fix: improve arc-tangency fitting and add layered engrave/cut passes for GravographIS

GeometrySimplifier/ArcFit now fit arcs that pass exactly through run
endpoints while balancing tangency error between trusted and estimated
directions, fixing arcs that previously bulged or broke tangent
continuity at fillet/compound-curve junctions.

GravographIS post processor gains per-layer (engrave/cut) tool passes
via a new GravographISPostConfig, so ENGRAVE/ETCH-tagged geometry runs
as a separate scribe pass with its own feed/depth and an operator
pause before the cut pass (spring-floated spindle needs a tool swap).

Co-Authored-By: Claude Opus 4.6 <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

CLAUDE.md

@@ -120,3 +120,4 @@ Always keep `README.md` and `CLAUDE.md` up to date when making changes that affe
 - **Cut-off materialization lifecycle**: `CutOff` objects live on `Plate.CutOffs`. Each generates a `Drawing` (with `IsCutOff = true`) whose `Program` contains trimmed line segments. `Plate.RegenerateCutOffs(settings)` removes old cut-off Parts, recomputes programs, and re-adds them to `Plate.Parts`. Regeneration triggers: cut-off add/remove/move, part drag complete, fill complete, plate transform. Cut-off Parts are excluded from quantity tracking, utilization, overlap detection, and nest file serialization (programs are regenerated from definitions on load).
 - **User-defined G-code variables**: Programs can contain named variable definitions (`name = expression [inline] [global]`) referenced in coordinates with `$name`. Variables resolve to doubles at parse time for geometry/nesting. `VariableRefs` on `Motion`/`Feedrate` track the symbolic link so post processors can emit machine variable references. Cincinnati post maps non-inline variables to numbered machine variables (`#200+`) with descriptive comments. Global variables share a number across programs; local variables get per-drawing numbers. `ProgramReader` uses a two-pass parse (collect definitions, then parse G-code with substitution). `NestWriter` serializes definitions and `$references` back to text for round-trip fidelity.
 - **CAD import pipeline**: All "DXF → Drawing" conversion goes through `OpenNest.IO.CadImporter`. The UI form uses `Import` on file load (storing the mutable result in a `FileListItem`) and `BuildDrawing` on save (passing the user's current visible entities and bends). Console, MCP, API, and Training projects use `ImportDrawing` for headless conversion. This guarantees all callers produce drawings with the same shape: pierce-point `Source.Offset`, stable `SourceEntities` with GUIDs, `SuppressedEntityIds`, detected bends, and metadata.
+- **GravographIS engrave/cut passes**: The `OpenNest.Posts.GravographIS` post splits geometry by `LayerType` into ordered tool passes — engrave (`Scribe`) then cut (`Cut`/`Leadin`/`Leadout`); `Display` is skipped. `ConvertGeometry` tags DXF layers `ENGRAVE`/`ETCH` (lines, arcs, circles) as `Scribe`; the layer round-trips through `.nest` via `NestWriter`/`ProgramReader`. `NestPolylineExtractor.ExtractLayered` carries `LayerType` per polyline (splitting a continuous chain at any layer change); `GravographISPostProcessor.BuildPasses` groups them and `GravographISWriter.Write(IReadOnlyList<GravographPass>, …)` emits each pass at its own feed/depth, parking to origin and emitting an operator pause (motor off → aux off → `LB` console message → motor on) before any pass whose config has `PauseBefore`. Per-pass parameters live in `GravographISPostConfig` (an `IConfigurablePostProcessor` config with `Engrave`/`Cut` `LayerCutConfig` blocks), edited in the shared `PostProcessorConfigForm` PropertyGrid and persisted to JSON. The cut block pauses by default so the operator can swap/adjust the tool (the spring-floated spindle means programmed `DZ` depth is not the real cut depth).

OpenNest.Core/Converters/ConvertGeometry.cs

@@ -87,14 +87,15 @@ namespace OpenNest.Converters
 
             lastpt = endpt;
 
+            var layer = ClassifyLayer(arc);
             var sweep = System.Math.Abs(arc.SweepAngle());
             if (sweep < Tolerance.Epsilon || sweep.IsEqualTo(Angle.TwoPI))
             {
-                pgm.LineTo(endpt);
+                pgm.Codes.Add(new LinearMove(endpt) { Layer = layer });
             }
             else
             {
-                pgm.ArcTo(endpt, arc.Center, arc.IsReversed ? RotationType.CW : RotationType.CCW);
+                pgm.Codes.Add(new ArcMove(endpt, arc.Center, arc.IsReversed ? RotationType.CW : RotationType.CCW) { Layer = layer });
             }
 
             return lastpt;
@@ -107,7 +108,7 @@ namespace OpenNest.Converters
             if (startpt.DistanceTo(lastpt) > Tolerance.ChainTolerance)
                 pgm.MoveTo(startpt);
 
-            pgm.ArcTo(startpt, circle.Center, circle.Rotation);
+            pgm.Codes.Add(new ArcMove(startpt, circle.Center, circle.Rotation) { Layer = ClassifyLayer(circle) });
 
             lastpt = startpt;
             return lastpt;
@@ -118,13 +119,22 @@ namespace OpenNest.Converters
             if (line.StartPoint.DistanceTo(lastpt) > Tolerance.ChainTolerance)
                 pgm.MoveTo(line.StartPoint);
 
-            var move = new LinearMove(line.EndPoint);
-            if (string.Equals(line.Layer?.Name, "ETCH", System.StringComparison.OrdinalIgnoreCase))
-                move.Layer = LayerType.Scribe;
-            pgm.Codes.Add(move);
+            pgm.Codes.Add(new LinearMove(line.EndPoint) { Layer = ClassifyLayer(line) });
 
             lastpt = line.EndPoint;
             return lastpt;
         }
+
+        // Engrave/etch geometry maps to Scribe so the post processor can treat it as a
+        // separate tool pass; everything else keeps the move's default Cut layer.
+        private static LayerType ClassifyLayer(Entity geo)
+        {
+            var name = geo.Layer?.Name;
+            if (string.Equals(name, "ENGRAVE", System.StringComparison.OrdinalIgnoreCase) ||
+                string.Equals(name, "ETCH", System.StringComparison.OrdinalIgnoreCase))
+                return LayerType.Scribe;
+
+            return LayerType.Cut;
+        }
     }
 }

OpenNest.Core/Geometry/ArcFit.cs

@@ -57,13 +57,14 @@ namespace OpenNest.Geometry
         }
 
         /// <summary>
-        /// Fits a circular arc constrained to be tangent to the given directions at both
-        /// the first and last points. The center lies at the intersection of the normals
-        /// at P1 and Pn, guaranteeing the arc departs P1 in the start direction and arrives
-        /// at Pn in the end direction. Uses the radius from P1 (exact start tangent);
-        /// deviation includes any endpoint gap at Pn.
+        /// Fits a circular arc that passes exactly through both the first and last points
+        /// while matching the given endpoint tangents as closely as possible. For any
+        /// circle through two points, the tangents at those points make equal mirrored
+        /// angles with the chord, so the achievable inscribed angle is the average of the
+        /// two requested ones — when the requested tangents are consistent with a single
+        /// circular arc, both are matched exactly.
         /// </summary>
-        internal static (Vector center, double radius, double deviation) FitWithDualTangent(
+        internal static (Vector center, double radius, double deviation) FitThroughEndpointsWithTangents(
             List<Vector> points, Vector startTangent, Vector endTangent)
         {
             if (points.Count < 3)
@@ -72,42 +73,39 @@ namespace OpenNest.Geometry
             var p1 = points[0];
             var pn = points[^1];
 
