feat(io): add Gravograph .CHR font reader with text-to-geometry

Add ChrFont, a reader for Gravograph .CHR engraving fonts, plus UI to
convert placed text into engraved geometry in the CAD converter.

The .CHR files are obfuscated with a single-byte XOR. Different
GravoStyle releases use different keys (0x2F in older versions, 0xCF in
the 7000 series, and others across the font library), so the key is
auto-detected from byte 1 of the file: the font name is ASCII stored as
UTF-16LE, so the high byte of its first character is 0x00 in plaintext
and the raw byte equals the key. This reads every font in a GravoStyle
install regardless of version, not just one hardcoded key.

UI: right-clicking a text item in EntityView raises TextConvertRequested;
CadConverterForm renders it via ChrFont with H/V alignment and adds the
result on an ENGRAVE layer.

Tests use Xunit.SkippableFact and a gitignored test-config.json so the
suite points at a local .CHR file without committing proprietary assets.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

.gitignore

@@ -213,3 +213,6 @@ docs/superpowers/
 
 # Launch settings
 **/Properties/launchSettings.json
+
+# Local test config (contains user-specific paths to proprietary test assets)
+OpenNest.Tests/test-config.json

OpenNest.IO/ChrFont.cs

@@ -0,0 +1,369 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Text;
+using OpenNest.Geometry;
+
+namespace OpenNest.IO
+{
+    public class ChrFont
+    {
+        private readonly Dictionary<int, ChrGlyph> glyphs = new();
+
+        public string Name { get; internal set; }
+        public string Version { get; internal set; }
+        public double CapHeight { get; internal set; } = 5000;
+
+        internal void AddGlyph(int charCode, ChrGlyph glyph)
+        {
+            glyphs[charCode] = glyph;
+        }
+
+        public bool HasGlyph(int charCode) => glyphs.ContainsKey(charCode);
+
+        public ChrGlyph GetGlyph(int charCode) =>
+            glyphs.TryGetValue(charCode, out var g) ? g : null;
+
+        public double MeasureTextWidth(string text, double height)
+        {
+            var scale = height / CapHeight;
+            double width = 0;
+            foreach (var ch in text)
+            {
+                var glyph = GetGlyph(ch);
+                if (glyph == null)
+                {
+                    var space = GetGlyph(' ');
+                    width += (space?.AdvanceWidth ?? CapHeight * 0.6) * scale;
+                    continue;
+                }
+                width += glyph.AdvanceWidth * scale;
+            }
+            return width;
+        }
+
+        public List<Entity> RenderText(string text, double height, Vector position, Layer layer = null)
+        {
+            var scale = height / CapHeight;
+            var entities = new List<Entity>();
+            var cursorX = position.X;
+
+            foreach (var ch in text)
+            {
+                var glyph = GetGlyph(ch);
+                if (glyph == null)
+                {
+                    var space = GetGlyph(' ');
+                    cursorX += (space?.AdvanceWidth ?? CapHeight * 0.6) * scale;
+                    continue;
+                }
+
+                var glyphEntities = glyph.ToEntities(scale, cursorX, position.Y, layer);
+                entities.AddRange(glyphEntities);
+                cursorX += glyph.AdvanceWidth * scale;
+            }
+
+            return entities;
+        }
+
+        public static ChrFont Read(string path, byte? xorKey = null)
+        {
+            var raw = File.ReadAllBytes(path);
+
+            // The whole file is obfuscated with a single-byte XOR. Different
+            // GravoStyle versions use different keys (0x2F in older releases,
+            // 0xCF in 7000-series). The font name at offset 0 is ASCII stored
+            // as UTF-16LE, so the high byte of its first character is 0x00 in
+            // plaintext — which means raw[1] is exactly the XOR key. Detect it
+            // from the file unless the caller forces a specific key.
+            var key = xorKey ?? (raw.Length > 1 ? raw[1] : (byte)0x2F);
+
+            var data = new byte[raw.Length];
+            for (var i = 0; i < raw.Length; i++)
+                data[i] = (byte)(raw[i] ^ key);
+
+            return Parse(data);
+        }
+
+        private static ChrFont Parse(byte[] data)
+        {
+            var font = new ChrFont();
+
+            font.Name = Encoding.Unicode.GetString(data, 0, 26).TrimEnd('\0').Trim();
+            font.Version = Encoding.ASCII.GetString(data, 26, 12).TrimEnd('\0').Trim();
+
+            var charTable = new List<(int charCode, int offset)>();
+            var i = 0x40;
+            while (i + 5 < data.Length)
+            {
+                var charCode = data[i] | (data[i + 1] << 8);
+                var offset = data[i + 2] | (data[i + 3] << 8) | (data[i + 4] << 16) | (data[i + 5] << 24);
+
+                if (charCode < 0x20 || offset == 0 || offset >= data.Length)
+                    break;
+
+                charTable.Add((charCode, offset));
+                i += 6;
+            }
+
+            for (var c = 0; c < charTable.Count; c++)
+            {
+                var (charCode, offset) = charTable[c];
+
+                var nextOffset = c + 1 < charTable.Count
+                    ? FindNextOffset(charTable, offset, data.Length)
+                    : data.Length;
+
+                var glyph = ParseGlyph(data, offset, nextOffset);
+                if (glyph != null)
+                    font.AddGlyph(charCode, glyph);
+            }
+
+            if (font.glyphs.Count > 0)
+            {
+                foreach (var g in font.glyphs.Values)
+                {
+                    if (g.CapHeight > 0)
+                    {
+                        font.CapHeight = g.CapHeight;
+                        break;
+                    }
+                }
+            }
+
+            return font;
+        }
+
+        private static int FindNextOffset(List<(int charCode, int offset)> table, int currentOffset, int fileLength)
+        {
+            var best = fileLength;
+            foreach (var (_, off) in table)
+            {
+                if (off > currentOffset && off < best)
+                    best = off;
+            }
+            return best;
+        }
+
+        private static ChrGlyph ParseGlyph(byte[] data, int offset, int endOffset)
+        {
+            if (offset + 92 > data.Length)
+                return null;
+
+            var glyph = new ChrGlyph();
+            glyph.CapHeight = ReadBE16(data, offset + 15 * 2);
+            var bearing = System.Math.Abs(ReadBE16(data, offset + 18 * 2));
+            glyph.AdvanceWidth = ReadBE16(data, offset + 22 * 2) + bearing;
+
+            var strokeStart = offset + 92;
+            var pos = strokeStart;
+            var currentStroke = new List<ChrStrokePoint>();
+
+            while (pos + 5 < endOffset)
+            {
+                var cmd = ReadBE16(data, pos);
+                var x = ReadBE16(data, pos + 2);
+                var y = ReadBE16(data, pos + 4);
+                pos += 6;
+
+                if (System.Math.Abs(x) > 15000 || System.Math.Abs(y) > 15000)
+                    break;
+
+                if (cmd < -1000)
+                    break;
+
+                var type = cmd switch
+                {
+                    1 => ChrPointType.Vertex,
+                    4 => ChrPointType.Control,
+                    5 => ChrPointType.EndPoint,
+                    _ => ChrPointType.Vertex,
+                };
+
+                currentStroke.Add(new ChrStrokePoint(type, x, y));
+
+                if (type == ChrPointType.EndPoint)
+                {
+                    if (currentStroke.Count > 0)
+                        glyph.Strokes.Add(currentStroke);
+                    currentStroke = new List<ChrStrokePoint>();
+                }
+            }
+
+            if (currentStroke.Count > 0)
+                glyph.Strokes.Add(currentStroke);
+
+            return glyph;
+        }
+
+        private static int ReadBE16(byte[] data, int offset)
+        {
+            var val = (data[offset] << 8) | data[offset + 1];
+            if (val > 32767) val -= 65536;
+            return val;
+        }
+    }
+
+    internal enum ChrPointType
+    {
+        Vertex,
+        Control,
+        EndPoint,
+    }
+
+    internal struct ChrStrokePoint
+    {
+        public ChrPointType Type;
+        public double X;
+        public double Y;
+
+        public ChrStrokePoint(ChrPointType type, double x, double y)
+        {
+            Type = type;
+            X = x;
+            Y = y;
+        }
+    }
+
+    public class ChrGlyph
+    {
+        internal readonly List<List<ChrStrokePoint>> Strokes = new();
+
+        public double AdvanceWidth { get; internal set; }
+        public double CapHeight { get; internal set; }
+
+        private const int ArcSamples = 16;
+
+        public List<Entity> ToEntities(double scale, double offsetX, double offsetY, Layer layer = null)
+        {
+            var entities = new List<Entity>();
+            layer ??= Layer.Default;
+
+            foreach (var stroke in Strokes)
+            {
+                if (stroke.Count < 2) continue;
+
+                var segments = BuildSegments(stroke);
+                foreach (var seg in segments)
+                {
+                    if (seg.Points.Count < 2) continue;
+
+                    var scaled = new List<Vector>(seg.Points.Count);
+                    foreach (var pt in seg.Points)
+                        scaled.Add(new Vector(pt.X * scale + offsetX, pt.Y * scale + offsetY));
+
+                    var converted = PointsToLines(scaled);
+
+                    foreach (var e in converted)
+                    {
+                        e.Layer = layer;
+                        entities.Add(e);
+                    }
+                }
+            }
+
+            return entities;
+        }
+
+        private static List<Entity> PointsToLines(List<Vector> points)
+        {
+            var entities = new List<Entity>();
+            for (var i = 0; i < points.Count - 1; i++)
+            {
+                if (points[i].DistanceTo(points[i + 1]) < 0.001)
+                    continue;
+                entities.Add(new Line(points[i], points[i + 1]));
+            }
+            return entities;
+        }
+
+        private static List<StrokeSegment> BuildSegments(List<ChrStrokePoint> stroke)
+        {
+            var segments = new List<StrokeSegment>();
+            var current = new StrokeSegment();
+
+            var i = 0;
+            while (i < stroke.Count)
+            {
+                var pt = stroke[i];
+
+                if (pt.Type == ChrPointType.Vertex || pt.Type == ChrPointType.EndPoint)
+                {
+                    if (i + 1 < stroke.Count && stroke[i + 1].Type == ChrPointType.Control)
+                    {
+                        var p0 = new Vector(pt.X, pt.Y);
+                        var pMid = new Vector(stroke[i + 1].X, stroke[i + 1].Y);
+                        var p2End = i + 2 < stroke.Count ? stroke[i + 2] : stroke[i + 1];
+                        var p1 = new Vector(p2End.X, p2End.Y);
+
+                        SampleCircularArc(current.Points, p0, pMid, p1, ArcSamples);
+                        current.HasCurves = true;
+                        i += 2;
+                    }
+                    else
+                    {
+                        current.Points.Add(new Vector(pt.X, pt.Y));
+                        i++;
+                    }
+                }
+                else
+                {
+                    i++;
+                }
+            }
+
+            if (current.Points.Count >= 2)
+                segments.Add(current);
+
+            return segments;
+        }
+
+        private class StrokeSegment
+        {
+            public readonly List<Vector> Points = new();
+            public bool HasCurves;
+        }
+
+        private static void SampleCircularArc(List<Vector> output, Vector p0, Vector pMid, Vector p1, int samples)
+        {
+            if (output.Count == 0 || output[^1].DistanceTo(p0) > 0.01)
+                output.Add(p0);
+
+            double ax = p0.X, ay = p0.Y;
+            double bx = pMid.X, by = pMid.Y;
+            double cx = p1.X, cy = p1.Y;
+
+            var d = 2 * (ax * (by - cy) + bx * (cy - ay) + cx * (ay - by));
+
+            if (System.Math.Abs(d) < 1e-6)
+            {
+                output.Add(pMid);
+                output.Add(p1);
+                return;
+            }
+
+            var ux = ((ax * ax + ay * ay) * (by - cy) + (bx * bx + by * by) * (cy - ay) + (cx * cx + cy * cy) * (ay - by)) / d;
+            var uy = ((ax * ax + ay * ay) * (cx - bx) + (bx * bx + by * by) * (ax - cx) + (cx * cx + cy * cy) * (bx - ax)) / d;
+            var radius = System.Math.Sqrt((ax - ux) * (ax - ux) + (ay - uy) * (ay - uy));
+
+            var a0 = System.Math.Atan2(ay - uy, ax - ux);
+            var am = System.Math.Atan2(by - uy, bx - ux);
+            var a1 = System.Math.Atan2(cy - uy, cx - ux);
+
+            var ccwSweep = a1 - a0;
+            while (ccwSweep <= 0) ccwSweep += 2 * System.Math.PI;
+
+            var midRel = am - a0;
+            while (midRel < 0) midRel += 2 * System.Math.PI;
+
+            var sweep = midRel < ccwSweep ? ccwSweep : ccwSweep - 2 * System.Math.PI;
+
+            for (var i = 1; i <= samples; i++)
+            {
+                var t = (double)i / samples;
+                var angle = a0 + sweep * t;
+                output.Add(new Vector(ux + radius * System.Math.Cos(angle), uy + radius * System.Math.Sin(angle)));
+            }
+        }
+    }
+}

