feat: add material library resolution, assist gas support, and UI fixes

- Add MaterialLibraryResolver for Cincinnati post processor to resolve
  G89 library files from material/thickness/gas configuration
- Add Nest.AssistGas property with serialization support in nest format
- Add etch library support with separate gas configuration
- Fix CutOff tests to match AwayFromOrigin default cut direction
- Fix plate info label not updating after ResizePlateToFitParts
- Add cutoff and remnants toolbar button icons

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

OpenNest.Console/Program.cs

@@ -7,6 +7,7 @@ using System.Collections.Generic;
 using System.Diagnostics;
 using System.IO;
 using System.Linq;
+using System.Reflection;
 using System.Threading;
 
 return NestConsole.Run(args);
@@ -20,6 +21,12 @@ static class NestConsole
         if (options == null)
             return 0; // --help was requested
 
+        if (options.ListPosts)
+        {
+            ListPostProcessors(options);
+            return 0;
+        }
+
         if (options.InputFiles.Count == 0)
         {
             PrintUsage();
@@ -68,6 +75,7 @@ static class NestConsole
 
         PrintResults(success, plate, elapsed);
         Save(nest, options);
+        PostProcess(nest, options);
 
         return options.CheckOverlaps && overlapCount > 0 ? 1 : 0;
     }
@@ -120,6 +128,18 @@ static class NestConsole
                 case "--engine" when i + 1 < args.Length:
                     NestEngineRegistry.ActiveEngineName = args[++i];
                     break;
+                case "--post" when i + 1 < args.Length:
+                    o.PostName = args[++i];
+                    break;
+                case "--post-output" when i + 1 < args.Length:
+                    o.PostOutput = args[++i];
+                    break;
+                case "--posts-dir" when i + 1 < args.Length:
+                    o.PostsDir = args[++i];
+                    break;
+                case "--list-posts":
+                    o.ListPosts = true;
+                    break;
                 case "--help":
                 case "-h":
                     PrintUsage();
@@ -382,6 +402,100 @@ static class NestConsole
         Console.WriteLine($"Saved: {outputFile}");
     }
 
+    static string ResolvePostsDir(Options options)
+    {
+        if (options.PostsDir != null)
+            return options.PostsDir;
+
+        var exePath = Assembly.GetEntryAssembly()?.Location
+                      ?? typeof(NestConsole).Assembly.Location;
+        return Path.Combine(Path.GetDirectoryName(exePath), "Posts");
+    }
+
+    static List<IPostProcessor> LoadPostProcessors(string postsDir)
+    {
+        var processors = new List<IPostProcessor>();
+
+        if (!Directory.Exists(postsDir))
+            return processors;
+
+        foreach (var file in Directory.GetFiles(postsDir, "*.dll"))
+        {
+            try
+            {
+                var assembly = Assembly.LoadFrom(file);
+
+                foreach (var type in assembly.GetTypes())
+                {
+                    if (!typeof(IPostProcessor).IsAssignableFrom(type) || type.IsInterface || type.IsAbstract)
+                        continue;
+
+                    if (Activator.CreateInstance(type) is IPostProcessor processor)
+                        processors.Add(processor);
+                }
+            }
+            catch (Exception ex)
+            {
+                Console.Error.WriteLine($"Warning: failed to load post processor from {Path.GetFileName(file)}: {ex.Message}");
+            }
+        }
+
+        return processors;
+    }
+
+    static void ListPostProcessors(Options options)
+    {
+        var postsDir = ResolvePostsDir(options);
+        var processors = LoadPostProcessors(postsDir);
+
+        if (processors.Count == 0)
+        {
+            Console.WriteLine($"No post processors found in: {postsDir}");
+            return;
+        }
+
+        Console.WriteLine($"Post processors ({postsDir}):");
+
+        foreach (var p in processors)
+            Console.WriteLine($"  {p.Name,-30} {p.Description}");
+    }
+
+    static void PostProcess(Nest nest, Options options)
+    {
+        if (options.PostName == null)
+            return;
+
+        var postsDir = ResolvePostsDir(options);
+        var processors = LoadPostProcessors(postsDir);
+        var post = processors.FirstOrDefault(p =>
+            p.Name.Equals(options.PostName, StringComparison.OrdinalIgnoreCase));
+
+        if (post == null)
+        {
+            Console.Error.WriteLine($"Error: post processor '{options.PostName}' not found");
+
+            if (processors.Count > 0)
+                Console.Error.WriteLine($"Available: {string.Join(", ", processors.Select(p => p.Name))}");
+            else
+                Console.Error.WriteLine($"No post processors found in: {postsDir}");
+
+            return;
+        }
+
+        var outputFile = options.PostOutput;
+
+        if (outputFile == null)
+        {
+            var firstInput = options.InputFiles[0];
+            outputFile = Path.Combine(
+                Path.GetDirectoryName(firstInput),
+                $"{Path.GetFileNameWithoutExtension(firstInput)}.cnc");
+        }
+
+        post.Post(nest, outputFile);
+        Console.WriteLine($"Post: {post.Name} -> {outputFile}");
+    }
+
     static void PrintUsage()
     {
         Console.Error.WriteLine("Usage: OpenNest.Console <input-files...> [options]");
@@ -407,6 +521,10 @@ static class NestConsole
         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/)");
+        Console.Error.WriteLine("  --list-posts           List available post processors and exit");
         Console.Error.WriteLine("  -h, --help             Show this help");
     }
 
@@ -425,5 +543,9 @@ static class NestConsole
         public bool KeepParts;
         public bool AutoNest;
         public string TemplateFile;
+        public string PostName;
+        public string PostOutput;
+        public string PostsDir;
+        public bool ListPosts;
     }
 }

OpenNest.Core/Nest.cs

@@ -36,6 +36,8 @@ namespace OpenNest
 
         public string Notes { get; set; }
 
+        public string AssistGas { get; set; } = "";
+
         public Units Units { get; set; }
 
         public DateTime DateCreated { get; set; }

OpenNest.Engine/BestFit/PolygonHelper.cs

@@ -23,9 +23,17 @@ namespace OpenNest.Engine.BestFit
                 return new PolygonExtractionResult(null, Vector.Zero);
 
             // Inflate by half-spacing if spacing is non-zero.
-            // OffsetSide.Right = outward for CCW perimeters (standard for outer contours).
+            // Detect winding direction to choose the correct outward offset side.
+            var outwardSide = OffsetSide.Right;
+            if (halfSpacing > 0)
+            {
+                var testPoly = perimeter.ToPolygon();
+                if (testPoly.Vertices.Count >= 3 && testPoly.RotationDirection() == RotationType.CW)
+                    outwardSide = OffsetSide.Left;
+            }
+
             var inflated = halfSpacing > 0
-                ? (perimeter.OffsetEntity(halfSpacing, OffsetSide.Right) as Shape ?? perimeter)
+                ? (perimeter.OffsetEntity(halfSpacing, outwardSide) as Shape ?? perimeter)
                 : perimeter;
 
             // Convert to polygon with circumscribed arcs for tight nesting.

OpenNest.IO/NestFormat.cs

@@ -23,6 +23,7 @@ namespace OpenNest.IO
             public string DateCreated { get; init; } = "";
             public string DateLastModified { get; init; } = "";
             public string Notes { get; init; } = "";
+            public string AssistGas { get; init; } = "";
             public PlateDefaultsDto PlateDefaults { get; init; } = new();
             public List<DrawingDto> Drawings { get; init; } = new();
             public List<PlateDto> Plates { get; init; } = new();

OpenNest.IO/NestReader.cs

@@ -160,6 +160,7 @@ namespace OpenNest.IO
             nest.DateCreated = DateTime.Parse(dto.DateCreated);
             nest.DateLastModified = DateTime.Parse(dto.DateLastModified);
             nest.Notes = dto.Notes;
+            nest.AssistGas = dto.AssistGas ?? "";
 
             // Plate defaults
             var pd = dto.PlateDefaults;

OpenNest.IO/NestWriter.cs

@@ -77,6 +77,7 @@ namespace OpenNest.IO
                 DateCreated = nest.DateCreated.ToString("o"),
                 DateLastModified = nest.DateLastModified.ToString("o"),
                 Notes = nest.Notes ?? "",
+                AssistGas = nest.AssistGas ?? "",
                 PlateDefaults = BuildPlateDefaultsDto(),
                 Drawings = BuildDrawingDtos(),
                 Plates = BuildPlateDtos()

OpenNest.Mcp/Tools/InputTools.cs

@@ -57,6 +57,35 @@ namespace OpenNest.Mcp.Tools
             return sb.ToString();
         }
 
+        [McpServerTool(Name = "save_nest")]
+        [Description("Save the current session (all drawings and plates) to a .nest file.")]
+        public string SaveNest(
+            [Description("Absolute path for the output .nest file")] string path,
+            [Description("Name for the nest (optional)")] string name = null)
+        {
+            var nest = new Nest();
+            nest.Name = name ?? Path.GetFileNameWithoutExtension(path);
+
+            foreach (var drawing in _session.AllDrawings())
+                nest.Drawings.Add(drawing);
+
+            foreach (var plate in _session.AllPlates())
+                nest.Plates.Add(plate);
+
+            if (nest.Drawings.Count == 0)
+                return "Error: no drawings in session to save";
+
+            var dir = Path.GetDirectoryName(path);
+            if (!string.IsNullOrEmpty(dir) && !Directory.Exists(dir))
+                Directory.CreateDirectory(dir);
+
+            var writer = new NestWriter(nest);
+            if (!writer.Write(path))
+                return "Error: failed to write nest file";
+
+            return $"Saved nest to {path}\n  Drawings: {nest.Drawings.Count}\n  Plates: {nest.Plates.Count}";
+        }
+
         [McpServerTool(Name = "import_dxf")]
         [Description("Import a DXF file as a new drawing. Returns drawing name and bounding box.")]
         public string ImportDxf(

OpenNest.Posts.Cincinnati/CincinnatiFeatureWriter.cs

@@ -19,6 +19,7 @@ public sealed class FeatureContext
     public bool IsLastFeatureOnSheet { get; set; }
     public bool IsSafetyHeadraise { get; set; }
     public bool IsExteriorFeature { get; set; }
+    public bool IsEtch { get; set; }
     public string LibraryFile { get; set; } = "";
     public double CutDistance { get; set; }
     public double SheetDiagonal { get; set; }
@@ -61,17 +62,24 @@ public sealed class CincinnatiFeatureWriter
         if (ctx.IsFirstFeatureOfPart && !string.IsNullOrEmpty(ctx.PartName))
             writer.WriteLine(CoordinateFormatter.Comment($"PART: {ctx.PartName}"));
 
-        // 3. G89 process params (if RepeatG89BeforeEachFeature)
-        if (_config.RepeatG89BeforeEachFeature && _config.ProcessParameterMode == G89Mode.LibraryFile)
+        // 3. G89 process params
+        if (_config.ProcessParameterMode == G89Mode.LibraryFile)
         {
-            var lib = !string.IsNullOrEmpty(ctx.LibraryFile) ? ctx.LibraryFile : _config.DefaultLibraryFile;
-            var speedClass = _speedClassifier.Classify(ctx.CutDistance, ctx.SheetDiagonal);
-            var cutDist = _speedClassifier.FormatCutDist(ctx.CutDistance, ctx.SheetDiagonal);
-            writer.WriteLine($"G89 P {lib} ({speedClass} {cutDist})");
+            var lib = ctx.LibraryFile;
+            if (!string.IsNullOrEmpty(lib))
+            {
+                var speedClass = _speedClassifier.Classify(ctx.CutDistance, ctx.SheetDiagonal);
+                var cutDist = _speedClassifier.FormatCutDist(ctx.CutDistance, ctx.SheetDiagonal);
+                writer.WriteLine($"G89 P {lib} ({speedClass} {cutDist})");
+            }
+            else
+            {
+                writer.WriteLine("(WARNING: No library found)");
+            }
         }
 
