From 195a9cfd8885d631633b414495a1f2540faa2601 Mon Sep 17 00:00:00 2001
From: nicm <nicm>
Date: Thu, 22 Jan 2026 08:55:01 +0000
Subject: [PATCH] When history-limit is changed, apply to existing panes, not
 just new ones. GitHub issue 4705.

---
 grid-view.c   |  4 ++--
 grid.c        |  7 +++++--
 options.c     |  4 ++++
 session.c     | 26 ++++++++++++++++++++++++++
 tmux.1        |  4 +---
 tmux.h        |  3 ++-
 window-copy.c |  5 +++++
 7 files changed, 45 insertions(+), 8 deletions(-)

diff --git a/grid-view.c b/grid-view.c
index 7590ea42..655ec9e4 100644
--- a/grid-view.c
+++ b/grid-view.c
@@ -82,7 +82,7 @@ grid_view_clear_history(struct grid *gd, u_int bg)
 
 	/* Scroll the lines into the history. */
 	for (yy = 0; yy < last; yy++) {
-		grid_collect_history(gd);
+		grid_collect_history(gd, 0);
 		grid_scroll_history(gd, bg);
 	}
 	if (last < gd->sy)
@@ -107,7 +107,7 @@ grid_view_scroll_region_up(struct grid *gd, u_int rupper, u_int rlower,
     u_int bg)
 {
 	if (gd->flags & GRID_HISTORY) {
-		grid_collect_history(gd);
+		grid_collect_history(gd, 0);
 		if (rupper == 0 && rlower == gd->sy - 1)
 			grid_scroll_history(gd, bg);
 		else {
diff --git a/grid.c b/grid.c
index 7ad6770b..92a9ce76 100644
--- a/grid.c
+++ b/grid.c
@@ -375,14 +375,17 @@ grid_trim_history(struct grid *gd, u_int ny)
  * and shift up.
  */
 void
-grid_collect_history(struct grid *gd)
+grid_collect_history(struct grid *gd, int all)
 {
 	u_int	ny;
 
 	if (gd->hsize == 0 || gd->hsize < gd->hlimit)
 		return;
 
-	ny = gd->hlimit / 10;
+	if (all)
+		ny = gd->hsize - gd->hlimit;
+	else
+		ny = gd->hlimit / 10;
 	if (ny < 1)
 		ny = 1;
 	if (ny > gd->hsize)
diff --git a/options.c b/options.c
index 37160b7a..a847ad9c 100644
--- a/options.c
+++ b/options.c
@@ -1252,6 +1252,10 @@ options_push_changes(const char *name)
 		utf8_update_width_cache();
 	if (strcmp(name, "input-buffer-size") == 0)
 		input_set_buffer_size(options_get_number(global_options, name));
+	if (strcmp(name, "history-limit") == 0) {
+		RB_FOREACH(s, sessions, &sessions)
+			session_update_history(s);
+	}
 	RB_FOREACH(s, sessions, &sessions)
 		status_update_cache(s);
 
diff --git a/session.c b/session.c
index 51430678..afa48637 100644
--- a/session.c
+++ b/session.c
@@ -768,3 +768,29 @@ session_theme_changed(struct session *s)
 		}
 	}
 }
+
+/* Update history for all panes. */
+void
+session_update_history(struct session *s)
+{
+	struct winlink		*wl;
+	struct window_pane	*wp;
+	struct grid		*gd;
+	u_int			 limit, osize;
+
+	limit = options_get_number(s->options, "history-limit");
+	RB_FOREACH(wl, winlinks, &s->windows) {
+		TAILQ_FOREACH(wp, &wl->window->panes, entry) {
+			gd = wp->base.grid;
+
+			osize = gd->hsize;
+			gd->hlimit = limit;
+			grid_collect_history(gd, 1);
+
+			if (gd->hsize != osize) {
+				log_debug("%s: %%%u %u -> %u", __func__, wp->id,
+				    osize, gd->hsize);
+			}
+		}
+	}
+}
diff --git a/tmux.1 b/tmux.1
index bf051794..f58511f2 100644
--- a/tmux.1
+++ b/tmux.1
@@ -4583,9 +4583,7 @@ If set to 0, messages and indicators are displayed until a key is pressed.
 .Ar time
 is in milliseconds.
 .It Ic history-limit Ar lines
-Set the maximum number of lines held in window history.
-This setting applies only to new windows - existing window histories are not
-resized and retain the limit at the point they were created.
+Set the maximum number of lines held in pane history.
 .It Ic initial-repeat-time Ar time
 Set the time in milliseconds for the initial repeat when a key is bound with the
 .Fl r
diff --git a/tmux.h b/tmux.h
index e5145b10..74447785 100644
--- a/tmux.h
+++ b/tmux.h
@@ -3002,7 +3002,7 @@ int	 grid_cells_look_equal(const struct grid_cell *,
 struct grid *grid_create(u_int, u_int, u_int);
 void	 grid_destroy(struct grid *);
 int	 grid_compare(struct grid *, struct grid *);
-void	 grid_collect_history(struct grid *);
+void	 grid_collect_history(struct grid *, int);
 void	 grid_remove_history(struct grid *, u_int );
 void	 grid_scroll_history(struct grid *, u_int);
 void	 grid_scroll_history_region(struct grid *, u_int, u_int, u_int);
@@ -3485,6 +3485,7 @@ u_int		 session_group_count(struct session_group *);
 u_int		 session_group_attached_count(struct session_group *);
 void		 session_renumber_windows(struct session *);
 void		 session_theme_changed(struct session *);
+void		 session_update_history(struct session *);
 
 /* utf8.c */
 enum utf8_state	 utf8_towc (const struct utf8_data *, wchar_t *);
diff --git a/window-copy.c b/window-copy.c
index 82c0f47f..04cfe85d 100644
--- a/window-copy.c
+++ b/window-copy.c
@@ -2708,6 +2708,11 @@ window_copy_cmd_refresh_from_pane(struct window_copy_cmd_state *cs)
 	data->backing = window_copy_clone_screen(&wp->base, &data->screen, NULL,
 	    NULL, wme->swp != wme->wp);
 
+	if (data->oy > screen_hsize(data->backing)) {
+		data->cy = 0;
+		data->oy = screen_hsize(data->backing);
+	}
+
 	window_copy_size_changed(wme);
 	return (WINDOW_COPY_CMD_REDRAW);
 }