OpenNest.Posts.GravographIS/GravographISPort.cs

@@ -0,0 +1,99 @@
+using System;
+using System.IO.Ports;
+using System.Threading;
+
+namespace OpenNest.Posts.GravographIS
+{
+    /// <summary>
+    /// Serial streamer for the Gravograph IS8000. 9600 8-N-1; flow control is
+    /// configurable and defaults to RTS/CTS (the controller is buffered and drops
+    /// CTS to apply backpressure). The job is sent in modest chunks rather than as
+    /// one giant write so the handshake can pause the write mid-stream.
+    /// </summary>
+    public sealed class GravographISPort : IDisposable
+    {
+        private SerialPort port;
+
+        public const int DefaultBaudRate = 9600;
+        public const int DefaultChunkSize = 256;
+        public const int DefaultWriteTimeoutMs = 30000;
+
+        public int ChunkSize { get; set; } = DefaultChunkSize;
+        public int WriteTimeoutMs { get; set; } = DefaultWriteTimeoutMs;
+
+        public bool IsOpen => port != null && port.IsOpen;
+
+        /// <summary>
+        /// Opens the port at the controller's required line settings (9600 8-N-1)
+        /// with the given <paramref name="handshake"/>. Throws if the port is
+        /// already open or if opening fails.
+        /// </summary>
+        public void Open(string portName, Handshake handshake = Handshake.RequestToSend)
+        {
+            if (string.IsNullOrWhiteSpace(portName))
+                throw new ArgumentException("Port name is required.", nameof(portName));
+            if (port != null)
+                throw new InvalidOperationException("Port is already open.");
+
+            port = new SerialPort(portName, DefaultBaudRate, Parity.None, 8, StopBits.One)
+            {
+                Handshake = handshake,
+                WriteTimeout = WriteTimeoutMs,
+                ReadTimeout = WriteTimeoutMs,
+                // DTR/RTS are needed for some USB-serial bridges and for RTS/CTS flow:
+                DtrEnable = true,
+                RtsEnable = handshake != Handshake.RequestToSend &&
+                            handshake != Handshake.RequestToSendXOnXOff,
+            };
+
+            port.Open();
+        }
+
+        /// <summary>
+        /// Streams the encoded job to the port in chunks. Cancellable. The chunked
+        /// write is intentional — Write() blocks until the OS accepts the bytes,
+        /// which with RTS/CTS or XOn/XOff yields cleanly when the controller's
+        /// buffer is full.
+        /// </summary>
+        public void StreamJob(byte[] data, CancellationToken cancellationToken = default)
+        {
+            if (data == null) throw new ArgumentNullException(nameof(data));
+            if (port == null || !port.IsOpen)
+                throw new InvalidOperationException("Port is not open.");
+
+            var chunk = ChunkSize > 0 ? ChunkSize : DefaultChunkSize;
+            var offset = 0;
+
+            while (offset < data.Length)
+            {
+                cancellationToken.ThrowIfCancellationRequested();
+
+                var count = System.Math.Min(chunk, data.Length - offset);
+                port.Write(data, offset, count);
+                offset += count;
+            }
+
+            // Block until the OS has handed the last bytes to the line. SerialPort
+            // doesn't expose flush-and-drain directly; BaseStream.Flush is a no-op
+            // on Windows, so this is best-effort.
+            try { port.BaseStream.Flush(); }
+            catch { /* ignored — Flush is advisory on SerialPort */ }
+        }
+
+        public void Close()
+        {
+            if (port == null) return;
+            try
+            {
+                if (port.IsOpen) port.Close();
+            }
+            finally
+            {
+                port.Dispose();
+                port = null;
+            }
+        }
+
+        public void Dispose() => Close();
+    }
+}

OpenNest.Posts.GravographIS/GravographISPostProcessor.cs

@@ -0,0 +1,61 @@
+using System;
+using System.IO;
+using System.IO.Ports;
+using System.Threading;
+
+namespace OpenNest.Posts.GravographIS
+{
+    /// <summary>
+    /// IPostProcessor implementation for the Gravograph IS8000. <see cref="Post(Nest, Stream)"/>
+    /// writes the binary HPGL bytes. For serial streaming, use <see cref="Stream(Nest, string, Handshake, CancellationToken)"/>.
+    /// </summary>
+    public sealed class GravographISPostProcessor : IPostProcessor
+    {
+        public string Name => "Gravograph IS8000";
+        public string Author => "OpenNest";
+        public string Description => "Gravograph IS8000 mechanical engraver (binary HPGL over serial)";
+
+        public GravographISWriterOptions WriterOptions { get; } = new GravographISWriterOptions();
+
+        public NestPolylineExtractor Extractor { get; } = new NestPolylineExtractor();
+
+        public double StitchTolerance { get; set; } = PolylinePrePass.DefaultStitchTolerance;
+
+        public bool AllowReverse { get; set; } = true;
+
+        public void Post(Nest nest, Stream outputStream)
+        {
+            if (nest == null) throw new ArgumentNullException(nameof(nest));
+            if (outputStream == null) throw new ArgumentNullException(nameof(outputStream));
+
+            var polylines = Extractor.Extract(nest);
+            var prepared = PolylinePrePass.Prepare(polylines, StitchTolerance, AllowReverse);
+            new GravographISWriter(WriterOptions).Write(prepared, outputStream);
+        }
+
+        public void Post(Nest nest, string outputFile)
+        {
+            using var fs = new FileStream(outputFile, FileMode.Create, FileAccess.Write);
+            Post(nest, fs);
+        }
+
+        /// <summary>
+        /// Buffers the encoded job in memory, then streams it to the named COM port.
+        /// </summary>
+        public void Stream(Nest nest, string portName,
+            Handshake handshake = Handshake.RequestToSend,
+            CancellationToken cancellationToken = default)
+        {
+            byte[] bytes;
+            using (var ms = new MemoryStream())
+            {
+                Post(nest, ms);
+                bytes = ms.ToArray();
+            }
+
+            using var port = new GravographISPort();
+            port.Open(portName, handshake);
+            port.StreamJob(bytes, cancellationToken);
+        }
+    }
+}

OpenNest.Posts.GravographIS/GravographISWriter.cs

@@ -0,0 +1,327 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
+using OpenNest.Geometry;
+
+namespace OpenNest.Posts.GravographIS
+{
+    /// <summary>
+    /// Encodes polylines (in inches) into the Gravograph IS8000 native "binary HPGL"
+    /// wire format. The byte stream is byte-exact against captures from GravoStyle'98.
+    ///
+    /// Scale: 80 steps/mm = 2032 steps/inch. Y (and Z) are negated on the wire.
+    /// Deltas are signed big-endian int16 (max ±32767 steps ≈ ±16 inches per move).
+    /// </summary>
+    public sealed class GravographISWriter
+    {
+        // 93-byte preamble — captured from GravoStyle'98 with the trailing
+        // job-specific travel block stripped. The VS, VZ and DZ operands are
+        // patched by the writer to reflect feed and depth options.
+        //
+        // The original capture ended with a DR command (FF FD 44 52 00 00)
+        // followed by three 8-byte int16 records — same format as PU/PD —
+        // that carried a chunked travel from the head's parked position to
+        // the original job's first vertex (cumulative ΔX ≈ 1", ΔY ≈ 47").
+        // Those frozen deltas have nothing to do with our job geometry, so
+        // replaying them sends the head to a fixed point regardless of where
+        // the operator set zero. Stripped for the same reason as the captured
+        // fixed return-to-home block.
+        private static readonly byte[] PreambleTemplate = new byte[]
+        {
+            0x21, 0x41, 0x53, 0x20, 0x33, 0x38, 0x3b, 0x01, 0x90, 0x01,
+            0xf4, 0x01, 0x90, 0x01, 0xf4, 0x01, 0x90, 0x01, 0xf4, 0x00,
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+            0x00, 0x00, 0x09, 0x00, 0x00, 0x03, 0xe8, 0x05, 0x06, 0x00,
+            0x00, 0x00, 0x00, 0x00, 0x00, 0xff, 0xfd, 0x32, 0x44, 0x00,
+            0x00, 0xff, 0xfd, 0x4d, 0x43, 0x00, 0x01, 0xff, 0xfd, 0x4f,
+            0x55, 0xff, 0xfb, 0xff, 0xfd, 0x4f, 0x55, 0xff, 0xfa, 0xff,
+            0xfd, 0x50, 0x5a, 0x00, 0x00, 0xff, 0xfd, 0x56, 0x53, 0x00,
+            0x23, 0xff, 0xfd, 0x56, 0x5a, 0x00, 0x23, 0xff, 0xfd, 0x44,
+            0x5a, 0x01, 0xfc,
+        };
+
+        // Stripped 36-byte postamble: lift, aux off, motor off, operator beep,
+        // job-finish. The 24-byte return-to-home block that appears in GravoStyle's
+        // captured postamble between MC and OP is intentionally OMITTED — those
+        // three 8-byte int16 records carry chunked job-specific return deltas
+        // (each record is [word1:int16][param:int16][ΔX:int16][ΔY:int16], same
+        // format as PU/PD records; the original capture chunked the long Y return
+        // across three records because each delta has to fit in int16). Reusing
+        // GravoStyle's frozen deltas on different geometry overshoots the X-axis
+        // limit. We emit calculated return deltas for the current job instead.
+        // The writer now replaces the captured fixed return block with a calculated
+        // lift + PU travel to the operator-set origin before these final commands.
+        private static readonly byte[] EndJobBytes = new byte[]
+        {
+            0xff, 0xfd, 0x4f, 0x55, 0xff, 0xfa, // OU 0xFFFA  aux off
+            0xff, 0xfd, 0x4f, 0x55, 0xff, 0xfb, // OU 0xFFFB  aux off
+            0xff, 0xfd, 0x4d, 0x43, 0x00, 0x00, // MC 0x0000  motor off
+            0xff, 0xfd, 0x4f, 0x50, 0x00, 0x00, // OP 0x0000  operator beep
+            0xff, 0xfd, 0x4a, 0x46, 0x00, 0x00, // JF 0x0000  job finish
+        };
+
+        // 80 steps/mm × 25.4 mm/in
+        internal const int StepsPerInch = 2032;
+
+        public GravographISWriterOptions Options { get; }
+
+        public GravographISWriter()
+            : this(new GravographISWriterOptions())
+        {
+        }
+
+        public GravographISWriter(GravographISWriterOptions options)
+        {
+            Options = options ?? throw new ArgumentNullException(nameof(options));
+        }
+
+        /// <summary>
+        /// Writes the full byte stream (preamble + geometry + postamble) for the given
+        /// polylines. Polyline coordinates are in inches, relative to the operator-set
+        /// work origin. The writer emits a leading DR travel to the first polyline
+        /// start before lowering for the first cut.
+        /// </summary>
+        public void Write(IEnumerable<IReadOnlyList<Vector>> polylines, Stream output)
+        {
+            if (polylines == null) throw new ArgumentNullException(nameof(polylines));
+            if (output == null) throw new ArgumentNullException(nameof(output));
+
+            var preamble = (byte[])PreambleTemplate.Clone();
+            PatchOperand(preamble, (byte)'V', (byte)'S', (short)Options.FeedMmPerSec);
+            PatchOperand(preamble, (byte)'V', (byte)'Z', (short)Options.FeedMmPerSec);
+            PatchOperand(preamble, (byte)'D', (byte)'Z', DepthInStepsAsInt16());
+            output.Write(preamble, 0, preamble.Length);
+
+            // Cumulative head position from the operator-set upper-left origin, in
+            // wire steps. The first polyline gets a leading DR travel from this
+            // origin before PD lowers for cutting. Used by the envelope guard to
+            // catch bad records before they ship to the engraver.
+            var headX = 0;
+            var headY = 0;
+            var envelopeXSteps = (int)System.Math.Round(Options.WorkEnvelopeXMm * StepsPerMm,
+                MidpointRounding.AwayFromZero);
+            var envelopeYSteps = (int)System.Math.Round(Options.WorkEnvelopeYMm * StepsPerMm,
+                MidpointRounding.AwayFromZero);
+
+            var firstPolyline = true;
+            var polyIndex = 0;
+
+            foreach (var poly in polylines)
+            {
+                polyIndex++;
+                if (poly == null || poly.Count < 2)
+                    continue;
+
+                var (startX, startY) = ToWire(poly[0]);
+                WriteTravel(output,
+                    firstPolyline ? (byte)'D' : (byte)'P',
+                    firstPolyline ? (byte)'R' : (byte)'U',
+                    checked(startX - headX), checked(startY - headY),
+                    ref headX, ref headY, envelopeXSteps, envelopeYSteps, polyIndex);
+
+                // PD command + single records-follow flag, then one record per segment.
+                output.WriteByte(0xFF);
+                output.WriteByte(0xFD);
+                output.WriteByte((byte)'P');
+                output.WriteByte((byte)'D');
+                output.WriteByte(0x00);
+                output.WriteByte(0x00);
+
+                var prevX = startX;
+                var prevY = startY;
+                for (int i = 1; i < poly.Count; i++)
+                {
+                    var (cx, cy) = ToWire(poly[i]);
+                    var dx = checked(cx - prevX);
+                    var dy = checked(cy - prevY);
+                    EnsureEnvelope(headX + dx, headY + dy, envelopeXSteps, envelopeYSteps,
+                        polyIndex, segment: i, isTravel: false);
+                    WriteRecord(output, dx, dy);
+                    prevX = cx;
+                    prevY = cy;
+                    headX += dx;
+                    headY += dy;
+                }
+
+                firstPolyline = false;
+            }
+
+            WriteLiftOnly(output);
+            if (Options.ReturnToOriginAtEnd && !firstPolyline)
+            {
+                WriteTravel(output, (byte)'P', (byte)'U',
+                    checked(-headX), checked(-headY),
+                    ref headX, ref headY, envelopeXSteps, envelopeYSteps, polyIndex);
+            }
+            output.Write(EndJobBytes, 0, EndJobBytes.Length);
+        }
+
+        private const double StepsPerMm = 80.0;
+
+        private void EnsureEnvelope(int wireX, int wireY,
+            int envXSteps, int envYSteps,
+            int polyIndex, int segment, bool isTravel)
+        {
+            if (!Options.EnvelopeGuardEnabled) return;
+
+            // Wire frame: X is identity to input; Y is negated. With the operator
+            // origin set at the upper-left of the work envelope and an OpenNest
+            // quadrant-4 plate, valid part coordinates are +X/right and -Y/down:
+            //   wireX ∈ [0, +envXSteps]
+            //   wireY ∈ [0, +envYSteps]
+            if (wireX >= 0 && wireX <= envXSteps && wireY >= 0 && wireY <= envYSteps)
+                return;
+
+            var inputX = wireX / (double)StepsPerInch;
+            var inputY = -wireY / (double)StepsPerInch;
+            var kind = isTravel ? "pen-up travel" : "cut segment";
+            throw new InvalidOperationException(
+                $"Polyline {polyIndex} {kind} (segment {segment}) would place the head at " +
+                $"({inputX:F3}\", {inputY:F3}\"), outside the {Options.WorkEnvelopeXMm}×{Options.WorkEnvelopeYMm} mm " +
+                $"work envelope from upper-left origin. Refusing to emit the record.");
+        }
+
+        private short DepthInStepsAsInt16()
+        {
+            var steps = (long)System.Math.Round(Options.DepthInches * StepsPerInch, MidpointRounding.AwayFromZero);
+            if (steps < short.MinValue || steps > short.MaxValue)
+                throw new ArgumentOutOfRangeException(nameof(Options.DepthInches), $"Depth {Options.DepthInches} in. → {steps} steps overflows int16.");
+            return (short)steps;
+        }
+
+        private static (int x, int y) ToWire(Vector v)
+        {
+            // Inches -> steps. With upper-left origin in OpenNest quadrant 4,
+            // negative input Y is down; Y is negated on the wire.
+            var x = (int)System.Math.Round(v.X * StepsPerInch, MidpointRounding.AwayFromZero);
+            var y = (int)System.Math.Round(-v.Y * StepsPerInch, MidpointRounding.AwayFromZero);
+            return (x, y);
+        }
+
+        private void WriteTravel(Stream s, byte c0, byte c1, int dx, int dy,
+            ref int headX, ref int headY,
+            int envelopeXSteps, int envelopeYSteps,
+            int polyIndex)
+        {
+            if (dx == 0 && dy == 0)
+                return;
+
+            s.WriteByte(0xFF);
+            s.WriteByte(0xFD);
+            s.WriteByte(c0);
+            s.WriteByte(c1);
+            s.WriteByte(0x00);
+            s.WriteByte(0x00);
+
+            var chunks = System.Math.Max(
+                (int)System.Math.Ceiling(System.Math.Abs(dx) / (double)short.MaxValue),
+                (int)System.Math.Ceiling(System.Math.Abs(dy) / (double)short.MaxValue));
+            if (chunks < 1) chunks = 1;
+
+            var emittedX = 0;
+            var emittedY = 0;
+            for (var i = 1; i <= chunks; i++)
+            {
+                var targetX = (int)System.Math.Round(dx * (i / (double)chunks), MidpointRounding.AwayFromZero);
+                var targetY = (int)System.Math.Round(dy * (i / (double)chunks), MidpointRounding.AwayFromZero);
+                var chunkX = checked(targetX - emittedX);
+                var chunkY = checked(targetY - emittedY);
+
+                EnsureEnvelope(headX + chunkX, headY + chunkY, envelopeXSteps, envelopeYSteps,
+                    polyIndex, segment: 0, isTravel: true);
+                WriteRecord(s, chunkX, chunkY);
+
+                emittedX = targetX;
+                emittedY = targetY;
+                headX += chunkX;
+                headY += chunkY;
+            }
+        }
+
+        private static void WriteLiftOnly(Stream s)
+        {
+            s.WriteByte(0xFF);
+            s.WriteByte(0xFD);
+            s.WriteByte((byte)'P');
+            s.WriteByte((byte)'U');
+            s.WriteByte(0x00);
+            s.WriteByte(0x01);
+        }
+
+        private static void WriteCommandWithRecord(Stream s, byte c0, byte c1, int dx, int dy)
+        {
+            s.WriteByte(0xFF);
+            s.WriteByte(0xFD);
+            s.WriteByte(c0);
+            s.WriteByte(c1);
+            // Records-follow flag (0x0000) emitted once per PU/PD packet.
+            s.WriteByte(0x00);
+            s.WriteByte(0x00);
+            WriteRecord(s, dx, dy);
+        }
+
+        private static void WriteRecord(Stream s, int dx, int dy)
+        {
+            if (dx < short.MinValue || dx > short.MaxValue ||
+                dy < short.MinValue || dy > short.MaxValue)
+            {
+                throw new InvalidOperationException(
+                    $"Move delta ({dx}, {dy}) steps overflows signed int16 — split moves upstream.");
+            }
+
+            int word1;
+            int param;
+
+            var absDx = (double)System.Math.Abs(dx);
+            var absDy = (double)System.Math.Abs(dy);
+            var len = System.Math.Sqrt(absDx * absDx + absDy * absDy);
+
+            if (len < 1.0)
+            {
+                // Zero-length lift (PU 00 01) is the dedicated form; for a record-carrying
+                // packet a true zero-length move shouldn't occur, but stay numerically safe.
+                word1 = 16384;
+                param = 1;
+            }
+            else
+            {
+                var maxAbs = System.Math.Max(absDx, absDy);
+                word1 = (int)System.Math.Round(16384.0 * maxAbs / len, MidpointRounding.AwayFromZero);
+                param = (int)System.Math.Round(len / 22.4, MidpointRounding.AwayFromZero);
+                if (param < 1) param = 1;
+                if (param > 180) param = 180;
+                if (word1 > 16384) word1 = 16384;
+            }
+
+            WriteBigEndianInt16(s, (short)word1);
+            WriteBigEndianInt16(s, (short)param);
+            WriteBigEndianInt16(s, (short)dx);
+            WriteBigEndianInt16(s, (short)dy);
+        }
+
+        private static void WriteBigEndianInt16(Stream s, short value)
+        {
+            s.WriteByte((byte)((value >> 8) & 0xFF));
+            s.WriteByte((byte)(value & 0xFF));
+        }
+
+        // Locates the operand of a command (FF FD <c0> <c1> <hi> <lo>) and overwrites it.
+        // Throws if the command isn't present — that would mean the preamble was mis-edited.
+        private static void PatchOperand(byte[] buffer, byte c0, byte c1, short value)
+        {
+            for (int i = 0; i <= buffer.Length - 6; i++)
+            {
+                if (buffer[i] == 0xFF && buffer[i + 1] == 0xFD &&
+                    buffer[i + 2] == c0 && buffer[i + 3] == c1)
+                {
+                    buffer[i + 4] = (byte)((value >> 8) & 0xFF);
+                    buffer[i + 5] = (byte)(value & 0xFF);
+                    return;
+                }
+            }
+
+            throw new InvalidOperationException(
+                $"Command '{(char)c0}{(char)c1}' not found in preamble template.");
+        }
+    }
+}