-        // 4. Pierce and start cut
-        writer.WriteLine("G84");
+        // 4. Pierce/beam on — G85 for etch (no pierce), G84 for cut
+        writer.WriteLine(ctx.IsEtch ? "G85" : "G84");
 
         // 5. Anti-dive off
         if (_config.UseAntiDive)
@@ -90,20 +98,20 @@ public sealed class CincinnatiFeatureWriter
             {
                 var sb = new StringBuilder();
 
-                // Kerf compensation on first cutting move
-                if (!kerfEmitted && _config.KerfCompensation == KerfMode.ControllerSide)
+                // Kerf compensation on first cutting move (skip for etch)
+                if (!ctx.IsEtch && !kerfEmitted && _config.KerfCompensation == KerfMode.ControllerSide)
                 {
-                    sb.Append(_config.DefaultKerfSide == KerfSide.Left ? "G41" : "G42");
+                    sb.Append(_config.DefaultKerfSide == KerfSide.Left ? "G41 " : "G42 ");
                     kerfEmitted = true;
                 }
 
-                sb.Append($"G1X{_fmt.FormatCoord(linear.EndPoint.X)}Y{_fmt.FormatCoord(linear.EndPoint.Y)}");
+                sb.Append($"G1 X{_fmt.FormatCoord(linear.EndPoint.X)} Y{_fmt.FormatCoord(linear.EndPoint.Y)}");
 
-                // Feedrate
-                var feedVar = GetFeedVariable(linear.Layer);
+                // Feedrate — etch always uses process feedrate
+                var feedVar = ctx.IsEtch ? "#148" : GetFeedVariable(linear.Layer);
                 if (feedVar != lastFeedVar)
                 {
-                    sb.Append($"F{feedVar}");
+                    sb.Append($" F{feedVar}");
                     lastFeedVar = feedVar;
                 }
 
@@ -114,28 +122,30 @@ public sealed class CincinnatiFeatureWriter
             {
                 var sb = new StringBuilder();
 
-                // Kerf compensation on first cutting move
-                if (!kerfEmitted && _config.KerfCompensation == KerfMode.ControllerSide)
+                // Kerf compensation on first cutting move (skip for etch)
+                if (!ctx.IsEtch && !kerfEmitted && _config.KerfCompensation == KerfMode.ControllerSide)
                 {
-                    sb.Append(_config.DefaultKerfSide == KerfSide.Left ? "G41" : "G42");
+                    sb.Append(_config.DefaultKerfSide == KerfSide.Left ? "G41 " : "G42 ");
                     kerfEmitted = true;
                 }
 
                 // G2 = CW, G3 = CCW
                 var gCode = arc.Rotation == RotationType.CW ? "G2" : "G3";
-                sb.Append($"{gCode}X{_fmt.FormatCoord(arc.EndPoint.X)}Y{_fmt.FormatCoord(arc.EndPoint.Y)}");
+                sb.Append($"{gCode} X{_fmt.FormatCoord(arc.EndPoint.X)} Y{_fmt.FormatCoord(arc.EndPoint.Y)}");
 
                 // Convert absolute center to incremental I/J
                 var i = arc.CenterPoint.X - currentPos.X;
                 var j = arc.CenterPoint.Y - currentPos.Y;
-                sb.Append($"I{_fmt.FormatCoord(i)}J{_fmt.FormatCoord(j)}");
+                sb.Append($" I{_fmt.FormatCoord(i)} J{_fmt.FormatCoord(j)}");
 
-                // Feedrate — full circles use multiplied feedrate
+                // Feedrate — etch always uses process feedrate, cut uses layer-based
                 var isFullCircle = IsFullCircle(currentPos, arc.EndPoint);
-                var feedVar = isFullCircle ? "[#148*#128]" : GetFeedVariable(arc.Layer);
+                var feedVar = ctx.IsEtch ? "#148"
+                    : isFullCircle ? "[#148*#128]"
+                    : GetFeedVariable(arc.Layer);
                 if (feedVar != lastFeedVar)
                 {
-                    sb.Append($"F{feedVar}");
+                    sb.Append($" F{feedVar}");
                     lastFeedVar = feedVar;
                 }
 
@@ -183,9 +193,9 @@ public sealed class CincinnatiFeatureWriter
         var sb = new StringBuilder();
 
         if (_config.UseLineNumbers)
-            sb.Append($"N{featureNumber}");
+            sb.Append($"N{featureNumber} ");
 
-        sb.Append($"G0X{_fmt.FormatCoord(piercePoint.X)}Y{_fmt.FormatCoord(piercePoint.Y)}");
+        sb.Append($"G0 X{_fmt.FormatCoord(piercePoint.X)} Y{_fmt.FormatCoord(piercePoint.Y)}");
 
         writer.WriteLine(sb.ToString());
     }
@@ -194,7 +204,7 @@ public sealed class CincinnatiFeatureWriter
     {
         if (ctx.IsSafetyHeadraise && _config.SafetyHeadraiseDistance.HasValue)
         {
-            writer.WriteLine($"M47 P{_config.SafetyHeadraiseDistance.Value}(Safety Headraise)");
+            writer.WriteLine($"M47 P{_config.SafetyHeadraiseDistance.Value} (Safety Headraise)");
             return;
         }
 

OpenNest.Posts.Cincinnati/CincinnatiPartSubprogramWriter.cs

@@ -27,19 +27,22 @@ public sealed class CincinnatiPartSubprogramWriter
     /// The program coordinates must already be normalized to origin (0,0).
     /// </summary>
     public void Write(TextWriter w, Program normalizedProgram, string drawingName,
-        int subNumber, string libraryFile, double sheetDiagonal)
+        int subNumber, string cutLibrary, string etchLibrary, double sheetDiagonal)
     {
-        var features = SplitFeatures(normalizedProgram.Codes);
-        if (features.Count == 0)
+        var allFeatures = SplitFeatures(normalizedProgram.Codes);
+        if (allFeatures.Count == 0)
             return;
 
+        // Classify and order: etch features first, then cut features
+        var ordered = OrderFeatures(allFeatures);
+
         w.WriteLine("(*****************************************************)");
         w.WriteLine($":{subNumber}");
         w.WriteLine(CoordinateFormatter.Comment($"PART: {drawingName}"));
 
-        for (var i = 0; i < features.Count; i++)
+        for (var i = 0; i < ordered.Count; i++)
         {
-            var codes = features[i];
+            var (codes, isEtch) = ordered[i];
             var featureNumber = i == 0
                 ? _config.FeatureLineNumberStart
                 : 1000 + i + 1;
@@ -51,10 +54,11 @@ public sealed class CincinnatiPartSubprogramWriter
                 FeatureNumber = featureNumber,
                 PartName = drawingName,
                 IsFirstFeatureOfPart = false,
-                IsLastFeatureOnSheet = i == features.Count - 1,
+                IsLastFeatureOnSheet = i == ordered.Count - 1,
                 IsSafetyHeadraise = false,
                 IsExteriorFeature = false,
-                LibraryFile = libraryFile,
+                IsEtch = isEtch,
+                LibraryFile = isEtch ? etchLibrary : cutLibrary,
                 CutDistance = cutDistance,
                 SheetDiagonal = sheetDiagonal
             };
@@ -62,8 +66,30 @@ public sealed class CincinnatiPartSubprogramWriter
             _featureWriter.Write(w, ctx);
         }
 
-        w.WriteLine("G0X0Y0");
-        w.WriteLine($"M99(END OF {drawingName})");
+        w.WriteLine("G0 X0 Y0");
+        w.WriteLine($"M99 (END OF {drawingName})");
+    }
+
+    internal static List<(List<ICode> codes, bool isEtch)> OrderFeatures(List<List<ICode>> features)
+    {
+        var result = new List<(List<ICode>, bool)>();
+        var etch = new List<List<ICode>>();
+        var cut = new List<List<ICode>>();
+
+        foreach (var f in features)
+        {
+            if (CincinnatiSheetWriter.IsFeatureEtch(f))
+                etch.Add(f);
+            else
+                cut.Add(f);
+        }
+
+        foreach (var f in etch)
+            result.Add((f, true));
+        foreach (var f in cut)
+            result.Add((f, false));
+
+        return result;
     }
 
     /// <summary>

OpenNest.Posts.Cincinnati/CincinnatiPostConfig.cs

@@ -1,3 +1,5 @@
+using System.Collections.Generic;
+
 namespace OpenNest.Posts.Cincinnati
 {
     /// <summary>
@@ -153,16 +155,29 @@ namespace OpenNest.Posts.Cincinnati
         public G89Mode ProcessParameterMode { get; set; } = G89Mode.LibraryFile;
 
         /// <summary>
-        /// Gets or sets the default G89 library file path.
-        /// Default: empty string
+        /// Gets or sets the default assist gas when Nest.AssistGas is empty.
+        /// Default: "O2"
         /// </summary>
-        public string DefaultLibraryFile { get; set; } = "";
+        public string DefaultAssistGas { get; set; } = "O2";
 
         /// <summary>
-        /// Gets or sets whether to repeat G89 before each feature.
-        /// Default: true
+        /// Gets or sets the gas used for etch operations.
+        /// Independent of the cutting assist gas — etch typically requires a specific gas.
+        /// Default: "N2"
         /// </summary>
-        public bool RepeatG89BeforeEachFeature { get; set; } = true;
+        public string DefaultEtchGas { get; set; } = "N2";
+
+        /// <summary>
+        /// Gets or sets the material-to-library mapping for cut operations.
+        /// Each entry maps (material, thickness, gas) to a G89 library file.
+        /// </summary>
+        public List<MaterialLibraryEntry> MaterialLibraries { get; set; } = new();
+
+        /// <summary>
+        /// Gets or sets the gas-to-library mapping for etch operations.
+        /// Each entry maps a gas type to a G89 etch library file.
+        /// </summary>
+        public List<EtchLibraryEntry> EtchLibraries { get; set; } = new();
 
         /// <summary>
         /// Gets or sets whether to use exact stop mode (G61).
@@ -272,4 +287,18 @@ namespace OpenNest.Posts.Cincinnati
         /// </summary>
         public int SheetLengthVariable { get; set; } = 111;
     }
+
+    public class MaterialLibraryEntry
+    {
+        public string Material { get; set; } = "";
+        public double Thickness { get; set; }
+        public string Gas { get; set; } = "";
+        public string Library { get; set; } = "";
+    }
+
+    public class EtchLibraryEntry
+    {
+        public string Gas { get; set; } = "";
+        public string Library { get; set; } = "";
+    }
 }

OpenNest.Posts.Cincinnati/CincinnatiPostProcessor.cs

@@ -68,7 +68,18 @@ namespace OpenNest.Posts.Cincinnati
                 .Where(p => p.Parts.Count > 0)
                 .ToList();
 
-            // 3. Build part sub-program registry (if enabled)
+            // 3. Resolve gas and library files
+            var resolver = new MaterialLibraryResolver(Config);
+            var gas = MaterialLibraryResolver.ResolveGas(nest, Config);
+            var etchLibrary = resolver.ResolveEtchLibrary(Config.DefaultEtchGas);
+
+            // Resolve cut library from first plate for preamble
+            var firstPlate = plates.FirstOrDefault();
+            var initialCutLibrary = firstPlate != null
+                ? resolver.ResolveCutLibrary(firstPlate.Material?.Name ?? "", firstPlate.Thickness, gas)
+                : "";
+
+            // 4. Build part sub-program registry (if enabled)
             Dictionary<(int, long), int> partSubprograms = null;
             List<(int subNum, string name, Program program)> subprogramEntries = null;
 
