refactor(engine): rename the Default engine and fill strategy to Fill

The multi-phase lattice fill (linear, pairs, rectangle best-fit, remainder) is
no longer meant to be the engine used by default, so it gets a name for what
it does. The registry lists it as Fill and maps the old name Default to it;
PlateFillService, PlateNesterFactory and NestJobOptions use Fill, and every
fill-strategy caller still accepts Default. Console --autonest now validates
engine names through NestingEngineRegistry.ResolveName so renamed names work.

Layouts are unchanged: Default and Fill resolve to the same fillers and the
golden layouts pass under the new name.

OpenNest.Benchmark/BenchmarkJob.cs

@@ -83,7 +83,7 @@ namespace OpenNest.Benchmark
                 parts,
                 stock,
                 new NestJobOptions(
-                    "Default",
+                    "Fill",
                     maxPlates,
                     salvageRate ?? SalvageRate,
                     minimumSalvageDimension ?? 0

OpenNest.Console/Program.cs

@@ -79,10 +79,8 @@ static class NestConsole
         // single-plate placement strategy. Unknown names exit with the valid choices.
         if (options.AutoNest)
         {
-            var isJobsEngine = NestingEngineRegistry.AvailableEngines.Any(e =>
-                e.Name.Equals(options.Engine, StringComparison.OrdinalIgnoreCase)
-            );
-            if (!isJobsEngine)
+            // ResolveName also accepts renamed engines' old names (for example Default).
+            if (NestingEngineRegistry.ResolveName(options.Engine) == null)
             {
                 Console.Error.WriteLine(
                     $"Error: unknown engine '{options.Engine}'. Jobs engines: {string.Join(", ", NestingEngineRegistry.AvailableEngines.Select(e => e.Name))}"
@@ -764,8 +762,8 @@ static class NestConsole
               --template <path>      Nest template for plate defaults (thickness, quadrant, material, spacing)
               --autonest             Validated whole-job nesting onto one sheet; replaces only after acceptance
               --allow-invalid        Explicitly keep representable invalid autonest layouts (default: reject, exit 2)
-              --engine <name>        With --autonest: jobs engine (default: Default; also StockLadder, Strip, ...).
-                                     Without --autonest: fill strategy (Default, Strip, Vertical Remnant, Horizontal Remnant)
+              --engine <name>        With --autonest: jobs engine (default: Default; also Irregular, Rectangles, Fill, ...).
+                                     Without --autonest: fill strategy (Fill (default), Strip, Vertical Remnant, Horizontal Remnant)
               --keep-parts           Don't clear existing parts before filling
               --check-overlaps       Run overlap detection after fill (exit code 1 if found)
               --no-save              Skip saving output file

OpenNest.Engine.Tests/FillStrategyNameTests.cs

@@ -0,0 +1,81 @@
+using OpenNest.Engine.Jobs;
+using OpenNest.Engine.Jobs.Placement;
+using OpenNest.Engine.Tests.Jobs;
+using OpenNest.Geometry;
+
+namespace OpenNest.Engine.Tests;
+
+/// <summary>
+/// The fill engine and placement strategy are named "Fill"; the old name "Default" remains a
+/// hidden alias so saved selections, scripts and API requests keep their behavior.
+/// </summary>
+public class FillStrategyNameTests
+{
+    [Fact]
+    public void FillIsListedAndDefaultIsNot()
+    {
+        var engines = NestingEngineRegistry.AvailableEngines.Select(e => e.Name).ToList();
+
+        Assert.Contains("Fill", engines);
+        Assert.DoesNotContain("Default", engines, StringComparer.OrdinalIgnoreCase);
+        Assert.Equal(new[] { "Fill", "Strip", "Vertical Remnant", "Horizontal Remnant" },
+            PlateFillService.BuiltInStrategies);
+    }
+
+    [Theory]
+    [InlineData("Default")]
+    [InlineData(" default ")]
+    public void LegacyDefaultEngineNameResolvesToFill(string name)
+    {
+        Assert.Equal("Fill", NestingEngineRegistry.ResolveName(name));
+        Assert.IsType<FixedStrategyNestingEngine>(NestingEngineRegistry.Create(name));
+        Assert.Equal(NestJobStatus.Complete, NestingEngineRegistry.Create(name).Solve(FiniteStockJobTests.Job(1)).Status);
+    }
+
+    [Fact]
+    public void PlugInNamedDefaultCannotShadowFill()
+    {
+        var before = NestingEngineRegistry.AvailableEngines.Count;
+
+        NestingEngineRegistry.Register("Default", "stale plug-in", () => new FixedStrategyNestingEngine("Strip"));
+
+        Assert.Equal(before, NestingEngineRegistry.AvailableEngines.Count);
+        Assert.Equal("Fill", NestingEngineRegistry.ResolveName("Default"));
+    }
+
+    [Theory]
+    [InlineData(null, "Fill")]
+    [InlineData("", "Fill")]
+    [InlineData("fill", "Fill")]
+    [InlineData("Default", "Fill")]
+    [InlineData("DEFAULT", "Fill")]
+    public void PlacementStrategyResolvesFillAndItsLegacyName(string? strategy, string expected)
+    {
+        Assert.Equal(expected, PlateFillService.ResolveStrategy(strategy!));
+    }
+
+    [Fact]
+    public void LegacyStrategyNameStillFillsAPlate()
+    {
+        var plate = new Plate(new Size(60, 80));
+        var drawing = new Drawing("part", TestDrawingFactory.Rectangle(6, 4));
+
+        var parts = PlateFillService.FillItem("Default", plate,
+            new NestItem { Drawing = drawing, Quantity = 6 }, plate.WorkArea(), null, CancellationToken.None);
+
+        Assert.Equal(6, parts.Count);
+    }
+
+    [Fact]
+    public void WholeJobRunnerAcceptsFillAndItsLegacyName()
+    {
+        Assert.IsType<DefaultPlateNester>(PlateNesterFactory.Create("Fill"));
+        Assert.IsType<DefaultPlateNester>(PlateNesterFactory.Create("Default"));
+        Assert.Equal("Fill", new NestJobOptions().PlacementStrategy);
+
+        var job = FiniteStockJobTests.Job(1);
+        var legacy = new NestJobRunner(PlateNesterFactory.Create)
+            .Solve(new NestJob(job.Parts, job.Plates, new NestJobOptions("Default")));
+        Assert.Equal(NestJobStatus.Complete, legacy.Status);
+    }
+}