OpenNest.Posts.GravographIS/GravographISWriterOptions.cs

@@ -0,0 +1,24 @@
+namespace OpenNest.Posts.GravographIS
+{
+    public sealed class GravographISWriterOptions
+    {
+        public double DepthInches { get; set; } = 0.25;
+
+        public int FeedMmPerSec { get; set; } = 35;
+
+        // IS8000 work envelope in millimeters, from the operator-set upper-left
+        // work origin. Defaults to the catalog 0.610 m x 1.220 m bed. With an
+        // OpenNest quadrant-4 plate, motion is allowed right (+X) and down (-Y).
+        public double WorkEnvelopeXMm { get; set; } = 610.0;
+        public double WorkEnvelopeYMm { get; set; } = 1220.0;
+
+        // When true, the writer throws an InvalidOperationException naming the
+        // offending polyline and segment before any out-of-envelope record is
+        // emitted. Disable only for off-machine encoding tests.
+        public bool EnvelopeGuardEnabled { get; set; } = true;
+
+        // When true, lift at the end of the last cut and return to the
+        // operator-set origin before shutting the job down.
+        public bool ReturnToOriginAtEnd { get; set; } = true;
+    }
+}

OpenNest.Posts.GravographIS/NestPolylineExtractor.cs

@@ -0,0 +1,179 @@
+using System;
+using System.Collections.Generic;
+using OpenNest.CNC;
+using OpenNest.Geometry;
+
+namespace OpenNest.Posts.GravographIS
+{
+    /// <summary>
+    /// Lifts polylines out of an OpenNest <see cref="Nest"/> for the Gravograph
+    /// backend. Walks each <see cref="Part"/>'s <see cref="Program"/>, breaks
+    /// polylines at rapid moves, and tessellates arcs to a chord-deviation
+    /// tolerance (the wire format takes line segments only).
+    /// </summary>
+    public sealed class NestPolylineExtractor
+    {
+        public double ArcChordToleranceInches { get; set; } = 0.001;
+
+        /// <summary>
+        /// Extracts polylines from every non-cutoff part in every plate of the nest,
+        /// returning them in plate coordinates (inches).
+        /// </summary>
+        public List<List<Vector>> Extract(Nest nest)
+        {
+            if (nest == null) throw new ArgumentNullException(nameof(nest));
+
+            var result = new List<List<Vector>>();
+
+            foreach (var plate in nest.Plates)
+            {
+                foreach (var part in plate.Parts)
+                {
+                    if (part.BaseDrawing != null && part.BaseDrawing.IsCutOff)
+                        continue;
+
+                    ExtractPart(part, result);
+                }
+            }
+
+            return result;
+        }
+
+        /// <summary>
+        /// Extracts polylines for a single part. Public so callers driving the
+        /// writer directly (e.g. from a console one-off) can use it.
+        /// </summary>
+        public List<List<Vector>> ExtractPart(Part part)
+        {
+            var list = new List<List<Vector>>();
+            ExtractPart(part, list);
+            return list;
+        }
+
+        private void ExtractPart(Part part, List<List<Vector>> sink)
+        {
+            var program = part.Program;
+            if (program == null) return;
+
+            // The walk below treats Motion.EndPoint as absolute. Convert a working
+            // copy to absolute mode so G91 programs (the form OpenNest's UI writes)
+            // produce correct geometry. Cloning keeps part.Program untouched.
+            if (program.Mode == Mode.Incremental)
+            {
+                program = (Program)program.Clone();
+                program.Mode = Mode.Absolute;
+            }
+
+            var offset = part.Location;
+            var pos = new Vector(0, 0);
+            List<Vector> current = null;
+
+            foreach (var code in program.Codes)
+            {
+                if (code is Motion m && m.Suppressed)
+                    continue;
+
+                switch (code)
+                {
+                    case RapidMove rapid:
+                    {
+                        FlushCurrent(sink, ref current);
+                        pos = rapid.EndPoint;
+                        break;
+                    }
+
+                    case LinearMove linear:
+                    {
+                        if (current == null)
+                        {
+                            current = new List<Vector> { pos + offset };
+                        }
+                        var end = linear.EndPoint;
+                        current.Add(end + offset);
+                        pos = end;
+                        break;
+                    }
+
+                    case ArcMove arc:
+                    {
+                        if (current == null)
+                        {
+                            current = new List<Vector> { pos + offset };
+                        }
+                        TessellateArc(pos, arc, offset, ArcChordToleranceInches, current);
+                        pos = arc.EndPoint;
+                        break;
+                    }
+                }
+            }
+
+            FlushCurrent(sink, ref current);
+        }
+
+        private static void FlushCurrent(List<List<Vector>> sink, ref List<Vector> current)
+        {
+            if (current != null && current.Count >= 2)
+                sink.Add(current);
+            current = null;
+        }
+
+        // Sample points along an arc to within chordTol of the true curve. start is
+        // the arc's start point (current pen position), arc.CenterPoint is absolute
+        // (G-code I/J in this codebase are stored as the absolute center), arc.EndPoint
+        // is absolute end. The starting point is assumed to already be in the polyline;
+        // intermediate samples and the endpoint are appended.
+        private static void TessellateArc(Vector start, ArcMove arc, Vector offset,
+            double chordTol, List<Vector> sink)
+        {
+            var c = arc.CenterPoint;
+            var r = c.DistanceTo(start);
+            if (r < 1e-9)
+            {
+                sink.Add(arc.EndPoint + offset);
+                return;
+            }
+
+            var a0 = System.Math.Atan2(start.Y - c.Y, start.X - c.X);
+            var a1 = System.Math.Atan2(arc.EndPoint.Y - c.Y, arc.EndPoint.X - c.X);
+
+            double sweep;
+            if (arc.Rotation == RotationType.CW)
+            {
+                sweep = a0 - a1;
+                if (sweep <= 0) sweep += 2 * System.Math.PI;
+            }
+            else
+            {
+                sweep = a1 - a0;
+                if (sweep <= 0) sweep += 2 * System.Math.PI;
+            }
+
+            // Treat a near-zero sweep with coincident start/end as a full circle.
+            if (sweep < 1e-9 &&
+                System.Math.Abs(start.X - arc.EndPoint.X) < 1e-9 &&
+                System.Math.Abs(start.Y - arc.EndPoint.Y) < 1e-9)
+            {
+                sweep = 2 * System.Math.PI;
+            }
+
+            // Max angle step from chord-deviation tolerance: dev = r * (1 - cos(t/2)).
+            var maxAngleStep = 2.0 * System.Math.Acos(System.Math.Max(0.0, 1.0 - chordTol / r));
+            if (double.IsNaN(maxAngleStep) || maxAngleStep <= 0)
+                maxAngleStep = System.Math.PI / 32;
+
+            var steps = (int)System.Math.Ceiling(sweep / maxAngleStep);
+            if (steps < 1) steps = 1;
+
+            var direction = arc.Rotation == RotationType.CW ? -1.0 : 1.0;
+            for (int i = 1; i < steps; i++)
+            {
+                var t = sweep * (i / (double)steps);
+                var ang = a0 + direction * t;
+                var pt = new Vector(c.X + r * System.Math.Cos(ang), c.Y + r * System.Math.Sin(ang));
+                sink.Add(pt + offset);
+            }
+
+            sink.Add(arc.EndPoint + offset);
+        }
+    }
+}

