diff --git a/OpenNest.Engine/CuttingPlanning/CuttingPlanModels.cs b/OpenNest.Engine/CuttingPlanning/CuttingPlanModels.cs
index e3f3d98..1e165dc 100644
--- a/OpenNest.Engine/CuttingPlanning/CuttingPlanModels.cs
+++ b/OpenNest.Engine/CuttingPlanning/CuttingPlanModels.cs
@@ -11,7 +11,8 @@ namespace OpenNest.Engine.CuttingPlanning;
 
 /// <summary>
 /// Caller-side direct-XY input. Regeneration requires explicit confirmed parameters.
-/// Keep sources/settings stable during Capture. This is not an Apply request.
+/// Keep sources/settings stable during Capture. Only plate-scoped requests (<see cref="ForPlate"/>)
+/// record the state that CuttingPlanService.Apply checks; a detached part list cannot be applied.
 /// </summary>
 public sealed class CuttingPlanRequest
 {
@@ -30,19 +31,18 @@ public sealed class CuttingPlanRequest
 
     /// <summary>
     /// Plate scope: plans the plate's current parts and captures its exact state, so a Ready
-    /// result can later be applied through <see cref="CuttingPlanService.Apply"/>.
+    /// result can later be applied through CuttingPlanService.Apply. A factory rather than a
+    /// constructor overload, so <c>new CuttingPlanRequest(null)</c> stays unambiguous.
     /// </summary>
-    public CuttingPlanRequest(Plate plate, Vector startPoint = default, int expansionBudget = 20000,
+    public static CuttingPlanRequest ForPlate(Plate plate, Vector startPoint = default, int expansionBudget = 20000,
         CuttingParameters confirmedParameters = null, IEnumerable<Part> eligibleParts = null,
-        bool preservePartOrder = false, int maxEntries = 16)
-        : this(plate?.Parts, startPoint, expansionBudget, confirmedParameters, eligibleParts,
+        bool preservePartOrder = false, int maxEntries = 16) =>
+        new(plate?.Parts, startPoint, expansionBudget, confirmedParameters, eligibleParts,
             preservePartOrder, maxEntries)
-    {
-        Plate = plate;
-    }
+        { Plate = plate };
 
     /// <summary>The plate scope, or null for a detached part list that cannot be applied.</summary>
-    public Plate Plate { get; }
+    public Plate Plate { get; private init; }
     public CuttingParameters ConfirmedParameters { get; }
     public IReadOnlyList<Part> EligibleParts { get; }
     public bool PreservePartOrder { get; }
@@ -167,8 +167,9 @@ public sealed record CuttingPlanFinding(int? SourceOrdinal, Part SourcePart,
     int? OtherSourceOrdinal, Part OtherSourcePart, PostVerificationKind? Kind, string Message);
 
 /// <summary>
-/// A replayed direct-XY proposal, optionally with regenerated programs. Not physical
-/// safety, posting consent, dependency readiness or an atomic Apply payload. Failures contain no proposals.
+/// A replayed direct-XY proposal, optionally with regenerated programs, that respects the
+/// captured cutoff/containment prerequisites. Not physical safety or posting consent. Apply
+/// installs it only for a plate-scoped request whose plate is unchanged. Failures contain no proposals.
 /// </summary>
 public sealed class CuttingPlanResult
 {
diff --git a/OpenNest.Tests/CuttingPlanning/CuttingDependencyTests.cs b/OpenNest.Tests/CuttingPlanning/CuttingDependencyTests.cs
index eb89727..64270a7 100644
--- a/OpenNest.Tests/CuttingPlanning/CuttingDependencyTests.cs
+++ b/OpenNest.Tests/CuttingPlanning/CuttingDependencyTests.cs
@@ -18,7 +18,7 @@ public class CuttingDependencyTests
     {
         var parameters = ExplicitContourTests.Parameters();
         var (_, plate, p, q, cut) = CutOffPlate(parameters, orphan: false);
-        var request = new CuttingPlanRequest(plate, new Vector(11, 12.5),
+        var request = CuttingPlanRequest.ForPlate(plate, new Vector(11, 12.5),
             confirmedParameters: regenerate ? parameters : null);
         var snapshot = CuttingPlanService.Capture(request);
         Assert.Equal(new[] { 2 }, snapshot.Dependencies.PrerequisitesOf(0));
@@ -43,7 +43,7 @@ public class CuttingDependencyTests
     public void Apply_CutOffReclassifiedAfterPlanning_IsStale()
     {
         var (_, plate, p, q, cut) = CutOffPlate(ExplicitContourTests.Parameters(), orphan: false);
-        var result = CuttingPlanService.Plan(new CuttingPlanRequest(plate, new Vector(11, 12.5)));
+        var result = CuttingPlanService.Plan(CuttingPlanRequest.ForPlate(plate, new Vector(11, 12.5)));
         Assert.Equal(CuttingPlanStatus.Ready, result.Status);
         cut.BaseDrawing.IsCutOff = false;
 