-            var stLen = System.Math.Sqrt(startTangent.X * startTangent.X + startTangent.Y * startTangent.Y);
-            var etLen = System.Math.Sqrt(endTangent.X * endTangent.X + endTangent.Y * endTangent.Y);
-            if (stLen < 1e-10 || etLen < 1e-10)
-                return (Vector.Invalid, 0, double.MaxValue);
-
-            // Normal to start tangent at P1 (perpendicular)
-            var n1x = -startTangent.Y / stLen;
-            var n1y = startTangent.X / stLen;
-
-            // Normal to end tangent at Pn
-            var n2x = -endTangent.Y / etLen;
-            var n2y = endTangent.X / etLen;
-
-            // Solve: P1 + t1*N1 = Pn + t2*N2
-            var det = n1x * (-n2y) - (-n2x) * n1y;
-            if (System.Math.Abs(det) < 1e-10)
-                return (Vector.Invalid, 0, double.MaxValue);
-
             var dx = pn.X - p1.X;
             var dy = pn.Y - p1.Y;
-            var t1 = (dx * (-n2y) - (-n2x) * dy) / det;
-
-            var cx = p1.X + t1 * n1x;
-            var cy = p1.Y + t1 * n1y;
-
-            // Use radius from P1 (guarantees exact start tangent and passes through P1)
-            var r1 = System.Math.Sqrt((cx - p1.X) * (cx - p1.X) + (cy - p1.Y) * (cy - p1.Y));
-            if (r1 < 1e-10)
+            var chordLen = System.Math.Sqrt(dx * dx + dy * dy);
+            if (chordLen < 1e-10)
                 return (Vector.Invalid, 0, double.MaxValue);
 
-            // Measure endpoint gap at Pn
-            var r2 = System.Math.Sqrt((cx - pn.X) * (cx - pn.X) + (cy - pn.Y) * (cy - pn.Y));
-            var endpointDev = System.Math.Abs(r2 - r1);
+            var ux = dx / chordLen;
+            var uy = dy / chordLen;
 
-            var interiorDev = MaxRadialDeviation(points, cx, cy, r1);
-            return (new Vector(cx, cy), r1, System.Math.Max(endpointDev, interiorDev));
+            // Inscribed angle between chord and tangent at each endpoint (mirrored at Pn)
+            var theta1 = SignedAngle(ux, uy, startTangent);
+            var theta2 = -SignedAngle(ux, uy, endTangent);
+            var theta = (theta1 + theta2) / 2;
+
+            // Nearly straight or degenerate (sweep would exceed ~356 degrees)
+            if (System.Math.Abs(theta) < 1e-3 || System.Math.Abs(theta) > System.Math.PI * 0.99)
+                return (Vector.Invalid, 0, double.MaxValue);
+
+            var halfChord = chordLen / 2;
+            var radius = halfChord / System.Math.Abs(System.Math.Sin(theta));
+            var d = -halfChord / System.Math.Tan(theta);
+
+            var cx = (p1.X + pn.X) / 2 + d * -uy;
+            var cy = (p1.Y + pn.Y) / 2 + d * ux;
+
+            return (new Vector(cx, cy), radius, MaxRadialDeviation(points, cx, cy, radius));
+        }
+
+        private static double SignedAngle(double ux, double uy, Vector to)
+        {
+            var len = System.Math.Sqrt(to.X * to.X + to.Y * to.Y);
+            if (len < 1e-10) return 0;
+            return System.Math.Atan2(ux * to.Y - uy * to.X, ux * to.X + uy * to.Y);
         }
 
         /// <summary>

OpenNest.Core/Geometry/GeometrySimplifier.cs

@@ -374,11 +374,8 @@ public class GeometrySimplifier
         var points = CollectPoints(entities, start, k);
         if (points.Count < 3) return null;
 
-        var startTangent = chainedTangent.IsValid()
-            ? chainedTangent
-            : new Vector(points[1].X - points[0].X, points[1].Y - points[0].Y);
-
-        var endTangent = GetExitDirection(entities[k]);
+        var startTangent = EstimateStartTangent(entities, start, points, chainedTangent);
+        var endTangent = EstimateEndTangent(entities, k, points);
         var (center, radius, dev) = TryFit(points, startTangent, endTangent);
         if (!center.IsValid()) return null;
 
@@ -386,8 +383,10 @@ public class GeometrySimplifier
         while (k + 1 <= runEnd)
         {
             var extPoints = CollectPoints(entities, start, k + 1);
-            var extEndTangent = GetExitDirection(entities[k + 1]);
-            var (nc, nr, nd) = extPoints.Count >= 3 ? TryFit(extPoints, startTangent, extEndTangent) : (Vector.Invalid, 0, 0d);
+            if (extPoints.Count < 3) break;
+
+            var extEndTangent = EstimateEndTangent(entities, k + 1, extPoints);
+            var (nc, nr, nd) = TryFit(extPoints, startTangent, extEndTangent);
             if (!nc.IsValid()) break;
 
             k++;
@@ -407,37 +406,172 @@ public class GeometrySimplifier
         return new ArcFitResult(center, radius, dev, points, k);
     }
 
-    private (Vector center, double radius, double deviation) TryFit(List<Vector> points, Vector startTangent, Vector endTangent)
+    private (Vector center, double radius, double deviation) TryFit(
+        List<Vector> points, TangentEstimate start, TangentEstimate end)
     {
-        // Try dual-tangent fit first (matches direction at both endpoints)
-        if (endTangent.IsValid())
+        foreach (var (center, radius, dev) in FitAttempts(points, start, end))
         {
-            var (dc, dr, dd) = ArcFit.FitWithDualTangent(points, startTangent, endTangent);
-            if (dc.IsValid() && dd <= Tolerance)
-            {
-                var isRev = SumSignedAngles(dc, points) < 0;
-                var aDev = MaxArcToSegmentDeviation(points, dc, dr, isRev);
-                if (aDev <= Tolerance)
-                    return (dc, dr, System.Math.Max(dd, aDev));
-            }
-        }
-
-        // Fall back to start-tangent-only, then mirror axis
-        var (center, radius, dev) = ArcFit.FitWithStartTangent(points, startTangent);
             if (!center.IsValid() || dev > Tolerance)
-            (center, radius, dev) = FitMirrorAxis(points);
-        if (!center.IsValid() || dev > Tolerance)
-            return (Vector.Invalid, 0, 0);
+                continue;
 
             // Check that the arc doesn't bulge away from the original line segments
             var isReversed = SumSignedAngles(center, points) < 0;
             var arcDev = MaxArcToSegmentDeviation(points, center, radius, isReversed);
             if (arcDev > Tolerance)
-            return (Vector.Invalid, 0, 0);
+                continue;
 