OpenNest.Posts.GravographIS/OpenNest.Posts.GravographIS.csproj

@@ -0,0 +1,20 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <TargetFramework>net8.0-windows</TargetFramework>
+    <RootNamespace>OpenNest.Posts.GravographIS</RootNamespace>
+  </PropertyGroup>
+  <ItemGroup>
+    <ProjectReference Include="..\OpenNest.Core\OpenNest.Core.csproj" />
+    <PackageReference Include="System.IO.Ports" Version="8.0.0" />
+  </ItemGroup>
+  <ItemGroup>
+    <InternalsVisibleTo Include="OpenNest.Tests" />
+  </ItemGroup>
+  <Target Name="CopyToPostsDir" AfterTargets="Build">
+    <PropertyGroup>
+      <PostsDir>..\OpenNest\bin\$(Configuration)\$(TargetFramework)\Posts\</PostsDir>
+    </PropertyGroup>
+    <MakeDir Directories="$(PostsDir)" />
+    <Copy SourceFiles="$(TargetPath)" DestinationFolder="$(PostsDir)" SkipUnchangedFiles="true" ContinueOnError="true" />
+  </Target>
+</Project>

OpenNest.Posts.GravographIS/PolylinePrePass.cs

@@ -0,0 +1,196 @@
+using System;
+using System.Collections.Generic;
+using OpenNest.Geometry;
+
+namespace OpenNest.Posts.GravographIS
+{
+    /// <summary>
+    /// Geometry pre-pass for the Gravograph IS8000 backend. The machine is a dumb
+    /// executor — it never reorders geometry and always lifts between separate
+    /// entities — so we stitch shared-endpoint polylines together and reorder by
+    /// nearest-neighbor before encoding.
+    /// </summary>
+    public static class PolylinePrePass
+    {
+        public const double DefaultStitchTolerance = 1e-6;
+
+        /// <summary>
+        /// Joins polylines whose endpoints coincide (within <paramref name="tolerance"/>)
+        /// into single continuous polylines. Polylines with fewer than two points are
+        /// dropped. Direction is reversed as needed to make a join. Each input polyline
+        /// is copied — the inputs are not mutated.
+        /// </summary>
+        public static List<List<Vector>> Stitch(
+            IEnumerable<IReadOnlyList<Vector>> polylines,
+            double tolerance = DefaultStitchTolerance)
+        {
+            if (polylines == null) throw new ArgumentNullException(nameof(polylines));
+
+            var segs = new List<List<Vector>>();
+            foreach (var p in polylines)
+            {
+                if (p == null || p.Count < 2)
+                    continue;
+                segs.Add(new List<Vector>(p));
+            }
+
+            bool changed;
+            do
+            {
+                changed = false;
+                for (int i = 0; i < segs.Count; i++)
+                {
+                    var a = segs[i];
+
+                    for (int j = 0; j < segs.Count; j++)
+                    {
+                        if (i == j) continue;
+                        var b = segs[j];
+
+                        // a-end ↔ b-start: append b to a (skip duplicated joint)
+                        if (Near(a[a.Count - 1], b[0], tolerance))
+                        {
+                            for (int k = 1; k < b.Count; k++) a.Add(b[k]);
+                            segs.RemoveAt(j);
+                            if (j < i) i--;
+                            changed = true;
+                            break;
+                        }
+
+                        // a-end ↔ b-end: append reversed b to a
+                        if (Near(a[a.Count - 1], b[b.Count - 1], tolerance))
+                        {
+                            for (int k = b.Count - 2; k >= 0; k--) a.Add(b[k]);
+                            segs.RemoveAt(j);
+                            if (j < i) i--;
+                            changed = true;
+                            break;
+                        }
+
+                        // a-start ↔ b-end: prepend b to a
+                        if (Near(a[0], b[b.Count - 1], tolerance))
+                        {
+                            var combined = new List<Vector>(b.Count + a.Count - 1);
+                            combined.AddRange(b);
+                            for (int k = 1; k < a.Count; k++) combined.Add(a[k]);
+                            segs[i] = combined;
+                            segs.RemoveAt(j);
+                            if (j < i) i--;
+                            changed = true;
+                            break;
+                        }
+
+                        // a-start ↔ b-start: prepend reversed b to a
+                        if (Near(a[0], b[0], tolerance))
+                        {
+                            var combined = new List<Vector>(b.Count + a.Count - 1);
+                            for (int k = b.Count - 1; k >= 0; k--) combined.Add(b[k]);
+                            for (int k = 1; k < a.Count; k++) combined.Add(a[k]);
+                            segs[i] = combined;
+                            segs.RemoveAt(j);
+                            if (j < i) i--;
+                            changed = true;
+                            break;
+                        }
+                    }
+
+                    if (changed) break;
+                }
+            }
+            while (changed);
+
+            return segs;
+        }
+
+        /// <summary>
+        /// Greedy nearest-neighbor ordering of polylines starting from
+        /// <paramref name="origin"/> (defaults to 0,0 = the work origin = the first
+        /// polyline's first point on the wire). When <paramref name="allowReverse"/>
+        /// is true a polyline may be reversed if its tail is closer than its head.
+        /// </summary>
+        public static List<List<Vector>> Reorder(
+            IEnumerable<IReadOnlyList<Vector>> polylines,
+            bool allowReverse = true,
+            Vector? origin = null)
+        {
+            if (polylines == null) throw new ArgumentNullException(nameof(polylines));
+
+            var pool = new List<List<Vector>>();
+            foreach (var p in polylines)
+            {
+                if (p == null || p.Count < 2)
+                    continue;
+                pool.Add(new List<Vector>(p));
+            }
+
+            var ordered = new List<List<Vector>>(pool.Count);
+            var current = origin ?? new Vector(0, 0);
+
+            while (pool.Count > 0)
+            {
+                var bestIdx = -1;
+                var bestReverse = false;
+                var bestDistSq = double.PositiveInfinity;
+
+                for (int i = 0; i < pool.Count; i++)
+                {
+                    var p = pool[i];
+                    var dHead = SquaredDistance(current, p[0]);
+                    if (dHead < bestDistSq)
+                    {
+                        bestDistSq = dHead;
+                        bestIdx = i;
+                        bestReverse = false;
+                    }
+
+                    if (allowReverse)
+                    {
+                        var dTail = SquaredDistance(current, p[p.Count - 1]);
+                        if (dTail < bestDistSq)
+                        {
+                            bestDistSq = dTail;
+                            bestIdx = i;
+                            bestReverse = true;
+                        }
+                    }
+                }
+
+                var pick = pool[bestIdx];
+                pool.RemoveAt(bestIdx);
+                if (bestReverse)
+                    pick.Reverse();
+                ordered.Add(pick);
+                current = pick[pick.Count - 1];
+            }
+
+            return ordered;
+        }
+
+        /// <summary>
+        /// Convenience: stitch then reorder.
+        /// </summary>
+        public static List<List<Vector>> Prepare(
+            IEnumerable<IReadOnlyList<Vector>> polylines,
+            double stitchTolerance = DefaultStitchTolerance,
+            bool allowReverse = true,
+            Vector? origin = null)
+        {
+            var stitched = Stitch(polylines, stitchTolerance);
+            return Reorder(stitched, allowReverse, origin);
+        }
+
+        private static bool Near(Vector a, Vector b, double tol)
+        {
+            var dx = a.X - b.X;
+            var dy = a.Y - b.Y;
+            return (dx * dx + dy * dy) <= tol * tol;
+        }
+
+        private static double SquaredDistance(Vector a, Vector b)
+        {
+            var dx = a.X - b.X;
+            var dy = a.Y - b.Y;
+            return dx * dx + dy * dy;
+        }
+    }
+}

OpenNest.Tests/GravographIS/EnvelopeGuardTests.cs

@@ -0,0 +1,165 @@
+using System.Collections.Generic;
+using System.IO;
+using OpenNest.Geometry;
+using OpenNest.Posts.GravographIS;
+
+namespace OpenNest.Tests.GravographIS;
+
+public class EnvelopeGuardTests
+{
+    // 0.610 m / 0.0125 mm/step = 48 800 steps = 24.0157 inches
+    // 1.220 m / 0.0125 mm/step = 97 600 steps = 48.0315 inches
+
+    [Fact]
+    public void NegativeX_FromOrigin_Throws()
+    {
+        // Operator origin is upper-left; quadrant 4 walks right/down. A cut that walks
+        // left of origin in -X must be refused.
+        var polylines = new List<IReadOnlyList<Vector>>
+        {
+            new[] { new Vector(0, 0), new Vector(-1, 0) },
+        };
+
+        var ex = Assert.Throws<System.InvalidOperationException>(() =>
+        {
+            using var ms = new MemoryStream();
+            new GravographISWriter().Write(polylines, ms);
+        });
+
+        Assert.Contains("Polyline 1", ex.Message);
+        Assert.Contains("cut segment", ex.Message);
+        Assert.Contains("segment 1", ex.Message);
+    }
+
+    [Fact]
+    public void PositiveY_FromOrigin_Throws()
+    {
+        // Positive input-Y is above the upper-left origin in quadrant 4.
+        var polylines = new List<IReadOnlyList<Vector>>
+        {
+            new[] { new Vector(0, 0), new Vector(0, 1) },
+        };
+
+        var ex = Assert.Throws<System.InvalidOperationException>(() =>
+        {
+            using var ms = new MemoryStream();
+            new GravographISWriter().Write(polylines, ms);
+        });
+
+        Assert.Contains("Polyline 1", ex.Message);
+    }
+
+    [Fact]
+    public void XExceedsEnvelope_Throws_AndNamesSegment()
+    {
+        // 25" in X is past the 0.610 m (~24.02") envelope.
+        var polylines = new List<IReadOnlyList<Vector>>
+        {
+            new[] { new Vector(0, 0), new Vector(10, 0), new Vector(25, 0) },
+        };
+
+        var ex = Assert.Throws<System.InvalidOperationException>(() =>
+        {
+            using var ms = new MemoryStream();
+            new GravographISWriter().Write(polylines, ms);
+        });
+
+        Assert.Contains("Polyline 1", ex.Message);
+        Assert.Contains("segment 2", ex.Message); // 0→10 ok; 10→25 trips
+        Assert.Contains("25.000\"", ex.Message);
+    }
+
+    [Fact]
+    public void YExceedsEnvelope_Throws()
+    {
+        // -49" in Y is past the 1.220 m (~48.03") envelope.
+        var polylines = new List<IReadOnlyList<Vector>>
+        {
+            new[] { new Vector(0, 0), new Vector(0, -49) },
+        };
+
+        Assert.Throws<System.InvalidOperationException>(() =>
+        {
+            using var ms = new MemoryStream();
+            new GravographISWriter().Write(polylines, ms);
+        });
+    }
+
+    [Fact]
+    public void PenUpTravel_OutsideEnvelope_AlsoThrows_AndIsLabeledTravel()
+    {
+        // Polyline 1 ends in-envelope; the PU travel to polyline 2 leaves it.
+        var polylines = new List<IReadOnlyList<Vector>>
+        {
+            new[] { new Vector(0, 0), new Vector(1, 0) },
+            new[] { new Vector(30, 0), new Vector(30, -1) },
+        };
+
+        var ex = Assert.Throws<System.InvalidOperationException>(() =>
+        {
+            using var ms = new MemoryStream();
+            new GravographISWriter().Write(polylines, ms);
+        });
+
+        Assert.Contains("Polyline 2", ex.Message);
+        Assert.Contains("pen-up travel", ex.Message);
+    }
+
+    [Fact]
+    public void RightAtEnvelopeCorner_IsAllowed()
+    {
+        // Walk to (24", -48") in int16-sized hops (each delta < 16.1"). The
+        // catalog envelope is 24.02" × 48.03", so this lands just inside.
+        var polylines = new List<IReadOnlyList<Vector>>
+        {
+            new[]
+            {
+                new Vector(0, 0),
+                new Vector(8, -16),
+                new Vector(16, -32),
+                new Vector(24, -48),
+            },
+        };
+
+        using var ms = new MemoryStream();
+        new GravographISWriter().Write(polylines, ms); // no throw
+        Assert.True(ms.Length > 0);
+    }
+
+    [Fact]
+    public void EnvelopeGuard_CanBeDisabled_ForOffMachineEncoding()
+    {
+        var polylines = new List<IReadOnlyList<Vector>>
+        {
+            new[] { new Vector(0, 0), new Vector(-5, 0) },
+        };
+
+        var opts = new GravographISWriterOptions { EnvelopeGuardEnabled = false };
+
+        using var ms = new MemoryStream();
+        new GravographISWriter(opts).Write(polylines, ms); // no throw
+        Assert.True(ms.Length > 0);
+    }
+
+    [Fact]
+    public void CustomEnvelope_TightensTheCheck()
+    {
+        // Restrict to 1" × 1" — a 2" line in -Y now overshoots.
+        var polylines = new List<IReadOnlyList<Vector>>
+        {
+            new[] { new Vector(0, 0), new Vector(0, -2) },
+        };
+
+        var opts = new GravographISWriterOptions
+        {
+            WorkEnvelopeXMm = 25.4,
+            WorkEnvelopeYMm = 25.4,
+        };
+
+        Assert.Throws<System.InvalidOperationException>(() =>
+        {
+            using var ms = new MemoryStream();
+            new GravographISWriter(opts).Write(polylines, ms);
+        });
+    }
+}

