very nice

cht/app.py

@@ -43,7 +43,9 @@ class ChtApp(Adw.Application):
             css = Gtk.CssProvider()
             css.load_from_string(
                 ".frame-selected { outline: 3px solid @accent_color; outline-offset: -3px; border-radius: 6px; }\n"
-                "row.frame-selected, row.frame-selected:hover { background: alpha(@accent_color, 0.25); outline: none; border-radius: 0; }"
+                "row.frame-selected, row.frame-selected:hover { background: alpha(@accent_color, 0.25); outline: none; border-radius: 0; }\n"
+                ".frame-highlight { outline: 2px solid @warning_color; outline-offset: -2px; border-radius: 4px; opacity: 0.9; }\n"
+                "row.frame-highlight { background: alpha(@warning_color, 0.15); }"
             )
             Gtk.StyleContext.add_provider_for_display(
                 Gdk.Display.get_default(),

cht/stream/lifecycle.py

@@ -23,7 +23,8 @@ class StreamLifecycle:
 
     def __init__(self, *, timeline, waveform_engine, transcriber,
                  on_new_frames, on_waveform_update, on_transcript_ready,
-                 on_scene_marker, on_recorder_restarted):
+                 on_scene_marker, on_recorder_restarted,
+                 on_manifest_updated=None):
         self._timeline = timeline
         self._waveform_engine = waveform_engine
         self._transcriber = transcriber
@@ -34,6 +35,7 @@ class StreamLifecycle:
         self._on_transcript_ready = on_transcript_ready
         self._on_scene_marker = on_scene_marker
         self._on_recorder_restarted = on_recorder_restarted
+        self._on_manifest_updated = on_manifest_updated
 
         # State
         self._streaming = False
@@ -196,4 +198,11 @@ class StreamLifecycle:
             log.warning("Recorder died — restarting into new segment")
             self._stream_mgr.restart_recorder()
             self._on_recorder_restarted(self._stream_mgr.recording_path)
+            # Rebuild manifest with the newly completed segment
+            try:
+                rebuild_manifest(self._stream_mgr.session_dir)
+            except Exception as e:
+                log.error("Manifest rebuild failed: %s", e)
+            if self._on_manifest_updated:
+                GLib.idle_add(self._on_manifest_updated)
         return True

cht/ui/frames_panel.py

@@ -176,6 +176,24 @@ class FramesPanel(Gtk.Box):
         self._selected = None
         self.emit("selection-changed")
 
+    def highlight_nearest(self, timestamp: float) -> None:
+        """Scroll to and briefly highlight the frame closest to *timestamp*."""
+        if not self._order:
+            return
+        best_id = None
+        best_dist = float("inf")
+        for fid, ts in self._timestamps.items():
+            d = abs(ts - timestamp)
+            if d < best_dist:
+                best_dist = d
+                best_id = fid
+        if not best_id or best_id not in self._widgets:
+            return
+        widget = self._widgets[best_id]
+        widget.add_css_class("frame-highlight")
+        self._scroll_to(widget)
+        GLib.timeout_add(400, lambda: widget.remove_css_class("frame-highlight") or False)
+
     def clear(self):
         """Remove all items and reset state."""
         self._selected = None

cht/ui/monitor.py

@@ -217,12 +217,8 @@ class MonitorWidget(Gtk.Box):
                     self._stack.set_visible_child_name("review")
                 return
             elif current == "live":
-                # Transitioning from live: load MKV at cursor position atomically
-                pos = s.cursor
-                if self._review_player and self._recording_path:
-                    self._review_player.load_at(self._recording_path, pos, pause=s.paused)
-                    if not s.paused:
-                        self._review_player.play()
+                # Transitioning from live to scrub: just switch stack.
+                # Don't auto-load the growing MKV — user picks a segment via scrub bar.
                 self._stack.set_visible_child_name("review")
             else:
                 # Already in review (non-scrub): seek if cursor moved

cht/ui/scrub_bar.py

@@ -9,9 +9,12 @@ Drag within a block to scrub frame-by-frame at mouse speed.
 
 import logging
 
+from pathlib import Path
+
 import gi
 gi.require_version("Gtk", "4.0")
-from gi.repository import Gtk, Gdk, GLib, GObject, Pango
+gi.require_version("GdkPixbuf", "2.0")
+from gi.repository import Gtk, Gdk, GLib, GObject, GdkPixbuf
 
 import cairo
 
@@ -49,6 +52,7 @@ class ScrubBar(Gtk.DrawingArea):
         self._proxy_states = {}   # segment_index → "generating" | "ready"
         self._scene_markers = []  # global timestamps
         self._scrubbing = False
+        self._frame_thumbs = []   # list of {timestamp, surface} — cairo surfaces
 
         self.set_draw_func(self._draw)
 
@@ -77,6 +81,12 @@ class ScrubBar(Gtk.DrawingArea):
         self._total_duration = sum(s["duration"] for s in manifest)
         self.queue_draw()
 
+    def set_duration(self, duration: float) -> None:
+        """Update total duration (from Timeline, overrides manifest sum if larger)."""
+        if duration > self._total_duration:
+            self._total_duration = duration
+            self.queue_draw()
+
     def set_cursor(self, global_time: float) -> None:
         """Update the cursor position (from Timeline)."""
         self._cursor = global_time
@@ -97,6 +107,66 @@ class ScrubBar(Gtk.DrawingArea):
         self._proxy_states[segment_index] = state
         self.queue_draw()
 
+    def set_frames(self, frames: list[dict]) -> None:
+        """Set frame thumbnails. Each dict: {timestamp, path}.
+
+        Loads thumbnails scaled to fit the bar height and caches as cairo surfaces.
+        """
+        self._frame_thumbs = []
+        thumb_h = BAR_HEIGHT - 4  # 2px margin top/bottom
+        thumb_w = int(thumb_h * 16 / 9)  # assume 16:9 aspect
+        for f in frames:
+            path = f.get("path")
+            ts = f.get("timestamp", 0)
+            if not path or not Path(path).exists():
+                continue
+            try:
+                pixbuf = GdkPixbuf.Pixbuf.new_from_file_at_scale(
+                    str(path), thumb_w, thumb_h, True
+                )
+                surface = self._pixbuf_to_surface(pixbuf)
+                self._frame_thumbs.append({
+                    "timestamp": ts,
+                    "surface": surface,
+                    "width": pixbuf.get_width(),
+                    "height": pixbuf.get_height(),
+                })
+            except Exception as e:
+                log.debug("Thumb load failed for %s: %s", path, e)
+        self.queue_draw()
+
+    def add_frame(self, timestamp: float, path: str) -> None:
+        """Add a single frame thumbnail incrementally."""
+        if not Path(path).exists():
+            return
+        thumb_h = BAR_HEIGHT - 4
+        thumb_w = int(thumb_h * 16 / 9)
+        try:
+            pixbuf = GdkPixbuf.Pixbuf.new_from_file_at_scale(path, thumb_w, thumb_h, True)
+            surface = self._pixbuf_to_surface(pixbuf)
+            self._frame_thumbs.append({
+                "timestamp": timestamp,
+                "surface": surface,
+                "width": pixbuf.get_width(),
+                "height": pixbuf.get_height(),
+            })
+            self.queue_draw()
+        except Exception as e:
+            log.debug("Thumb load failed for %s: %s", path, e)
+
+    @staticmethod
+    def _pixbuf_to_surface(pixbuf):
+        """Convert a GdkPixbuf to a cairo ImageSurface."""
+        w, h = pixbuf.get_width(), pixbuf.get_height()
+        has_alpha = pixbuf.get_has_alpha()
+        fmt = cairo.FORMAT_ARGB32 if has_alpha else cairo.FORMAT_RGB24
+        surface = cairo.ImageSurface(fmt, w, h)
+        cr = cairo.Context(surface)
+        Gdk.cairo_set_source_pixbuf(cr, pixbuf, 0, 0)
+        cr.paint()
+        surface.flush()
+        return surface
+
     # -- Drawing --
 
     def _draw(self, area, cr, width, height):
@@ -144,7 +214,31 @@ class ScrubBar(Gtk.DrawingArea):
                 cr.arc(x + w - 8, 8, 3, 0, 6.28)
                 cr.fill()
 
-        # Scene markers
+        # Frame thumbnails at their timestamp positions
+        for thumb in self._frame_thumbs:
+            tx = self._global_to_x(thumb["timestamp"], width)
+            tw, th = thumb["width"], thumb["height"]
+            # Center thumbnail on its timestamp, vertically centered in bar
+            x0 = tx - tw / 2
+            y0 = (height - th) / 2
+            cr.save()
+            # Dark outline for separation against any background
+            cr.set_source_rgba(0, 0, 0, 0.7)
+            cr.set_line_width(2)
+            cr.rectangle(x0 - 1, y0 - 1, tw + 2, th + 2)
+            cr.stroke()
+            # Thumbnail
+            cr.set_source_surface(thumb["surface"], x0, y0)
+            cr.rectangle(x0, y0, tw, th)
+            cr.fill()
+            # Bright inner border
+            cr.set_source_rgba(1, 1, 1, 0.5)
+            cr.set_line_width(1)
+            cr.rectangle(x0, y0, tw, th)
+            cr.stroke()
+            cr.restore()
+
+        # Scene markers (on top of thumbs)
         cr.set_source_rgb(*MARKER_COLOR)
         for ts in self._scene_markers:
             mx = self._global_to_x(ts, width)

cht/ui/timeline.py

@@ -210,6 +210,7 @@ class TimelineControls(Gtk.Box):
         else:
             self._live_btn.remove_css_class("suggested-action")
 
+        self._scrub_bar.set_duration(s.duration)
         self._scrub_bar.set_cursor(s.cursor)
         self._scrub_bar.set_scene_markers(s.scene_markers)
         self._time_label.set_text(self._fmt_time(s.cursor))

cht/ui/transcript_panel.py

@@ -173,6 +173,24 @@ class TranscriptPanel(Gtk.Box):
         self._selected.clear()
         self.emit("selection-changed")
 
+    def highlight_nearest(self, timestamp: float) -> None:
+        """Scroll to and briefly highlight the transcript segment closest to *timestamp*."""
+        if not self._order:
+            return
+        best_id = None
+        best_dist = float("inf")
+        for sid, ts in self._timestamps.items():
+            d = abs(ts - timestamp)
+            if d < best_dist:
+                best_dist = d
+                best_id = sid
+        if not best_id or best_id not in self._rows:
+            return
+        row = self._rows[best_id]
+        row.add_css_class("frame-highlight")
+        self._scroll_to_row(row)
+        GLib.timeout_add(400, lambda: row.remove_css_class("frame-highlight") or False)
+
     def clear(self):
         """Remove all items and reset state."""
         self._selected.clear()

cht/window.py

@@ -60,6 +60,7 @@ class ChtWindow(Adw.ApplicationWindow):
             on_transcript_ready=lambda segs: self._transcript_panel.add_items(segs),
             on_scene_marker=lambda ts: self._timeline.add_scene_marker(ts),
             on_recorder_restarted=lambda path: self._monitor.set_recording(path),
+            on_manifest_updated=lambda: self._update_scrub_bar_manifest(),
         )
 
         # Panels (own their selection state)
@@ -252,20 +253,33 @@ class ChtWindow(Adw.ApplicationWindow):
         log.info("Waiting for sender...")
 
     def _on_live_toggle(self):
-        pos = self._monitor.get_live_position()
-        self._timeline.toggle_live(live_player_pos=pos)
+        if self._timeline.state.live:
+            # Live → Scrub: don't load growing MKV, let user pick a segment
+            self._timeline.toggle_live(live_player_pos=self._monitor.get_live_position())
+            # Refresh manifest so scrub bar shows completed segments
+            self._update_scrub_bar_manifest()
+        else:
+            # Scrub → Live: restore recording path and resume
+            mgr = self._lifecycle.stream_mgr
+            if mgr:
+                self._monitor.set_recording(mgr.recording_path)
+            self._timeline.toggle_live()
 
     # -- Scrub --
 
     def _update_scrub_bar_manifest(self):
-        """Refresh the scrub bar with the current session's segment manifest."""
+        """Refresh the scrub bar with the current session's segment manifest and frames."""
         mgr = self._lifecycle.stream_mgr
         if not mgr:
             return
         self._manifest = load_segment_manifest(mgr.session_dir)
         if not self._manifest:
             self._manifest = rebuild_manifest(mgr.session_dir)
-        self._timeline_controls.scrub_bar.set_manifest(self._manifest)
+        scrub_bar = self._timeline_controls.scrub_bar
+        scrub_bar.set_manifest(self._manifest)
+        # Feed frame thumbnails to the scrub bar
+        frames = load_frame_index(mgr.frames_dir)
+        scrub_bar.set_frames([{"timestamp": f["timestamp"], "path": str(f["path"])} for f in frames])
 
     def _on_segment_activated(self, scrub_bar, segment_index):
         """User clicked a segment block — request its proxy."""
@@ -327,12 +341,16 @@ class ChtWindow(Adw.ApplicationWindow):
     def _scrub_tick(self):
         """Release throttle so next scrub motion can update monitor."""
         self._scrub_pending = False
+        cursor = self._timeline.state.cursor
         # Apply latest cursor position to monitor
-        seg, local_time = global_time_to_segment(
-            self._manifest, self._timeline.state.cursor
-        )
+        seg, local_time = global_time_to_segment(self._manifest, cursor)
         if seg:
             self._monitor.scrub_to(local_time)
+        # Sync waveform, time labels, etc. at throttled rate
+        self._timeline.emit("changed")
+        # Highlight nearest frame/transcript
+        self._frames_panel.highlight_nearest(cursor)
+        self._transcript_panel.highlight_nearest(cursor)
         return False
 
     def _capture_at_scrub_position(self):
@@ -583,6 +601,10 @@ class ChtWindow(Adw.ApplicationWindow):
             self._frames_panel.load_items(items)
             self._known_frames = {item["id"] for item in items}
             self._agent_output.append(f"  Loaded {len(items)} frame thumbnails.\n")
+            # Update scrub bar thumbnails
+            self._timeline_controls.scrub_bar.set_frames(
+                [{"timestamp": e["timestamp"], "path": str(e["path"])} for e in entries]
+            )
 
     def _load_existing_transcript(self):
         if not self._lifecycle.stream_mgr:
@@ -608,6 +630,7 @@ class ChtWindow(Adw.ApplicationWindow):
                 pixbuf = GdkPixbuf.Pixbuf.new_from_file_at_scale(str(entry["path"]), 256, 144, True)
                 auto = not self._transcript_panel.has_selection
                 self._frames_panel.add_item(fid, pixbuf, entry["timestamp"], auto_select=auto)
+                self._timeline_controls.scrub_bar.add_frame(entry["timestamp"], str(entry["path"]))
             except Exception as e:
                 log.warning("Thumbnail load failed for %s: %s", fid, e)
         return True