@@ -100,21 +111,21 @@ namespace OpenNest.Posts.Cincinnati
                 }
             }
 
-            // 4. Create writers
+            // 5. Create writers
             var preamble = new CincinnatiPreambleWriter(Config);
             var sheetWriter = new CincinnatiSheetWriter(Config, vars);
 
-            // 5. Build material description from first plate
-            var material = plates.FirstOrDefault()?.Material;
+            // 6. Build material description from first plate
+            var material = firstPlate?.Material;
             var materialDesc = material != null
                 ? $"{material.Name}{(string.IsNullOrEmpty(material.Grade) ? "" : $", {material.Grade}")}"
                 : "";
 
-            // 6. Write to stream
+            // 7. Write to stream
             using var writer = new StreamWriter(outputStream, Encoding.UTF8, 1024, leaveOpen: true);
 
             // Main program
-            preamble.WriteMainProgram(writer, nest.Name ?? "NEST", materialDesc, plates.Count);
+            preamble.WriteMainProgram(writer, nest.Name ?? "NEST", materialDesc, plates.Count, initialCutLibrary);
 
             // Variable declaration subprogram
             preamble.WriteVariableDeclaration(writer, vars);
@@ -122,17 +133,18 @@ namespace OpenNest.Posts.Cincinnati
             // Sheet subprograms
             for (var i = 0; i < plates.Count; i++)
             {
+                var plate = plates[i];
                 var sheetIndex = i + 1;
                 var subNumber = Config.SheetSubprogramStart + i;
-                sheetWriter.Write(writer, plates[i], nest.Name ?? "NEST", sheetIndex, subNumber,
-                    partSubprograms);
+                var cutLibrary = resolver.ResolveCutLibrary(plate.Material?.Name ?? "", plate.Thickness, gas);
+                sheetWriter.Write(writer, plate, nest.Name ?? "NEST", sheetIndex, subNumber,
+                    cutLibrary, etchLibrary, partSubprograms);
             }
 
             // Part sub-programs (if enabled)
             if (subprogramEntries != null)
             {
                 var partSubWriter = new CincinnatiPartSubprogramWriter(Config);
-                var firstPlate = plates.FirstOrDefault();
                 var sheetDiagonal = firstPlate != null
                     ? System.Math.Sqrt(firstPlate.Size.Width * firstPlate.Size.Width
                         + firstPlate.Size.Length * firstPlate.Size.Length)
@@ -141,7 +153,7 @@ namespace OpenNest.Posts.Cincinnati
                 foreach (var (subNum, name, pgm) in subprogramEntries)
                 {
                     partSubWriter.Write(writer, pgm, name, subNum,
-                        Config.DefaultLibraryFile ?? "", sheetDiagonal);
+                        initialCutLibrary, etchLibrary, sheetDiagonal);
                 }
             }
 

OpenNest.Posts.Cincinnati/CincinnatiPreambleWriter.cs

@@ -21,7 +21,9 @@ public sealed class CincinnatiPreambleWriter
     /// <summary>
     /// Writes the main program header block.
     /// </summary>
-    public void WriteMainProgram(TextWriter w, string nestName, string materialDescription, int sheetCount)
+    /// <param name="initialLibrary">Resolved G89 library file for the initial process setup.</param>
+    public void WriteMainProgram(TextWriter w, string nestName, string materialDescription,
+        int sheetCount, string initialLibrary)
     {
         w.WriteLine(CoordinateFormatter.Comment($"NEST {nestName}"));
         w.WriteLine(CoordinateFormatter.Comment($"CONFIGURATION - {_config.ConfigurationName}"));
@@ -39,8 +41,8 @@ public sealed class CincinnatiPreambleWriter
 
         w.WriteLine("M42");
 
-        if (_config.ProcessParameterMode == G89Mode.LibraryFile && !string.IsNullOrEmpty(_config.DefaultLibraryFile))
-            w.WriteLine($"G89 P {_config.DefaultLibraryFile}");
+        if (_config.ProcessParameterMode == G89Mode.LibraryFile && !string.IsNullOrEmpty(initialLibrary))
+            w.WriteLine($"G89 P {initialLibrary}");
 
         w.WriteLine($"M98 P{_config.VariableDeclarationSubprogram} (Variable Declaration)");
 
@@ -49,7 +51,7 @@ public sealed class CincinnatiPreambleWriter
         for (var i = 1; i <= sheetCount; i++)
         {
             var subNum = _config.SheetSubprogramStart + (i - 1);
-            w.WriteLine($"N{i}M98 P{subNum} (SHEET {i})");
+            w.WriteLine($"N{i} M98 P{subNum} (SHEET {i})");
         }
 
         w.WriteLine("M42");

OpenNest.Posts.Cincinnati/CincinnatiSheetWriter.cs

@@ -30,11 +30,14 @@ public sealed class CincinnatiSheetWriter
     /// <summary>
     /// Writes a complete sheet subprogram for the given plate.
     /// </summary>
+    /// <param name="cutLibrary">Resolved G89 library file for cut operations.</param>
+    /// <param name="etchLibrary">Resolved G89 library file for etch operations.</param>
     /// <param name="partSubprograms">
     /// Optional mapping of (drawingId, rotationKey) to sub-program number.
     /// When provided, non-cutoff parts are emitted as M98 calls instead of inline features.
     /// </param>
     public void Write(TextWriter w, Plate plate, string nestName, int sheetIndex, int subNumber,
+        string cutLibrary, string etchLibrary,
         Dictionary<(int, long), int> partSubprograms = null)
     {
         if (plate.Parts.Count == 0)
@@ -43,7 +46,6 @@ public sealed class CincinnatiSheetWriter
         var width = plate.Size.Width;
         var length = plate.Size.Length;
         var sheetDiagonal = System.Math.Sqrt(width * width + length * length);
-        var libraryFile = _config.DefaultLibraryFile ?? "";
         var varDeclSub = _config.VariableDeclarationSubprogram;
         var partCount = plate.Parts.Count(p => !p.BaseDrawing.IsCutOff);
 
@@ -55,20 +57,20 @@ public sealed class CincinnatiSheetWriter
         w.WriteLine($"( Layout {sheetIndex} )");
         w.WriteLine($"( SHEET NAME = {_fmt.FormatCoord(length)} X {_fmt.FormatCoord(width)} )");
         w.WriteLine($"( Total parts on sheet = {partCount} )");
-        w.WriteLine($"#{_config.SheetWidthVariable}={_fmt.FormatCoord(width)}(SHEET WIDTH FOR CUTOFFS)");
-        w.WriteLine($"#{_config.SheetLengthVariable}={_fmt.FormatCoord(length)}(SHEET LENGTH FOR CUTOFFS)");
+        w.WriteLine($"#{_config.SheetWidthVariable}={_fmt.FormatCoord(width)} (SHEET WIDTH FOR CUTOFFS)");
+        w.WriteLine($"#{_config.SheetLengthVariable}={_fmt.FormatCoord(length)} (SHEET LENGTH FOR CUTOFFS)");
 
         // 2. Coordinate setup
         w.WriteLine("M42");
         w.WriteLine("N10000");
-        w.WriteLine("G92X#5021Y#5022");
-        if (!string.IsNullOrEmpty(libraryFile))
-            w.WriteLine($"G89 P {libraryFile}");
+        w.WriteLine("G92 X#5021 Y#5022");
+        if (!string.IsNullOrEmpty(cutLibrary))
+            w.WriteLine($"G89 P {cutLibrary}");
         w.WriteLine($"M98 P{varDeclSub} (Variable Declaration)");
         w.WriteLine("G90");
-        w.WriteLine("M47(CPT)");
-        if (!string.IsNullOrEmpty(libraryFile))
-            w.WriteLine($"G89 P {libraryFile}");
+        w.WriteLine("M47");
+        if (!string.IsNullOrEmpty(cutLibrary))
+            w.WriteLine($"G89 P {cutLibrary}");
         w.WriteLine("GOTO1( Goto Feature )");
 
         // 3. Order parts: non-cutoff sorted by Bottom then Left, cutoffs last
@@ -86,20 +88,20 @@ public sealed class CincinnatiSheetWriter
 
         // 4. Emit parts
         if (partSubprograms != null)
-            WritePartsWithSubprograms(w, allParts, libraryFile, sheetDiagonal, partSubprograms);
+            WritePartsWithSubprograms(w, allParts, cutLibrary, etchLibrary, sheetDiagonal, partSubprograms);
         else
-            WritePartsInline(w, allParts, libraryFile, sheetDiagonal);
+            WritePartsInline(w, allParts, cutLibrary, etchLibrary, sheetDiagonal);
 
         // 5. Footer
         w.WriteLine("M42");
-        w.WriteLine("G0X0Y0");
+        w.WriteLine("G0 X0 Y0");
         if (_config.PalletExchange != PalletMode.None)
-            w.WriteLine($"N{sheetIndex + 1}M50");
-        w.WriteLine($"M99(END OF {nestName}.{sheetIndex:D3})");
+            w.WriteLine($"N{sheetIndex + 1} M50");
+        w.WriteLine($"M99 (END OF {nestName}.{sheetIndex:D3})");
     }
 
     private void WritePartsWithSubprograms(TextWriter w, List<Part> allParts,
-        string libraryFile, double sheetDiagonal,
+        string cutLibrary, string etchLibrary, double sheetDiagonal,
         Dictionary<(int, long), int> partSubprograms)
     {
         var lastPartName = "";
@@ -126,26 +128,28 @@ public sealed class CincinnatiSheetWriter
             else
             {
                 // Inline features for cutoffs or parts without sub-programs
-                var features = SplitPartFeatures(part);
+                var features = SplitAndOrderFeatures(part);
                 for (var f = 0; f < features.Count; f++)
                 {
+                    var (codes, isEtch) = features[f];
                     var featureNumber = featureIndex == 0
                         ? _config.FeatureLineNumberStart
                         : 1000 + featureIndex + 1;
 
                     var isLastFeature = isLastPart && f == features.Count - 1;
-                    var cutDistance = ComputeCutDistance(features[f]);
+                    var cutDistance = ComputeCutDistance(codes);
 
                     var ctx = new FeatureContext
                     {
-                        Codes = features[f],
+                        Codes = codes,
                         FeatureNumber = featureNumber,
                         PartName = partName,
                         IsFirstFeatureOfPart = isNewPart && f == 0,
                         IsLastFeatureOnSheet = isLastFeature,
                         IsSafetyHeadraise = isSafetyHeadraise && f == 0,
                         IsExteriorFeature = false,
-                        LibraryFile = libraryFile,
+                        IsEtch = isEtch,
+                        LibraryFile = isEtch ? etchLibrary : cutLibrary,
                         CutDistance = cutDistance,
                         SheetDiagonal = sheetDiagonal
                     };
@@ -164,7 +168,7 @@ public sealed class CincinnatiSheetWriter
     {
         // Safety headraise before rapid to new part
         if (isSafetyHeadraise && _config.SafetyHeadraiseDistance.HasValue)
-            w.WriteLine($"M47 P{_config.SafetyHeadraiseDistance.Value}(Safety Headraise)");
+            w.WriteLine($"M47 P{_config.SafetyHeadraiseDistance.Value} (Safety Headraise)");
 
         // Rapid to part position (bounding box lower-left)
         var featureNumber = featureIndex == 0
@@ -173,21 +177,21 @@ public sealed class CincinnatiSheetWriter
 
         var sb = new StringBuilder();
         if (_config.UseLineNumbers)
-            sb.Append($"N{featureNumber}");
-        sb.Append($"G0X{_fmt.FormatCoord(part.Left)}Y{_fmt.FormatCoord(part.Bottom)}");
+            sb.Append($"N{featureNumber} ");
+        sb.Append($"G0 X{_fmt.FormatCoord(part.Left)} Y{_fmt.FormatCoord(part.Bottom)}");
         w.WriteLine(sb.ToString());
 
