From a55850c981f2ee39b3c47c7fe0b0fef13570f311 Mon Sep 17 00:00:00 2001
From: Mitchell Hashimoto <m@mitchellh.com>
Date: Thu, 9 Jul 2026 20:58:14 -0700
Subject: [PATCH] terminal: use previous page width for cursor cells

cursorCellEndOfPrev moved its pin to the previous row but then set the
column from the desired screen width. If incomplete reflow left that
previous page narrower, resolving the cell used an out-of-bounds column
and panicked in runtime safety builds.

Set the column from the page reached by the cursor pin so the returned
cell is always the actual final cell of that row.
---
 src/terminal/Screen.zig | 23 ++++++++++++++++++++++-
 1 file changed, 22 insertions(+), 1 deletion(-)

diff --git a/src/terminal/Screen.zig b/src/terminal/Screen.zig
index eb5e4cf52..ec4ad24d9 100644
--- a/src/terminal/Screen.zig
+++ b/src/terminal/Screen.zig
@@ -651,7 +651,7 @@ pub fn cursorCellEndOfPrev(self: *Screen) *pagepkg.Cell {
     assert(self.cursor.y > 0);
 
     var page_pin = self.cursor.page_pin.up(1).?;
-    page_pin.x = self.pages.cols - 1;
+    page_pin.x = page_pin.node.cols() - 1;
     const page_rac = page_pin.rowAndCell();
     return page_rac.cell;
 }
@@ -4223,6 +4223,27 @@ test "Screen eraseRows active partial" {
     }
 }
 
+test "Screen: cursorCellEndOfPrev across mixed-width pages" {
+    const testing = std.testing;
+    var s = try init(testing.allocator, .{
+        .cols = 4,
+        .rows = 2,
+        .max_scrollback = 0,
+    });
+    defer s.deinit();
+
+    try s.testWriteString("ABCDE");
+    const first = s.pages.pages.first.?;
+    try s.pages.split(.{ .node = first, .y = 1 });
+    s.cursorReload();
+    const second = first.next.?;
+    first.page().size.cols = 2;
+
+    try testing.expectEqual(second, s.cursor.page_pin.node);
+    const expected = (Pin{ .node = first, .x = 1 }).rowAndCell().cell;
+    try testing.expectEqual(expected, s.cursorCellEndOfPrev());
+}
+
 test "Screen: cursorDown across pages preserves style" {
     const testing = std.testing;
     const alloc = testing.allocator;