diff --git a/autoload/save_manager.gd b/autoload/save_manager.gd
index ba5b0f7..b502ebe 100644
--- a/autoload/save_manager.gd
+++ b/autoload/save_manager.gd
@@ -10,6 +10,80 @@ const SimulationTime = preload("res://world/owniverse/simulation_time.gd")
 const STATE_VERSION: String = SimulationTime.STATE_VERSION
 var last_error: String = ""
 var blocked_saves: Dictionary = {}
+var save_directory: String = "user://"
+signal save_completed(filename: String, success: bool, error: String)
+signal saves_drained
+
+# Queue ownership stays on the main thread. The worker only sees its snapshot.
+var _save_thread: Thread
+var _active_filename: String = ""
+var _pending_saves: Dictionary = {}
+
+
+func _process(_delta: float) -> void:
+    if _save_thread != null and not _save_thread.is_alive():
+        _finish_save()
+
+
+func is_saving() -> bool:
+    return _save_thread != null or not _pending_saves.is_empty()
+
+
+func _snapshot(filename: String, password: String, data: Dictionary) -> Dictionary:
+    var payload: Dictionary = data.duplicate(true)
+    payload.format_version = FORMAT_VERSION
+    payload.app_version = str(ProjectSettings.get_setting("application/config/version", ""))
+    return {"filename": filename, "path": save_directory.path_join(filename + ".adventure"), "password": password, "payload": payload,
+        "plaintext": Global.save_plaintext_copy, "speed_limit": Global.SPEED_LIMIT,
+        "stages": Global.CivilizationRules.keys()}
+
+
+## True means queued, not written. Completion is reported by save_completed.
+func request_save(filename: String, password: String, data: Dictionary) -> bool:
+    if blocked_saves.has(filename):
+        return _fail("Save blocked to preserve an unreadable save: " + filename)
+    _pending_saves[filename] = _snapshot(filename, password, data)
+    if _save_thread == null:
+        _start_save()
+    return true
+
+
+func _start_save() -> void:
+    if _pending_saves.is_empty():
+        return
+    _active_filename = _pending_saves.keys()[0]
+    var job: Dictionary = _pending_saves[_active_filename]
+    _pending_saves.erase(_active_filename)
+    _save_thread = Thread.new()
+    var error: Error = _save_thread.start(_write_snapshot.bind(job))
+    if error != OK:
+        _save_thread = null
+        _fail("Cannot start save worker: " + error_string(error))
+        save_completed.emit(_active_filename, false, last_error)
+        _start_save()
+        if not is_saving(): saves_drained.emit()
+
+
+func _finish_save() -> void:
+    var error: String = _save_thread.wait_to_finish()
+    var filename: String = _active_filename
+    _save_thread = null
+    last_error = error
+    if error != "": push_error(error)
+    save_completed.emit(filename, error == "", error)
+    if _save_thread == null: _start_save()
+    if not is_saving(): saves_drained.emit()
+
+
+## Used for application suspension and teardown, when frames may stop arriving.
+func flush_saves() -> void:
+    while is_saving():
+        if _save_thread == null: _start_save()
+        if _save_thread != null: _finish_save()
+
+
+func _exit_tree() -> void:
+    flush_saves()
 
 #region Save Load routines
 
@@ -20,50 +94,56 @@ func _fail(message: String) -> bool:
 