         // Part name comment
         w.WriteLine(CoordinateFormatter.Comment($"PART: {partName}"));
 
         // Set local coordinate system at part position
-        w.WriteLine("G92X0Y0");
+        w.WriteLine("G92 X0 Y0");
 
         // Call part sub-program
-        w.WriteLine($"M98P{subNum}({partName})");
+        w.WriteLine($"M98 P{subNum} ({partName})");
 
         // Restore sheet coordinate system
-        w.WriteLine($"G92X{_fmt.FormatCoord(part.Left)}Y{_fmt.FormatCoord(part.Bottom)}");
+        w.WriteLine($"G92 X{_fmt.FormatCoord(part.Left)} Y{_fmt.FormatCoord(part.Bottom)}");
 
         // Head raise (unless last part on sheet)
         if (!isLastPart)
@@ -195,36 +199,22 @@ public sealed class CincinnatiSheetWriter
     }
 
     private void WritePartsInline(TextWriter w, List<Part> allParts,
-        string libraryFile, double sheetDiagonal)
+        string cutLibrary, string etchLibrary, double sheetDiagonal)
     {
-        // Multi-contour splitting
-        var features = new List<(Part part, List<ICode> codes)>();
+        // Split and classify features, ordering etch before cut per part
+        var features = new List<(Part part, List<ICode> codes, bool isEtch)>();
         foreach (var part in allParts)
         {
-            List<ICode> current = null;
-            foreach (var code in part.Program.Codes)
-            {
-                if (code is RapidMove)
-                {
-                    if (current != null)
-                        features.Add((part, current));
-                    current = new List<ICode> { code };
-                }
-                else
-                {
-                    current ??= new List<ICode>();
-                    current.Add(code);
-                }
-            }
-            if (current != null && current.Count > 0)
-                features.Add((part, current));
+            var partFeatures = SplitAndOrderFeatures(part);
+            foreach (var (codes, isEtch) in partFeatures)
+                features.Add((part, codes, isEtch));
         }
 
         // Emit features
         var lastPartName = "";
         for (var i = 0; i < features.Count; i++)
         {
-            var (part, codes) = features[i];
+            var (part, codes, isEtch) = features[i];
             var partName = part.BaseDrawing.Name;
             var isFirstFeatureOfPart = partName != lastPartName;
             var isSafetyHeadraise = partName != lastPartName && lastPartName != "";
@@ -245,7 +235,8 @@ public sealed class CincinnatiSheetWriter
                 IsLastFeatureOnSheet = isLastFeature,
                 IsSafetyHeadraise = isSafetyHeadraise,
                 IsExteriorFeature = false,
-                LibraryFile = libraryFile,
+                IsEtch = isEtch,
+                LibraryFile = isEtch ? etchLibrary : cutLibrary,
                 CutDistance = cutDistance,
                 SheetDiagonal = sheetDiagonal
             };
@@ -255,9 +246,14 @@ public sealed class CincinnatiSheetWriter
         }
     }
 
-    private static List<List<ICode>> SplitPartFeatures(Part part)
+    /// <summary>
+    /// Splits a part's program into features (by rapids), classifies each as etch or cut,
+    /// and orders etch features before cut features.
+    /// </summary>
+    public static List<(List<ICode> codes, bool isEtch)> SplitAndOrderFeatures(Part part)
     {
-        var features = new List<List<ICode>>();
+        var etchFeatures = new List<List<ICode>>();
+        var cutFeatures = new List<List<ICode>>();
         List<ICode> current = null;
 
         foreach (var code in part.Program.Codes)
@@ -265,7 +261,7 @@ public sealed class CincinnatiSheetWriter
             if (code is RapidMove)
             {
                 if (current != null)
-                    features.Add(current);
+                    ClassifyAndAdd(current, etchFeatures, cutFeatures);
                 current = new List<ICode> { code };
             }
             else
@@ -276,9 +272,40 @@ public sealed class CincinnatiSheetWriter
         }
 
         if (current != null && current.Count > 0)
-            features.Add(current);
+            ClassifyAndAdd(current, etchFeatures, cutFeatures);
 
-        return features;
+        // Etch features first, then cut features
+        var result = new List<(List<ICode>, bool)>();
+        foreach (var f in etchFeatures)
+            result.Add((f, true));
+        foreach (var f in cutFeatures)
+            result.Add((f, false));
+
+        return result;
+    }
+
+    private static void ClassifyAndAdd(List<ICode> codes,
+        List<List<ICode>> etchFeatures, List<List<ICode>> cutFeatures)
+    {
+        if (IsFeatureEtch(codes))
+            etchFeatures.Add(codes);
+        else
+            cutFeatures.Add(codes);
+    }
+
+    /// <summary>
+    /// A feature is etch if any non-rapid move has LayerType.Scribe.
+    /// </summary>
+    public static bool IsFeatureEtch(List<ICode> codes)
+    {
+        foreach (var code in codes)
+        {
+            if (code is LinearMove linear && linear.Layer == LayerType.Scribe)
+                return true;
+            if (code is ArcMove arc && arc.Layer == LayerType.Scribe)
+                return true;
+        }
+        return false;
     }
 
     private static double ComputeCutDistance(List<ICode> codes)

OpenNest.Posts.Cincinnati/MaterialLibraryResolver.cs

@@ -0,0 +1,42 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+
+namespace OpenNest.Posts.Cincinnati;
+
+public sealed class MaterialLibraryResolver
+{
+    private const double ThicknessTolerance = 0.001;
+
+    private readonly List<MaterialLibraryEntry> _materialLibraries;
+    private readonly List<EtchLibraryEntry> _etchLibraries;
+
+    public MaterialLibraryResolver(CincinnatiPostConfig config)
+    {
+        _materialLibraries = config.MaterialLibraries ?? new List<MaterialLibraryEntry>();
+        _etchLibraries = config.EtchLibraries ?? new List<EtchLibraryEntry>();
+    }
+
+    public string ResolveCutLibrary(string materialName, double thickness, string gas)
+    {
+        var entry = _materialLibraries.FirstOrDefault(e =>
+            string.Equals(e.Material, materialName, StringComparison.OrdinalIgnoreCase) &&
+            System.Math.Abs(e.Thickness - thickness) <= ThicknessTolerance &&
+            string.Equals(e.Gas, gas, StringComparison.OrdinalIgnoreCase));
+
+        return entry?.Library ?? "";
+    }
+
+    public string ResolveEtchLibrary(string gas)
+    {
+        var entry = _etchLibraries.FirstOrDefault(e =>
+            string.Equals(e.Gas, gas, StringComparison.OrdinalIgnoreCase));
+
+        return entry?.Library ?? "";
+    }
+
+    public static string ResolveGas(Nest nest, CincinnatiPostConfig config)
+    {
+        return !string.IsNullOrEmpty(nest.AssistGas) ? nest.AssistGas : config.DefaultAssistGas;
+    }
+}

OpenNest.Tests/Cincinnati/CincinnatiFeatureWriterTests.cs

@@ -13,9 +13,7 @@ public class CincinnatiFeatureWriterTests
         UseAntiDive = true,
         KerfCompensation = KerfMode.ControllerSide,
         DefaultKerfSide = KerfSide.Left,
-        RepeatG89BeforeEachFeature = true,
         ProcessParameterMode = G89Mode.LibraryFile,
-        DefaultLibraryFile = "MILD10",
         InteriorM47 = M47Mode.Always,
         ExteriorM47 = M47Mode.Always,
         UseSpeedGas = false,
@@ -58,7 +56,7 @@ public class CincinnatiFeatureWriterTests
         var output = WriteFeature(config, ctx);
         var lines = output.Split(Environment.NewLine, StringSplitOptions.RemoveEmptyEntries);
 
-        Assert.StartsWith("N1G0X13.401Y57.4895", lines[0]);
+        Assert.StartsWith("N1 G0 X13.401 Y57.4895", lines[0]);
     }
 
     [Fact]
@@ -70,7 +68,7 @@ public class CincinnatiFeatureWriterTests
         var output = WriteFeature(config, ctx);
         var lines = output.Split(Environment.NewLine, StringSplitOptions.RemoveEmptyEntries);
 
-        Assert.StartsWith("G0X13.401Y57.4895", lines[0]);
+        Assert.StartsWith("G0 X13.401 Y57.4895", lines[0]);
     }
 
     [Fact]
@@ -260,8 +258,8 @@ public class CincinnatiFeatureWriterTests
         var cwOutput = WriteFeature(config, SimpleContext(cwCodes));
         var ccwOutput = WriteFeature(config, SimpleContext(ccwCodes));
 
-        Assert.Contains("G2X", cwOutput);
-        Assert.Contains("G3X", ccwOutput);
+        Assert.Contains("G2 X", cwOutput);
+        Assert.Contains("G3 X", ccwOutput);
     }
 
     [Fact]
@@ -289,12 +287,10 @@ public class CincinnatiFeatureWriterTests
     }
 
     [Fact]
-    public void G89_EmittedWhenRepeatEnabled()
+    public void G89_EmittedWithLibraryFile()
     {
         var config = DefaultConfig();
-        config.RepeatG89BeforeEachFeature = true;
         config.ProcessParameterMode = G89Mode.LibraryFile;
-        config.DefaultLibraryFile = "MILD10";
         var ctx = SimpleContext();
         ctx.LibraryFile = "MILD10";
         ctx.CutDistance = 18.0;
@@ -305,14 +301,65 @@ public class CincinnatiFeatureWriterTests
     }
 
     [Fact]
-    public void G89_NotEmittedWhenRepeatDisabled()
+    public void G89_WarningEmittedWhenNoLibrary()
     {
         var config = DefaultConfig();
-        config.RepeatG89BeforeEachFeature = false;
+        config.ProcessParameterMode = G89Mode.LibraryFile;
         var ctx = SimpleContext();
+        ctx.LibraryFile = "";
         var output = WriteFeature(config, ctx);
 
-        Assert.DoesNotContain("G89", output);
+        Assert.Contains("WARNING: No library found", output);
+        Assert.DoesNotContain("G89 P", output);
+    }
+
+    [Fact]
+    public void Etch_UsesG85InsteadOfG84()
+    {
+        var config = DefaultConfig();
+        var ctx = SimpleContext();
+        ctx.IsEtch = true;
+        ctx.LibraryFile = "EtchN2.lib";
+        var output = WriteFeature(config, ctx);
+
+        Assert.Contains("G85", output);
+        Assert.DoesNotContain("G84", output);
+    }
+
+    [Fact]
+    public void Etch_SkipsKerfCompensation()
+    {
+        var config = DefaultConfig();
+        config.KerfCompensation = KerfMode.ControllerSide;
+        var ctx = SimpleContext();
+        ctx.IsEtch = true;
+        ctx.LibraryFile = "EtchN2.lib";
+        var output = WriteFeature(config, ctx);
+
+        Assert.DoesNotContain("G41", output);
+        Assert.DoesNotContain("G42", output);
+        Assert.DoesNotContain("G40", output);
+    }
+
+    [Fact]
+    public void Etch_AllMovesUseProcessFeedrate()
+    {
+        var config = DefaultConfig();
+        config.KerfCompensation = KerfMode.PreApplied;
+        var codes = new List<ICode>
+        {
+            new RapidMove(1.0, 1.0),
+            new LinearMove(2.0, 1.0) { Layer = LayerType.Leadin },
+            new LinearMove(3.0, 1.0) { Layer = LayerType.Cut }
+        };
+        var ctx = SimpleContext(codes);
+        ctx.IsEtch = true;
+        ctx.LibraryFile = "EtchN2.lib";
+        var output = WriteFeature(config, ctx);
+
+        // Should use #148 for all moves, not #126 for lead-in
+        Assert.DoesNotContain("F#126", output);
+        Assert.Contains("F#148", output);
     }
 