             return (center, radius, System.Math.Max(dev, arcDev));
         }
 
+        return (Vector.Invalid, 0, 0);
+    }
+
+    /// <summary>
+    /// Yields fit attempts in preference order. A trusted tangent (chained from the
+    /// previous arc, an adjacent original arc, or a long straight edge) is enforced
+    /// exactly on its side; otherwise the tangency error is balanced between both
+    /// endpoints. The unconstrained mirror-axis fit is the last resort. Every attempt
+    /// passes exactly through both endpoints, so no gaps are introduced.
+    /// </summary>
+    private IEnumerable<(Vector center, double radius, double deviation)> FitAttempts(
+        List<Vector> points, TangentEstimate start, TangentEstimate end)
+    {
+        if (start.Trusted && !end.Trusted)
+        {
+            yield return ArcFit.FitWithStartTangent(points, start.Direction);
+            yield return ArcFit.FitThroughEndpointsWithTangents(points, start.Direction, end.Direction);
+            yield return FitWithEndTangent(points, end.Direction);
+        }
+        else if (end.Trusted && !start.Trusted)
+        {
+            yield return FitWithEndTangent(points, end.Direction);
+            yield return ArcFit.FitThroughEndpointsWithTangents(points, start.Direction, end.Direction);
+            yield return ArcFit.FitWithStartTangent(points, start.Direction);
+        }
+        else
+        {
+            yield return ArcFit.FitThroughEndpointsWithTangents(points, start.Direction, end.Direction);
+            yield return ArcFit.FitWithStartTangent(points, start.Direction);
+            yield return FitWithEndTangent(points, end.Direction);
+        }
+
+        yield return FitMirrorAxis(points);
+    }
+
+    /// <summary>
+    /// Fits an arc through both endpoints with an exact tangent at the last point,
+    /// by running the start-tangent fit on the reversed point sequence.
+    /// </summary>
+    private static (Vector center, double radius, double deviation) FitWithEndTangent(
+        List<Vector> points, Vector endTangent)
+    {
+        var reversed = new List<Vector>(points);
+        reversed.Reverse();
+        return ArcFit.FitWithStartTangent(reversed, new Vector(-endTangent.X, -endTangent.Y));
+    }
+
+    /// <summary>
+    /// An estimated tangent direction at a fit endpoint. Trusted estimates come from
+    /// exact geometry (a chained arc, an adjacent original arc, or a long straight
+    /// edge) and are enforced exactly; untrusted ones are derived from the polyline
+    /// vertices and only guide the fit.
+    /// </summary>
+    private readonly record struct TangentEstimate(Vector Direction, bool Trusted);
+
+    /// <summary>Segment-length ratio above which a neighboring line counts as a true
+    /// straight edge (rather than another chord of the tessellated curve).</summary>
+    private const double NeighborEdgeFactor = 3.0;
+
+    private static TangentEstimate EstimateStartTangent(
+        List<Entity> entities, int start, List<Vector> points, Vector chainedTangent)
+    {
+        if (chainedTangent.IsValid())
+            return new TangentEstimate(chainedTangent, true);
+
+        if (entities[start] is Arc startArc)
+            return new TangentEstimate(GetEntryDirection(startArc), true);
+
+        var firstChordLen = points[0].DistanceTo(points[1]);
+        if (start > 0)
+        {
+            var prev = entities[start - 1];
+            var prevEnd = prev switch { Line l => l.EndPoint, Arc a => a.EndPoint(), _ => Vector.Invalid };
+            if (prevEnd.IsValid() && prevEnd.DistanceTo(points[0]) < 1e-6)
+            {
+                if (prev is Arc)
+                    return new TangentEstimate(GetExitDirection(prev), true);
+                if (prev is Line prevLine && prevLine.StartPoint.DistanceTo(prevLine.EndPoint) >= NeighborEdgeFactor * firstChordLen)
+                    return new TangentEstimate(GetExitDirection(prevLine), true);
+            }
+        }
+
+        var chord = new Vector(points[1].X - points[0].X, points[1].Y - points[0].Y);
+        if (points.Count >= 3)
+            return new TangentEstimate(EstimateVertexTangent(points[0], points[1], points[2], chord), false);
+        return new TangentEstimate(chord, false);
+    }
+
+    private static TangentEstimate EstimateEndTangent(List<Entity> entities, int k, List<Vector> points)
+    {
+        if (entities[k] is Arc endArc)
+            return new TangentEstimate(GetExitDirection(endArc), true);
+
+        var lastChordLen = points[^1].DistanceTo(points[^2]);
+        if (k + 1 < entities.Count)
+        {
+            var next = entities[k + 1];
+            var nextStart = next switch { Line l => l.StartPoint, Arc a => a.StartPoint(), _ => Vector.Invalid };
+            if (nextStart.IsValid() && nextStart.DistanceTo(points[^1]) < 1e-6)
+            {
+                if (next is Arc nextArc)
+                    return new TangentEstimate(GetEntryDirection(nextArc), true);
+                if (next is Line nextLine && nextLine.StartPoint.DistanceTo(nextLine.EndPoint) >= NeighborEdgeFactor * lastChordLen)
+                    return new TangentEstimate(GetExitDirection(nextLine), true);
+            }
+        }
+
+        var chord = new Vector(points[^1].X - points[^2].X, points[^1].Y - points[^2].Y);
+        if (points.Count >= 3)
+            return new TangentEstimate(EstimateVertexTangent(points[^1], points[^2], points[^3], chord), false);
+        return new TangentEstimate(chord, false);
+    }
+
+    /// <summary>
+    /// Estimates the curve tangent at a polyline vertex from the circle through it and
+    /// its two nearest neighbors. A raw chord direction is off from the true tangent by
+    /// half the chord's subtended angle; the circumcircle estimate removes that bias.
+    /// Falls back to the travel direction when the three points are collinear.
+    /// </summary>
+    private static Vector EstimateVertexTangent(Vector at, Vector b, Vector c, Vector travel)
+    {
+        var d = 2 * (at.X * (b.Y - c.Y) + b.X * (c.Y - at.Y) + c.X * (at.Y - b.Y));
+        if (System.Math.Abs(d) < 1e-14)
+            return travel;
+
+        var sqA = at.X * at.X + at.Y * at.Y;
+        var sqB = b.X * b.X + b.Y * b.Y;
+        var sqC = c.X * c.X + c.Y * c.Y;
+        var cx = (sqA * (b.Y - c.Y) + sqB * (c.Y - at.Y) + sqC * (at.Y - b.Y)) / d;
+        var cy = (sqA * (c.X - b.X) + sqB * (at.X - c.X) + sqC * (b.X - at.X)) / d;
+
+        var tangent = new Vector(-(at.Y - cy), at.X - cx);
+        if (tangent.X * travel.X + tangent.Y * travel.Y < 0)
+            tangent = new Vector(-tangent.X, -tangent.Y);
+        return tangent;
+    }
+
+    /// <summary>
+    /// Returns the entry direction (tangent at start point) of an entity.
+    /// </summary>
+    private static Vector GetEntryDirection(Entity entity) => entity switch
+    {
+        Line line => new Vector(line.EndPoint.X - line.StartPoint.X, line.EndPoint.Y - line.StartPoint.Y),
+        Arc arc => arc.IsReversed
+            ? new Vector(System.Math.Sin(arc.StartAngle), -System.Math.Cos(arc.StartAngle))
+            : new Vector(-System.Math.Sin(arc.StartAngle), System.Math.Cos(arc.StartAngle)),
+        _ => Vector.Invalid,
+    };
+
     /// <summary>
     /// Computes the tangent direction at the last point of a fitted arc,
     /// used to chain tangent continuity to the next arc.

OpenNest.IO/CadImporter.cs

@@ -27,6 +27,7 @@ namespace OpenNest.IO
             var dxf = Dxf.Import(path);
 
             RemoveDuplicateArcs(dxf.Entities);
+            RemoveZeroSweepArcs(dxf.Entities);
 
             var bends = new List<Bend>();
             if (options.DetectBends && dxf.Document != null)
@@ -141,6 +142,12 @@ namespace OpenNest.IO
             return drawing;
         }
 
+        internal static void RemoveZeroSweepArcs(List<Entity> entities)
+        {
+            entities.RemoveAll(e =>
+                e is Arc arc && arc.StartAngle.IsEqualTo(arc.EndAngle, Tolerance.ChainTolerance));
+        }
+
         internal static void RemoveDuplicateArcs(List<Entity> entities)
         {
             var circles = entities.OfType<Circle>().ToList();

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.IO/Dxf.cs

@@ -242,6 +242,7 @@ namespace OpenNest.IO
             public ExportContext()
             {
                 Document = new CadDocument();
+                Document.Header.Version = ACadVersion.AC1018;
 
                 CutLayer = new Layer("Cut") { Color = new Color(1) };
                 RapidLayer = new Layer("Rapid") { Color = new Color(5) };