OpenNest.Tests/GravographIS/GravographISWriterTests.cs

@@ -0,0 +1,223 @@
+using System.Collections.Generic;
+using System.IO;
+using OpenNest.Geometry;
+using OpenNest.Posts.GravographIS;
+
+namespace OpenNest.Tests.GravographIS;
+
+public class GravographISWriterTests
+{
+    // 93-byte preamble captured from GravoStyle'98 (VS/VZ=35, DZ=508 → matches defaults).
+    // The original capture ended with a DR command (FF FD 44 52) followed by three
+    // 8-byte int16 records carrying a chunked job-specific travel (~1" X, ~47" Y).
+    // Stripped from the writer (see GravographISWriter.PreambleTemplate) because
+    // those frozen deltas send the head to a fixed point regardless of the job. The
+    // writer now emits a job-specific leading DR travel from operator zero instead.
+    private const string PreambleHex =
+        "21 41 53 20 33 38 3b 01 90 01 f4 01 90 01 f4 01 90 01 f4 00 00 00 00 00 00 00 00 00 00 " +
+        "00 00 00 09 00 00 03 e8 05 06 00 00 00 00 00 00 ff fd 32 44 00 00 ff fd 4d 43 00 01 ff fd " +
+        "4f 55 ff fb ff fd 4f 55 ff fa ff fd 50 5a 00 00 ff fd 56 53 00 23 ff fd 56 5a 00 23 ff fd " +
+        "44 5a 01 fc";
+
+    // Legacy 36-byte tail with lift, aux off, motor off, operator beep, job finish.
+    // Byte-exact capture tests disable dynamic return-to-origin to preserve this form.
+    private const string PostambleHex =
+        "ff fd 50 55 00 01 ff fd 4f 55 ff fa ff fd 4f 55 ff fb ff fd 4d 43 00 00 " +
+        "ff fd 4f 50 00 00 ff fd 4a 46 00 00";
+
+    [Fact]
+    public void TestA_SingleTwoInchVerticalLine_IsByteExact()
+    {
+        var polylines = new List<IReadOnlyList<Vector>>
+        {
+            new[] { new Vector(1, 1), new Vector(1, 3) },
+        };
+
+        var writer = new GravographISWriter(new GravographISWriterOptions
+        {
+            DepthInches = 0.25,
+            FeedMmPerSec = 35,
+            EnvelopeGuardEnabled = false,
+            ReturnToOriginAtEnd = false,
+        });
+
+        using var ms = new MemoryStream();
+        writer.Write(polylines, ms);
+
+        const string GeomHex =
+            "ff fd 44 52 00 00 2d 41 00 80 07 f0 f8 10 " +
+            "ff fd 50 44 00 00 40 00 00 b4 00 00 f0 20";
+        var expected = HexToBytes(PreambleHex + " " + GeomHex + " " + PostambleHex);
+
+        Assert.Equal(expected, ms.ToArray());
+    }
+
+    [Fact]
+    public void TestB_FourLines_IsByteExact()
+    {
+        var polylines = new List<IReadOnlyList<Vector>>
+        {
+            new[] { new Vector(1, 1), new Vector(1, 3) },
+            new[] { new Vector(4, 1), new Vector(4, 3) },
+            new[] { new Vector(4, 5), new Vector(4, 7) },
+            new[] { new Vector(1, 5), new Vector(1, 7) },
+        };
+
+        var writer = new GravographISWriter(new GravographISWriterOptions
+        {
+            DepthInches = 0.25,
+            FeedMmPerSec = 35,
+            EnvelopeGuardEnabled = false,
+            ReturnToOriginAtEnd = false,
+        });
+
+        using var ms = new MemoryStream();
+        writer.Write(polylines, ms);
+
+        const string GeomHex =
+            "ff fd 44 52 00 00 2d 41 00 80 07 f0 f8 10 " +
+            "ff fd 50 44 00 00 40 00 00 b4 00 00 f0 20 " +
+            "ff fd 50 55 00 00 35 40 00 b4 17 d0 0f e0 " +
+            "ff fd 50 44 00 00 40 00 00 b4 00 00 f0 20 " +
+            "ff fd 50 55 00 00 40 00 00 b4 00 00 f0 20 " +
+            "ff fd 50 44 00 00 40 00 00 b4 00 00 f0 20 " +
+            "ff fd 50 55 00 00 35 40 00 b4 e8 30 0f e0 " +
+            "ff fd 50 44 00 00 40 00 00 b4 00 00 f0 20";
+        var expected = HexToBytes(PreambleHex + " " + GeomHex + " " + PostambleHex);
+
+        Assert.Equal(expected, ms.ToArray());
+    }
+
+    [Fact]
+    public void LeadingDR_TravelsToFirstPolylineStartBeforePD()
+    {
+        var polylines = new List<IReadOnlyList<Vector>>
+        {
+            new[] { new Vector(2, 2), new Vector(3, 2) },
+        };
+
+        using var ms = new MemoryStream();
+        new GravographISWriter(new GravographISWriterOptions { EnvelopeGuardEnabled = false }).Write(polylines, ms);
+
+        var bytes = ms.ToArray();
+        // First command after the 93-byte preamble must be DR to the first point,
+        // followed by PD for the first cut.
+        Assert.Equal(0xFF, bytes[93]);
+        Assert.Equal(0xFD, bytes[94]);
+        Assert.Equal((byte)'D', bytes[95]);
+        Assert.Equal((byte)'R', bytes[96]);
+
+        Assert.Equal(0xFF, bytes[107]);
+        Assert.Equal(0xFD, bytes[108]);
+        Assert.Equal((byte)'P', bytes[109]);
+        Assert.Equal((byte)'D', bytes[110]);
+    }
+
+    [Fact]
+    public void LeadingDR_LongTravel_IsChunked()
+    {
+        var polylines = new List<IReadOnlyList<Vector>>
+        {
+            new[] { new Vector(1, 47), new Vector(2, 47) },
+        };
+
+        using var ms = new MemoryStream();
+        new GravographISWriter(new GravographISWriterOptions { EnvelopeGuardEnabled = false }).Write(polylines, ms);
+
+        var bytes = ms.ToArray();
+        Assert.Equal((byte)'D', bytes[95]);
+        Assert.Equal((byte)'R', bytes[96]);
+        Assert.Equal((byte)'P', bytes[125]);
+        Assert.Equal((byte)'D', bytes[126]);
+    }
+
+    [Fact]
+    public void OptionsPatchVsVzDz()
+    {
+        var polylines = new List<IReadOnlyList<Vector>>
+        {
+            new[] { new Vector(0, 0), new Vector(0.5, 0) },
+        };
+
+        using var ms = new MemoryStream();
+        new GravographISWriter(new GravographISWriterOptions
+        {
+            DepthInches = 0.125,   // 254 steps = 0x00FE
+            FeedMmPerSec = 50,     // 0x0032
+        }).Write(polylines, ms);
+
+        var bytes = ms.ToArray();
+        AssertOperand(bytes, (byte)'V', (byte)'S', 0x00, 0x32);
+        AssertOperand(bytes, (byte)'V', (byte)'Z', 0x00, 0x32);
+        AssertOperand(bytes, (byte)'D', (byte)'Z', 0x00, 0xFE);
+    }
+
+    [Fact]
+    public void ReturnsToOriginAfterFinalLift_ByDefault()
+    {
+        var polylines = new List<IReadOnlyList<Vector>>
+        {
+            new[] { new Vector(0, 0), new Vector(1, 0), new Vector(1, -1) },
+        };
+
+        using var ms = new MemoryStream();
+        new GravographISWriter().Write(polylines, ms);
+
+        var bytes = ms.ToArray();
+        var liftIndex = LastIndexOfCommand(bytes, (byte)'P', (byte)'U', 0x00, 0x01);
+        Assert.True(liftIndex >= 0);
+
+        Assert.Equal(0xFF, bytes[liftIndex + 6]);
+        Assert.Equal(0xFD, bytes[liftIndex + 7]);
+        Assert.Equal((byte)'P', bytes[liftIndex + 8]);
+        Assert.Equal((byte)'U', bytes[liftIndex + 9]);
+
+        var dx = ReadInt16(bytes, liftIndex + 16);
+        var dy = ReadInt16(bytes, liftIndex + 18);
+        Assert.Equal(-GravographISWriter.StepsPerInch, dx);
+        Assert.Equal(-GravographISWriter.StepsPerInch, dy);
+    }
+
+    private static void AssertOperand(byte[] bytes, byte c0, byte c1, byte hi, byte lo)
+    {
+        for (var i = 0; i < bytes.Length - 5; i++)
+        {
+            if (bytes[i] == 0xFF && bytes[i + 1] == 0xFD && bytes[i + 2] == c0 && bytes[i + 3] == c1)
+            {
+                Assert.Equal(hi, bytes[i + 4]);
+                Assert.Equal(lo, bytes[i + 5]);
+                return;
+            }
+        }
+        Assert.Fail($"Command {(char)c0}{(char)c1} not found in stream.");
+    }
+
+    private static int LastIndexOfCommand(byte[] bytes, byte c0, byte c1, byte hi, byte lo)
+    {
+        for (var i = bytes.Length - 6; i >= 0; i--)
+        {
+            if (bytes[i] == 0xFF && bytes[i + 1] == 0xFD &&
+                bytes[i + 2] == c0 && bytes[i + 3] == c1 &&
+                bytes[i + 4] == hi && bytes[i + 5] == lo)
+            {
+                return i;
+            }
+        }
+
+        return -1;
+    }
+
+    private static short ReadInt16(byte[] bytes, int offset)
+    {
+        return unchecked((short)((bytes[offset] << 8) | bytes[offset + 1]));
+    }
+
+    internal static byte[] HexToBytes(string hex)
+    {
+        var clean = hex.Replace(" ", string.Empty).Replace("\n", string.Empty).Replace("\r", string.Empty);
+        var bytes = new byte[clean.Length / 2];
+        for (var i = 0; i < bytes.Length; i++)
+            bytes[i] = System.Convert.ToByte(clean.Substring(i * 2, 2), 16);
+        return bytes;
+    }
+}

OpenNest.Tests/GravographIS/NestPolylineExtractorTests.cs

@@ -0,0 +1,37 @@
+using OpenNest;
+using OpenNest.CNC;
+using OpenNest.Geometry;
+using OpenNest.Posts.GravographIS;
+
+namespace OpenNest.Tests.GravographIS;
+
+public class NestPolylineExtractorTests
+{
+    [Fact]
+    public void ExtractPart_IncrementalProgram_ProducesAbsoluteCoordinates()
+    {
+        // 1x1 square in G91 (incremental) mode — the form OpenNest's UI writes
+        // to .nest files. Without absolute-mode handling the extractor plotted
+        // each EndPoint as if it were absolute, producing a 2x2 diamond.
+        var program = new Program(Mode.Incremental);
+        program.Codes.Add(new RapidMove(new Vector(0, 0)));
+        program.Codes.Add(new LinearMove(1, 0));
+        program.Codes.Add(new LinearMove(0, 1));
+        program.Codes.Add(new LinearMove(-1, 0));
+        program.Codes.Add(new LinearMove(0, -1));
+
+        var drawing = new Drawing("Square 1x1", program);
+        var part = new Part(drawing, new Vector(0.25, 46.75));
+
+        var polylines = new NestPolylineExtractor().ExtractPart(part);
+
+        Assert.Single(polylines);
+        var poly = polylines[0];
+        Assert.Equal(5, poly.Count);
+        Assert.Equal(new Vector(0.25, 46.75), poly[0]);
+        Assert.Equal(new Vector(1.25, 46.75), poly[1]);
+        Assert.Equal(new Vector(1.25, 47.75), poly[2]);
+        Assert.Equal(new Vector(0.25, 47.75), poly[3]);
+        Assert.Equal(new Vector(0.25, 46.75), poly[4]);
+    }
+}