     [Fact]
@@ -378,7 +425,7 @@ public class CincinnatiFeatureWriterTests
         ctx.IsLastFeatureOnSheet = false;
         var output = WriteFeature(config, ctx);
 
-        Assert.Contains("M47 P2000(Safety Headraise)", output);
+        Assert.Contains("M47 P2000 (Safety Headraise)", output);
     }
 
     [Fact]
@@ -404,7 +451,7 @@ public class CincinnatiFeatureWriterTests
         var lines = output.Split(Environment.NewLine, StringSplitOptions.RemoveEmptyEntries);
 
         // Find indices of key lines
-        var rapidIdx = Array.FindIndex(lines, l => l.Contains("G0X"));
+        var rapidIdx = Array.FindIndex(lines, l => l.Contains("G0 X"));
         var partIdx = Array.FindIndex(lines, l => l.Contains("PART:"));
         var g89Idx = Array.FindIndex(lines, l => l.Contains("G89"));
         var g84Idx = Array.FindIndex(lines, l => l.Contains("G84"));

OpenNest.Tests/Cincinnati/CincinnatiPostProcessorTests.cs

@@ -17,7 +17,6 @@ public class CincinnatiPostProcessorTests
         var config = new CincinnatiPostConfig
         {
             ConfigurationName = "CL940",
-            DefaultLibraryFile = "MS135N2PANEL.lib",
             PostedAccuracy = 4
         };
         var post = new CincinnatiPostProcessor(config);
@@ -72,7 +71,7 @@ public class CincinnatiPostProcessorTests
         var output = Encoding.UTF8.GetString(ms.ToArray());
 
         // Should only have one sheet subprogram call in main
-        Assert.Contains("N1M98 P101 (SHEET 1)", output);
+        Assert.Contains("N1 M98 P101 (SHEET 1)", output);
         Assert.DoesNotContain("SHEET 2", output);
     }
 
@@ -104,10 +103,19 @@ public class CincinnatiPostProcessorTests
         var config = new CincinnatiPostConfig
         {
             ConfigurationName = "CL940_CORONA",
-            DefaultLibraryFile = "MS135N2PANEL.lib",
+            DefaultAssistGas = "N2",
+            DefaultEtchGas = "N2",
             PostedUnits = Units.Inches,
             KerfCompensation = KerfMode.ControllerSide,
-            UseAntiDive = true
+            UseAntiDive = true,
+            MaterialLibraries = new()
+            {
+                new MaterialLibraryEntry { Material = "Mild Steel", Thickness = 0.135, Gas = "N2", Library = "MS135N2PANEL.lib" }
+            },
+            EtchLibraries = new()
+            {
+                new EtchLibraryEntry { Gas = "N2", Library = "EtchN2.lib" }
+            }
         };
 
         var opts = new JsonSerializerOptions
@@ -119,10 +127,15 @@ public class CincinnatiPostProcessorTests
         var deserialized = JsonSerializer.Deserialize<CincinnatiPostConfig>(json, opts);
 
         Assert.Equal("CL940_CORONA", deserialized.ConfigurationName);
-        Assert.Equal("MS135N2PANEL.lib", deserialized.DefaultLibraryFile);
+        Assert.Equal("N2", deserialized.DefaultAssistGas);
+        Assert.Equal("N2", deserialized.DefaultEtchGas);
         Assert.Equal(Units.Inches, deserialized.PostedUnits);
         Assert.Equal(KerfMode.ControllerSide, deserialized.KerfCompensation);
         Assert.True(deserialized.UseAntiDive);
+        Assert.Single(deserialized.MaterialLibraries);
+        Assert.Equal("MS135N2PANEL.lib", deserialized.MaterialLibraries[0].Library);
+        Assert.Single(deserialized.EtchLibraries);
+        Assert.Equal("EtchN2.lib", deserialized.EtchLibraries[0].Library);
 
         // Enums serialize as strings
         Assert.Contains("\"Inches\"", json);
@@ -157,21 +170,21 @@ public class CincinnatiPostProcessorTests
         var output = Encoding.UTF8.GetString(ms.ToArray());
 
         // Sheet should contain M98 call to part sub-program
-        Assert.Contains("M98P200", output);
+        Assert.Contains("M98 P200", output);
 
         // Should have G92 for local coordinate positioning
-        Assert.Contains("G92X0Y0", output);
+        Assert.Contains("G92 X0 Y0", output);
 
         // Part sub-program definition
         Assert.Contains(":200", output);
         Assert.Contains("G84", output);
 
-        // Sub-program ends with G0X0Y0 and M99
-        Assert.Contains("G0X0Y0", output);
-        Assert.Contains("M99(END OF Square)", output);
+        // Sub-program ends with G0 X0 Y0 and M99
+        Assert.Contains("G0 X0 Y0", output);
+        Assert.Contains("M99 (END OF Square)", output);
 
         // G92 restore after M98 call
-        Assert.Contains("G92X", output);
+        Assert.Contains("G92 X", output);
     }
 
     [Fact]
@@ -198,7 +211,7 @@ public class CincinnatiPostProcessorTests
         var output = Encoding.UTF8.GetString(ms.ToArray());
 
         // Both parts should call the same sub-program
-        var m98Count = System.Text.RegularExpressions.Regex.Matches(output, "M98P200").Count;
+        var m98Count = System.Text.RegularExpressions.Regex.Matches(output, @"M98 P200\b").Count;
         Assert.Equal(2, m98Count);
 
         // Only one sub-program definition
@@ -238,8 +251,8 @@ public class CincinnatiPostProcessorTests
         // Should have two different sub-programs
         Assert.Contains(":200", output);
         Assert.Contains(":201", output);
-        Assert.Contains("M98P200", output);
-        Assert.Contains("M98P201", output);
+        Assert.Contains("M98 P200", output);
+        Assert.Contains("M98 P201", output);
     }
 
     [Fact]
@@ -268,7 +281,7 @@ public class CincinnatiPostProcessorTests
         var output = Encoding.UTF8.GetString(ms.ToArray());
 
         // Regular part uses sub-program
-        Assert.Contains("M98P200", output);
+        Assert.Contains("M98 P200", output);
         Assert.Contains(":200", output);
 
         // Cutoff should NOT have its own sub-program

OpenNest.Tests/Cincinnati/CincinnatiPreambleWriterTests.cs

@@ -13,14 +13,13 @@ public class CincinnatiPreambleWriterTests
         var config = new CincinnatiPostConfig
         {
             ConfigurationName = "CL940",
-            PostedUnits = Units.Inches,
-            DefaultLibraryFile = "MS135N2PANEL.lib"
+            PostedUnits = Units.Inches
         };
         var sb = new StringBuilder();
         using var sw = new StringWriter(sb);
         var writer = new CincinnatiPreambleWriter(config);
 
-        writer.WriteMainProgram(sw, "TestNest", "Mild Steel, 10GA", 2);
+        writer.WriteMainProgram(sw, "TestNest", "Mild Steel, 10GA", 2, "MS135N2PANEL.lib");
 
         var output = sb.ToString();
         Assert.Contains("( NEST TestNest )", output);
@@ -30,8 +29,8 @@ public class CincinnatiPreambleWriterTests
         Assert.Contains("G89 P MS135N2PANEL.lib", output);
         Assert.Contains("M98 P100 (Variable Declaration)", output);
         Assert.Contains("GOTO1 (GOTO SHEET NUMBER)", output);
-        Assert.Contains("N1M98 P101 (SHEET 1)", output);
-        Assert.Contains("N2M98 P102 (SHEET 2)", output);
+        Assert.Contains("N1 M98 P101 (SHEET 1)", output);
+        Assert.Contains("N2 M98 P102 (SHEET 2)", output);
         Assert.Contains("M30 (END OF MAIN)", output);
     }
 
@@ -43,7 +42,7 @@ public class CincinnatiPreambleWriterTests
         using var sw = new StringWriter(sb);
         var writer = new CincinnatiPreambleWriter(config);
 
-        writer.WriteMainProgram(sw, "Test", "", 1);
+        writer.WriteMainProgram(sw, "Test", "", 1, "");
 
         Assert.Contains("G21", sb.ToString());
     }
@@ -56,7 +55,7 @@ public class CincinnatiPreambleWriterTests
         using var sw = new StringWriter(sb);
         var writer = new CincinnatiPreambleWriter(config);
 
-        writer.WriteMainProgram(sw, "Test", "", 1);
+        writer.WriteMainProgram(sw, "Test", "", 1, "");
 
         Assert.Contains("G61", sb.ToString());
     }
@@ -69,7 +68,7 @@ public class CincinnatiPreambleWriterTests
         using var sw = new StringWriter(sb);
         var writer = new CincinnatiPreambleWriter(config);
 
-        writer.WriteMainProgram(sw, "Test", "", 1);
+        writer.WriteMainProgram(sw, "Test", "", 1, "");
 
         Assert.DoesNotContain("G61", sb.ToString());
     }

OpenNest.Tests/Cincinnati/CincinnatiSheetWriterTests.cs

@@ -1,3 +1,4 @@
+using System.Collections.Generic;
 using System.IO;
 using System.Linq;
 using System.Text;
@@ -14,7 +15,6 @@ public class CincinnatiSheetWriterTests
     {
         var config = new CincinnatiPostConfig
         {
-            DefaultLibraryFile = "MS135N2PANEL.lib",
             PostedAccuracy = 4
         };
         var plate = new Plate(48.0, 96.0);
@@ -24,14 +24,15 @@ public class CincinnatiSheetWriterTests
         using var sw = new StringWriter(sb);
         var sheetWriter = new CincinnatiSheetWriter(config, new ProgramVariableManager());
 
-        sheetWriter.Write(sw, plate, "TestNest", 1, 101);
+        sheetWriter.Write(sw, plate, "TestNest", 1, 101, "MS135N2PANEL.lib", "EtchN2.lib");
 
         var output = sb.ToString();
         Assert.Contains(":101", output);
         Assert.Contains("( Sheet 1 )", output);
         Assert.Contains("#110=", output);
         Assert.Contains("#111=", output);
-        Assert.Contains("G92X#5021Y#5022", output);
+        Assert.Contains("G92 X#5021 Y#5022", output);
+        Assert.Contains("G89 P MS135N2PANEL.lib", output);
         Assert.Contains("M99", output);
     }
 
@@ -50,11 +51,11 @@ public class CincinnatiSheetWriterTests
         using var sw = new StringWriter(sb);
         var sheetWriter = new CincinnatiSheetWriter(config, new ProgramVariableManager());
 
-        sheetWriter.Write(sw, plate, "TestNest", 1, 101);
+        sheetWriter.Write(sw, plate, "TestNest", 1, 101, "", "");
 
         var output = sb.ToString();
         Assert.Contains("M42", output);
-        Assert.Contains("G0X0Y0", output);
+        Assert.Contains("G0 X0 Y0", output);
         Assert.Contains("M50", output);
     }
 
@@ -68,7 +69,7 @@ public class CincinnatiSheetWriterTests
         using var sw = new StringWriter(sb);
         var sheetWriter = new CincinnatiSheetWriter(config, new ProgramVariableManager());
 
-        sheetWriter.Write(sw, plate, "TestNest", 1, 101);
+        sheetWriter.Write(sw, plate, "TestNest", 1, 101, "", "");
 