 
 func save_data(filename: String, password: String, data: Dictionary) -> bool:
+    # Synchronous compatibility API must never race an asynchronous writer.
+    flush_saves()
     last_error = ""
     if blocked_saves.has(filename):
         return _fail("Save blocked to preserve an unreadable save: " + filename)
-    var payload: Dictionary = data.duplicate(true)
-    payload.format_version = FORMAT_VERSION
-    payload.app_version = str(ProjectSettings.get_setting("application/config/version", ""))
-    var problem: String = validate_data(payload)
+    var error: String = _write_snapshot(_snapshot(filename, password, data))
+    return _fail(error) if error != "" else true
+
+
+static func _write_snapshot(job: Dictionary) -> String:
+    var payload: Dictionary = job.payload
+    var problem: String = _validate_payload(payload, job.speed_limit, job.stages)
     if problem != "":
-        return _fail("Invalid save: " + problem)
-    var path: String = "user://" + filename + ".adventure"
+        return "Invalid save: " + problem
+    var path: String = job.path
     var temporary: String = path + ".tmp"
-    var file := FileAccess.open_encrypted_with_pass(temporary, FileAccess.WRITE, password)
+    var file := FileAccess.open_encrypted_with_pass(temporary, FileAccess.WRITE, job.password)
     if file == null:
-        return _fail("Cannot write encrypted save: " + temporary)
+        return "Cannot write encrypted save: " + temporary
     file.store_var(payload, false)
     file.close()
     # Check the actual encrypted file, including finalization, before replacing the old save.
-    var verification := FileAccess.open_encrypted_with_pass(temporary, FileAccess.READ, password)
+    var verification := FileAccess.open_encrypted_with_pass(temporary, FileAccess.READ, job.password)
     if verification == null:
-        return _fail("Cannot verify encrypted save: " + temporary)
+        return "Cannot verify encrypted save: " + temporary
     var restored: Variant = verification.get_var(false)
     verification.close()
     if not restored is Dictionary or restored != payload:
-        return _fail("Encrypted save verification failed: " + temporary)
+        return "Encrypted save verification failed: " + temporary
     if DirAccess.rename_absolute(temporary, path) != OK:
-        return _fail("Cannot replace encrypted save: " + path)
-    if Global.save_plaintext_copy:
+        return "Cannot replace encrypted save: " + path
+    if job.plaintext:
         var plain_path: String = path + ".json"
         file = FileAccess.open(plain_path + ".tmp", FileAccess.WRITE)
         if file == null:
-            return _fail("Encrypted save written, but cannot write diagnostic copy: " + plain_path)
+            return "Encrypted save written, but cannot write diagnostic copy: " + plain_path
         file.store_string(JSON.stringify(payload, "  ", true, true) + "\n")
         file.flush()
         var write_error: Error = file.get_error()
         file.close()
         if write_error != OK or DirAccess.rename_absolute(plain_path + ".tmp", plain_path) != OK:
-            return _fail("Encrypted save written, but diagnostic copy failed: " + plain_path)
-    return true
+            return "Encrypted save written, but diagnostic copy failed: " + plain_path
+    return ""
 
 
 func load_data(filename: String, password: String) -> Dictionary:
+    flush_saves()
     last_error = ""
     # Plaintext is diagnostic only: never use it as a fallback.
-    var path: String = "user://" + filename + ".adventure"
+    var path: String = save_directory.path_join(filename + ".adventure")
     if not FileAccess.file_exists(path):
         return {}
     var file := FileAccess.open_encrypted_with_pass(path, FileAccess.READ, password)
@@ -73,6 +153,22 @@ func load_data(filename: String, password: String) -> Dictionary:
         return {}
     var data: Variant = file.get_var(false)
     file.close()
+    # Unsupported formats are archived, never converted or overwritten.
+    # Returning no data lets the stage start a new, saveable session.
+    if data is Dictionary and data.get("format_version") != FORMAT_VERSION:
+        var archive: String = path + ".incompatible.bak"
+        var index: int = 0
+        while FileAccess.file_exists(archive):
+            index += 1
+            archive = path + ".incompatible.bak." + str(index)
+        var error: Error = DirAccess.rename_absolute(path, archive)
+        if error != OK:
+            blocked_saves[filename] = true
+            _fail("Cannot archive incompatible save: " + error_string(error))
+            return {}
+        blocked_saves.erase(filename)
+        push_warning("Incompatible save preserved at " + archive + "; starting a new game.")
+        return {}
     var problem: String = validate_data(data)
     if problem != "":
         blocked_saves[filename] = true
@@ -82,13 +178,13 @@ func load_data(filename: String, password: String) -> Dictionary:
     return data
 
 
-func _number(value: Variant, whole: bool = false, nonnegative: bool = true) -> bool:
+static func _number(value: Variant, whole: bool = false, nonnegative: bool = true) -> bool:
     if not (value is int or value is float) or not is_finite(float(value)):
         return false
     return (not whole or float(value) == floorf(float(value))) and (not nonnegative or value >= 0)
 