@@ -57,7 +57,7 @@ public class CuttingDependencyTests
     public void Plan_OrphanedCutOff_PrecedesEveryPart()
     {
         var (_, plate, p, q, cut) = CutOffPlate(ExplicitContourTests.Parameters(), orphan: true);
-        var snapshot = CuttingPlanService.Capture(new CuttingPlanRequest(plate, new Vector(11, 12.5)));
+        var snapshot = CuttingPlanService.Capture(CuttingPlanRequest.ForPlate(plate, new Vector(11, 12.5)));
         Assert.Equal(new[] { 2 }, snapshot.Dependencies.PrerequisitesOf(0));
         Assert.Equal(new[] { 2 }, snapshot.Dependencies.PrerequisitesOf(1));
 
@@ -72,7 +72,7 @@ public class CuttingDependencyTests
     {
         var (_, plate, p, _, cut) = CutOffPlate(ExplicitContourTests.Parameters(), orphan: false);
 
-        var result = CuttingPlanService.Plan(new CuttingPlanRequest(plate, new Vector(11, 12.5), preservePartOrder: true));
+        var result = CuttingPlanService.Plan(CuttingPlanRequest.ForPlate(plate, new Vector(11, 12.5), preservePartOrder: true));
 
         Assert.Equal(CuttingPlanStatus.ConstraintConflict, result.Status);
         Assert.Empty(result.ProposedOrder);
@@ -89,7 +89,7 @@ public class CuttingDependencyTests
     {
         var parameters = ExplicitContourTests.Parameters();
         var (_, plate, _, _, _) = CutOffPlate(parameters, orphan: false);
-        var snapshot = CuttingPlanService.Capture(new CuttingPlanRequest(plate, new Vector(11, 12.5),
+        var snapshot = CuttingPlanService.Capture(CuttingPlanRequest.ForPlate(plate, new Vector(11, 12.5),
             confirmedParameters: regenerate ? parameters : null));
         var ready = CuttingPlanService.Plan(snapshot);
         Assert.Equal(CuttingPlanStatus.Ready, ready.Status);
@@ -120,7 +120,7 @@ public class CuttingDependencyTests
     public void Plan_PartInsideAHostCutout_IsCutBeforeTheHost()
     {
         var (plate, host, inner) = NestedPlate(Rectangle(2.7, 2.7, 0.6, 0.6));
-        var snapshot = CuttingPlanService.Capture(new CuttingPlanRequest(plate));
+        var snapshot = CuttingPlanService.Capture(CuttingPlanRequest.ForPlate(plate));
         Assert.Equal(new[] { 1 }, snapshot.Dependencies.PrerequisitesOf(0));
         Assert.Empty(snapshot.Dependencies.PrerequisitesOf(1));
 
@@ -129,7 +129,7 @@ public class CuttingDependencyTests
         Assert.True(result.Status == CuttingPlanStatus.Ready, Describe(result));
         Assert.Equal(new[] { inner, host }, result.ProposedOrder.Select(o => o.SourcePart));
 