         Assert.Equal("", sb.ToString());
     }
@@ -96,7 +97,7 @@ public class CincinnatiSheetWriterTests
         using var sw = new StringWriter(sb);
         var sheetWriter = new CincinnatiSheetWriter(config, new ProgramVariableManager());
 
-        sheetWriter.Write(sw, plate, "TestNest", 1, 101);
+        sheetWriter.Write(sw, plate, "TestNest", 1, 101, "", "");
 
         var output = sb.ToString();
         // Should have two G84 pierce commands (one per contour)
@@ -104,6 +105,80 @@ public class CincinnatiSheetWriterTests
         Assert.Equal(2, g84Count);
     }
 
+    [Fact]
+    public void WriteSheet_EtchFeaturesOrderedBeforeCut()
+    {
+        var config = new CincinnatiPostConfig { PostedAccuracy = 4 };
+        var pgm = new Program();
+        // Cut contour first in program
+        pgm.Codes.Add(new RapidMove(0, 0));
+        pgm.Codes.Add(new LinearMove(5, 0) { Layer = LayerType.Cut });
+        pgm.Codes.Add(new LinearMove(5, 5) { Layer = LayerType.Cut });
+        // Etch contour second in program
+        pgm.Codes.Add(new RapidMove(1, 1));
+        pgm.Codes.Add(new LinearMove(2, 1) { Layer = LayerType.Scribe });
+        pgm.Codes.Add(new LinearMove(2, 2) { Layer = LayerType.Scribe });
+
+        var plate = new Plate(48.0, 96.0);
+        plate.Parts.Add(new Part(new Drawing("MixedPart", pgm)));
+
+        var sb = new StringBuilder();
+        using var sw = new StringWriter(sb);
+        var sheetWriter = new CincinnatiSheetWriter(config, new ProgramVariableManager());
+
+        sheetWriter.Write(sw, plate, "TestNest", 1, 101, "MS250O2.lib", "EtchN2.lib");
+
+        var output = sb.ToString();
+        // Etch (G85) should appear before cut (G84)
+        var g85Idx = output.IndexOf("G85");
+        var g84Idx = output.IndexOf("G84");
+        Assert.True(g85Idx >= 0, "G85 should be present for etch");
+        Assert.True(g84Idx >= 0, "G84 should be present for cut");
+        Assert.True(g85Idx < g84Idx, "G85 (etch) should come before G84 (cut)");
+
+        // Etch uses etch library
+        Assert.Contains("G89 P EtchN2.lib", output);
+        // Cut uses cut library
+        Assert.Contains("G89 P MS250O2.lib", output);
+    }
+
+    [Fact]
+    public void IsFeatureEtch_ReturnsTrueForScribeLayer()
+    {
+        var codes = new List<ICode>
+        {
+            new RapidMove(0, 0),
+            new LinearMove(1, 0) { Layer = LayerType.Scribe },
+            new LinearMove(1, 1) { Layer = LayerType.Scribe }
+        };
+
+        Assert.True(CincinnatiSheetWriter.IsFeatureEtch(codes));
+    }
+
+    [Fact]
+    public void IsFeatureEtch_ReturnsFalseForCutLayer()
+    {
+        var codes = new List<ICode>
+        {
+            new RapidMove(0, 0),
+            new LinearMove(1, 0) { Layer = LayerType.Cut },
+            new LinearMove(1, 1) { Layer = LayerType.Cut }
+        };
+
+        Assert.False(CincinnatiSheetWriter.IsFeatureEtch(codes));
+    }
+
+    [Fact]
+    public void IsFeatureEtch_ReturnsFalseForRapidsOnly()
+    {
+        var codes = new List<ICode>
+        {
+            new RapidMove(0, 0)
+        };
+
+        Assert.False(CincinnatiSheetWriter.IsFeatureEtch(codes));
+    }
+
     private static Program CreateSimpleProgram()
     {
         var pgm = new Program();

OpenNest.Tests/Cincinnati/MaterialLibraryResolverTests.cs

@@ -0,0 +1,160 @@
+using OpenNest.Posts.Cincinnati;
+
+namespace OpenNest.Tests.Cincinnati;
+
+public class MaterialLibraryResolverTests
+{
+    private static CincinnatiPostConfig ConfigWithLibraries() => new()
+    {
+        DefaultAssistGas = "O2",
+        DefaultEtchGas = "N2",
+        MaterialLibraries = new()
+        {
+            new MaterialLibraryEntry { Material = "Mild Steel", Thickness = 0.250, Gas = "O2", Library = "MS250O2.lib" },
+            new MaterialLibraryEntry { Material = "Mild Steel", Thickness = 0.250, Gas = "N2", Library = "MS250N2.lib" },
+            new MaterialLibraryEntry { Material = "Aluminum", Thickness = 0.125, Gas = "N2", Library = "AL125N2.lib" },
+            new MaterialLibraryEntry { Material = "Stainless Steel", Thickness = 0.375, Gas = "AIR", Library = "SS375AIR.lib" }
+        },
+        EtchLibraries = new()
+        {
+            new EtchLibraryEntry { Gas = "N2", Library = "EtchN2.lib" },
+            new EtchLibraryEntry { Gas = "O2", Library = "EtchO2.lib" },
+            new EtchLibraryEntry { Gas = "AIR", Library = "EtchAIR.lib" }
+        }
+    };
+
+    [Fact]
+    public void ResolveCutLibrary_ExactMatch()
+    {
+        var resolver = new MaterialLibraryResolver(ConfigWithLibraries());
+        var result = resolver.ResolveCutLibrary("Mild Steel", 0.250, "O2");
+        Assert.Equal("MS250O2.lib", result);
+    }
+
+    [Fact]
+    public void ResolveCutLibrary_CaseInsensitiveMaterial()
+    {
+        var resolver = new MaterialLibraryResolver(ConfigWithLibraries());
+        var result = resolver.ResolveCutLibrary("mild steel", 0.250, "O2");
+        Assert.Equal("MS250O2.lib", result);
+    }
+
+    [Fact]
+    public void ResolveCutLibrary_CaseInsensitiveGas()
+    {
+        var resolver = new MaterialLibraryResolver(ConfigWithLibraries());
+        var result = resolver.ResolveCutLibrary("Mild Steel", 0.250, "o2");
+        Assert.Equal("MS250O2.lib", result);
+    }
+
+    [Fact]
+    public void ResolveCutLibrary_ThicknessWithinTolerance()
+    {
+        var resolver = new MaterialLibraryResolver(ConfigWithLibraries());
+        var result = resolver.ResolveCutLibrary("Mild Steel", 0.2505, "O2");
+        Assert.Equal("MS250O2.lib", result);
+    }
+
+    [Fact]
+    public void ResolveCutLibrary_ThicknessOutsideTolerance_ReturnsEmpty()
+    {
+        var resolver = new MaterialLibraryResolver(ConfigWithLibraries());
+        var result = resolver.ResolveCutLibrary("Mild Steel", 0.260, "O2");
+        Assert.Equal("", result);
+    }
+
+    [Fact]
+    public void ResolveCutLibrary_NoMatch_ReturnsEmpty()
+    {
+        var resolver = new MaterialLibraryResolver(ConfigWithLibraries());
+        var result = resolver.ResolveCutLibrary("Titanium", 0.250, "O2");
+        Assert.Equal("", result);
+    }
+
+    [Fact]
+    public void ResolveCutLibrary_WrongGas_ReturnsEmpty()
+    {
+        var resolver = new MaterialLibraryResolver(ConfigWithLibraries());
+        var result = resolver.ResolveCutLibrary("Mild Steel", 0.250, "AIR");
+        Assert.Equal("", result);
+    }
+
+    [Fact]
+    public void ResolveCutLibrary_DifferentGasSameMaterial()
+    {
+        var resolver = new MaterialLibraryResolver(ConfigWithLibraries());
+        var o2 = resolver.ResolveCutLibrary("Mild Steel", 0.250, "O2");
+        var n2 = resolver.ResolveCutLibrary("Mild Steel", 0.250, "N2");
+        Assert.Equal("MS250O2.lib", o2);
+        Assert.Equal("MS250N2.lib", n2);
+    }
+
+    [Fact]
+    public void ResolveCutLibrary_EmptyList_ReturnsEmpty()
+    {
+        var config = new CincinnatiPostConfig { MaterialLibraries = new() };
+        var resolver = new MaterialLibraryResolver(config);
+        var result = resolver.ResolveCutLibrary("Mild Steel", 0.250, "O2");
+        Assert.Equal("", result);
+    }
+
+    [Fact]
+    public void ResolveEtchLibrary_ExactMatch()
+    {
+        var resolver = new MaterialLibraryResolver(ConfigWithLibraries());
+        var result = resolver.ResolveEtchLibrary("N2");
+        Assert.Equal("EtchN2.lib", result);
+    }
+
+    [Fact]
+    public void ResolveEtchLibrary_CaseInsensitive()
+    {
+        var resolver = new MaterialLibraryResolver(ConfigWithLibraries());
+        var result = resolver.ResolveEtchLibrary("n2");
+        Assert.Equal("EtchN2.lib", result);
+    }
+
+    [Fact]
+    public void ResolveEtchLibrary_NoMatch_ReturnsEmpty()
+    {
+        var resolver = new MaterialLibraryResolver(ConfigWithLibraries());
+        var result = resolver.ResolveEtchLibrary("Argon");
+        Assert.Equal("", result);
+    }
+
+    [Fact]
+    public void ResolveEtchLibrary_EmptyList_ReturnsEmpty()
+    {
+        var config = new CincinnatiPostConfig { EtchLibraries = new() };
+        var resolver = new MaterialLibraryResolver(config);
+        var result = resolver.ResolveEtchLibrary("N2");
+        Assert.Equal("", result);
+    }
+
+    [Fact]
+    public void ResolveGas_UsesNestAssistGas_WhenSet()
+    {
+        var nest = new Nest("Test") { AssistGas = "N2" };
+        var config = new CincinnatiPostConfig { DefaultAssistGas = "O2" };
+        var result = MaterialLibraryResolver.ResolveGas(nest, config);
+        Assert.Equal("N2", result);
+    }
+
+    [Fact]
+    public void ResolveGas_FallsBackToConfig_WhenNestEmpty()
+    {
+        var nest = new Nest("Test") { AssistGas = "" };
+        var config = new CincinnatiPostConfig { DefaultAssistGas = "O2" };
+        var result = MaterialLibraryResolver.ResolveGas(nest, config);
+        Assert.Equal("O2", result);
+    }
+
+    [Fact]
+    public void ResolveGas_FallsBackToConfig_WhenNestNull()
+    {
+        var nest = new Nest("Test");
+        var config = new CincinnatiPostConfig { DefaultAssistGas = "AIR" };
+        var result = MaterialLibraryResolver.ResolveGas(nest, config);
+        Assert.Equal("AIR", result);
+    }
+}

OpenNest.Tests/CutOffTests.cs

@@ -154,10 +154,10 @@ public class CutOffTests
 
         // Plate(100, 50) = Width=100, Length=50. Vertical cut runs along Y (Width axis).
         // BoundingBox Y extent = Size.Width = 100. With 2" overtravel = 102.
-        // Default TowardOrigin: RapidMove to far end (102), LinearMove to near end (0).
-        var rapidMoves = cutoff.Drawing.Program.Codes.OfType<RapidMove>().ToList();
-        Assert.Single(rapidMoves);
-        Assert.Equal(102.0, rapidMoves[0].EndPoint.Y, 5);
+        // Default AwayFromOrigin: RapidMove to near end (0), LinearMove to far end (102).
+        var linearMoves = cutoff.Drawing.Program.Codes.OfType<LinearMove>().ToList();
+        Assert.Single(linearMoves);
+        Assert.Equal(102.0, linearMoves[0].EndPoint.Y, 5);
     }
 