 
-func _number_map(value: Variant, whole: bool = false, nonnegative: bool = true) -> bool:
+static func _number_map(value: Variant, whole: bool = false, nonnegative: bool = true) -> bool:
     if not value is Dictionary:
         return false
     for key in value:
@@ -97,7 +193,7 @@ func _number_map(value: Variant, whole: bool = false, nonnegative: bool = true)
     return true
 
 
-func _plain_tree(value: Variant) -> bool:
+static func _plain_tree(value: Variant) -> bool:
     if value is Dictionary:
         for key in value:
             if not (key is String or key is StringName) or not _plain_tree(value[key]):
@@ -113,6 +209,10 @@ func _plain_tree(value: Variant) -> bool:
 
 ## Return a diagnostic path on failure; an empty string means the structure is valid.
 func validate_data(data: Variant) -> String:
+    return _validate_payload(data, Global.SPEED_LIMIT, Global.CivilizationRules.keys())
+
+
+static func _validate_payload(data: Variant, speed_limit: int, stages: Array) -> String:
     if not data is Dictionary or not _plain_tree(data):
         return "save must contain plain finite values"
     if data.get("format_version") != FORMAT_VERSION or not data.get("app_version") is String:
@@ -140,7 +240,7 @@ func validate_data(data: Variant) -> String:
         return "invalid state.time"
     if not is_finite(float(saved.time.datetime) * 10.0) or saved.time.year != SimulationTime.processed_year(saved.time.datetime):
         return "invalid processed time"
-    if not _number(saved.speed, true) or saved.speed < 1 or saved.speed > Global.SPEED_LIMIT:
+    if not _number(saved.speed, true) or saved.speed < 1 or saved.speed > speed_limit:
         return "invalid state.speed"
     if not _number(saved.speed_in_year) or saved.speed_in_year != pow(10.0, saved.speed - 1):
         return "invalid state.speed_in_year"
@@ -187,7 +287,7 @@ func validate_data(data: Variant) -> String:
     if not saved.ethics is Dictionary or not saved.civilization_homes is Dictionary:
         return "invalid civilization state"
     for id in saved.ethics:
-        if not Global.CivilizationRules.has(id) or not _number_map(saved.ethics[id], true):
+        if id not in stages or not _number_map(saved.ethics[id], true):
             return "invalid state.ethics." + str(id)
         for ethic in saved.ethics[id]:
             if ethic not in ["m", "l", "w", "d", "c", "b"]:
diff --git a/stage/stage.gd b/stage/stage.gd
index 803e294..2e003de 100644
--- a/stage/stage.gd
+++ b/stage/stage.gd
@@ -9,6 +9,10 @@ var description_targets: Dictionary = {}
 var description_samples: Dictionary = {}
 var description_rates: Dictionary = {}
 var description_elapsed: float = 0.0
+const UI_UPDATE_INTERVAL: float = 0.1
+var ui_elapsed: float = 0.0
+var ui_pages: Vector2i = Vector2i(-1, -1)
+var closing: bool = false
 
 const PAGE_COUNT = 5
 const RESOURCE_PAGE = 1
@@ -89,7 +93,9 @@ func set_datetime(value: float):
     # Simulation time advances in tenths of a year; displaying five decimal
     # places only adds zeroes and suggests precision the simulation does not
     # have.
-    date_time.text = Global.format_number(value, 1) if value != 0.0 else "0.0"
+    var text: String = Global.format_number(value, 1) if value != 0.0 else "0.0"
+    if date_time.text != text:
+        date_time.text = text
 
