diff --git a/apps/studio/config/compound_eye.png b/apps/studio/config/compound_eye.png
index 3e6375c..7ea4e12 100644
Binary files a/apps/studio/config/compound_eye.png and b/apps/studio/config/compound_eye.png differ
diff --git a/apps/studio/config/locales/en_US.json b/apps/studio/config/locales/en_US.json
index 5d9cc6c..bbab459 100644
--- a/apps/studio/config/locales/en_US.json
+++ b/apps/studio/config/locales/en_US.json
@@ -141,8 +141,11 @@
     "window_tip": "Drag the highlighted region to move the window: this strip is the timeline of the whole session",
     "no_data": "—",
     "mode_follow": "Following live",
-    "mode_browse": "Browsing history (display paused; capture and recording continue)",
+    "mode_follow_tip": "The charts follow the newest sample and the window scrolls with it",
+    "mode_browse": "Browsing history",
+    "mode_browse_tip": "Display paused, capture and recording continue; drag or scroll to move the window, “back to latest” returns to live",
     "mode_replay": "Replaying a recording (browsing)",
+    "mode_replay_tip": "The charts read the open recording; capture and recording continue",
     "return_latest": "Back to latest",
     "return_latest_tip": "Leave history browsing and follow the newest data again",
     "overview": "Whole session",
@@ -150,6 +153,9 @@
     "box_zoom": "Box zoom",
     "box_zoom_tip": "Switch to rubber-band zoom (drag a region on the chart)",
     "selection": "Selection {duration}s / {samples} samples — {detail}",
+    "selection_summary": "Selection {duration}s / {samples} samples",
+    "selection_detail": "mean {mean} · σ {std}",
+    "selection_peak_tip": "The large number is the selection's peak; the line under it is its mean",
     "selection_empty": "No valid samples in the selection",
     "value_unavailable": "n/a",
     "value_unavailable_tip": "No curve is loaded for {channel}, so it has no value in this unit (raw counts are never shown in its place)",
@@ -326,7 +332,6 @@
     "apply_no_target": "No device to apply to (run an acquisition first)"
   },
   "status": {
-    "ready": "Ready",
     "phase_idle": "Idle",
     "phase_connecting": "Connecting",
     "phase_running": "Acquiring",
@@ -339,15 +344,12 @@
     "calibrated_axes": "Calibrated · {axes}",
     "uncalibrated": "Uncalibrated",
     "config_none": "no config",
-    "device_label": "config {config}",
     "camera_none": "No cameras found",
     "camera_found": "Found {count} camera(s): {names}",
     "preview_started": "Preview started (camera {camera_id})",
     "preview_stopped": "Preview stopped",
     "preview_failed": "Preview failed: {error}",
-    "connecting": "Connecting…",
     "connect_slow": "This is taking a while — click “Cancel” or press Esc to abort",
-    "run_started": "Running ({source})",
     "run_stopped": "Stopped",
     "run_stopping": "Stopping… (releasing the device)",
     "run_stopping_cancelled": "Connection cancelled (releasing the device)",
diff --git a/apps/studio/config/locales/zh_CN.json b/apps/studio/config/locales/zh_CN.json
index 0429276..78b2eae 100644
--- a/apps/studio/config/locales/zh_CN.json
+++ b/apps/studio/config/locales/zh_CN.json
@@ -141,8 +141,11 @@
     "window_tip": "拖动高亮区域即可移动视窗；这是整段会话的时间轴",
     "no_data": "—",
     "mode_follow": "跟随实时",
-    "mode_browse": "浏览历史（显示暂停，采集与记录继续）",
+    "mode_follow_tip": "曲线跟随最新样本，窗口随采集滚动",
+    "mode_browse": "浏览历史",
+    "mode_browse_tip": "显示暂停，采集与记录继续；拖动或滚轮改变窗口，点「返回最新」回到实时",
     "mode_replay": "回放录制（浏览）",
+    "mode_replay_tip": "曲线读的是打开的录制；回放期间采集与记录继续",
     "return_latest": "返回最新",
     "return_latest_tip": "退出历史浏览，恢复跟随最新数据",
     "overview": "全程总览",
@@ -150,6 +153,9 @@
     "box_zoom": "框选",
     "box_zoom_tip": "切换为框选放大（拖动图表框选区域）",
     "selection": "选区 {duration}s / {samples} 点 — {detail}",
+    "selection_summary": "选区 {duration}s / {samples} 点",
+    "selection_detail": "均 {mean} · σ {std}",
+    "selection_peak_tip": "上方大号数字是选区的峰值；均值为选区均值",
     "selection_empty": "选区无有效样本",
     "value_unavailable": "不可用",
     "value_unavailable_tip": "{channel} 轴未加载标定曲线，因此没有该单位的数值（不会用原始值冒充）",
@@ -326,7 +332,6 @@
     "apply_no_target": "没有可应用的设备（请先运行一次采集）"
   },
   "status": {
-    "ready": "就绪",
     "phase_idle": "空闲",
     "phase_connecting": "连接中",
     "phase_running": "采集中",
@@ -339,15 +344,12 @@
     "calibrated_axes": "已标定 · {axes}",
     "uncalibrated": "未标定",
     "config_none": "未选配置",
-    "device_label": "配置 {config}",
     "camera_none": "未发现摄像机",
     "camera_found": "发现 {count} 个摄像机: {names}",
     "preview_started": "预览已启动（摄像机 {camera_id}）",
     "preview_stopped": "预览已停止",
     "preview_failed": "预览失败: {error}",
-    "connecting": "正在连接…",
     "connect_slow": "连接耗时较长，可点击「取消连接」或按 Esc 中断",
-    "run_started": "运行中（{source}）",
     "run_stopped": "已停止",
     "run_stopping": "正在停止…（正在释放设备）",
     "run_stopping_cancelled": "已取消连接（正在释放设备）",
diff --git a/apps/studio/docs/record-channel.md b/apps/studio/docs/record-channel.md
index 5d60431..6f07936 100644
--- a/apps/studio/docs/record-channel.md
+++ b/apps/studio/docs/record-channel.md
@@ -52,6 +52,25 @@ UI 线程 _on_run_tick ──> 曲线显示（仍可降帧）
   控件更新必须留在 UI 线程。
 - **sink 是普通 callable 列表**，某个 sink 抛异常会被记录并只影响该 packet，不会杀掉采集。
 
+### 2.1 采集循环只认「新帧」，并据此定义帧率
+
+`CaptureSource.read_latest` 返回的是**后台读取线程的最新一帧**：如果那一刻还没有新帧，
+它把**同一帧**再给一次。采集循环以前不做判断，于是同一帧被反复处理 —— 30 fps 的设备
+录出了 63 行/秒（且 `frame_id` 各不相同，看起来像真的），顶栏的 `packet.fps` 显示的是
+**我们自己的轮询速率**。
+
+- `_capture_sequence(sensor)` 读 `capture_source.status.last_seq`：计数没变就是"还没有新
+  帧"，睡 `CAPTURE_REPEAT_POLL_S`（2 ms）后重试，**不进处理链、不发 packet**。
+  只有带后台读取线程的源才有这个标记；视频文件是同步 `read_raw()`，每次调用都解码下一
+  帧，因此它的计数与"重复"无关，直接忽略（返回 `None`，行为不变）。
+- `packet.fps` 改为**速率**：`(窗口内帧数 - 1) / (首末到达时刻之差)`，窗口 `FPS_WINDOW_S`
+  = 1 s。按"1 秒内到达了多少帧"数数会系统性地偏大（窗口里正好装一秒，抖动就多算一帧）。
+- 这一层是"哪些帧算一帧"的唯一判据，记录、曲线、标定与 CSV 都跟着它走；它不改动
+  `packet.fps` 的语义之外的东西 —— **容器速率**仍然是传感器配置值（见 §6.1）。
+
+`shared/tests/test_worker_frame_rate.py` 用一个假 SDK 驱动真实循环验证：同一帧返回 3 次
+时，packet 数 ≈ 交付帧数（去掉判据后是 11317 : 39），且 `packet.fps` 与交付速率一致。
+
 ### 关键文件
 