-        var preserved = CuttingPlanService.Plan(new CuttingPlanRequest(plate, preservePartOrder: true));
+        var preserved = CuttingPlanService.Plan(CuttingPlanRequest.ForPlate(plate, preservePartOrder: true));
         Assert.Equal(CuttingPlanStatus.ConstraintConflict, preserved.Status);
         var finding = Assert.Single(preserved.Findings);
         Assert.Same(host, finding.SourcePart);
@@ -143,7 +143,7 @@ public class CuttingDependencyTests
         // Same insert as above plus a remote rapid and scribe mark: material is unchanged, so
         // the inner-before-host prerequisite must not depend on whole-program bounds.
         var (plate, host, inner) = NestedPlate(Marked(Rectangle(2.7, 2.7, 0.6, 0.6)));
-        var snapshot = CuttingPlanService.Capture(new CuttingPlanRequest(plate));
+        var snapshot = CuttingPlanService.Capture(CuttingPlanRequest.ForPlate(plate));
         Assert.Null(snapshot.Findings.FirstOrDefault()?.Message);
         Assert.True(inner.BoundingBox.Left < host.BoundingBox.Left);
 
@@ -158,7 +158,7 @@ public class CuttingDependencyTests
     {
         var (plate, host, inner) = NestedPlate(Rectangle(3.6, 2.8, 0.8, 0.4));
 
-        var result = CuttingPlanService.Plan(new CuttingPlanRequest(plate));
+        var result = CuttingPlanService.Plan(CuttingPlanRequest.ForPlate(plate));
 
         Assert.Equal(CuttingPlanStatus.UnsupportedGeometry, result.Status);
         var finding = Assert.Single(result.Findings);
@@ -177,7 +177,7 @@ public class CuttingDependencyTests
         plate.Parts.Add(host);
         plate.Parts.Add(inner);
 
-        var snapshot = CuttingPlanService.Capture(new CuttingPlanRequest(plate));
+        var snapshot = CuttingPlanService.Capture(CuttingPlanRequest.ForPlate(plate));
 
         Assert.Null(snapshot.Findings.FirstOrDefault()?.Message);
         Assert.Empty(snapshot.Dependencies.PrerequisitesOf(0));
diff --git a/OpenNest.Tests/CuttingPlanning/CuttingPlanCommitTests.cs b/OpenNest.Tests/CuttingPlanning/CuttingPlanCommitTests.cs
index 46e4f0d..7560e56 100644
--- a/OpenNest.Tests/CuttingPlanning/CuttingPlanCommitTests.cs
+++ b/OpenNest.Tests/CuttingPlanning/CuttingPlanCommitTests.cs
@@ -21,7 +21,7 @@ public class CuttingPlanCommitTests
         Assert.Contains(PostVerificationAnalyzer.Analyze(nest, Vector.Zero).Findings,
             f => f.Kind == PostVerificationKind.RapidCrossing);
 
