diff --git a/OpenNest.Engine.Tests/Jobs/PlateNesterParityTests.cs b/OpenNest.Engine.Tests/Jobs/PlateNesterParityTests.cs
new file mode 100644
index 0000000..aa6058b
--- /dev/null
+++ b/OpenNest.Engine.Tests/Jobs/PlateNesterParityTests.cs
@@ -0,0 +1,257 @@
+using OpenNest.CNC;
+using OpenNest.Geometry;
+using Xunit;
+
+namespace OpenNest.Engine.Tests.Jobs;
+
+/// <summary>
+/// Parity between the legacy adapter and the migrated built-in plate nesters (Default/Strip) on
+/// generated geometry. The runner's placement validator enforces geometric safety on every committed
+/// candidate, so these tests assert fulfillment, status, and — for the deterministic Default/rectangle
+/// case — identical layouts.
+/// </summary>
+public class PlateNesterParityTests
+{
+    private const double Tolerance = 1e-6;
+
+    private static readonly Size PlateSize = new(30, 50);
+    private static readonly Spacing Edge = new(1, 1, 1, 1);
+
+    private static NestJob Job(IReadOnlyList<NestJobPart> parts, int? stockQuantity = 3,
+        string strategy = "Default")
+    {
+        var stock = new NestPlateStock("stock", PlateSize, stockQuantity, 1, Edge);
+        return new NestJob(parts, new[] { stock }, new NestJobOptions(strategy));
+    }
+
+    private static NestJobResult Solve(IPlateNester nester, NestJob job) =>
+        new NestJobRunner(_ => nester).Solve(job);
+
+    private static Dictionary<string, PartFulfillment> ByPart(NestJobResult result) =>
+        result.Fulfillment.ToDictionary(f => f.PartId, StringComparer.Ordinal);
+
+    private static void AssertLayoutsIdentical(NestJobResult left, NestJobResult right)
+    {
+        Assert.Equal(left.Plates.Count, right.Plates.Count);
+        for (var i = 0; i < left.Plates.Count; i++)
+        {
+            var lPlates = left.Plates[i].Placements;
+            var rPlates = right.Plates[i].Placements;
+            Assert.Equal(lPlates.Count, rPlates.Count);
+            var lSorted = lPlates.OrderBy(p => p.PartId).ThenBy(p => p.X).ThenBy(p => p.Y).ToList();
+            var rSorted = rPlates.OrderBy(p => p.PartId).ThenBy(p => p.X).ThenBy(p => p.Y).ToList();
+            for (var j = 0; j < lSorted.Count; j++)
+            {
+                Assert.Equal(lSorted[j].PartId, rSorted[j].PartId);
+                Assert.Equal(lSorted[j].X, rSorted[j].X, 6);
+                Assert.Equal(lSorted[j].Y, rSorted[j].Y, 6);
+                Assert.True(AnglesEqual(lSorted[j].Rotation, rSorted[j].Rotation),
+                    $"rotation differs: {lSorted[j].Rotation} vs {rSorted[j].Rotation}");
+            }
+        }
+    }
+
+    private static bool AnglesEqual(double left, double right)
+    {
+        var delta = (left - right) % (System.Math.PI * 2);
+        return System.Math.Abs(delta) <= Tolerance ||
+            System.Math.Abs(System.Math.Abs(delta) - System.Math.PI * 2) <= Tolerance;
+    }
+
+    [Fact]
+    public void DefaultParity_Rectangles_SameFulfillmentAndLayout()
+    {
+        var parts = new[]
+        {
+            new NestJobPart("a", PartGeometrySnapshot.FromProgram(TestDrawingFactory.Rectangle(6, 4)), 4),
+            new NestJobPart("b", PartGeometrySnapshot.FromProgram(TestDrawingFactory.Rectangle(4, 3)), 3)
+        };
+
+        var legacy = Solve(new LegacyPlateNesterAdapter(plate => new DefaultNestEngine(plate)), Job(parts));
+        var migrated = Solve(new DefaultPlateNester(), Job(parts));
+
+        Assert.Equal(legacy.Status, migrated.Status);
+        Assert.Equal(NestJobStatus.Complete, migrated.Status);
+        Assert.Equal(ByPart(legacy), ByPart(migrated));
+        foreach (var usage in legacy.StockUsage)
+            Assert.Equal(usage.Used, migrated.StockUsage.First(u => u.StockId == usage.StockId).Used);
+        // Automatic-rotation rectangles on a single stock size are deterministic: identical layouts.