 | 文件 | 职责 |
@@ -161,9 +180,9 @@ outputs/recordings/<UTC 时间戳>_session<NNNN>/
 
 `session.json` 的 `video.fps` 是**容器速率**，必须等于传感器的采集速率，取自传感器配置
 （`config/sensors/<type>/sensor.json` 的 `fps`，box 为 30），**不是** packet 里那个
-`fps` 字段 —— 后者是"管线每秒完成多少帧"的计数器，开流瞬间的缓冲突发或视频文件源会让
-它读到 48，用它写 30 fps 的容器就等于把回放播成了快进。这是"传感器 30 fps、录制结果
-48 fps"的直接原因。
+`fps` 字段 —— 后者是"本机每秒处理了多少帧"的实时速率（见 §2.1），开流瞬间的缓冲突发会
+让它高于配置值，用它写 30 fps 的容器就等于把回放播成了快进。这是"传感器 30 fps、录制
+结果 48 fps"的直接原因。
 
 - `StudioMainWindow._video_fps()`：实时相机 → 传感器配置的 `fps`；视频文件源 → 实测值；
   实时相机的实测值另存 `video.measured_fps`，两者都进 `session.json`，对不上时看得见。
diff --git a/apps/studio/docs/shell-lifecycle.md b/apps/studio/docs/shell-lifecycle.md
index 6d42c55..19a918d 100644
--- a/apps/studio/docs/shell-lifecycle.md
+++ b/apps/studio/docs/shell-lifecycle.md
@@ -118,11 +118,31 @@
 - **符号不替代语义**：每个按钮都带 tooltip 与 `accessibleName`，`ui_check.py` 的
   `chart header and unit chip` 段逐项断言 `text()==""` 且这三样齐全——只有符号没有说明
   等于把动作藏起来。全程总览**区域名**（`window_caption`）仍是文字，它标注的是一块区域。
+- **选区统计在数值卡上，不在下方**：框选/缩放出一段窗口后，每张卡的大号数字变成该窗口的
+  **峰值**、下方小字是该窗口的**均值 · σ**（`chart.selection_detail`），卡片的 tooltip 说明
+  大数字是峰值；曲线下方只剩「选区 4.13 s / 183 点」（完整的一行仍在它的 tooltip 里）。
+  以前把三通道的峰/均/σ 塞在一行 `QLabel` 里，中文长句直接把面板顶出右边界。
+  窗口等于整个会话（「全程总览」）不算选区——那是默认适配，此时卡片回到"游标处样本"。
 - **单位芯片是可点的按钮**（`QPushButton#unitBadge`，不再是 `QLabel`）：点一下就切换
   `N` ⇄ `raw`，同一条命令（`_set_display_unit`）同时改曲线、数值卡与设置区下拉，三处永远
   一致。旧写法只有「raw/N」两个字，看起来像只读状态。
 - 箭头图页脚的放大倍率写成「箭头按位移放大 ×2」，不再只有一个「×2」。
 
+### 状态栏是一条通知行，不是第二条状态行
+
+底部 `QStatusBar` 只承载**一次性通知**（录制结束/失败、标定已应用、连接慢、错误原因）：
+
+- **没有常驻控件**。以前右下角有一条 `配置 sensor.json`（`status.device_label`），而状态轨
+  的传感器摘要按钮已经写着 `MINI · sensor.json`，右下角是同一件事实的第二遍。
+- **消息会过期**（`_NoticeBar.DEFAULT_TIMEOUT_MS` = 6 s）。Qt 的 `showMessage(text)` 默认
+  `msecs=0`，意思是"永不消失"，于是会话刚开始那句「运行中（0）」一直挂到退出；只读状态
+  的读法应该在顶栏（阶段芯片 + 来源槽），所以子类把"没有超时"一律换成 6 秒。
+- **与状态轨重复的两条提示被删掉**：`status.run_started`（「运行中（0）」）与
+  `status.connecting`（「正在连接…」）在轨上分别有「采集中」芯片与相机编号、以及
+  「连接中」芯片。
+- **逐帧重复的通告只发一次**：`status.units_raw_fallback`（无标定 → 显示原始单位）以前每
+  一帧都发一次，等于永久占住通知行；现在每次运行只提示一次。
+
 ### 单位切换是"开关"，不是"重新解释"
 
 曲线缓冲区里的每个数都带着它被测量时的单位。设备在头几帧还没确认标定时，显示会退到
diff --git a/apps/studio/docs/ui-palette.md b/apps/studio/docs/ui-palette.md
index 3e5ebad..db604d2 100644
--- a/apps/studio/docs/ui-palette.md
+++ b/apps/studio/docs/ui-palette.md
@@ -220,6 +220,11 @@ flow_ramp = 画布色, #6E4AD0, #FA02F3, #FF8A6B, #D8FF00
    按钮，所以不参与 §6.5 的"同一时刻只有一个实心按钮"计数（`QLabel#unitBadge` 仍是通道
    徽标与传感器缩略图的样式，两者靠控件类型区分）。
 
+8. **数值卡的小字用等宽体，且不会把面板顶宽**。选区统计（均值 · σ）画在数值卡内的 9pt
+   等宽小字上，与 16pt 的大号数字同一列；底部状态栏不再出现长句，因此曲线面板的宽度由
+   三个数值卡决定，而不是由一行统计文字决定。`ui_check.py` 的 `session browsing` 段断言
+   该小字 `width() >= sizeHint().width()`（中文与英文都不裁切）。
+
 ---
 
 ## 7. 三个顶层视图 = 同一窗口的三套布局
diff --git a/apps/studio/src/orisys_studio/app_window.py b/apps/studio/src/orisys_studio/app_window.py
index 0c1f349..43a90b7 100644
--- a/apps/studio/src/orisys_studio/app_window.py
+++ b/apps/studio/src/orisys_studio/app_window.py
@@ -112,6 +112,22 @@ def _reveal_in_explorer(path: Path) -> None:
     subprocess.run(["xdg-open", str(folder)], check=False)
 
 
+class _NoticeBar(QStatusBar):
+    """A status bar whose messages expire.
+
+    Everything that is a *state* — the phase, the source, the calibration, whether
+    the data is valid — is read from the toolbar's rail. This line is for one-off
+    notices, so a message with no timeout is a defect: it is how an hour-old
+    "运行中（0）" was still sitting under a stopped window. Any caller that asks for
+    a permanent message gets ``DEFAULT_TIMEOUT_MS`` instead.
+    """
+
+    DEFAULT_TIMEOUT_MS = 6000
+
+    def showMessage(self, text: str, timeout: int = 0) -> None:  # noqa: N802 - Qt name
+        super().showMessage(str(text or ""), int(timeout) or self.DEFAULT_TIMEOUT_MS)
+
+
 class StudioMainWindow(QMainWindow):
     def __init__(self, prefs: dict[str, Any] | None = None) -> None:
         super().__init__()
@@ -127,6 +143,8 @@ class StudioMainWindow(QMainWindow):
         self._running = False
         self._connect_started_at = 0.0
         self._connect_slow_notified = False
+        #: Whether this run has already said "showing raw, nothing is calibrated".
+        self._raw_fallback_notified = False
         self._preview = None
         self._preview_timer = QTimer(self)
         self._preview_timer.setInterval(33)
@@ -226,13 +244,12 @@ class StudioMainWindow(QMainWindow):
         self.replay_bar.setVisible(False)
         root.addWidget(self.replay_bar)
 
