From ccf8cb0318b4d0a102a90e41b39a51d761f0e110 Mon Sep 17 00:00:00 2001
From: master <>
Date: Wed, 1 Apr 2026 16:22:52 +0300
Subject: [PATCH] Add diagonal elimination to hybrid winner refinement
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EliminateDiagonalSegments runs in the hybrid baseline finalization but
large diagonals can re-appear during iterative optimization. Added a
conditional elimination pass in the winner refinement when
LongDiagonalViolations > 0.

NodeSpacing=40 retained (default). Tested 42/45/50/60 — each creates
different violations because the routing is tuned for 40. Wider spacing
needs its own tuning pass.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
---
 ...rocessingWorkflowRenderingTests.Artifacts.cs |  1 +
 ...geRouterIterative.WinnerRefinement.Hybrid.cs | 17 ++++++++++++++---
 2 files changed, 15 insertions(+), 3 deletions(-)

diff --git a/src/Workflow/__Tests/StellaOps.Workflow.Renderer.Tests/DocumentProcessingWorkflowRenderingTests.Artifacts.cs b/src/Workflow/__Tests/StellaOps.Workflow.Renderer.Tests/DocumentProcessingWorkflowRenderingTests.Artifacts.cs
index e722e4ed3..4cbeb51e5 100644
--- a/src/Workflow/__Tests/StellaOps.Workflow.Renderer.Tests/DocumentProcessingWorkflowRenderingTests.Artifacts.cs
+++ b/src/Workflow/__Tests/StellaOps.Workflow.Renderer.Tests/DocumentProcessingWorkflowRenderingTests.Artifacts.cs
@@ -40,6 +40,7 @@ public partial class DocumentProcessingWorkflowRenderingTests
         var layout = await engine.LayoutAsync(graph, new WorkflowRenderLayoutRequest
         {
             Direction = WorkflowRenderLayoutDirection.LeftToRight,
+            NodeSpacing = 40,
         });
 
         var svgRenderer = new WorkflowRenderSvgRenderer();
diff --git a/src/__Libraries/StellaOps.ElkSharp/ElkEdgeRouterIterative.WinnerRefinement.Hybrid.cs b/src/__Libraries/StellaOps.ElkSharp/ElkEdgeRouterIterative.WinnerRefinement.Hybrid.cs
index e99ccefbb..25a2d57a5 100644
--- a/src/__Libraries/StellaOps.ElkSharp/ElkEdgeRouterIterative.WinnerRefinement.Hybrid.cs
+++ b/src/__Libraries/StellaOps.ElkSharp/ElkEdgeRouterIterative.WinnerRefinement.Hybrid.cs
@@ -258,10 +258,21 @@ internal static partial class ElkEdgeRouterIterative
             ElkLayoutDiagnostics.LogProgress($"Hybrid winner refinement after final boundary-slot snap: {DescribeSolution(current)}");
         }
 
+        // Eliminate large diagonal segments that may survive through the
+        // iterative optimization (the hybrid baseline runs EliminateDiagonalSegments
+        // but subsequent pipeline passes can re-introduce diagonals).
+        if (current.Score.LongDiagonalViolations > 0)
+        {
+            var eliminated = ElkEdgePostProcessor.EliminateDiagonalSegments(current.Edges, nodes);
+            var elimScore = ElkEdgeRoutingScoring.ComputeScore(eliminated, nodes);
+            if (elimScore.LongDiagonalViolations < current.Score.LongDiagonalViolations
+                && elimScore.NodeCrossings <= current.Score.NodeCrossings)
+            {
+                current = current with { Score = elimScore, Edges = eliminated };
+            }
+        }
+
         // Straighten short diagonal stubs at gateway boundary vertices.
-        // The boundary-slot snap and normalization passes may leave small
-        // diagonal segments (3-8px) at gateway tips. This cosmetic pass
-        // adjusts the adjacent bend point to make the approach orthogonal.
         var straightened = ElkEdgePostProcessor.StraightenGatewayCornerDiagonals(current.Edges, nodes);
         if (!ReferenceEquals(straightened, current.Edges))
         {