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/GravographISPostConfig.cs

@@ -0,0 +1,81 @@
+using System.ComponentModel;
+using OpenNest.CNC;
+
+namespace OpenNest.Posts.GravographIS
+{
+    /// <summary>
+    /// Cut parameters for one kind of pass (engrave or cut). Edited in the post
+    /// configuration PropertyGrid and persisted to JSON.
+    /// </summary>
+    [TypeConverter(typeof(ExpandableObjectConverter))]
+    public sealed class LayerCutConfig
+    {
+        [DisplayName("Feed (mm/sec)")]
+        [Description("XY and Z feed for this pass. Patches the VS and VZ wire commands.")]
+        public int FeedMmPerSec { get; set; } = 10;
+
+        [DisplayName("Depth (inches)")]
+        [Description("Programmed Z plunge (DZ). Note: the spring-floated spindle means this does not set actual cut depth — tool protrusion does.")]
+        public double Depth { get; set; } = 0.25;
+
+        [DisplayName("Pause Before")]
+        [Description("Stop the spindle and prompt the operator before this pass begins, so the tool can be swapped/adjusted.")]
+        public bool PauseBefore { get; set; }
+
+        [DisplayName("Pause Message")]
+        [Description("Message shown on the controller during the pause.")]
+        public string PauseMessage { get; set; } = "";
+
+        public override string ToString() => $"{FeedMmPerSec} mm/s, {Depth:0.###}\"" + (PauseBefore ? ", pause" : "");
+    }
+
+    /// <summary>
+    /// Configuration for the Gravograph IS post processor: one <see cref="LayerCutConfig"/>
+    /// per cut kind. The engrave block applies to <see cref="LayerType.Scribe"/> paths,
+    /// the cut block to <see cref="LayerType.Cut"/>/<see cref="LayerType.Leadin"/>/<see cref="LayerType.Leadout"/>.
+    /// The cut block carries the tool-change pause by default.
+    /// </summary>
+    public sealed class GravographISPostConfig
+    {
+        [Category("Engrave (Scribe)")]
+        [DisplayName("Engrave")]
+        [Description("Parameters for engrave/scribe geometry (text).")]
+        public LayerCutConfig Engrave { get; set; } = new LayerCutConfig
+        {
+            FeedMmPerSec = 10,
+            Depth = 0.25,
+            PauseBefore = false,
+            PauseMessage = "",
+        };
+
+        [Category("Cut")]
+        [DisplayName("Cut")]
+        [Description("Parameters for cut geometry (outlines). Pauses for a tool change by default.")]
+        public LayerCutConfig Cut { get; set; } = new LayerCutConfig
+        {
+            FeedMmPerSec = 3,
+            Depth = 0.25,
+            PauseBefore = true,
+            PauseMessage = "Change tool",
+        };
+
+        /// <summary>
+        /// Returns the cut config a polyline of the given layer should use, or null
+        /// if the layer is non-cutting (<see cref="LayerType.Display"/>) and should be skipped.
+        /// </summary>
+        public LayerCutConfig ConfigFor(LayerType layer)
+        {
+            switch (layer)
+            {
+                case LayerType.Scribe:
+                    return Engrave;
+                case LayerType.Cut:
+                case LayerType.Leadin:
+                case LayerType.Leadout:
+                    return Cut;
+                default:
+                    return null;
+            }
+        }
+    }
+}