OpenNest.Engine.Tests/Jobs/Cutouts/CutoutLatticeFillTests.cs

@@ -54,7 +54,7 @@ public class CutoutLatticeFillTests
     }
 
     // Both cases fail intermittently; unskip when Project Memory opennest issue c98c21bd is fixed.
-    private const string FillNondeterminism = "Open defect (Project Memory opennest c98c21bd): Default Fill can "
+    private const string FillNondeterminism = "Open defect (Project Memory opennest c98c21bd): Fill can "
         + "return different, equally scored lattices between identical calls.";
 
     [Theory]

OpenNest.Engine.Tests/Jobs/FixedStrategyNestingEngineTests.cs

@@ -22,7 +22,7 @@ public class FixedStrategyNestingEngineTests
     [Fact]
     public void PreservesJobMaxPlates()
     {
-        var engine = new FixedStrategyNestingEngine("Default");
+        var engine = new FixedStrategyNestingEngine("Fill");
         var part = new NestJobPart(
             "part",
             PartGeometrySnapshot.FromProgram(TestDrawingFactory.Rectangle(100, 100)),
@@ -39,7 +39,7 @@ public class FixedStrategyNestingEngineTests
         var job = new NestJob(
             new[] { part },
             new[] { stock },
-            new NestJobOptions("Default", maxPlates: 1)
+            new NestJobOptions("Fill", maxPlates: 1)
         );
 
         var result = engine.Solve(job);

OpenNest.Engine.Tests/Jobs/GoldenLayoutTests.cs

@@ -165,7 +165,7 @@ public class GoldenLayoutTests
     [Fact]
     public void Default_MixedJob_GoldenLayout()
     {
-        var result = SolveStable(new NestJobRunner(PlateNesterFactory.Create), MixedJob("Default"));
+        var result = SolveStable(new NestJobRunner(PlateNesterFactory.Create), MixedJob("Fill"));
         Assert.Equal(NestJobStatus.Complete, result.Status);
         Assert.Equal(20, result.Plates.Sum(p => p.Placements.Count));
         AssertGolden(
@@ -299,7 +299,7 @@ public class GoldenLayoutTests
     [Fact]
     public void OrderedViaStockLadder_MixedJob_GoldenLayout()
     {
-        var result = SolveStable(new StockLadderNestingEngine(), MixedJob("Default"));
+        var result = SolveStable(new StockLadderNestingEngine(), MixedJob("Fill"));
         Assert.Equal(NestJobStatus.Complete, result.Status);
         AssertGolden(
             result,
@@ -338,7 +338,7 @@ public class GoldenLayoutTests
                 new NestPlateStock("small", new Size(14, 14), 4, 1, new Spacing(1, 1, 1, 1)),
                 new NestPlateStock("large", new Size(30, 24), 3, 1, new Spacing(1, 1, 1, 1)),
             },
-            new NestJobOptions("Default")
+            new NestJobOptions("Fill")
         );
 
     private sealed record AuthoritativeStage(
@@ -408,7 +408,7 @@ public class GoldenLayoutTests
     {
         var stages = new List<AuthoritativeStage>();
         var legacyPhases = new SortedSet<string>();
-        var result = new FixedStrategyNestingEngine("Default").Solve(
+        var result = new FixedStrategyNestingEngine("Fill").Solve(
             ProgressJob(),
             new StageCollector(stages, legacyPhases)
         );

OpenNest.Engine.Tests/Jobs/NestJobEngineSelectionTests.cs

@@ -27,7 +27,7 @@ public class NestJobEngineSelectionTests
     [Fact]
     public void FactoryResolvesEachNamedBuiltInStrategy()
     {
-        var defaultNester = PlateNesterFactory.Create("Default");
+        var defaultNester = PlateNesterFactory.Create("Fill");
         var stripNester = PlateNesterFactory.Create("Strip");
         var verticalNester = PlateNesterFactory.Create("Vertical Remnant");
         var horizontalNester = PlateNesterFactory.Create("Horizontal Remnant");

OpenNest.Engine.Tests/Jobs/NestJobExampleTests.cs

@@ -145,7 +145,7 @@ public class NestJobExampleTests
                     quadrant: 1
                 ),
             },
-            new NestJobOptions("Default", maxPlates: 1)
+            new NestJobOptions("Fill", maxPlates: 1)
         );
 
         var result = new NestJobRunner(PlateNesterFactory.Create).Solve(job);
@@ -172,7 +172,7 @@ public class NestJobExampleTests
         var item = new NestItem { Drawing = drawing, Quantity = 1 };
 
         var parts = PlateFillService.Nest(
-            "Default",
+            "Fill",
             plate,
             new List<NestItem> { item },
             progress: null,

OpenNest.Engine.Tests/Jobs/NestJobGeometryTests.cs

@@ -260,7 +260,7 @@ public class NestJobGeometryTests
     }
 
     [Theory]
-    [InlineData("Default")]
+    [InlineData("Fill")]
     [InlineData("Strip")]
     public void RealEngineSmokeCasesPreserveInputAndProduceSafeAccounting(string strategy)
     {