 #region Item manipulations: update and visibility
 
@@ -97,8 +103,27 @@ func set_datetime(value: float):
 func set_owniverse_item_value() -> void:
     for item_id in owniverse.items_to_update:
         if owniverse_items.has(item_id):
-            owniverse_items[item_id].set_label(owniverse.items_to_update[item_id])
-    owniverse.items_to_update.clear()
+            var item: OwniverseItem = owniverse_items[item_id]
+            if item.is_visible_in_tree() and item.get_global_rect().intersects(stage_page_scroller.get_global_rect()):
+                item.set_label(owniverse.items_to_update[item_id])
+
+
+func _refresh_ui(force: bool = false) -> void:
+    if force or owniverse.item_amounts_dirty:
+        owniverse.refresh_item_amounts(true)
+    set_owniverse_item_value()
+    set_datetime(owniverse.state.time.year)
+    _set_active_page_actions()
+    ui_elapsed = 0.0
+
+
+func _update_ui(delta: float) -> void:
+    ui_elapsed += delta
+    var position_in_pages: float = float(stage_page_scroller.scroll_horizontal) / PAGE_WIDTH
+    var pages := Vector2i(floori(position_in_pages), ceili(position_in_pages))
+    if pages != ui_pages or ui_elapsed >= UI_UPDATE_INTERVAL:
+        ui_pages = pages
+        _refresh_ui()
         
 
 #endregion
@@ -219,6 +244,9 @@ func item_activated(item: OwniverseItem) -> void:
     
     if item.item_id == "S" or item.item_id == "H":
         var _value = owniverse.produce_hs(item.item_id, 100_000)
+    _unlock_items()
+    _refresh_ui(true)
+    _refresh_descriptions()
     
 
 func _check_counters(delta: float) -> Array:
@@ -277,6 +305,8 @@ func _input(event: InputEvent) -> void:
 func _set_active_page_actions() -> void:
     for pa in page_actions:
         if !g_active_items.has(pa): continue
+        if not page_actions[pa].is_visible_in_tree() or not page_actions[pa].get_global_rect().intersects(stage_page_scroller.get_global_rect()):
+            continue
         
         var item_id: String = g_active_items[pa].item_id
         var entity: OwniverseEntity = owniverse.entities[item_id]
@@ -302,12 +332,17 @@ func _page_action_pressed(page_id: int, action_amount: float) -> void:
     
     if action_amount > 0:
         owniverse.produce(item_id, action_amount)
+        _unlock_items()
+        _refresh_ui(true)
+        _refresh_descriptions()
 
 
 #endregion
 
 
 func _ready() -> void:
+    get_tree().auto_accept_quit = false
+    owniverse.defer_item_updates = true
     var inited_result = init_enitities()
     locked_items = inited_result.locked_items
     load_data()
@@ -317,6 +352,7 @@ func _ready() -> void:
     set_datetime(owniverse.state.time.year)
     set_owniverse_item_value()
     _unlock_items()
+    _refresh_ui(true)
     
     g_counters.swipe.sec = 0.2
 
@@ -329,8 +365,7 @@ func _process(delta: float) -> void:
     
     owniverse.evolute(delta)
     _update_descriptions(delta)
-    set_owniverse_item_value()
-    set_datetime(owniverse.state.time.year)
+    _update_ui(delta)
     
     #owniverse.cycle(delta)
     
@@ -339,7 +374,6 @@ func _process(delta: float) -> void:
     var actions = _check_counters(delta)
     _do_actions(actions)
     
-    _set_active_page_actions()
 
 
 func _change_speed(delta: int) -> void:
@@ -421,21 +455,41 @@ func _restore_page() -> void:
     if pending_page >= 0:
         stage_page_scroller.scroll_horizontal = pending_page * PAGE_WIDTH
         pending_page = -1
+    _refresh_ui(true)
 
 
 func save_data() -> void:
     var page: int = pending_page
     if page < 0:
         page = clampi(roundi(float(stage_page_scroller.scroll_horizontal) / PAGE_WIDTH), 0, PAGE_COUNT - 1)
-    SaveManager.save_data("owniverse", "qwerty", {
+    SaveManager.request_save("owniverse", "qwerty", {
         "state": owniverse.state,
         "ui": {"current_page": page},
     })
 
