Set default timeline mode based on activity

daw-backend/src/audio/engine.rs

@@ -27,7 +27,7 @@ pub struct Engine {
     project: Project,
     audio_pool: AudioClipPool,
     buffer_pool: BufferPool,
-    playhead: u64,          // Playhead position in samples
+    playhead: i64,          // Playhead position in samples (may be negative during count-in pre-roll)
     sample_rate: u32,
     playing: bool,
     channels: u32,
@@ -74,6 +74,10 @@ pub struct Engine {
     // MIDI recording state
     midi_recording_state: Option<MidiRecordingState>,
 
+    // Currently held MIDI notes per track (note -> velocity), updated on NoteOn/NoteOff
+    // Used to inject held notes when recording starts mid-press (e.g. after count-in)
+    midi_held_notes: HashMap<TrackId, HashMap<u8, u8>>,
+
     // MIDI input manager for external MIDI devices
     midi_input_manager: Option<MidiInputManager>,
 
@@ -160,6 +164,7 @@ impl Engine {
             recording_mirror_tx: None,
             recording_progress_counter: 0,
             midi_recording_state: None,
+            midi_held_notes: HashMap::new(),
             midi_input_manager: None,
             metronome: Metronome::new(sample_rate),
             recording_sample_buffer: Vec::with_capacity(4096),
@@ -396,17 +401,18 @@ impl Engine {
             );
 
             // Update playhead (convert total samples to frames)
-            self.playhead += (output.len() / self.channels as usize) as u64;
+            self.playhead += (output.len() / self.channels as usize) as i64;
 
-            // Update atomic playhead for UI reads
+            // Update atomic playhead for UI reads (clamped to 0; negative = count-in pre-roll)
             self.playhead_atomic
-                .store(self.playhead, Ordering::Relaxed);
+                .store(self.playhead.max(0) as u64, Ordering::Relaxed);
 
             // Send periodic position updates
             self.frames_since_last_event += output.len() / self.channels as usize;
             if self.frames_since_last_event >= self.event_interval_frames / self.channels as usize
             {
-                let position_seconds = self.playhead as f64 / self.sample_rate as f64;
+                // Clamp to 0 during count-in pre-roll (negative playhead = before project start)
+                let position_seconds = self.playhead.max(0) as f64 / self.sample_rate as f64;
                 let _ = self
                     .event_tx
                     .push(AudioEvent::PlaybackPosition(position_seconds));
@@ -692,17 +698,17 @@ impl Engine {
                 self.project.stop_all_notes();
             }
             Command::Seek(seconds) => {
-                let frames = (seconds * self.sample_rate as f64) as u64;
+                self.playhead = (seconds * self.sample_rate as f64) as i64;
-                self.playhead = frames;
+                // Clamp to 0 for atomic/disk-reader; negative = count-in pre-roll (no disk reads needed)
-                self.playhead_atomic
+                let clamped = self.playhead.max(0) as u64;
-                    .store(self.playhead, Ordering::Relaxed);
+                self.playhead_atomic.store(clamped, Ordering::Relaxed);
                 // Stop all MIDI notes when seeking to prevent stuck notes
                 self.project.stop_all_notes();
                 // Reset all node graphs to clear effect buffers (echo, reverb, etc.)
                 self.project.reset_all_graphs();
                 // Notify disk reader to refill buffers from new position
                 if let Some(ref mut dr) = self.disk_reader {
-                    dr.send(crate::audio::disk_reader::DiskReaderCommand::Seek { frame: frames });
+                    dr.send(crate::audio::disk_reader::DiskReaderCommand::Seek { frame: clamped });
                 }
             }
             Command::SetTrackVolume(track_id, volume) => {
@@ -1212,6 +1218,9 @@ impl Engine {
                 // Emit event to UI for visual feedback
                 let _ = self.event_tx.push(AudioEvent::NoteOn(note, velocity));
 
+                // Track held notes so count-in recording can inject them at start_time
+                self.midi_held_notes.entry(track_id).or_default().insert(note, velocity);
+
                 // If MIDI recording is active on this track, capture the event
                 if let Some(recording) = &mut self.midi_recording_state {
                     if recording.track_id == track_id {
@@ -1230,6 +1239,11 @@ impl Engine {
                 // Emit event to UI for visual feedback
                 let _ = self.event_tx.push(AudioEvent::NoteOff(note));
 