-        var result = CuttingPlanService.Plan(new CuttingPlanRequest(plate));
+        var result = CuttingPlanService.Plan(CuttingPlanRequest.ForPlate(plate));
         Assert.Equal(CuttingPlanStatus.Ready, result.Status);
         Assert.Equal(parts, plate.Parts); // Planning never mutates.
         var commit = CuttingPlanService.Apply([result]);
@@ -53,7 +53,7 @@ public class CuttingPlanCommitTests
         // capture neither stales the plan nor leaks into what is installed.
         var parameters = ExplicitContourTests.Parameters();
         var length = ((LineLeadIn)parameters.ExternalLeadIn).Length;
-        var result = CuttingPlanService.Plan(new CuttingPlanRequest(plate, confirmedParameters: parameters));
+        var result = CuttingPlanService.Plan(CuttingPlanRequest.ForPlate(plate, confirmedParameters: parameters));
         Assert.Equal(CuttingPlanStatus.Ready, result.Status);
         var proposal = Assert.Single(result.ProposedOrder);
         Assert.True(proposal.IsRegenerated);
@@ -104,7 +104,7 @@ public class CuttingPlanCommitTests
         var cutOff = new CutOff(new Vector(30, 0), CutOffAxis.Vertical);
         plate.CutOffs.Add(cutOff);
         plate.CuttingParameters = new CuttingParameters();
-        var result = CuttingPlanService.Plan(new CuttingPlanRequest(plate));
+        var result = CuttingPlanService.Plan(CuttingPlanRequest.ForPlate(plate));
         Assert.Equal(CuttingPlanStatus.Ready, result.Status);
         switch (change)
         {
@@ -149,7 +149,7 @@ public class CuttingPlanCommitTests
     public void Apply_MalformedLiveProgram_IsStaleInsteadOfThrowing()
     {
         var (_, plate, parts) = FixedPlate();
-        var result = CuttingPlanService.Plan(new CuttingPlanRequest(plate));
+        var result = CuttingPlanService.Plan(CuttingPlanRequest.ForPlate(plate));
         Assert.Equal(CuttingPlanStatus.Ready, result.Status);
         parts[1].Program.Codes = null!;
         var events = Watch(plate);
@@ -194,8 +194,8 @@ public class CuttingPlanCommitTests
         fixedPlate.Parts.Add(shared);
         var results = new[]
         {
-            CuttingPlanService.Plan(new CuttingPlanRequest(regenerated, confirmedParameters: parameters)),
-            CuttingPlanService.Plan(new CuttingPlanRequest(fixedPlate))
+            CuttingPlanService.Plan(CuttingPlanRequest.ForPlate(regenerated, confirmedParameters: parameters)),
+            CuttingPlanService.Plan(CuttingPlanRequest.ForPlate(fixedPlate))
         };
         Assert.All(results, r => Assert.Equal(CuttingPlanStatus.Ready, r.Status));
         Assert.True(results[0].ProposedOrder[0].IsRegenerated);
@@ -229,8 +229,8 @@ public class CuttingPlanCommitTests
         var (_, second, secondParts) = FixedPlate();
         var results = new[]
         {
-            CuttingPlanService.Plan(new CuttingPlanRequest(first)),
-            CuttingPlanService.Plan(new CuttingPlanRequest(second))
+            CuttingPlanService.Plan(CuttingPlanRequest.ForPlate(first)),
+            CuttingPlanService.Plan(CuttingPlanRequest.ForPlate(second))
         };
         secondParts[0].LeadInsLocked = true;
         var firstState = PlateCuttingState.Capture(first);
@@ -253,9 +253,9 @@ public class CuttingPlanCommitTests
         var (_, third, thirdPart, thirdParameters) = RegeneratedPlate(Vector.Zero);
         var results = new[]
         {
-            CuttingPlanService.Plan(new CuttingPlanRequest(first)),
-            CuttingPlanService.Plan(new CuttingPlanRequest(second, confirmedParameters: parameters)),
-            CuttingPlanService.Plan(new CuttingPlanRequest(third, confirmedParameters: thirdParameters))
+            CuttingPlanService.Plan(CuttingPlanRequest.ForPlate(first)),
+            CuttingPlanService.Plan(CuttingPlanRequest.ForPlate(second, confirmedParameters: parameters)),
+            CuttingPlanService.Plan(CuttingPlanRequest.ForPlate(third, confirmedParameters: thirdParameters))
         };
         Assert.All(results, r => Assert.Equal(CuttingPlanStatus.Ready, r.Status));
         var states = new[] { first, second, third }.Select(p => PlateCuttingState.Capture(p)).ToArray();
@@ -287,7 +287,7 @@ public class CuttingPlanCommitTests
     public void Apply_CancelledBeforeCommit_ChangesNothing()
     {
         var (_, plate, parts) = FixedPlate();
-        var result = CuttingPlanService.Plan(new CuttingPlanRequest(plate));
+        var result = CuttingPlanService.Plan(CuttingPlanRequest.ForPlate(plate));
         var state = PlateCuttingState.Capture(plate);
         var events = Watch(plate);
         using var cancel = new CancellationTokenSource();
@@ -308,8 +308,8 @@ public class CuttingPlanCommitTests
         var (_, second, secondParts) = FixedPlate();
         var results = new[]
         {
-            CuttingPlanService.Plan(new CuttingPlanRequest(first)),
-            CuttingPlanService.Plan(new CuttingPlanRequest(second))
+            CuttingPlanService.Plan(CuttingPlanRequest.ForPlate(first)),
+            CuttingPlanService.Plan(CuttingPlanRequest.ForPlate(second))
         };
         var failure = new InvalidOperationException("view refresh");
         var seen = new List<string>();
@@ -339,8 +339,8 @@ public class CuttingPlanCommitTests
         CuttingPlanResult[] results = fault switch
         {
             "detached" => [CuttingPlanService.Plan(new CuttingPlanRequest(parts))],
-            "not-ready" => [CuttingPlanService.Plan(new CuttingPlanRequest(plate, preservePartOrder: true))],
-            "duplicate" => Enumerable.Repeat(CuttingPlanService.Plan(new CuttingPlanRequest(plate)), 2).ToArray(),
+            "not-ready" => [CuttingPlanService.Plan(CuttingPlanRequest.ForPlate(plate, preservePartOrder: true))],
+            "duplicate" => Enumerable.Repeat(CuttingPlanService.Plan(CuttingPlanRequest.ForPlate(plate)), 2).ToArray(),
             _ => []
         };
         if (fault == "detached")
@@ -356,6 +356,14 @@ public class CuttingPlanCommitTests
         Assert.Equal((0, 0, 0), events());
     }
 