OpenNest.Engine.Tests/Jobs/NestJobRunnerTests.cs

@@ -105,7 +105,7 @@ public class NestJobRunnerTests
         Assert.Equal(100, job.Plates[0].Size.Width);
         Assert.Equal(1, job.Plates[0].EdgeSpacing.Left);
         Assert.Equal(0, job.Plates[0].Quantity);
-        Assert.Equal("Default", job.Options.PlacementStrategy);
+        Assert.Equal("Fill", job.Options.PlacementStrategy);
         Assert.Throws<NotSupportedException>(() => ((IList<NestJobPart>)job.Parts).Clear());
     }
 

OpenNest.Engine.Tests/Jobs/NestPipelineTests.cs

@@ -43,7 +43,7 @@ public class NestPipelineTests
         var item = Item("bracket", 10);
         var codes = item.Drawing.Program.Codes.Count;
 
-        var result = NestPipeline.Run(Request("Default", item));
+        var result = NestPipeline.Run(Request("Fill", item));
 
         Assert.True(result.IsValid, string.Join("; ", result.Violations));
         Assert.True(result.CanKeep);
@@ -240,7 +240,7 @@ public class NestPipelineTests
             NestPipeline.Run(Request("Mystery Engine", Item("bracket", 1)))
         );
 
-        Assert.Contains("Default", error.Message);
+        Assert.Contains("Fill", error.Message);
     }
 
     [Fact]
@@ -265,7 +265,7 @@ public class NestPipelineTests
         cts.Cancel();
 
         Assert.ThrowsAny<OperationCanceledException>(() =>
-            NestPipeline.Run(Request("Default", Item("bracket", 1)), null, cts.Token)
+            NestPipeline.Run(Request("Fill", Item("bracket", 1)), null, cts.Token)
         );
     }
 }

OpenNest.Engine.Tests/Jobs/NestingEngineRegistryTests.cs

@@ -12,7 +12,7 @@ public class NestingEngineRegistryTests
 
         Assert.Contains("Rectangles", names);
         Assert.Contains("Irregular", names);
-        Assert.Contains("Default", names);
+        Assert.Contains("Fill", names);
         Assert.Contains("Strip", names);
         Assert.Contains("Vertical Remnant", names);
         Assert.Contains("Horizontal Remnant", names);
@@ -43,7 +43,7 @@ public class NestingEngineRegistryTests
         var before = NestingEngineRegistry.AvailableEngines.Count;
 
         NestingEngineRegistry.Register("Opus55NestingEngine", "stale plug-in",
-            () => new FixedStrategyNestingEngine("Default"));
+            () => new FixedStrategyNestingEngine("Fill"));
 
         Assert.Equal(before, NestingEngineRegistry.AvailableEngines.Count);
         Assert.Equal("Irregular", NestingEngineRegistry.ResolveName("Opus55NestingEngine"));
@@ -67,9 +67,9 @@ public class NestingEngineRegistryTests
         var before = NestingEngineRegistry.AvailableEngines.Count;
 
         NestingEngineRegistry.Register(
-            "Default",
+            "Fill",
             "duplicate",
-            () => new FixedStrategyNestingEngine("Default")
+            () => new FixedStrategyNestingEngine("Fill")
         );
 
         Assert.Equal(before, NestingEngineRegistry.AvailableEngines.Count);
@@ -78,7 +78,7 @@ public class NestingEngineRegistryTests
     [Fact]
     public void CreateResolvesKnownNamesCaseInsensitivelyAndRejectsUnknown()
     {
-        Assert.NotNull(NestingEngineRegistry.Create("default"));
+        Assert.NotNull(NestingEngineRegistry.Create("fill"));
         Assert.NotNull(NestingEngineRegistry.Create("Vertical Remnant"));
         Assert.NotNull(NestingEngineRegistry.Create("stockladder"));
 

OpenNest.Engine.Tests/Jobs/PlateFillerContractTests.cs

@@ -8,7 +8,7 @@ namespace OpenNest.Engine.Tests.Jobs;
 public class PlateFillerContractTests
 {
     [Theory]
-    [InlineData("Default")]
+    [InlineData("Fill")]
     [InlineData("Vertical Remnant")]
     [InlineData("Horizontal Remnant")]
     public void StandardPlateFiller_Fill_ReturnsPartsBoundToInputDrawing(string strategy)
@@ -353,7 +353,7 @@ public class PlateFillerContractTests
 
     private static PlateFillerBase CreateFiller(string strategy, Plate plate) => strategy switch
     {
-        "Default" => new DefaultPlateFiller(plate),
+        "Fill" => new DefaultPlateFiller(plate),
         "Vertical Remnant" => new RemnantPlateFiller(plate, RemnantFillPolicy.Vertical),
         "Horizontal Remnant" => new RemnantPlateFiller(plate, RemnantFillPolicy.Horizontal),
         _ => throw new ArgumentOutOfRangeException(nameof(strategy)),

