFlangeShape
+        {
+            OD = 10,
+            HoleDiameter = 1,
+            HolePatternDiameter = 7,
+            HoleCount = 4,
+            Blind = true
+        };
+        var drawing = shape.GetDrawing();
+
+        var expectedArea = System.Math.PI * 24;
+        Assert.Equal(expectedArea, drawing.Area, 0.5);
+    }
+
+    [Fact]
+    public void GetDrawing_DefaultName_IsPipeFlange()
+    {
+        var shape = new PipeFlangeShape
+        {
+            OD = 10,
+            HoleDiameter = 1,
+            HolePatternDiameter = 7,
+            HoleCount = 4
+        };
+        var drawing = shape.GetDrawing();
+
+        Assert.Equal("PipeFlange", drawing.Name);
+    }
+
+    [Fact]
+    public void GetDrawing_WithPipeSize_CutsCenterBoreAtPipeODPlusClearance()
+    {
+        var shape = new PipeFlangeShape
+        {
+            OD = 10,
+            HoleDiameter = 1,
+            HolePatternDiameter = 7,
+            HoleCount = 4,
+            PipeSize = "2",       // OD = 2.375
+            PipeClearance = 0.125,
+            Blind = false
+        };
+        var drawing = shape.GetDrawing();
+
+        // Expected bore diameter = 2.375 + 0.125 = 2.5
+        // Area = pi * (5^2 - 0.5^2 * 4 - 1.25^2) = pi * (25 - 1 - 1.5625) = pi * 22.4375
+        var expectedArea = System.Math.PI * 22.4375;
+        Assert.Equal(expectedArea, drawing.Area, 0.5);
+    }
+
+    [Fact]
+    public void GetDrawing_Blind_OmitsCenterBore()
+    {
+        var shape = new PipeFlangeShape
+        {
+            OD = 10,
+            HoleDiameter = 1,
+            HolePatternDiameter = 7,
+            HoleCount = 4,
+            PipeSize = "2",
+            PipeClearance = 0.125,
+            Blind = true
+        };
+        var drawing = shape.GetDrawing();
+
+        // With Blind=true, area = outer - 4 bolt holes = pi * (25 - 1) = pi * 24
+        var expectedArea = System.Math.PI * 24;
+        Assert.Equal(expectedArea, drawing.Area, 0.5);
+    }
+
+    [Fact]
+    public void GetDrawing_UnknownPipeSize_OmitsCenterBore()
+    {
+        var shape = new PipeFlangeShape
+        {
+            OD = 10,
+            HoleDiameter = 1,
+            HolePatternDiameter = 7,
+            HoleCount = 4,
+            PipeSize = "not-a-real-pipe",
+            PipeClearance = 0.125,
+            Blind = false
+        };
+        var drawing = shape.GetDrawing();
+
+        // Unknown pipe size → no bore, area matches blind case
+        var expectedArea = System.Math.PI * 24;
+        Assert.Equal(expectedArea, drawing.Area, 0.5);
+    }
+
+    [Theory]
+    [InlineData(null)]
+    [InlineData("")]
+    public void GetDrawing_NullOrEmptyPipeSize_OmitsCenterBore(string pipeSize)
+    {
+        var shape = new PipeFlangeShape
+        {
+            OD = 10,
+            HoleDiameter = 1,
+            HolePatternDiameter = 7,
+            HoleCount = 4,
+            PipeSize = pipeSize,
+            PipeClearance = 0.125
+        };
+        var drawing = shape.GetDrawing();
+
+        var expectedArea = System.Math.PI * 24;
+        Assert.Equal(expectedArea, drawing.Area, 0.5);
+    }
+
+    [Fact]
+    public void LoadFromJson_ProducesCorrectDrawing()
+    {
+        var json = """
+        [
+          {
+            "Name": "2in-150#",
+            "PipeSize": "2",
+            "PipeClearance": 0.0625,
+            "OD": 6.0,
+            "HoleDiameter": 0.75,
+            "HolePatternDiameter": 4.75,
+            "HoleCount": 4
+          },
+          {
+            "Name": "2in-300#",
+            "PipeSize": "2",
+            "PipeClearance": 0.0625,
+            "OD": 6.5,
+            "HoleDiameter": 0.75,
+            "HolePatternDiameter": 5.0,
+            "HoleCount": 8
+          }
+        ]
+        """;
+
+        var tempFile = Path.GetTempFileName();
+        try
+        {
+            File.WriteAllText(tempFile, json);
+
+            var flanges = ShapeDefinition.LoadFromJson<PipeFlangeShape>(tempFile);
+
+            Assert.Equal(2, flanges.Count);
+
+            var first = flanges[0];
+            Assert.Equal("2in-150#", first.Name);
+            Assert.Equal("2", first.PipeSize);
+            Assert.Equal(0.0625, first.PipeClearance, 0.0001);
+            var drawing = first.GetDrawing();
+            var bbox = drawing.Program.BoundingBox();
+            Assert.Equal(6, bbox.Width, 0.01);
+
+            var second = flanges[1];
+            Assert.Equal("2in-300#", second.Name);
+            Assert.Equal(8, second.HoleCount);
+        }
+        finally
+        {
+            File.Delete(tempFile);
+        }
+    }
+
+    [Fact]
+    public void LoadFromJson_RealShippedConfig_LoadsAllEntries()
+    {
+        // Resolve the repo-relative config path from the test binary location.
+        var dir = AppDomain.CurrentDomain.BaseDirectory;
+        while (dir != null && !File.Exists(Path.Combine(dir, "OpenNest.sln")))
+            dir = Path.GetDirectoryName(dir);
+
+        Assert.NotNull(dir);
+
+        var configPath = Path.Combine(dir, "OpenNest", "Configurations", "PipeFlangeShape.json");
+        Assert.True(File.Exists(configPath), $"Config missing at {configPath}");
+
+        var flanges = ShapeDefinition.LoadFromJson<PipeFlangeShape>(configPath);
+
+        Assert.NotEmpty(flanges);
+        foreach (var f in flanges)
+        {
+            Assert.False(string.IsNullOrWhiteSpace(f.PipeSize));
+            Assert.True(PipeSizes.TryGetOD(f.PipeSize, out _),
+                $"Unknown PipeSize '{f.PipeSize}' in entry '{f.Name}'");
+            Assert.Equal(0.0625, f.PipeClearance, 0.0001);
+        }
+    }
+}

OpenNest.Tests/Shapes/PipeSizesTests.cs

@@ -0,0 +1,64 @@
+using OpenNest.Shapes;
+
+namespace OpenNest.Tests.Shapes;
+
+public class PipeSizesTests
+{
+    [Fact]
+    public void All_ContainsExpectedCount()
+    {
+        Assert.Equal(35, PipeSizes.All.Count);
+    }
+
+    [Fact]
+    public void All_IsSortedByOuterDiameterAscending()
+    {
+        for (var i = 1; i < PipeSizes.All.Count; i++)
+            Assert.True(PipeSizes.All[i].OuterDiameter > PipeSizes.All[i - 1].OuterDiameter);
+    }
+
+    [Theory]
+    [InlineData("1/8", 0.405)]
+    [InlineData("1/2", 0.840)]
+    [InlineData("2", 2.375)]
+    [InlineData("2 1/2", 2.875)]
+    [InlineData("12", 12.750)]
+    [InlineData("48", 48.000)]
+    public void TryGetOD_KnownLabel_ReturnsExpectedOD(string label, double expected)
+    {
+        Assert.True(PipeSizes.TryGetOD(label, out var od));
+        Assert.Equal(expected, od, 0.001);
+    }
+
+    [Fact]
+    public void TryGetOD_UnknownLabel_ReturnsFalse()
+    {
+        Assert.False(PipeSizes.TryGetOD("bogus", out _));
+    }
+
+    [Fact]
+    public void GetFittingSizes_FiltersByMaxOD()
+    {
+        var results = PipeSizes.GetFittingSizes(3.0).ToList();
+
+        Assert.Contains(results, e => e.Label == "2 1/2");
+        Assert.DoesNotContain(results, e => e.Label == "3");
+        Assert.DoesNotContain(results, e => e.Label == "4");
+    }
+
+    [Fact]
+    public void GetFittingSizes_ExactBoundary_IsInclusive()
+    {
+        // NPS 3 has OD 3.500; passing maxOD = 3.500 should include it.
+        var results = PipeSizes.GetFittingSizes(3.500).ToList();
+
+        Assert.Contains(results, e => e.Label == "3");
+        Assert.DoesNotContain(results, e => e.Label == "3 1/2");
+    }
+
+    [Fact]
+    public void GetFittingSizes_MaxSmallerThanSmallest_ReturnsEmpty()
+    {
+        Assert.Empty(PipeSizes.GetFittingSizes(0.1));
+    }
+}