-        self.setStatusBar(QStatusBar())
-        # The phase/record state lives in the toolbar's rail; the status bar is
-        # for transient messages plus one permanent line of device identity.
-        self.device_label = QLabel()
-        self.device_label.setObjectName("panelMeta")
-        self.statusBar().addPermanentWidget(self.device_label)
-        self.cal_panel.status_message.connect(self.statusBar().showMessage)
+        self.setStatusBar(_NoticeBar())
+        # The status bar carries **one-off notices** only (a recording finished, a
+        # calibration was applied, a failure). The phase, the source and the
+        # validity of the data are already on the toolbar's rail, so repeating
+        # them here only put stale text under the window for the whole session.
+        self.cal_panel.status_message.connect(self._notify)
         self.cal_panel.calibration_exported.connect(self._on_calibration_exported)
         self.cal_panel.apply_requested.connect(self._on_calibration_apply)
         self._set_phase("idle")
@@ -1058,10 +1075,18 @@ class StudioMainWindow(QMainWindow):
         self._refresh_status_chip()
         self._refresh_status_rail()
         self._refresh_record_state()
-        if not self._preview_open and not self._running:
-            self.statusBar().showMessage(t("status.ready"))
         self._update_run_enabled()
 
+    #: How long a one-off notice stays on the status bar (see ``_NoticeBar``).
+    NOTICE_MS = _NoticeBar.DEFAULT_TIMEOUT_MS
+
+    def _notify(self, text: str, ms: int = NOTICE_MS) -> None:
+        """Show a one-off notice on the status bar and let it expire."""
+        message = str(text or "")
+        if not message:
+            return
+        self.statusBar().showMessage(message, int(ms))
+
     def _set_phase(self, phase: str) -> None:
         """Track the acquisition phase and reflect it in the status chip."""
         self._session_phase = phase if phase in SESSION_PHASES else "idle"
@@ -1117,7 +1142,6 @@ class StudioMainWindow(QMainWindow):
             self.toolbar.set_data_state(
                 t("status.data_invalid", count=self._record_error_count), "warning"
             )
-        self._refresh_device_label()
 
     def _calibration_summary(self) -> str:
         """What the calibration state means for the three axes.
@@ -1143,14 +1167,6 @@ class StudioMainWindow(QMainWindow):
             return t("status.uncalibrated")
         return t("status.calibrated_axes", axes="+".join(names))
 
-    def _refresh_device_label(self) -> None:
-        label = getattr(self, "device_label", None)
-        if label is None:
-            return
-        config = self.sensor_picker.config_name()
-        config_name = Path(config).name if config else t("status.config_none")
-        label.setText(t("status.device_label", config=config_name))
-
     # ---------------------------------------------------------- record state
     def _record_stats(self):
         """``(state, stats, directory)`` — the single read of the record channel.
@@ -1844,6 +1860,7 @@ class StudioMainWindow(QMainWindow):
         self._set_phase("connecting")
         self._connect_started_at = time.perf_counter()
         self._connect_slow_notified = False
+        self._raw_fallback_notified = False
         self.cal_panel.set_meta_context(sensor_type=sensor_type, config_ref=config_ref)
         self.cal_panel.set_running(True)
         self.toolbar.set_source_controls_enabled(False)
@@ -1854,7 +1871,8 @@ class StudioMainWindow(QMainWindow):
         self._update_run_enabled()
         self._refresh_status_rail()
         self._refresh_record_state()
-        self.statusBar().showMessage(t("status.connecting"))
+        # The phase chip on the rail already reads 连接中, so there is no status
+        # bar copy of it here (see ``_NoticeBar``).
         logger.info(
             "Connecting type=%s source=%s config=%s",
             sensor_type,
@@ -1988,9 +2006,9 @@ class StudioMainWindow(QMainWindow):
             self._connect_slow_notified = True
             self.toolbar.set_reset_enabled(True)
             self._sync_shortcut_actions()
-            self.statusBar().showMessage(
-                t("status.run_started", source=self._run_source_label)
-            )
+            # No status-bar line here: the rail's phase chip says 采集中 and the
+            # source slot names the camera, so "运行中（0）" was a second copy of
+            # the same fact that then stayed on screen for the rest of the session.
 
         if is_new:
             self._last_plot_packet_key = packet_key
@@ -2005,7 +2023,14 @@ class StudioMainWindow(QMainWindow):
                     sample=record,
                 )
                 if display.using_raw_fallback:
-                    self.statusBar().showMessage(t("status.units_raw_fallback"))
+                    # Announced once per run, not once per frame: a notice that is
+                    # re-issued every 16 ms never expires, and the rail already
+                    # carries the calibration state.
+                    if not self._raw_fallback_notified:
+                        self._raw_fallback_notified = True
+                        self._notify(t("status.units_raw_fallback"))
+                else:
+                    self._raw_fallback_notified = False
                 self._last_sample_valid = True
                 self._last_display_fallback = bool(display.using_raw_fallback)
                 self._last_display_available = tuple(bool(flag) for flag in display.available)
diff --git a/apps/studio/src/orisys_studio/ui/force_plots.py b/apps/studio/src/orisys_studio/ui/force_plots.py
index a9fb8a2..d6f4d09 100644
--- a/apps/studio/src/orisys_studio/ui/force_plots.py
+++ b/apps/studio/src/orisys_studio/ui/force_plots.py
@@ -50,6 +50,10 @@ VALUE_FONT_PT = 16
 #: timeline. One second is wide enough that a sample is always inside it and small
 #: enough that reading a recording from disk stays free while scrubbing.
 CURSOR_READOUT_S = 0.5
+#: How much of the session an edge must be inset by before the visible window
+#: counts as a *selection* rather than the default "whole session" fit. 1% of the
+#: session absorbs the float noise of a fit without hiding a real zoom.
+SELECTION_EPSILON = 0.01
 
 
 def _window_brush(theme: str):
@@ -140,6 +144,9 @@ class ForcePlotsPanel(QFrame):
         self._mode = "follow"
         self._window: tuple[float, float] = (0.0, 0.0)
         self._cursor_t = 0.0
+        #: The current selection's statistics, or None when the cards describe the
+        #: cursor instead (following live, a fitted session, a replay).
+        self._selection = None
         self._syncing = False
         self._overview_dirty = True
         self._last_overview_at = 0.0
@@ -198,17 +205,21 @@ class ForcePlotsPanel(QFrame):
         values_row.setSpacing(14)
         self.value_cards: list[QFrame] = []
         self.value_labels: list[QLabel] = []
+        self.value_details: list[QLabel] = []
         self.channel_badges: list[QLabel] = []
         self.channel_names: list[QLabel] = []
         self.value_units: list[QLabel] = []
         for label in CHANNEL_LABELS:
-            card, badge, name_label, value_label, unit_label = self._build_value_card(label)
+            card, badge, name_label, value_label, unit_label, detail_label = (
+                self._build_value_card(label)
+            )
             values_row.addWidget(card, 1)
             self.value_cards.append(card)
             self.channel_badges.append(badge)
             self.channel_names.append(name_label)
             self.value_labels.append(value_label)
             self.value_units.append(unit_label)
+            self.value_details.append(detail_label)
         root.addWidget(self.value_group)
 
         self.plot_frame = QFrame()
@@ -316,11 +327,15 @@ class ForcePlotsPanel(QFrame):
 
     def _build_value_card(
         self, channel: str
-    ) -> tuple[QFrame, QLabel, QLabel, QLabel, QLabel]:
+    ) -> tuple[QFrame, QLabel, QLabel, QLabel, QLabel, QLabel]:
         """One axis readout: channel badge + name over a large monospace value.
 
         The value is deliberately borderless and large — three boxed cards side
         by side were part of what made the panel look fragmented.
+
+        The third line carries the selection's mean and σ. It exists on every card
+        and is kept at a fixed height even while empty, so entering a selection
+        adds a number instead of moving the charts.
         """
         card = QFrame()
         card.setObjectName("valueGroup")
@@ -354,7 +369,13 @@ class ForcePlotsPanel(QFrame):
         value_row.addWidget(unit_label)
         value_row.addStretch(1)
         layout.addLayout(value_row)
-        return card, badge, name_label, value_label, unit_label
+
+        detail_label = QLabel()
+        detail_label.setObjectName("hintText")
+        detail_label.setFont(_mono_font(9))
+        detail_label.setFixedHeight(detail_label.fontMetrics().height())
+        layout.addWidget(detail_label)
+        return card, badge, name_label, value_label, unit_label, detail_label
 
     def set_theme(self, theme: str) -> None:
         self._theme = theme
@@ -446,11 +467,13 @@ class ForcePlotsPanel(QFrame):
         self._mode = "follow"
         self._window = (0.0, 0.0)
         self._cursor_t = 0.0
+        self._selection = None
         self._overview_dirty = True
         self._interactive(False)
         self.set_cursor(0.0)
         self.overview_curve.setData([], [])
         self.stats_label.setText("")
+        self.stats_label.setToolTip("")
         self._render_value_cards()
         self._apply_axis_mode()
         self._refresh_mode_label()
@@ -633,13 +656,17 @@ class ForcePlotsPanel(QFrame):
         self._clear_curves()
         self._mode = "follow"
         self._window = (0.0, 0.0)
+        self._selection = None
+        # The strip described the *previous* source's window: a summary left
+        # behind here would claim a selection that no longer exists.
+        self.stats_label.setText("")
+        self.stats_label.setToolTip("")
         self._overview_dirty = True
         self._refresh_mode_label()
         self._apply_axis_mode()
         if not self._source_ready:
             self.overview_curve.setData([], [])
             self.window_label.setText("")
-            self.stats_label.setText("")
             return
         self._sync_overview()
         self._reload_from_store()
@@ -728,6 +755,9 @@ class ForcePlotsPanel(QFrame):
         self._interactive(mode == "browse")
         self._refresh_mode_label()
         self._sync_overview()
+        if mode == "follow":
+            # Leaving the selection: the cards go back to describing the cursor.
+            self._update_selection_readout()
         self._readout_at_cursor()
         self.mode_changed.emit(mode)
 
@@ -818,6 +848,10 @@ class ForcePlotsPanel(QFrame):
             return
         if not self._source_ready:
             return
+        if self._selection_active():
+            # The cards are stating the selection's peak / mean / σ; the cursor is
+            # inside that window and must not overwrite them.
+            return
         first, last = self._source.extent()
         t0 = max(first, self._cursor_t - CURSOR_READOUT_S)
         t1 = min(last, self._cursor_t + CURSOR_READOUT_S)
@@ -837,34 +871,83 @@ class ForcePlotsPanel(QFrame):
         self._render_value_cards()
 
     def _update_selection_readout(self) -> None:
+        """Refresh what the selection is worth: the cards, and the strip's size.
+
+        The per-channel numbers live on the cards (peak, then mean · σ); the strip
+        under the charts keeps only how long the selection is and how many samples
+        it holds, because that is all that fits there. The full line stays in the
+        strip's tooltip.
+        """
         if not self._source_ready:
+            self._selection = None
             self.stats_label.setText("")
+            self.stats_label.setToolTip("")
+            self._render_value_cards()
+            return
+        if not self._selection_active():
+            # Following live, or fitted to the whole session: the cards are the
+            # readout of the cursor, not of a window.
+            self._selection = None
+            self.stats_label.setText("")
+            self.stats_label.setToolTip("")
+            self._render_value_cards()
             return
         t0, t1 = self._window
         stats = self._source.statistics(t0, t1, unit=self._unit)
         if stats.samples == 0:
+            self._selection = None
             self.stats_label.setText(t("chart.selection_empty"))
+            self.stats_label.setToolTip("")
+            self._render_value_cards()
             return
+        self._selection = stats
+        self.stats_label.setText(
+            t(
+                "chart.selection_summary",
+                duration=f"{stats.duration_s:.2f}",
+                samples=stats.samples,
+            )
+        )
+        self.stats_label.setToolTip(self._selection_tooltip(stats))
+        self._render_value_cards()
+
+    def _selection_tooltip(self, stats) -> str:
+        """The full selection readout, for the strip's tooltip."""
         unit = unit_display(self._unit)
         parts = []
         for index, label in enumerate(CHANNEL_LABELS):
-            peak = stats.peaks[index]
-            mean = stats.means[index]
-            std = stats.stds[index]
+            peak = float(stats.peaks[index])
             if not np.isfinite(peak):
                 continue
             parts.append(
-                f"{label} 峰 {peak:.3g}{unit} · 均 {mean:.3g} · σ {std:.3g}"
-            )
-        self.stats_label.setText(
-            t(
-                "chart.selection",
-                duration=f"{stats.duration_s:.2f}",
-                samples=stats.samples,
-                detail="   ".join(parts),
+                f"{label} 峰 {peak:.3g}{unit} · 均 {float(stats.means[index]):.3g} "
+                f"· σ {float(stats.stds[index]):.3g}"
             )
+        return t(
+            "chart.selection",
+            duration=f"{stats.duration_s:.2f}",
+            samples=stats.samples,
+            detail="   ".join(parts),
         )
 
+    def _selection_active(self) -> bool:
+        """Whether the visible window is a *selection* and not the whole session.
+
+        Following live is not a selection, and neither is "whole session" — that is
+        the default fit, where the number the operator wants is the one under the
+        cursor. A window that covers the session (the fit, or a zoom back out to
+        it) therefore keeps the cursor readout.
+        """
+        if self._mode != "browse" or not self._source_ready:
+            return False
+        first, last = self._source.extent()
+        span = last - first
+        if span <= 0.0:
+            return False
+        start, end = self._window
+        edge = span * SELECTION_EPSILON
+        return (start - first) > edge or (last - end) > edge
+
     def _sync_overview(self) -> None:
         if not self._source_ready:
             return
@@ -938,11 +1021,19 @@ class ForcePlotsPanel(QFrame):
         return 1200
 
     def _refresh_mode_label(self) -> None:
+        """The mode name on the header, with its meaning in the tooltip.
+
+        The long form ("Browsing history (display paused; capture and recording
+        continue)") did not fit next to the header's icon buttons at 1280–1440 px
+        in English and was simply cut mid-word, so the parenthetical lives in the
+        tooltip and the label stays a name.
+        """
         if self.is_recording_source():
             key = "chart.mode_replay"
         else:
             key = "chart.mode_browse" if self._mode == "browse" else "chart.mode_follow"
         self.mode_label.setText(t(key))
+        self.mode_label.setToolTip(t(f"{key}_tip"))
         # "Back to latest" only means something while reading a live session; a
         # recording has no latest sample to return to.
         self.btn_latest.setEnabled(
@@ -1042,25 +1133,64 @@ class ForcePlotsPanel(QFrame):
             curve.setData([], [])
 
     def _render_value_cards(self) -> None:
+        """One card per channel: what it reads *now*, in the active unit.
+
+        While a selection is being inspected the big number is that window's peak
+        and the line under it its mean and σ — the selection statistics used to be
+        a single long line under the charts, which could not fit and pushed the
+        panel wider.
+        """
         fmt = "{value:.3f}" if self._unit == "N" else "{value:.1f}"
         unavailable = t("chart.value_unavailable")
-        for index, (value_label, unit_label, value) in enumerate(
-            zip(self.value_labels, self.value_units, self._last_values)
+        selecting = self._selection
+        for index, (value_label, unit_label, detail_label, value) in enumerate(
+            zip(
+                self.value_labels,
+                self.value_units,
+                self.value_details,
+                self._last_values,
+            )
         ):
-            if not self._available[index]:
+            available = self._available[index]
+            if selecting is not None:
+                peak = float(selecting.peaks[index])
+                available = bool(np.isfinite(peak))
+                value = peak
+            if not available:
                 # An axis with no curve in this unit: a dash, never a raw count
                 # presented as a newton value.
                 value_label.setText(unavailable)
                 unit_label.setText("")
+                detail_label.setText("")
                 value_label.setToolTip(
                     t("chart.value_unavailable_tip", channel=CHANNEL_LABELS[index])
                 )
                 continue
             value_label.setText(fmt.format(value=value))
-            value_label.setToolTip("")
+            value_label.setToolTip(
+                t("chart.selection_peak_tip") if selecting is not None else ""
+            )
             unit_label.setText(unit_display(self._unit))
+            detail_label.setText(
+                self._selection_detail(index) if selecting is not None else ""
+            )
         self.unit_badge.setText(unit_display(self._unit))
 
+    def _selection_detail(self, index: int) -> str:
+        """``mean · σ`` for one channel of the current selection."""
+        stats = self._selection
+        if stats is None:
+            return ""
+        mean = float(stats.means[index])
+        std = float(stats.stds[index])
+        if not np.isfinite(mean):
+            return ""
+        return t(
+            "chart.selection_detail",
+            mean=f"{mean:.4g}",
+            std=f"{std:.4g}" if np.isfinite(std) else "-",
+        )
+
     def retranslate(self) -> None:
         self.title.setText(t("panels.plots"))
         for badge, label in zip(self.channel_badges, CHANNEL_LABELS):
@@ -1079,4 +1209,6 @@ class ForcePlotsPanel(QFrame):
         self.window_caption.setToolTip(t("chart.window_tip"))
         self._refresh_mode_label()
         self._refresh_window_label()
-        self._render_value_cards()
+        # Which readout a card carries depends on the mode, so the language switch
+        # goes through the same path as a data refresh.
+        self._update_selection_readout()
diff --git a/apps/studio/tests/test_ui_smoke.py b/apps/studio/tests/test_ui_smoke.py
index 9b4fe44..29ff2fb 100644
--- a/apps/studio/tests/test_ui_smoke.py
+++ b/apps/studio/tests/test_ui_smoke.py
@@ -1968,6 +1968,117 @@ def test_a_raw_only_recording_is_never_shown_in_newton(make_window, replay_recor
     assert panel.value_labels[0].text() not in ("", t("chart.value_unavailable"))
 
 
+# ------------------------------------------- selection readout and notices
+
+
+def test_a_selection_moves_its_statistics_onto_the_value_cards(make_window):
+    """The per-channel line under the charts did not fit; the cards hold it now.
+
+    Selecting a window makes the big number that window's peak and the line under
+    it its mean · σ. The strip keeps only how big the selection is, and leaving
+    the selection puts the cursor readout back.
+    """
+    from orisys_app_shared.i18n import t
+
+    window, stuck = _running_window(make_window)
+    window.toolbar.units_combo.setCurrentIndex(0)  # newton
+    window.force_plots.reset()
+    for index in range(90):
+        stuck.emit(ui_check._fake_packet(index))
+        window._on_run_tick()
+
+    plots = window.force_plots
+    assert plots._selection is None, "following live is not a selection"
+    assert plots.stats_label.text() == ""
+    assert plots.value_details[0].text() == "", "a live reading carries a mean line"
+
+    plots.set_window(1.0, 3.0)
+    assert plots.mode() == "browse"
+    assert plots._selection is not None, "the window was not read as a selection"
+
+    summary = plots.stats_label.text()
+    assert summary, "the strip does not state the size of the selection"
+    assert t("chart.selection_summary", duration="1", samples=2)[:4] in summary or (
+        "选区" in summary or "Selection" in summary
+    ), summary
+    # The numbers a reader cannot fit in the strip are on the cards instead.
+    expected_peak = float(plots._selection.peaks[0])
+    expected = f"{expected_peak:.3f}"
+    assert plots.value_labels[0].text() == expected, (
+        f"the FN card is not the selection's peak: {plots.value_labels[0].text()!r}"
+    )
+    detail = plots.value_details[0].text()
+    assert detail and detail != "", detail
+    assert f"{float(plots._selection.means[0]):.4g}" in detail, (detail, plots._selection.means[0])
+    assert "均" in detail or "mean" in detail, detail
+    assert plots.value_labels[0].toolTip(), "the peak is not explained anywhere"
+
+    # "Whole session" is the default fit, so it is not a selection.
+    plots.show_all()
+    assert plots._selection is None, "'whole session' is still treated as a selection"
+    assert plots.value_details[0].text() == ""
+
+    # ...and neither is live mode.
+    plots.set_window(1.0, 3.0)
+    assert plots._selection is not None
+    plots.follow_latest()
+    assert plots._selection is None, "the selection survived 'back to latest'"
+    assert plots.stats_label.text() == ""
+    _finish(window, stuck)
+
+
+def test_the_status_bar_is_a_notice_line_not_a_state_line(make_window):
+    """The rail is the state; the bar shows one-off notices and lets them expire.
+
+    A permanent "config sensor.json" line repeated what the rail's sensor chip
+    already says, and a message with no timeout (the old "运行中（0）") stayed under
+    the window for the whole session.
+    """
+    import time
+
+    from PyQt5.QtWidgets import QApplication
+
+    import orisys_studio.app_window as app_module
+
+    window = _show(make_window(), (1440, 880))
+    assert not hasattr(window, "device_label"), (
+        "the status bar still carries a permanent device line"
+    )
+    assert isinstance(window.statusBar(), app_module._NoticeBar)
+
+    # Qt's default is msecs=0, which means "no timeout": a message that never
+    # expires is what left an hour-old "运行中（0）" under the window.
+    window.statusBar().showMessage("plain call")
+    assert window.statusBar().currentMessage() == "plain call"
+
+    original_timeout = app_module._NoticeBar.DEFAULT_TIMEOUT_MS
+    app_module._NoticeBar.DEFAULT_TIMEOUT_MS = 40
+    try:
+        window.statusBar().showMessage("expiring notice")
+        assert window.statusBar().currentMessage() == "expiring notice"
+        deadline = time.perf_counter() + 1.5
+        while time.perf_counter() < deadline:
+            QApplication.processEvents()
+            if window.statusBar().currentMessage() == "":
+                break
+            time.sleep(0.01)
+        assert window.statusBar().currentMessage() == "", (
+            "a notice stayed on the status bar after its timeout"
+        )
+    finally:
+        app_module._NoticeBar.DEFAULT_TIMEOUT_MS = original_timeout
+
+    window._notify("")
+    assert window.statusBar().currentMessage() == ""
+    window._notify("something happened")
+    assert window.statusBar().currentMessage() == "something happened"
+
+    # The rail states the phase, so the bar does not repeat it.
+    window, stuck = _running_window(make_window)
+    assert window.toolbar.status_chip.text().strip(), "the rail lost its phase chip"
+    _finish(window, stuck)
+
+
 
 
 
diff --git a/apps/studio/tools/ui_check.py b/apps/studio/tools/ui_check.py
index 0738932..fb9d9cb 100644
--- a/apps/studio/tools/ui_check.py
+++ b/apps/studio/tools/ui_check.py
@@ -910,15 +910,21 @@ def main() -> int:
             not rail_squeezed(window),
             f"{theme}: the status rail squeezes {rail_squeezed(window)}",
         )
-        check(
-            "sensor.json" in window.device_label.text(),
-            f"{theme}: the status bar does not name the config file: "
-            f"{window.device_label.text()!r}",
-        )
         check(
             not hasattr(window.toolbar, "source_combo"),
             f"{theme}: the source mode is still a combobox",
         )
+        # The status bar is a notice line, not a second state line: the config
+        # file and the phase are already on the rail, and a message must expire.
+        check(
+            not hasattr(window, "device_label"),
+            f"{theme}: the status bar still carries a permanent device line",
+        )
+        window.statusBar().showMessage("notice")
+        check(
+            window.statusBar().currentMessage() == "notice",
+            f"{theme}: the status bar does not show a message at all",
+        )
 
         # The sensor dialog owns the pickers and the calibration facts.
         window._open_sensor_dialog()
@@ -1617,6 +1623,29 @@ def main() -> int:
         f"the arrow footer does not say what is magnified: "
         f"{header_window.arrow_panel.scale_label.text()!r}",
     )
+    # The header's mode label shares its row with three icon buttons and the unit
+    # chip: the long form of the mode sentence was cut mid-word in English.
+    for lang in ("zh_CN", "en_US"):
+        header_window._set_language(lang)
+        for _ in range(3):
+            app.processEvents()
+        for mode, name in ((False, "follow"), (True, "browse")):
+            if mode:
+                header_plots.set_window(0.2, 1.0)
+            app.processEvents()
+            label = header_plots.mode_label
+            check(
+                label.width() >= label.sizeHint().width(),
+                f"{lang}/{name}: the chart mode label is clipped: "
+                f"{label.width()} < {label.sizeHint().width()} ({label.text()!r})",
+            )
+            check(
+                label.toolTip() != "",
+                f"{lang}/{name}: the mode label does not explain itself",
+            )
+    # The locale is process-wide: leave it where the other sections expect it.
+    header_window._set_language("zh_CN")
+    app.processEvents()
     header_window.close()
     app.processEvents()
 
@@ -1761,6 +1790,25 @@ def main() -> int:
     finally:
         app_module.recordings_dir = original_root
         _shutil.rmtree(scratch, ignore_errors=True)
+
+    # The rail's FPS is the worker's *delivered* frame rate. It used to be a count
+    # of loop iterations (a 30 fps device read 63), so the number the rail prints
+    # must be the packet's, verbatim.
+    window.act_show_fps.setChecked(True)
+    app.processEvents()
+    packet = _fake_packet(0, mono_t=0.0)
+    packet.fps = 30.4
+    stuck.emit(packet)
+    window._on_run_tick()
+    app.processEvents()
+    check(
+        "30.4 FPS" in window.toolbar.source_summary.text(),
+        f"the rail does not show the delivered frame rate: "
+        f"{window.toolbar.source_summary.text()!r}",
+    )
+    window.act_show_fps.setChecked(False)
+    app.processEvents()
+
     window._stop_run(reason="user_stop")
     stuck.release()
     app.processEvents()
@@ -2460,9 +2508,16 @@ def main() -> int:
         all(plot.getViewBox().state["mouseEnabled"][0] for plot in plots.plots),
         "browsing does not enable panning",
     )
-    window_texts = plots.stats_label.text()
-    check(window_texts != "", "no selection statistics in browse mode")
-    check("峰" in window_texts, f"the peak is missing from the readout: {window_texts!r}")
+    # "Whole session" is the default fit, not a selection: the cards still state
+    # the sample under the cursor, and the strip carries no selection summary.
+    check(
+        plots._selection is None,
+        "fitted to the whole session, the cards still hold selection statistics",
+    )
+    check(
+        plots.stats_label.text() == "",
+        f"a fitted session shows a selection summary: {plots.stats_label.text()!r}",
+    )
 
     # Decimation must keep the spike while bounding the point count.
     drawn = max(int(curve.getData()[0].size) for curve in plots.curves)
@@ -2476,6 +2531,50 @@ def main() -> int:
         plots.overview_curve.getData()[0].size > 0,
         "the whole-session overview strip is empty",
     )
+    # A window narrower than the session is a selection: its peak becomes the big
+    # number on each card and its mean/σ the line under it, while the strip keeps
+    # only the size of the selection (the long per-channel line did not fit).
+    check(plots._selection is not None, "zooming in did not record a selection")
+    summary = plots.stats_label.text()
+    check(summary != "", "the strip does not state the size of the selection")
+    check(
+        "峰" not in summary and "均" not in summary,
+        f"the per-channel statistics are still in the strip: {summary!r}",
+    )
+    check(
+        "选区" in summary or "Selection" in summary,
+        f"the strip does not say that the numbers describe a selection: {summary!r}",
+    )
+    expected_peak = float(plots._selection.peaks[0])
+    peak_text = (
+        f"{expected_peak:.3f}" if plots.unit() == "N" else f"{expected_peak:.1f}"
+    )
+    check(
+        plots.value_labels[0].text() == peak_text,
+        f"the FN card is not the selection's peak: {plots.value_labels[0].text()!r}",
+    )
+    check(
+        plots.value_details[0].text() != ""
+        and ("均" in plots.value_details[0].text() or "mean" in plots.value_details[0].text()),
+        f"the card does not state the selection's mean: "
+        f"{plots.value_details[0].text()!r}",
+    )
+    for card, label, detail in zip(
+        plots.value_cards, plots.value_labels, plots.value_details
+    ):
+        check(
+            detail.width() >= detail.sizeHint().width(),
+            f"the selection detail line is clipped: "
+            f"{detail.width()} < {detail.sizeHint().width()}",
+        )
+    # Leaving the selection hands the cards back to the cursor readout.
+    plots.follow_latest()
+    check(plots._selection is None, "the selection survived 'back to latest'")
+    check(
+        plots.value_details[0].text() == "",
+        f"the mean line survived leaving the selection: "
+        f"{plots.value_details[0].text()!r}",
+    )
 