OpenNest.Engine.Tests/Jobs/PlateNesterParityTests.cs

@@ -22,7 +22,7 @@ public class PlateNesterParityTests
     private static NestJob Job(
         IReadOnlyList<NestJobPart> parts,
         int? stockQuantity = 3,
-        string strategy = "Default"
+        string strategy = "Fill"
     )
     {
         var stock = new NestPlateStock("stock", PlateSize, stockQuantity, 1, Edge);
@@ -97,7 +97,7 @@ public class PlateNesterParityTests
     [Fact]
     public void Builtins_AreResolvedByProductionFactory()
     {
-        Assert.IsType<DefaultPlateNester>(PlateNesterFactory.Create("Default"));
+        Assert.IsType<DefaultPlateNester>(PlateNesterFactory.Create("Fill"));
         Assert.IsType<StripPlateNester>(PlateNesterFactory.Create("Strip"));
         Assert.IsType<RemnantPlateNester>(PlateNesterFactory.Create("Vertical Remnant"));
         Assert.IsType<RemnantPlateNester>(PlateNesterFactory.Create("Horizontal Remnant"));
@@ -234,7 +234,7 @@ public class PlateNesterParityTests
     [Fact]
     public void RemnantRestrictedRotation_NeverTouchesFiller()
     {
-        // Same safety rule for the remnant nester, whose fillers inherit the Default pipeline's
+        // Same safety rule for the remnant nester, whose fillers inherit the Fill pipeline's
         // automatic-rotation limitation. The throwing factory proves the filler is never
         // constructed; completion at the locked angle proves OrderedPlateNester handled it.
         var part = new NestJobPart(

OpenNest.Engine.Tests/PlateFillServiceTests.cs

@@ -9,7 +9,7 @@ public class PlateFillServiceTests
 {
     private static readonly string[] Strategies =
     [
-        "Default",
+        "Fill",
         "Strip",
         "Vertical Remnant",
         "Horizontal Remnant",
@@ -44,7 +44,7 @@ public class PlateFillServiceTests
         var drawing = new Drawing("part", TestDrawingFactory.Rectangle(6, 4));
 
         var parts = PlateFillService.FillItem(
-            "Default",
+            "Fill",
             plate,
             new NestItem { Drawing = drawing, Quantity = 6 },
             plate.WorkArea(),
@@ -120,7 +120,7 @@ public class PlateFillServiceTests
         // The plateNumber overload reports the caller's plate index like the legacy
         // engine's PlateNumber did for interactive multi-plate loops.
         var progress = new CapturingProgress();
-        var parts = PlateFillService.Nest("Default", plate, items, 3, progress, CancellationToken.None);
+        var parts = PlateFillService.Nest("Fill", plate, items, 3, progress, CancellationToken.None);
 
         Assert.NotEmpty(parts);
         Assert.NotEmpty(progress.Reports);
@@ -217,7 +217,7 @@ public class PlateFillServiceTests
         var drawing = new Drawing("part", TestDrawingFactory.Rectangle(6, 4));
 
         Assert.Throws<ArgumentNullException>(() =>
-            PlateFillService.FillItem("Default", null!, new NestItem { Drawing = drawing, Quantity = 1 }, new Box(0, 0, 10, 10), null, CancellationToken.None)
+            PlateFillService.FillItem("Fill", null!, new NestItem { Drawing = drawing, Quantity = 1 }, new Box(0, 0, 10, 10), null, CancellationToken.None)
         );
     }
 

OpenNest.Engine.Tests/RectanglePacking/AreaPackerTests.cs

@@ -61,8 +61,8 @@ public class AreaPackerTests
         var area = plate.WorkArea();
         var items = new List<NestItem> { Item("panel", 10 + SheetPacker.OverhangAllowance * 0.8, 4, 2) };
 
-        var parts = PlateFillService.PackArea("Default", plate, area, items, null, CancellationToken.None);
-        var again = PlateFillService.PackArea("Default", plate, area, items, null, CancellationToken.None);
+        var parts = PlateFillService.PackArea("Fill", plate, area, items, null, CancellationToken.None);
+        var again = PlateFillService.PackArea("Fill", plate, area, items, null, CancellationToken.None);
 
         Assert.Equal(2, parts.Count);
         Assert.Equal(parts.Select(p => (p.Location, p.Rotation)), again.Select(p => (p.Location, p.Rotation)));
@@ -92,7 +92,7 @@ public class AreaPackerTests
         };
         var area = plate.WorkArea();
         var items = new List<NestItem> { Item("panel", 4, 10 + SheetPacker.OverhangAllowance * 0.8, 2) };
-        var parts = PlateFillService.PackArea("Default", plate, area, items, null, CancellationToken.None);
+        var parts = PlateFillService.PackArea("Fill", plate, area, items, null, CancellationToken.None);
 
         Assert.Equal(2, parts.Count);
         Assert.All(parts, p =>
@@ -117,7 +117,7 @@ public class AreaPackerTests
         var items = new List<NestItem> { rotated ? Item("panel", 6 + excess, 10 + excess, 1)
             : Item("panel", 10 + excess, 6 + excess, 1) };
 
-        var part = Assert.Single(PlateFillService.PackArea("Default", plate, plate.WorkArea(), items, null, CancellationToken.None));
+        var part = Assert.Single(PlateFillService.PackArea("Fill", plate, plate.WorkArea(), items, null, CancellationToken.None));
 
         Assert.True(part.BoundingBox.Right <= 10 + NestTolerances.WorkAreaSlack);
         Assert.True(part.BoundingBox.Top <= 6 + NestTolerances.WorkAreaSlack);
@@ -130,7 +130,7 @@ public class AreaPackerTests
     {
         var plate = new Plate(new Size(6, 10)) { PartSpacing = spacing };
         var items = new List<NestItem> { Item("panel", 10 + NestTolerances.WorkAreaSlack * 1.1, 4, 1) };
-        Assert.Empty(PlateFillService.PackArea("Default", plate, plate.WorkArea(), items, null, CancellationToken.None));
+        Assert.Empty(PlateFillService.PackArea("Fill", plate, plate.WorkArea(), items, null, CancellationToken.None));
     }
 
