From c57e0ded83b7fc4815711a6dfdd8ed7bf6bebc08 Mon Sep 17 00:00:00 2001
From: AJ Isaacs <ajisaacs27@gmail.com>
Date: Tue, 13 Oct 2026 18:15:16 -0400
Subject: [PATCH] fix(diagnostics): keep tiny clamps beyond coarse chords in
 the overlap check

Check Overlaps dismissed a tiny clamp by the part's coarse material bounds
before the fine tolerance-free test ran, but that material is inscribed at
the 0.001 chord tolerance: real material in the sliver beyond a convex arc
(a short arc cap, a rotated crescent) lay outside those bounds and the clamp
read as clear. For clamps below the tolerance the bounds are widened by the
chord tolerance before rejecting.

PM 407f5eb7-329f-41e4-947e-64ad52aa4034 (review s6-delta3-review.md)
---
 .../Diagnostics/PlateOverlapAnalyzer.cs       |  7 +++--
 .../PlateOverlapAnalyzerClampZoneTests.cs     | 26 +++++++++++++++++++
 2 files changed, 31 insertions(+), 2 deletions(-)

diff --git a/OpenNest.Core/Diagnostics/PlateOverlapAnalyzer.cs b/OpenNest.Core/Diagnostics/PlateOverlapAnalyzer.cs
index 7accabc..a602a97 100644
--- a/OpenNest.Core/Diagnostics/PlateOverlapAnalyzer.cs
+++ b/OpenNest.Core/Diagnostics/PlateOverlapAnalyzer.cs
@@ -270,8 +270,11 @@ public static class PlateOverlapAnalyzer
             {
                 cancellationToken.ThrowIfCancellationRequested();
                 var zone = clamp.Bounds;
-                if (partBounds.Right <= zone.Left || zone.Right <= partBounds.Left
-                    || partBounds.Top <= zone.Bottom || zone.Top <= partBounds.Bottom)
+                // The prepared material is inscribed at ChordTolerance, so real material can
+                // reach that far past its bounds; a tiny clamp there must still be checked.
+                var reach = KeepOutOverlap.NeedsToleranceFreeTest(zone) ? ChordTolerance : 0;
+                if (partBounds.Right + reach <= zone.Left || zone.Right <= partBounds.Left - reach
+                    || partBounds.Top + reach <= zone.Bottom || zone.Top <= partBounds.Bottom - reach)
                     continue;
                 try
                 {
diff --git a/OpenNest.Tests/Diagnostics/PlateOverlapAnalyzerClampZoneTests.cs b/OpenNest.Tests/Diagnostics/PlateOverlapAnalyzerClampZoneTests.cs
index fab500f..673e3ef 100644
--- a/OpenNest.Tests/Diagnostics/PlateOverlapAnalyzerClampZoneTests.cs
+++ b/OpenNest.Tests/Diagnostics/PlateOverlapAnalyzerClampZoneTests.cs
@@ -282,6 +282,32 @@ public class PlateOverlapAnalyzerClampZoneTests
         Assert.NotEmpty(report.ClampFindings);
     }
 
+    // Delta review 3: a tiny clamp in the sliver beyond a convex arc's 0.001 chords must not
+    // be dismissed by the coarse material bounds before the fine check runs.
+    [Fact]
+    public void TinyClampBeyondCoarseChordsIsReported()
+    {
+        const double r = 0.01, half = 0.04;
+        var dx = r * System.Math.Sin(half);
+        var cy = 20 - r * System.Math.Cos(half);
+        var program = new Program();
+        program.MoveTo(0, 0);
+        program.LineTo(20, 0);
+        program.LineTo(20, 20);
+        program.LineTo(10 + dx, 20);
+        program.ArcTo(10 - dx, 20, 10, cy, RotationType.CCW);
+        program.LineTo(0, 20);
+        program.LineTo(0, 0);
+        // Witness (10, 20.000002) is inside the arc (radius 0.009994 < 0.01) and the zone.
+        var zone = new ClampZone("tiny", new Box(9.999995, 20.000001199840007, 1e-5, 1e-5));
+
+        var report = PlateOverlapAnalyzer.Analyze(PlateOverlapAnalyzer.Capture(
+            new List<Part> { new(new Drawing("cap", program), new Vector(0, 0)) }, new[] { zone }));
+
+        Assert.True(report.IsComplete, string.Join("; ", report.Issues.Select(issue => issue.Message)));
+        Assert.NotEmpty(report.ClampFindings);
+    }
+
     private static string Describe(PlateOverlapReport report) =>
         string.Join(";", report.Pairs.Select(p => $"{p.PartAId}/{p.PartBId}:{p.Area:R}"))
         + "|"