From 2ec432838050db3b55e7d5fa9ec85ec5f70dc871 Mon Sep 17 00:00:00 2001
From: Michael Grant <mgrant@grant.org>
Date: Mon, 14 Sep 2026 03:09:42 +0100
Subject: [PATCH] Fixed clear erasinng the usable C marker, use beginning of
 buffer in this case, up to D marker.

---
 regress/output-commands.sh |  8 ++++++++
 window-copy.c              | 14 ++++++++++++--
 2 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/regress/output-commands.sh b/regress/output-commands.sh
index bf28be977..11f0fc6fb 100644
--- a/regress/output-commands.sh
+++ b/regress/output-commands.sh
@@ -139,6 +139,14 @@ $TMUX send-keys -t :below.0 -X copy-selection || exit 1
 [ "$($TMUX show-buffer)" = "$(printf 'PID TTY\\n1 pts/0')" ] || exit 1
 $TMUX send-keys -t :below.0 -X cancel || exit 1
 
+$TMUX new-window -d -n clear "printf 'old1\\nold2\\nold3\\nold4\\nold5\\nold6\\n\\033]133;A\\007p\\$ \\033]133;B\\007echo 1; clear; ps\\n\\033]133;C\\0071\\n\\033[H\\033[2JPID TTY\\n1 pts/0\\n\\033]133;D;0\\007separator\\n\\033]133;A\\007p\\$ \\033]133;B\\007'; exec sleep 100" || exit 1
+sleep 1
+$TMUX copy-mode -t :clear || exit 1
+$TMUX send-keys -t :clear.0 C-o || exit 1
+$TMUX send-keys -t :clear.0 -X copy-selection || exit 1
+[ "$($TMUX show-buffer)" = "$(printf 'PID TTY\\n1 pts/0')" ] || exit 1
+$TMUX send-keys -t :clear.0 -X cancel || exit 1
+
 $TMUX new-window -d -n same "printf '\\033]133;A\\007p\\$ \\033]133;B\\007echo\\n\\033]133;C\\007one\\033]133;D;0\\007\\033]133;A\\007p\\$ \\033]133;B\\007'; exec sleep 100" || exit 1
 sleep 1
 $TMUX copy-mode -U -t :same || exit 1
diff --git a/window-copy.c b/window-copy.c
index 4c1a7d8ab..3357765f3 100644
--- a/window-copy.c
+++ b/window-copy.c
@@ -4211,7 +4211,7 @@ window_copy_find_previous_output_range(struct screen *s, u_int cursor_x,
 	void			*buf;
 	u_int			 start_x, start_y, end_x, end_y, y, total;
 	size_t			 len;
-	int			 found = 0, pending = 0;
+	int			 found = 0, have_prompt = 0, pending = 0;
 
 	total = gd->hsize + gd->sy;
 	for (y = 0; y < total && y <= cursor_y; y++) {
@@ -4222,6 +4222,14 @@ window_copy_find_previous_output_range(struct screen *s, u_int cursor_x,
 			start_y = y;
 			pending = 1;
 		}
+		/* The output may have cleared its C marker from the screen. */
+		if (!pending && !have_prompt &&
+		    gl->flags & GRID_LINE_END_OUTPUT &&
+		    (~gl->flags & GRID_LINE_START_PROMPT ||
+		    gl->osc133_data.out_end_col <= gl->osc133_data.prompt_col)) {
+			start_x = start_y = 0;
+			pending = 1;
+		}
 		if (pending && gl->flags & GRID_LINE_END_OUTPUT &&
 		    (y != cursor_y || gl->osc133_data.out_end_col <= cursor_x)) {
 			end_x = gl->osc133_data.out_end_col;
@@ -4238,8 +4246,10 @@ window_copy_find_previous_output_range(struct screen *s, u_int cursor_x,
 			}
 			pending = 0;
 		}
-		if (gl->flags & GRID_LINE_START_PROMPT)
+		if (gl->flags & GRID_LINE_START_PROMPT) {
 			pending = 0;
+			have_prompt = 1;
+		}
 	}
 	return (found);
 }