     [Theory]
@@ -144,7 +144,7 @@ public class AreaPackerTests
         var area = new Box(x, y, w, h);
         var excess = SheetPacker.OverhangAllowance * 0.8;
         var items = new List<NestItem> { w == 5 ? Item("panel", w + excess, h - 0.25, 1) : Item("panel", 8, h + excess, 1) };
-        var parts = PlateFillService.PackArea("Default", plate, area, items, null, CancellationToken.None);
+        var parts = PlateFillService.PackArea("Fill", plate, area, items, null, CancellationToken.None);
         Assert.Equal(fits ? 1 : 0, parts.Count);
     }
 
@@ -181,7 +181,7 @@ public class AreaPackerTests
         var area = new Box(0, 0, 12, 12);
         var items = new List<NestItem> { Item("tall", 5, 7, 3), Item("small", 4, 3, 2) };
 
-        var parts = PlateFillService.PackArea("Default", plate, area, items, null, CancellationToken.None);
+        var parts = PlateFillService.PackArea("Fill", plate, area, items, null, CancellationToken.None);
 
         Assert.Equal(5, parts.Count);
         Assert.Equal(3, parts.Count(p => p.BaseDrawing.Name == "tall"));

OpenNest.Engine/Jobs/Cutouts/CutoutLatticeFill.cs

@@ -100,7 +100,7 @@ internal static class CutoutLatticeFill
             .Select((p, index) => p with { InstanceIndex = index }).ToArray();
     }
 
-    /// <summary>Default Fill over the cutout's bounds grown by one step on every side, in frame
+    /// <summary>Fill over the cutout's bounds grown by one step on every side, in frame
     /// coordinates. Fill places whole parts only, so the margin keeps every offset covered.</summary>
     private static List<NestJobPlacement> Lattice(NestJobPart insert, Box bounds, double step, double spacing,
         CancellationToken token)

OpenNest.Engine/Jobs/NestJobOptions.cs

@@ -6,7 +6,7 @@ namespace OpenNest.Engine.Jobs;
 public sealed class NestJobOptions
 {
     public NestJobOptions(
-        string placementStrategy = "Default",
+        string placementStrategy = "Fill",
         int? maxPlates = null,
         double salvageRate = 0,
         double minimumSalvageDimension = 0

OpenNest.Engine/Jobs/NestingEngineRegistry.cs

@@ -28,6 +28,7 @@ public static class NestingEngineRegistry
     {
         ["Opus55NestingEngine"] = "Irregular",
         ["RectanglesNestingEngine"] = "Rectangles",
+        ["Default"] = "Fill",
     };
 
     static NestingEngineRegistry()
@@ -51,9 +52,9 @@ public static class NestingEngineRegistry
         );
 
         Register(
-            "Default",
+            "Fill",
             "Multi-phase nesting (Linear, Pairs, RectBestFit, Remainder)",
-            () => new FixedStrategyNestingEngine("Default")
+            () => new FixedStrategyNestingEngine("Fill")
         );
 
         Register(

OpenNest.Engine/Jobs/Placement/PlateFillService.cs

@@ -15,10 +15,16 @@ namespace OpenNest.Engine.Jobs.Placement;
 /// </summary>
 public static class PlateFillService
 {
+    /// <summary>Strategy used when a caller selection names none.</summary>
+    public const string DefaultStrategy = "Fill";
+
+    /// <summary>Name of the Fill strategy in earlier releases; accepted as an alias.</summary>
+    private const string LegacyFillName = "Default";
+
     /// <summary>The four built-in strategy names, in registry display order.</summary>
     public static IReadOnlyList<string> BuiltInStrategies { get; } =
     [
-        "Default",
+        "Fill",
         "Strip",
         "Vertical Remnant",
         "Horizontal Remnant",
@@ -91,9 +97,10 @@ public static class PlateFillService
     }
 
     /// <summary>
-    /// Resolves a caller-supplied strategy name: null or empty means "Default"; otherwise the name
+    /// Resolves a caller-supplied strategy name: null or empty means "Fill"; otherwise the name
     /// must match a built-in strategy, matched case-insensitively like the legacy registry's
-    /// ActiveEngineName so tolerant interactive callers keep working. Returns the canonical name;
+    /// ActiveEngineName so tolerant interactive callers keep working. "Default", the Fill
+    /// strategy's name in earlier releases, still resolves to "Fill". Returns the canonical name;
     /// unknown names throw <see cref="NotSupportedException"/>.
     /// </summary>
     public static string ResolveStrategy(string strategy) => ResolveStrategy(strategy, true);
@@ -105,12 +112,14 @@ public static class PlateFillService
         if (string.IsNullOrWhiteSpace(strategy))
         {
             if (allowEmpty)
-                return "Default";
+                return DefaultStrategy;
             throw new NotSupportedException(
                 $"Unknown placement strategy: '{strategy}'. Known strategies: {string.Join(", ", BuiltInStrategies)}."
             );
         }
 
+        if (strategy.Equals(LegacyFillName, StringComparison.OrdinalIgnoreCase))
+            return DefaultStrategy;
         foreach (var candidate in BuiltInStrategies)
         {
             if (candidate.Equals(strategy, StringComparison.OrdinalIgnoreCase))
@@ -122,13 +131,13 @@ public static class PlateFillService
         );
     }
 
