Add -B to new-pane to select the floating pane border.

usr.bin/tmux/cmd-split-window.c

@@ -1,4 +1,4 @@
-/* $OpenBSD: cmd-split-window.c,v 1.133 2026/06/13 18:30:16 nicm Exp $ */
+/* $OpenBSD: cmd-split-window.c,v 1.134 2026/06/15 09:21:40 nicm Exp $ */
 
 /*
  * Copyright (c) 2009 Nicholas Marriott <nicholas.marriott@gmail.com>
@@ -39,9 +39,10 @@ const struct cmd_entry cmd_new_pane_entry = {
 	.name = "new-pane",
 	.alias = "newp",
 
-	.args = { "bc:de:EfF:hIkl:Lm:p:PR:s:S:t:T:vWx:X:y:Y:Z", 0, -1, NULL },
-	.usage = "[-bdefhIklPvWZ] [-c start-directory] [-e environment] "
-		 "[-F format] [-l size] [-m message] [-p percentage] "
+	.args = { "bB:c:de:EfF:hIkl:Lm:p:PR:s:S:t:T:vWx:X:y:Y:Z", 0, -1, NULL },
+	.usage = "[-bdefhIklPvWZ] [-B border-lines] "
+		  "[-c start-directory] [-e environment] "
+		  "[-F format] [-l size] [-m message] [-p percentage] "
 		 "[-s style] [-S active-border-style] "
 		 "[-R inactive-border-style] [-T title] [-x width] [-y height] "
 		 "[-X x-position] [-Y y-position] " CMD_TARGET_PANE_USAGE " "
@@ -85,9 +86,11 @@ cmd_split_window_exec(struct cmd *self, struct cmdq_item *item)
 	struct layout_cell	*lc = NULL;
 	struct cmd_find_state	 fs;
 	int			 input, empty, is_floating, flags = 0;
-	const char		*template, *style;
+	const char		*template, *style, *value;
 	char			*cause = NULL, *cp, *title;
+	struct options_entry	*oe;
 	struct args_value	*av;
+	enum pane_lines		 lines;
 	u_int			 count = args_count(args);
 
 	if (cmd_get_entry(self) == &cmd_new_pane_entry)
@@ -188,6 +191,19 @@ cmd_split_window_exec(struct cmd *self, struct cmdq_item *item)
 			return (CMD_RETURN_ERROR);
 		}
 	}
+	value = args_get(args, 'B');
+	if (value != NULL) {
+		oe = options_get(new_wp->options, "pane-border-lines");
+		lines = options_find_choice(options_table_entry(oe), value,
+		    &cause);
+		if (cause != NULL) {
+			cmdq_error(item, "pane-border-lines %s", cause);
+			free(cause);
+			return (CMD_RETURN_ERROR);
+		}
+		options_set_number(new_wp->options, "pane-border-lines",
+		    lines);
+	}
 	if (args_has(args, 'k') || args_has(args, 'm')) {
 		options_set_number(new_wp->options, "remain-on-exit", 3);
 		if (args_has(args, 'm')) {

usr.bin/tmux/options-table.c

@@ -1,4 +1,4 @@
-/* $OpenBSD: options-table.c,v 1.216 2026/06/15 08:16:05 nicm Exp $ */
+/* $OpenBSD: options-table.c,v 1.217 2026/06/15 09:21:40 nicm Exp $ */
 
 /*
  * Copyright (c) 2011 Nicholas Marriott <nicholas.marriott@gmail.com>
@@ -1365,7 +1365,7 @@ const struct options_table_entry options_table[] = {
 
 	{ .name = "pane-border-lines",
 	  .type = OPTIONS_TABLE_CHOICE,
-	  .scope = OPTIONS_TABLE_WINDOW,
+	  .scope = OPTIONS_TABLE_WINDOW|OPTIONS_TABLE_PANE,
 	  .choices = options_table_pane_border_lines_list,
 	  .default_num = PANE_LINES_SINGLE,
 	  .text = "Type of characters used to draw pane border lines. Some of "

usr.bin/tmux/screen-redraw.c

@@ -1,4 +1,4 @@
-/* $OpenBSD: screen-redraw.c,v 1.136 2026/06/15 08:16:05 nicm Exp $ */
+/* $OpenBSD: screen-redraw.c,v 1.137 2026/06/15 09:21:40 nicm Exp $ */
 