OpenNest.Posts.GravographIS/GravographISPostProcessor.cs

@@ -0,0 +1,160 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.IO.Ports;
+using System.Text.Json;
+using System.Text.Json.Serialization;
+using System.Threading;
+using OpenNest.Geometry;
+
+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)"/>.
+    ///
+    /// Geometry is split by <see cref="OpenNest.CNC.LayerType"/> into an engrave pass
+    /// (Scribe) and a cut pass (Cut), each with its own feed/depth from <see cref="Config"/>.
+    /// The cut pass pauses by default so the operator can swap/adjust the tool.
+    /// </summary>
+    public sealed class GravographISPostProcessor : IConfigurablePostProcessor
+    {
+        private static readonly JsonSerializerOptions JsonOptions = new()
+        {
+            WriteIndented = true,
+            Converters = { new JsonStringEnumConverter() }
+        };
+
+        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 GravographISPostConfig Config { get; }
+
+        object IConfigurablePostProcessor.Config => Config;
+
+        public GravographISPostProcessor()
+        {
+            var configPath = GetConfigPath();
+            if (File.Exists(configPath))
+            {
+                var json = File.ReadAllText(configPath);
+                Config = JsonSerializer.Deserialize<GravographISPostConfig>(json, JsonOptions)
+                    ?? new GravographISPostConfig();
+            }
+            else
+            {
+                Config = new GravographISPostConfig();
+                SaveConfig();
+            }
+        }
+
+        public GravographISPostProcessor(GravographISPostConfig config)
+        {
+            Config = config ?? throw new ArgumentNullException(nameof(config));
+        }
+
+        public void SaveConfig()
+        {
+            var configPath = GetConfigPath();
+            var json = JsonSerializer.Serialize(Config, JsonOptions);
+            File.WriteAllText(configPath, json);
+        }
+
+        private static string GetConfigPath()
+        {
+            var assemblyPath = typeof(GravographISPostProcessor).Assembly.Location;
+            var dir = Path.GetDirectoryName(assemblyPath);
+            var name = Path.GetFileNameWithoutExtension(assemblyPath);
+            return Path.Combine(dir, name + ".json");
+        }
+
+        public void Post(Nest nest, Stream outputStream)
+        {
+            if (nest == null) throw new ArgumentNullException(nameof(nest));
+            if (outputStream == null) throw new ArgumentNullException(nameof(outputStream));
+
+            var passes = BuildPasses(Extractor.ExtractLayered(nest));
+            new GravographISWriter(WriterOptions).Write(passes, outputStream);
+        }
+
+        public void Post(Nest nest, string outputFile)
+        {
+            using var fs = new FileStream(outputFile, FileMode.Create, FileAccess.Write);
+            Post(nest, fs);
+        }
+
+        /// <summary>
+        /// Groups layer-tagged polylines into ordered tool passes: engrave (Scribe)
+        /// first, then cut. Each group is stitch/reverse-optimized independently.
+        /// Geometry whose layer maps to no config (Display) is skipped. When only one
+        /// group is present, a single pass is returned (and so the writer emits no pause).
+        /// </summary>
+        public IReadOnlyList<GravographPass> BuildPasses(IEnumerable<LayeredPolyline> polylines)
+        {
+            if (polylines == null) throw new ArgumentNullException(nameof(polylines));
+
+            var engrave = new List<IReadOnlyList<Vector>>();
+            var cut = new List<IReadOnlyList<Vector>>();
+
+            foreach (var poly in polylines)
+            {
+                if (poly == null) continue;
+                var block = Config.ConfigFor(poly.Layer);
+                if (block == null)
+                    continue; // non-cutting (Display) geometry
+                if (ReferenceEquals(block, Config.Engrave))
+                    engrave.Add(poly.Points);
+                else
+                    cut.Add(poly.Points);
+            }
+
+            var passes = new List<GravographPass>();
+            if (engrave.Count > 0)
+                passes.Add(MakePass(Config.Engrave, engrave));
+            if (cut.Count > 0)
+                passes.Add(MakePass(Config.Cut, cut));
+
+            return passes;
+        }
+
+        private GravographPass MakePass(LayerCutConfig block, List<IReadOnlyList<Vector>> polylines)
+        {
+            return new GravographPass
+            {
+                Polylines = PolylinePrePass.Prepare(polylines, StitchTolerance, AllowReverse),
+                FeedMmPerSec = block.FeedMmPerSec,
+                DepthInches = block.Depth,
+                PauseBefore = block.PauseBefore,
+                PauseMessage = block.PauseMessage ?? "",
+            };
+        }
+
+        /// <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 +1,464 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Text;
+using OpenNest.Geometry;
+
+namespace OpenNest.Posts.GravographIS
+{
+    /// <summary>
+    /// One tool pass: a run of polylines cut at a single feed/depth, optionally
+    /// preceded by an operator pause (to swap or adjust the tool). The Gravograph
+    /// post builds one pass for engrave and one for cut.
+    /// </summary>
+    public sealed class GravographPass
+    {
+        public IEnumerable<IReadOnlyList<Vector>> Polylines { get; set; }
+
+        public int FeedMmPerSec { get; set; }
+
+        public double DepthInches { get; set; }
+
+        /// <summary>When true, park to origin and prompt the operator before this pass.</summary>
+        public bool PauseBefore { get; set; }
+
+        public string PauseMessage { get; set; } = "";
+    }
+
+    /// <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));
+
+            // A single pass at the configured feed/depth — byte-identical to the
+            // original single-group output (no transitions, no pause).
+            Write(new[]
+            {
+                new GravographPass
+                {
+                    Polylines = polylines,
+                    FeedMmPerSec = Options.FeedMmPerSec,
+                    DepthInches = Options.DepthInches,
+                    PauseBefore = false,
+                    PauseMessage = "",
+                },
+            }, output);
+        }
+
+        /// <summary>
+        /// Writes the full byte stream for an ordered list of tool passes. The preamble
+        /// carries the first pass's feed/depth; each later pass emits an inline feed
+        /// (and depth, if changed) and, when <see cref="GravographPass.PauseBefore"/> is
+        /// set, parks to the operator origin and emits an operator pause before cutting.
+        /// </summary>
+        public void Write(IReadOnlyList<GravographPass> passes, Stream output)
+        {
+            if (passes == null) throw new ArgumentNullException(nameof(passes));
+            if (output == null) throw new ArgumentNullException(nameof(output));
+
+            var firstFeed = passes.Count > 0 ? passes[0].FeedMmPerSec : Options.FeedMmPerSec;
+            var firstDepth = passes.Count > 0 ? passes[0].DepthInches : Options.DepthInches;
+
+            var preamble = (byte[])PreambleTemplate.Clone();
+            PatchOperand(preamble, (byte)'V', (byte)'S', (short)firstFeed);
+            PatchOperand(preamble, (byte)'V', (byte)'Z', (short)firstFeed);
+            PatchOperand(preamble, (byte)'D', (byte)'Z', DepthInStepsAsInt16(firstDepth));
+            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;
+            var currentFeed = firstFeed;
+            var currentDepth = firstDepth;
+
+            for (var p = 0; p < passes.Count; p++)
+            {
+                var pass = passes[p];
+
+                if (p > 0)
+                {
+                    if (pass.PauseBefore)
+                    {
+                        // Park: lift Z, then rapid (pen-up) back to the operator origin so
+                        // the head is clear of the work while the tool is swapped.
+                        WriteLiftOnly(output);
+                        WriteTravel(output, (byte)'P', (byte)'U',
+                            checked(-headX), checked(-headY),
+                            ref headX, ref headY, envelopeXSteps, envelopeYSteps, polyIndex);
+                        WritePauseCore(output, pass.PauseMessage);
+                    }
+
+                    if (pass.FeedMmPerSec != currentFeed)
+                    {
+                        WriteCommand(output, (byte)'V', (byte)'S', (short)pass.FeedMmPerSec);
+                        WriteCommand(output, (byte)'V', (byte)'Z', (short)pass.FeedMmPerSec);
+                        currentFeed = pass.FeedMmPerSec;
+                    }
+
+                    if (pass.DepthInches != currentDepth)
+                    {
+                        WriteCommand(output, (byte)'D', (byte)'Z', DepthInStepsAsInt16(pass.DepthInches));
+                        currentDepth = pass.DepthInches;
+                    }
+                }
+
+                if (pass.Polylines == null) continue;
+
+                foreach (var poly in pass.Polylines)
+                {
+                    polyIndex++;
+                    if (poly == null || poly.Count < 2)
+                        continue;
+
+                    WritePolyline(output, poly, ref firstPolyline, ref headX, ref headY,
+                        envelopeXSteps, envelopeYSteps, polyIndex);
+                }
+            }
+
+            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 void WritePolyline(Stream output, IReadOnlyList<Vector> poly,
+            ref bool firstPolyline, ref int headX, ref int headY,
+            int envelopeXSteps, int envelopeYSteps, int polyIndex)
+        {
+            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;
+        }
+
+        // The operator pause, minus the leading lift/park which the caller emits.
+        // Stops the spindle (MC off), turns off aux, writes the console message, then
+        // restarts the spindle (MC on) so the job resumes when the operator presses start.
+        private static void WritePauseCore(Stream s, string message)
+        {
+            WriteCommandRaw(s, (byte)'M', (byte)'C', 0x00, 0x00); // motor off
+            WriteCommandRaw(s, (byte)'O', (byte)'U', 0xFF, 0xFB); // aux off
+            WriteCommandRaw(s, (byte)'O', (byte)'U', 0xFF, 0xFA); // aux off
+            WriteCommandRaw(s, (byte)'L', (byte)'B', 0x00, 0x00); // begin message
+            WriteMessagePackets(s, message);
+            WriteCommandRaw(s, (byte)'N', (byte)'R', 0x00, 0x01); // line terminator
+            WriteCommandRaw(s, (byte)'L', (byte)'B', 0x00, 0x01); // end message
+            WriteCommandRaw(s, (byte)'M', (byte)'C', 0x00, 0x01); // motor on
+        }
+
+        // Console label packets carry two ASCII chars each; an odd-length message is
+        // space-padded to a whole number of packets so widths stay 2 bytes.
+        private static void WriteMessagePackets(Stream s, string message)
+        {
+            if (string.IsNullOrEmpty(message)) return;
+
+            var chars = Encoding.ASCII.GetBytes(message);
+            for (var i = 0; i < chars.Length; i += 2)
+            {
+                var c0 = chars[i];
+                var c1 = (i + 1 < chars.Length) ? chars[i + 1] : (byte)0x20;
+                WriteCommandRaw(s, (byte)'L', (byte)'B', c0, c1);
+            }
+        }
+
+        private static void WriteCommand(Stream s, byte c0, byte c1, short value)
+        {
+            WriteCommandRaw(s, c0, c1, (byte)((value >> 8) & 0xFF), (byte)(value & 0xFF));
+        }
+
+        private static void WriteCommandRaw(Stream s, byte c0, byte c1, byte hi, byte lo)
+        {
+            s.WriteByte(0xFF);
+            s.WriteByte(0xFD);
+            s.WriteByte(c0);
+            s.WriteByte(c1);
+            s.WriteByte(hi);
+            s.WriteByte(lo);
+        }
+
+        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 static short DepthInStepsAsInt16(double depthInches)
+        {
+            var steps = (long)System.Math.Round(depthInches * StepsPerInch, MidpointRounding.AwayFromZero);
+            if (steps < short.MinValue || steps > short.MaxValue)
+                throw new ArgumentOutOfRangeException(nameof(depthInches), $"Depth {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 +1,232 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using OpenNest.CNC;
+using OpenNest.Geometry;
+
+namespace OpenNest.Posts.GravographIS
+{
+    /// <summary>
+    /// A polyline together with the <see cref="LayerType"/> of the moves that
+    /// produced it. The Gravograph post groups by layer to emit separate engrave
+    /// and cut passes (with a tool-change pause between them).
+    /// </summary>
+    public sealed class LayeredPolyline
+    {
+        public LayeredPolyline(List<Vector> points, LayerType layer)
+        {
+            Points = points;
+            Layer = layer;
+        }
+
+        public List<Vector> Points { get; }
+
+        public LayerType Layer { get; }
+    }
+
+    /// <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 at <see cref="LayerType"/> changes, 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). Layer information is dropped;
+        /// use <see cref="ExtractLayered(Nest)"/> to keep it.
+        /// </summary>
+        public List<List<Vector>> Extract(Nest nest)
+        {
+            return ExtractLayered(nest).Select(p => p.Points).ToList();
+        }
+
+        /// <summary>
+        /// Extracts polylines for a single part without layer information.
+        /// </summary>
+        public List<List<Vector>> ExtractPart(Part part)
+        {
+            return ExtractPartLayered(part).Select(p => p.Points).ToList();
+        }
+
+        /// <summary>
+        /// Extracts layer-tagged polylines from every non-cutoff part in every plate,
+        /// in plate coordinates (inches). Each polyline is layer-uniform.
+        /// </summary>
+        public List<LayeredPolyline> ExtractLayered(Nest nest)
+        {
+            if (nest == null) throw new ArgumentNullException(nameof(nest));
+
+            var result = new List<LayeredPolyline>();
+
+            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 layer-tagged 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<LayeredPolyline> ExtractPartLayered(Part part)
+        {
+            var list = new List<LayeredPolyline>();
+            ExtractPart(part, list);
+            return list;
+        }
+
+        private void ExtractPart(Part part, List<LayeredPolyline> 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;
+            var currentLayer = LayerType.Cut;
+
+            foreach (var code in program.Codes)
+            {
+                if (code is Motion m && m.Suppressed)
+                    continue;
+
+                switch (code)
+                {
+                    case RapidMove rapid:
+                    {
+                        FlushCurrent(sink, ref current, currentLayer);
+                        pos = rapid.EndPoint;
+                        break;
+                    }
+
+                    case LinearMove linear:
+                    {
+                        StartOrSplit(sink, ref current, ref currentLayer, linear.Layer, pos + offset);
+                        var end = linear.EndPoint;
+                        current.Add(end + offset);
+                        pos = end;
+                        break;
+                    }
+
+                    case ArcMove arc:
+                    {
+                        StartOrSplit(sink, ref current, ref currentLayer, arc.Layer, pos + offset);
+                        TessellateArc(pos, arc, offset, ArcChordToleranceInches, current);
+                        pos = arc.EndPoint;
+                        break;
+                    }
+                }
+            }
+
+            FlushCurrent(sink, ref current, currentLayer);
+        }
+
+        // Ensures `current` is an open polyline whose layer matches `moveLayer`,
+        // seeded at `seed` (the current pen position). When the layer changes
+        // mid-chain the previous polyline is flushed and a new one begins at the
+        // shared seam vertex so engrave and cut passes stay geometrically continuous.
+        private static void StartOrSplit(List<LayeredPolyline> sink, ref List<Vector> current,
+            ref LayerType currentLayer, LayerType moveLayer, Vector seed)
+        {
+            if (current == null)
+            {
+                current = new List<Vector> { seed };
+                currentLayer = moveLayer;
+            }
+            else if (moveLayer != currentLayer)
+            {
+                FlushCurrent(sink, ref current, currentLayer);
+                current = new List<Vector> { seed };
+                currentLayer = moveLayer;
+            }
+        }
+
+        private static void FlushCurrent(List<LayeredPolyline> sink, ref List<Vector> current, LayerType layer)
+        {
+            if (current != null && current.Count >= 2)
+                sink.Add(new LayeredPolyline(current, layer));
+            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/Converters/ConvertGeometryLayerTests.cs