OpenNest.Tests/Shapes/PlateSizesTests.cs

@@ -0,0 +1,311 @@
+using System.Collections.Generic;
+using System.Linq;
+using OpenNest.Geometry;
+using OpenNest.Shapes;
+
+namespace OpenNest.Tests.Shapes;
+
+public class PlateSizesTests
+{
+    [Fact]
+    public void All_IsNotEmpty()
+    {
+        Assert.NotEmpty(PlateSizes.All);
+    }
+
+    [Fact]
+    public void All_DoesNotContain48x48()
+    {
+        // 48x48 is not a standard sheet - it's the default MinSheet threshold only.
+        Assert.DoesNotContain(PlateSizes.All, e => e.Width == 48 && e.Length == 48);
+    }
+
+    [Fact]
+    public void All_Smallest_Is48x96()
+    {
+        var smallest = PlateSizes.All.OrderBy(e => e.Area).First();
+        Assert.Equal(48, smallest.Width);
+        Assert.Equal(96, smallest.Length);
+    }
+
+    [Fact]
+    public void All_SortedByAreaAscending()
+    {
+        for (var i = 1; i < PlateSizes.All.Count; i++)
+            Assert.True(PlateSizes.All[i].Area >= PlateSizes.All[i - 1].Area);
+    }
+
+    [Fact]
+    public void All_Entries_AreCanonical_WidthLessOrEqualLength()
+    {
+        foreach (var entry in PlateSizes.All)
+            Assert.True(entry.Width <= entry.Length, $"{entry.Label} not in canonical orientation");
+    }
+
+    [Theory]
+    [InlineData(40, 40, true)]    // small - fits trivially
+    [InlineData(48, 96, true)]    // exact
+    [InlineData(96, 48, true)]    // rotated exact
+    [InlineData(90, 40, true)]    // rotated
+    [InlineData(49, 97, false)]   // just over in both dims
+    [InlineData(50, 50, false)]   // too wide in both orientations
+    public void Entry_Fits_RespectsRotation(double w, double h, bool expected)
+    {
+        var entry = new PlateSizes.Entry("48x96", 48, 96);
+        Assert.Equal(expected, entry.Fits(w, h));
+    }
+
+    [Fact]
+    public void TryGet_KnownLabel_ReturnsEntry()
+    {
+        Assert.True(PlateSizes.TryGet("48x96", out var entry));
+        Assert.Equal(48, entry.Width);
+        Assert.Equal(96, entry.Length);
+    }
+
+    [Fact]
+    public void TryGet_IsCaseInsensitive()
+    {
+        Assert.True(PlateSizes.TryGet("48X96", out var entry));
+        Assert.Equal(48, entry.Width);
+        Assert.Equal(96, entry.Length);
+    }
+
+    [Fact]
+    public void TryGet_UnknownLabel_ReturnsFalse()
+    {
+        Assert.False(PlateSizes.TryGet("bogus", out _));
+    }
+
+    [Fact]
+    public void Recommend_BelowMin_SnapsToDefaultIncrementOfOne()
+    {
+        var bbox = new Box(0, 0, 10.3, 20.7);
+
+        var result = PlateSizes.Recommend(bbox);
+
+        Assert.Equal(11, result.Width);
+        Assert.Equal(21, result.Length);
+        Assert.Null(result.MatchedLabel);
+    }
+
+    [Fact]
+    public void Recommend_BelowMin_UsesCustomIncrement()
+    {
+        var bbox = new Box(0, 0, 10.3, 20.7);
+        var options = new PlateSizeOptions { SnapIncrement = 0.25 };
+
+        var result = PlateSizes.Recommend(bbox, options);
+
+        Assert.Equal(10.5, result.Width, 4);
+        Assert.Equal(20.75, result.Length, 4);
+        Assert.Null(result.MatchedLabel);
+    }
+
+    [Fact]
+    public void Recommend_ExactlyAtMin_Snaps()
+    {
+        var bbox = new Box(0, 0, 48, 48);
+
+        var result = PlateSizes.Recommend(bbox);
+
+        Assert.Equal(48, result.Width);
+        Assert.Equal(48, result.Length);
+        Assert.Null(result.MatchedLabel);
+    }
+
+    [Fact]
+    public void Recommend_AboveMin_PicksSmallestContainingStandardSheet()
+    {
+        var bbox = new Box(0, 0, 40, 90);
+
+        var result = PlateSizes.Recommend(bbox);
+
+        Assert.Equal(48, result.Width);
+        Assert.Equal(96, result.Length);
+        Assert.Equal("48x96", result.MatchedLabel);
+    }
+
+    [Fact]
+    public void Recommend_AboveMin_WithRotation_PicksSmallestSheet()
+    {
+        var bbox = new Box(0, 0, 90, 40);
+
+        var result = PlateSizes.Recommend(bbox);
+
+        Assert.Equal("48x96", result.MatchedLabel);
+    }
+
+    [Fact]
+    public void Recommend_JustOver48_PicksNextStandardSize()
+    {
+        var bbox = new Box(0, 0, 50, 100);
+
+        var result = PlateSizes.Recommend(bbox);
+
+        Assert.Equal(60, result.Width);
+        Assert.Equal(120, result.Length);
+        Assert.Equal("60x120", result.MatchedLabel);
+    }
+
+    [Fact]
+    public void Recommend_MarginIsAppliedPerSide()
+    {
+        // 46 + 2*1 = 48 (fits exactly), 94 + 2*1 = 96 (fits exactly)
+        var bbox = new Box(0, 0, 46, 94);
+        var options = new PlateSizeOptions { Margin = 1 };
+
+        var result = PlateSizes.Recommend(bbox, options);
+
+        Assert.Equal("48x96", result.MatchedLabel);
+    }
+
+    [Fact]
+    public void Recommend_MarginPushesToNextSheet()
+    {
+        // 47 + 2 = 49 > 48, so 48x96 no longer fits -> next standard
+        var bbox = new Box(0, 0, 47, 95);
+        var options = new PlateSizeOptions { Margin = 1 };
+
+        var result = PlateSizes.Recommend(bbox, options);
+
+        Assert.NotEqual("48x96", result.MatchedLabel);
+        Assert.True(result.Width >= 49);
+        Assert.True(result.Length >= 97);
+    }
+
+    [Fact]
+    public void Recommend_AllowedSizes_StandardLabelWhitelist()
+    {
+        // 60x120 is the only option; 50x50 is above min so it routes to standard
+        var bbox = new Box(0, 0, 50, 50);
+        var options = new PlateSizeOptions { AllowedSizes = new[] { "60x120" } };
+
+        var result = PlateSizes.Recommend(bbox, options);
+
+        Assert.Equal("60x120", result.MatchedLabel);
+    }
+
+    [Fact]
+    public void Recommend_AllowedSizes_ArbitraryWxHString()
+    {
+        // 50x100 isn't in the standard catalog but is valid as an ad-hoc entry.
+        // bbox 49x99 doesn't fit 48x96 or 48x120, does fit 50x100 and 60x120,
+        // but only 50x100 is allowed.
+        var bbox = new Box(0, 0, 49, 99);
+        var options = new PlateSizeOptions { AllowedSizes = new[] { "50x100" } };
+
+        var result = PlateSizes.Recommend(bbox, options);
+
+        Assert.Equal(50, result.Width);
+        Assert.Equal(100, result.Length);
+        Assert.Equal("50x100", result.MatchedLabel);
+    }
+
+    [Fact]
+    public void Recommend_NothingFits_FallsBackToSnapUp()
+    {
+        // Larger than any catalog sheet
+        var bbox = new Box(0, 0, 100, 300);
+
+        var result = PlateSizes.Recommend(bbox);
+
+        Assert.Equal(100, result.Width);
+        Assert.Equal(300, result.Length);
+        Assert.Null(result.MatchedLabel);
+    }
+
+    [Fact]
+    public void Recommend_NothingFitsInAllowedList_FallsBackToSnapUp()
+    {
+        // Only 48x96 allowed, but bbox is too big for it
+        var bbox = new Box(0, 0, 50, 100);
+        var options = new PlateSizeOptions { AllowedSizes = new[] { "48x96" } };
+
+        var result = PlateSizes.Recommend(bbox, options);
+
+        Assert.Equal(50, result.Width);
+        Assert.Equal(100, result.Length);
+        Assert.Null(result.MatchedLabel);
+    }
+
+    [Fact]
+    public void Recommend_BoxEnumerable_CombinesIntoEnvelope()
+    {
+        // Two boxes that together span 0..40 x 0..90 -> fits 48x96
+        var boxes = new[]
+        {
+            new Box(0, 0, 40, 50),
+            new Box(0, 40, 30, 50),
+        };
+
+        var result = PlateSizes.Recommend(boxes);
+
+        Assert.Equal("48x96", result.MatchedLabel);
+    }
+
+    [Fact]
+    public void Recommend_BoxEnumerable_Empty_Throws()
+    {
+        Assert.Throws<System.ArgumentException>(
+            () => PlateSizes.Recommend(System.Array.Empty<Box>()));
+    }
+
+    [Fact]
+    public void PlateSizeOptions_Defaults()
+    {
+        var options = new PlateSizeOptions();
+
+        Assert.Equal(48, options.MinSheetWidth);
+        Assert.Equal(48, options.MinSheetLength);
+        Assert.Equal(1.0, options.SnapIncrement);
+        Assert.Equal(0, options.Margin);
+        Assert.Null(options.AllowedSizes);
+        Assert.Equal(PlateSizeSelection.SmallestArea, options.Selection);
+    }
+
+    [Fact]
+    public void Recommend_NarrowestFirst_PicksNarrowerSheetOverSmallerArea()
+    {
+        // Hypothetical: bbox (47, 47) fits both 48x96 (area 4608) and some narrower option.
+        // With SmallestArea: picks 48x96 (it's already the smallest 48-wide).
+        // With NarrowestFirst: also picks 48x96 since that's the narrowest.
+        // Better test: AllowedSizes = ["60x120", "48x120"] with bbox that fits both.
+        // 48x120 (area 5760) is narrower; 60x120 (area 7200) has more area.
+        // SmallestArea picks 48x120; NarrowestFirst also picks 48x120. Both pick the same.
+        //
+        // Real divergence: AllowedSizes = ["60x120", "72x120"] with bbox 55x100.
+        // 60x120 has narrower width (60) AND smaller area (7200 vs 8640), so both agree.
+        //
+        // To force divergence: AllowedSizes = ["60x96", "48x144"] with bbox 47x95.
+        // 60x96 area = 5760, 48x144 area = 6912. SmallestArea -> 60x96.
+        // NarrowestFirst width 48 < 60 -> 48x144.
+        var bbox = new Box(0, 0, 47, 95);
+        var options = new PlateSizeOptions
+        {
+            AllowedSizes = new[] { "60x96", "48x144" },
+            Selection = PlateSizeSelection.NarrowestFirst,
+        };
+
+        var result = PlateSizes.Recommend(bbox, options);
+
+        Assert.Equal(48, result.Width);
+        Assert.Equal(144, result.Length);
+    }
+
+    [Fact]
+    public void Recommend_SmallestArea_PicksSmallerAreaOverNarrowerWidth()
+    {
+        var bbox = new Box(0, 0, 47, 95);
+        var options = new PlateSizeOptions
+        {
+            AllowedSizes = new[] { "60x96", "48x144" },
+            Selection = PlateSizeSelection.SmallestArea,
+        };
+
+        var result = PlateSizes.Recommend(bbox, options);
+
+        Assert.Equal(60, result.Width);
+        Assert.Equal(96, result.Length);
+    }
+}

OpenNest.Tests/Splitting/DrawingSplitterTests.cs

@@ -384,6 +384,161 @@ public class DrawingSplitterTests
         }
     }
 
+    [Fact]
+    public void Split_RectangleWithSpanningSlot_ProducesDisconnectedStrips()
+    {
+        // 255x55 outer rectangle with a 235x35 interior slot centered at (10,10)-(245,45).
+        // 4 vertical splits at x = 55, 110, 165, 220.
+        //
+        // Expected: regions R2/R3/R4 are entirely "over" the slot horizontally, so the
+        // surviving material in each is two physically disjoint strips (upper + lower).
+        // R1 and R5 each have a solid edge that connects the top and bottom strips, so
+        // they remain single (notched) pieces.
+        //
+        // Total output drawings: 1 (R1) + 2 (R2) + 2 (R3) + 2 (R4) + 1 (R5) = 8.
+        var outerEntities = new List<Entity>
+        {
+            new Line(new Vector(0, 0), new Vector(255, 0)),
+            new Line(new Vector(255, 0), new Vector(255, 55)),
+            new Line(new Vector(255, 55), new Vector(0, 55)),
+            new Line(new Vector(0, 55), new Vector(0, 0))
+        };
+        var slotEntities = new List<Entity>
+        {
+            new Line(new Vector(10, 10), new Vector(245, 10)),
+            new Line(new Vector(245, 10), new Vector(245, 45)),
+            new Line(new Vector(245, 45), new Vector(10, 45)),
+            new Line(new Vector(10, 45), new Vector(10, 10))
+        };
+        var allEntities = new List<Entity>();
+        allEntities.AddRange(outerEntities);
+        allEntities.AddRange(slotEntities);
+
+        var drawing = new Drawing("SLOT", ConvertGeometry.ToProgram(allEntities));
+        var originalArea = drawing.Area;
+
+        var splitLines = new List<SplitLine>
+        {
+            new SplitLine(55.0, CutOffAxis.Vertical),
+            new SplitLine(110.0, CutOffAxis.Vertical),
+            new SplitLine(165.0, CutOffAxis.Vertical),
+            new SplitLine(220.0, CutOffAxis.Vertical)
+        };
+
+        var results = DrawingSplitter.Split(drawing, splitLines, new SplitParameters { Type = SplitType.Straight });
+
+        // R1 (0..55)   → 1 notched piece,  height 55
+        // R2 (55..110) → upper strip + lower strip, each height 10
+        // R3 (110..165)→ upper strip + lower strip, each height 10
+        // R4 (165..220)→ upper strip + lower strip, each height 10
+        // R5 (220..255)→ 1 notched piece,  height 55
+        Assert.Equal(8, results.Count);
+
+        // Area preservation: sum of all output areas equals (outer − slot).
+        var totalArea = results.Sum(d => d.Area);
+        Assert.Equal(originalArea, totalArea, 1);
+
+        // Box.Length = X-extent, Box.Width = Y-extent.
+        // Exactly 6 strips (Y-extent ~10mm) from the three middle regions, and
+        // exactly 2 notched pieces (Y-extent 55mm) from R1 and R5.
+        var strips = results
+            .Where(d => System.Math.Abs(d.Program.BoundingBox().Width - 10.0) < 0.5)
+            .ToList();
+        var notched = results
+            .Where(d => System.Math.Abs(d.Program.BoundingBox().Width - 55.0) < 0.5)
+            .ToList();
+
+        Assert.Equal(6, strips.Count);
+        Assert.Equal(2, notched.Count);
+
+        // Each piece should form a closed perimeter (no dangling edges, no gaps).
+        foreach (var piece in results)
+        {
+            var entities = ConvertProgram.ToGeometry(piece.Program)
+                .Where(e => e.Layer != SpecialLayers.Rapid).ToList();
+
+            Assert.True(entities.Count >= 3, $"{piece.Name} must have at least 3 edges");
+
+            for (var i = 0; i < entities.Count; i++)
+            {
+                var end = GetEndPoint(entities[i]);
+                var nextStart = GetStartPoint(entities[(i + 1) % entities.Count]);
+                var gap = end.DistanceTo(nextStart);
+                Assert.True(gap < 0.01,
+                    $"{piece.Name} gap of {gap:F4} between edge {i} end and edge {(i + 1) % entities.Count} start");
+            }
+        }
+    }
+
+    [Fact]
+    public void Split_DxfFile_WithSpanningSlot_HasNoCutLinesThroughCutout()
+    {
+        // Real DXF regression: 255x55 plate with a centered slot cutout, split into
+        // five columns. Exercises the same path as the synthetic
+        // Split_RectangleWithSpanningSlot_ProducesDisconnectedStrips test but through
+        // the full DXF import pipeline.
+        var path = Path.Combine(AppContext.BaseDirectory, "Splitting", "TestData", "split_test.dxf");
+        Assert.True(File.Exists(path), $"Test DXF not found: {path}");
+
+        var imported = OpenNest.IO.Dxf.Import(path);
+        var profile = new OpenNest.Geometry.ShapeProfile(imported.Entities);
+
+        // Normalize to origin so the split line positions are predictable.
+        var bb = profile.Perimeter.BoundingBox;
+        var offsetX = -bb.X;
+        var offsetY = -bb.Y;
+        foreach (var e in profile.Perimeter.Entities) e.Offset(offsetX, offsetY);
+        foreach (var cutout in profile.Cutouts)
+            foreach (var e in cutout.Entities) e.Offset(offsetX, offsetY);
+
+        var allEntities = new List<Entity>();
+        allEntities.AddRange(profile.Perimeter.Entities);
+        foreach (var cutout in profile.Cutouts) allEntities.AddRange(cutout.Entities);
+
+        var drawing = new Drawing("SPLITTEST", ConvertGeometry.ToProgram(allEntities));
+        var originalArea = drawing.Area;
+
+        // Part is ~255x55 with an interior slot. Split into 5 columns (55mm each).
+        var splitLines = new List<SplitLine>
+        {
+            new SplitLine(55.0, CutOffAxis.Vertical),
+            new SplitLine(110.0, CutOffAxis.Vertical),
+            new SplitLine(165.0, CutOffAxis.Vertical),
+            new SplitLine(220.0, CutOffAxis.Vertical)
+        };
+
+        var results = DrawingSplitter.Split(drawing, splitLines, new SplitParameters { Type = SplitType.Straight });
+
+        // Area must be preserved within tolerance (floating-point coords in the DXF).
+        var totalArea = results.Sum(d => d.Area);
+        Assert.Equal(originalArea, totalArea, 0);
+
+        // At least one region must yield more than one physical strip — that's the
+        // whole point of the fix: a cutout that spans a region disconnects it.
+        Assert.True(results.Count > splitLines.Count + 1,
+            $"Expected more than {splitLines.Count + 1} pieces (some regions split into strips), got {results.Count}");
+
+        // Every output drawing must resolve into fully-closed shapes (outer loop
+        // and any hole loops), with no dangling geometry. A piece that contains
+        // a cutout will have its entities span more than one connected loop.
+        foreach (var piece in results)
+        {
+            var entities = ConvertProgram.ToGeometry(piece.Program)
+                .Where(e => e.Layer != SpecialLayers.Rapid).ToList();
+
+            Assert.True(entities.Count >= 3, $"{piece.Name} has only {entities.Count} entities");
+
+            var shapes = OpenNest.Geometry.ShapeBuilder.GetShapes(entities);
+            Assert.NotEmpty(shapes);
+
+            foreach (var shape in shapes)
+            {
+                Assert.True(shape.IsClosed(),
+                    $"{piece.Name} contains an open chain of {shape.Entities.Count} entities");
+            }
+        }
+    }
+
     private static Vector GetStartPoint(Entity entity)
     {
         return entity switch

