diff --git a/src/ui/windows/console_tab.cpp b/src/ui/windows/console_tab.cpp
index d594354..118fdad 100644
--- a/src/ui/windows/console_tab.cpp
+++ b/src/ui/windows/console_tab.cpp
@@ -836,6 +836,14 @@ void ConsoleTab::drawVisibleLines(float padX, float lineHeight, bool hasTextFilt
     // mid-draw. -1 = none.
     int pendingFoldToggle = -1;
 
+    // CRT scanline parity is a true per-visual-row counter (each drawn sub-row = one row).
+    // Deriving it from cumulativeY/lineHeight drifted (cumulativeY includes the inter-line
+    // gap) and skipped rows, breaking the alternation. Seed it with the sub-row ordinal of
+    // the first on-screen line so the shading stays stable across scrolling.
+    int scanRowOrdinal = 0;
+    for (int k = 0; k < first_visible && k < static_cast<int>(layout_.segments.size()); k++)
+        scanRowOrdinal += static_cast<int>(layout_.segments[k].size());
+
     int last_rendered_vi = first_visible - 1;
     for (int vi = first_visible; vi < visible_count; vi++) {
         if (vi < static_cast<int>(layout_.cumulativeY.size()) &&
@@ -917,9 +925,9 @@ void ConsoleTab::drawVisibleLines(float padX, float lineHeight, bool hasTextFilt
             const char* segEnd   = line.text.c_str() + seg.byteEnd;
 
             if (s_scanline_enabled && lineHeight > 0.0f) {
-                int rowIndex = static_cast<int>(std::floor((layout_.cumulativeY[vi] + seg.yOffset) / lineHeight + 0.5f));
-                scanline_rows_.push_back({rowY, rowY + seg.height, rowIndex});
+                scanline_rows_.push_back({rowY, rowY + seg.height, scanRowOrdinal});
             }
+            ++scanRowOrdinal;  // one per visual sub-row, so parity always alternates
 
             // Selection highlight for this sub-row
             if (lineSelected && selByteStart < seg.byteEnd && selByteEnd > seg.byteStart) {