From ae88c34361d445749c85f42571afbbbde6b82826 Mon Sep 17 00:00:00 2001
From: AJ Isaacs <ajisaacs27@gmail.com>
Date: Fri, 20 Mar 2026 14:43:45 -0400
Subject: [PATCH] fix: prioritize width-fitting candidates in PairFiller strip
 mode

In strip mode, build candidate list entirely from pairs whose
ShortestSide fits the narrow work area dimension, sorted by
estimated tile count. Previously, the top-50 utilization cut
ran first, excluding good strip candidates like #183.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
---
 OpenNest.Engine/Fill/PairFiller.cs | 23 +++++++++--------------
 1 file changed, 9 insertions(+), 14 deletions(-)

diff --git a/OpenNest.Engine/Fill/PairFiller.cs b/OpenNest.Engine/Fill/PairFiller.cs
index ba620b6..18dc1c6 100644
--- a/OpenNest.Engine/Fill/PairFiller.cs
+++ b/OpenNest.Engine/Fill/PairFiller.cs
@@ -168,35 +168,30 @@ namespace OpenNest.Engine.Fill
         private List<BestFitResult> SelectPairCandidates(List<BestFitResult> bestFits, Box workArea)
         {
             var kept = bestFits.Where(r => r.Keep).ToList();
-            var top = kept.Take(MaxTopCandidates).ToList();
 
             var workShortSide = System.Math.Min(workArea.Width, workArea.Length);
             var plateShortSide = System.Math.Min(plateSize.Width, plateSize.Length);
 
             if (workShortSide < plateShortSide * 0.5)
             {
-                var stripCandidates = bestFits
+                // Strip mode: prioritize candidates that fit the narrow dimension.
+                var stripCandidates = kept
                     .Where(r => r.ShortestSide <= workShortSide + Tolerance.Epsilon
                              && r.Utilization >= MinStripUtilization)
-                    .OrderByDescending(r => r.Utilization);
+                    .ToList();
 
-                var existing = new HashSet<BestFitResult>(top);
+                SortByEstimatedCount(stripCandidates, workArea);
 
-                foreach (var r in stripCandidates)
-                {
-                    if (top.Count >= MaxStripCandidates)
-                        break;
-
-                    if (existing.Add(r))
-                        top.Add(r);
-                }
+                var top = stripCandidates.Take(MaxStripCandidates).ToList();
 
                 Debug.WriteLine($"[PairFiller] Strip mode: {top.Count} candidates (shortSide <= {workShortSide:F1})");
+                return top;
             }
 
-            SortByEstimatedCount(top, workArea);
+            var result = kept.Take(MaxTopCandidates).ToList();
+            SortByEstimatedCount(result, workArea);
 
-            return top;
+            return result;
         }
 
         private void SortByEstimatedCount(List<BestFitResult> candidates, Box workArea)