+                // Remove from held notes tracking
+                if let Some(track_notes) = self.midi_held_notes.get_mut(&track_id) {
+                    track_notes.remove(&note);
+                }
+
                 // If MIDI recording is active on this track, capture the event
                 if let Some(recording) = &mut self.midi_recording_state {
                     if recording.track_id == track_id {
@@ -3038,7 +3052,17 @@ impl Engine {
         // Check if track exists and is a MIDI track
         if let Some(crate::audio::track::TrackNode::Midi(_)) = self.project.get_track_mut(track_id) {
             // Create MIDI recording state
-            let recording_state = MidiRecordingState::new(track_id, clip_id, start_time);
+            let mut recording_state = MidiRecordingState::new(track_id, clip_id, start_time);
+
+            // Inject any notes currently held on this track (pressed during count-in pre-roll)
+            // so they start at t=0 of the recording rather than being lost
+            if let Some(held) = self.midi_held_notes.get(&track_id) {
+                for (&note, &velocity) in held {
+                    eprintln!("[MIDI_RECORDING] Injecting held note {} vel {} at start_time {:.3}s", note, velocity, start_time);
+                    recording_state.note_on(note, velocity, start_time);
+                }
+            }
+
             self.midi_recording_state = Some(recording_state);
 
             eprintln!("[MIDI_RECORDING] Started MIDI recording on track {} for clip {}", track_id, clip_id);

daw-backend/src/audio/metronome.rs

@@ -107,7 +107,7 @@ impl Metronome {
     pub fn process(
         &mut self,
         output: &mut [f32],
-        playhead_samples: u64,
+        playhead_samples: i64,
         playing: bool,
         sample_rate: u32,
         channels: u32,
@@ -120,20 +120,21 @@ impl Metronome {
         let frames = output.len() / channels as usize;
 
         for frame in 0..frames {
-            let current_sample = playhead_samples + frame as u64;
+            let current_sample = playhead_samples + frame as i64;
 
             // Calculate current beat number
             let current_time_seconds = current_sample as f64 / sample_rate as f64;
             let beats_per_second = self.bpm as f64 / 60.0;
             let current_beat = (current_time_seconds * beats_per_second).floor() as i64;
 
-            // Check if we crossed a beat boundary
+            // Check if we crossed a beat boundary (including negative beats during count-in pre-roll)
-            if current_beat != self.last_beat && current_beat >= 0 {
+            if current_beat != self.last_beat {
                 self.last_beat = current_beat;
 
                 // Determine which click to play.
                 // Beat 0 of each measure gets the accent (high click).
-                let beat_in_measure = (current_beat as u32 % self.time_signature_numerator) as usize;
+                // Use rem_euclid so negative beat numbers map correctly (e.g. -4 % 4 = 0).
+                let beat_in_measure = current_beat.rem_euclid(self.time_signature_numerator as i64) as usize;
                 self.playing_high_click = beat_in_measure == 0;
                 self.click_position = 0;  // Start from beginning of click
             }

daw-backend/src/audio/recording.rs

@@ -213,7 +213,6 @@ impl MidiRecordingState {
 
     /// Handle a MIDI note on event
     pub fn note_on(&mut self, note: u8, velocity: u8, absolute_time: f64) {
-        // Store this note as active
         self.active_notes.insert(note, ActiveMidiNote {
             note,
             velocity,
@@ -225,14 +224,21 @@ impl MidiRecordingState {
     pub fn note_off(&mut self, note: u8, absolute_time: f64) {
         // Find the matching noteOn
         if let Some(active_note) = self.active_notes.remove(&note) {
-            // Calculate relative time offset and duration
+            // If the note was fully released before the recording start (e.g. during count-in
-            let time_offset = active_note.start_time - self.start_time;
+            // pre-roll), discard it — only notes still held at the clip start are kept.
-            let duration = absolute_time - active_note.start_time;
+            if absolute_time <= self.start_time {
+                return;
+            }
+
+            // Clamp note start to clip start: notes held across the recording boundary
+            // are treated as starting at the clip position.
+            let note_start = active_note.start_time.max(self.start_time);
+            let time_offset = note_start - self.start_time;
+            let duration = absolute_time - note_start;
 
             eprintln!("[MIDI_RECORDING_STATE] Completing note {}: note_start={:.3}s, note_end={:.3}s, recording_start={:.3}s, time_offset={:.3}s, duration={:.3}s",
-                      note, active_note.start_time, absolute_time, self.start_time, time_offset, duration);
+                      note, note_start, absolute_time, self.start_time, time_offset, duration);
 