     [Fact]
@@ -171,11 +171,10 @@ public class CutOffTests
         };
         cutoff.Regenerate(plate, settings);
 
+        // AwayFromOrigin: RapidMove to near end (StartLimit=20), LinearMove to far end (100).
         var rapidMoves = cutoff.Drawing.Program.Codes.OfType<RapidMove>().ToList();
         Assert.Single(rapidMoves);
-        var linearMoves = cutoff.Drawing.Program.Codes.OfType<LinearMove>().ToList();
-        Assert.Single(linearMoves);
-        Assert.Equal(20.0, linearMoves[0].EndPoint.Y, 5);
+        Assert.Equal(20.0, rapidMoves[0].EndPoint.Y, 5);
     }
 
     [Fact]
@@ -189,9 +188,10 @@ public class CutOffTests
         };
         cutoff.Regenerate(plate, settings);
 
-        var rapidMoves = cutoff.Drawing.Program.Codes.OfType<RapidMove>().ToList();
-        Assert.Single(rapidMoves);
-        Assert.Equal(80.0, rapidMoves[0].EndPoint.Y, 5);
+        // AwayFromOrigin: RapidMove to near end (0), LinearMove to far end (EndLimit=80).
+        var linearMoves = cutoff.Drawing.Program.Codes.OfType<LinearMove>().ToList();
+        Assert.Single(linearMoves);
+        Assert.Equal(80.0, linearMoves[0].EndPoint.Y, 5);
     }
 
     [Fact]

OpenNest.Tests/PolygonHelperTests.cs

@@ -36,6 +36,47 @@ public class PolygonHelperTests
             $"With-spacing width: {withSpacing.Polygon.BoundingBox.Width:F3}");
     }
 
+    [Fact]
+    public void ExtractPerimeterPolygon_InflatedPolygonIsLarger_ForCWWinding()
+    {
+        // CW winding (standard CNC convention): (0,0)→(0,10)→(10,10)→(10,0)→(0,0)
+        var drawing = TestHelpers.MakeSquareDrawing(10);
+        var noSpacing = PolygonHelper.ExtractPerimeterPolygon(drawing, 0);
+        var withSpacing = PolygonHelper.ExtractPerimeterPolygon(drawing, 1);
+
+        noSpacing.Polygon.UpdateBounds();
+        withSpacing.Polygon.UpdateBounds();
+
+        Assert.True(withSpacing.Polygon.BoundingBox.Width > noSpacing.Polygon.BoundingBox.Width,
+            $"Inflated width {withSpacing.Polygon.BoundingBox.Width:F3} should be > original {noSpacing.Polygon.BoundingBox.Width:F3}");
+        Assert.True(withSpacing.Polygon.BoundingBox.Length > noSpacing.Polygon.BoundingBox.Length,
+            $"Inflated length {withSpacing.Polygon.BoundingBox.Length:F3} should be > original {noSpacing.Polygon.BoundingBox.Length:F3}");
+    }
+
+    [Fact]
+    public void ExtractPerimeterPolygon_InflatedPolygonIsLarger_ForCCWWinding()
+    {
+        // CCW winding: (0,0)→(10,0)→(10,10)→(0,10)→(0,0)
+        var pgm = new CNC.Program();
+        pgm.Codes.Add(new CNC.RapidMove(new Vector(0, 0)));
+        pgm.Codes.Add(new CNC.LinearMove(new Vector(10, 0)));
+        pgm.Codes.Add(new CNC.LinearMove(new Vector(10, 10)));
+        pgm.Codes.Add(new CNC.LinearMove(new Vector(0, 10)));
+        pgm.Codes.Add(new CNC.LinearMove(new Vector(0, 0)));
+        var drawing = new Drawing("ccw-square", pgm);
+
+        var noSpacing = PolygonHelper.ExtractPerimeterPolygon(drawing, 0);
+        var withSpacing = PolygonHelper.ExtractPerimeterPolygon(drawing, 1);
+
+        noSpacing.Polygon.UpdateBounds();
+        withSpacing.Polygon.UpdateBounds();
+
+        Assert.True(withSpacing.Polygon.BoundingBox.Width > noSpacing.Polygon.BoundingBox.Width,
+            $"Inflated width {withSpacing.Polygon.BoundingBox.Width:F3} should be > original {noSpacing.Polygon.BoundingBox.Width:F3}");
+        Assert.True(withSpacing.Polygon.BoundingBox.Length > noSpacing.Polygon.BoundingBox.Length,
+            $"Inflated length {withSpacing.Polygon.BoundingBox.Length:F3} should be > original {noSpacing.Polygon.BoundingBox.Length:F3}");
+    }
+
     [Fact]
     public void ExtractPerimeterPolygon_ReturnsNull_ForEmptyDrawing()
     {

OpenNest/Actions/ActionClone.cs

@@ -187,7 +187,25 @@ namespace OpenNest.Actions
 
             var boxes = new List<Box>();
             foreach (var part in plate.Parts)
+            {
+                if (part.BaseDrawing.IsCutOff)
+                    continue;
+
                 boxes.Add(part.BoundingBox.Offset(plate.PartSpacing));
+            }
+
+            var plateBounds = plate.BoundingBox(includeParts: false);
+            foreach (var cutoff in plate.CutOffs)
+            {
+                Box cutoffBox;
+
+                if (cutoff.Axis == CutOffAxis.Vertical)
+                    cutoffBox = new Box(cutoff.Position.X, plateBounds.Y, 0, plateBounds.Length);
+                else
+                    cutoffBox = new Box(plateBounds.X, cutoff.Position.Y, plateBounds.Width, 0);
+
+                boxes.Add(cutoffBox.Offset(plate.PartSpacing));
+            }
 
             var pt = plateView.CurrentPoint;
             var vertical = SpatialQuery.GetLargestBoxVertically(pt, bounds, boxes);

OpenNest/Actions/ActionSelectArea.cs

@@ -157,7 +157,31 @@ namespace OpenNest.Actions
         public void Update()
         {
             foreach (var part in plateView.Plate.Parts)
+            {
+                if (part.BaseDrawing.IsCutOff)
+                    continue;
+
                 boxes.Add(part.BoundingBox.Offset(plateView.Plate.PartSpacing));
+            }
+
+            // Add thin obstacle boxes from cutoff definitions so that
+            // the area selection correctly treats cutoffs as boundaries.
+            // Cutoff Parts have inflated bounding boxes (their programs use
+            // absolute coordinates, causing BoundingBox to span from origin)
+            // so we derive the position directly from the CutOff definition.
+            var plateBounds = plateView.Plate.BoundingBox(includeParts: false);
+
+            foreach (var cutoff in plateView.Plate.CutOffs)
+            {
+                Box cutoffBox;
+
+                if (cutoff.Axis == CutOffAxis.Vertical)
+                    cutoffBox = new Box(cutoff.Position.X, plateBounds.Y, 0, plateBounds.Length);
+                else
+                    cutoffBox = new Box(plateBounds.X, cutoff.Position.Y, plateBounds.Width, 0);
+
+                boxes.Add(cutoffBox.Offset(plateView.Plate.PartSpacing));
+            }
 
             Bounds = plateView.Plate.WorkArea();
         }

OpenNest/Forms/EditNestForm.cs

@@ -458,6 +458,7 @@ namespace OpenNest.Forms
             PlateView.ZoomToPlate();
             PlateView.Refresh();
             UpdatePlateList();
+            UpdatePlateHeader();
         }
 
         public void SelectAllParts()

OpenNest/Forms/MainForm.Designer.cs

@@ -149,6 +149,8 @@
             engineComboBox = new System.Windows.Forms.ToolStripComboBox();
             btnAutoNest = new System.Windows.Forms.ToolStripButton();
             btnShowRemnants = new System.Windows.Forms.ToolStripButton();
+            toolStripSeparator5 = new System.Windows.Forms.ToolStripSeparator();
+            btnCutOff = new System.Windows.Forms.ToolStripButton();
             pEPToolStripMenuItem = new System.Windows.Forms.ToolStripMenuItem();
             openNestToolStripMenuItem = new System.Windows.Forms.ToolStripMenuItem();
             menuStrip1.SuspendLayout();
@@ -917,7 +919,7 @@
             // toolStrip1
             // 
             toolStrip1.AutoSize = false;
-            toolStrip1.Items.AddRange(new System.Windows.Forms.ToolStripItem[] { btnNew, btnOpen, btnSave, btnSaveAs, toolStripSeparator1, btnZoomOut, btnZoomIn, btnZoomToFit, toolStripSeparator4, engineLabel, engineComboBox, btnAutoNest, btnShowRemnants });
+            toolStrip1.Items.AddRange(new System.Windows.Forms.ToolStripItem[] { btnNew, btnOpen, btnSave, btnSaveAs, toolStripSeparator1, btnZoomOut, btnZoomIn, btnZoomToFit, toolStripSeparator4, engineLabel, engineComboBox, btnAutoNest, btnShowRemnants, toolStripSeparator5, btnCutOff });
             toolStrip1.Location = new System.Drawing.Point(0, 24);
             toolStrip1.Name = "toolStrip1";
             toolStrip1.Size = new System.Drawing.Size(1281, 40);
@@ -1044,12 +1046,31 @@
             //
             // btnShowRemnants
             //
-            btnShowRemnants.DisplayStyle = System.Windows.Forms.ToolStripItemDisplayStyle.Text;
+            btnShowRemnants.DisplayStyle = System.Windows.Forms.ToolStripItemDisplayStyle.Image;
+            btnShowRemnants.Image = Properties.Resources.remnants;
+            btnShowRemnants.ImageScaling = System.Windows.Forms.ToolStripItemImageScaling.None;
             btnShowRemnants.Name = "btnShowRemnants";
-            btnShowRemnants.Size = new System.Drawing.Size(64, 37);
+            btnShowRemnants.Padding = new System.Windows.Forms.Padding(5, 0, 5, 0);
+            btnShowRemnants.Size = new System.Drawing.Size(38, 37);
             btnShowRemnants.Text = "Remnants";
             btnShowRemnants.Click += ShowRemnants_Click;
             //
+            // toolStripSeparator5
+            //
+            toolStripSeparator5.Name = "toolStripSeparator5";
+            toolStripSeparator5.Size = new System.Drawing.Size(6, 40);
+            //
+            // btnCutOff
+            //
+            btnCutOff.DisplayStyle = System.Windows.Forms.ToolStripItemDisplayStyle.Image;
+            btnCutOff.Image = Properties.Resources.cutoff;
+            btnCutOff.ImageScaling = System.Windows.Forms.ToolStripItemImageScaling.None;
+            btnCutOff.Name = "btnCutOff";
+            btnCutOff.Padding = new System.Windows.Forms.Padding(5, 0, 5, 0);
+            btnCutOff.Size = new System.Drawing.Size(38, 37);
+            btnCutOff.Text = "Sheet Cut-Off";
+            btnCutOff.Click += CutOff_Click;
+            //
             // pEPToolStripMenuItem
             // 
             pEPToolStripMenuItem.Name = "pEPToolStripMenuItem";
@@ -1213,6 +1234,8 @@
         private System.Windows.Forms.ToolStripComboBox engineComboBox;
         private System.Windows.Forms.ToolStripButton btnAutoNest;
         private System.Windows.Forms.ToolStripButton btnShowRemnants;
+        private System.Windows.Forms.ToolStripSeparator toolStripSeparator5;
+        private System.Windows.Forms.ToolStripButton btnCutOff;
         private System.Windows.Forms.ToolStripMenuItem mnuPlateCutOff;
     }
 }