-    /// <summary>Builds the filler for an optional strategy (null/empty = Default).</summary>
+    /// <summary>Builds the filler for an optional strategy (null/empty = Fill).</summary>
     private static PlateFillerBase CreateFiller(string strategy, Plate plate)
     {
         ArgumentNullException.ThrowIfNull(plate);
         return ResolveStrategy(strategy) switch
         {
-            "Default" => new DefaultPlateFiller(plate),
+            "Fill" => new DefaultPlateFiller(plate),
             "Strip" => new StripPlateFiller(plate),
             "Vertical Remnant" => new RemnantPlateFiller(plate, RemnantFillPolicy.Vertical),
             _ => new RemnantPlateFiller(plate, RemnantFillPolicy.Horizontal),
@@ -140,7 +149,7 @@ public static class PlateFillService
     {
         ArgumentNullException.ThrowIfNull(strategy);
         // An explicit empty string is an unknown strategy; only ResolveStrategy(string),
-        // used for caller selections, maps null/empty to Default.
+        // used for caller selections, maps null/empty to Fill.
         ResolveStrategy(strategy, allowEmpty: false);
         return CreateFiller(strategy, plate);
     }

OpenNest.Engine/Jobs/Placement/PrivatePlateFill.cs

@@ -10,7 +10,7 @@ using OpenNest.Geometry;
 namespace OpenNest.Engine.Jobs.Placement;
 
 /// <summary>
-/// Runs the Default Fill for one private drawing on a private plate, for callers that turn the
+/// Runs the Fill strategy for one private drawing on a private plate, for callers that turn the
 /// result into job poses. The caller owns the drawing and must call
 /// <see cref="BestFitCache.Invalidate"/> for it when finished.
 /// </summary>

OpenNest.Engine/Jobs/Placement/RemnantPlateNester.cs

@@ -13,8 +13,8 @@ namespace OpenNest.Engine.Jobs.Placement;
 /// <see cref="DefaultPlateNester"/>.
 /// </summary>
 /// <remarks>
-/// The remnant fillers share the Default pipeline's automatic-rotation limitation, so non-automatic
-/// requirements route through <see cref="OrderedPlateNester"/> exactly as they do for Default.
+/// The remnant fillers share the Fill pipeline's automatic-rotation limitation, so non-automatic
+/// requirements route through <see cref="OrderedPlateNester"/> exactly as they do for Fill.
 /// </remarks>
 public sealed class RemnantPlateNester : IPlateNester
 {
@@ -45,7 +45,7 @@ public sealed class RemnantPlateNester : IPlateNester
         ArgumentNullException.ThrowIfNull(request);
         token.ThrowIfCancellationRequested();
 
-        // Same safety rule as DefaultPlateNester: the remnant fillers inherit the Default pipeline's
+        // Same safety rule as DefaultPlateNester: the remnant fillers inherit the Fill pipeline's
         // automatic-rotation limitation, so any non-automatic requirement goes to the policy-aware
         // ordered nester.
         if (request.Parts.Any(part => part.Rotation.Kind != RotationPolicyKind.Automatic))

OpenNest.Engine/Jobs/PlateNesterFactory.cs

@@ -15,7 +15,8 @@ public static class PlateNesterFactory
         ArgumentNullException.ThrowIfNull(strategy);
         return strategy switch
         {
-            "Default" => new DefaultPlateNester(),
+            // "Default" is the strategy's name in earlier releases.
+            "Fill" or "Default" => new DefaultPlateNester(),
             "Strip" => new StripPlateNester(),
             "Vertical Remnant" => RemnantPlateNester.Vertical(),
             "Horizontal Remnant" => RemnantPlateNester.Horizontal(),

OpenNest.Mcp/Tools/NestingTools.cs

@@ -31,7 +31,7 @@ namespace OpenNest.Mcp.Tools
             [Description("Index of the plate to fill")] int plateIndex,
             [Description("Name of the drawing to fill with")] string drawingName,
             [Description("Maximum quantity to place (0 = unlimited)")] int quantity = 0,
-            [Description("Placement strategy: Default, Strip, Vertical Remnant, Horizontal Remnant")]
+            [Description("Placement strategy: Fill, Strip, Vertical Remnant, Horizontal Remnant")]
                 string engine = null
         )
         {
@@ -84,7 +84,7 @@ namespace OpenNest.Mcp.Tools
             [Description("Width of the area")] double width,
             [Description("Length of the area")] double length,
             [Description("Maximum quantity to place (0 = unlimited)")] int quantity = 0,
-            [Description("Placement strategy: Default, Strip, Vertical Remnant, Horizontal Remnant")]
+            [Description("Placement strategy: Fill, Strip, Vertical Remnant, Horizontal Remnant")]
                 string engine = null
         )
         {
@@ -134,7 +134,7 @@ namespace OpenNest.Mcp.Tools
             [Description("Index of the plate")] int plateIndex,
             [Description("Name of the drawing to fill with")] string drawingName,
             [Description("Maximum quantity per remnant (0 = unlimited)")] int quantity = 0,
-            [Description("Placement strategy: Default, Strip, Vertical Remnant, Horizontal Remnant")]
+            [Description("Placement strategy: Fill, Strip, Vertical Remnant, Horizontal Remnant")]
                 string engine = null
         )
         {
@@ -197,7 +197,7 @@ namespace OpenNest.Mcp.Tools
             [Description("Index of the plate")] int plateIndex,
             [Description("Comma-separated drawing names")] string drawingNames,
             [Description("Comma-separated quantities for each drawing")] string quantities,
-            [Description("Placement strategy: Default, Strip, Vertical Remnant, Horizontal Remnant")]
+            [Description("Placement strategy: Fill, Strip, Vertical Remnant, Horizontal Remnant")]
                 string engine = null
         )
         {

OpenNest.Tests/Benchmark/NestLayoutCheckEquivalenceTests.cs

@@ -10,7 +10,7 @@ public class NestLayoutCheckEquivalenceTests
 {
     [Theory]
     [InlineData("StockLadder")]
-    [InlineData("Default")]
+    [InlineData("Fill")]
     [InlineData("Strip")]
     [InlineData("Vertical Remnant")]
     [InlineData("Horizontal Remnant")]