+        AssertLayoutsIdentical(legacy, migrated);
+    }
+
+    [Fact]
+    public void StripParity_Rectangles_SameFulfillmentAndTotalCount()
+    {
+        var parts = new[]
+        {
+            new NestJobPart("a", PartGeometrySnapshot.FromProgram(TestDrawingFactory.Rectangle(6, 4)), 4),
+            new NestJobPart("b", PartGeometrySnapshot.FromProgram(TestDrawingFactory.Rectangle(4, 3)), 3)
+        };
+
+        var legacy = Solve(new LegacyPlateNesterAdapter(plate => new StripNestEngine(plate)),
+            Job(parts, strategy: "Strip"));
+        var migrated = Solve(new StripPlateNester(), Job(parts, strategy: "Strip"));
+
+        Assert.Equal(legacy.Status, migrated.Status);
+        Assert.Equal(NestJobStatus.Complete, migrated.Status);
+        Assert.Equal(ByPart(legacy), ByPart(migrated));
+        Assert.Equal(legacy.Plates.SelectMany(p => p.Placements).Count(),
+            migrated.Plates.SelectMany(p => p.Placements).Count());
+        // Shrink-fill ordering can differ between engine instances; do not assert identical coordinates.
+    }
+
+    [Fact]
+    public void MigratedBuiltins_AreResolvedByProductionFactory()
+    {
+        Assert.IsType<DefaultPlateNester>(PlateNesterFactory.Create("Default"));
+        Assert.IsType<StripPlateNester>(PlateNesterFactory.Create("Strip"));
+        Assert.IsType<LegacyPlateNesterAdapter>(PlateNesterFactory.Create("Vertical Remnant"));
+        Assert.IsType<LegacyPlateNesterAdapter>(PlateNesterFactory.Create("Horizontal Remnant"));
+    }
+
+    [Fact]
+    public void AsymmetricPart_ValidAndFulfilled()
+    {
+        // L-shape: 6x4 outer with a corner notch removed (single closed contour, asymmetric).
+        var lshape = new Program();
+        lshape.MoveTo(0, 0);
+        lshape.LineTo(6, 0);
+        lshape.LineTo(6, 4);
+        lshape.LineTo(3, 4);
+        lshape.LineTo(3, 2);
+        lshape.LineTo(0, 2);
+        lshape.LineTo(0, 0);
+
+        var parts = new[]
+        {
+            new NestJobPart("l", PartGeometrySnapshot.FromProgram(lshape), 3),
+            new NestJobPart("sq", PartGeometrySnapshot.FromProgram(TestDrawingFactory.Rectangle(4, 3)), 2)
+        };
+        var result = Solve(new DefaultPlateNester(), Job(parts));
+
+        Assert.Equal(NestJobStatus.Complete, result.Status);
+        Assert.Equal(3, ByPart(result)["l"].Placed);
+        Assert.Equal(2, ByPart(result)["sq"].Placed);
+        Assert.Equal(5, result.Plates.SelectMany(p => p.Placements).Count());
+    }
+
+    [Fact]
+    public void HoleAndArcParts_ValidAndFulfilled()
+    {
+        // 6x6 rectangle with a 2x2 inner hole (rapid contour), plus a D-shape with a semicircular arc.
+        var holed = new Program();
+        holed.MoveTo(0, 0);
+        holed.LineTo(6, 0);
+        holed.LineTo(6, 6);
+        holed.LineTo(0, 6);
+        holed.LineTo(0, 0);
+        holed.MoveTo(2, 2);
+        holed.LineTo(4, 2);
+        holed.LineTo(4, 4);
+        holed.LineTo(2, 4);
+        holed.LineTo(2, 2);
+
+        var arc = new Program();
+        arc.MoveTo(0, 0);
+        arc.LineTo(3, 0);
+        arc.ArcTo(3, 5, 3, 2.5, RotationType.CCW);
+        arc.LineTo(0, 5);
+        arc.LineTo(0, 0);
+
+        var parts = new[]
+        {
+            new NestJobPart("holed", PartGeometrySnapshot.FromProgram(holed), 2),
+            new NestJobPart("arc", PartGeometrySnapshot.FromProgram(arc), 2)
+        };
+        var result = Solve(new DefaultPlateNester(), Job(parts));
+
+        Assert.Equal(NestJobStatus.Complete, result.Status);
+        Assert.Equal(2, ByPart(result)["holed"].Placed);
+        Assert.Equal(2, ByPart(result)["arc"].Placed);
+    }
+
+    [Fact]
+    public void FixedRotation_Respected()
+    {
+        var part = new NestJobPart("fixed", PartGeometrySnapshot.FromProgram(TestDrawingFactory.Rectangle(6, 4)),
+            2, rotation: RotationPolicy.Fixed(0));
+        var result = Solve(new DefaultPlateNester(), Job(new[] { part }));
+
+        Assert.Equal(NestJobStatus.Complete, result.Status);
+        var placements = result.Plates.SelectMany(p => p.Placements).ToList();
+        Assert.Equal(2, placements.Count);
+        foreach (var placement in placements)
+            Assert.True(AnglesEqual(placement.Rotation, 0), $"fixed rotation violated: {placement.Rotation}");
+    }
+
+    [Fact]
+    public void RepeatedNames_KeepIndependentIdentity()
+    {
+        // Two distinct requirements sharing identical geometry (and, via the mapper, name) but different IDs.
+        var program = TestDrawingFactory.Rectangle(6, 4);
+        var parts = new[]
+        {
+            new NestJobPart("first", PartGeometrySnapshot.FromProgram(program), 2),
+            new NestJobPart("second", PartGeometrySnapshot.FromProgram(program), 1)
+        };
+        var result = Solve(new DefaultPlateNester(), Job(parts));
+
+        Assert.Equal(NestJobStatus.Complete, result.Status);
+        Assert.Equal(2, ByPart(result)["first"].Placed);
+        Assert.Equal(1, ByPart(result)["second"].Placed);
+        var ids = result.Plates.SelectMany(p => p.Placements).Select(p => p.PartId);
+        Assert.Equal(2, ids.Count(id => id == "first"));
+        Assert.Equal(1, ids.Count(id => id == "second"));
+    }
+
+    [Fact]
+    public void OffsetGeometry_ValidAndFulfilled()
+    {
+        // Part contour starting at a nonzero origin (offset geometry).
+        var program = new Program();
+        program.MoveTo(12, 7);
+        program.LineTo(18, 7);
+        program.LineTo(18, 11);
+        program.LineTo(12, 11);
+        program.LineTo(12, 7);
+
+        var part = new NestJobPart("offset", PartGeometrySnapshot.FromProgram(program), 2);
+        var result = Solve(new DefaultPlateNester(), Job(new[] { part }));
+
+        Assert.Equal(NestJobStatus.Complete, result.Status);
+        Assert.Equal(2, ByPart(result)["offset"].Placed);
+        // The runner's validator guarantees containment and non-overlap for every committed placement.
+    }
+
+    [Fact]
+    public void RunScopedCache_DrawingReusedAcrossTrials()
+    {
+        // 14x9 parts on 30x20: one sheet holds fewer than five, so the runner runs multiple candidate
+        // trials through the same nester instance. The run-scoped drawing cache must keep producing
+        // valid, correctly-attributed placements across trials.
+        var part = new NestJobPart("p", PartGeometrySnapshot.FromProgram(TestDrawingFactory.Rectangle(14, 9)), 5);
+        var stock = new NestPlateStock("stock", new Size(30, 20), 3);
+        var nester = new DefaultPlateNester();
+        var result = new NestJobRunner(_ => nester).Solve(new NestJob(new[] { part }, new[] { stock }));
+
+        Assert.Equal(NestJobStatus.Complete, result.Status);
+        Assert.Equal(5, result.Fulfillment.Single(f => f.PartId == "p").Placed);
+        Assert.Equal(2, result.Plates.Count);
+        var usage = result.StockUsage.Single();
+        Assert.Equal(2, usage.Used);
+        Assert.Equal(1, usage.Remaining);
+    }
+
+    [Fact]
+    public void LegacyRemnantStrategies_StillResolveThroughAdapter()
+    {
+        // Remnant strategies must keep working through the legacy adapter after the factory change.
+        var part = new NestJobPart("p", PartGeometrySnapshot.FromProgram(TestDrawingFactory.Rectangle(6, 4)), 2);
+        foreach (var strategy in new[] { "Vertical Remnant", "Horizontal Remnant" })
+        {
+            var result = Solve(PlateNesterFactory.Create(strategy), Job(new[] { part }, strategy: strategy));
+            Assert.Equal(NestJobStatus.Complete, result.Status);
+            Assert.Equal(2, result.Fulfillment.Single(f => f.PartId == "p").Placed);
+        }
+    }
+}
diff --git a/OpenNest.Engine/Jobs/CandidateProgressBridge.cs b/OpenNest.Engine/Jobs/CandidateProgressBridge.cs
new file mode 100644
index 0000000..9dd2c8d
--- /dev/null
+++ b/OpenNest.Engine/Jobs/CandidateProgressBridge.cs
@@ -0,0 +1,26 @@
+using System;
+
+namespace OpenNest;
+
+/// <summary>
+/// Bridges legacy <see cref="IProgress{NestProgress}"/> reporting into job progress while a candidate
+/// trial is being evaluated. Used by both the legacy adapter and the migrated built-in nesters so the
+/// stage/context mapping has one implementation.
+/// </summary>
+internal static class CandidateProgressBridge
+{
+    internal static IProgress<NestProgress> Create(IProgress<NestJobProgress> progress, string stockId)
+    {
+        if (progress == null) return null;
+        return new LegacyToJob(progress, stockId);
+    }
+
+    private sealed class LegacyToJob(IProgress<NestJobProgress> progress, string stockId) : IProgress<NestProgress>
+    {
+        public void Report(NestProgress value)
+        {
+            ArgumentNullException.ThrowIfNull(value);
+            progress.Report(new NestJobProgress(NestJobStage.EvaluatingCandidate, stockId, -1, 0, 0, value));
+        }
+    }
+}
diff --git a/OpenNest.Engine/Jobs/Placement/DefaultPlateNester.cs b/OpenNest.Engine/Jobs/Placement/DefaultPlateNester.cs
new file mode 100644
index 0000000..e184090
--- /dev/null
+++ b/OpenNest.Engine/Jobs/Placement/DefaultPlateNester.cs
@@ -0,0 +1,82 @@
+using System;
+using System.Collections.Generic;
+using System.Threading;
+
+namespace OpenNest;
+
+/// <summary>
+/// Migrated built-in placement strategy for the whole-job runner. Reuses <see cref="DefaultNestEngine"/>
+/// fill/pack geometry but owns its own run-scoped bookkeeping: remaining demand is read from the
+/// request and placement counts are derived from returned placements, so the engine's private
+/// <see cref="NestItem.Quantity"/> mutations never feed back into job accounting.
+/// </summary>
+/// <remarks>
+/// A private <see cref="Drawing"/> per requirement is created once per solve and reused across every
+/// candidate trial (the runner reuses one <see cref="IPlateNester"/> instance per job). This is safe
+/// because the engines mutate <see cref="NestItem.Quantity"/> (per-trial) and canonical-frame copies,
+/// never the shared <see cref="Drawing"/> or its <c>Quantity</c>. Identity is by Drawing reference,
+/// never by name. Each trial still gets a fresh private <see cref="Plate"/>.
+/// </remarks>
+public sealed class DefaultPlateNester : IPlateNester
+{
+    private readonly Func<Plate, DefaultNestEngine> engineFactory;
+    private readonly Dictionary<string, Drawing> drawingsById = new(StringComparer.Ordinal);
+    private readonly Dictionary<Drawing, string> idByDrawing = new(ReferenceEqualityComparer.Instance);
+
+    public DefaultPlateNester() : this(static plate => new DefaultNestEngine(plate))
+    {
+    }
+
+    /// <param name="engineFactory">Injectable for tests; defaults to <see cref="DefaultNestEngine"/>.</param>
+    public DefaultPlateNester(Func<Plate, DefaultNestEngine> engineFactory)
+    {
+        this.engineFactory = engineFactory ?? throw new ArgumentNullException(nameof(engineFactory));
+    }
+
+    public PlateCandidate Place(PlatePlacementRequest request, IProgress<NestJobProgress> progress = null,
+        CancellationToken token = default)
+    {
+        ArgumentNullException.ThrowIfNull(request);
+        token.ThrowIfCancellationRequested();
+
+        var plate = DrawingJobMapper.CreatePlate(request.Stock);
+        var items = new List<NestItem>(request.Parts.Count);
+        foreach (var requirement in request.Parts)
+        {
+            if (!drawingsById.TryGetValue(requirement.Id, out var drawing))
+            {
+                drawing = DrawingJobMapper.CreateDrawing(requirement);
+                drawingsById.Add(requirement.Id, drawing);
+                idByDrawing.Add(drawing, requirement.Id);
+            }
+
+            // Quantity is the request's remaining demand; the engine may mutate this per-trial item,
+            // and that mutation is deliberately discarded — placement counts come from the result.
+            items.Add(new NestItem
+            {
+                Drawing = drawing,
+                Quantity = requirement.Quantity,
+                Priority = requirement.Priority,
+                StepAngle = DrawingJobMapper.LegacyStep(requirement.Rotation),
+                RotationStart = requirement.Rotation.Start,
+                RotationEnd = requirement.Rotation.End
+            });
+        }
+
+        var engine = engineFactory(plate) ?? throw new InvalidOperationException("Engine factory returned null.");
+        var legacyProgress = CandidateProgressBridge.Create(progress, request.Stock.Id);
+        var parts = engine.Nest(items, legacyProgress, token);
+        token.ThrowIfCancellationRequested();
+        if (parts == null) throw new InvalidOperationException("Engine returned null placements.");
+
+        var placements = new List<NestJobPlacement>(parts.Count);
+        foreach (var part in parts)
+        {
+            if (part?.BaseDrawing == null || !idByDrawing.TryGetValue(part.BaseDrawing, out var id))
+                throw new InvalidOperationException("Placement does not reference a known requirement drawing.");
+            placements.Add(new NestJobPlacement(id, 0, part.Location.X, part.Location.Y, part.Rotation));
+        }
+
+        return new PlateCandidate(placements);
+    }
+}
diff --git a/OpenNest.Engine/Jobs/Placement/StripPlateNester.cs b/OpenNest.Engine/Jobs/Placement/StripPlateNester.cs
new file mode 100644
index 0000000..8c6060c
--- /dev/null
+++ b/OpenNest.Engine/Jobs/Placement/StripPlateNester.cs
@@ -0,0 +1,77 @@
+using System;
+using System.Collections.Generic;
+using System.Threading;
+
+namespace OpenNest;
+
+/// <summary>
+/// Migrated built-in placement strategy for the whole-job runner. Reuses <see cref="StripNestEngine"/>
+/// iterative shrink-fill/pack geometry with the same run-scoped bookkeeping as <see cref="DefaultPlateNester"/>:
+/// remaining demand is read from the request and placement counts are derived from returned placements.
+/// </summary>
+/// <remarks>
+/// A private <see cref="Drawing"/> per requirement is created once per solve and reused across trials
+/// (safe: the engine mutates per-trial <see cref="NestItem.Quantity"/> and canonical copies, never the
+/// shared Drawing). Identity is by Drawing reference. Each trial gets a fresh private <see cref="Plate"/>.
+/// </remarks>
+public sealed class StripPlateNester : IPlateNester
+{
+    private readonly Func<Plate, StripNestEngine> engineFactory;
+    private readonly Dictionary<string, Drawing> drawingsById = new(StringComparer.Ordinal);
+    private readonly Dictionary<Drawing, string> idByDrawing = new(ReferenceEqualityComparer.Instance);
+
+    public StripPlateNester() : this(static plate => new StripNestEngine(plate))
+    {
+    }
+
+    /// <param name="engineFactory">Injectable for tests; defaults to <see cref="StripNestEngine"/>.</param>
+    public StripPlateNester(Func<Plate, StripNestEngine> engineFactory)
+    {
+        this.engineFactory = engineFactory ?? throw new ArgumentNullException(nameof(engineFactory));
+    }
+
+    public PlateCandidate Place(PlatePlacementRequest request, IProgress<NestJobProgress> progress = null,
+        CancellationToken token = default)
+    {
+        ArgumentNullException.ThrowIfNull(request);
+        token.ThrowIfCancellationRequested();
+
+        var plate = DrawingJobMapper.CreatePlate(request.Stock);
+        var items = new List<NestItem>(request.Parts.Count);
+        foreach (var requirement in request.Parts)
+        {
+            if (!drawingsById.TryGetValue(requirement.Id, out var drawing))
+            {
+                drawing = DrawingJobMapper.CreateDrawing(requirement);
+                drawingsById.Add(requirement.Id, drawing);
+                idByDrawing.Add(drawing, requirement.Id);
+            }
+
+            items.Add(new NestItem
+            {
+                Drawing = drawing,
+                Quantity = requirement.Quantity,
+                Priority = requirement.Priority,
+                StepAngle = DrawingJobMapper.LegacyStep(requirement.Rotation),
+                RotationStart = requirement.Rotation.Start,
+                RotationEnd = requirement.Rotation.End
+            });
+        }
+
+        var engine = engineFactory(plate) ?? throw new InvalidOperationException("Engine factory returned null.");
+        var legacyProgress = CandidateProgressBridge.Create(progress, request.Stock.Id);
+        var parts = engine.Nest(items, legacyProgress, token);
+        token.ThrowIfCancellationRequested();
+        if (parts == null) throw new InvalidOperationException("Engine returned null placements.");
+
+        var placements = new List<NestJobPlacement>(parts.Count);
+        foreach (var part in parts)
+        {
+            if (part?.BaseDrawing == null || !idByDrawing.TryGetValue(part.BaseDrawing, out var id))
+                throw new InvalidOperationException("Placement does not reference a known requirement drawing.");
+            placements.Add(new NestJobPlacement(id, 0, part.Location.X, part.Location.Y, part.Rotation));
+        }
+
+        return new PlateCandidate(placements);
+    }
+}
diff --git a/OpenNest.Engine/Jobs/PlateNesterFactory.cs b/OpenNest.Engine/Jobs/PlateNesterFactory.cs
index c60b1be..495bfee 100644
--- a/OpenNest.Engine/Jobs/PlateNesterFactory.cs
+++ b/OpenNest.Engine/Jobs/PlateNesterFactory.cs
@@ -2,9 +2,10 @@ using System;
 namespace OpenNest;
 
 /// <summary>
-/// Instance-scoped strategy resolution for the whole-job runner. The built-in strategies map
-/// to private engine factories; the process-global NestEngineRegistry (including plugin
-/// registrations and ActiveEngineName) is neither read nor modified. Unknown keys reject.
+/// Instance-scoped strategy resolution for the whole-job runner. Default and Strip resolve to the
+/// migrated built-in plate nesters; the remnant strategies still use the legacy adapter during
+/// rollout. The process-global NestEngineRegistry (including plugin registrations and
+/// ActiveEngineName) is neither read nor modified. Unknown keys reject.
 /// </summary>
 public static class PlateNesterFactory
 {
@@ -13,8 +14,8 @@ public static class PlateNesterFactory
         ArgumentNullException.ThrowIfNull(strategy);
         return strategy switch
         {
-            "Default" => new LegacyPlateNesterAdapter(plate => new DefaultNestEngine(plate)),
-            "Strip" => new LegacyPlateNesterAdapter(plate => new StripNestEngine(plate)),
+            "Default" => new DefaultPlateNester(),
+            "Strip" => new StripPlateNester(),
             "Vertical Remnant" => new LegacyPlateNesterAdapter(plate => new VerticalRemnantEngine(plate)),
             "Horizontal Remnant" => new LegacyPlateNesterAdapter(plate => new HorizontalRemnantEngine(plate)),
             _ => throw new NotSupportedException($"Unknown placement strategy: {strategy}.")