 
 func _notification(what: int) -> void:
-    if is_node_ready() and (what == NOTIFICATION_WM_CLOSE_REQUEST or what == NOTIFICATION_APPLICATION_PAUSED):
+    if not is_node_ready() or closing:
+        return
+    if what == NOTIFICATION_WM_CLOSE_REQUEST:
+        _close_after_save()
+    elif what == NOTIFICATION_APPLICATION_PAUSED:
         save_data()
+        # Mobile platforms can suspend all processing immediately after this event.
+        SaveManager.flush_saves()
+
+
+func _close_after_save() -> void:
+    closing = true
+    set_process(false)
+    set_process_input(false)
+    mouse_filter = Control.MOUSE_FILTER_IGNORE
+    # Stop GUI actions too while the final snapshot is being written.
+    process_mode = Node.PROCESS_MODE_DISABLED
+    save_data()
+    if SaveManager.is_saving():
+        await SaveManager.saves_drained
+    get_tree().quit()
 
 
 func init_enitities() -> Dictionary:
diff --git a/tests/README.md b/tests/README.md
index 4fe941d..50543c2 100644
--- a/tests/README.md
+++ b/tests/README.md
@@ -1,5 +1,18 @@
 # Проверки поэтапного переноса из Owniverse.U
 
+## Фоновое сохранение и частота обновления интерфейса
+
+```sh
+godot --headless --path Owniverse.GI --script res://tests/test_async_save.gd
+godot --headless --path Owniverse.GI --script res://tests/test_ui_updates.gd
+```
+
+Сохранение: основной поток создаёт глубокий снимок состояния и параметров. Рабочий поток проверяет данные, записывает зашифрованный временный файл, проверяет чтением и заменяет основное сохранение; диагностический JSON создаётся из того же снимка. Одновременно работает один писатель. Для каждого имени файла хранится только последний ожидающий запрос. `request_save()` подтверждает постановку в очередь; результат записи сообщает сигнал `save_completed`. При закрытии игра ждёт `saves_drained`, при приостановке приложения и уничтожении менеджера очередь завершается через `flush_saves()`. Копирование снимка остаётся в основном потоке.
+
+Тест сохранений пишет только в уникальную временную папку `/tmp`, затем удаляет собственные файлы. Проверяются независимость снимка, работа кадров при записи, объединение запросов, диагностическая копия, сохранность предыдущего файла при ошибках и завершение очереди при уничтожении менеджера. Сообщения `Invalid save`, `Save blocked` и `Cannot write` в этом тесте ожидаемы.
+
+Счётчики, время и кнопки производства обновляются раз в 0,1 секунды. Изменения симуляции помечают суммы для пересчёта; сами суммы вычисляются при обновлении интерфейса. Текст счётчиков применяется только к видимым элементам и только при изменении строки. Переход между страницами, выбор элемента и производство вызывают немедленное обновление. Описания сохраняют прежний интервал 0,25 секунды. Тест интерфейса использует игровую сцену с отключёнными загрузкой, сохранением и автоматической симуляцией, не обращаясь к сохранению игрока.
+
 ## Время: шаг 0,1 игрового года
 
 ```sh
@@ -15,7 +28,9 @@ godot --headless --path Owniverse.GI --script res://tests/test_time.gd
 - `time.datetime` — накопленный возраст, включая необработанную дробную часть;
 - `time.year` — последний рассчитанный возраст с точностью до десятой доли года.
 
-Сохранения используют только актуальную структуру состояния и не поддерживают прежние форматы.
+Сохранения используют формат 2 и актуальную структуру состояния. Проверяются целостность данных, фоновая запись и повторная загрузка; поддержка и миграция прежних форматов отсутствуют.
+
+Файл с несовместимым номером формата при загрузке переносится в `*.adventure.incompatible.bak` (при совпадении имени добавляется числовой суффикс). Игра начинает новую сессию и может сохранять её в формате 2. Прогресс несовместимого файла не переносится, исходные байты сохраняются в архиве. Ошибка архивирования, расшифровки или повреждение данных текущего формата по-прежнему блокируют перезапись.
 
