--- scripts/ui/equip_window.gd
+++ scripts/ui/equip_window.gd
@@ -25,8 +25,28 @@ static var _portraits: Dictionary = {}
 
 
 ## hud.gd hook: builds the equipment window into its body. Returns true (the old list is not built).
+static var _sig := ""
+
+
+## What the window shows; the body is rebuilt only when this changes. PlayerState.changed fires on every HP / SP
+## tick in combat, and a rebuild between mouse-down and mouse-up swallowed clicks (owner bug 2026-09-30: the 3D
+## button "did nothing").
+static func signature() -> String:
+	var ps = PlayerState
+	var br := ""
+	if load("res://scripts/ui/v2_ui.gd").on() and ps.ch != null:
+		br = str(load("res://scripts/server/combat_v2.gd").battle_rating(ps.ch))
+	return JSON.stringify([ps.equipment, str(ps.job), show_3d, int(ps.base_lv), int(ps.job_lv), ps.stats, str(ps.char_name),
+		ps.max_hp(), ps.max_sp(), ps.weight(), ps.max_weight(), ps.status_atk() + ps.equip_bonus("batk"), ps.weapon_atk() + ps.refine_atk(),
+		ps.hard_def(), ps.soft_def(), ps.hit(), ps.flee(), ps.crit_rate(), ps.aspd(), br])
+
+
 static func fill(hud) -> bool:
 	var body: VBoxContainer = hud.bodies["equip"]
+	var sig := signature()
+	if sig == _sig and body.get_child_count() > 0:
+		return true
+	_sig = sig
 	if preview and is_instance_valid(preview) and preview.get_parent():
 		preview.get_parent().remove_child(preview)
 	hud._clear(body)