@@ -0,0 +1,70 @@
+using System.Linq;
+using OpenNest.CNC;
+using OpenNest.Converters;
+using OpenNest.Geometry;
+
+namespace OpenNest.Tests.Converters;
+
+public class ConvertGeometryLayerTests
+{
+    private static Program ProgramFor(Entity entity)
+    {
+        var shape = new Shape();
+        shape.Entities.Add(entity);
+        return ConvertGeometry.ToProgram(shape);
+    }
+
+    [Fact]
+    public void AddLine_EngraveLayer_TagsScribe()
+    {
+        var line = new Line(0, 0, 1, 0) { Layer = new Layer("ENGRAVE") };
+
+        var pgm = ProgramFor(line);
+
+        Assert.All(pgm.Codes.OfType<LinearMove>(), m => Assert.Equal(LayerType.Scribe, m.Layer));
+    }
+
+    [Fact]
+    public void AddLine_EtchLayer_TagsScribe()
+    {
+        var line = new Line(0, 0, 1, 0) { Layer = new Layer("etch") };
+
+        var pgm = ProgramFor(line);
+
+        Assert.All(pgm.Codes.OfType<LinearMove>(), m => Assert.Equal(LayerType.Scribe, m.Layer));
+    }
+
+    [Fact]
+    public void AddArc_EngraveLayer_TagsScribe()
+    {
+        var arc = new Arc(new Vector(0, 0), 1, 0, System.Math.PI / 2) { Layer = new Layer("ENGRAVE") };
+
+        var pgm = ProgramFor(arc);
+
+        var arcs = pgm.Codes.OfType<ArcMove>().ToList();
+        Assert.NotEmpty(arcs);
+        Assert.All(arcs, m => Assert.Equal(LayerType.Scribe, m.Layer));
+    }
+
+    [Fact]
+    public void AddCircle_EngraveLayer_TagsScribe()
+    {
+        var circle = new Circle(0, 0, 1) { Layer = new Layer("ENGRAVE") };
+
+        var pgm = ProgramFor(circle);
+
+        var arcs = pgm.Codes.OfType<ArcMove>().ToList();
+        Assert.NotEmpty(arcs);
+        Assert.All(arcs, m => Assert.Equal(LayerType.Scribe, m.Layer));
+    }
+
+    [Fact]
+    public void AddLine_DefaultLayer_StaysCut()
+    {
+        var line = new Line(0, 0, 1, 0) { Layer = new Layer("0") };
+
+        var pgm = ProgramFor(line);
+
+        Assert.All(pgm.Codes.OfType<LinearMove>(), m => Assert.Equal(LayerType.Cut, m.Layer));
+    }
+}

OpenNest.Tests/Geometry/GeometrySimplifierTests.cs

@@ -131,6 +131,111 @@ public class GeometrySimplifierTests
         Assert.IsType<Arc>(result.Entities[6]);
     }
 