OpenNest.Training/Program.cs

@@ -89,8 +89,10 @@ int RunDataCollection(string dir, string dbPath, string saveDir, double s, strin
         new Size(48, 24), new Size(120, 10)
     };
 
-    var dxfFiles = Directory.GetFiles(dir, "*.dxf", SearchOption.AllDirectories);
+    var dxfFiles = Directory.GetFiles(dir, "*.dxf", SearchOption.AllDirectories)
-    Console.WriteLine($"Found {dxfFiles.Length} DXF files");
+        .Concat(Directory.GetFiles(dir, "*.dwg", SearchOption.AllDirectories))
+        .ToArray();
+    Console.WriteLine($"Found {dxfFiles.Length} CAD files");
     var resolvedDb = dbPath.EndsWith(".db", StringComparison.OrdinalIgnoreCase) ? dbPath : dbPath + ".db";
     Console.WriteLine($"Database: {Path.GetFullPath(resolvedDb)}");
     Console.WriteLine($"Sheet sizes: {sheetSuite.Length} configurations");

OpenNest/Actions/ActionCutOff.cs

@@ -16,15 +16,11 @@ namespace OpenNest.Actions
         private CutOffSettings settings;
         private CutOffAxis lockedAxis = CutOffAxis.Vertical;
         private Dictionary<Part, Entity> perimeterCache;
-        private readonly Timer debounceTimer;
-        private bool regeneratePending;
 
         public ActionCutOff(PlateView plateView)
             : base(plateView)
         {
             settings = plateView.CutOffSettings;
-            debounceTimer = new Timer { Interval = 16 };
-            debounceTimer.Tick += OnDebounce;
             ConnectEvents();
         }
 
@@ -40,8 +36,6 @@ namespace OpenNest.Actions
 
         public override void DisconnectEvents()
         {
-            debounceTimer.Stop();
-            debounceTimer.Dispose();
             plateView.MouseMove -= OnMouseMove;
             plateView.MouseDown -= OnMouseDown;
             plateView.KeyDown -= OnKeyDown;
@@ -58,18 +52,6 @@ namespace OpenNest.Actions
 
         private void OnMouseMove(object sender, MouseEventArgs e)
         {
-            regeneratePending = true;
-            debounceTimer.Start();
-        }
-
-        private void OnDebounce(object sender, System.EventArgs e)
-        {
-            debounceTimer.Stop();
-
-            if (!regeneratePending)
-                return;
-
-            regeneratePending = false;
             var pt = plateView.CurrentPoint;
             previewCutOff = new CutOff(pt, lockedAxis);
             previewCutOff.Regenerate(plateView.Plate, settings, perimeterCache);

OpenNest/ArchUnits.cs

@@ -1,4 +1,4 @@
-using OpenNest.IO.Bom;
+using OpenNest.Math;
 using System;
 using System.Drawing;
 using System.Text;

OpenNest/ColorScheme.cs

@@ -13,10 +13,13 @@ namespace OpenNest
         private Color edgeSpacingColor;
         private Color previewPartColor;
 
-        public static Color[] PartColors => Drawing.PartColors;
+        public string Name { get; set; } = "Unnamed";
+
+        public Color[] PartColors { get; set; } = Drawing.PartColors;
 
         public static readonly ColorScheme Default = new ColorScheme
         {
+            Name = "Classic",
             BackgroundColor = Color.DarkGray,
             LayoutOutlineColor = Color.Gray,
             LayoutFillColor = Color.WhiteSmoke,

OpenNest/ColorSchemeRegistry.cs

@@ -0,0 +1,203 @@
+using OpenNest.Forms;
+using OpenNest.Properties;
+using System;
+using System.Collections.Generic;
+using System.Drawing;
+using System.IO;
+using System.Linq;
+using System.Windows.Forms;
+
+namespace OpenNest
+{
+    public static class ColorSchemeRegistry
+    {
+        private static readonly Dictionary<string, ColorScheme> builtIns =
+            new(StringComparer.OrdinalIgnoreCase)
+            {
+                ["Classic"] = BuildClassic(),
+                ["Pastel"] = BuildPastel(),
+                ["Dark"] = BuildDark()
+            };
+
+        private static List<ColorScheme> diskCache;
+
+        public static IEnumerable<ColorScheme> AllSchemes
+        {
+            get
+            {
+                diskCache ??= LoadDiskSchemes().ToList();
+                return builtIns.Values.Concat(diskCache);
+            }
+        }
+
+        public static void Refresh() => diskCache = null;
+
+        public static ColorScheme Get(string name)
+        {
+            if (string.IsNullOrWhiteSpace(name))
+                return builtIns["Classic"];
+
+            var hit = AllSchemes.FirstOrDefault(
+                s => string.Equals(s.Name, name, StringComparison.OrdinalIgnoreCase));
+            return hit ?? builtIns["Classic"];
+        }
+
+        public static void ApplyActiveFromSettings()
+        {
+            var name = Settings.Default.ActiveColorScheme;
+            var scheme = Get(name);
+            Apply(scheme);
+        }
+
+        public static void Apply(ColorScheme scheme)
+        {
+            var d = ColorScheme.Default;
+            d.Name = scheme.Name;
+            d.BackgroundColor = scheme.BackgroundColor;
+            d.LayoutOutlineColor = scheme.LayoutOutlineColor;
+            d.LayoutFillColor = scheme.LayoutFillColor;
+            d.BoundingBoxColor = scheme.BoundingBoxColor;
+            d.RapidColor = scheme.RapidColor;
+            d.OriginColor = scheme.OriginColor;
+            d.EdgeSpacingColor = scheme.EdgeSpacingColor;
+            d.PreviewPartColor = scheme.PreviewPartColor;
+            d.PartColors = scheme.PartColors;
+
+            Drawing.PartColors = scheme.PartColors;
+
+            RecolorOpenNests(scheme.PartColors);
+        }
+
+        private static void RecolorOpenNests(Color[] palette)
+        {
+            foreach (Form f in Application.OpenForms)
+            {
+                if (f is not EditNestForm enf)
+                    continue;
+
+                var i = 0;
+                foreach (var drawing in enf.Nest.Drawings)
+                {
+                    if (drawing.IsCutOff)
+                        continue;
+                    drawing.Color = palette[i % palette.Length];
+                    i++;
+                }
+            }
+        }
+
+        private static IEnumerable<ColorScheme> LoadDiskSchemes()
+        {
+            var dir = Path.Combine(AppContext.BaseDirectory, "Schemes");
+            if (!Directory.Exists(dir))
+                yield break;
+
+            foreach (var path in Directory.GetFiles(dir, "*.json"))
+            {
+                ColorScheme scheme;
+                try
+                {
+                    scheme = ColorSchemeSerializer.Deserialize(File.ReadAllText(path));
+                }
+                catch
+                {
+                    continue;
+                }
+                if (!builtIns.ContainsKey(scheme.Name))
+                    yield return scheme;
+            }
+        }
+
+        private static ColorScheme BuildClassic() => new ColorScheme
+        {
+            Name = "Classic",
+            BackgroundColor = Color.DarkGray,
+            LayoutOutlineColor = Color.Gray,
+            LayoutFillColor = Color.WhiteSmoke,
+            BoundingBoxColor = Color.FromArgb(128, 128, 255),
+            RapidColor = Color.DodgerBlue,
+            OriginColor = Color.Gray,
+            EdgeSpacingColor = Color.FromArgb(180, 180, 180),
+            PreviewPartColor = Color.FromArgb(255, 140, 0),
+            PartColors = new[]
+            {
+                Color.FromArgb(205, 92, 92),
+                Color.FromArgb(148, 103, 189),
+                Color.FromArgb(75, 180, 175),
+                Color.FromArgb(210, 190, 75),
+                Color.FromArgb(190, 85, 175),
+                Color.FromArgb(185, 115, 85),
+                Color.FromArgb(120, 100, 190),
+                Color.FromArgb(200, 100, 140),
+                Color.FromArgb(80, 175, 155),
+                Color.FromArgb(195, 160, 85),
+                Color.FromArgb(175, 95, 160),
+                Color.FromArgb(215, 130, 130),
+            }
+        };
+
+        private static ColorScheme BuildPastel() => new ColorScheme
+        {
+            Name = "Pastel",
+            BackgroundColor = Color.FromArgb(70, 75, 85),
+            LayoutOutlineColor = Color.FromArgb(180, 180, 190),
+            LayoutFillColor = Color.FromArgb(245, 245, 248),
+            BoundingBoxColor = Color.FromArgb(128, 128, 255),
+            RapidColor = Color.DodgerBlue,
+            OriginColor = Color.FromArgb(160, 160, 160),
+            EdgeSpacingColor = Color.FromArgb(200, 200, 210),
+            PreviewPartColor = Color.FromArgb(255, 140, 0),
+            PartColors = new[]
+            {
+                Color.FromArgb(122, 179, 209), Color.FromArgb(254, 229, 174),
+                Color.FromArgb(143, 177, 229), Color.FromArgb(167, 172, 227),
+                Color.FromArgb(216, 249, 195), Color.FromArgb(209, 168, 216),
+                Color.FromArgb(222, 157, 190), Color.FromArgb(176, 255, 240),
+                Color.FromArgb(235, 205, 153), Color.FromArgb(177, 225, 180),
+                Color.FromArgb(125, 202, 241), Color.FromArgb(187, 206, 151),
+                Color.FromArgb(251, 175, 190), Color.FromArgb(129, 226, 227),
+                Color.FromArgb(255, 253, 207), Color.FromArgb(235, 205, 255),
+                Color.FromArgb(255, 197, 168), Color.FromArgb(116, 213, 234),
+                Color.FromArgb(190, 169, 122), Color.FromArgb(213, 159, 135),
+                Color.FromArgb(124, 184, 155), Color.FromArgb(255, 189, 214),
+                Color.FromArgb(146, 222, 255), Color.FromArgb(177, 173, 125),
+                Color.FromArgb(177, 166, 202), Color.FromArgb(197, 208, 255),
+                Color.FromArgb(255, 209, 243), Color.FromArgb(210, 255, 237),
+                Color.FromArgb(255, 237, 204), Color.FromArgb(167, 233, 255),
+                Color.FromArgb(182, 220, 255), Color.FromArgb(159, 177, 142),
+                Color.FromArgb(190, 248, 255), Color.FromArgb(187, 169, 136),
+                Color.FromArgb(199, 162, 168), Color.FromArgb(250, 255, 239),
+                Color.FromArgb(222, 233, 255), Color.FromArgb(255, 234, 225),
+                Color.FromArgb(240, 249, 255), Color.FromArgb(152, 176, 176),
+            }
+        };
+
+        private static ColorScheme BuildDark() => new ColorScheme
+        {
+            Name = "Dark",
+            BackgroundColor = Color.FromArgb(30, 30, 34),
+            LayoutOutlineColor = Color.FromArgb(90, 90, 95),
+            LayoutFillColor = Color.FromArgb(50, 50, 55),
+            BoundingBoxColor = Color.FromArgb(100, 160, 220),
+            RapidColor = Color.FromArgb(255, 200, 50),
+            OriginColor = Color.FromArgb(120, 120, 130),
+            EdgeSpacingColor = Color.FromArgb(90, 90, 100),
+            PreviewPartColor = Color.FromArgb(255, 170, 60),
+            PartColors = new[]
+            {
+                Color.FromArgb(255, 85, 85),   // Neon Red
+                Color.FromArgb(80, 220, 255),  // Electric Cyan
+                Color.FromArgb(255, 200, 50),  // Amber
+                Color.FromArgb(130, 255, 130), // Lime Green
+                Color.FromArgb(255, 130, 220), // Hot Pink
+                Color.FromArgb(255, 165, 70),  // Tangerine
+                Color.FromArgb(100, 180, 255), // Sky Blue
+                Color.FromArgb(200, 160, 255), // Lavender
+                Color.FromArgb(50, 230, 180),  // Mint
+                Color.FromArgb(255, 255, 100), // Lemon
+                Color.FromArgb(255, 120, 120), // Salmon
+                Color.FromArgb(140, 230, 255), // Ice Blue
+            }
+        };
+    }
+}