 /*
  * Copyright (c) 2007 Nicholas Marriott <nicholas.marriott@gmail.com>
@@ -1003,6 +1003,7 @@ screen_redraw_draw_borders_cell(struct screen_redraw_ctx *ctx, u_int i, u_int j)
 	struct format_tree	*ft;
 	struct window_pane	*wp, *active = server_client_get_pane(c);
 	struct grid_cell	 gc;
+	enum pane_lines		 pane_lines;
 	u_int			 cell_type;
 	u_int			 x = ctx->ox + i, y = ctx->oy + j;
 	int			 isolates;
@@ -1034,7 +1035,11 @@ screen_redraw_draw_borders_cell(struct screen_redraw_ctx *ctx, u_int i, u_int j)
 		    screen_redraw_check_is(ctx, x, y, marked_pane.wp))
 			gc.attr ^= GRID_ATTR_REVERSE;
 	}
-	screen_redraw_border_set(w, wp, ctx->pane_lines, cell_type, &gc);
+	if (wp == NULL)
+		pane_lines = ctx->pane_lines;
+	else
+		pane_lines = window_pane_get_pane_lines(wp);
+	screen_redraw_border_set(w, wp, pane_lines, cell_type, &gc);
 
 	if (cell_type == CELL_TOPBOTTOM &&
 	    (c->flags & CLIENT_UTF8) &&

usr.bin/tmux/tmux.1

@@ -1,4 +1,4 @@
-.\" $OpenBSD: tmux.1,v 1.1089 2026/06/15 08:16:05 nicm Exp $
+.\" $OpenBSD: tmux.1,v 1.1090 2026/06/15 09:21:40 nicm Exp $
 .\"
 .\" Copyright (c) 2007 Nicholas Marriott <nicholas.marriott@gmail.com>
 .\"
@@ -3490,6 +3490,7 @@ but a different format may be specified with
 .Tg newp
 .It Xo Ic new\-pane
 .Op Fl bdefhIkPvWZ
+.Op Fl B Ar border\-lines
 .Op Fl c Ar start\-directory
 .Op Fl e Ar environment
 .Op Fl F Ar format
@@ -3521,6 +3522,9 @@ sets the border style when the pane is inactive (see
 .Sx STYLES ) .
 .Fl T
 sets the pane title.
+.Fl B
+sets the pane border lines for floating panes; see
+.Ic pane\-border\-lines .
 .Pp
 .Fl h
 does a horizontal split and

usr.bin/tmux/tmux.h

@@ -1,4 +1,4 @@
-/* $OpenBSD: tmux.h,v 1.1351 2026/06/15 08:16:05 nicm Exp $ */
+/* $OpenBSD: tmux.h,v 1.1352 2026/06/15 09:21:40 nicm Exp $ */
 
 /*
  * Copyright (c) 2007 Nicholas Marriott <nicholas.marriott@gmail.com>
@@ -3474,6 +3474,7 @@ int		 window_pane_get_bg_control_client(struct window_pane *);
 int		 window_get_bg_client(struct window_pane *);
 enum client_theme window_pane_get_theme(struct window_pane *);
 void		 window_pane_send_theme_update(struct window_pane *);
+enum pane_lines	 window_pane_get_pane_lines(struct window_pane *);
 int		 window_get_pane_status(struct window *);
 int		 window_pane_get_pane_status(struct window_pane *);
 struct style_range *window_pane_status_get_range(struct window_pane *, u_int,

usr.bin/tmux/window.c

@@ -1,4 +1,4 @@
-/* $OpenBSD: window.c,v 1.337 2026/06/15 08:16:05 nicm Exp $ */
+/* $OpenBSD: window.c,v 1.338 2026/06/15 09:21:40 nicm Exp $ */
 
 /*
  * Copyright (c) 2007 Nicholas Marriott <nicholas.marriott@gmail.com>
@@ -2148,6 +2148,18 @@ window_pane_status_get_range(struct window_pane *wp, u_int x, u_int y)
 	return (style_ranges_get_range(srs, x - wp->xoff - 2));
 }
 
+enum pane_lines
+window_pane_get_pane_lines(struct window_pane *wp)
+{
+	struct options	*oo;
+
+	if (!window_pane_is_floating(wp))
+		oo = wp->window->options;
+	else
+		oo = wp->options;
+	return (options_get_number(oo, "pane-border-lines"));
+}
+
 int
 window_get_pane_status(struct window *w)
 {