     # A user gesture (the signal pyqtgraph emits for a wheel/drag) enters browse;
     # "back to latest" must actually leave it.
diff --git a/apps/studio/tools/ui_snapshot.py b/apps/studio/tools/ui_snapshot.py
index 86fa428..545a0cb 100644
--- a/apps/studio/tools/ui_snapshot.py
+++ b/apps/studio/tools/ui_snapshot.py
@@ -149,14 +149,39 @@ def _run_scene(window, app, scene: str):
 
 def _demo_data(window) -> None:
     """Fill the plots, the calibration table and the arrow canvas."""
+    from orisys_app_shared.force.session import SessionSample, SessionStore
+
     plots = window.force_plots
+    # The panel reads a *selection* out of the attached source, so the demo needs
+    # a real session store behind it (a store-less panel can only follow live).
+    store = SessionStore()
+    plots.set_store(store)
     for i in range(240):
         t = i / 30.0
         fn = 6.0 + 5.0 * math.sin(t * 1.4)
         fx = 4.0 * math.sin(t * 2.1 + 0.4)
         fy = -3.0 + 2.5 * math.cos(t * 1.1)
+        store.append(
+            SessionSample(
+                frame_id=i,
+                t_rel_s=t,
+                fn_raw=fn * 7.9 + 9.0,
+                fx_raw=fx * 7.9,
+                fy_raw=fy * 7.9,
+                fn_n=fn,
+                fx_n=fx,
+                fy_n=fy,
+                calibrated_axes=("fn", "fx", "fy"),
+            )
+        )
         plots.push(t, fn, fx, fy, unit="N")
 
+    # The overview reads the *source*, and ``push`` only rebuilds it once a second
+    # (the demo fills a whole session in a few milliseconds), so build it once here.
+    plots._overview_dirty = True
+    plots._last_overview_at = 0.0
+    plots._sync_overview()
+
     cal = window.cal_panel
     cal.set_running(True)
     cal.push_raw(9.81, -0.42, 0.10)
@@ -227,6 +252,14 @@ def main() -> int:
             "replay view so the progress bar can be reviewed"
         ),
     )
+    parser.add_argument(
+        "--select",
+        default="",
+        help=(
+            "A,B — browse the live demo session inside that window so the "
+            "selection readout (cards = peak / mean · σ) can be reviewed"
+        ),
+    )
     parser.add_argument("--out", required=True, help="output PNG path")
     args = parser.parse_args()
 
@@ -235,6 +268,14 @@ def main() -> int:
     except ValueError:
         parser.error("--size must look like 1440x880")
 
+    selection = None
+    if args.select:
+        try:
+            start, end = (float(part) for part in args.select.split(",", 1))
+        except ValueError:
+            parser.error("--select must look like 2,6")
+        selection = (start, end)
+
     panels = {part.strip().lower() for part in args.panels.split(",") if part.strip()}
 
     from PyQt5.QtWidgets import QApplication
@@ -281,6 +322,13 @@ def main() -> int:
         for _ in range(4):
             app.processEvents()
 
+    if selection is not None:
+        # A selection is a browse window narrower than the session: the value
+        # cards state its peak and mean · σ, the strip only its size.
+        window.force_plots.set_window(*selection)
+        for _ in range(4):
+            app.processEvents()
+
     out = Path(args.out)
     out.parent.mkdir(parents=True, exist_ok=True)
     ok = window.grab().save(str(out))
diff --git a/shared/src/orisys_app_shared/acquisition/sdk_worker.py b/shared/src/orisys_app_shared/acquisition/sdk_worker.py
index 17ee9de..414663b 100644
--- a/shared/src/orisys_app_shared/acquisition/sdk_worker.py
+++ b/shared/src/orisys_app_shared/acquisition/sdk_worker.py
@@ -36,6 +36,11 @@ STOP_JOIN_TIMEOUT_S = 5.0
 #: How long a new session waits (in its own thread, never on the GUI) for a
 #: previous session that is still winding down before opening the device.
 HANDOVER_TIMEOUT_S = 60.0
+#: Window over which the delivered frame rate is measured.
+FPS_WINDOW_S = 1.0
+#: How long to wait before asking again when the capture source has not produced
+#: a new frame yet. Long enough not to spin, short enough not to add latency.
+CAPTURE_REPEAT_POLL_S = 0.002
 
 # Re-exported so ``from ...sdk_worker import SdkPacket`` keeps working; the
 # definitions live in ``models`` so neither worker depends on the other.
@@ -72,6 +77,29 @@ def _sensor_force_calibrated(sensor, *, config_ref: str | Path | None = None) ->
         return False
 
 
+def _capture_sequence(sensor) -> Optional[int]:
+    """The capture source's delivered-frame counter, when it can mark a repeat.
+
+    ``CaptureSource.read_latest`` returns the newest frame from its background
+    reader; if that reader has not produced another frame yet, the *same* one
+    comes back. Its ``status.last_seq`` advances once per delivered frame, so an
+    unchanged counter means "no new frame". Only a source with a running
+    background reader has that marker: a video file is read synchronously and
+    every call decodes the next frame, so its counter says nothing about repeats
+    and is ignored (``None``).
+    """
+    source = getattr(sensor, "capture_source", None)
+    if source is None:
+        source = getattr(sensor, "_capture_source", None)
+    if source is None or not bool(getattr(source, "running", False)):
+        return None
+    status = getattr(source, "status", None)
+    try:
+        return int(getattr(status, "last_seq"))
+    except (TypeError, ValueError):
+        return None
+
+
 def process_chain(sensor) -> tuple[Optional[np.ndarray], str]:
     """Run the live processing chain for one already-read frame.
 
@@ -595,6 +623,9 @@ class SdkAcquisitionWorker(RecordSinkMixin):
         saw_frame = False
         last_frame_mono = 0.0
         none_streak_start: Optional[float] = None
+        #: The capture sequence of the last frame that was actually *processed*:
+        #: an unchanged counter means the same frame came back again.
+        last_delivered: Optional[int] = None
         # Per-session monotonic frame index: the join key shared by the video,
         # the CSV and the calibration records.
         frame_id = 0
@@ -615,6 +646,18 @@ class SdkAcquisitionWorker(RecordSinkMixin):
                             break
 
