From fc695b4e8643fa2ec07ff8f8d9351c3c17960811 Mon Sep 17 00:00:00 2001
From: Nicholas Marriott <nicholas.marriott@gmail.com>
Date: Wed, 9 Sep 2026 10:01:32 +0100
Subject: [PATCH] =?UTF-8?q?Test=20for=20v1=20nesting=20limit,=20based=20on?=
 =?UTF-8?q?=20a=20changed=20from=20Afonso=20Janu=C3=A1rio.?=
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---
 regress/layout-nesting-limit.sh | 77 +++++++++++++++++++++++++++++++++
 1 file changed, 77 insertions(+)
 create mode 100644 regress/layout-nesting-limit.sh

diff --git a/regress/layout-nesting-limit.sh b/regress/layout-nesting-limit.sh
new file mode 100644
index 000000000..7d0594d9c
--- /dev/null
+++ b/regress/layout-nesting-limit.sh
@@ -0,0 +1,77 @@
+#!/bin/sh
+
+# Version 1 layouts must reject excessive nesting without losing the session or
+# changing its layout. Check both split types and the depth limit boundary.
+
+PATH=/bin:/usr/bin
+TERM=screen
+export PATH TERM
+
+[ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
+DIR=$(mktemp -d) || exit 1
+TMUX="$TEST_TMUX -S$DIR/socket -f/dev/null"
+
+fail()
+{
+	echo "$*" >&2
+	exit 1
+}
+
+cleanup()
+{
+	$TMUX kill-server 2>/dev/null
+	rm -rf "$DIR"
+}
+trap cleanup 0
+trap 'exit 1' 1 2 15
+
+# Generate a checksum-valid v1 layout with one child in every nested group.
+layout()
+{
+	awk -v depth="$1" -v open="$2" 'BEGIN {
+		closing = (open == "{" ? "}" : "]")
+		body = ""
+		for (i = 0; i < depth; i++)
+			body = body "1x1,0,0" open
+		body = body "1x1,0,0"
+		for (i = 0; i < depth; i++)
+			body = body closing
+
+		ord["0"] = 48; ord["1"] = 49; ord["x"] = 120
+		ord[","] = 44; ord["{"] = 123; ord["}"] = 125
+		ord["["] = 91; ord["]"] = 93
+		csum = 0
+		for (i = 1; i <= length(body); i++) {
+			c = substr(body, i, 1)
+			bit = csum % 2
+			csum = int(csum / 2) + bit * 32768
+			csum = (csum + ord[c]) % 65536
+		}
+		printf "%04x,%s", csum, body
+	}'
+}
+
+$TMUX new-session -d -s deep -x80 -y24 'exec sleep 100' || exit 1
+
+for open in '{' '['; do
+	# A valid checksum and nesting up to the limit must still be accepted.
+	value=$(layout 1000 "$open") || fail "could not generate layout"
+	$TMUX select-layout -t deep "$value" ||
+		fail "layout at the depth limit was rejected ($open)"
+	before=$($TMUX display-message -p -t deep \
+	    '#{pane_id} #{pane_width} #{pane_height} #{window_layout}') || exit 1
+
+	for depth in 1001 1500; do
+		value=$(layout "$depth" "$open") || fail "could not generate layout"
+		$TMUX select-layout -t deep "$value" >/dev/null 2>&1 &&
+			fail "excessive nesting was accepted ($open, $depth)"
+		$TMUX has-session -t deep ||
+			fail "server died on excessive nesting ($open, $depth)"
+		after=$($TMUX display-message -p -t deep \
+		    '#{pane_id} #{pane_width} #{pane_height} #{window_layout}') || exit 1
+		[ "$before" = "$after" ] ||
+			fail "pane or layout changed after rejection ($open, $depth)"
+	done
+done
+
+exit 0