OpenNest.Tests/BestFit/NativeUClearanceTests.cs

@@ -38,7 +38,7 @@ public class NativeUClearanceTests
             PartSpacing = 0.25,
             EdgeSpacing = new Spacing(1, 1),
         };
-        var parts = PlateFillService.FillItem("Default", plate,
+        var parts = PlateFillService.FillItem("Fill", plate,
             new NestItem { Drawing = drawing, Quantity = quantity }, plate.WorkArea(),
             null, CancellationToken.None);
 

OpenNest.Tests/Engine/EngineOverlapTests.cs

@@ -28,7 +28,7 @@ public class EngineOverlapTests
     }
 
     [Theory]
-    [InlineData("Default")]
+    [InlineData("Fill")]
     [InlineData("Strip")]
     [InlineData("Vertical Remnant")]
     [InlineData("Horizontal Remnant")]

OpenNest.Tests/Engine/ExplicitPlacementStrategyTests.cs

@@ -26,9 +26,9 @@ public class ExplicitPlacementStrategyTests
     [InlineData(null)]
     [InlineData("")]
     [InlineData("   ")]
-    public void ResolveStrategy_UnsetMeansDefault(string strategy)
+    public void ResolveStrategy_UnsetMeansFill(string strategy)
     {
-        Assert.Equal("Default", PlateFillService.ResolveStrategy(strategy));
+        Assert.Equal("Fill", PlateFillService.ResolveStrategy(strategy));
     }
 
     [Theory]

OpenNest.WinForms.Tests/ActionSelectAreaCutOffTests.cs

@@ -63,7 +63,7 @@ public class ActionSelectAreaCutOffTests
             program.LineTo(3, 0);
             program.LineTo(0, 0);
             // ActionFillArea passes SelectedArea directly to this service.
-            var parts = PlateFillService.FillItem("Default", plate,
+            var parts = PlateFillService.FillItem("Fill", plate,
                 new NestItem { Drawing = new Drawing("square", program) }, area, null, CancellationToken.None);
             Assert.NotEmpty(parts);
             Assert.All(parts, part =>

OpenNest/Forms/EngineSelection.cs

@@ -13,7 +13,7 @@ namespace OpenNest.Forms
     /// App-scoped nesting-engine selection. The selected name addresses a whole-job
     /// INestingEngine resolved through NestingEngineRegistry at call time; single-plate
     /// interactive fill uses FillStrategy, which maps a built-in engine to its placement
-    /// strategy and falls back to Default for jobs-only engines (StockLadder, plug-ins).
+    /// strategy and falls back to Fill for jobs-only engines (StockLadder, plug-ins).
     /// </summary>
     public static class EngineSelection
     {
@@ -67,8 +67,8 @@ namespace OpenNest.Forms
                 .ToList();
 
         /// <summary>Placement strategy for single-plate fill: the selection when it names a
-        /// built-in strategy, otherwise Default.</summary>
-        public static string FillStrategy => IsFillStrategy(engineName) ? engineName : DefaultEngineName;
+        /// built-in strategy, otherwise Fill.</summary>
+        public static string FillStrategy => IsFillStrategy(engineName) ? engineName : PlateFillService.DefaultStrategy;
 
         public static bool IsFillStrategy(string name) =>
             !string.IsNullOrWhiteSpace(name)

README.md

@@ -64,7 +64,7 @@ Key options: `--size WxL`, `--autonest` (validated single-sheet whole-job nestin
 
 ```bash
 dotnet run --project OpenNest.Benchmark -- ./benchmark-jobs \
-  --sheet-sizes 48x96,60x120,72x120 --engines Default,StockLadder --csv results.csv
+  --sheet-sizes 48x96,60x120,72x120 --engines Irregular,Rectangles --csv results.csv
 ```
 
 Layouts are validated (bounds, spacing, quantity, rotation, stock match); invalid runs place nothing and pay the penalty. `--parallel` (default 3) speeds up scoring but inflates `Time(ms)` — use `--parallel 1` when comparing speed. Pass `--sheet-sizes` for an unbiased run; otherwise only each file's original sizes are offered. `--progress` logs each solve's start, the engine's `NestJobProgress` (plate evaluations throttled to one line per 2 s, every plate commit) and its finish. Custom engines drop in as DLLs implementing `INestingEngine` (public parameterless constructor) in an `Engines/` folder next to the benchmark. Built-in engines and how to change them: [nesting engines](docs/nesting-engines.md).
@@ -93,7 +93,7 @@ Engines implement `INestingEngine.Solve(NestJob)`. Desktop Auto Nest, console au
 |--------|-------------|
 | **Rectangles** | Plain and near-rectangular plates: maximal-rectangles box packing |
 | **Irregular** | Irregular profiles: no-fit-polygon frontier packing |
-| **Default** | Multi-phase: linear fill → pairs → rect best-fit → extents |
+| **Fill** | Multi-phase: linear fill → pairs → rect best-fit → extents (named Default in earlier releases) |
 | **Strip** | Iterative shrink-fill for mixed-drawing layouts |
 | **Vertical / Horizontal Remnant** | Optimizes a clean remnant drop on one edge |
 | **StockLadder** | Whole-job, stock-constrained baseline with salvage-credit ranking |

docs/geometry/pair-spacing.md

@@ -18,7 +18,7 @@ Fresh-process import/cache/materialization probes used a 24-by-24 sheet, one-inc
 | --- | --- | --- |
 | Smallest-envelope kept pair, minimum raw clearance | 0.22548054744486495 | 0.24999929486961545 |
 | `PairFiller`, 70 parts, minimum raw clearance | 0.22548054744486434 | 0.24999929486961417 |
-| `PlateFillService.FillItem("Default")`, 70 parts, minimum raw clearance | 0.2254805474448648 | 0.24999929486961447 |
+| `PlateFillService.FillItem("Fill")`, 70 parts, minimum raw clearance | 0.2254805474448648 | 0.24999929486961447 |
 