+    [Fact]
+    public void Analyze_FilletBetweenTangentLines_ArcIsTangentToLines()
+    {
+        // A 90-degree fillet (r=0.3, center origin, 270deg..360deg CCW) between two
+        // long tangent lines, approximated by 8 chords whose interior vertices bulge
+        // radially outward within tolerance (simulates real DXF tessellation noise).
+        var r = 0.3;
+        var deltas = new[] { 0.0, 0.002, 0.003, 0.0035, 0.0035, 0.0035, 0.003, 0.002, 0.0 };
+        var pts = new List<Vector>();
+        for (var i = 0; i <= 8; i++)
+        {
+            var ang = OpenNest.Math.Angle.ToRadians(270 + 11.25 * i);
+            var radius = r + deltas[i];
+            pts.Add(new Vector(radius * System.Math.Cos(ang), radius * System.Math.Sin(ang)));
+        }
+
+        var shape = new Shape();
+        shape.Entities.Add(new Line(new Vector(-2, -r), pts[0]));
+        for (var i = 0; i < pts.Count - 1; i++)
+            shape.Entities.Add(new Line(pts[i], pts[i + 1]));
+        shape.Entities.Add(new Line(pts[^1], new Vector(r, 2)));
+
+        var simplifier = new GeometrySimplifier { Tolerance = 0.004 };
+        var candidates = simplifier.Analyze(shape);
+
+        Assert.Single(candidates);
+        var arc = candidates[0].FittedArc;
+
+        // Arc must pass exactly through the run's boundary vertices (no gaps)
+        Assert.True(arc.StartPoint().DistanceTo(pts[0]) < 1e-6);
+        Assert.True(arc.EndPoint().DistanceTo(pts[^1]) < 1e-6);
+
+        // Arc must be tangent to the adjacent straight edges at its endpoints
+        var startDelta = AngleBetweenDeg(ArcTangentAt(arc, arc.StartPoint()), new Vector(1, 0));
+        var endDelta = AngleBetweenDeg(ArcTangentAt(arc, arc.EndPoint()), new Vector(0, 1));
+        Assert.True(startDelta < 0.3, $"Arc start not tangent to incoming line: off by {startDelta:F3} deg");
+        Assert.True(endDelta < 0.3, $"Arc end not tangent to outgoing line: off by {endDelta:F3} deg");
+    }
+
+    [Fact]
+    public void Analyze_CompoundCurve_AdjacentArcsAreTangentAtJunction()
+    {
+        // Two tangent-continuous arcs of different radii (r=0.2 sweeping 60deg, then
+        // r=0.6 sweeping 40deg), tessellated into chords with slight radial noise.
+        // The fitted arcs must stay tangent-continuous at their junction.
+        var c1 = new Vector(0, 0);
+        var r1 = 0.2;
+        var deltas1 = new[] { 0.0, 0.001, 0.0005, -0.0005, -0.001, -0.0005, 0.0 };
+        var pts = new List<Vector>();
+        for (var i = 0; i <= 6; i++)
+        {
+            var ang = OpenNest.Math.Angle.ToRadians(10 * i);
+            var radius = r1 + deltas1[i];
+            pts.Add(new Vector(c1.X + radius * System.Math.Cos(ang), c1.Y + radius * System.Math.Sin(ang)));
+        }
+
+        // Second arc center along the junction radius so tangents match at the junction
+        var junctionAngle = OpenNest.Math.Angle.ToRadians(60);
+        var u = new Vector(System.Math.Cos(junctionAngle), System.Math.Sin(junctionAngle));
+        var r2 = 0.6;
+        var c2 = new Vector(c1.X + u.X * (r1 - r2), c1.Y + u.Y * (r1 - r2));
+        var deltas2 = new[] { 0.0, 0.001, -0.001, 0.0005, -0.0005, 0.0 };
+        for (var i = 1; i <= 5; i++)
+        {
+            var ang = OpenNest.Math.Angle.ToRadians(60 + 8 * i);
+            var radius = r2 + deltas2[i];
+            pts.Add(new Vector(c2.X + radius * System.Math.Cos(ang), c2.Y + radius * System.Math.Sin(ang)));
+        }
+
+        var shape = new Shape();
+        for (var i = 0; i < pts.Count - 1; i++)
+            shape.Entities.Add(new Line(pts[i], pts[i + 1]));
+
+        var simplifier = new GeometrySimplifier { Tolerance = 0.004 };
+        var candidates = simplifier.Analyze(shape);
+
+        Assert.Equal(2, candidates.Count);
+        var arcA = candidates[0].FittedArc;
+        var arcB = candidates[1].FittedArc;
+
+        // Arcs must share the junction vertex exactly
+        Assert.True(arcA.EndPoint().DistanceTo(arcB.StartPoint()) < 1e-6);
+
+        // Tangent continuity across the junction
+        var junctionDelta = AngleBetweenDeg(ArcTangentAt(arcA, arcA.EndPoint()), ArcTangentAt(arcB, arcB.StartPoint()));
+        Assert.True(junctionDelta < 0.3, $"Tangent break of {junctionDelta:F3} deg at arc-arc junction");
+    }
+
+    private static Vector ArcTangentAt(Arc arc, Vector pt)
+    {
+        var ang = System.Math.Atan2(pt.Y - arc.Center.Y, pt.X - arc.Center.X);
+        return arc.IsReversed
+            ? new Vector(System.Math.Sin(ang), -System.Math.Cos(ang))
+            : new Vector(-System.Math.Sin(ang), System.Math.Cos(ang));
+    }
+
+    private static double AngleBetweenDeg(Vector v1, Vector v2)
+    {
+        var l1 = System.Math.Sqrt(v1.X * v1.X + v1.Y * v1.Y);
+        var l2 = System.Math.Sqrt(v2.X * v2.X + v2.Y * v2.Y);
+        var dot = (v1.X * v2.X + v1.Y * v2.Y) / (l1 * l2);
+        dot = System.Math.Max(-1, System.Math.Min(1, dot));
+        return System.Math.Acos(dot) * 180.0 / System.Math.PI;
+    }
+
     [Fact]
     public void Apply_DynaPanDxf_NoGapsAfterSimplification()
     {

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/GravographISPostConfigTests.cs

@@ -0,0 +1,51 @@
+using OpenNest.CNC;
+using OpenNest.Posts.GravographIS;
+
+namespace OpenNest.Tests.GravographIS;
+
+public class GravographISPostConfigTests
+{
+    [Fact]
+    public void Defaults_EngraveBlock_NoPause_FasterFeed()
+    {
+        var config = new GravographISPostConfig();
+
+        Assert.Equal(10, config.Engrave.FeedMmPerSec);
+        Assert.False(config.Engrave.PauseBefore);
+    }
+
+    [Fact]
+    public void Defaults_CutBlock_PausesToChangeTool()
+    {
+        var config = new GravographISPostConfig();
+
+        Assert.Equal(3, config.Cut.FeedMmPerSec);
+        Assert.True(config.Cut.PauseBefore);
+        Assert.Equal("Change tool", config.Cut.PauseMessage);
+    }
+
+    [Theory]
+    [InlineData(LayerType.Scribe)]
+    public void ConfigFor_Scribe_ReturnsEngraveBlock(LayerType layer)
+    {
+        var config = new GravographISPostConfig();
+        Assert.Same(config.Engrave, config.ConfigFor(layer));
+    }
+
+    [Theory]
+    [InlineData(LayerType.Cut)]
+    [InlineData(LayerType.Leadin)]
+    [InlineData(LayerType.Leadout)]
+    public void ConfigFor_CutLayers_ReturnCutBlock(LayerType layer)
+    {
+        var config = new GravographISPostConfig();
+        Assert.Same(config.Cut, config.ConfigFor(layer));
+    }
+
+    [Fact]
+    public void ConfigFor_Display_ReturnsNull_SoItIsSkipped()
+    {
+        var config = new GravographISPostConfig();
+        Assert.Null(config.ConfigFor(LayerType.Display));
+    }
+}

OpenNest.Tests/GravographIS/GravographISPostProcessorTests.cs

@@ -0,0 +1,70 @@
+using System.Collections.Generic;
+using OpenNest.CNC;
+using OpenNest.Geometry;
+using OpenNest.Posts.GravographIS;
+
+namespace OpenNest.Tests.GravographIS;
+
+public class GravographISPostProcessorTests
+{
+    private static LayeredPolyline Poly(LayerType layer, params Vector[] pts)
+        => new LayeredPolyline(new List<Vector>(pts), layer);
+
+    [Fact]
+    public void BuildPasses_EngraveAndCut_OrdersEngraveFirstThenCutWithPause()
+    {
+        var post = new GravographISPostProcessor();
+
+        var passes = post.BuildPasses(new[]
+        {
+            Poly(LayerType.Cut, new Vector(0, 0), new Vector(1, 0)),
+            Poly(LayerType.Scribe, new Vector(0, 0), new Vector(0, 1)),
+        });
+
+        Assert.Equal(2, passes.Count);
+
+        Assert.Equal(post.Config.Engrave.FeedMmPerSec, passes[0].FeedMmPerSec);
+        Assert.False(passes[0].PauseBefore);
+
+        Assert.Equal(post.Config.Cut.FeedMmPerSec, passes[1].FeedMmPerSec);
+        Assert.True(passes[1].PauseBefore);
+        Assert.Equal("Change tool", passes[1].PauseMessage);
+    }
+
+    [Fact]
+    public void BuildPasses_CutOnly_IsSinglePass()
+    {
+        var post = new GravographISPostProcessor();
+
+        var passes = post.BuildPasses(new[]
+        {
+            Poly(LayerType.Cut, new Vector(0, 0), new Vector(1, 0)),
+        });
+
+        Assert.Single(passes);
+        Assert.Equal(post.Config.Cut.FeedMmPerSec, passes[0].FeedMmPerSec);
+    }
+
+    [Fact]
+    public void BuildPasses_SkipsDisplayGeometry()
+    {
+        var post = new GravographISPostProcessor();
+
+        var passes = post.BuildPasses(new[]
+        {
+            Poly(LayerType.Display, new Vector(0, 0), new Vector(1, 0)),
+            Poly(LayerType.Cut, new Vector(0, 0), new Vector(0, 1)),
+        });
+
+        Assert.Single(passes);
+        Assert.Equal(post.Config.Cut.FeedMmPerSec, passes[0].FeedMmPerSec);
+    }
+
+    [Fact]
+    public void Config_IsExposedThroughConfigurableInterface()
+    {
+        var post = new GravographISPostProcessor(new GravographISPostConfig());
+        OpenNest.IConfigurablePostProcessor configurable = post;
+        Assert.Same(post.Config, configurable.Config);
+    }
+}