-            // Add to completed notes
             self.completed_notes.push((
                 time_offset,
                 active_note.note,
@@ -258,8 +264,9 @@ impl MidiRecordingState {
     pub fn get_notes_with_active(&self, current_time: f64) -> Vec<(f64, u8, u8, f64)> {
         let mut notes = self.completed_notes.clone();
         for active in self.active_notes.values() {
-            let time_offset = active.start_time - self.start_time;
+            let note_start = active.start_time.max(self.start_time);
-            let provisional_dur = (current_time - active.start_time).max(0.0);
+            let time_offset = note_start - self.start_time;
+            let provisional_dur = (current_time - note_start).max(0.0);
             notes.push((time_offset, active.note, active.velocity, provisional_dur));
         }
         notes
@@ -273,15 +280,13 @@ impl MidiRecordingState {
     /// Close out all active notes at the given time
     /// This should be called when stopping recording to end any held notes
     pub fn close_active_notes(&mut self, end_time: f64) {
-        // Collect all active notes and close them
         let active_notes: Vec<_> = self.active_notes.drain().collect();
 
         for (_note_num, active_note) in active_notes {
-            // Calculate relative time offset and duration
+            let note_start = active_note.start_time.max(self.start_time);
-            let time_offset = active_note.start_time - self.start_time;
+            let time_offset = note_start - self.start_time;
-            let duration = end_time - active_note.start_time;
+            let duration = end_time - note_start;
 
-            // Add to completed notes
             self.completed_notes.push((
                 time_offset,
                 active_note.note,

lightningbeam-ui/lightningbeam-core/src/document.rs

@@ -133,6 +133,15 @@ impl Default for TimeSignature {
 
 fn default_bpm() -> f64 { 120.0 }
 
+/// How time is displayed in the timeline
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Serialize, Deserialize, Default)]
+pub enum TimelineMode {
+    #[default]
+    Seconds,
+    Measures,
+    Frames,
+}
+
 /// Asset category for folder tree access
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
 pub enum AssetCategory {
@@ -226,6 +235,10 @@ pub struct Document {
     #[serde(default)]
     pub script_folders: AssetFolderTree,
 
+    /// How time is displayed in the timeline (saved with document)
+    #[serde(default)]
+    pub timeline_mode: TimelineMode,
+
     /// Current UI layout state (serialized for save/load)
     #[serde(default, skip_serializing_if = "Option::is_none")]
     pub ui_layout: Option<LayoutNode>,
@@ -270,6 +283,7 @@ impl Default for Document {
             effect_folders: AssetFolderTree::new(),
             script_definitions: HashMap::new(),
             script_folders: AssetFolderTree::new(),
+            timeline_mode: TimelineMode::Seconds,
             ui_layout: None,
             ui_layout_base: None,
             current_time: 0.0,

lightningbeam-ui/lightningbeam-editor/src/keymap.rs

@@ -339,6 +339,7 @@ impl From<MenuAction> for AppAction {
             MenuAction::AddShapeTween => Self::AddShapeTween,
             MenuAction::ReturnToStart => Self::ReturnToStart,
             MenuAction::Play => Self::Play,
+            MenuAction::ToggleCountIn => Self::Play, // not directly mappable to AppAction
             MenuAction::ZoomIn => Self::ZoomIn,
             MenuAction::ZoomOut => Self::ZoomOut,
             MenuAction::ActualSize => Self::ActualSize,

lightningbeam-ui/lightningbeam-editor/src/main.rs

@@ -856,6 +856,7 @@ struct EditorApp {
     armed_layers: HashSet<Uuid>,
     is_recording: bool,                   // Whether recording is currently active
     metronome_enabled: bool,              // Whether metronome clicks during recording
+    count_in_enabled: bool,              // Whether count-in fires before recording
     recording_clips: HashMap<Uuid, u32>,  // layer_id -> backend clip_id during recording
     recording_start_time: f64,            // Playback time when recording started
     recording_layer_ids: Vec<Uuid>,       // Layers being recorded to (for creating clips)
@@ -1128,6 +1129,7 @@ impl EditorApp {
             armed_layers: HashSet::new(),     // No layers explicitly armed
             is_recording: false,              // Not recording initially
             metronome_enabled: false,         // Metronome off by default
+            count_in_enabled: false,         // Count-in off by default
             recording_clips: HashMap::new(),  // No active recording clips
             recording_start_time: 0.0,        // Will be set when recording starts
             recording_layer_ids: Vec::new(),  // Will be populated when recording starts
@@ -1488,6 +1490,13 @@ impl EditorApp {
             }
         };
 