 ## Согласованные правила эволюции
 
diff --git a/tests/fixtures/ui_stage.gd b/tests/fixtures/ui_stage.gd
new file mode 100644
index 0000000..4348b6e
--- /dev/null
+++ b/tests/fixtures/ui_stage.gd
@@ -0,0 +1,14 @@
+extends "res://stage/stage.gd"
+
+# Keep scene wiring and display logic, without accessing the player's save.
+func load_data() -> bool:
+    return false
+
+func save_data() -> void:
+    pass
+
+func _process(_delta: float) -> void:
+    pass
+
+func _notification(_what: int) -> void:
+    pass
diff --git a/tests/fixtures/ui_stage.gd.uid b/tests/fixtures/ui_stage.gd.uid
new file mode 100644
index 0000000..e08b9b2
--- /dev/null
+++ b/tests/fixtures/ui_stage.gd.uid
@@ -0,0 +1 @@
+uid://c8ewikdhlvnex
diff --git a/tests/test_async_save.gd b/tests/test_async_save.gd
new file mode 100644
index 0000000..ad022c4
--- /dev/null
+++ b/tests/test_async_save.gd
@@ -0,0 +1,100 @@
+extends SceneTree
+
+var failures: int = 0
+var checks: int = 0
+var completions: Array = []
+
+func _initialize() -> void:
+    call_deferred("run")
+
+func check(value: bool, message: String) -> void:
+    checks += 1
+    if not value:
+        failures += 1
+        push_error(message)
+
+func run() -> void:
+    var manager = load("res://autoload/save_manager.gd").new()
+    var directory: String = "/tmp/owniverse-async-%s-%s" % [OS.get_process_id(), Time.get_ticks_usec()]
+    DirAccess.make_dir_recursive_absolute(directory)
+    manager.save_directory = directory
+    root.add_child(manager)
+    manager.save_completed.connect(func(filename, success, error): completions.append([filename, success, error]))
+    var world = load("res://world/owniverse/owniverse.gd").new()
+    var data: Dictionary = {"state": world.state, "ui": {"current_page": 1}}
+    var global: Node = root.get_node("Global")
+    var old_plaintext: bool = global.save_plaintext_copy
+    global.save_plaintext_copy = true
+    check(manager.request_save("snapshot", "test-password", data), "Snapshot queued")
+    data.state.energy = 99.0
+    data.ui.current_page = 2
+    var frames: int = 0
+    var deadline: int = Time.get_ticks_msec() + 10000
+    while manager.is_saving() and Time.get_ticks_msec() < deadline:
+        frames += 1
+        await process_frame
+    check(not manager.is_saving() and frames > 0, "Frames continue while save is pending")
+    var saved: Dictionary = manager.load_data("snapshot", "test-password")
+    check(saved.state.energy == 1e14 and saved.ui.current_page == 1, "Worker owns a deep snapshot")
+    var plain: Dictionary = JSON.parse_string(FileAccess.get_file_as_string(directory.path_join("snapshot.adventure.json")))
+    check(plain.state.energy == 1e14, "Diagnostic JSON uses same snapshot")
+    check(completions.size() == 1 and completions[0][1], "Completion reports successful write")
+
+    completions.clear()
+    data.state.energy = 1.0
+    manager.request_save("latest", "test-password", data)
+    data.state.energy = 2.0
+    manager.request_save("latest", "test-password", data)
+    data.state.energy = 3.0
+    manager.request_save("latest", "test-password", data)
+    data.state.energy = 4.0
+    manager.flush_saves()
+    check(completions.size() == 2, "Repeated requests coalesce behind active write")
+    check(manager.load_data("latest", "test-password").state.energy == 3.0, "Last queued snapshot wins")
+
+    var incompatible_path: String = directory.path_join("incompatible.adventure")
+    var incompatible = FileAccess.open_encrypted_with_pass(incompatible_path, FileAccess.WRITE, "test-password")
+    incompatible.store_var({"format_version": -1, "state": {"unknown": true}}, false)
+    incompatible.close()
+    var original: PackedByteArray = FileAccess.get_file_as_bytes(incompatible_path)
+    var previous_archive = FileAccess.open(incompatible_path + ".incompatible.bak", FileAccess.WRITE)
+    previous_archive.store_string("keep previous backup")
+    previous_archive.close()