 Measurements use raw material outlines tessellated at 1e-6 chord tolerance and independent Shapely boundary distances, not the slide solver or its offset contours. The roughly 7e-7 shortfall is within tessellation error. These specific pair/grid polygons were valid; no geometry repair was applied. The corrected top pair passes the existing validator. The full grids do **not** pass it; see below.
 

docs/nesting-engines.md

@@ -14,7 +14,7 @@ in `OpenNest.Engine/NestingEngines/<Name>/`, its tests in `OpenNest.Engine.Tests
 | Rectangles | Plain and near-rectangular plates | Each part packed as the box of its material at its minimum-area rotation, using a maximal-rectangles free list; stock chosen sheet by sheet by salvage-credited look-ahead cost |
 | Irregular | Irregular profiles | No-fit-polygon frontier packing with gap filling and best-fit pairs, six whole-job strategy variants and a tail re-plan |
 | StockLadder | Caller-supplied stock ladders | Constrained-first fill with equivalent-demand area repacking |
-| Default, Strip, Vertical Remnant, Horizontal Remnant | Single-strategy fills | The fixed placement strategies behind interactive fill |
+| Fill, Strip, Vertical Remnant, Horizontal Remnant | Single-strategy fills | The fixed placement strategies behind interactive fill; Fill is the multi-phase lattice fill (linear, pairs, rectangle best-fit, remainder) |
 
 Rectangles places irregular parts validly, but only as their bounding boxes; it never nests into a
 notch or hole. Box sides account for how the layout check flattens arcs, so round-edged parts stay
@@ -44,8 +44,8 @@ with a single boundary/containment union.
 Any remaining numerical hole is filled only when its entire ring is certified to lie in forbidden
 space, preserving genuine enclosed placement pockets without changing spacing tolerances.
 
-When remaining demand exceeds two, Irregular also offers Default Fill patterns as optional
-multi-member candidates, not as solid bounding boxes or a whole-job Default fallback. It searches
+When remaining demand exceeds two, Irregular also offers Fill patterns as optional
+multi-member candidates, not as solid bounding boxes or a whole-job Fill fallback. It searches
 the empty work area and physical leftover space for up to two high-area rectangles. Occupied
 outlines are expanded by part spacing before rectangle search. Each sheet prepares blocks initially
 and after its first placement, for up to four high-demand-area types; each type has at most eight
@@ -67,7 +67,7 @@ engine, so every engine benefits. Nothing calls it yet: a part inside a cutout m
 the cutout's contour, and the sequencer does not enforce that order.
 
 `CutoutLatticeFill` (`OpenNest.Engine/Jobs/Cutouts/`) fills one closed cutout with copies of one
-part. It runs Default Fill over the cutout's bounds plus one part step on every side, then shifts
+part. It runs Fill over the cutout's bounds plus one part step on every side, then shifts
 that lattice across a grid of offsets of up to half a step each way. At each offset it keeps the
 copies whose spacing-grown outline lies inside the cutout, using the part's inner-fit region of
 the inscribed, flattened cutout, and the offset keeping the most copies wins. Every returned pose
@@ -78,16 +78,20 @@ calls for some parts, so results are not yet guaranteed identical between runs.
 
 ## Renamed engines
 
-Earlier releases shipped these as plug-ins under other names. The registry maps the old names so
-saved desktop selections, scripts and API requests keep working:
+The registry maps names used by earlier releases (the first two shipped as plug-ins) so saved
+desktop selections, scripts and API requests keep working:
 
 | Old name | Now |
 |---|---|
 | `Opus55NestingEngine` | Irregular |
 | `RectanglesNestingEngine` | Rectangles |
+| `Default` | Fill |
+
+Fill strategy calls (interactive fill, `PlateFillService`, console fill without `--autonest`, MCP fill
+tools) also accept `Default` as Fill.
 
 Gpt6Astra and Qwen38FlashNext are no longer shipped and have no alias. A saved selection of either
-falls back to Default with the usual status-bar warning.
+falls back to the default engine with the usual status-bar warning.
 
 ## Changing an engine
 

docs/performance/fill-verification.md

@@ -18,7 +18,7 @@ Irregular's private block proposals opt into quantity-limited Row/Column stripe
 perpendicular copies stop after reaching the requested count. The final fill still
 trims its winner to the exact quantity. Existing overlap fallbacks and block spacing
 certification remain active; fallback tiling can exceed the soft limit. Nonpositive
-limits remain uncapped. Ordinary Default fills and the zero-quantity cutout lattice
+limits remain uncapped. Ordinary Fill-strategy fills and the zero-quantity cutout lattice
 keep their full-area behavior.
 
 This can change which private block candidate wins; it is not a promise of identical

scripts/ReleaseSmoke/Program.cs

@@ -20,7 +20,7 @@ try
     var create = registry.GetMethod("Create")!;
 
     // Every built-in engine the desktop offers must instantiate from the packaged assembly.
-    string[] expected = ["Rectangles", "Irregular", "StockLadder", "Default", "Strip", "Vertical Remnant", "Horizontal Remnant"];
+    string[] expected = ["Rectangles", "Irregular", "StockLadder", "Fill", "Strip", "Vertical Remnant", "Horizontal Remnant"];
     foreach (var name in expected)
     {
         var engine = create.Invoke(null, [name])!;