+        // Set default timeline mode based on activity
+        document.timeline_mode = match layout_index {
+            2 => lightningbeam_core::document::TimelineMode::Measures, // Music
+            1 => lightningbeam_core::document::TimelineMode::Seconds,  // Video
+            _ => lightningbeam_core::document::TimelineMode::Frames,   // Animation, Painting, etc.
+        };
+
         // Reset action executor with new document
         self.action_executor = lightningbeam_core::action::ActionExecutor::new(document);
 
@@ -3577,6 +3586,12 @@ impl EditorApp {
                 println!("Menu: Play");
                 // TODO: Implement play/pause
             }
+            MenuAction::ToggleCountIn => {
+                // Only effective when metronome is enabled (count-in requires a click track)
+                if self.metronome_enabled {
+                    self.count_in_enabled = !self.count_in_enabled;
+                }
+            }
 
             // View menu
             MenuAction::ZoomIn => {
@@ -5632,9 +5647,28 @@ impl eframe::App for EditorApp {
             if let Some(menu_system) = &self.menu_system {
                 let recent_files = self.config.get_recent_files();
                 let layout_names: Vec<String> = self.layouts.iter().map(|l| l.name.clone()).collect();
+
+                // Determine timeline measures mode for conditional menu items
+                let timeline_is_measures = self.pane_instances.values().any(|p| {
+                    if let panes::PaneInstance::Timeline(t) = p { t.is_measures_mode() } else { false }
+                });
+
+                // Checked actions show "✔ Label"; hidden actions are not rendered at all
+                let checked: &[crate::menu::MenuAction] = if self.count_in_enabled && self.metronome_enabled {
+                    &[crate::menu::MenuAction::ToggleCountIn]
+                } else {
+                    &[]
+                };
+                let hidden: &[crate::menu::MenuAction] = if timeline_is_measures && self.metronome_enabled {
+                    &[]
+                } else {
+                    &[crate::menu::MenuAction::ToggleCountIn]
+                };
+
                 if let Some(action) = menu_system.render_egui_menu_bar(
                     ui, &recent_files, Some(&self.keymap),
                     &layout_names, self.current_layout_index,
+                    checked, hidden,
                 ) {
                     self.handle_menu_action(action);
                 }
@@ -5774,6 +5808,7 @@ impl eframe::App for EditorApp {
                     is_playing: &mut self.is_playing,
                     is_recording: &mut self.is_recording,
                     metronome_enabled: &mut self.metronome_enabled,
+                    count_in_enabled: &mut self.count_in_enabled,
                     recording_clips: &mut self.recording_clips,
                     recording_start_time: &mut self.recording_start_time,
                     recording_layer_ids: &mut self.recording_layer_ids,

lightningbeam-ui/lightningbeam-editor/src/menu.rs

@@ -324,6 +324,7 @@ pub enum MenuAction {
     AddShapeTween,
     ReturnToStart,
     Play,
+    ToggleCountIn,
 
     // View menu
     ZoomIn,
@@ -422,6 +423,7 @@ impl MenuItemDef {
     const ADD_SHAPE_TWEEN: Self = Self { label: "Add Shape Tween", action: MenuAction::AddShapeTween, shortcut: None };
     const RETURN_TO_START: Self = Self { label: "Return to start", action: MenuAction::ReturnToStart, shortcut: None };
     const PLAY: Self = Self { label: "Play", action: MenuAction::Play, shortcut: None };
+    const COUNT_IN: Self = Self { label: "Count In", action: MenuAction::ToggleCountIn, shortcut: None };
 
