diff --git a/apps/studio/docs/record-channel.md b/apps/studio/docs/record-channel.md
index 2bbe988..e2ab314 100644
--- a/apps/studio/docs/record-channel.md
+++ b/apps/studio/docs/record-channel.md
@@ -318,7 +318,7 @@ SDK 版本，「由视频重算」前这些提示必须让操作者看到（回
 ### 回放界面
 
 回放**与实时是同一套界面**：`ui/playback_dialog.py`、`ui/replay_bar.py` 与深度重算引擎都
-已删除。`replay.py::ReplayController` 只读录制并发信号，主窗口把它接到同一套面板上——
+已删除。`replay.py::ReplayEngine` 只读录制并发信号，主窗口把它接到同一套面板上——
 状态轨的主按钮在回放视图里变成「▶ 回放 / ⏸ 暂停」（`toolbar.set_run_role`），来源槽换成
 「选择录制视频…」。布局、单位、看点与关闭流程见 `docs/shell-lifecycle.md` §2
 （含「由视频重算」复核模式）。
diff --git a/apps/studio/docs/shell-lifecycle.md b/apps/studio/docs/shell-lifecycle.md
index f090dec..03652bd 100644
--- a/apps/studio/docs/shell-lifecycle.md
+++ b/apps/studio/docs/shell-lifecycle.md
@@ -60,11 +60,14 @@
 同一套图表手势。**唯一的差别是左上的来源槽**——实时是摄像机，回放是一段录制视频。
 `ui/replay_bar.py`（进度条 + 录制目录选择）与 `PlaybackDialog` 都已删除。
 
-- `apps/studio/src/orisys_studio/replay.py::ReplayController(QObject)`：录制读取、游标、
+- `apps/studio/src/orisys_studio/replay.py::ReplayEngine(QObject)`：录制读取、游标、
   回放提示（降采样 / 跨版本）。它不画任何东西，只发信号：`position_changed` /
   `frames_changed` / `status_changed` / `recording_changed`。深度重算引擎
   （`DepthRecomputer` / `depth_backends`）已随回放条一起删除——用户不需要这条回放路径，
   要复核算法就用「由视频重算」。
+  它叫 *engine* 是因为它只回答「t 时刻是什么」；传输策略（何时开始、播完意味着什么、
+  重算是否在跑）与 2D 渲染属于窗口级的 `ReplayController`（见
+  `docs/architecture/studio-architecture.md` 建议 1）。
 - **选视频即选录制**：状态轨的「选择录制视频…」（`toolbar.btn_replay_video`）与
   「文件 → 打开视频…」都走 `_load_replay_video(path)`——视频所在目录就是录制目录，
   于是曲线自动配对同目录的 `forces.csv`。视频与 CSV 仍然同时记录（录制格式不变）。
diff --git a/apps/studio/src/orisys_studio/app_window.py b/apps/studio/src/orisys_studio/app_window.py
index bbabe1d..2d30c8f 100644
--- a/apps/studio/src/orisys_studio/app_window.py
+++ b/apps/studio/src/orisys_studio/app_window.py
@@ -48,7 +48,7 @@ from orisys_app_shared.paths import recordings_dir
 from orisys_app_shared.record import RecordConfig
 from orisys_app_shared.record.sample import to_record_sample
 from orisys_studio.recording import RecordingCoordinator, record_config_from_prefs
-from orisys_studio.replay import ReplayController
+from orisys_studio.replay import ReplayEngine
 from orisys_studio.scene3d.prefs import settings_to_prefs
 from orisys_app_shared.i18n import set_locale, t
 from orisys_app_shared.logging import report_error
@@ -190,8 +190,10 @@ class StudioMainWindow(QMainWindow):
         self._run_source_label = ""
         # ---- replay ---------------------------------------------------------
         # One engine for the history view: the recording reader, the cursor and
-        # the asynchronous depth recomputation. It renders nothing itself.
-        self.replay = ReplayController(self)
+        # the asynchronous depth recomputation. It renders nothing itself; the
+        # transport policy around it will move into a ReplayController (see
+        # docs/architecture/studio-architecture.md, suggestion 1).
+        self.replay = ReplayEngine(self)
         # ---- record channel -------------------------------------------------
         # Fed from the acquisition thread via the worker's sink list, so it does
         # not depend on the UI refresh rate or on which panels are visible.
diff --git a/apps/studio/src/orisys_studio/replay.py b/apps/studio/src/orisys_studio/replay.py
index 8324c7a..a88bb81 100644
--- a/apps/studio/src/orisys_studio/replay.py
+++ b/apps/studio/src/orisys_studio/replay.py
@@ -6,6 +6,12 @@ panel, the curves read the recording through
 :class:`~orisys_app_shared.force.source.RecordingCurveSource`, and the transport
 on the chart header drives :meth:`set_position`.
 
+It is an *engine*, not a controller: it answers "what is at t?" and knows nothing about
+the transport's policy (when to start, what the end of the timeline means, whether a
+recompute pass is running) or about the widgets. That policy lives in
+``ReplayController`` (the window-level controller for this view), which is why the two
+names are deliberately different — see ``apps/studio/docs/shell-lifecycle.md``.
+
 There is no depth recomputation here: depth is not stored with a recording, the
 replay view shows the recorded frames, and re-running the pipeline over a video
 is the acquisition path's job (see the studio's "recompute" mode).
@@ -37,7 +43,7 @@ def _sdk_version() -> str:
         return ""
 
 
-class ReplayController(QObject):
+class ReplayEngine(QObject):
     """Open one recording and answer "what is at t?" for every view."""
 
     #: The cursor moved; the chart cursor and the 2D panel follow.
diff --git a/apps/studio/tools/ui_check.py b/apps/studio/tools/ui_check.py
index bef1e12..0d0d0b4 100644
--- a/apps/studio/tools/ui_check.py
+++ b/apps/studio/tools/ui_check.py
@@ -2972,7 +2972,7 @@ def main() -> int:
         recorder.on_packet(_fake_packet(index))
     recorder.stop()
 
-    from orisys_studio.replay import ReplayController
+    from orisys_studio.replay import ReplayEngine
 
     # The replay lives in the main window: one engine, one progress bar, and the
     # charts read the recording itself.
diff --git a/docs/architecture/studio-architecture.md b/docs/architecture/studio-architecture.md
index 73f6077..5a8ae2c 100644
--- a/docs/architecture/studio-architecture.md
+++ b/docs/architecture/studio-architecture.md
@@ -146,7 +146,7 @@ graph TB
     subgraph SRC["生产者（4 条）"]
         LIVE["实时 packet.processed_frame + flow + depth"]
         RECOMP["重算：同一采集链跑在录像上"]
-        REPLAY["回放：ReplayController.video_frame_bgr() 原始帧"]
+        REPLAY["回放：ReplayEngine.video_frame_bgr() 原始帧"]
         PREV["预览：摄像头原始帧"]
     end
     IB["image_backend.py（共享）<br/>ImageFrame → plan_image() → render_image()"]