+    manager.blocked_saves.incompatible = true
+    check(manager.load_data("incompatible", "test-password").is_empty() and manager.last_error == "", "Unsupported format permits a fresh session")
+    check(not manager.blocked_saves.has("incompatible") and not FileAccess.file_exists(incompatible_path), "Incompatible file no longer blocks saving")
+    check(FileAccess.get_file_as_bytes(incompatible_path + ".incompatible.bak.1") == original, "Unsupported save archived without losing bytes")
+    check(FileAccess.get_file_as_string(incompatible_path + ".incompatible.bak") == "keep previous backup", "Earlier archive preserved")
+    check(manager.request_save("incompatible", "test-password", data), "New session can queue a save")
+    manager.flush_saves()
+    check(manager.load_data("incompatible", "test-password").state == data.state, "New format saves and reloads after incompatible file")
+
+    # Expected failures below must leave the last good encrypted file intact.
+    data.state.energy = -1.0
+    manager.request_save("latest", "test-password", data)
+    manager.flush_saves()
+    check(not completions.back()[1] and manager.last_error.contains("Invalid save"), "Worker validation error reaches main thread")
+    check(manager.load_data("latest", "test-password").state.energy == 3.0, "Invalid snapshot preserves previous save")
+    manager.blocked_saves.latest = true
+    check(not manager.request_save("latest", "test-password", data), "Unreadable save protection also applies to queue")
+    # A valid snapshot exercises an actual I/O failure, not validation.
+    data.state.energy = 5.0
+    manager.request_save("missing/failure", "test-password", data)
+    manager.flush_saves()
+    check(manager.last_error.contains("Cannot write"), "I/O error reported without hanging queue")
+
+    manager.request_save("shutdown", "test-password", data)
+    data.state.energy = 6.0
+    manager.request_save("shutdown", "test-password", data)
+    manager.free()
+    var reader = load("res://autoload/save_manager.gd").new()
+    reader.save_directory = directory
+    check(reader.load_data("shutdown", "test-password").state.energy == 6.0, "Teardown drains final pending snapshot")
+    reader.free()
+    world.free()
+    global.save_plaintext_copy = old_plaintext
+    for filename in DirAccess.get_files_at(directory):
+        DirAccess.remove_absolute(directory.path_join(filename))
+    DirAccess.remove_absolute(directory)
+    print("Async save: %d checks, %d failures (validation/block/I/O errors above are intentional)" % [checks, failures])
+    quit(0 if failures == 0 else 1)
diff --git a/tests/test_async_save.gd.uid b/tests/test_async_save.gd.uid
new file mode 100644
index 0000000..87949b2
--- /dev/null
+++ b/tests/test_async_save.gd.uid
@@ -0,0 +1 @@
+uid://dsn0ih3yfrry2
diff --git a/tests/test_ui_updates.gd b/tests/test_ui_updates.gd
new file mode 100644
index 0000000..de5c88f
--- /dev/null
+++ b/tests/test_ui_updates.gd
@@ -0,0 +1,55 @@
+extends SceneTree
+
+var checks: int = 0
+var failures: int = 0
+
+func _initialize() -> void:
+    call_deferred("run")
+
+func check(value: bool, message: String) -> void:
+    checks += 1
+    if not value:
+        failures += 1
+        push_error(message)
+
+func run() -> void:
+    var scene = load("res://world/world.tscn").instantiate()
+    var stage = scene.get_node("Stage")
+    stage.owniverse.free()
+    stage.set_script(load("res://tests/fixtures/ui_stage.gd"))
+    root.add_child(scene)
+    await process_frame
+    await process_frame
+    stage.stage_page_scroller.scroll_horizontal = stage.PAGE_WIDTH
+    await process_frame
+    stage.owniverse.state.amount.H = 1000.0
+    stage.owniverse.state.amount.RD = 2.0
+    stage.owniverse.refresh_item_amounts()
+    stage._update_ui(0.0)
+    var hydrogen = stage.owniverse_items.H
+    var dwarf = stage.owniverse_items.RD