     // View menu items
     const ZOOM_IN: Self = Self { label: "Zoom In", action: MenuAction::ZoomIn, shortcut: Some(Shortcut::new(ShortcutKey::Equals, CTRL, NO_SHIFT, NO_ALT)) };
@@ -548,6 +550,8 @@ impl MenuItemDef {
                     MenuDef::Separator,
                     MenuDef::Item(&Self::RETURN_TO_START),
                     MenuDef::Item(&Self::PLAY),
+                    MenuDef::Separator,
+                    MenuDef::Item(&Self::COUNT_IN),
                 ],
             },
             // View menu
@@ -805,6 +809,8 @@ impl MenuSystem {
         keymap: Option<&crate::keymap::KeymapManager>,
         layout_names: &[String],
         current_layout_index: usize,
+        checked_actions: &[MenuAction],
+        hidden_actions: &[MenuAction],
     ) -> Option<MenuAction> {
         let mut action = None;
         let ctx = ui.ctx().clone();
@@ -819,7 +825,7 @@ impl MenuSystem {
                     let response = ui.button(*label);
                     let popup_id = egui::Popup::default_response_id(&response);
                     button_entries.push((response, popup_id, menu_def));
-                } else if let Some(a) = self.render_menu_def(ui, menu_def, recent_files, keymap, layout_names, current_layout_index) {
+                } else if let Some(a) = self.render_menu_def(ui, menu_def, recent_files, keymap, layout_names, current_layout_index, checked_actions, hidden_actions) {
                     action = Some(a);
                 }
             }
@@ -847,7 +853,7 @@ impl MenuSystem {
                         ui.set_width(min_width);
                         let mut a = None;
                         for child in *children {
-                            if let Some(result) = self.render_menu_def(ui, child, recent_files, keymap, layout_names, current_layout_index) {
+                            if let Some(result) = self.render_menu_def(ui, child, recent_files, keymap, layout_names, current_layout_index, checked_actions, hidden_actions) {
                                 a = Some(result);
                                 ui.close();
                             }
@@ -875,10 +881,15 @@ impl MenuSystem {
         keymap: Option<&crate::keymap::KeymapManager>,
         layout_names: &[String],
         current_layout_index: usize,
+        checked_actions: &[MenuAction],
+        hidden_actions: &[MenuAction],
     ) -> Option<MenuAction> {
         match def {
             MenuDef::Item(item_def) => {
-                if Self::render_menu_item(ui, item_def, keymap) {
+                if hidden_actions.contains(&item_def.action) {
+                    return None;
+                }
+                if Self::render_menu_item(ui, item_def, keymap, checked_actions) {
                     Some(item_def.action)
                 } else {
                     None
@@ -914,7 +925,7 @@ impl MenuSystem {
                         } else if *label == "Layout" {
                             let mut action = None;
                             for child in *children {
-                                if let Some(a) = self.render_menu_def(ui, child, recent_files, keymap, layout_names, current_layout_index) {
+                                if let Some(a) = self.render_menu_def(ui, child, recent_files, keymap, layout_names, current_layout_index, checked_actions, hidden_actions) {
                                     action = Some(a);
                                     ui.close();
                                 }
@@ -937,7 +948,7 @@ impl MenuSystem {
                         } else {
                             let mut action = None;
                             for child in *children {
-                                if let Some(a) = self.render_menu_def(ui, child, recent_files, keymap, layout_names, current_layout_index) {
+                                if let Some(a) = self.render_menu_def(ui, child, recent_files, keymap, layout_names, current_layout_index, checked_actions, hidden_actions) {
                                     action = Some(a);
                                     ui.close();
                                 }
@@ -951,7 +962,7 @@ impl MenuSystem {
     }
 
     /// Render a single menu item with label and shortcut
-    fn render_menu_item(ui: &mut egui::Ui, def: &MenuItemDef, keymap: Option<&crate::keymap::KeymapManager>) -> bool {
+    fn render_menu_item(ui: &mut egui::Ui, def: &MenuItemDef, keymap: Option<&crate::keymap::KeymapManager>, checked_actions: &[MenuAction]) -> bool {
         // Look up shortcut from keymap if available, otherwise use static default
         let effective_shortcut = if let Some(km) = keymap {
             if let Ok(app_action) = crate::keymap::AppAction::try_from(def.action) {
@@ -987,10 +998,15 @@ impl MenuSystem {
                 ui.visuals().widgets.inactive.text_color()
             };
             let label_pos = rect.min + egui::vec2(4.0, (rect.height() - 14.0) / 2.0);
+            let label = if checked_actions.contains(&def.action) {
+                format!("✔ {}", def.label)
+            } else {
+                def.label.to_owned()
+            };
             ui.painter().text(
                 label_pos,
                 egui::Align2::LEFT_TOP,
-                def.label,
+                label,
                 egui::FontId::proportional(14.0),
                 text_color,
             );