OpenNest.Tests/GravographIS/PolylinePrePassTests.cs

@@ -0,0 +1,164 @@
+using System.Collections.Generic;
+using OpenNest.Geometry;
+using OpenNest.Posts.GravographIS;
+
+namespace OpenNest.Tests.GravographIS;
+
+public class PolylinePrePassTests
+{
+    [Fact]
+    public void Stitch_TwoConnectedSegments_BecomeOnePolyline()
+    {
+        var inputs = new List<IReadOnlyList<Vector>>
+        {
+            new[] { new Vector(0, 0), new Vector(1, 0) },
+            new[] { new Vector(1, 0), new Vector(1, 1) },
+        };
+
+        var stitched = PolylinePrePass.Stitch(inputs);
+
+        Assert.Single(stitched);
+        Assert.Equal(3, stitched[0].Count);
+        Assert.Equal(new Vector(0, 0), stitched[0][0]);
+        Assert.Equal(new Vector(1, 0), stitched[0][1]);
+        Assert.Equal(new Vector(1, 1), stitched[0][2]);
+    }
+
+    [Fact]
+    public void Stitch_FourSegmentsFormingClosedSquare_BecomeOnePolyline()
+    {
+        var inputs = new List<IReadOnlyList<Vector>>
+        {
+            new[] { new Vector(0, 0), new Vector(1, 0) },
+            new[] { new Vector(1, 0), new Vector(1, 1) },
+            new[] { new Vector(1, 1), new Vector(0, 1) },
+            new[] { new Vector(0, 1), new Vector(0, 0) },
+        };
+
+        var stitched = PolylinePrePass.Stitch(inputs);
+
+        Assert.Single(stitched);
+        // Four edges + closing return-to-start = five vertices.
+        Assert.Equal(5, stitched[0].Count);
+    }
+
+    [Fact]
+    public void Stitch_ReversesOneSegmentToMakeAJoin()
+    {
+        // Second segment is given backward; stitcher should reverse it.
+        var inputs = new List<IReadOnlyList<Vector>>
+        {
+            new[] { new Vector(0, 0), new Vector(1, 0) },
+            new[] { new Vector(2, 0), new Vector(1, 0) },
+        };
+
+        var stitched = PolylinePrePass.Stitch(inputs);
+
+        Assert.Single(stitched);
+        Assert.Equal(3, stitched[0].Count);
+        Assert.Equal(new Vector(0, 0), stitched[0][0]);
+        Assert.Equal(new Vector(2, 0), stitched[0][stitched[0].Count - 1]);
+    }
+
+    [Fact]
+    public void Stitch_DisjointSegments_StayDistinct()
+    {
+        var inputs = new List<IReadOnlyList<Vector>>
+        {
+            new[] { new Vector(0, 0), new Vector(1, 0) },
+            new[] { new Vector(5, 5), new Vector(6, 5) },
+        };
+
+        var stitched = PolylinePrePass.Stitch(inputs);
+
+        Assert.Equal(2, stitched.Count);
+    }
+
+    [Fact]
+    public void Stitch_DropsZeroAndSinglePointPolylines()
+    {
+        var inputs = new List<IReadOnlyList<Vector>>
+        {
+            new Vector[] { },
+            new[] { new Vector(0, 0) },
+            new[] { new Vector(0, 0), new Vector(1, 0) },
+        };
+
+        var stitched = PolylinePrePass.Stitch(inputs);
+
+        Assert.Single(stitched);
+        Assert.Equal(2, stitched[0].Count);
+    }
+
+    [Fact]
+    public void Reorder_ReducesTotalPenUpTravelVsWorstCase()
+    {
+        // Three short polylines at (0,0), (10,0), (5,0). The greedy NN starting
+        // from origin should pick (0,0)→(5,0)→(10,0) (travels of 4 + 4 ≈ 8) over
+        // the worst-case input order (0,0)→(10,0)→(5,0) (travels 9 + 4 ≈ 13).
+        var inputs = new List<IReadOnlyList<Vector>>
+        {
+            new[] { new Vector(0, 0), new Vector(1, 0) },
+            new[] { new Vector(10, 0), new Vector(11, 0) },
+            new[] { new Vector(5, 0), new Vector(6, 0) },
+        };
+
+        var reordered = PolylinePrePass.Reorder(inputs);
+
+        Assert.Equal(3, reordered.Count);
+        var travelBefore = TotalPenUpTravel(inputs);
+        var travelAfter = TotalPenUpTravel(reordered);
+        Assert.True(travelAfter < travelBefore,
+            $"Expected reorder to reduce pen-up travel; before={travelBefore}, after={travelAfter}");
+    }
+
+    [Fact]
+    public void Reorder_ReversesPolylineIfTailIsCloser()
+    {
+        // Origin (0,0); a single polyline whose tail is much closer to origin
+        // than its head. Reorder should flip it.
+        var inputs = new List<IReadOnlyList<Vector>>
+        {
+            new[] { new Vector(10, 0), new Vector(0.5, 0) },
+        };
+
+        var reordered = PolylinePrePass.Reorder(inputs, allowReverse: true);
+
+        Assert.Single(reordered);
+        Assert.Equal(new Vector(0.5, 0), reordered[0][0]);
+        Assert.Equal(new Vector(10, 0), reordered[0][1]);
+    }
+
+    [Fact]
+    public void Reorder_ReverseDisabled_KeepsDirection()
+    {
+        var inputs = new List<IReadOnlyList<Vector>>
+        {
+            new[] { new Vector(10, 0), new Vector(0.5, 0) },
+        };
+
+        var reordered = PolylinePrePass.Reorder(inputs, allowReverse: false);
+
+        Assert.Single(reordered);
+        Assert.Equal(new Vector(10, 0), reordered[0][0]);
+        Assert.Equal(new Vector(0.5, 0), reordered[0][1]);
+    }
+
+    private static double TotalPenUpTravel(IEnumerable<IReadOnlyList<Vector>> polylines)
+    {
+        var total = 0.0;
+        Vector? last = null;
+        foreach (var p in polylines)
+        {
+            if (p == null || p.Count < 2) continue;
+            if (last.HasValue)
+            {
+                var dx = p[0].X - last.Value.X;
+                var dy = p[0].Y - last.Value.Y;
+                total += System.Math.Sqrt(dx * dx + dy * dy);
+            }
+            last = p[p.Count - 1];
+        }
+        return total;
+    }
+}

OpenNest.Tests/IO/ChrFontTests.cs

@@ -0,0 +1,180 @@
+using OpenNest.Geometry;
+using OpenNest.IO;
+
+namespace OpenNest.Tests.IO;
+
+public class ChrFontTests
+{
+    private ChrFont LoadFont()
+    {
+        var path = TestConfig.GetExistingPath("ChrFontPath");
+        Skip.If(path == null, "ChrFontPath not configured in test-config.json or file not found");
+        return ChrFont.Read(path);
+    }
+
+    [SkippableFact]
+    public void Read_ParsesFontName()
+    {
+        var font = LoadFont();
+        Assert.Equal("US BLOCK 1L", font.Name);
+    }
+
+    [SkippableFact]
+    public void Read_ParsesVersion()
+    {
+        var font = LoadFont();
+        Assert.StartsWith("C1.", font.Version);
+    }
+
+    [SkippableFact]
+    public void Read_HasAsciiGlyphs()
+    {
+        var font = LoadFont();
+        Assert.True(font.HasGlyph('A'));
+        Assert.True(font.HasGlyph('Z'));
+        Assert.True(font.HasGlyph('0'));
+        Assert.True(font.HasGlyph(' '));
+    }
+
+    [SkippableFact]
+    public void Read_HasExtendedGlyphs()
+    {
+        var font = LoadFont();
+        Assert.True(font.HasGlyph(0xC7)); // C-cedilla
+    }
+
+    [SkippableFact]
+    public void Glyph_L_ProducesLines()
+    {
+        var font = LoadFont();
+        var glyph = font.GetGlyph('L');
+        Assert.NotNull(glyph);
+
+        var entities = glyph.ToEntities(1.0, 0, 0);
+        Assert.True(entities.Count >= 2, $"Expected at least 2 entities for 'L', got {entities.Count}");
+        Assert.All(entities, e => Assert.Equal(EntityType.Line, e.Type));
+    }
+
+    [SkippableFact]
+    public void Glyph_O_ProducesEntities()
+    {
+        var font = LoadFont();
+        var glyph = font.GetGlyph('O');
+        Assert.NotNull(glyph);
+
+        var entities = glyph.ToEntities(1.0, 0, 0);
+        Assert.True(entities.Count > 0);
+    }
+
+    [SkippableFact]
+    public void RenderText_ProducesEntities()
+    {
+        var font = LoadFont();
+        var entities = font.RenderText("HELLO", 1.0, new Vector(0, 0));
+        Assert.True(entities.Count > 0, "RenderText should produce entities");
+    }
+
+    [SkippableFact]
+    public void RenderText_ScalesCorrectly()
+    {
+        var font = LoadFont();
+
+        var small = font.RenderText("A", 0.5, Vector.Zero);
+        var large = font.RenderText("A", 2.0, Vector.Zero);
+
+        var smallBox = small.GetBoundingBox();
+        var largeBox = large.GetBoundingBox();
+
+        Assert.True(largeBox.Width > smallBox.Width);
+        Assert.True(largeBox.Length > smallBox.Length);
+    }
+
+    [SkippableFact]
+    public void RenderText_AdvancesCursor()
+    {
+        var font = LoadFont();
+        var abEntities = font.RenderText("AB", 1.0, Vector.Zero);
+        var aEntities = font.RenderText("A", 1.0, Vector.Zero);
+
+        var abBox = abEntities.GetBoundingBox();
+        var aBox = aEntities.GetBoundingBox();
+
+        Assert.True(abBox.Length > aBox.Length * 1.5,
+            $"AB width ({abBox.Length:F1}) should be significantly wider than A width ({aBox.Length:F1})");
+    }
+
+    [SkippableFact]
+    public void RenderText_MatchesGravographReference()
+    {
+        var font = LoadFont();
+
+        var height = 5.08;
+        var centerX = 50.8;
+        var centerY = 34.925;
+
+        var entities = font.RenderText("Text", height, Vector.Zero);
+        var rawBox = entities.GetBoundingBox();
+        var shiftX = centerX - (rawBox.Left + rawBox.Right) / 2;
+        var shiftY = centerY - (rawBox.Top + rawBox.Bottom) / 2;
+        foreach (var e in entities)
+            e.Offset(new Vector(shiftX, shiftY));
+        Assert.True(entities.Count > 0, "Should produce entities for 'Text'");
+
+        var box = entities.GetBoundingBox();
+
+        var refLeft = 43.53;
+        var refRight = 58.07;
+        var refBottom = 32.39;
+        var refTop = 37.47;
+
+        var tolerance = 0.5;
+
+        Assert.True(System.Math.Abs(box.Left - refLeft) < tolerance,
+            $"Left: ours={box.Left:F2}, ref={refLeft:F2}, diff={System.Math.Abs(box.Left - refLeft):F2}");
+        Assert.True(System.Math.Abs(box.Right - refRight) < tolerance,
+            $"Right: ours={box.Right:F2}, ref={refRight:F2}, diff={System.Math.Abs(box.Right - refRight):F2}");
+        Assert.True(System.Math.Abs(box.Bottom - refBottom) < tolerance,
+            $"Bottom: ours={box.Bottom:F2}, ref={refBottom:F2}, diff={System.Math.Abs(box.Bottom - refBottom):F2}");
+        Assert.True(System.Math.Abs(box.Top - refTop) < tolerance,
+            $"Top: ours={box.Top:F2}, ref={refTop:F2}, diff={System.Math.Abs(box.Top - refTop):F2}");
+
+        var actualCapHeight = box.Top - box.Bottom;
+        Assert.True(System.Math.Abs(actualCapHeight - height) < 0.5,
+            $"Cap height: ours={actualCapHeight:F2}, expected={height:F2}");
+    }
+
+    [SkippableFact]
+    public void MeasureTextWidth_IsConsistent()
+    {
+        var font = LoadFont();
+        var height = 5.08;
+        var measuredWidth = font.MeasureTextWidth("Text", height);
+        var entities = font.RenderText("Text", height, Vector.Zero);
+        var box = entities.GetBoundingBox();
+
+        Assert.True(measuredWidth >= box.Length,
+            $"Measured={measuredWidth:F2} should be >= rendered={box.Length:F2}");
+        Assert.True(measuredWidth - box.Length < 2.0,
+            $"Measured={measuredWidth:F2}, rendered={box.Length:F2}, diff={measuredWidth - box.Length:F2}");
+    }
+
+    [SkippableFact]
+    public void Glyph_t_HasCurveAtBottom()
+    {
+        var font = LoadFont();
+        var glyph = font.GetGlyph('t');
+        Assert.NotNull(glyph);
+
+        var entities = glyph.ToEntities(1.0, 0, 0);
+        var lines = entities.Cast<Line>().ToList();
+
+        Assert.True(lines.Count >= 10, $"Expected at least 10 entities for 't', got {lines.Count}");
+
+        var curveLines = lines.Skip(1).Take(lines.Count - 3).ToList();
+        Assert.True(curveLines.Count >= 14, $"Expected at least 14 curve segments, got {curveLines.Count}");
+
+        var lastCurve = curveLines[^1];
+        Assert.True(lastCurve.EndPoint.X > curveLines[0].StartPoint.X,
+            $"Curve should end to the right of where it starts: start X={curveLines[0].StartPoint.X:F1}, end X={lastCurve.EndPoint.X:F1}");
+    }
+}

OpenNest.Tests/OpenNest.Tests.csproj

@@ -14,6 +14,7 @@
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.8.0" />
     <PackageReference Include="xunit" Version="2.5.3" />
     <PackageReference Include="xunit.runner.visualstudio" Version="2.5.3" />
+    <PackageReference Include="Xunit.SkippableFact" Version="1.4.13" />
   </ItemGroup>
 