+    check(hydrogen.description.text == "1 000", "Visible page updates immediately on navigation")
+    check(dwarf.description.text == "", "Offscreen counters are not rendered")
+    stage.owniverse.state.amount.H = 2000.0
+    stage.owniverse.refresh_item_amounts()
+    check(stage.owniverse.item_amounts_dirty and stage.owniverse.items_to_update.H == 1000.0, "Simulation invalidates without recalculating display sums")
+    stage._update_ui(0.05)
+    check(hydrogen.description.text == "1 000", "No refresh before interval")
+    stage._update_ui(0.051)
+    check(hydrogen.description.text == "2 000" and not stage.owniverse.item_amounts_dirty, "Latest state appears at interval")
+    stage.item_activated(hydrogen)
+    check(hydrogen.description.text == root.get_node("Global").format_number(stage.owniverse.state.amount.H), "Player production updates counter immediately")
+    check(stage.owniverse.state.amount.H > 2000.0, "Production action actually executed")
+    dwarf.visible = true
+    stage.stage_page_scroller.scroll_horizontal = 2 * stage.PAGE_WIDTH
+    await process_frame
+    stage._update_ui(0.0)
+    check(dwarf.description.text == "2", "Newly visible page receives cached latest values")
+    stage.owniverse.state.time.year = 1234.5
+    stage._update_ui(0.1)
+    check(stage.date_time.text == "1 234.5", "Time uses throttled display with tenths")
+    for entity in stage.owniverse.entities.values(): entity.free()
+    stage.owniverse.free()
+    scene.free()
+    print("UI updates: %d checks, %d failures" % [checks, failures])
+    quit(0 if failures == 0 else 1)
diff --git a/tests/test_ui_updates.gd.uid b/tests/test_ui_updates.gd.uid
new file mode 100644
index 0000000..1003fc4
--- /dev/null
+++ b/tests/test_ui_updates.gd.uid
@@ -0,0 +1 @@
+uid://c8bt2hxqm4hsf
diff --git a/ui/actions/actions.gd b/ui/actions/actions.gd
index fc40598..3723bdf 100644
--- a/ui/actions/actions.gd
+++ b/ui/actions/actions.gd
@@ -47,7 +47,9 @@ func _set_action_values(values: Array, displayed: Array) -> void:
     for ind in range(0, 5):
         action_values[ind] = values[ind]
         # Keep the original request for execution; show the exact planned output.
-        action_labels[ind].text = Global.format_number(displayed[ind]) if displayed[ind] > 0 else ""
+        var text: String = Global.format_number(displayed[ind]) if displayed[ind] > 0 else ""
+        if action_labels[ind].text != text:
+            action_labels[ind].text = text
         
 
 func _on_action_button_pressed(button_id: int) -> void:
diff --git a/ui/owniverse_item/owniverse_item.gd b/ui/owniverse_item/owniverse_item.gd
index 18b1368..ef2f0b5 100644
--- a/ui/owniverse_item/owniverse_item.gd
+++ b/ui/owniverse_item/owniverse_item.gd
@@ -20,7 +20,9 @@ var item_type = ""
 
 
 func set_label(value: float) -> void:
-    description.text = Global.format_number(value)
+    var text: String = Global.format_number(value)
+    if description.text != text:
+        description.text = text
     #description.text = str(value)
 
 
diff --git a/world/owniverse/owniverse.gd b/world/owniverse/owniverse.gd
index 254ad92..c1e7c5b 100644
--- a/world/owniverse/owniverse.gd
+++ b/world/owniverse/owniverse.gd
@@ -14,6 +14,8 @@ var _group_members: Dictionary = {}
 var _indexed_entity_count: int = -1
 
 var items_to_update: Dictionary[String, float] = {}
+var defer_item_updates: bool = false
+var item_amounts_dirty: bool = true
 
 var auto_production: Array = []
 var locked_entities: Array = []
@@ -146,8 +148,12 @@ func get_item_amounts(total_produced: bool = false) -> Dictionary[String, float]
     return result
 
 
-func refresh_item_amounts() -> void:
+func refresh_item_amounts(force: bool = false) -> void:
+    item_amounts_dirty = true
+    if defer_item_updates and not force:
+        return
     items_to_update = get_item_amounts()
+    item_amounts_dirty = false
 
 
 func _add_time_delta(delta: float) -> Dictionary: