diff --git a/patches/0003-ns-add-buffer-notification-dispatch-and-mode-line-el.patch b/patches/0003-ns-add-buffer-notification-dispatch-and-mode-line-el.patch
index aede7b9..3f2b6d9 100644
--- a/patches/0003-ns-add-buffer-notification-dispatch-and-mode-line-el.patch
+++ b/patches/0003-ns-add-buffer-notification-dispatch-and-mode-line-el.patch
@@ -27,7 +27,7 @@ diff --git a/src/nsterm.m b/src/nsterm.m
 index 8f528bd..7e3d57a 100644
 --- a/src/nsterm.m
 +++ b/src/nsterm.m
-@@ -8718,6 +8718,551 @@ - (NSRect)accessibilityFrame
+@@ -8718,6 +8718,552 @@ - (NSRect)accessibilityFrame
  
  @end
  
@@ -432,17 +432,18 @@ index 8f528bd..7e3d57a 100644
 +      [self ensureTextCache];
 +      if (cachedText && oldPoint > 0)
 +	{
-+	  NSUInteger tlen = [cachedText length];
 +	  NSUInteger oldIdx = [self accessibilityIndexForCharpos:oldPoint];
 +	  NSUInteger newIdx = [self accessibilityIndexForCharpos:point];
-+	  if (oldIdx > tlen) oldIdx = tlen;
-+	  if (newIdx > tlen) newIdx = tlen;
 +
-+	  NSRange oldLine = [cachedText lineRangeForRange:
-+				  NSMakeRange (oldIdx, 0)];
-+	  NSRange newLine = [cachedText lineRangeForRange:
-+				  NSMakeRange (newIdx, 0)];
-+	  if (oldLine.location != newLine.location)
++	  /* Use precomputed lineStartOffsets for O(log L) line lookup.
++	     NSString lineRangeForRange: is O(offset) — it scans from
++	     the start of the string, causing progressive slowdown in
++	     large buffers (O(cursor_position) per redisplay cycle).
++	     lineForAXIndex: binary-searches lineStartOffsets, built
++	     once per cache rebuild in ensureTextCache.  */
++	  NSInteger oldLine = [self lineForAXIndex: oldIdx];
++	  NSInteger newLine = [self lineForAXIndex: newIdx];
++	  if (oldLine != newLine)
 +	    granularity = ns_ax_text_selection_granularity_line;
 +	  else
 +	    {