OpenNest/ColorSchemeSerializer.cs

@@ -0,0 +1,84 @@
+using System.Drawing;
+using System.Globalization;
+using System.Linq;
+using System.Text.Json;
+
+namespace OpenNest
+{
+    public static class ColorSchemeSerializer
+    {
+        private static readonly JsonSerializerOptions JsonOptions = new()
+        {
+            WriteIndented = true,
+            PropertyNamingPolicy = JsonNamingPolicy.CamelCase
+        };
+
+        public static string Serialize(ColorScheme scheme)
+        {
+            var dto = new ColorSchemeDto
+            {
+                Name = scheme.Name,
+                BackgroundColor = ToHex(scheme.BackgroundColor),
+                LayoutOutlineColor = ToHex(scheme.LayoutOutlineColor),
+                LayoutFillColor = ToHex(scheme.LayoutFillColor),
+                BoundingBoxColor = ToHex(scheme.BoundingBoxColor),
+                RapidColor = ToHex(scheme.RapidColor),
+                OriginColor = ToHex(scheme.OriginColor),
+                EdgeSpacingColor = ToHex(scheme.EdgeSpacingColor),
+                PreviewPartColor = ToHex(scheme.PreviewPartColor),
+                PartColors = scheme.PartColors.Select(ToHex).ToArray()
+            };
+            return JsonSerializer.Serialize(dto, JsonOptions);
+        }
+
+        public static ColorScheme Deserialize(string json)
+        {
+            var dto = JsonSerializer.Deserialize<ColorSchemeDto>(json, JsonOptions)
+                ?? throw new JsonException("ColorScheme JSON was null");
+
+            return new ColorScheme
+            {
+                Name = dto.Name ?? "Unnamed",
+                BackgroundColor = FromHex(dto.BackgroundColor),
+                LayoutOutlineColor = FromHex(dto.LayoutOutlineColor),
+                LayoutFillColor = FromHex(dto.LayoutFillColor),
+                BoundingBoxColor = FromHex(dto.BoundingBoxColor),
+                RapidColor = FromHex(dto.RapidColor),
+                OriginColor = FromHex(dto.OriginColor),
+                EdgeSpacingColor = FromHex(dto.EdgeSpacingColor),
+                PreviewPartColor = FromHex(dto.PreviewPartColor),
+                PartColors = (dto.PartColors ?? new string[0]).Select(FromHex).ToArray()
+            };
+        }
+
+        private static string ToHex(Color c) =>
+            "#" + c.R.ToString("X2") + c.G.ToString("X2") + c.B.ToString("X2");
+
+        private static Color FromHex(string hex)
+        {
+            if (string.IsNullOrWhiteSpace(hex))
+                return Color.Black;
+            var h = hex.TrimStart('#');
+            if (h.Length < 6)
+                return Color.Black;
+            var r = byte.Parse(h.Substring(0, 2), NumberStyles.HexNumber, CultureInfo.InvariantCulture);
+            var g = byte.Parse(h.Substring(2, 2), NumberStyles.HexNumber, CultureInfo.InvariantCulture);
+            var b = byte.Parse(h.Substring(4, 2), NumberStyles.HexNumber, CultureInfo.InvariantCulture);
+            return Color.FromArgb(r, g, b);
+        }
+
+        private class ColorSchemeDto
+        {
+            public string Name { get; set; }
+            public string BackgroundColor { get; set; }
+            public string LayoutOutlineColor { get; set; }
+            public string LayoutFillColor { get; set; }
+            public string BoundingBoxColor { get; set; }
+            public string RapidColor { get; set; }
+            public string OriginColor { get; set; }
+            public string EdgeSpacingColor { get; set; }
+            public string PreviewPartColor { get; set; }
+            public string[] PartColors { get; set; }
+        }
+    }
+}

OpenNest/Controls/CadText.cs

@@ -0,0 +1,16 @@
+using System.Drawing;
+using OpenNest.Geometry;
+
+namespace OpenNest.Controls
+{
+    public class CadText
+    {
+        public Vector Position { get; set; }
+        public string Value { get; set; }
+        public double Height { get; set; }
+        public double Rotation { get; set; }
+        public string LayerName { get; set; }
+        public StringAlignment HAlign { get; set; }
+        public StringAlignment VAlign { get; set; }
+    }
+}

OpenNest/Controls/CuttingPanel.cs

@@ -24,6 +24,8 @@ namespace OpenNest.Controls
 
         private readonly CheckBox chkTabsEnabled;
         private readonly NumericUpDown nudTabWidth;
+        private readonly RadioButton rbTabAll;
+        private readonly RadioButton rbAutoTab;
         private readonly NumericUpDown nudAutoTabMin;
         private readonly NumericUpDown nudAutoTabMax;
         private readonly NumericUpDown nudPierceClearance;
@@ -112,7 +114,7 @@ namespace OpenNest.Controls
             {
                 HeaderText = "Tabs",
                 Dock = DockStyle.Top,
-                ExpandedHeight = 120,
+                ExpandedHeight = 160,
                 IsExpanded = false
             };
 
@@ -122,44 +124,78 @@ namespace OpenNest.Controls
                 Location = new Point(12, 4),
                 AutoSize = true
             };
-            chkTabsEnabled.CheckedChanged += (s, e) =>
-            {
-                nudTabWidth.Enabled = chkTabsEnabled.Checked;
-                OnParametersChanged();
-            };
             tabsPanel.ContentPanel.Controls.Add(chkTabsEnabled);
 
             tabsPanel.ContentPanel.Controls.Add(new Label
             {
-                Text = "Width:",
+                Text = "Tab Size:",
                 Location = new Point(160, 6),
                 AutoSize = true
             });
 
-            nudTabWidth = CreateNumeric(215, 3, 0.25, 0.0625);
+            nudTabWidth = CreateNumeric(225, 3, 0.25, 0.0625);
             nudTabWidth.Enabled = false;
             tabsPanel.ContentPanel.Controls.Add(nudTabWidth);
 
+            rbTabAll = new RadioButton
+            {
+                Text = "Tab all parts",
+                Location = new Point(28, 28),
+                AutoSize = true,
+                Enabled = false,
+                Checked = true
+            };
+            tabsPanel.ContentPanel.Controls.Add(rbTabAll);
+
+            rbAutoTab = new RadioButton
+            {
+                Text = "Auto-tab when smallest part dimension is between:",
+                Location = new Point(28, 50),
+                AutoSize = true,
+                Enabled = false
+            };
+            tabsPanel.ContentPanel.Controls.Add(rbAutoTab);
+
             tabsPanel.ContentPanel.Controls.Add(new Label
             {
-                Text = "Auto-Tab Min Size:",
+                Text = "Min:",
-                Location = new Point(12, 32),
+                Location = new Point(44, 76),
                 AutoSize = true
             });
 
-            nudAutoTabMin = CreateNumeric(140, 29, 0, 0.0625);
+            nudAutoTabMin = CreateNumeric(77, 73, 0, 0.0625);
+            nudAutoTabMin.Enabled = false;
             tabsPanel.ContentPanel.Controls.Add(nudAutoTabMin);
 
             tabsPanel.ContentPanel.Controls.Add(new Label
             {
-                Text = "Auto-Tab Max Size:",
+                Text = "Max:",
-                Location = new Point(12, 58),
+                Location = new Point(210, 76),
                 AutoSize = true
             });
 
-            nudAutoTabMax = CreateNumeric(140, 55, 0, 0.0625);
+            nudAutoTabMax = CreateNumeric(245, 73, 0, 0.0625);
+            nudAutoTabMax.Enabled = false;
             tabsPanel.ContentPanel.Controls.Add(nudAutoTabMax);
 
