diff --git a/control.c b/control.c
index 7f76ff9e3..c3bb82b01 100644
--- a/control.c
+++ b/control.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: control.c,v 1.65 2026/08/04 11:18:22 nicm Exp $ */
+/* $OpenBSD: control.c,v 1.66 2026/08/18 07:43:44 nicm Exp $ */
 
 /*
  * Copyright (c) 2012 Nicholas Marriott <nicholas.marriott@gmail.com>
@@ -388,6 +388,25 @@ control_pause_pane(struct client *c, struct window_pane *wp)
 	}
 }
 
+/*
+ * Reset a pane after its buffer has been replaced: drop any output still
+ * queued from the old buffer and start again from the pane's own offset.
+ */
+void
+control_reset_pane(struct client *c, struct window_pane *wp)
+{
+	struct control_pane	*cp;
+
+	if (c->control_state == NULL)
+		return;
+	cp = control_get_pane(c, wp);
+	if (cp == NULL)
+		return;
+	control_discard_pane(c, cp);
+	memcpy(&cp->offset, &wp->offset, sizeof cp->offset);
+	memcpy(&cp->queued, &wp->offset, sizeof cp->queued);
+}
+
 /* Write an already-formatted line, queueing it behind %output if needed. */
 static void
 control_write_line(struct client *c, char *line)
diff --git a/spawn.c b/spawn.c
index 6379e01af..9e162217f 100644
--- a/spawn.c
+++ b/spawn.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: spawn.c,v 1.50 2026/07/23 09:38:27 nicm Exp $ */
+/* $OpenBSD: spawn.c,v 1.51 2026/08/18 07:43:44 nicm Exp $ */
 
 /*
  * Copyright (c) 2019 Nicholas Marriott <nicholas.marriott@gmail.com>
@@ -245,7 +245,7 @@ struct window_pane *
 spawn_pane(struct spawn_context *sc, char **cause)
 {
 	struct cmdq_item	 *item = sc->item;
-	struct client		 *c;
+	struct client		 *c, *loop;
 	struct session		 *s = sc->s;
 	struct session		 *ts;
 	struct window		 *w = sc->wl->window;
@@ -333,6 +333,20 @@ spawn_pane(struct spawn_context *sc, char **cause)
 			input_free(sc->wp0->ictx);
 			sc->wp0->ictx = NULL;
 		}
+
+		/*
+		 * The old buffer is gone and the new one starts empty, so
+		 * offsets into the old buffer no longer mean anything. Reset
+		 * them, and drop output control clients still had queued.
+		 */
+		sc->wp0->offset.used = 0;
+		sc->wp0->base_offset = 0;
+		sc->wp0->pipe_offset.used = 0;
+		TAILQ_FOREACH(loop, &clients, entry) {
+			if (loop->flags & CLIENT_CONTROL)
+				control_reset_pane(loop, sc->wp0);
+		}
+
 		new_wp = sc->wp0;
 		new_wp->flags &= ~(PANE_STATUSREADY|PANE_STATUSDRAWN);
 	} else {
diff --git a/tmux.h b/tmux.h
index 11d9e3d4d..ea03cb463 100644
--- a/tmux.h
+++ b/tmux.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: tmux.h,v 1.1425 2026/08/17 20:04:00 nicm Exp $ */
+/* $OpenBSD: tmux.h,v 1.1426 2026/08/18 07:43:44 nicm Exp $ */
 
 /*
  * Copyright (c) 2007 Nicholas Marriott <nicholas.marriott@gmail.com>
@@ -3986,6 +3986,7 @@ void	control_set_pane_on(struct client *, struct window_pane *);
 void	control_set_pane_off(struct client *, struct window_pane *);
 void	control_continue_pane(struct client *, struct window_pane *);
 void	control_pause_pane(struct client *, struct window_pane *);
+void	control_reset_pane(struct client *, struct window_pane *);
 void	control_set_window_size(struct client *, u_int, u_int, u_int);
 int	control_get_window_size(struct client *, u_int, u_int *, u_int *);
 void	control_clear_window_size(struct client *, u_int);