   <ItemGroup>
@@ -27,6 +28,7 @@
     <ProjectReference Include="..\OpenNest.Engine\OpenNest.Engine.csproj" />
     <ProjectReference Include="..\OpenNest.IO\OpenNest.IO.csproj" />
     <ProjectReference Include="..\OpenNest.Posts.Cincinnati\OpenNest.Posts.Cincinnati.csproj" />
+    <ProjectReference Include="..\OpenNest.Posts.GravographIS\OpenNest.Posts.GravographIS.csproj" />
     <ProjectReference Include="..\OpenNest\OpenNest.csproj" />
   </ItemGroup>
 
@@ -37,6 +39,9 @@
     <Content Include="Splitting\TestData\**\*">
       <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
     </Content>
+    <Content Include="test-config.json" Condition="Exists('test-config.json')">
+      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
+    </Content>
   </ItemGroup>
 
 </Project>

OpenNest.Tests/TestHelpers.cs

@@ -1,8 +1,37 @@
+using System.Text.Json;
 using OpenNest.CNC;
 using OpenNest.Geometry;
 
 namespace OpenNest.Tests;
 
+internal static class TestConfig
+{
+    private static readonly Lazy<Dictionary<string, string>> Config = new(() =>
+    {
+        var dir = AppContext.BaseDirectory;
+        for (var i = 0; i < 6; i++)
+        {
+            var path = Path.Combine(dir, "test-config.json");
+            if (File.Exists(path))
+            {
+                var json = File.ReadAllText(path);
+                return JsonSerializer.Deserialize<Dictionary<string, string>>(json) ?? new();
+            }
+            dir = Path.GetDirectoryName(dir)!;
+        }
+        return new();
+    });
+
+    public static string? Get(string key) =>
+        Config.Value.TryGetValue(key, out var val) ? val : null;
+
+    public static string? GetExistingPath(string key)
+    {
+        var path = Get(key);
+        return path != null && File.Exists(path) ? path : null;
+    }
+}
+
 internal static class TestHelpers
 {
     public static Part MakePartAt(double x, double y, double size = 1)

OpenNest.sln

@@ -30,6 +30,8 @@ Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "PostProcessors", "PostProce
 EndProject
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "OpenNest.Posts.Cincinnati", "OpenNest.Posts.Cincinnati\OpenNest.Posts.Cincinnati.csproj", "{FB1B2EB2-9D80-4499-BA93-B4E2F295A532}"
 EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "OpenNest.Posts.GravographIS", "OpenNest.Posts.GravographIS\OpenNest.Posts.GravographIS.csproj", "{3A6B8E7E-9B5F-4D2C-8AE3-2C9F5E3D1A40}"
+EndProject
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "OpenNest.Data", "OpenNest.Data\OpenNest.Data.csproj", "{A0B4B48E-1DF0-4DD3-B42C-B9B7779EA8B0}"
 EndProject
 Global
@@ -186,12 +188,25 @@ Global
 		{A0B4B48E-1DF0-4DD3-B42C-B9B7779EA8B0}.Release|x64.Build.0 = Release|Any CPU
 		{A0B4B48E-1DF0-4DD3-B42C-B9B7779EA8B0}.Release|x86.ActiveCfg = Release|Any CPU
 		{A0B4B48E-1DF0-4DD3-B42C-B9B7779EA8B0}.Release|x86.Build.0 = Release|Any CPU
+		{3A6B8E7E-9B5F-4D2C-8AE3-2C9F5E3D1A40}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{3A6B8E7E-9B5F-4D2C-8AE3-2C9F5E3D1A40}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{3A6B8E7E-9B5F-4D2C-8AE3-2C9F5E3D1A40}.Debug|x64.ActiveCfg = Debug|Any CPU
+		{3A6B8E7E-9B5F-4D2C-8AE3-2C9F5E3D1A40}.Debug|x64.Build.0 = Debug|Any CPU
+		{3A6B8E7E-9B5F-4D2C-8AE3-2C9F5E3D1A40}.Debug|x86.ActiveCfg = Debug|Any CPU
+		{3A6B8E7E-9B5F-4D2C-8AE3-2C9F5E3D1A40}.Debug|x86.Build.0 = Debug|Any CPU
+		{3A6B8E7E-9B5F-4D2C-8AE3-2C9F5E3D1A40}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{3A6B8E7E-9B5F-4D2C-8AE3-2C9F5E3D1A40}.Release|Any CPU.Build.0 = Release|Any CPU
+		{3A6B8E7E-9B5F-4D2C-8AE3-2C9F5E3D1A40}.Release|x64.ActiveCfg = Release|Any CPU
+		{3A6B8E7E-9B5F-4D2C-8AE3-2C9F5E3D1A40}.Release|x64.Build.0 = Release|Any CPU
+		{3A6B8E7E-9B5F-4D2C-8AE3-2C9F5E3D1A40}.Release|x86.ActiveCfg = Release|Any CPU
+		{3A6B8E7E-9B5F-4D2C-8AE3-2C9F5E3D1A40}.Release|x86.Build.0 = Release|Any CPU
 	EndGlobalSection
 	GlobalSection(SolutionProperties) = preSolution
 		HideSolutionNode = FALSE
 	EndGlobalSection
 	GlobalSection(NestedProjects) = preSolution
 		{FB1B2EB2-9D80-4499-BA93-B4E2F295A532} = {4052CFAC-1F12-48BE-872D-F503C3B65D7E}
+		{3A6B8E7E-9B5F-4D2C-8AE3-2C9F5E3D1A40} = {4052CFAC-1F12-48BE-872D-F503C3B65D7E}
 	EndGlobalSection
 	GlobalSection(ExtensibilityGlobals) = postSolution
 		SolutionGuid = {86FE17B3-F764-40AE-BCAA-F26B470CA05C}

OpenNest/Controls/EntityView.cs

@@ -40,6 +40,7 @@ namespace OpenNest.Controls
 
         public event EventHandler<Line> LinePicked;
         public event EventHandler PickCancelled;
+        public event EventHandler<CadText> TextConvertRequested;
 
         private bool isPickingBendLine;
         public bool IsPickingBendLine
@@ -76,6 +77,13 @@ namespace OpenNest.Controls
                 if (line != null)
                     LinePicked?.Invoke(this, line);
             }
+
+            if (e.Button == MouseButtons.Right)
+            {
+                var text = HitTestText(e.Location);
+                if (text != null)
+                    ShowTextContextMenu(text, e.Location);
+            }
         }
 
         protected override void OnPaint(PaintEventArgs e)
@@ -328,6 +336,41 @@ namespace OpenNest.Controls
             return bestLine;
         }
 
+        private CadText HitTestText(Point controlPoint)
+        {
+            if (Texts == null || Texts.Count == 0)
+                return null;
+
+            var worldPoint = PointControlToWorld(controlPoint);
+            var tolerance = LengthGuiToWorld(8);
+
+            foreach (var text in Texts)
+            {
+                if (string.IsNullOrEmpty(text.Value))
+                    continue;
+
+                var estimatedWidth = text.Height * text.Value.Length * 0.6;
+                var minX = text.Position.X - tolerance;
+                var maxX = text.Position.X + estimatedWidth + tolerance;
+                var minY = text.Position.Y - tolerance;
+                var maxY = text.Position.Y + text.Height + tolerance;
+
+                if (worldPoint.X >= minX && worldPoint.X <= maxX &&
+                    worldPoint.Y >= minY && worldPoint.Y <= maxY)
+                    return text;
+            }
+
+            return null;
+        }
+
+        private void ShowTextContextMenu(CadText text, Point location)
+        {
+            var menu = new ContextMenuStrip();
+            var item = menu.Items.Add($"Convert \"{text.Value}\" to Geometry");
+            item.Click += (s, e) => TextConvertRequested?.Invoke(this, text);
+            menu.Show(this, location);
+        }
+
         private void DrawEntityLabels(Graphics g)
         {
             for (var i = 0; i < Entities.Count; i++)

OpenNest/Forms/CadConverterForm.cs

@@ -45,6 +45,7 @@ namespace OpenNest.Forms
             filterPanel.AddBendLineClicked += OnAddBendLineClicked;
             entityView1.LinePicked += OnLinePicked;
             entityView1.PickCancelled += OnPickCancelled;
+            entityView1.TextConvertRequested += OnTextConvertRequested;
             btnSplit.Click += OnSplitClicked;
             numQuantity.ValueChanged += OnQuantityChanged;
             txtCustomer.TextChanged += OnCustomerChanged;
@@ -463,6 +464,115 @@ namespace OpenNest.Forms
             filterPanel.SetPickMode(false);
         }
 
+        private void OnTextConvertRequested(object sender, Controls.CadText text)
+        {
+            var item = CurrentItem;
+            if (item == null) return;
+
+            var font = LoadChrFont();
+            if (font == null) return;
+
+            var layer = new Geometry.Layer("ENGRAVE")
+            {
+                Color = System.Drawing.Color.Cyan,
+                IsVisible = true,
+            };
+
+            var entities = font.RenderText(text.Value, text.Height, Geometry.Vector.Zero, layer);
+            if (entities.Count > 0)
+            {
+                var box = entities.GetBoundingBox();
+                var shiftX = text.HAlign switch
+                {
+                    System.Drawing.StringAlignment.Center => text.Position.X - (box.Left + box.Right) / 2,
+                    System.Drawing.StringAlignment.Far => text.Position.X - box.Right,
+                    _ => text.Position.X - box.Left,
+                };
+                var shiftY = text.VAlign switch
+                {
+                    System.Drawing.StringAlignment.Center => text.Position.Y - (box.Top + box.Bottom) / 2,
+                    System.Drawing.StringAlignment.Near => text.Position.Y - box.Top,
+                    _ => text.Position.Y - box.Bottom,
+                };
+                var shift = new Geometry.Vector(shiftX, shiftY);
+                foreach (var e in entities)
+                    e.Offset(shift);
+            }
+            if (entities.Count == 0)
+            {
+                MessageBox.Show($"No geometry produced for \"{text.Value}\".", "Convert Text",
+                    MessageBoxButtons.OK, MessageBoxIcon.Information);
+                return;
+            }
+
+            item.Entities.AddRange(entities);
+            item.Texts.Remove(text);
+            item.EntityCount = item.Entities.Count;
+            item.Bounds = item.Entities.GetBoundingBox();
+
+            entityView1.Entities.Clear();
+            entityView1.Entities.AddRange(item.Entities);
+            entityView1.Texts = item.Texts;
+            filterPanel.LoadItem(item.Entities, item.Bends);
+            entityView1.Invalidate();
+            staleProgram = true;
+            lblEntityCount.Text = $"{item.EntityCount} entities";
+        }
+
+        private ChrFont cachedChrFont;
+        private string cachedChrFontPath;
+
+        private ChrFont LoadChrFont()
+        {
+            if (cachedChrFont != null)
+                return cachedChrFont;
+
+            // Look for .CHR files next to the app, then prompt
+            var appDir = System.IO.Path.GetDirectoryName(Application.ExecutablePath);
+            var candidates = Directory.GetFiles(appDir, "*.CHR", SearchOption.TopDirectoryOnly);
+
+            string fontPath;
+            if (candidates.Length == 1)
+            {
+                fontPath = candidates[0];
+            }
+            else if (candidates.Length > 1)
+            {
+                fontPath = PromptForChrFile(appDir);
+            }
+            else
+            {
+                fontPath = PromptForChrFile(null);
+            }
+
+            if (fontPath == null)
+                return null;
+
+            try
+            {
+                cachedChrFont = ChrFont.Read(fontPath);
+                cachedChrFontPath = fontPath;
+                return cachedChrFont;
+            }
+            catch (Exception ex)
+            {
+                MessageBox.Show($"Error loading font: {ex.Message}", "Font Error",
+                    MessageBoxButtons.OK, MessageBoxIcon.Error);
+                return null;
+            }
+        }
+
+        private static string PromptForChrFile(string initialDir)
+        {
+            using var dlg = new OpenFileDialog
+            {
+                Title = "Select Engraving Font (.CHR)",
+                Filter = "Gravograph Font (*.CHR)|*.CHR",
+                InitialDirectory = initialDir ?? "",
+            };
+            return dlg.ShowDialog() == DialogResult.OK ? dlg.FileName : null;
+        }
+
         private void OnDragEnter(object sender, DragEventArgs e)
         {
             if (e.Data.GetDataPresent(DataFormats.FileDrop))
@@ -839,6 +949,13 @@ namespace OpenNest.Forms
                             ACadSharp.Entities.TextHorizontalAlignment.Right => System.Drawing.StringAlignment.Far,
                             _ => System.Drawing.StringAlignment.Near,
                         };
+                        var va = text.VerticalAlignment switch
+                        {
+                            ACadSharp.Entities.TextVerticalAlignmentType.Middle => System.Drawing.StringAlignment.Center,
+                            ACadSharp.Entities.TextVerticalAlignmentType.Top => System.Drawing.StringAlignment.Near,
+                            ACadSharp.Entities.TextVerticalAlignmentType.Bottom => System.Drawing.StringAlignment.Far,
+                            _ => System.Drawing.StringAlignment.Far,
+                        };
                         texts.Add(new CadText
                         {
                             Position = new Vector(pt.X, pt.Y),
@@ -847,6 +964,7 @@ namespace OpenNest.Forms
                             Rotation = text.Rotation,
                             LayerName = text.Layer?.Name,
                             HAlign = ha,
+                            VAlign = va,
                         });
                         break;
                 }