+            chkTabsEnabled.CheckedChanged += (s, e) =>
+            {
+                var enabled = chkTabsEnabled.Checked;
+                nudTabWidth.Enabled = enabled;
+                rbTabAll.Enabled = enabled;
+                rbAutoTab.Enabled = enabled;
+                nudAutoTabMin.Enabled = enabled && rbAutoTab.Checked;
+                nudAutoTabMax.Enabled = enabled && rbAutoTab.Checked;
+                OnParametersChanged();
+            };
+
+            rbTabAll.CheckedChanged += (s, e) =>
+            {
+                nudAutoTabMin.Enabled = chkTabsEnabled.Checked && rbAutoTab.Checked;
+                nudAutoTabMax.Enabled = chkTabsEnabled.Checked && rbAutoTab.Checked;
+                OnParametersChanged();
+            };
+
             // Pierce section
             var piercePanel = new CollapsiblePanel
             {
@@ -246,13 +282,13 @@ namespace OpenNest.Controls
                 InternalLeadOut = BuildLeadOut(cboInternalLeadOut, pnlInternalLeadOut),
                 ArcCircleLeadIn = BuildLeadIn(cboArcCircleLeadIn, pnlArcCircleLeadIn),
                 ArcCircleLeadOut = BuildLeadOut(cboArcCircleLeadOut, pnlArcCircleLeadOut),
-                TabsEnabled = chkTabsEnabled.Checked,
+                TabsEnabled = chkTabsEnabled.Checked && rbTabAll.Checked,
                 TabConfig = new NormalTab { Size = (double)nudTabWidth.Value },
                 PierceClearance = (double)nudPierceClearance.Value,
                 RoundLeadInAngles = chkRoundLeadInAngles.Checked,
                 LeadInAngleIncrement = (double)nudLeadInAngleIncrement.Value,
-                AutoTabMinSize = (double)nudAutoTabMin.Value,
+                AutoTabMinSize = chkTabsEnabled.Checked && rbAutoTab.Checked ? (double)nudAutoTabMin.Value : 0,
-                AutoTabMaxSize = (double)nudAutoTabMax.Value
+                AutoTabMaxSize = chkTabsEnabled.Checked && rbAutoTab.Checked ? (double)nudAutoTabMax.Value : 0
             };
         }
 
@@ -267,7 +303,10 @@ namespace OpenNest.Controls
             LoadLeadIn(cboArcCircleLeadIn, pnlArcCircleLeadIn, p.ArcCircleLeadIn);
             LoadLeadOut(cboArcCircleLeadOut, pnlArcCircleLeadOut, p.ArcCircleLeadOut);
 
-            chkTabsEnabled.Checked = p.TabsEnabled;
+            var hasAutoTab = p.AutoTabMinSize > 0 || p.AutoTabMaxSize > 0;
+            chkTabsEnabled.Checked = p.TabsEnabled || hasAutoTab;
+            rbAutoTab.Checked = hasAutoTab;
+            rbTabAll.Checked = !hasAutoTab;
             if (p.TabConfig != null)
                 nudTabWidth.Value = (decimal)p.TabConfig.Size;
             nudPierceClearance.Value = (decimal)p.PierceClearance;

OpenNest/Controls/EntityView.cs

@@ -29,12 +29,17 @@ namespace OpenNest.Controls
         public List<Entity> SimplifierToleranceRight { get; set; }
         public List<Entity> OriginalEntities { get; set; }
         public bool ShowEntityLabels { get; set; }
+        public List<CadText> Texts { get; set; } = new List<CadText>();
+        public HashSet<Guid> TitleBlockEntityIds { get; set; }
 
         private readonly Pen gridPen = new Pen(Color.FromArgb(70, 70, 70));
         private readonly Dictionary<int, Pen> penCache = new Dictionary<int, Pen>();
+        private readonly Dictionary<int, Pen> ghostPenCache = new Dictionary<int, Pen>();
         private readonly Font labelFont = new Font("Segoe UI", 7f);
         private readonly SolidBrush labelBrush = new SolidBrush(Color.FromArgb(220, 255, 255, 200));
         private readonly SolidBrush labelBackBrush = new SolidBrush(Color.FromArgb(33, 40, 48));
+        private readonly SolidBrush textBrush = new SolidBrush(Color.FromArgb(180, 200, 200, 200));
+        private readonly SolidBrush ghostTextBrush = new SolidBrush(Color.FromArgb(50, 200, 200, 200));
 
         public event EventHandler<Line> LinePicked;
         public event EventHandler PickCancelled;
@@ -100,6 +105,13 @@ namespace OpenNest.Controls
             foreach (var entity in Entities)
             {
                 if (IsEtchLayer(entity.Layer)) continue;
+
+                if (TitleBlockEntityIds != null && TitleBlockEntityIds.Contains(entity.Id))
+                {
+                    DrawGhostEntity(e.Graphics, entity);
+                    continue;
+                }
+
                 var isHighlighted = simplifierHighlightSet != null && simplifierHighlightSet.Contains(entity);
                 var pen = isHighlighted
                     ? GetEntityPen(Color.FromArgb(60, entity.Color))
@@ -116,6 +128,8 @@ namespace OpenNest.Controls
                 DrawEntity(e.Graphics, entity, pen);
             }
 
+            DrawTexts(e.Graphics);
+
             if (ShowEntityLabels)
                 DrawEntityLabels(e.Graphics);
 
@@ -239,11 +253,26 @@ namespace OpenNest.Controls
             return pen;
         }
 
+        private Pen GetGhostPen(Color color)
+        {
+            var ghostColor = Color.FromArgb(60, color.R, color.G, color.B);
+            var argb = ghostColor.ToArgb();
+            if (!ghostPenCache.TryGetValue(argb, out var pen))
+            {
+                pen = new Pen(ghostColor);
+                ghostPenCache[argb] = pen;
+            }
+            return pen;
+        }
+
         public void ClearPenCache()
         {
             foreach (var pen in penCache.Values)
                 pen.Dispose();
             penCache.Clear();
+            foreach (var pen in ghostPenCache.Values)
+                pen.Dispose();
+            ghostPenCache.Clear();
         }
 
         private static bool IsEtchLayer(Layer layer) =>
@@ -408,10 +437,29 @@ namespace OpenNest.Controls
                 labelFont.Dispose();
                 labelBrush.Dispose();
                 labelBackBrush.Dispose();
+                textBrush.Dispose();
+                ghostTextBrush.Dispose();
             }
             base.Dispose(disposing);
         }
 
+        private void DrawGhostEntity(Graphics g, Entity e)
+        {
+            var pen = GetGhostPen(e.Color);
+            switch (e.Type)
+            {
+                case EntityType.Arc:
+                    DrawArc(g, (Arc)e, pen);
+                    break;
+                case EntityType.Circle:
+                    DrawCircle(g, (Circle)e, pen);
+                    break;
+                case EntityType.Line:
+                    DrawLine(g, (Line)e, pen);
+                    break;
+            }
+        }
+
         private void DrawEntity(Graphics g, Entity e, Pen pen)
         {
             if (!e.Layer.IsVisible || !e.IsVisible)
@@ -474,6 +522,36 @@ namespace OpenNest.Controls
                 diameter);
         }
 
+        private void DrawTexts(Graphics g)
+        {
+            if (Texts == null || Texts.Count == 0)
+                return;
+
+            using var sf = new StringFormat();
+
+            foreach (var text in Texts)
+            {
+                var pos = PointWorldToGraph(text.Position);
+                var fontSize = LengthWorldToGui(text.Height);
+                if (fontSize < 2f) continue;
+
+                var state = g.Save();
+                g.TranslateTransform(pos.X, pos.Y);
+
+                if (text.Rotation != 0)
+                    g.RotateTransform((float)OpenNest.Math.Angle.ToDegrees(text.Rotation));
+
+                sf.Alignment = text.HAlign;
+                sf.LineAlignment = text.VAlign;
+
+                var brush = TitleBlockEntityIds != null && TitleBlockEntityIds.Count > 0
+                    ? ghostTextBrush : textBrush;
+                using var font = new Font("Segoe UI", fontSize, GraphicsUnit.Pixel);
+                g.DrawString(text.Value, font, brush, 0, 0, sf);
+                g.Restore(state);
+            }
+        }
+
         private void DrawPoint(Graphics g, Vector pt, Pen pen)
         {
             var pt1 = PointWorldToGraph(pt);

OpenNest/Controls/FileListControl.cs

@@ -20,8 +20,10 @@ namespace OpenNest.Controls
         public List<Entity> OriginalEntities { get; set; }
         public List<Bend> Bends { get; set; } = new();
         public HashSet<Guid> SuppressedEntityIds { get; set; }
+        public HashSet<Guid> TitleBlockEntityIds { get; set; }
         public Box Bounds { get; set; }
         public int EntityCount { get; set; }
+        public List<CadText> Texts { get; set; } = new();
     }
 
     public class FileListControl : Control

OpenNest/Controls/FilterPanel.cs

@@ -27,6 +27,7 @@ namespace OpenNest.Controls
         public event EventHandler FilterChanged;
         public event EventHandler<int> BendLineSelected;
         public event EventHandler<int> BendLineRemoved;
+        public event EventHandler<int> BendLineEdited;
         public event EventHandler AddBendLineClicked;
 
         public FilterPanel()
@@ -51,6 +52,18 @@ namespace OpenNest.Controls
             bendLinesList.SelectedIndexChanged += (s, e) =>
                 BendLineSelected?.Invoke(this, bendLinesList.SelectedIndex);
 
+            var bendEditLink = new LinkLabel
+            {
+                Text = "Edit",
+                AutoSize = true,
+                Font = new Font("Segoe UI", 8f)
+            };
+            bendEditLink.LinkClicked += (s, e) =>
+            {
+                if (bendLinesList.SelectedIndex >= 0)
+                    BendLineEdited?.Invoke(this, bendLinesList.SelectedIndex);
+            };
+
             var bendDeleteLink = new LinkLabel
             {
                 Text = "Remove",
@@ -63,6 +76,12 @@ namespace OpenNest.Controls
                     BendLineRemoved?.Invoke(this, bendLinesList.SelectedIndex);
             };
 
+            bendLinesList.DoubleClick += (s, e) =>
+            {
+                if (bendLinesList.SelectedIndex >= 0)
+                    BendLineEdited?.Invoke(this, bendLinesList.SelectedIndex);
+            };
+
             bendAddLink = new LinkLabel
             {
                 Text = "Add Bend Line",
@@ -80,6 +99,7 @@ namespace OpenNest.Controls
                 WrapContents = false
             };
             bendLinksPanel.Controls.Add(bendAddLink);
+            bendLinksPanel.Controls.Add(bendEditLink);
             bendLinksPanel.Controls.Add(bendDeleteLink);
 
             bendLinesPanel.ContentPanel.Controls.Add(bendLinesList);

OpenNest/Controls/PlateRenderer.cs

@@ -385,85 +385,20 @@ namespace OpenNest.Controls
 
         private void DrawRapids(Graphics g)
         {
+            var pen = view.ColorScheme.RapidPen;
             var pos = new Vector(0, 0);
 
             for (var i = 0; i < view.Plate.Parts.Count; ++i)
             {
                 var part = view.Plate.Parts[i];
-                var pgm = part.Program;
+                var segments = RapidEnumerator.Enumerate(part.Program, part.Location, pos);
 
-                var piercePoint = GetFirstPiercePoint(pgm, part.Location);
+                foreach (var seg in segments)
-                DrawLine(g, pos, piercePoint, view.ColorScheme.RapidPen);
-
-                pos = piercePoint;
-                DrawRapids(g, pgm, part.Location, ref pos, skipFirstRapid: true);
-            }
-        }
-
-        private static Vector GetFirstPiercePoint(Program pgm, Vector partLocation)
                 {
-            for (var i = 0; i < pgm.Length; i++)
+                    DrawLine(g, seg.From, seg.To, pen);
-            {
+                    pos = seg.To;
-                if (pgm[i] is SubProgramCall call && call.Program != null)
-                    return GetFirstPiercePoint(call.Program, partLocation + call.Offset);
-
-                if (pgm[i] is Motion motion)
-                {
-                    return motion.EndPoint + partLocation;
                 }
             }
-            return partLocation;
-        }
-
-        private void DrawRapids(Graphics g, Program pgm, Vector basePos, ref Vector pos, bool skipFirstRapid = false)
-        {
-            var firstRapidSkipped = false;
-
-            for (var i = 0; i < pgm.Length; ++i)
-            {
-                var code = pgm[i];
-
-                if (code is SubProgramCall { Program: { } program } call)
-                {
-                    // A SubProgramCall is a coordinate-frame shift, not a physical
-                    // rapid to the hole center. The Cincinnati post emits it as a
-                    // G52 bracket, so the physical rapid is the sub-program's first
-                    // motion, which goes straight from here to the lead-in pierce.
-                    // Look ahead for that pierce point and draw the direct rapid,
-                    // then recurse with skipFirstRapid so the sub doesn't also draw
-                    // its first rapid on top. See docs/cincinnati-post-output.md.
-                    var holeBase = basePos + call.Offset;
-                    var firstPierce = GetFirstPiercePoint(program, holeBase);
-
-                    if (ShouldDrawRapid(skipFirstRapid, ref firstRapidSkipped))
-                        DrawLine(g, pos, firstPierce, view.ColorScheme.RapidPen);
-
-                    var subPos = holeBase;
-                    DrawRapids(g, program, holeBase, ref subPos, skipFirstRapid: true);
-                    pos = subPos;
-                }
-                else if (code is Motion motion)
-                {
-                    var endpt = pgm.Mode == Mode.Incremental
-                        ? motion.EndPoint + pos
-                        : motion.EndPoint;
-
-                    if (code.Type == CodeType.RapidMove && ShouldDrawRapid(skipFirstRapid, ref firstRapidSkipped))
-                        DrawLine(g, pos, endpt, view.ColorScheme.RapidPen);
-
-                    pos = endpt;
-                }
-            }
-        }
-
-        private static bool ShouldDrawRapid(bool skipFirstRapid, ref bool firstRapidSkipped)
-        {
-            if (skipFirstRapid && !firstRapidSkipped)
-            {
-                firstRapidSkipped = true;
-                return false;
-            }
-            return true;
         }
 
         private void DrawAllPiercePoints(Graphics g)