OpenNest.Tests/GravographIS/GravographISWriterTests.cs

@@ -0,0 +1,318 @@
+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);
+    }
+
+    [Fact]
+    public void Passes_PauseBeforeCut_EmitsPauseSequenceBetweenGroups()
+    {
+        var engrave = new List<IReadOnlyList<Vector>> { new[] { new Vector(0, 0), new Vector(1, 0) } };
+        var cut = new List<IReadOnlyList<Vector>> { new[] { new Vector(0, 0), new Vector(0, -1) } };
+        var passes = new List<GravographPass>
+        {
+            new GravographPass { Polylines = engrave, FeedMmPerSec = 10, DepthInches = 0.25 },
+            new GravographPass { Polylines = cut, FeedMmPerSec = 3, DepthInches = 0.25, PauseBefore = true, PauseMessage = "Hi" },
+        };
+
+        using var ms = new MemoryStream();
+        new GravographISWriter(new GravographISWriterOptions
+        {
+            EnvelopeGuardEnabled = false,
+            ReturnToOriginAtEnd = false,
+        }).Write(passes, ms);
+        var bytes = ms.ToArray();
+
+        var mcOff = IndexOf(bytes, 0, (byte)'M', (byte)'C', 0x00, 0x00);
+        var ouFb = IndexOf(bytes, mcOff, (byte)'O', (byte)'U', 0xFF, 0xFB);
+        var ouFa = IndexOf(bytes, ouFb, (byte)'O', (byte)'U', 0xFF, 0xFA);
+        var lbBegin = IndexOf(bytes, ouFa, (byte)'L', (byte)'B', 0x00, 0x00);
+        var lbMsg = IndexOf(bytes, lbBegin, (byte)'L', (byte)'B', (byte)'H', (byte)'i');
+        var nr = IndexOf(bytes, lbMsg, (byte)'N', (byte)'R', 0x00, 0x01);
+        var lbEnd = IndexOf(bytes, nr, (byte)'L', (byte)'B', 0x00, 0x01);
+        var mcOn = IndexOf(bytes, lbEnd, (byte)'M', (byte)'C', 0x00, 0x01);
+
+        Assert.True(mcOff >= 0, "motor-off (MC 0000) not found");
+        Assert.True(mcOff < ouFb && ouFb < ouFa && ouFa < lbBegin && lbBegin < lbMsg
+            && lbMsg < nr && nr < lbEnd && lbEnd < mcOn,
+            "pause commands out of order");
+
+        // Resume sets the cut feed inline (VS 0x0003) after the motor restarts.
+        var vsCut = IndexOf(bytes, mcOn, (byte)'V', (byte)'S', 0x00, 0x03);
+        Assert.True(vsCut > mcOn, "cut feed not set after resume");
+    }
+
+    [Fact]
+    public void Passes_PauseOddMessage_SpacePadsLastPacket()
+    {
+        var passes = new List<GravographPass>
+        {
+            new GravographPass { Polylines = new List<IReadOnlyList<Vector>> { new[] { new Vector(0, 0), new Vector(1, 0) } }, FeedMmPerSec = 10 },
+            new GravographPass { Polylines = new List<IReadOnlyList<Vector>> { new[] { new Vector(0, 0), new Vector(0, -1) } }, FeedMmPerSec = 3, PauseBefore = true, PauseMessage = "abc" },
+        };
+
+        using var ms = new MemoryStream();
+        new GravographISWriter(new GravographISWriterOptions { EnvelopeGuardEnabled = false, ReturnToOriginAtEnd = false }).Write(passes, ms);
+        var bytes = ms.ToArray();
+
+        var lbAb = IndexOf(bytes, 0, (byte)'L', (byte)'B', (byte)'a', (byte)'b');
+        var lbCPad = IndexOf(bytes, lbAb, (byte)'L', (byte)'B', (byte)'c', 0x20);
+        Assert.True(lbAb >= 0, "first message packet 'ab' not found");
+        Assert.True(lbCPad > lbAb, "odd packet not space-padded to 'c '");
+    }
+
+    [Fact]
+    public void Passes_DifferentFeeds_NoPause_EmitsInlineFeedChangeNoMessage()
+    {
+        var passes = new List<GravographPass>
+        {
+            new GravographPass { Polylines = new List<IReadOnlyList<Vector>> { new[] { new Vector(0, 0), new Vector(1, 0) } }, FeedMmPerSec = 10 },
+            new GravographPass { Polylines = new List<IReadOnlyList<Vector>> { new[] { new Vector(0, 0), new Vector(0, -1) } }, FeedMmPerSec = 3, PauseBefore = false },
+        };
+
+        using var ms = new MemoryStream();
+        new GravographISWriter(new GravographISWriterOptions { EnvelopeGuardEnabled = false, ReturnToOriginAtEnd = false }).Write(passes, ms);
+        var bytes = ms.ToArray();
+
+        Assert.True(IndexOf(bytes, 0, (byte)'V', (byte)'S', 0x00, 0x03) >= 0, "inline cut feed change missing");
+        Assert.True(IndexOfCmd(bytes, (byte)'L', (byte)'B') < 0, "no LB message expected without a pause");
+    }
+
+    private static int IndexOf(byte[] bytes, int from, byte c0, byte c1, byte hi, byte lo)
+    {
+        for (var i = System.Math.Max(0, from); i <= bytes.Length - 6; 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 int IndexOfCmd(byte[] bytes, byte c0, byte c1)
+    {
+        for (var i = 0; i <= bytes.Length - 4; i++)
+        {
+            if (bytes[i] == 0xFF && bytes[i + 1] == 0xFD && bytes[i + 2] == c0 && bytes[i + 3] == c1)
+                return i;
+        }
+        return -1;
+    }
+
+    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 +1,78 @@
+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]);
+    }
+
+    [Fact]
+    public void ExtractPartLayered_SplitsContinuousChainAtLayerChange()
+    {
+        // A single continuous chain (no rapid) that switches from Scribe to Cut
+        // must be split into two layer-uniform polylines sharing the seam vertex,
+        // so the post can emit a tool-change pause between engrave and cut.
+        var program = new Program(Mode.Absolute);
+        program.Codes.Add(new LinearMove(1, 0) { Layer = LayerType.Scribe });
+        program.Codes.Add(new LinearMove(2, 0) { Layer = LayerType.Scribe });
+        program.Codes.Add(new LinearMove(2, 1) { Layer = LayerType.Cut });
+        program.Codes.Add(new LinearMove(3, 1) { Layer = LayerType.Cut });
+
+        var drawing = new Drawing("Mixed", program);
+        var part = new Part(drawing, new Vector(0, 0));
+
+        var polylines = new NestPolylineExtractor().ExtractPartLayered(part);
+
+        Assert.Equal(2, polylines.Count);
+
+        Assert.Equal(LayerType.Scribe, polylines[0].Layer);
+        Assert.Equal(new[] { new Vector(0, 0), new Vector(1, 0), new Vector(2, 0) }, polylines[0].Points);
+
+        Assert.Equal(LayerType.Cut, polylines[1].Layer);
+        Assert.Equal(new[] { new Vector(2, 0), new Vector(2, 1), new Vector(3, 1) }, polylines[1].Points);
+    }
+
+    [Fact]
+    public void ExtractPartLayered_UniformChain_IsSinglePolyline()
+    {
+        var program = new Program(Mode.Absolute);
+        program.Codes.Add(new LinearMove(1, 0));
+        program.Codes.Add(new LinearMove(1, 1));
+
+        var part = new Part(new Drawing("Cut", program), new Vector(0, 0));
+
+        var polylines = new NestPolylineExtractor().ExtractPartLayered(part);
+
+        Assert.Single(polylines);
+        Assert.Equal(LayerType.Cut, polylines[0].Layer);
+    }
+}

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/Actions/ActionCutOff.cs

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

OpenNest/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>