tools/StreamGravographJob/Program.cs

@@ -0,0 +1,266 @@
+using System;
+using System.ComponentModel;
+using System.Diagnostics;
+using System.IO;
+using System.IO.Ports;
+using System.Runtime.InteropServices;
+using System.Threading;
+using Microsoft.Win32.SafeHandles;
+
+if (args.Length < 2)
+{
+    Console.Error.WriteLine("Usage:");
+    Console.Error.WriteLine("  StreamGravographJob <file.prn>   <COMx> [chunk=256] [flow=rtscts|xonxoff|none]");
+    Console.Error.WriteLine("  StreamGravographJob --gen <name> <outfile.prn>      # name: testA | testB | miniB | miniSquare");
+    Console.Error.WriteLine("  StreamGravographJob --inspect-nest <file.nest>");
+    Console.Error.WriteLine("  StreamGravographJob --from-nest    <file.nest> <outfile.prn>");
+    return 2;
+}
+
+// Inspect a .nest file: extract polylines via the post-processor pipeline and
+// report dimensions / bounding box / pen-up travel — no bytes written.
+if (args[0] == "--inspect-nest")
+{
+    if (args.Length < 2) { Console.Error.WriteLine("--inspect-nest requires <file.nest>"); return 2; }
+    var nestPath = args[1];
+    if (!File.Exists(nestPath)) { Console.Error.WriteLine($"Not found: {nestPath}"); return 3; }
+
+    using var fs = new FileStream(nestPath, FileMode.Open, FileAccess.Read);
+    var reader = new OpenNest.IO.NestReader(fs);
+    var nest = reader.Read();
+
+    Console.WriteLine($"Nest: {nest.Name}");
+    Console.WriteLine($"Units: {nest.Units}");
+    Console.WriteLine($"Plates: {nest.Plates.Count}");
+    var plateIdx = 0;
+    foreach (var plate in nest.Plates)
+    {
+        plateIdx++;
+        Console.WriteLine($"  Plate {plateIdx}: size={plate.Size.Length} x {plate.Size.Width}, quadrant={plate.Quadrant}, parts={plate.Parts.Count}");
+    }
+
+    var polylines = new OpenNest.Posts.GravographIS.NestPolylineExtractor().Extract(nest);
+    if (polylines.Count == 0)
+    {
+        Console.WriteLine("No polylines extracted.");
+        return 0;
+    }
+
+    double minX = double.PositiveInfinity, minY = double.PositiveInfinity;
+    double maxX = double.NegativeInfinity, maxY = double.NegativeInfinity;
+    int totalPts = 0;
+    foreach (var p in polylines)
+    {
+        foreach (var v in p)
+        {
+            if (v.X < minX) minX = v.X;
+            if (v.X > maxX) maxX = v.X;
+            if (v.Y < minY) minY = v.Y;
+            if (v.Y > maxY) maxY = v.Y;
+        }
+        totalPts += p.Count;
+    }
+    Console.WriteLine($"Polylines: {polylines.Count}, total points: {totalPts}");
+    Console.WriteLine($"Bounding box (inches): X ∈ [{minX:F3}, {maxX:F3}]  Y ∈ [{minY:F3}, {maxY:F3}]");
+    Console.WriteLine($"Extents: {maxX - minX:F3}\" × {maxY - minY:F3}\"");
+
+    // After running the pre-pass (stitch + reorder from origin) — what the writer will actually consume.
+    var prepared = OpenNest.Posts.GravographIS.PolylinePrePass.Prepare(polylines);
+    Console.WriteLine($"After stitch+reorder: {prepared.Count} polylines");
+
+    Console.WriteLine();
+    Console.WriteLine("--- Vertex dump (prepared, upper-left origin, with segment deltas) ---");
+    var pi = 0;
+    foreach (var poly in prepared)
+    {
+        pi++;
+        Console.WriteLine($"Polyline {pi}: {poly.Count} points");
+        var cumX = 0.0; var cumY = 0.0;
+        for (var i = 0; i < poly.Count; i++)
+        {
+            var v = poly[i];
+            if (i == 0)
+            {
+                Console.WriteLine($"  [{i}] ({v.X,7:F3}, {v.Y,7:F3})   first DR travel from upper-left origin=({v.X,+7:F3}, {v.Y,+7:F3})");
+            }
+            else
+            {
+                var dx = v.X - poly[i - 1].X;
+                var dy = v.Y - poly[i - 1].Y;
+                cumX += dx;
+                cumY += dy;
+                Console.WriteLine($"  [{i}] ({v.X,7:F3}, {v.Y,7:F3})   Δ=({dx,+7:F3}, {dy,+7:F3})   cum from origin=({cumX,+7:F3}, {cumY,+7:F3})");
+            }
+        }
+    }
+    return 0;
+}
+
+// Convert a .nest file to a .prn job via the full post-processor pipeline.
+if (args[0] == "--from-nest")
+{
+    if (args.Length < 3) { Console.Error.WriteLine("--from-nest requires <file.nest> <outfile.prn>"); return 2; }
+    var nestPath = args[1];
+    var outFile = args[2];
+    if (!File.Exists(nestPath)) { Console.Error.WriteLine($"Not found: {nestPath}"); return 3; }
+
+    using var fs = new FileStream(nestPath, FileMode.Open, FileAccess.Read);
+    var nest = new OpenNest.IO.NestReader(fs).Read();
+    var post = new OpenNest.Posts.GravographIS.GravographISPostProcessor();
+    post.Post(nest, outFile);
+
+    var size = new FileInfo(outFile).Length;
+    Console.WriteLine($"Wrote {size} bytes → {outFile}");
+    return 0;
+}
+
+// Generator mode: run the live writer to produce a captured-test file on disk.
+if (args[0] == "--gen")
+{
+    if (args.Length < 3) { Console.Error.WriteLine("--gen requires <name> <outfile>"); return 2; }
+    var preset = args[1];
+    var outFile = args[2];
+    var polylines = preset.ToLowerInvariant() switch
+    {
+        "testa" => new System.Collections.Generic.List<System.Collections.Generic.IReadOnlyList<OpenNest.Geometry.Vector>>
+        {
+            new[] { new OpenNest.Geometry.Vector(1, 1), new OpenNest.Geometry.Vector(1, 3) },
+        },
+        "testb" => new System.Collections.Generic.List<System.Collections.Generic.IReadOnlyList<OpenNest.Geometry.Vector>>
+        {
+            new[] { new OpenNest.Geometry.Vector(1, 1), new OpenNest.Geometry.Vector(1, 3) },
+            new[] { new OpenNest.Geometry.Vector(4, 1), new OpenNest.Geometry.Vector(4, 3) },
+            new[] { new OpenNest.Geometry.Vector(4, 5), new OpenNest.Geometry.Vector(4, 7) },
+            new[] { new OpenNest.Geometry.Vector(1, 5), new OpenNest.Geometry.Vector(1, 7) },
+        },
+        // Same 4-polyline topology as testB (vertical lines + diagonal PU travels between them),
+        // shrunk to a 0.5" × 1.5" footprint so it stays right near the operator-set work origin.
+        "minib" => new System.Collections.Generic.List<System.Collections.Generic.IReadOnlyList<OpenNest.Geometry.Vector>>
+        {
+            new[] { new OpenNest.Geometry.Vector(0,   0),   new OpenNest.Geometry.Vector(0,   0.5) },
+            new[] { new OpenNest.Geometry.Vector(0.5, 0),   new OpenNest.Geometry.Vector(0.5, 0.5) },
+            new[] { new OpenNest.Geometry.Vector(0.5, 1),   new OpenNest.Geometry.Vector(0.5, 1.5) },
+            new[] { new OpenNest.Geometry.Vector(0,   1),   new OpenNest.Geometry.Vector(0,   1.5) },
+        },
+        // Closed 0.5" square as a SINGLE polyline of 5 points → 4-segment PD packet.
+        // Exercises multi-segment PD (one FF FD 50 44 00 00 followed by 4 records,
+        // no intermediate lifts) and bi-directional motion (X+, Y+, X−, Y−).
+        // Returns the head to its starting point so no manual jog needed after.
+        "minisquare" => new System.Collections.Generic.List<System.Collections.Generic.IReadOnlyList<OpenNest.Geometry.Vector>>
+        {
+            new[]
+            {
+                new OpenNest.Geometry.Vector(0,    0),
+                new OpenNest.Geometry.Vector(0.5,  0),
+                new OpenNest.Geometry.Vector(0.5,  0.5),
+                new OpenNest.Geometry.Vector(0,    0.5),
+                new OpenNest.Geometry.Vector(0,    0),
+            },
+        },
+        _ => throw new ArgumentException($"Unknown preset '{preset}' (try testA, testB, miniB, or miniSquare)."),
+    };
+
+    using var outFs = new FileStream(outFile, FileMode.Create, FileAccess.Write);
+    new OpenNest.Posts.GravographIS.GravographISWriter().Write(polylines, outFs);
+    Console.WriteLine($"Wrote {new FileInfo(outFile).Length} bytes via live writer → {outFile}");
+    return 0;
+}
+
+var file = args[0];
+var portName = args[1];
+var chunk = args.Length > 2 ? int.Parse(args[2]) : 256;
+var flowArg = args.Length > 3 ? args[3] : "rtscts";
+
+var handshake = flowArg.ToLowerInvariant() switch
+{
+    "rtscts" or "rts" or "cts" => Handshake.RequestToSend,
+    "xonxoff" or "xon" or "xoff" => Handshake.XOnXOff,
+    "none" => Handshake.None,
+    _ => throw new ArgumentException($"Unknown flow control '{flowArg}'."),
+};
+
+if (!File.Exists(file))
+{
+    Console.Error.WriteLine($"File not found: {file}");
+    return 3;
+}
+
+var bytes = File.ReadAllBytes(file);
+Console.WriteLine($"File: {file}");
+Console.WriteLine($"Size: {bytes.Length} bytes");
+Console.WriteLine($"Header: {BitConverter.ToString(bytes, 0, Math.Min(7, bytes.Length)).Replace('-', ' ')}");
+
+var ports = SerialPort.GetPortNames();
+Array.Sort(ports);
+Console.WriteLine($"Available COM ports: {string.Join(", ", ports)}");
+if (Array.IndexOf(ports, portName) < 0)
+{
+    Console.Error.WriteLine($"{portName} not in available ports.");
+    return 4;
+}
+
+using var port = new SerialPort(portName, 9600, Parity.None, 8, StopBits.One)
+{
+    Handshake = handshake,
+    WriteTimeout = 30000,
+    ReadTimeout = 30000,
+    WriteBufferSize = 4096,
+    DtrEnable = true,
+};
+
+// Probe with the same CreateFile flags SerialStream uses, in this same process,
+// so we can tell SerialStream-specific failures apart from process-level access denials.
+{
+    const uint GENERIC_RW = 0x80000000u | 0x40000000u;
+    const uint OPEN_EXISTING = 3;
+    const uint FILE_FLAG_OVERLAPPED = 0x40000000u;
+    var devName = @"\\.\" + portName;
+    var handle = NativeMethods.CreateFileW(devName, GENERIC_RW, 0, IntPtr.Zero, OPEN_EXISTING, FILE_FLAG_OVERLAPPED, IntPtr.Zero);
+    var err = Marshal.GetLastWin32Error();
+    if (handle.IsInvalid)
+    {
+        Console.WriteLine($"CreateFile(\"{devName}\", overlapped, exclusive) FAILED: win32={err} ({new Win32Exception(err).Message})");
+    }
+    else
+    {
+        Console.WriteLine($"CreateFile(\"{devName}\", overlapped, exclusive) OK — closing.");
+        handle.Close();
+    }
+}
+
+Console.WriteLine($"Opening {portName} 9600 8N1 handshake={handshake}...");
+port.Open();
+Console.WriteLine("Opened.");
+
+var sw = Stopwatch.StartNew();
+try
+{
+    for (var i = 0; i < bytes.Length; i += chunk)
+    {
+        var n = Math.Min(chunk, bytes.Length - i);
+        port.Write(bytes, i, n);
+    }
+    try { port.BaseStream.Flush(); } catch { /* advisory */ }
+    Thread.Sleep(500);
+}
+finally
+{
+    sw.Stop();
+    port.Close();
+}
+
+Console.WriteLine($"Sent {bytes.Length} bytes in {sw.ElapsedMilliseconds} ms. Port closed.");
+return 0;
+
+internal static class NativeMethods
+{
+    [DllImport("kernel32.dll", SetLastError = true, CharSet = CharSet.Unicode, EntryPoint = "CreateFileW")]
+    internal static extern SafeFileHandle CreateFileW(
+        string lpFileName,
+        uint dwDesiredAccess,
+        uint dwShareMode,
+        IntPtr lpSecurityAttributes,
+        uint dwCreationDisposition,
+        uint dwFlagsAndAttributes,
+        IntPtr hTemplateFile);
+}

tools/StreamGravographJob/StreamGravographJob.csproj

@@ -0,0 +1,14 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net8.0-windows</TargetFramework>
+    <Nullable>enable</Nullable>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <RootNamespace>OpenNest.Tools.StreamGravographJob</RootNamespace>
+  </PropertyGroup>
+  <ItemGroup>
+    <PackageReference Include="System.IO.Ports" Version="8.0.0" />
+    <ProjectReference Include="..\..\OpenNest.Posts.GravographIS\OpenNest.Posts.GravographIS.csproj" />
+    <ProjectReference Include="..\..\OpenNest.IO\OpenNest.IO.csproj" />
+  </ItemGroup>
+</Project>