OpenNest/Controls/PlateView.cs

@@ -464,6 +464,9 @@ namespace OpenNest.Controls
 
         protected override void OnPaint(PaintEventArgs e)
         {
+            if (BackColor != ColorScheme.BackgroundColor)
+                BackColor = ColorScheme.BackgroundColor;
+
             e.Graphics.SmoothingMode = SmoothingMode.HighSpeed;
 
             if (DrawOrigin)

OpenNest/Controls/ProgramEditorControl.cs

@@ -209,14 +209,7 @@ namespace OpenNest.Controls
 
         private static Entity CloneEntity(Entity entity, Color color)
         {
-            Entity clone = entity switch
+            var clone = entity.Clone();
-            {
-                Line line => new Line(line.StartPoint, line.EndPoint) { Layer = line.Layer, IsVisible = line.IsVisible },
-                Arc arc => new Arc(arc.Center, arc.Radius, arc.StartAngle, arc.EndAngle, arc.IsReversed) { Layer = arc.Layer, IsVisible = arc.IsVisible },
-                Circle circle => new Circle(circle.Center, circle.Radius) { Layer = circle.Layer, IsVisible = circle.IsVisible },
-                _ => null,
-            };
-            if (clone != null)
             clone.Color = color;
             return clone;
         }

OpenNest/Forms/BendLineDialog.cs

@@ -99,5 +99,17 @@ namespace OpenNest.Forms
         public double BendAngle => (double)numAngle.Value;
 
         public double? BendRadius => chkRadius.Checked ? (double)numRadius.Value : null;
+
+        public void LoadBend(Bend bend)
+        {
+            cboDirection.SelectedIndex = bend.Direction == BendDirection.Up ? 1 : 0;
+            if (bend.Angle.HasValue)
+                numAngle.Value = (decimal)bend.Angle.Value;
+            if (bend.Radius.HasValue)
+            {
+                chkRadius.Checked = true;
+                numRadius.Value = (decimal)bend.Radius.Value;
+            }
+        }
     }
 }

OpenNest/Forms/BomImportForm.cs

@@ -165,7 +165,8 @@ namespace OpenNest.Forms
                 else
                 {
                     var lookupName = item.FileName;
-                    if (lookupName.EndsWith(".dxf", StringComparison.OrdinalIgnoreCase))
+                    if (lookupName.EndsWith(".dxf", StringComparison.OrdinalIgnoreCase)
+                        || lookupName.EndsWith(".dwg", StringComparison.OrdinalIgnoreCase))
                         lookupName = Path.GetFileNameWithoutExtension(lookupName);
 
                     if (matchedPaths.TryGetValue(lookupName, out var dxfPath))

OpenNest/Forms/CadConverterForm.cs

@@ -41,6 +41,7 @@ namespace OpenNest.Forms
             filterPanel.FilterChanged += OnFilterChanged;
             filterPanel.BendLineSelected += OnBendLineSelected;
             filterPanel.BendLineRemoved += OnBendLineRemoved;
+            filterPanel.BendLineEdited += OnBendLineEdited;
             filterPanel.AddBendLineClicked += OnAddBendLineClicked;
             entityView1.LinePicked += OnLinePicked;
             entityView1.PickCancelled += OnPickCancelled;
@@ -91,9 +92,18 @@ namespace OpenNest.Forms
                     Customer = string.Empty,
                     Bends = result.Bends,
                     Bounds = result.Bounds,
-                    EntityCount = result.Entities.Count
+                    EntityCount = result.Entities.Count,
+                    Texts = ExtractTexts(result.Document),
+                    TitleBlockEntityIds = result.TitleBlockEntityIds,
                 };
 
+                if (result.TitleBlockEntityIds != null && result.TitleBlockEntityIds.Count > 0)
+                {
+                    item.SuppressedEntityIds ??= new HashSet<Guid>();
+                    foreach (var id in result.TitleBlockEntityIds)
+                        item.SuppressedEntityIds.Add(id);
+                }
+
                 if (InvokeRequired)
                     BeginInvoke((Action)(() => fileList.AddItem(item)));
                 else
@@ -151,6 +161,8 @@ namespace OpenNest.Forms
             entityView1.Entities.Clear();
             entityView1.Entities.AddRange(item.Entities);
             entityView1.Bends = item.Bends ?? new List<Bend>();
+            entityView1.Texts = item.Texts ?? new List<CadText>();
+            entityView1.TitleBlockEntityIds = item.TitleBlockEntityIds;
 
             item.Entities.ForEach(e => e.IsVisible = true);
             if (item.Entities.Any(e => e.Layer != null))
@@ -292,6 +304,29 @@ namespace OpenNest.Forms
             entityView1.Invalidate();
         }
 
+        private void OnBendLineEdited(object sender, int index)
+        {
+            var item = CurrentItem;
+            if (item == null || index < 0 || index >= item.Bends.Count) return;
+
+            var bend = item.Bends[index];
+            using var dialog = new BendLineDialog();
+            dialog.LoadBend(bend);
+
+            if (dialog.ShowDialog(this) != DialogResult.OK) return;
+
+            bend.Direction = dialog.Direction;
+            bend.Angle = dialog.BendAngle;
+            bend.Radius = dialog.BendRadius;
+
+            Bend.UpdateEtchEntities(item.Entities, item.Bends);
+            entityView1.Entities.Clear();
+            entityView1.Entities.AddRange(item.Entities);
+            entityView1.Bends = item.Bends;
+            filterPanel.LoadItem(item.Entities, item.Bends);
+            entityView1.Invalidate();
+        }
+
         private void OnQuantityChanged(object sender, EventArgs e)
         {
             var item = CurrentItem;
@@ -449,7 +484,8 @@ namespace OpenNest.Forms
             {
                 var files = (string[])e.Data.GetData(DataFormats.FileDrop);
                 var dxfFiles = files.Where(f =>
-                    f.EndsWith(".dxf", StringComparison.OrdinalIgnoreCase)).ToArray();
+                    f.EndsWith(".dxf", StringComparison.OrdinalIgnoreCase) ||
+                    f.EndsWith(".dwg", StringComparison.OrdinalIgnoreCase)).ToArray();
                 if (dxfFiles.Length > 0)
                     AddFiles(dxfFiles);
             }
@@ -779,6 +815,102 @@ namespace OpenNest.Forms
 
         #endregion
 
+        private static List<CadText> ExtractTexts(ACadSharp.CadDocument doc)
+        {
+            var texts = new List<CadText>();
+            if (doc == null) return texts;
+
+            foreach (var entity in doc.Entities)
+            {
+                switch (entity)
+                {
+                    case ACadSharp.Entities.MText mtext:
+                        var (mh, mv) = MapAttachmentPoint(mtext.AttachmentPoint);
+                        texts.Add(new CadText
+                        {
+                            Position = new Vector(mtext.InsertPoint.X, mtext.InsertPoint.Y),
+                            Value = ReplaceControlCodes(StripMTextFormatting(mtext.Value)),
+                            Height = mtext.Height,
+                            Rotation = mtext.Rotation,
+                            LayerName = mtext.Layer?.Name,
+                            HAlign = mh,
+                            VAlign = mv,
+                        });
+                        break;
+
+                    case ACadSharp.Entities.TextEntity text:
+                        var useAlignment = text.HorizontalAlignment != 0
+                            || text.VerticalAlignment != 0;
+                        var pt = useAlignment ? text.AlignmentPoint : text.InsertPoint;
+                        var ha = text.HorizontalAlignment switch
+                        {
+                            ACadSharp.Entities.TextHorizontalAlignment.Center => System.Drawing.StringAlignment.Center,
+                            ACadSharp.Entities.TextHorizontalAlignment.Right => System.Drawing.StringAlignment.Far,
+                            _ => System.Drawing.StringAlignment.Near,
+                        };
+                        texts.Add(new CadText
+                        {
+                            Position = new Vector(pt.X, pt.Y),
+                            Value = ReplaceControlCodes(text.Value),
+                            Height = text.Height,
+                            Rotation = text.Rotation,
+                            LayerName = text.Layer?.Name,
+                            HAlign = ha,
+                        });
+                        break;
+                }
+            }
+
+            return texts;
+        }
+
+        private static (System.Drawing.StringAlignment h, System.Drawing.StringAlignment v) MapAttachmentPoint(
+            ACadSharp.Entities.AttachmentPointType apt)
+        {
+            var h = apt switch
+            {
+                ACadSharp.Entities.AttachmentPointType.TopCenter
+                    or ACadSharp.Entities.AttachmentPointType.MiddleCenter
+                    or ACadSharp.Entities.AttachmentPointType.BottomCenter => System.Drawing.StringAlignment.Center,
+                ACadSharp.Entities.AttachmentPointType.TopRight
+                    or ACadSharp.Entities.AttachmentPointType.MiddleRight
+                    or ACadSharp.Entities.AttachmentPointType.BottomRight => System.Drawing.StringAlignment.Far,
+                _ => System.Drawing.StringAlignment.Near,
+            };
+            var v = apt switch
+            {
+                ACadSharp.Entities.AttachmentPointType.MiddleLeft
+                    or ACadSharp.Entities.AttachmentPointType.MiddleCenter
+                    or ACadSharp.Entities.AttachmentPointType.MiddleRight => System.Drawing.StringAlignment.Center,
+                ACadSharp.Entities.AttachmentPointType.BottomLeft
+                    or ACadSharp.Entities.AttachmentPointType.BottomCenter
+                    or ACadSharp.Entities.AttachmentPointType.BottomRight => System.Drawing.StringAlignment.Far,
+                _ => System.Drawing.StringAlignment.Near,
+            };
+            return (h, v);
+        }
+
+        private static string StripMTextFormatting(string text)
+        {
+            if (string.IsNullOrEmpty(text)) return text;
+            var result = System.Text.RegularExpressions.Regex.Replace(text, @"\\[A-Za-z][^;]*;", "");
+            result = result.Replace("{", "").Replace("}", "");
+            return result.Trim();
+        }
+
+        private static string ReplaceControlCodes(string text)
+        {
+            if (string.IsNullOrEmpty(text)) return text;
+            return text
+                .Replace("%%p", "±")
+                .Replace("%%P", "±")
+                .Replace("%%d", "°")
+                .Replace("%%D", "°")
+                .Replace("%%c", "⌀")
+                .Replace("%%C", "⌀")
+                .Replace("%%%", "%");
+        }
+
         private void filterPanel_Paint(object sender, PaintEventArgs e)
         {
 

OpenNest/Forms/EditNestForm.Designer.cs

@@ -47,11 +47,9 @@
             drawingListBox1 = new OpenNest.Controls.DrawingListBox();
             toolStrip2 = new System.Windows.Forms.ToolStrip();
             toolStripButton2 = new System.Windows.Forms.ToolStripButton();
-            toolStripSeparator4 = new System.Windows.Forms.ToolStripSeparator();
+            shapeLibraryButton = new System.Windows.Forms.ToolStripButton();
             editDrawingsButton = new System.Windows.Forms.ToolStripButton();
-            toolStripSeparator1 = new System.Windows.Forms.ToolStripSeparator();
             toolStripButton3 = new System.Windows.Forms.ToolStripButton();
-            toolStripSeparator2 = new System.Windows.Forms.ToolStripSeparator();
             hideNestedButton = new System.Windows.Forms.ToolStripButton();
             ((System.ComponentModel.ISupportInitialize)splitContainer).BeginInit();
             splitContainer.Panel1.SuspendLayout();
@@ -219,7 +217,7 @@
             // 
             toolStrip2.GripStyle = System.Windows.Forms.ToolStripGripStyle.Hidden;
             toolStrip2.ImageScalingSize = new System.Drawing.Size(20, 20);
-            toolStrip2.Items.AddRange(new System.Windows.Forms.ToolStripItem[] { toolStripButton2, toolStripSeparator4, editDrawingsButton, toolStripSeparator1, toolStripButton3, toolStripSeparator2, hideNestedButton });
+            toolStrip2.Items.AddRange(new System.Windows.Forms.ToolStripItem[] { toolStripButton2, shapeLibraryButton, editDrawingsButton, toolStripButton3, hideNestedButton });
             toolStrip2.Location = new System.Drawing.Point(4, 3);
             toolStrip2.Name = "toolStrip2";
             toolStrip2.Size = new System.Drawing.Size(265, 27);
@@ -238,10 +236,15 @@
             toolStripButton2.Text = "Import Drawings";
             toolStripButton2.Click += ImportDrawings_Click;
             //
-            // toolStripSeparator4
+            // shapeLibraryButton
             //
-            toolStripSeparator4.Name = "toolStripSeparator4";
+            shapeLibraryButton.DisplayStyle = System.Windows.Forms.ToolStripItemDisplayStyle.Image;
-            toolStripSeparator4.Size = new System.Drawing.Size(6, 27);
+            shapeLibraryButton.Image = Properties.Resources.shapes;
+            shapeLibraryButton.Name = "shapeLibraryButton";
+            shapeLibraryButton.Padding = new System.Windows.Forms.Padding(5, 0, 5, 0);
+            shapeLibraryButton.Size = new System.Drawing.Size(34, 24);
+            shapeLibraryButton.Text = "Shape Library";
+            shapeLibraryButton.Click += ShapeLibrary_Click;
             //
             // editDrawingsButton
             //
@@ -253,11 +256,6 @@
             editDrawingsButton.Text = "Edit Drawings in Converter";
             editDrawingsButton.Click += EditDrawingsInConverter_Click;
             //
-            // toolStripSeparator1
-            // 
-            toolStripSeparator1.Name = "toolStripSeparator1";
-            toolStripSeparator1.Size = new System.Drawing.Size(6, 27);
-            // 
             // toolStripButton3
             //
             toolStripButton3.DisplayStyle = System.Windows.Forms.ToolStripItemDisplayStyle.Image;
@@ -269,11 +267,6 @@
             toolStripButton3.Text = "Cleanup unused Drawings";
             toolStripButton3.Click += CleanUnusedDrawings_Click;
             //
-            // toolStripSeparator2
-            // 
-            toolStripSeparator2.Name = "toolStripSeparator2";
-            toolStripSeparator2.Size = new System.Drawing.Size(6, 27);
-            // 
             // hideNestedButton
             // 
             hideNestedButton.CheckOnClick = true;
@@ -329,11 +322,9 @@
         private System.Windows.Forms.ColumnHeader utilColumn;
         private System.Windows.Forms.ToolStrip toolStrip2;
         private System.Windows.Forms.ToolStripButton toolStripButton2;
-        private System.Windows.Forms.ToolStripSeparator toolStripSeparator4;
+        private System.Windows.Forms.ToolStripButton shapeLibraryButton;
         private System.Windows.Forms.ToolStripButton editDrawingsButton;
-        private System.Windows.Forms.ToolStripSeparator toolStripSeparator1;
         private System.Windows.Forms.ToolStripButton toolStripButton3;
-        private System.Windows.Forms.ToolStripSeparator toolStripSeparator2;
         private System.Windows.Forms.ToolStripButton hideNestedButton;
         private System.Windows.Forms.ToolStripSeparator toolStripSeparator3;
         private System.Windows.Forms.ToolStripButton toolStripLabel1;

OpenNest/Forms/EditNestForm.cs

@@ -7,6 +7,7 @@ using OpenNest.Engine.Sequencing;
 using OpenNest.IO;
 using OpenNest.Math;
 using OpenNest.Properties;
+using OpenNest.Shapes;
 using System;
 using System.ComponentModel;
 using System.Diagnostics;
@@ -328,7 +329,7 @@ namespace OpenNest.Forms
         {
             var dlg = new OpenFileDialog();
             dlg.Multiselect = true;
-            dlg.Filter = "DXF Files (*.dxf) | *.dxf";
+            dlg.Filter = "CAD Files (*.dxf;*.dwg)|*.dxf;*.dwg|DXF Files (*.dxf)|*.dxf|DWG Files (*.dwg)|*.dwg";
 
             if (dlg.ShowDialog() != DialogResult.OK)
                 return;
@@ -345,7 +346,6 @@ namespace OpenNest.Forms
             drawings.ForEach(d => Nest.Drawings.Add(d));
 
             UpdateDrawingList();
-            tabControl1.SelectedIndex = 1;
         }
 
         public bool Export()
@@ -453,7 +453,11 @@ namespace OpenNest.Forms
 
         public void ResizePlateToFitParts()
         {
-            PlateView.Plate.AutoSize(Settings.Default.AutoSizePlateFactor);
+            var options = new PlateSizeOptions
+            {
+                SnapIncrement = Settings.Default.AutoSizePlateFactor,
+            };
+            PlateView.Plate.SnapToStandardSize(options);
             PlateView.ZoomToPlate();
             PlateView.Refresh();
             UpdatePlateList();
@@ -870,6 +874,18 @@ namespace OpenNest.Forms
             Import();
         }
 
+        private void ShapeLibrary_Click(object sender, EventArgs e)
+        {
+            var form = new ShapeLibraryForm(Nest.Drawings.Select(d => d.Name));
+            form.ShowDialog();
+
+            var drawings = form.GetDrawings();
+            if (drawings.Count == 0) return;
+
+            drawings.ForEach(d => Nest.Drawings.Add(d));
+            UpdateDrawingList();
+        }
+
         private void EditDrawingsInConverter_Click(object sender, EventArgs e)
         {
             if (Nest.Drawings.Count == 0)

OpenNest/Forms/MainForm.cs

@@ -71,6 +71,7 @@ namespace OpenNest.Forms
             NestEngineRegistry.LoadPlugins(enginesDir);
 
             OptionsForm.ApplyDisabledStrategies();
+            ColorSchemeRegistry.ApplyActiveFromSettings();
 
             foreach (var engine in NestEngineRegistry.AvailableEngines)
                 engineComboBox.Items.Add(engine.Name);
@@ -836,7 +837,7 @@ namespace OpenNest.Forms
         {
             if (activeForm == null) return;
 
-            var form = new ShapeLibraryForm();
+            var form = new ShapeLibraryForm(activeForm.Nest.Drawings.Select(d => d.Name));
             form.ShowDialog();
 
             var drawings = form.GetDrawings();

OpenNest/Forms/OptionsForm.Designer.cs

@@ -42,6 +42,8 @@
             this.bottomPanel1 = new OpenNest.Controls.BottomPanel();
             this.strategyGrid = new System.Windows.Forms.DataGridView();
             this.strategyGroupBox = new System.Windows.Forms.GroupBox();
+            this.colorSchemeLabel = new System.Windows.Forms.Label();
+            this.colorSchemeCombo = new System.Windows.Forms.ComboBox();
             ((System.ComponentModel.ISupportInitialize)(this.numericUpDown1)).BeginInit();
             this.tableLayoutPanel1.SuspendLayout();
             this.bottomPanel1.SuspendLayout();
@@ -95,15 +97,18 @@
             this.tableLayoutPanel1.Controls.Add(this.label1, 0, 1);
             this.tableLayoutPanel1.Controls.Add(this.textBox1, 1, 0);
             this.tableLayoutPanel1.Controls.Add(this.label3, 0, 0);
-            this.tableLayoutPanel1.Controls.Add(this.checkBox1, 0, 2);
+            this.tableLayoutPanel1.Controls.Add(this.colorSchemeLabel, 0, 2);
+            this.tableLayoutPanel1.Controls.Add(this.colorSchemeCombo, 1, 2);
+            this.tableLayoutPanel1.Controls.Add(this.checkBox1, 0, 3);
             this.tableLayoutPanel1.Controls.Add(this.numericUpDown1, 1, 1);
             this.tableLayoutPanel1.Controls.Add(this.button1, 3, 0);
             this.tableLayoutPanel1.Location = new System.Drawing.Point(12, 12);
             this.tableLayoutPanel1.Name = "tableLayoutPanel1";
-            this.tableLayoutPanel1.RowCount = 3;
+            this.tableLayoutPanel1.RowCount = 4;
-            this.tableLayoutPanel1.RowStyles.Add(new System.Windows.Forms.RowStyle(System.Windows.Forms.SizeType.Percent, 33.33F));
+            this.tableLayoutPanel1.RowStyles.Add(new System.Windows.Forms.RowStyle(System.Windows.Forms.SizeType.Percent, 25F));
-            this.tableLayoutPanel1.RowStyles.Add(new System.Windows.Forms.RowStyle(System.Windows.Forms.SizeType.Percent, 33.33F));
+            this.tableLayoutPanel1.RowStyles.Add(new System.Windows.Forms.RowStyle(System.Windows.Forms.SizeType.Percent, 25F));
-            this.tableLayoutPanel1.RowStyles.Add(new System.Windows.Forms.RowStyle(System.Windows.Forms.SizeType.Percent, 33.34F));
+            this.tableLayoutPanel1.RowStyles.Add(new System.Windows.Forms.RowStyle(System.Windows.Forms.SizeType.Percent, 25F));
+            this.tableLayoutPanel1.RowStyles.Add(new System.Windows.Forms.RowStyle(System.Windows.Forms.SizeType.Percent, 25F));
             this.tableLayoutPanel1.Size = new System.Drawing.Size(684, 160);
             this.tableLayoutPanel1.TabIndex = 0;
             // 
@@ -198,6 +203,25 @@
             this.strategyGroupBox.TabStop = false;
             this.strategyGroupBox.Text = "Fill Strategies";
             //
+            // colorSchemeLabel
+            //
+            this.colorSchemeLabel.Anchor = ((System.Windows.Forms.AnchorStyles)((System.Windows.Forms.AnchorStyles.Left | System.Windows.Forms.AnchorStyles.Right)));
+            this.colorSchemeLabel.AutoSize = true;
+            this.colorSchemeLabel.Location = new System.Drawing.Point(3, 92);
+            this.colorSchemeLabel.Name = "colorSchemeLabel";
+            this.colorSchemeLabel.Size = new System.Drawing.Size(145, 16);
+            this.colorSchemeLabel.TabIndex = 10;
+            this.colorSchemeLabel.Text = "Color scheme:";
+            //
+            // colorSchemeCombo
+            //
+            this.colorSchemeCombo.Anchor = ((System.Windows.Forms.AnchorStyles)((System.Windows.Forms.AnchorStyles.Left | System.Windows.Forms.AnchorStyles.Right)));
+            this.colorSchemeCombo.DropDownStyle = System.Windows.Forms.ComboBoxStyle.DropDownList;
+            this.colorSchemeCombo.Location = new System.Drawing.Point(154, 89);
+            this.colorSchemeCombo.Name = "colorSchemeCombo";
+            this.colorSchemeCombo.Size = new System.Drawing.Size(130, 24);
+            this.colorSchemeCombo.TabIndex = 11;
+            //
             // OptionsForm
             //
             this.AcceptButton = this.saveButton;
@@ -239,5 +263,7 @@
         private System.Windows.Forms.Button button1;
         private System.Windows.Forms.DataGridView strategyGrid;
         private System.Windows.Forms.GroupBox strategyGroupBox;
+        private System.Windows.Forms.Label colorSchemeLabel;
+        private System.Windows.Forms.ComboBox colorSchemeCombo;
     }
 }