OpenNest/Properties/Resources.Designer.cs

@@ -80,6 +80,16 @@ namespace OpenNest.Properties {
             }
         }
         
+        /// <summary>
+        ///   Looks up a localized resource of type System.Drawing.Bitmap.
+        /// </summary>
+        internal static System.Drawing.Bitmap cutoff {
+            get {
+                object obj = ResourceManager.GetObject("cutoff", resourceCulture);
+                return ((System.Drawing.Bitmap)(obj));
+            }
+        }
+
         /// <summary>
         ///   Looks up a localized resource of type System.Drawing.Bitmap.
         /// </summary>
@@ -160,6 +170,16 @@ namespace OpenNest.Properties {
             }
         }
         
+        /// <summary>
+        ///   Looks up a localized resource of type System.Drawing.Bitmap.
+        /// </summary>
+        internal static System.Drawing.Bitmap remnants {
+            get {
+                object obj = ResourceManager.GetObject("remnants", resourceCulture);
+                return ((System.Drawing.Bitmap)(obj));
+            }
+        }
+
         /// <summary>
         ///   Looks up a localized resource of type System.Drawing.Bitmap.
         /// </summary>

OpenNest/Properties/Resources.resx

@@ -175,4 +175,10 @@
   <data name="zoom_out" type="System.Resources.ResXFileRef, System.Windows.Forms">
     <value>..\Resources\zoom_out.png;System.Drawing.Bitmap, System.Drawing, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a</value>
   </data>
+  <data name="cutoff" type="System.Resources.ResXFileRef, System.Windows.Forms">
+    <value>..\Resources\cutoff.png;System.Drawing.Bitmap, System.Drawing, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a</value>
+  </data>
+  <data name="remnants" type="System.Resources.ResXFileRef, System.Windows.Forms">
+    <value>..\Resources\remnants.png;System.Drawing.Bitmap, System.Drawing, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a</value>
+  </data>
 </root>

tools/NestBuilder/NestBuilder.csproj

@@ -0,0 +1,10 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net8.0-windows</TargetFramework>
+  </PropertyGroup>
+  <ItemGroup>
+    <ProjectReference Include="..\..\OpenNest.Core\OpenNest.Core.csproj" />
+    <ProjectReference Include="..\..\OpenNest.IO\OpenNest.IO.csproj" />
+  </ItemGroup>
+</Project>

tools/NestBuilder/Program.cs

@@ -0,0 +1,209 @@
+using System;
+using System.Drawing;
+using System.IO;
+using System.Linq;
+using OpenNest;
+using OpenNest.Converters;
+using OpenNest.Geometry;
+using Size = OpenNest.Geometry.Size;
+using OpenNest.IO;
+
+var partColors = new Color[]
+{
+    Color.FromArgb(205, 92, 92),    // Indian Red
+    Color.FromArgb(148, 103, 189),  // Medium Purple
+    Color.FromArgb(75, 180, 175),   // Teal
+    Color.FromArgb(210, 190, 75),   // Goldenrod
+    Color.FromArgb(190, 85, 175),   // Orchid
+    Color.FromArgb(185, 115, 85),   // Sienna
+    Color.FromArgb(120, 100, 190),  // Slate Blue
+    Color.FromArgb(200, 100, 140),  // Rose
+    Color.FromArgb(80, 175, 155),   // Sea Green
+    Color.FromArgb(195, 160, 85),   // Dark Khaki
+    Color.FromArgb(175, 95, 160),   // Plum
+    Color.FromArgb(215, 130, 130),  // Light Coral
+};
+
+var templateDir = @"C:\Users\AJ\Desktop\Projects\OpenNest\docs\Templates";
+var outputDir = @"C:\Users\AJ\Desktop\Projects\OpenNest\docs\Templates\Nests";
+Directory.CreateDirectory(outputDir);
+
+// BOM: (fileName, qty, thickness, material)
+var bom = new (string File, int Qty, double Thickness, string Material)[]
+{
+    ("PT01", 2, 0.250, "304SS"),
+    ("PT02", 5, 0.625, "304SS"),
+    ("PT03", 4, 0.250, "304SS"),
+    ("PT04", 4, 0.250, "304SS"),
+    ("PT05", 1, 0.250, "304SS"),
+    ("PT06", 21, 0.375, "304SS"),
+    ("PT07", 2, 0.250, "304SS"),
+    ("PT08", 22, 0.250, "304SS"),
+    ("PT11", 2, 0.1875, "304SS"),
+    ("PT12", 2, 0.1875, "304SS"),
+    ("PT13", 6, 0.1875, "304SS"),
+    ("PT15", 6, 0.1875, "304SS"),
+    ("PT16", 6, 0.1875, "304SS"),
+    ("PT18", 3, 0.250, "304SS"),
+    ("PT19", 3, 0.1875, "304SS"),
+    ("PT20", 2, 0.1196, "304SS"),
+    ("PT21", 6, 0.1196, "304SS"),
+    ("PT22", 2, 0.1196, "304SS"),
+    ("PT23", 1, 0.0598, "304SS"),
+    ("PT24", 1, 0.0598, "304SS"),
+    ("PT26", 4, 0.250, "304SS"),
+    ("PT27", 2, 0.250, "304SS"),
+    ("PT28", 4, 0.250, "304SS"),
+    ("PT29", 6, 0.250, "304SS"),
+    ("PT33", 2, 0.250, "304SS"),
+    ("PT34", 4, 0.250, "304SS"),
+    ("PT35", 3, 0.1875, "304SS"),
+    ("PT36", 4, 0.1875, "304SS"),
+    ("PT37", 4, 0.1875, "304SS"),
+    ("PT38", 4, 0.1875, "304SS"),
+    ("PT39", 2, 0.0598, "304SS"),
+    ("PT40", 4, 0.0598, "304SS"),
+    ("PT41", 1, 0.1875, "304SS"),
+    ("PT43", 1, 0.0598, "304SS"),
+    ("PT44", 1, 0.0598, "304SS"),
+    ("PT45", 1, 0.250, "304SS"),
+    ("PT46", 2, 0.250, "304SS"),
+    ("PT47", 4, 0.250, "304SS"),
+    ("PT48", 1, 0.250, "304SS"),
+    ("PT49", 1, 0.750, "PCS"),
+    ("PT50", 2, 0.375, "PCS"),
+    ("PT51", 1, 0.250, "304SS"),
+    ("PT52", 1, 0.1875, "304SS"),
+    ("PT53", 1, 0.1875, "304SS"),
+    ("PT54", 2, 0.250, "304SS"),
+    ("PT55", 1, 0.1196, "304SS"),
+    ("PT56", 1, 0.1196, "304SS"),
+    ("PT57", 1, 0.0598, "304SS"),
+    ("PT58", 1, 0.0598, "304SS"),
+};
+
+// Group by material + thickness
+var groups = bom.GroupBy(b => (b.Material, b.Thickness)).OrderBy(g => g.Key.Material).ThenBy(g => g.Key.Thickness);
+
+foreach (var group in groups)
+{
+    var material = group.Key.Material;
+    var thickness = group.Key.Thickness;
+    var thicknessLabel = thickness switch
+    {
+        0.0598 => "16GA",
+        0.1196 => "11GA",
+        0.1875 => "3-16",
+        0.250 => "1-4",
+        0.375 => "3-8",
+        0.625 => "5-8",
+        0.750 => "3-4",
+        _ => thickness.ToString("F4")
+    };
+
+    var nestName = $"4526 A14 - {material} {thicknessLabel}";
+    Console.WriteLine($"\n=== {nestName} ===");
+
+    var nest = new Nest();
+    nest.Name = nestName;
+    nest.PlateDefaults.Thickness = thickness;
+    nest.PlateDefaults.Material = new Material { Name = material };
+    nest.PlateDefaults.PartSpacing = 0.125;
+    nest.PlateDefaults.EdgeSpacing = new Spacing(0.25, 0.25, 0.25, 0.25);
+
+    // Import DXFs for this group
+    var importer = new DxfImporter();
+    var colorIndex = 0;
+    double maxMinDim = 0;
+    double maxMaxDim = 0;
+
+    foreach (var item in group)
+    {
+        var dxfPath = Path.Combine(templateDir, $"4526 A14 {item.File}.dxf");
+        if (!File.Exists(dxfPath))
+        {
+            Console.WriteLine($"  WARNING: {dxfPath} not found, skipping");
+            continue;
+        }
+
+        if (!importer.GetGeometry(dxfPath, out var geometry) || geometry.Count == 0)
+        {
+            Console.WriteLine($"  WARNING: no geometry in {item.File}, skipping");
+            continue;
+        }
+
+        var pgm = ConvertGeometry.ToProgram(geometry);
+        if (pgm == null)
+        {
+            Console.WriteLine($"  WARNING: failed to convert {item.File}, skipping");
+            continue;
+        }
+
+        var drawing = new Drawing(item.File, pgm);
+        drawing.Quantity.Required = item.Qty;
+        drawing.Material = new Material { Name = material };
+        drawing.Color = partColors[colorIndex % partColors.Length];
+        colorIndex++;
+        nest.Drawings.Add(drawing);
+
+        var bbox = pgm.BoundingBox();
+        var minDim = System.Math.Min(bbox.Width, bbox.Length);
+        var maxDim = System.Math.Max(bbox.Width, bbox.Length);
+        maxMinDim = System.Math.Max(maxMinDim, minDim);
+        maxMaxDim = System.Math.Max(maxMaxDim, maxDim);
+
+        Console.WriteLine($"  {item.File}: {bbox.Width:F2} x {bbox.Length:F2}, qty={item.Qty}");
+    }
+
+    // Choose plate size based on largest part dimensions
+    // Size(width, length) — width is the short side, length is the long side
+    // Standard sizes: 48x96, 48x120, 60x120, 60x144, 72x144, 96x120
+    double plateW, plateL;
+    if (maxMinDim <= 47.5 && maxMaxDim <= 95.5)
+    {
+        plateW = 48; plateL = 96;
+    }
+    else if (maxMinDim <= 47.5 && maxMaxDim <= 119.5)
+    {
+        plateW = 48; plateL = 120;
+    }
+    else if (maxMinDim <= 59.5 && maxMaxDim <= 119.5)
+    {
+        plateW = 60; plateL = 120;
+    }
+    else if (maxMinDim <= 59.5 && maxMaxDim <= 143.5)
+    {
+        plateW = 60; plateL = 144;
+    }
+    else if (maxMinDim <= 71.5 && maxMaxDim <= 143.5)
+    {
+        plateW = 72; plateL = 144;
+    }
+    else if (maxMinDim <= 95.5 && maxMaxDim <= 119.5)
+    {
+        plateW = 96; plateL = 120;
+    }
+    else
+    {
+        // Fallback: round up to nearest 12"
+        plateW = System.Math.Ceiling((maxMinDim + 1) / 12.0) * 12;
+        plateL = System.Math.Ceiling((maxMaxDim + 1) / 12.0) * 12;
+    }
+
+    // Create one empty plate via PlateDefaults so it inherits settings
+    nest.PlateDefaults.Size = new Size(plateW, plateL);
+    var plate = nest.CreatePlate();
+    plate.Quantity = 1;
+
+    Console.WriteLine($"  Plate size: {plateW} x {plateL} (W x L)");
+    Console.WriteLine($"  Drawings: {nest.Drawings.Count}");
+
+    var outputPath = Path.Combine(outputDir, $"{nestName}.nest");
+    var writer = new NestWriter(nest);
+    if (writer.Write(outputPath))
+        Console.WriteLine($"  Saved: {outputPath}");
+    else
+        Console.WriteLine($"  ERROR: failed to save {outputPath}");
+}
+
+Console.WriteLine("\nDone!");