                 t0 = time.perf_counter()
+                # ``CaptureSource.read_latest`` hands back the newest frame and,
+                # until the pipeline produces another one, that **same** frame
+                # again. Treating the repeat as a new sample doubled every
+                # measurement (a 30 fps device recorded 63 rows per second) and
+                # made the reported rate this loop's own polling rate. A source
+                # without a background reader (a video file) decodes a new frame
+                # per call, so it has no repeat marker and is left alone.
+                delivered = _capture_sequence(sensor)
+                if delivered is not None and delivered == last_delivered:
+                    time.sleep(CAPTURE_REPEAT_POLL_S)
+                    continue
+                last_delivered = delivered
                 processed = sensor.get_img()
                 if processed is None:
                     if saw_frame and is_file and none_streak_start is None:
@@ -658,9 +701,14 @@ class SdkAcquisitionWorker(RecordSinkMixin):
                 compute_error = compute_error or chain_error
                 t1 = time.perf_counter()
                 frame_times.append(t1)
-                cutoff = t1 - 1.0
+                cutoff = t1 - FPS_WINDOW_S
                 frame_times = [t for t in frame_times if t >= cutoff]
-                fps = float(len(frame_times)) if frame_times else 0.0
+                # A *rate*, not a count: counting arrivals in a one-second window
+                # reads one frame high whenever the window holds a full second of
+                # a jittery stream. The span between the first and last arrival is
+                # exactly what "frames per second" means.
+                span = frame_times[-1] - frame_times[0] if len(frame_times) > 1 else 0.0
+                fps = (len(frame_times) - 1) / span if span > 0.0 else 0.0
                 forces = read_forces_from_sensor(sensor, config_ref=mode.config_ref)
                 invalid_reason = forces.get("invalid_reason") or compute_error
                 raw_frame = _ensure_bgr(raw)
diff --git a/shared/tests/test_worker_frame_rate.py b/shared/tests/test_worker_frame_rate.py
new file mode 100644
index 0000000..524ca3d
--- /dev/null
+++ b/shared/tests/test_worker_frame_rate.py
@@ -0,0 +1,206 @@
+"""Which frame the acquisition loop counts, and at what rate.
+
+``CaptureSource.read_latest`` returns the newest frame from its background reader
+and, if that reader has not produced another one yet, the *same* frame again. The
+loop must not treat the repeat as a new sample: doing so duplicated every
+measurement (a 30 fps device recorded 63 rows per second) and the rail read the
+loop's own polling rate as the device's frame rate.
+"""
+
+from __future__ import annotations
+
+import sys
+import threading
+import time
+import types
+from pathlib import Path
+
+APP_ROOT = Path(__file__).resolve().parents[2]
+BOX_CONFIG = APP_ROOT / "apps" / "studio" / "config" / "sensors" / "box" / "sensor.json"
+
+#: The fake device's own frame period: ~100 frames per second.
+FRAME_PERIOD_S = 0.01
+#: How many times the SDK hands the same frame back before the next one arrives.
+REPEATS_PER_FRAME = 3
+
+
+class _Status:
+    """Stands in for ``orisys.capture.config.CaptureStatus``."""
+
+    def __init__(self) -> None:
+        self.last_seq = 0
+        self.dropped_frames = 0
+
+
+class _CaptureSource:
+    """A background reader that publishes a new frame on its own thread.
+
+    The real one is a thread too: the sequence advances whether or not the
+    consumer asks for a frame, which is exactly why an unchanged sequence means
+    "no new frame" rather than "the consumer has not called yet".
+    """
+
+    def __init__(self, period_s: float = FRAME_PERIOD_S) -> None:
+        self.status = _Status()
+        self.running = True
+        self._period = float(period_s)
+        self._stop = threading.Event()
+        self._thread = threading.Thread(target=self._publish, daemon=True)
+        self._thread.start()
+
+    def _publish(self) -> None:
+        while not self._stop.is_set():
+            if self._stop.wait(timeout=self._period):
+                return
+            self.status.last_seq += 1
+
+    def close(self) -> None:
+        self.running = False
+        self._stop.set()
+        self._thread.join(timeout=1.0)
+
+
+class _Info:
+    """The channel names the worker reads off ``sensor.info``."""
+
+    FNORMAL = "FNORMAL"
+    FSHEARX = "FSHEARX"
+    FSHEARY = "FSHEARY"
+    FNORMAL_RAW = "FNORMAL_RAW"
+    FSHEARX_RAW = "FSHEARX_RAW"
+    FSHEARY_RAW = "FSHEARY_RAW"
+
+
+#: Every sensor the fake SDK handed out, so a test can read its frame counter.
+CREATED: list = []
+
+
+class _Sensor:
+    def __init__(self, *args, **kwargs) -> None:
+        import numpy as np
+
+        self.configured: dict = {}
+        self.connected = True
+        self.capture_source = _CaptureSource()
+        self.frame = np.zeros((8, 8, 3), dtype=np.uint8)
+        self.info = _Info()
+        self.force_calibrated = True
+        CREATED.append(self)
+
+    def configure(self, **kwargs):
+        self.configured = kwargs
+
+    def read_info(self, *names):
+        """The SDK's readout: one value per requested channel, in order."""
+        values = {
+            _Info.FNORMAL: 1.5,
+            _Info.FSHEARX: 0.25,
+            _Info.FSHEARY: -0.25,
+            _Info.FNORMAL_RAW: 15.0,
+            _Info.FSHEARX_RAW: 2.5,
+            _Info.FSHEARY_RAW: -2.5,
+        }
+        return tuple(values.get(str(name), 0.0) for name in names)
+
+    def get_img(self):
+        # ``read_latest``: hand back the newest frame immediately, the same one
+        # again when nothing new has arrived.
+        return self.frame
+
+    def disconnect(self):
+        self.connected = False
+        self.capture_source.close()
+
+
+def _install() -> object:
+    saved = {name: sys.modules.get(name) for name in ("orisys", "orisys.finger")}
+    module = types.ModuleType("orisys")
+    module.__version__ = "fake"
+    module.Sensor = _Sensor  # type: ignore[attr-defined]
+    finger_module = types.ModuleType("orisys.finger")
+    finger_module.FingerRuntime = _Sensor  # type: ignore[attr-defined]
+    module.finger = finger_module  # type: ignore[attr-defined]
+    sys.modules["orisys"] = module
+    sys.modules["orisys.finger"] = finger_module
+    return saved
+
+
+def _restore(saved) -> None:
+    for name, original in saved.items():
+        if original is None:
+            sys.modules.pop(name, None)
+        else:
+            sys.modules[name] = original
+
+
+def _collect(duration_s: float = 1.2):
+    """Run the real worker loop against the fake device.
+
+    Returns ``(packets, delivered)`` — what the loop recorded, and how many frames
+    the fake capture source actually delivered in the same period.
+    """
+    from orisys_app_shared.acquisition.sdk_worker import SdkAcquisitionWorker
+
+    CREATED.clear()
+    saved = _install()
+    worker = SdkAcquisitionWorker()
+    packets: list = []
+    lock = threading.Lock()
+
+    def sink(packet) -> None:
+        with lock:
+            packets.append(packet)
+
+    try:
+        worker.add_sink(sink)
+        worker.start("0", config_ref=BOX_CONFIG)
+        time.sleep(duration_s)
+        worker.stop(wait=True)
+        delivered = CREATED[-1].capture_source.status.last_seq if CREATED else 0
+    finally:
+        _restore(saved)
+    return packets, int(delivered)
+
+
+def _rate(packets) -> float:
+    span = float(packets[-1].mono_t) - float(packets[0].mono_t)
+    return (len(packets) - 1) / span if span > 0 else 0.0
+
+
+def test_the_same_frame_is_not_counted_twice():
+    """One packet per delivered frame, whatever the loop's polling rate is."""
+    packets, delivered = _collect()
+    assert packets, "the loop emitted nothing at all"
+    assert delivered > 10, f"the fake device only delivered {delivered} frames"
+    assert len(packets) <= delivered * 1.5, (
+        f"{len(packets)} packets for {delivered} delivered frames: the repeats "
+        "are being recorded as samples"
+    )
+    assert len(packets) >= delivered * 0.7, (
+        f"only {len(packets)} packets for {delivered} delivered frames"
+    )
+
+
+def test_the_reported_rate_is_the_delivered_rate():
+    """``packet.fps`` describes the frames, not how often the loop asked."""
+    packets, delivered = _collect()
+    reported = [float(packet.fps) for packet in packets if packet.fps]
+    assert reported, "no packet carried a frame rate"
+    measured = _rate(packets)
+    settled = reported[-5:]
+    assert all(value > 10.0 for value in settled), settled
+    assert abs(settled[-1] - measured) < 0.25 * measured, (settled[-1], measured)
+
+
+if __name__ == "__main__":  # pragma: no cover - manual runner
+    failures = 0
+    for name, function in sorted(globals().items()):
+        if name.startswith("test_") and callable(function):
+            try:
+                function()
+                print(f"  ok   {name}")
+            except Exception as exc:  # noqa: BLE001
+                failures += 1
+                print(f"  FAIL {name}: {type(exc).__name__}: {exc}")
+    print(f"failures: {failures}")
+    raise SystemExit(1 if failures else 0)