OpenNest/Forms/OptionsForm.cs

@@ -68,6 +68,13 @@ namespace OpenNest.Forms
             checkBox1.Checked = Settings.Default.CreateNewNestOnOpen;
             numericUpDown1.Value = (decimal)Settings.Default.AutoSizePlateFactor;
 
+            colorSchemeCombo.Items.Clear();
+            foreach (var scheme in ColorSchemeRegistry.AllSchemes)
+                colorSchemeCombo.Items.Add(scheme.Name);
+            var active = Settings.Default.ActiveColorScheme;
+            var idx = colorSchemeCombo.Items.IndexOf(active);
+            colorSchemeCombo.SelectedIndex = idx >= 0 ? idx : 0;
+
             var disabledNames = ParseDisabledStrategies(Settings.Default.DisabledStrategies);
             foreach (DataGridViewRow row in strategyGrid.Rows)
                 row.Cells["Enabled"].Value = !disabledNames.Contains((string)row.Cells["Name"].Value);
@@ -78,6 +85,7 @@ namespace OpenNest.Forms
             Settings.Default.NestTemplatePath = textBox1.Text;
             Settings.Default.CreateNewNestOnOpen = checkBox1.Checked;
             Settings.Default.AutoSizePlateFactor = (double)numericUpDown1.Value;
+            Settings.Default.ActiveColorScheme = colorSchemeCombo.SelectedItem as string ?? "Classic";
 
             var disabledNames = new List<string>();
             foreach (DataGridViewRow row in strategyGrid.Rows)
@@ -89,6 +97,10 @@ namespace OpenNest.Forms
 
             Settings.Default.Save();
             ApplyDisabledStrategies();
+            ColorSchemeRegistry.ApplyActiveFromSettings();
+
+            foreach (Form f in Application.OpenForms)
+                f.Invalidate(invalidateChildren: true);
         }
 
         /// <summary>

OpenNest/Forms/ShapeLibraryForm.cs

@@ -21,12 +21,17 @@ namespace OpenNest.Forms
         private readonly List<Drawing> addedDrawings = new List<Drawing>();
         private readonly List<ShapeEntry> shapeEntries = new List<ShapeEntry>();
         private readonly List<ParameterBinding> parameterBindings = new List<ParameterBinding>();
+        private readonly HashSet<string> existingNames;
 
         private ShapeEntry selectedEntry;
         private bool suppressPreview;
 
-        public ShapeLibraryForm()
+        public ShapeLibraryForm(IEnumerable<string> existingDrawingNames = null)
         {
+            existingNames = existingDrawingNames != null
+                ? new HashSet<string>(existingDrawingNames, StringComparer.OrdinalIgnoreCase)
+                : new HashSet<string>(StringComparer.OrdinalIgnoreCase);
+
             InitializeComponent();
             DiscoverShapes();
             PopulateShapeList();
@@ -180,6 +185,43 @@ namespace OpenNest.Forms
 
                 y += 18;
 
+                Control editor;
+                if (prop.PropertyType == typeof(bool))
+                {
+                    var cb = new CheckBox
+                    {
+                        Location = new Point(parametersPanel.Padding.Left, y),
+                        AutoSize = true,
+                        Checked = sourceValues != null && (bool)prop.GetValue(sourceValues)
+                    };
+                    cb.CheckedChanged += (s, ev) => UpdatePreview();
+                    editor = cb;
+                }
+                else if (prop.PropertyType == typeof(string) && prop.Name == "PipeSize")
+                {
+                    var combo = new ComboBox
+                    {
+                        Location = new Point(parametersPanel.Padding.Left, y),
+                        Width = panelWidth,
+                        Anchor = AnchorStyles.Top | AnchorStyles.Left | AnchorStyles.Right,
+                        DropDownStyle = ComboBoxStyle.DropDownList
+                    };
+
+                    // Initial population: every entry; the filter runs on first UpdatePreview.
+                    foreach (var entry in PipeSizes.All)
+                        combo.Items.Add(entry.Label);
+
+                    var initial = sourceValues != null ? (string)prop.GetValue(sourceValues) : null;
+                    if (!string.IsNullOrEmpty(initial) && combo.Items.Contains(initial))
+                        combo.SelectedItem = initial;
+                    else if (combo.Items.Count > 0)
+                        combo.SelectedIndex = 0;
+
+                    combo.SelectedIndexChanged += (s, ev) => UpdatePreview();
+                    editor = combo;
+                }
+                else
+                {
                     var tb = new TextBox
                     {
                         Location = new Point(parametersPanel.Padding.Left, y),
@@ -196,11 +238,13 @@ namespace OpenNest.Forms
                     }
 
                     tb.TextChanged += (s, ev) => UpdatePreview();
+                    editor = tb;
+                }
 
-                parameterBindings.Add(new ParameterBinding { Property = prop, Control = tb });
+                parameterBindings.Add(new ParameterBinding { Property = prop, Control = editor });
 
                 parametersPanel.Controls.Add(label);
-                parametersPanel.Controls.Add(tb);
+                parametersPanel.Controls.Add(editor);
 
                 y += 30;
             }
@@ -212,20 +256,31 @@ namespace OpenNest.Forms
         {
             if (suppressPreview || selectedEntry == null) return;
 
+            UpdatePipeSizeFilter();
+
             try
             {
                 var shape = CreateShapeFromInputs();
                 if (shape == null) return;
 
                 var drawing = shape.GetDrawing();
+                nameTextBox.Text = shape.GenerateName();
                 previewBox.ShowDrawing(drawing);
 
                 if (drawing?.Program != null)
                 {
                     var bb = drawing.Program.BoundingBox();
-                    previewBox.SetInfo(
+                    var info = string.Format("{0:F3} x {1:F3}", bb.Size.Length, bb.Size.Width);
-                        nameTextBox.Text,
+
-                        string.Format("{0:F3} x {1:F3}", bb.Size.Length, bb.Size.Width));
+                    if (shape is PipeFlangeShape flange
+                        && !flange.Blind
+                        && !string.IsNullOrEmpty(flange.PipeSize)
+                        && !PipeSizes.TryGetOD(flange.PipeSize, out _))
+                    {
+                        info += "  — Invalid pipe size, no bore cut";
+                    }
+
+                    previewBox.SetInfo(nameTextBox.Text, info);
                 }
             }
             catch
@@ -234,6 +289,72 @@ namespace OpenNest.Forms
             }
         }
 
+        private void UpdatePipeSizeFilter()
+        {
+            // Find the PipeSize combo and the numeric inputs it depends on.
+            ComboBox pipeCombo = null;
+            double holePattern = 0, holeDia = 0, clearance = 0;
+            bool blind = false;
+
+            foreach (var binding in parameterBindings)
+            {
+                var name = binding.Property.Name;
+                if (name == "PipeSize" && binding.Control is ComboBox cb)
+                    pipeCombo = cb;
+                else if (name == "HolePatternDiameter" && binding.Control is TextBox tb1)
+                    double.TryParse(tb1.Text, out holePattern);
+                else if (name == "HoleDiameter" && binding.Control is TextBox tb2)
+                    double.TryParse(tb2.Text, out holeDia);
+                else if (name == "PipeClearance" && binding.Control is TextBox tb3)
+                    double.TryParse(tb3.Text, out clearance);
+                else if (name == "Blind" && binding.Control is CheckBox chk)
+                    blind = chk.Checked;
+            }
+
+            if (pipeCombo == null)
+                return;
+
+            // Disable when blind, but keep visible with the selection preserved.
+            pipeCombo.Enabled = !blind;
+
+            // Compute filter: pipeOD + clearance < HolePatternDiameter - HoleDiameter.
+            var maxPipeOD = holePattern - holeDia - clearance;
+            var fittingLabels = PipeSizes.GetFittingSizes(maxPipeOD).Select(e => e.Label).ToList();
+
+            // Sequence-equal on existing items — no-op if unchanged (avoids flicker).
+            var currentLabels = pipeCombo.Items.Cast<string>().ToList();
+            if (currentLabels.SequenceEqual(fittingLabels))
+                return;
+
+            var previousSelection = pipeCombo.SelectedItem as string;
+
+            pipeCombo.BeginUpdate();
+            try
+            {
+                pipeCombo.Items.Clear();
+                foreach (var label in fittingLabels)
+                    pipeCombo.Items.Add(label);
+
+                if (fittingLabels.Count == 0)
+                {
+                    // No pipe fits — leave unselected.
+                }
+                else if (previousSelection != null && fittingLabels.Contains(previousSelection))
+                {
+                    pipeCombo.SelectedItem = previousSelection;
+                }
+                else
+                {
+                    // Select the largest (last, since PipeSizes.All is sorted ascending).
+                    pipeCombo.SelectedIndex = fittingLabels.Count - 1;
+                }
+            }
+            finally
+            {
+                pipeCombo.EndUpdate();
+            }
+        }
+
         private ShapeDefinition CreateShapeFromInputs()
         {
             var shape = (ShapeDefinition)Activator.CreateInstance(selectedEntry.ShapeType);
@@ -241,6 +362,19 @@ namespace OpenNest.Forms
 
             foreach (var binding in parameterBindings)
             {
+                if (binding.Property.PropertyType == typeof(bool))
+                {
+                    var cb = (CheckBox)binding.Control;
+                    binding.Property.SetValue(shape, cb.Checked);
+                    continue;
+                }
+
+                if (binding.Control is ComboBox combo)
+                {
+                    binding.Property.SetValue(shape, combo.SelectedItem?.ToString());
+                    continue;
+                }
+
                 var tb = (TextBox)binding.Control;
 
                 if (binding.Property.PropertyType == typeof(int))
@@ -277,10 +411,12 @@ namespace OpenNest.Forms
                 if (shape == null) return;
 
                 var drawing = shape.GetDrawing();
+                drawing.Name = GetUniqueName(drawing.Name);
                 drawing.Color = Drawing.GetNextColor();
                 drawing.Quantity.Required = (int)quantityUpDown.Value;
 
                 addedDrawings.Add(drawing);
+                existingNames.Add(drawing.Name);
                 DialogResult = DialogResult.OK;
 
                 addButton.Text = $"Added ({addedDrawings.Count})";
@@ -295,6 +431,19 @@ namespace OpenNest.Forms
             }
         }
 
+        private string GetUniqueName(string baseName)
+        {
+            if (!existingNames.Contains(baseName))
+                return baseName;
+
+            for (var i = 2; ; i++)
+            {
+                var candidate = $"{baseName} ({i})";
+                if (!existingNames.Contains(candidate))
+                    return candidate;
+            }
+        }
+
         private static string FriendlyName(string name)
         {
             if (name.EndsWith("Shape"))

OpenNest/GraphicsHelper.cs

@@ -138,9 +138,20 @@ namespace OpenNest
                         break;
 
                     case CodeType.RapidMove:
+                        {
+                            var rapid = (RapidMove)code;
+                            var endpt = rapid.EndPoint;
+                            if (mode == Mode.Incremental)
+                                endpt += curpos;
+                            var dx = endpt.X - curpos.X;
+                            var dy = endpt.Y - curpos.Y;
+                            if (dx * dx + dy * dy > 0.001 * 0.001)
+                            {
                                 cutPath.StartFigure();
                                 leadPath.StartFigure();
-                        AddLine(cutPath, (RapidMove)code, mode, ref curpos);
+                            }
+                            curpos = endpt;
+                        }
                         break;
 
                     case CodeType.SubProgramCall:
@@ -300,8 +311,17 @@ namespace OpenNest
                         break;
 
                     case CodeType.RapidMove:
+                        {
+                            var rapid = (RapidMove)code;
+                            var endpt = rapid.EndPoint;
+                            if (mode == Mode.Incremental)
+                                endpt += curpos;
+                            var dx = endpt.X - curpos.X;
+                            var dy = endpt.Y - curpos.Y;
+                            if (dx * dx + dy * dy > 0.001 * 0.001)
                                 Flush();
-                        AddLine(path, (RapidMove)code, mode, ref curpos);
+                            curpos = endpt;
+                        }
                         break;
 
                     case CodeType.SubProgramCall: