diff --git a/OpenNest.Engine.Tests/Jobs/NestPipelineCommitTests.cs b/OpenNest.Engine.Tests/Jobs/NestPipelineCommitTests.cs
new file mode 100644
index 0000000..2cbbd5f
--- /dev/null
+++ b/OpenNest.Engine.Tests/Jobs/NestPipelineCommitTests.cs
@@ -0,0 +1,90 @@
+using OpenNest.Engine.Jobs;
+using OpenNest.Geometry;
+
+namespace OpenNest.Engine.Tests.Jobs;
+
+public class NestPipelineCommitTests
+{
+    private sealed class StubEngine(bool overlap) : INestingEngine
+    {
+        public NestJobResult Solve(NestJob job, IProgress<NestJobProgress>? progress = null,
+            CancellationToken token = default) => new(
+                NestJobStatus.Complete, NestJobStopReason.Completed,
+                new[] { new NestJobPlateResult(0, job.Plates[0], new[]
+                {
+                    new NestJobPlacement(job.Parts[0].Id, 0, 2, 2, 0),
+                    new NestJobPlacement(job.Parts[0].Id, 1, overlap ? 2 : 20, 2, 0),
+                }) },
+                new[] { new PartFulfillment(job.Parts[0].Id, 2, 2, 0) },
+                new[] { new StockUsage(job.Plates[0].Id, 1, null) });
+    }
+
+    private static NestPipelineResult Result(Drawing drawing, bool overlap = false) =>
+        NestPipeline.Run(new StubEngine(overlap), "stub", new NestPipelineRequest("stub",
+            new[] { new NestItem { Drawing = drawing, Quantity = 2 } },
+            new[] { new NestPlateStock("sheet", new Size(48, 96), null, 0.25, new Spacing(1, 1), 1) }));
+
+    [Fact]
+    public void AppliesValidatedSettingsToEmptyPlateAndNeverFillsOccupiedPlate()
+    {
+        var drawing = new Drawing("part", TestDrawingFactory.Rectangle());
+        var nest = new Nest();
+        nest.Drawings.Add(drawing);
+        var occupied = nest.CreatePlate();
+        occupied.Parts.Add(new Part(drawing));
+        var empty = nest.CreatePlate();
+        empty.Quantity = 7;
+        empty.Quadrant = 3;
+        empty.Size = new Size(4, 8);
+        empty.EdgeSpacing = new Spacing(0, 0);
+        using var manager = new PlateManager(nest);
+        var result = Result(drawing);
+        Assert.True(result.IsValid, string.Join("; ", result.Violations));
+
+        var applied = NestPipelineCommit.ApplyToEmptyPlates(result, manager);
+
+        Assert.Same(empty, Assert.Single(applied));
+        Assert.Single(occupied.Parts);
+        Assert.Equal(2, empty.Parts.Count);
+        Assert.Equal(1, empty.Quantity);
+        Assert.Equal(1, empty.Quadrant);
+        Assert.Equal(result.Job.Plates[0].Size, empty.Size);
+        Assert.Equal(result.Job.Plates[0].EdgeSpacing, empty.EdgeSpacing);
+        Assert.Equal(0.25, empty.PartSpacing);
+        Assert.All(empty.Parts, p => Assert.Same(drawing, p.BaseDrawing));
+        Assert.Equal(3, drawing.Quantity.Nested);
+    }
+
+    [Fact]
+    public void InvalidResultRequiresExplicitConsentAndDiscardDoesNotMutateNest()
+    {
+        var drawing = new Drawing("part", TestDrawingFactory.Rectangle());
+        var nest = new Nest();
+        nest.Drawings.Add(drawing);
+        var empty = nest.CreatePlate();
+        using var manager = new PlateManager(nest);
+        var result = Result(drawing, overlap: true);
+        Assert.False(result.IsValid);
+
+        Assert.Throws<InvalidOperationException>(() => NestPipelineCommit.ApplyToEmptyPlates(result, manager));
+        Assert.Same(empty, Assert.Single(nest.Plates));
+        Assert.Empty(empty.Parts);
+        Assert.Equal(0, drawing.Quantity.Nested);
+
+        var applied = NestPipelineCommit.ApplyToEmptyPlates(result, manager, allowInvalid: true);
+        Assert.Equal(2, Assert.Single(applied).Parts.Count);
+    }
+
+    [Fact]
+    public void CancelledCommitDoesNotCreateAnyPlate()
+    {
+        var drawing = new Drawing("part", TestDrawingFactory.Rectangle());
+        var nest = new Nest();
+        using var manager = new PlateManager(nest);
+        using var cts = new CancellationTokenSource();
+        cts.Cancel();
+        Assert.ThrowsAny<OperationCanceledException>(() =>
+            NestPipelineCommit.ApplyToEmptyPlates(Result(drawing), manager, token: cts.Token));
+        Assert.Empty(nest.Plates);
+    }
+}
diff --git a/OpenNest.Engine/Jobs/NestPipelineCommit.cs b/OpenNest.Engine/Jobs/NestPipelineCommit.cs
new file mode 100644
index 0000000..cd59bb3
--- /dev/null
+++ b/OpenNest.Engine/Jobs/NestPipelineCommit.cs
@@ -0,0 +1,50 @@
+using System;
+using System.Collections.Generic;
+using System.Threading;
+
+namespace OpenNest.Engine.Jobs;
+
+/// <summary>Applies an explicitly accepted whole-job proposal to empty physical sheets only.
+/// Caller must keep the nest and its drawings stable from request construction through commit.</summary>
+public static class NestPipelineCommit
+{
+    public static IReadOnlyList<Plate> ApplyToEmptyPlates(
+        NestPipelineResult result,
+        PlateManager manager,
+        bool allowInvalid = false,
+        CancellationToken token = default
+    )
+    {
+        ArgumentNullException.ThrowIfNull(result);
+        ArgumentNullException.ThrowIfNull(manager);
+        token.ThrowIfCancellationRequested();
+        if (!result.CanKeep || (!result.IsValid && !allowInvalid))
+            throw new InvalidOperationException("The nesting result cannot be committed without a keepable layout and explicit consent to its violations.");
+
+        var applied = new List<Plate>();
+        // Commit is synchronous on the caller's owning thread. Cancellation is checked
+        // before mutation, not partway through attachment (which would leave half a job).
+        manager.BeginBatch();
+        try
+        {
+            foreach (var proposed in result.Plates)
+            {
+                if (proposed.Parts.Count == 0)
+                    continue;
+                var plate = manager.GetOrCreateEmpty();
+                plate.Size = proposed.Stock.Size;
+                plate.PartSpacing = proposed.Stock.PartSpacing;
+                plate.EdgeSpacing = proposed.Stock.EdgeSpacing;
+                plate.Quadrant = proposed.Stock.Quadrant;
+                plate.Quantity = 1;
+                plate.Parts.AddRange(proposed.Parts);
+                applied.Add(plate);
+            }
+        }
+        finally
+        {
+            manager.EndBatch();
+        }
+        return applied.AsReadOnly();
+    }
+}
diff --git a/OpenNest.WinForms.Tests/Forms/NestValidationFormTests.cs b/OpenNest.WinForms.Tests/Forms/NestValidationFormTests.cs
new file mode 100644
index 0000000..28556bc
--- /dev/null
+++ b/OpenNest.WinForms.Tests/Forms/NestValidationFormTests.cs
@@ -0,0 +1,75 @@
+using System.Runtime.ExceptionServices;
+using System.Windows.Forms;
+using OpenNest.Forms;
+
+namespace OpenNest.WinForms.Tests.Forms;
+
+public class NestValidationFormTests
+{
+    [Theory]
+    [InlineData(true)]
+    [InlineData(false)]
+    public void DiscardIsDefaultAndMalformedOutputCannotBeKept(bool canKeep)
+    {
+        RunSta(() =>
+        {
+            using var form = new NestValidationForm(new[] { "part A and part B violate spacing" }, canKeep);
+            var buttons = form.Controls.OfType<FlowLayoutPanel>().Single().Controls.OfType<Button>().ToArray();
+            var discard = Assert.Single(buttons, b => b.Text == "Discard");
+            var keep = Assert.Single(buttons, b => b.Text == "Keep anyway");
+            Assert.Same(discard, form.AcceptButton);
+            Assert.Same(discard, form.CancelButton);
+            Assert.Equal(canKeep, keep.Enabled);
+            Assert.Contains("violate spacing", form.Controls.OfType<TextBox>().Single().Text);
+        });
+    }
+
+    private sealed class TestProgress(CancellationTokenSource cts) : NestProgressForm(cts)
+    {
+        public FormClosingEventArgs RequestClose()
+        {
+            var args = new FormClosingEventArgs(CloseReason.UserClosing, false);
+            OnFormClosing(args);
+            return args;
+        }
+    }
+
+    [Fact]
+    public void ClosingWholeJobProgressWaitsForWorkerAndRequestsCancellation()
+    {
+        RunSta(() =>
+        {
+            using var cts = new CancellationTokenSource();
+            using var form = new TestProgress(cts) { HoldOpenUntilCompleted = true };
+            Assert.True(form.Controls.Find("stopButton", true).Single().Enabled);
+            Assert.True(form.RequestClose().Cancel);
+            Assert.True(cts.IsCancellationRequested);
+            form.ShowCompleted();
+            Assert.False(form.RequestClose().Cancel);
+        });
+    }
+
+    [Fact]
+    public void CompletionClosesWithoutCancellingSuccessfulJob()
+    {
+        RunSta(() =>
+        {
+            using var cts = new CancellationTokenSource();
+            using var form = new TestProgress(cts) { HoldOpenUntilCompleted = true };
+            form.ShowCompleted();
+            Assert.False(form.RequestClose().Cancel);
+            Assert.False(cts.IsCancellationRequested);
+        });
+    }
+
+    private static void RunSta(Action action)
+    {
+        Exception? error = null;
+        var thread = new Thread(() => { try { action(); } catch (Exception ex) { error = ex; } });
+        thread.SetApartmentState(ApartmentState.STA);
+        thread.Start();
+        Assert.True(thread.Join(TimeSpan.FromSeconds(15)));
+        if (error != null)
+            ExceptionDispatchInfo.Capture(error).Throw();
+    }
+}
diff --git a/OpenNest/Forms/AutoNestForm.Designer.cs b/OpenNest/Forms/AutoNestForm.Designer.cs
index 8cd1d9b..f6b6c98 100644
--- a/OpenNest/Forms/AutoNestForm.Designer.cs
+++ b/OpenNest/Forms/AutoNestForm.Designer.cs
@@ -24,11 +24,6 @@ namespace OpenNest.Forms
             this.summaryLabel = new System.Windows.Forms.Label();
             this.engineLabel = new System.Windows.Forms.Label();
             this.engineComboBox = new System.Windows.Forms.ComboBox();
-            this.createNewPlatesAsNeededBox = new System.Windows.Forms.CheckBox();
-            this.partFirstGroup = new System.Windows.Forms.GroupBox();
-            this.partFirstCheckBox = new System.Windows.Forms.CheckBox();
-            this.sortOrderLabel = new System.Windows.Forms.Label();
-            this.sortOrderComboBox = new System.Windows.Forms.ComboBox();
             this.minRemnantLabel = new System.Windows.Forms.Label();
             this.minRemnantBox = new System.Windows.Forms.TextBox();
             this.plateOptimizerGroup = new System.Windows.Forms.GroupBox();
@@ -45,7 +40,6 @@ namespace OpenNest.Forms
             this.platesTab.SuspendLayout();
             ((System.ComponentModel.ISupportInitialize)(this.partsGrid)).BeginInit();
             ((System.ComponentModel.ISupportInitialize)(this.plateGrid)).BeginInit();
-            this.partFirstGroup.SuspendLayout();
             this.plateOptimizerGroup.SuspendLayout();
             this.buttonPanel.SuspendLayout();
             this.SuspendLayout();
@@ -77,8 +71,6 @@ namespace OpenNest.Forms
             //
             this.platesTab.Controls.Add(this.engineLabel);
             this.platesTab.Controls.Add(this.engineComboBox);
-            this.platesTab.Controls.Add(this.createNewPlatesAsNeededBox);
-            this.platesTab.Controls.Add(this.partFirstGroup);
             this.platesTab.Controls.Add(this.plateOptimizerGroup);
             this.platesTab.Location = new System.Drawing.Point(4, 25);
             this.platesTab.Name = "platesTab";
@@ -129,70 +121,18 @@ namespace OpenNest.Forms
             this.engineComboBox.Size = new System.Drawing.Size(200, 24);
             this.engineComboBox.TabIndex = 1;
             //
-            // createNewPlatesAsNeededBox
-            //
-            this.createNewPlatesAsNeededBox.AutoSize = true;
-            this.createNewPlatesAsNeededBox.Location = new System.Drawing.Point(10, 44);
-            this.createNewPlatesAsNeededBox.Name = "createNewPlatesAsNeededBox";
-            this.createNewPlatesAsNeededBox.Size = new System.Drawing.Size(202, 20);
-            this.createNewPlatesAsNeededBox.TabIndex = 2;
-            this.createNewPlatesAsNeededBox.Text = "Create new plates as needed";
-            this.createNewPlatesAsNeededBox.UseVisualStyleBackColor = true;
-            //
-            // partFirstGroup
-            //
-            this.partFirstGroup.Anchor = ((System.Windows.Forms.AnchorStyles)(((System.Windows.Forms.AnchorStyles.Top | System.Windows.Forms.AnchorStyles.Left) | System.Windows.Forms.AnchorStyles.Right)));
-            this.partFirstGroup.Controls.Add(this.partFirstCheckBox);
-            this.partFirstGroup.Controls.Add(this.sortOrderLabel);
-            this.partFirstGroup.Controls.Add(this.sortOrderComboBox);
-            this.partFirstGroup.Controls.Add(this.minRemnantLabel);
-            this.partFirstGroup.Controls.Add(this.minRemnantBox);
-            this.partFirstGroup.Location = new System.Drawing.Point(10, 72);
-            this.partFirstGroup.Name = "partFirstGroup";
-            this.partFirstGroup.Size = new System.Drawing.Size(528, 80);
-            this.partFirstGroup.TabIndex = 3;
-            this.partFirstGroup.TabStop = false;
-            this.partFirstGroup.Text = "      Part-First Mode";
-            //
-            // partFirstCheckBox
-            //
-            this.partFirstCheckBox.AutoSize = true;
-            this.partFirstCheckBox.Location = new System.Drawing.Point(10, 0);
-            this.partFirstCheckBox.Name = "partFirstCheckBox";
-            this.partFirstCheckBox.Size = new System.Drawing.Size(15, 14);
-            this.partFirstCheckBox.TabIndex = 0;
-            this.partFirstCheckBox.UseVisualStyleBackColor = true;
-            this.partFirstCheckBox.CheckedChanged += new System.EventHandler(this.partFirstCheckBox_CheckedChanged);
-            //
-            // sortOrderLabel
-            //
-            this.sortOrderLabel.AutoSize = true;
-            this.sortOrderLabel.Location = new System.Drawing.Point(10, 26);
-            this.sortOrderLabel.Name = "sortOrderLabel";
-            this.sortOrderLabel.Size = new System.Drawing.Size(75, 16);
-            this.sortOrderLabel.TabIndex = 1;
-            this.sortOrderLabel.Text = "Sort Order:";
-            //
-            // sortOrderComboBox
-            //
-            this.sortOrderComboBox.DropDownStyle = System.Windows.Forms.ComboBoxStyle.DropDownList;
-            this.sortOrderComboBox.Location = new System.Drawing.Point(100, 23);
-            this.sortOrderComboBox.Name = "sortOrderComboBox";
-            this.sortOrderComboBox.Size = new System.Drawing.Size(180, 24);
-            this.sortOrderComboBox.TabIndex = 2;
-            //
             // minRemnantLabel
             //
             this.minRemnantLabel.AutoSize = true;
-            this.minRemnantLabel.Location = new System.Drawing.Point(10, 54);
+            this.minRemnantLabel.Location = new System.Drawing.Point(10, 193);
             this.minRemnantLabel.Name = "minRemnantLabel";
             this.minRemnantLabel.Size = new System.Drawing.Size(117, 16);
             this.minRemnantLabel.TabIndex = 3;
-            this.minRemnantLabel.Text = "Min Remnant Size:";
+            this.minRemnantLabel.Text = "Min Salvage Size:";
             //
             // minRemnantBox
             //
-            this.minRemnantBox.Location = new System.Drawing.Point(133, 51);
+            this.minRemnantBox.Location = new System.Drawing.Point(155, 190);
             this.minRemnantBox.Name = "minRemnantBox";
             this.minRemnantBox.Size = new System.Drawing.Size(60, 22);
             this.minRemnantBox.TabIndex = 4;
@@ -201,17 +141,19 @@ namespace OpenNest.Forms
             // plateOptimizerGroup
             //
             this.plateOptimizerGroup.Anchor = ((System.Windows.Forms.AnchorStyles)(((System.Windows.Forms.AnchorStyles.Top | System.Windows.Forms.AnchorStyles.Left) | System.Windows.Forms.AnchorStyles.Right)));
+            this.plateOptimizerGroup.Controls.Add(this.minRemnantLabel);
+            this.plateOptimizerGroup.Controls.Add(this.minRemnantBox);
             this.plateOptimizerGroup.Controls.Add(this.optimizePlateSizeBox);
             this.plateOptimizerGroup.Controls.Add(this.plateGrid);
             this.plateOptimizerGroup.Controls.Add(this.salvageRateLabel);
             this.plateOptimizerGroup.Controls.Add(this.salvageRateBox);
             this.plateOptimizerGroup.Controls.Add(this.salvageRatePercentLabel);
-            this.plateOptimizerGroup.Location = new System.Drawing.Point(10, 158);
+            this.plateOptimizerGroup.Location = new System.Drawing.Point(10, 52);
             this.plateOptimizerGroup.Name = "plateOptimizerGroup";
-            this.plateOptimizerGroup.Size = new System.Drawing.Size(528, 188);
+            this.plateOptimizerGroup.Size = new System.Drawing.Size(528, 224);
             this.plateOptimizerGroup.TabIndex = 4;
             this.plateOptimizerGroup.TabStop = false;
-            this.plateOptimizerGroup.Text = "      Plate Optimizer";
+            this.plateOptimizerGroup.Text = "      Stock Options";
             //
             // optimizePlateSizeBox
             //
@@ -318,8 +260,6 @@ namespace OpenNest.Forms
             this.platesTab.PerformLayout();
             ((System.ComponentModel.ISupportInitialize)(this.partsGrid)).EndInit();
             ((System.ComponentModel.ISupportInitialize)(this.plateGrid)).EndInit();
-            this.partFirstGroup.ResumeLayout(false);
-            this.partFirstGroup.PerformLayout();
             this.plateOptimizerGroup.ResumeLayout(false);
             this.plateOptimizerGroup.PerformLayout();
             this.buttonPanel.ResumeLayout(false);
@@ -335,11 +275,6 @@ namespace OpenNest.Forms
         private System.Windows.Forms.Label summaryLabel;
         private System.Windows.Forms.Label engineLabel;
         private System.Windows.Forms.ComboBox engineComboBox;
-        private System.Windows.Forms.CheckBox createNewPlatesAsNeededBox;
-        private System.Windows.Forms.GroupBox partFirstGroup;
-        private System.Windows.Forms.CheckBox partFirstCheckBox;
-        private System.Windows.Forms.Label sortOrderLabel;
-        private System.Windows.Forms.ComboBox sortOrderComboBox;
         private System.Windows.Forms.Label minRemnantLabel;
         private System.Windows.Forms.TextBox minRemnantBox;
         private System.Windows.Forms.GroupBox plateOptimizerGroup;
diff --git a/OpenNest/Forms/AutoNestForm.cs b/OpenNest/Forms/AutoNestForm.cs
index a932db2..525f50a 100644
--- a/OpenNest/Forms/AutoNestForm.cs
+++ b/OpenNest/Forms/AutoNestForm.cs
@@ -22,11 +22,6 @@ namespace OpenNest.Forms
             LoadDefaultPlateOptions();
             SetPlateOptimizerVisible(false);
 