lightningbeam-ui/lightningbeam-editor/src/panes/mod.rs

@@ -213,6 +213,7 @@ pub struct SharedPaneState<'a> {
     /// Recording state
     pub is_recording: &'a mut bool,  // Whether recording is currently active
     pub metronome_enabled: &'a mut bool,  // Whether metronome clicks during recording
+    pub count_in_enabled: &'a mut bool,  // Whether count-in fires before recording
     pub recording_clips: &'a mut std::collections::HashMap<uuid::Uuid, u32>, // layer_id -> clip_id
     pub recording_start_time: &'a mut f64,  // Playback time when recording started
     pub recording_layer_ids: &'a mut Vec<uuid::Uuid>,  // Layers being recorded to

lightningbeam-ui/lightningbeam-editor/src/panes/timeline.rs

@@ -136,13 +136,7 @@ enum ClipDragType {
     LoopExtendLeft,
 }
 
-/// How time is displayed in the ruler and header
+use lightningbeam_core::document::TimelineMode;
-#[derive(Debug, Clone, Copy, PartialEq)]
-enum TimeDisplayFormat {
-    Seconds,
-    Measures,
-    Frames,
-}
 
 /// State for an in-progress layer header drag-to-reorder operation.
 struct LayerDragState {
@@ -194,7 +188,7 @@ pub struct TimelinePane {
     context_menu_clip: Option<(Option<uuid::Uuid>, egui::Pos2)>,
 
     /// Whether to display time as seconds or measures
-    time_display_format: TimeDisplayFormat,
+    time_display_format: TimelineMode,
 
     /// Waveform upload progress: pool_index -> frames uploaded so far.
     /// Tracks chunked GPU uploads across frames to avoid hitches.
@@ -223,6 +217,16 @@ pub struct TimelinePane {
     automation_topology_generation: u64,
     /// Cached metronome icon texture (loaded on first use)
     metronome_icon: Option<egui::TextureHandle>,
+    /// Count-in pre-roll state: set when count-in is active, cleared when recording fires
+    pending_recording_start: Option<PendingRecordingStart>,
+}
+
+/// Deferred recording start created during count-in pre-roll
+struct PendingRecordingStart {
+    /// Original playhead position — where clips will be placed in the timeline
+    original_playhead: f64,
+    /// Transport time at which to fire the actual recording commands
+    trigger_time: f64,
 }
 
 /// Check if a clip type can be dropped on a layer type
@@ -663,7 +667,7 @@ impl TimelinePane {
             mousedown_pos: None,
             layer_control_clicked: false,
             context_menu_clip: None,
-            time_display_format: TimeDisplayFormat::Seconds,
+            time_display_format: TimelineMode::Seconds,
             waveform_upload_progress: std::collections::HashMap::new(),
             video_thumbnail_textures: std::collections::HashMap::new(),
             layer_drag: None,
@@ -675,9 +679,15 @@ impl TimelinePane {
             automation_cache_generation: u64::MAX,
             automation_topology_generation: u64::MAX,
             metronome_icon: None,
+            pending_recording_start: None,
         }
     }
 
+    /// Returns true if the timeline is currently in Measures display mode.
+    pub fn is_measures_mode(&self) -> bool {
+        self.time_display_format == TimelineMode::Measures
+    }
+
     /// Execute a view action with the given parameters
     /// Called from main.rs after determining this is the best handler
     #[allow(dead_code)] // Mirrors StagePane; wiring in main.rs pending (see TODO at view action dispatch)
@@ -910,6 +920,37 @@ impl TimelinePane {
         });
 
         let start_time = *shared.playback_time;
+
+        // Count-in: seek back N beats, start transport + metronome, defer ALL recording commands.
+        // Must happen before Step 4 so no clips or backend recordings are created yet.
+        if *shared.count_in_enabled
+            && *shared.metronome_enabled
+            && self.time_display_format == TimelineMode::Measures
+        {
+            let (bpm, beats_per_measure) = {
+                let doc = shared.action_executor.document();
+                (doc.bpm, doc.time_signature.numerator as f64)
+            };
+            let count_in_duration = beats_per_measure * (60.0 / bpm);
+            let seek_to = start_time - count_in_duration; // may be negative
+
+            if let Some(controller_arc) = shared.audio_controller {
+                let mut controller = controller_arc.lock().unwrap();
+                controller.seek(seek_to);
+                controller.set_metronome_enabled(true);
+                if !*shared.is_playing {
+                    controller.play();
+                    *shared.is_playing = true;
+                }
+            }
+
+            self.pending_recording_start = Some(PendingRecordingStart {
+                original_playhead: start_time,
+                trigger_time: start_time,
+            });
+            return; // Recording commands are deferred — check_pending_recording_start fires them
+        }
+
         shared.recording_layer_ids.clear();
 
         // Step 4: Dispatch recording for each candidate
@@ -986,8 +1027,8 @@ impl TimelinePane {
             return;
         }
 
-        // Auto-start playback if needed, and enable metronome if requested.
+        // No count-in (or deferred re-call from check_pending_recording_start):
-        // Metronome must be enabled BEFORE play() so beat 0 is not missed.
+        // Start immediately. Metronome must be enabled BEFORE play() so beat 0 is not missed.
         if let Some(controller_arc) = shared.audio_controller {
             let mut controller = controller_arc.lock().unwrap();
             if *shared.metronome_enabled {
@@ -1005,7 +1046,31 @@ impl TimelinePane {
     }
 
     /// Stop all active recordings
+    /// Called every frame; fires deferred recording commands once the count-in pre-roll ends.
+    fn check_pending_recording_start(&mut self, shared: &mut SharedPaneState) {
+        let Some(ref pending) = self.pending_recording_start else { return };
+        if !*shared.is_playing || *shared.playback_time < pending.trigger_time {
+            return;
+        }
+        let original_playhead = pending.original_playhead;
+        self.pending_recording_start = None;
+
+        // Re-run start_recording with playback_time temporarily set to the original playhead
+        // so it captures the correct start_time and places clips at the right position.
+        // Disable count_in_enabled so start_recording takes the immediate path (no re-seek).
+        let saved_time = *shared.playback_time;
+        let saved_count_in = *shared.count_in_enabled;
+        *shared.playback_time = original_playhead;
+        *shared.count_in_enabled = false;
+        self.start_recording(shared);
+        *shared.playback_time = saved_time;
+        *shared.count_in_enabled = saved_count_in;
+    }
+
     fn stop_recording(&mut self, shared: &mut SharedPaneState) {
+        // Cancel any in-progress count-in
+        self.pending_recording_start = None;
+
         let stop_wall = std::time::Instant::now();
         eprintln!("[STOP] stop_recording called at {:?}", stop_wall);
 
@@ -1287,8 +1352,8 @@ impl TimelinePane {
         framerate: f64,
     ) -> Option<f64> {
         match self.time_display_format {
-            TimeDisplayFormat::Frames => Some(1.0 / framerate),
+            TimelineMode::Frames => Some(1.0 / framerate),
-            TimeDisplayFormat::Measures => {
+            TimelineMode::Measures => {
                 use lightningbeam_core::beat_time::{beat_duration, measure_duration};
                 let beat = beat_duration(bpm);
                 let measure = measure_duration(bpm, time_sig);
@@ -1308,7 +1373,7 @@ impl TimelinePane {
                 }
                 Some(measure)
             }
-            TimeDisplayFormat::Seconds => None,
+            TimelineMode::Seconds => None,
         }
     }
 
@@ -1385,7 +1450,7 @@ impl TimelinePane {
         let text_color = text_style.text_color.unwrap_or(egui::Color32::from_gray(200));
 
         match self.time_display_format {
-            TimeDisplayFormat::Seconds => {
+            TimelineMode::Seconds => {
                 let interval = self.calculate_ruler_interval();
                 let start_time = (self.viewport_start_time / interval).floor() * interval;
                 let end_time = self.x_to_time(rect.width());
@@ -1418,7 +1483,7 @@ impl TimelinePane {
                     time += interval;
                 }
             }
-            TimeDisplayFormat::Measures => {
+            TimelineMode::Measures => {
                 let beats_per_second = bpm / 60.0;
                 let beat_dur = lightningbeam_core::beat_time::beat_duration(bpm);
                 let bpm_count = time_sig.numerator;
@@ -1471,7 +1536,7 @@ impl TimelinePane {
                     }
                 }
             }
-            TimeDisplayFormat::Frames => {
+            TimelineMode::Frames => {
                 let interval = self.calculate_ruler_interval_frames(framerate);
                 let start_frame = (self.viewport_start_time.max(0.0) * framerate).floor() as i64;
                 let end_frame = (self.x_to_time(rect.width()) * framerate).ceil() as i64;
@@ -2509,7 +2574,7 @@ impl TimelinePane {
 