+    [Fact]
+    public void Request_NullDetachedListStaysUnambiguousAndInvalid()
+    {
+        // A plate overload of the constructor made this existing call ambiguous (CS0121).
+        Assert.Equal(CuttingPlanStatus.InvalidInput, CuttingPlanService.Plan(new CuttingPlanRequest(null)).Status);
+        Assert.Equal(CuttingPlanStatus.InvalidInput, CuttingPlanService.Plan(CuttingPlanRequest.ForPlate(null)).Status);
+    }
+
     [Fact]
     public void Apply_AllPlatesWithEmptySentinel_KeepsSentinelAndPlateList()
     {
@@ -370,7 +378,7 @@ public class CuttingPlanCommitTests
         var listChanges = 0;
         manager.PlateListChanged += (_, _) => listChanges++;
         var sentinelEvents = Watch(sentinel);
-        var results = nest.Plates.ToArray().Select(p => CuttingPlanService.Plan(new CuttingPlanRequest(p))).ToArray();
+        var results = nest.Plates.ToArray().Select(p => CuttingPlanService.Plan(CuttingPlanRequest.ForPlate(p))).ToArray();
         Assert.All(results, r => Assert.Equal(CuttingPlanStatus.Ready, r.Status));
         Assert.Empty(results[1].ProposedOrder);
 
diff --git a/docs/cutting-planner.md b/docs/cutting-planner.md
index c33fd6e..e20674b 100644
--- a/docs/cutting-planner.md
+++ b/docs/cutting-planner.md
@@ -15,15 +15,15 @@ programs and settings are stable. Pass that snapshot to `Plan` on a worker;
 defaults to `Vector.Zero`, not a discovered controller position.
 
 ```csharp
-var request = new CuttingPlanRequest(plate, startPoint: start,
+var request = CuttingPlanRequest.ForPlate(plate, startPoint: start,
     confirmedParameters: parameters, expansionBudget: 20000,
     maxEntries: 16, preservePartOrder: false);
 var snapshot = CuttingPlanService.Capture(request, cancellationToken);
 var result = CuttingPlanService.Plan(snapshot, cancellationToken);
 ```
 
-- A plate-scoped request plans the plate's current parts and records its exact
-  state for `Apply`. A detached part list (`new CuttingPlanRequest(parts, ...)`)
+- A plate-scoped request (`CuttingPlanRequest.ForPlate`) plans the plate's current
+  parts and records its exact state for `Apply`. A detached part list (`new CuttingPlanRequest(parts, ...)`)
   plans the same way but can never be applied. An empty plate is a Ready no-op.
 - Omitting `confirmedParameters` preserves the original fixed-program contract:
   locked and unlocked programs stay fixed; only whole-part order may change.