-            sortOrderComboBox.Items.Add("Bounding Box Area");
-            sortOrderComboBox.Items.Add("Size");
-            sortOrderComboBox.SelectedIndex = 0;
-            SetPartFirstVisible(false);
-
             partsGrid.DataError += PartsGrid_DataError;
         }
 
@@ -36,12 +31,6 @@ namespace OpenNest.Forms
             set { engineComboBox.SelectedItem = value; }
         }
 
-        public bool AllowPlateCreation
-        {
-            get { return createNewPlatesAsNeededBox.Checked; }
-            set { createNewPlatesAsNeededBox.Checked = value; }
-        }
-
         public bool OptimizePlateSize
         {
             get { return optimizePlateSizeBox.Checked; }
@@ -59,22 +48,6 @@ namespace OpenNest.Forms
             set { salvageRateBox.Text = (value * 100).ToString("F0"); }
         }
 
-        public bool PartFirstMode
-        {
-            get { return partFirstCheckBox.Checked; }
-            set { partFirstCheckBox.Checked = value; }
-        }
-
-        public PartSortOrder SortOrder
-        {
-            get
-            {
-                if (sortOrderComboBox.SelectedItem is string s && s == "Size")
-                    return PartSortOrder.Size;
-                return PartSortOrder.BoundingBoxArea;
-            }
-        }
-
         public double MinRemnantSize
         {
             get
@@ -292,17 +265,6 @@ namespace OpenNest.Forms
             salvageRateLabel.Visible = visible;
             salvageRateBox.Visible = visible;
             salvageRatePercentLabel.Visible = visible;
-        }
-
-        private void partFirstCheckBox_CheckedChanged(object sender, EventArgs e)
-        {
-            SetPartFirstVisible(partFirstCheckBox.Checked);
-        }
-
-        private void SetPartFirstVisible(bool visible)
-        {
-            sortOrderLabel.Visible = visible;
-            sortOrderComboBox.Visible = visible;
             minRemnantLabel.Visible = visible;
             minRemnantBox.Visible = visible;
         }
diff --git a/OpenNest/Forms/JobEngineNest.cs b/OpenNest/Forms/JobEngineNest.cs
index 7f667fc..f1f1865 100644
--- a/OpenNest/Forms/JobEngineNest.cs
+++ b/OpenNest/Forms/JobEngineNest.cs
@@ -9,91 +9,11 @@ using OpenNest.Geometry;
 namespace OpenNest.Forms
 {
     /// <summary>
-    /// Desktop adapter for whole-job engines (StockLadder and Engines/ plug-ins): builds the
-    /// NestJob from auto-nest items, translates NestJobProgress for NestProgressForm, and maps
-    /// result poses back onto the nest's own drawings.
+    /// Desktop progress adapter for every whole-job engine. Building, validation and binding
+    /// belong to the shared NestPipeline.
     /// </summary>
     internal static class JobEngineNest
     {
-        public static NestJob BuildJob(
-            IReadOnlyList<NestItem> items,
-            Plate template,
-            List<PlateOption> plateOptions,
-            double salvageRate,
-            double minRemnantSize,
-            int maxPlates,
-            out Dictionary<string, Drawing> drawingsByPartId
-        )
-        {
-            var parts = new List<NestJobPart>();
-            drawingsByPartId = new Dictionary<string, Drawing>(StringComparer.Ordinal);
-
-            for (var i = 0; i < items.Count; i++)
-            {
-                if (items[i].Quantity <= 0)
-                    continue;
-
-                var partId = $"part-{i}";
-                parts.Add(DrawingJobMapper.FromItem(partId, items[i]));
-                drawingsByPartId[partId] = items[i].Drawing;
-            }
-
-            var stock = new List<NestPlateStock>();
-
-            if (plateOptions != null && plateOptions.Count > 0)
-            {
-                for (var i = 0; i < plateOptions.Count; i++)
-                {
-                    var option = plateOptions[i];
-                    stock.Add(
-                        new NestPlateStock(
-                            $"option-{i}",
-                            new Size(option.Width, option.Length),
-                            quantity: null,
-                            template.PartSpacing,
-                            template.EdgeSpacing,
-                            template.Quadrant
-                        )
-                    );
-                }
-            }
-            else
-            {
-                stock.Add(DrawingJobMapper.FromPlate("plate", template, quantity: null));
-            }
-
-            var options = new NestJobOptions(
-                maxPlates: maxPlates,
-                salvageRate: plateOptions != null && plateOptions.Count > 0 ? salvageRate : 0,
-                minimumSalvageDimension: minRemnantSize
-            );
-
-            return new NestJob(parts, stock, options);
-        }
-
-        /// <summary>Parts for one result sheet, bound to the caller's drawings.</summary>
-        public static List<Part> CreateParts(
-            NestJobPlateResult sheet,
-            IReadOnlyDictionary<string, Drawing> drawingsByPartId
-        )
-        {
-            var parts = new List<Part>(sheet.Placements.Count);
-
-            foreach (var pose in sheet.Placements)
-            {
-                if (!drawingsByPartId.TryGetValue(pose.PartId, out var drawing))
-                    continue;
-
-                var part = new Part(drawing);
-                part.Rotate(pose.Rotation);
-                part.Location = new Vector(pose.X, pose.Y);
-                part.UpdateBounds();
-                parts.Add(part);
-            }
-
-            return parts;
-        }
-
         /// <summary>
         /// Forwards job progress to a NestProgress sink. An engine's optional LegacyProgress detail
         /// (live preview parts) passes through; otherwise the stage and committed counts become a
diff --git a/OpenNest/Forms/MainForm.cs b/OpenNest/Forms/MainForm.cs
index 2a43ede..5d31d5b 100644
--- a/OpenNest/Forms/MainForm.cs
+++ b/OpenNest/Forms/MainForm.cs
@@ -1146,336 +1146,132 @@ namespace OpenNest.Forms
 
         private async void RunAutoNest_Click(object sender, EventArgs e)
         {
-            var form = new AutoNestForm(activeForm.Nest);
-            form.AllowPlateCreation = true;
-
-            if (activeForm.Nest.PlateOptions.Count > 0)
-                form.LoadPlateOptions(activeForm.Nest.PlateOptions, activeForm.Nest.SalvageRate);
-
-            if (form.ShowDialog() != System.Windows.Forms.DialogResult.OK)
+            var target = activeForm;
+            if (target == null || target.IsDisposed || target.PlateView.Plate == null)
                 return;
-
-            if (form.EngineName != null)
+            var views = MdiChildren.OfType<EditNestForm>()
+                .Where(f => ReferenceEquals(f.Nest, target.Nest)).Select(f => f.PlateView).ToArray();
+            if (nestingInProgress || Application.OpenForms.OfType<NestProgressForm>().Any()
+                || views.Any(v => v.IsFillInProgress || v.Actions.CurrentAction?.IsBusy() == true))
             {
-                EngineSelection.EngineName = form.EngineName;
-                engineComboBox.SelectedItem = form.EngineName;
+                MessageBox.Show(this, "Finish or cancel the current plate operation before Auto Nest.",
+                    "Auto Nest", MessageBoxButtons.OK, MessageBoxIcon.Information);
+                return;
             }
+            foreach (var view in views)
+                view.SetAction(typeof(ActionSelect));
+
+            using var form = new AutoNestForm(target.Nest);
+            if (target.Nest.PlateOptions.Count > 0)
+                form.LoadPlateOptions(target.Nest.PlateOptions, target.Nest.SalvageRate);
+            if (form.ShowDialog(this) != DialogResult.OK)
+                return;
 
             var items = form.GetNestItems();
-
             if (!items.Any(it => it.Quantity > 0))
                 return;
-
-            var optimizePlateSize = form.OptimizePlateSize;
-            var plateOptions = optimizePlateSize ? form.GetPlateOptions() : null;
-            var salvageRate = form.SalvageRate;
-            var partFirstMode = form.PartFirstMode;
-            var sortOrder = form.SortOrder;
-            var minRemnantSize = form.MinRemnantSize;
-            var allowPlateCreation = form.AllowPlateCreation;
-
-            if (optimizePlateSize)
+            var engineName = form.EngineName ?? EngineSelection.EngineName;
+            EngineSelection.EngineName = engineName;
+            engineComboBox.SelectedItem = engineName;
+            var plateOptions = form.OptimizePlateSize ? form.GetPlateOptions() : null;
+            using var cts = new CancellationTokenSource();
+            nestingCts = cts;
+            using var progressForm = new NestProgressForm(cts, showPlateRow: true)
             {
-                activeForm.Nest.PlateOptions = plateOptions;
-                activeForm.Nest.SalvageRate = salvageRate;
-            }
-
-            nestingCts = new CancellationTokenSource();
-            var progressForm = new NestProgressForm(nestingCts, showPlateRow: true);
-
-            var jobEngineName = EngineSelection.IsFillStrategy(EngineSelection.EngineName)
-                ? null
-                : EngineSelection.EngineName;
-            progressForm.AllowAccept = jobEngineName == null;
-
+                AllowAccept = false,
+                HoldOpenUntilCompleted = true,
+            };
+            var receivingProgress = true;
             var progress = new Progress<NestProgress>(p =>
             {
+                if (!receivingProgress || target.IsDisposed || cts.IsCancellationRequested)
+                    return;
                 progressForm.UpdateProgress(p);
-
                 if (p.IsOverallBest)
-                    activeForm.PlateView.SetActiveParts(p.BestParts);
-                activeForm.PlateView.ActiveWorkArea = p.ActiveWorkArea;
+                    target.PlateView.SetActiveParts(p.BestParts);
+                target.PlateView.ActiveWorkArea = p.ActiveWorkArea;
             });
-
-            progressForm.Show(this);
+            var jobProgress = JobEngineNest.CreateProgress(engineName, progress);
             SetNestingLockout(true);
-
             try
             {
-                if (jobEngineName != null)
-                    await RunJobEngineAsync(
-                        jobEngineName,
-                        items,
-                        progressForm,
-                        progress,
-                        nestingCts.Token,
-                        plateOptions,
-                        salvageRate,
-                        minRemnantSize
-                    );
-                else
-                    await RunAutoNestAsync(
-                        items,
-                        progressForm,
-                        progress,
-                        nestingCts.Token,
-                        plateOptions,
-                        salvageRate,
-                        partFirstMode,
-                        sortOrder,
-                        minRemnantSize,
-                        allowPlateCreation
-                    );
-            }
-            catch (Exception ex)
-            {
-                activeForm.PlateView.ClearPreviewParts();
-                MessageBox.Show(
-                    $"Nesting error: {ex.Message}",
-                    "Error",
-                    MessageBoxButtons.OK,
-                    MessageBoxIcon.Error
-                );
-            }
-            finally
-            {
-                activeForm.PlateView.ActiveWorkArea = null;
-                progressForm.Close();
-                SetNestingLockout(false);
-                nestingCts.Dispose();
-                nestingCts = null;
-            }
-        }
+                var request = new NestPipelineRequest(engineName, items,
+                    NestStockBuilder.FromTemplate(target.PlateView.Plate, plateOptions),
+                    new NestJobOptions(maxPlates: 100,
+                        salvageRate: plateOptions?.Count > 0 ? form.SalvageRate : 0,
+                        minimumSalvageDimension: form.MinRemnantSize));
 
-        private async Task RunAutoNestAsync(
-            List<NestItem> items,
-            NestProgressForm progressForm,
-            IProgress<NestProgress> progress,
-            CancellationToken token,
-            List<PlateOption> plateOptions = null,
-            double salvageRate = 0.5,
-            bool partFirstMode = false,
-            PartSortOrder sortOrder = PartSortOrder.BoundingBoxArea,
-            double minRemnantSize = 12.0,
-            bool allowPlateCreation = true
-        )
-        {
-            if (partFirstMode)
-            {
-                var existingPlates = new List<Plate>();
-                for (var i = 0; i < activeForm.Nest.Plates.Count; i++)
+                async Task<NestPipelineResult> SolveAsync()
                 {
-                    var p = activeForm.Nest.Plates[i];
-                    if (p.Parts.Count > 0)
-                        existingPlates.Add(p);
-                }
-
-                var template = activeForm.PlateView.Plate;
-
-                var nestOptions = new MultiPlateNestOptions
-                {
-                    Template = template,
-                    PlateOptions = plateOptions,
-                    SalvageRate = salvageRate,
-                    SortOrder = sortOrder,
-                    MinRemnantSize = minRemnantSize,
-                    AllowPlateCreation = allowPlateCreation,
-                    Strategy = EngineSelection.FillStrategy,
-                };
-
-                var result = await Task.Run(() =>
-                    MultiPlateNester.Nest(items, nestOptions, existingPlates, progress, token)
-                );
-
-                foreach (var pr in result.Plates)
-                {
-                    if (pr.IsNew)
+                    try
                     {
-                        var plate = GetOrCreatePlate();
-                        plate.Size = pr.Plate.Size;
-                        plate.Parts.AddRange(pr.Parts);
+                        return await Task.Run(() => NestPipeline.Run(request, jobProgress, cts.Token));
+                    }
+                    finally
+                    {
+                        receivingProgress = false;
+                        progressForm.ShowCompleted();
+                        progressForm.Close();
                     }
                 }
 
-                activeForm.Nest.UpdateDrawingQuantities();
-                progressForm.ShowCompleted();
-                return;
-            }
+                var solve = SolveAsync();
+                // Owned modal progress holds drawings/plates stable through solve and cancellation.
+                if (!solve.IsCompleted)
+                    progressForm.ShowDialog(this);
+                var result = await solve;
+                cts.Token.ThrowIfCancellationRequested();
+                target.PlateView.ClearPreviewParts();
+                target.PlateView.ActiveWorkArea = null;
 
-            const int maxPlates = 100;
-
-            for (var plateIndex = 0; plateIndex < maxPlates; plateIndex++)
-            {
-                var remaining = items.Where(i => i.Quantity > 0).ToList();
-
-                if (remaining.Count == 0 || token.IsCancellationRequested)
-                    break;
-
-                var plate = GetOrCreatePlate();
-
-                var placed = await NestSinglePlateAsync(
-                    plate,
-                    plateIndex,
-                    remaining,
-                    progressForm,
-                    progress,
-                    token,
-                    plateOptions,
-                    salvageRate
-                );
-
-                if (!placed)
-                    break;
-            }
-
-            activeForm.Nest.UpdateDrawingQuantities();
-            progressForm.ShowCompleted();
-        }
-
-        /// <summary>
-        /// Whole-job path for StockLadder and Engines/ plug-ins: the engine owns plate count and
-        /// size selection, reports NestJobProgress into the progress form, and its result is
-        /// committed onto empty or new plates. Cancellation discards the run (engines throw).
-        /// </summary>
-        private async Task RunJobEngineAsync(
-            string engineName,
-            List<NestItem> items,
-            NestProgressForm progressForm,
-            IProgress<NestProgress> progress,
-            CancellationToken token,
-            List<PlateOption> plateOptions,
-            double salvageRate,
-            double minRemnantSize
-        )
-        {
-            const int maxPlates = 100;
-
-            var engine = NestingEngineRegistry.Create(engineName);
-            var job = JobEngineNest.BuildJob(
-                items,
-                activeForm.PlateView.Plate,
-                plateOptions,
-                salvageRate,
-                minRemnantSize,
-                maxPlates,
-                out var drawingsByPartId
-            );
-            var jobProgress = JobEngineNest.CreateProgress(engineName, progress);
-
-            NestJobResult result;
-            try
-            {
-                result = await Task.Run(() => engine.Solve(job, jobProgress, token));
-            }
-            catch (OperationCanceledException) when (token.IsCancellationRequested)
-            {
-                activeForm.PlateView.ClearPreviewParts();
-                return;
-            }
-
-            activeForm.PlateView.ClearPreviewParts();
-
-            foreach (var sheet in result.Plates)
-            {
-                var parts = JobEngineNest.CreateParts(sheet, drawingsByPartId);
-                if (parts.Count == 0)
-                    continue;
-
-                var plate = GetOrCreatePlate();
-                plate.Size = sheet.Stock.Size;
-                plate.Parts.AddRange(parts);
-            }
-
-            activeForm.PlateView.Invalidate();
-            activeForm.Nest.UpdateDrawingQuantities();
-            progressForm.ShowCompleted();
-
-            if (result.Status != NestJobStatus.Complete)
-                MessageBox.Show(
-                    $"{engineName} could not place every part ({result.StopReason}).",
-                    "Auto Nest",
-                    MessageBoxButtons.OK,
-                    MessageBoxIcon.Information
-                );
-        }
-
-        private Plate GetOrCreatePlate()
-        {
-            var plate = activeForm.PlateManager.GetOrCreateEmpty();
-            activeForm.PlateManager.LoadLast();
-            return plate;
-        }
-
-        private async Task<bool> NestSinglePlateAsync(
-            Plate plate,
-            int plateIndex,
-            List<NestItem> items,
-            NestProgressForm progressForm,
-            IProgress<NestProgress> progress,
-            CancellationToken token,
-            List<PlateOption> plateOptions = null,
-            double salvageRate = 0.5
-        )
-        {
-            List<Part> nestParts;
-
-            if (plateOptions != null && plateOptions.Count > 0)
-            {
-                var result = await Task.Run(() =>
-                    PlateOptimizer.Optimize(
-                        items,
-                        plateOptions,
-                        salvageRate,
-                        plate,
-                        progress,
-                        token,
-                        EngineSelection.FillStrategy
-                    )
-                );
-
-                if (
-                    result == null
-                    || result.Parts.Count == 0
-                    || (token.IsCancellationRequested && !progressForm.Accepted)
-                )
-                    return false;
-
-                plate.Size = new Geometry.Size(result.ChosenSize.Width, result.ChosenSize.Length);
-                nestParts = result.Parts;
-
-                // Deduct placed quantities — the optimizer clones items internally
-                // so the originals are untouched after dry runs.
-                foreach (var item in items)
+                var allowInvalid = false;
+                if (!result.IsValid)
                 {
-                    var placed = nestParts.Count(p => p.BaseDrawing.Name == item.Drawing.Name);
-                    item.Quantity = System.Math.Max(0, item.Quantity - placed);
+                    using var review = new NestValidationForm(result.Violations, result.CanKeep);
+                    if (review.ShowDialog(this) != DialogResult.OK)
+                        return;
+                    allowInvalid = true;
                 }
+
+                var applied = NestPipelineCommit.ApplyToEmptyPlates(result, target.PlateManager,
+                    allowInvalid, cts.Token);
+                if (applied.Count > 0)
+                    target.PlateManager.LoadAt(target.Nest.Plates.IndexOf(applied[0]));
+                if (plateOptions?.Count > 0)
+                {
+                    target.Nest.PlateOptions = plateOptions;
+                    target.Nest.SalvageRate = form.SalvageRate;
+                }
+                target.PlateView.Invalidate();
+                if (allowInvalid)
+                {
+                    target.OverlapDisplay = OverlapDisplayMode.Both;
+                    await target.CheckOverlapsAsync();
+                }
+                if (result.Status != NestJobStatus.Complete)
+                    MessageBox.Show(this, $"{engineName} could not place every part ({result.StopReason}).",
+                        "Auto Nest", MessageBoxButtons.OK, MessageBoxIcon.Information);
             }
-            else
+            catch (OperationCanceledException) when (cts.IsCancellationRequested)
             {
-                // Same preview flow as before: fill the current plate's remaining demand with the
-                // selected strategy, then commit the returned parts. App-scoped selection — the
-                // process-global engine registry is never consulted.
-                nestParts = await Task.Run(() =>
-                    PlateFillService.Nest(
-                        EngineSelection.FillStrategy,
-                        plate,
-                        items,
-                        plateIndex,
-                        progress,
-                        token
-                    )
-                );
+                // Stop discards the entire proposal, including engines that ignore cancellation.
+            }
+            catch (Exception ex)
+            {
+                MessageBox.Show(this, $"Nesting error: {ex.Message}", "Auto Nest",
+                    MessageBoxButtons.OK, MessageBoxIcon.Error);
+            }
+            finally
+            {
+                receivingProgress = false;
+                if (!target.IsDisposed)
+                {
+                    target.PlateView.ClearPreviewParts();
+                    target.PlateView.ActiveWorkArea = null;
+                }
+                SetNestingLockout(false);
+                nestingCts = null;
             }
-
-            activeForm.PlateView.ClearPreviewParts();
-
-            if (nestParts.Count == 0 || (token.IsCancellationRequested && !progressForm.Accepted))
-                return false;
-
-            plate.Parts.AddRange(nestParts);
-            activeForm.PlateView.Invalidate();
-            return true;
         }
 
         private void SequenceAllPlates_Click(object sender, EventArgs e)
diff --git a/OpenNest/Forms/NestProgressForm.cs b/OpenNest/Forms/NestProgressForm.cs
index 57db375..3834477 100644
--- a/OpenNest/Forms/NestProgressForm.cs
+++ b/OpenNest/Forms/NestProgressForm.cs
@@ -25,6 +25,20 @@ namespace OpenNest.Forms
         private readonly System.Windows.Forms.Timer fadeTimer;
         private readonly Dictionary<Label, (int remaining, Color flashColor)> fadeCounters = new();
         private bool hasReceivedProgress;
+        private bool completed;
+
+        /// <summary>Keep the owner disabled until a whole-job worker finishes after Stop/close.</summary>
+        private bool holdOpenUntilCompleted;
+        public bool HoldOpenUntilCompleted
+        {
+            get => holdOpenUntilCompleted;
+            set
+            {
+                holdOpenUntilCompleted = value;
+                if (value)
+                    stopButton.Enabled = true; // Plug-ins need not report progress before cancellation.
+            }
+        }
 
         public bool Accepted { get; private set; }
 
@@ -94,6 +108,7 @@ namespace OpenNest.Forms
 
         public void ShowCompleted()
         {
+            completed = true;
             if (IsDisposed || !IsHandleCreated)
                 return;
 
@@ -143,13 +158,19 @@ namespace OpenNest.Forms
 
         protected override void OnFormClosing(FormClosingEventArgs e)
         {
+            if (HoldOpenUntilCompleted && !completed)
+            {
+                cts.Cancel();
+                e.Cancel = true;
+                return;
+            }
             fadeTimer.Stop();
             fadeTimer.Dispose();
             elapsedTimer.Stop();
             elapsedTimer.Dispose();
             stopwatch.Stop();
 
-            if (!cts.IsCancellationRequested)
+            if (!completed && !cts.IsCancellationRequested)
                 cts.Cancel();
 
             base.OnFormClosing(e);
diff --git a/OpenNest/Forms/NestValidationForm.cs b/OpenNest/Forms/NestValidationForm.cs
new file mode 100644
index 0000000..23d7dd9
--- /dev/null
+++ b/OpenNest/Forms/NestValidationForm.cs
@@ -0,0 +1,60 @@
+using System.Collections.Generic;
+using System.Drawing;
+using System.Windows.Forms;
+
+namespace OpenNest.Forms;
+
+/// <summary>A fresh, explicit decision for each invalid automatic nesting proposal.</summary>
+public sealed class NestValidationForm : Form
+{
+    public NestValidationForm(IReadOnlyList<string> violations, bool canKeep)
+    {
+        Text = "Auto Nest — validation problems";
+        StartPosition = FormStartPosition.CenterParent;
+        ClientSize = new Size(740, 440);
+        MinimizeBox = false;
+        MaximizeBox = false;
+        ShowInTaskbar = false;
+        var summary = new Label
+        {
+            Dock = DockStyle.Top,
+            Height = 70,
+            Padding = new Padding(10),
+            Text = canKeep
+                ? "This layout failed validation. Discard leaves your plates unchanged. Keep anyway applies the entire layout and enables Overlap Check.\nOverlap Check highlights material overlaps; spacing, stock and rotation warnings remain listed here."
+                : "The engine returned malformed placements. No layout can be kept. Discard leaves your plates unchanged.",
+        };
+        var report = new TextBox
+        {
+            Dock = DockStyle.Fill,
+            Multiline = true,
+            ReadOnly = true,
+            ScrollBars = ScrollBars.Both,
+            WordWrap = false,
+            Text = string.Join("\r\n\r\n", violations),
+        };
+        var buttons = new FlowLayoutPanel
+        {
+            Dock = DockStyle.Bottom,
+            Height = 48,
+            FlowDirection = FlowDirection.RightToLeft,
+            Padding = new Padding(6),
+        };
+        var discard = new Button { Text = "Discard", AutoSize = true, DialogResult = DialogResult.Cancel };
+        var keep = new Button
+        {
+            Text = "Keep anyway",
+            AutoSize = true,
+            Enabled = canKeep,
+            DialogResult = DialogResult.OK,
+        };
+        buttons.Controls.Add(discard);
+        buttons.Controls.Add(keep);
+        Controls.Add(report);
+        Controls.Add(summary);
+        Controls.Add(buttons);
+        AcceptButton = discard;
+        CancelButton = discard;
+        ActiveControl = discard;
+    }
+}
diff --git a/docs/automatic-nesting.md b/docs/automatic-nesting.md
new file mode 100644
index 0000000..5011e45
--- /dev/null
+++ b/docs/automatic-nesting.md
@@ -0,0 +1,38 @@
+# Automatic nesting pipeline
+
+`NestPipeline.Run` is the shared whole-job boundary in `OpenNest.Engine`:
+
+1. Snapshot caller requirements and stock into a `NestJob`.
+2. Resolve the selected name through `NestingEngineRegistry` (built-ins and plug-ins use the same path).
+3. Run the engine without mutating caller drawings or plates.
+4. Check returned placements with the independent `NestLayoutCheck` used by the benchmark.
+5. Bind a representable result back to the caller's drawing references; the caller decides whether to commit it.
+
+`NestStockBuilder.FromTemplate` snapshots sheet options and spacing settings for multiple-sheet jobs. `SinglePlate` offers exactly one physical sheet, regardless of the legacy plate repeat quantity. `NestPipelineCommit.ApplyToEmptyPlates` applies accepted desktop proposals to empty/new plates with the checked size, quadrant, spacing and quantity-one semantics. It never fills occupied plates.
+
+## Desktop Auto Nest
+
+Every engine selected in **Nest > Auto Nest** uses the pipeline. Part-First and its sorting controls are removed. Use interactive Fill Area/remnant tools for leftover space on occupied sheets; these are not whole-job nesting.
+
+Auto Nest starts on empty/new sheets and does not change existing populated plates. Stock Options offers sheet sizes and salvage settings; minimum salvage size is part of that section, not a Part-First option. The maximum remains 100 physical sheets per run.
+
+Progress is owned and modal so the input drawings cannot be edited while a worker uses them. Stop or closing progress cancels and discards the whole proposal. The dialog waits for the worker to finish; no engine has an Accept-early button on this path. A plug-in that ignores the cancellation token cannot commit its late result.
+
+Every invalid result shows the validation report before any plates are changed:
+
+- **Discard** is the default button and the Escape action. No proposed parts or sheets are applied.
+- **Keep anyway** requires an explicit click and keeps the entire representable proposal, then enables Overlap Check.
+- Malformed output (unknown requirements or nonfinite poses) is not keepable. It cannot be faithfully represented as the proposed layout; no partial/truncated proposal is offered.
+
+Overlap Check displays material overlaps, not every spacing/stock/rotation failure in the report. A layout passing validation may still be incomplete; completeness and stop reason are separate from geometric validity. This check does not replace pre-post CNC verification.
+
+The selected engine is saved in `%APPDATA%\OpenNest\engine-selection.json`.
+Selection is restored after plug-ins load. If the saved engine is unavailable,
+Default is selected and the status bar reports the fallback; startup does not
+replace the saved missing-engine preference.
+
+## Integration constraints
+
+Callers must hold drawings and target state stable from snapshot through attachment. Do not append whole-job placements to an occupied target or flatten multiple returned sheets onto one plate: that would commit a layout different from the one checked. Do not trust arbitrary engine fulfillment metadata as a substitute for counting returned placements.
+
+Interactive fills are outside this contract and still use `PlateFillService`. The benchmark invokes the same independent validator. Console/MCP/API migration is a separate adoption step; the existence of the pipeline does not imply every front end already calls it.