             // Grid lines matching ruler
             match self.time_display_format {
-                TimeDisplayFormat::Seconds => {
+                TimelineMode::Seconds => {
                     let interval = self.calculate_ruler_interval();
                     let start_time = (self.viewport_start_time / interval).floor() * interval;
                     let end_time = self.x_to_time(rect.width());
@@ -2526,7 +2591,7 @@ impl TimelinePane {
                         time += interval;
                     }
                 }
-                TimeDisplayFormat::Measures => {
+                TimelineMode::Measures => {
                     let beats_per_second = document.bpm / 60.0;
                     let bpm_count = document.time_signature.numerator;
                     let start_beat = (self.viewport_start_time.max(0.0) * beats_per_second).floor() as i64;
@@ -2544,7 +2609,7 @@ impl TimelinePane {
                         );
                     }
                 }
-                TimeDisplayFormat::Frames => {
+                TimelineMode::Frames => {
                     let framerate = document.framerate;
                     let px_per_frame = self.pixels_per_second / framerate as f32;
 
@@ -4652,6 +4717,12 @@ impl TimelinePane {
 
 impl PaneRenderer for TimelinePane {
     fn render_header(&mut self, ui: &mut egui::Ui, shared: &mut SharedPaneState) -> bool {
+        // Sync timeline mode from document (document is source of truth)
+        self.time_display_format = shared.action_executor.document().timeline_mode;
+
+        // Fire deferred recording commands once count-in pre-roll has elapsed
+        self.check_pending_recording_start(shared);
+
         ui.spacing_mut().item_spacing.x = 2.0; // Small spacing between button groups
 
         // Main playback controls group
@@ -4749,7 +4820,7 @@ impl PaneRenderer for TimelinePane {
                 }
 
                 // Metronome toggle — only visible in Measures mode
-                if self.time_display_format == TimeDisplayFormat::Measures {
+                if self.time_display_format == TimelineMode::Measures {
                     ui.add_space(4.0);
 
                     let metro_tint = if *shared.metronome_enabled {
@@ -4804,6 +4875,7 @@ impl PaneRenderer for TimelinePane {
                             }
                         }
                     }
+
                 }
             });
         });
@@ -4822,10 +4894,10 @@ impl PaneRenderer for TimelinePane {
             };
 
             match self.time_display_format {
-                TimeDisplayFormat::Seconds => {
+                TimelineMode::Seconds => {
                     ui.colored_label(text_color, format!("Time: {:.2}s / {:.2}s", *shared.playback_time, self.duration));
                 }
-                TimeDisplayFormat::Measures => {
+                TimelineMode::Measures => {
                     let time_sig = lightningbeam_core::document::TimeSignature { numerator: time_sig_num, denominator: time_sig_den };
                     let pos = lightningbeam_core::beat_time::time_to_measure(
                         *shared.playback_time, bpm, &time_sig,
@@ -4836,7 +4908,7 @@ impl PaneRenderer for TimelinePane {
                         time_sig_num, time_sig_den,
                     ));
                 }
-                TimeDisplayFormat::Frames => {
+                TimelineMode::Frames => {
                     let current_frame = (*shared.playback_time * framerate).floor() as i64 + 1;
                     let total_frames = (self.duration * framerate).ceil() as i64;
                     ui.colored_label(text_color, format!(
@@ -4855,16 +4927,18 @@ impl PaneRenderer for TimelinePane {
             // Time display format toggle
             egui::ComboBox::from_id_salt("time_format")
                 .selected_text(match self.time_display_format {
-                    TimeDisplayFormat::Seconds => "Seconds",
+                    TimelineMode::Seconds => "Seconds",
-                    TimeDisplayFormat::Measures => "Measures",
+                    TimelineMode::Measures => "Measures",
-                    TimeDisplayFormat::Frames => "Frames",
+                    TimelineMode::Frames => "Frames",
                 })
                 .width(80.0)
                 .show_ui(ui, |ui| {
-                    ui.selectable_value(&mut self.time_display_format, TimeDisplayFormat::Seconds, "Seconds");
+                    ui.selectable_value(&mut self.time_display_format, TimelineMode::Seconds, "Seconds");
-                    ui.selectable_value(&mut self.time_display_format, TimeDisplayFormat::Measures, "Measures");
+                    ui.selectable_value(&mut self.time_display_format, TimelineMode::Measures, "Measures");
-                    ui.selectable_value(&mut self.time_display_format, TimeDisplayFormat::Frames, "Frames");
+                    ui.selectable_value(&mut self.time_display_format, TimelineMode::Frames, "Frames");
                 });
+            // Write change back to document so it persists and is the source of truth
+            shared.action_executor.document_mut().timeline_mode = self.time_display_format;
 
             ui.separator();