refactor: split Chat out of MainViewModel — Commit 10/12

MainViewModel.Chat.cs (194 lines) takes the YouTube chat overlay: ChatMessages
(+500 cap, clear-on-fade), OnChatMessageReceived (dispatcher marshal,
mock→real preview switch), chat fade timer (ResetChatFadeTimer), the ChatBox
render paths (RenderChatBox for the live compositor, UpdateChatBoxPreview for
the editor preview), the mock preview loop (MockChatMessages/StartMockChatPreview/
StopMockChatPreview/RunMockChatPreviewAsync/_mockChatCts), UpdateActiveChatBoxPreviews,
CanAddYouTubeChat (one-per-layout gate) and ShowChatInactiveMessage. Core drops
1119 -> 940 lines. Ctor wiring (MessageReceived hookup, ChatBoxRenderer ctor,
LoadLayout preview start, dispose) stays in core; ResolveOutputFrame (core)
still calls RenderChatBox cross-partial.

Zero behavior change; build 0 warnings; 246 pass, only the 2 known failures.
Docs: index.md Chat row added + core row trimmed in the same commit.

ViewModels/MainViewModel.Chat.cs

@@ -0,0 +1,194 @@
+using System.Collections.ObjectModel;
+using System.Windows.Media;
+using System.Windows.Media.Imaging;
+using System.Windows.Threading;
+using ytLive.Helpers;
+using ytLive.Models;
+using ytLive.Services;
+
+namespace ytLive.ViewModels;
+
+public partial class MainViewModel : ViewModelBase
+{
+
+    private readonly ChatBoxRenderer _chatBoxRenderer;
+
+    // Mock chat messages for the ChatBox preview — branded placeholders so the
+    // creator sees where the overlay lands before going live.
+    private static readonly IReadOnlyList<ChatMessage> MockChatMessages = new[]
+    {
+        new ChatMessage { AuthorName = "LlamaCasty", Message = "welcome to the stream!", Timestamp = DateTime.Now.AddMinutes(-4), IsMember = true },
+        new ChatMessage { AuthorName = "LlamaCastyFan", Message = "$10 — LlamaCasty is the best!", Timestamp = DateTime.Now.AddMinutes(-3), IsSuperChat = true },
+        new ChatMessage { AuthorName = "GamerDude", Message = "what streaming software is this?", Timestamp = DateTime.Now.AddMinutes(-2) },
+        new ChatMessage { AuthorName = "LlamaCasty", Message = "thanks for watching! llamacasty.com", Timestamp = DateTime.Now.AddMinutes(-1), IsMember = true },
+        new ChatMessage { AuthorName = "LlamaDog", Message = "Subscribe so they can buy the subscription at llamacasty.com!", Timestamp = DateTime.Now, IsMember = true },
+    };
+    // Chat fade timer: clears chat overlay after N seconds of inactivity.
+    private System.Windows.Threading.DispatcherTimer? _chatFadeTimer;
+
+    public ObservableCollection<ChatMessage> ChatMessages { get; } = new();
+
+    /// <summary>The Add → YouTube Chat menu item: enabled only while no chat layer exists
+    /// anywhere — one chat overlay per layout.</summary>
+    public bool CanAddYouTubeChat
+        => StagedScene != null
+           && !Scenes.Any(s => s.Elements.OfType<Source>().Any(e => e.Type == SourceType.ChatBox));
+
+    public bool ShowChatInactiveMessage => !IsLive;
+
+    private void OnChatMessageReceived(ChatMessage message)
+    {
+        System.Windows.Application.Current.Dispatcher.Invoke(() =>
+        {
+            ChatMessages.Add(message);
+            if (ChatMessages.Count > 500)
+                ChatMessages.RemoveAt(0);
+
+            // Reset chat fade timer on every message
+            ResetChatFadeTimer();
+
+            StopMockChatPreview();
+
+            // Switch ChatBox previews from mock to real messages
+            if (StagedScene != null)
+                foreach (var chatBox in StagedScene.Elements.OfType<Source>().Where(s => s.Type == SourceType.ChatBox))
+                    UpdateChatBoxPreview(chatBox);
+        });
+    }
+
+    private void ResetChatFadeTimer()
+    {
+        _chatFadeTimer?.Stop();
+        var chatBoxes = Scenes.SelectMany(s => s.Elements).OfType<Source>()
+            .Where(s => s.Type == SourceType.ChatBox && s.ChatFadeSeconds > 0).ToList();
+        if (chatBoxes.Count == 0) return;
+
+        var delay = chatBoxes.Min(s => s.ChatFadeSeconds);
+        _chatFadeTimer = new System.Windows.Threading.DispatcherTimer
+        { Interval = TimeSpan.FromSeconds(delay) };
+        _chatFadeTimer.Tick += (_, _) =>
+        {
+            _chatFadeTimer?.Stop();
+            _chatFadeTimer = null;
+            ChatMessages.Clear();
+            foreach (var chatBox in Scenes.SelectMany(s => s.Elements).OfType<Source>()
+                         .Where(s => s.Type == SourceType.ChatBox))
+                UpdateChatBoxPreview(chatBox);
+            StartMockChatPreview();
+        };
+        _chatFadeTimer.Start();
+    }
+
+    private VideoFrame? RenderChatBox(Source chatBox)
+    {
+        if (ChatMessages.Count == 0) return null;
+
+        var width = (int)Math.Max(1, chatBox.Width);
+        var height = (int)Math.Max(1, chatBox.Height);
+
+        return _chatBoxRenderer.Render(
+            ChatMessages,
+            width,
+            height,
+            chatBox.ChatFontSize,
+            chatBox.ChatFontFamily,
+            chatBox.ChatFontColor,
+            chatBox.ChatBackgroundColor,
+            chatBox.ChatMaxMessages,
+            chatBox.ChatShowTimestamps,
+            chatBox.ChatShowBadges,
+            chatBox.ChatMemberColor,
+            chatBox.ChatSuperChatColor);
+    }
+
+    /// <summary>
+    /// Renders the ChatBox preview: real messages when connected, mock when not.
+    /// </summary>
+    private void UpdateChatBoxPreview(Source chatBox, IReadOnlyList<ChatMessage>? messages = null)
+    {
+        try
+        {
+            messages ??= ChatMessages.Count > 0 ? (IReadOnlyList<ChatMessage>)ChatMessages : MockChatMessages;
+            var width = (int)Math.Max(32, chatBox.Width);
+            var height = (int)Math.Max(32, chatBox.Height);
+
+            var frame = _chatBoxRenderer.Render(
+                messages,
+                width,
+                height,
+                chatBox.ChatFontSize,
+                chatBox.ChatFontFamily,
+                chatBox.ChatFontColor,
+                chatBox.ChatBackgroundColor,
+                chatBox.ChatMaxMessages,
+                chatBox.ChatShowTimestamps,
+                chatBox.ChatShowBadges,
+                chatBox.ChatMemberColor,
+                chatBox.ChatSuperChatColor);
+
+            var bitmap = new WriteableBitmap(width, height, 96, 96, System.Windows.Media.PixelFormats.Bgra32, null);
+            bitmap.WritePixels(new System.Windows.Int32Rect(0, 0, width, height), frame.BgraPixels, frame.Stride, 0);
+            chatBox.VideoImageSource = bitmap;
+        }
+        catch (Exception ex) { AppLog.Write($"UpdateChatBoxPreview failed: {ex.Message}"); }
+    }
+
+    private CancellationTokenSource? _mockChatCts;
+
+    private async Task RunMockChatPreviewAsync(Source chatBox, CancellationToken ct)
+    {
+        var n = 0;
+        while (!ct.IsCancellationRequested)
+        {
+            UpdateChatBoxPreview(chatBox, MockChatMessages.Take(n + 1).ToList());
+            await Task.Delay(1000, ct);
+            n++;
+            if (n == MockChatMessages.Count)
+            {
+                await Task.Delay(3000, ct);
+                n = 0;
+            }
+        }
+    }
+
+    private void StartMockChatPreview()
+    {
+        StopMockChatPreview();
+        _mockChatCts = new CancellationTokenSource();
+        var ct = _mockChatCts.Token;
+        foreach (var chatBox in Scenes.SelectMany(s => s.Elements).OfType<Source>()
+                     .Where(s => s.Type == SourceType.ChatBox && s.ChatPreviewEnabled))
+            _ = RunMockChatPreviewAsync(chatBox, ct);
+    }
+
+    private void StopMockChatPreview()
+    {
+        _mockChatCts?.Cancel();
+        _mockChatCts?.Dispose();
+        _mockChatCts = null;
+    }
+
+    /// <summary>
+    /// Render previews + wire property-change subscriptions for all ChatBox
+    /// sources across every scene. Called after layout load so existing ChatBox
+    /// sources show mock content and respond to config changes.
+    /// </summary>
+    private void UpdateActiveChatBoxPreviews()
+    {
+        foreach (var scene in Scenes)
+            foreach (var chatBox in scene.Elements.OfType<Source>().Where(s => s.Type == SourceType.ChatBox))
+            {
+                chatBox.PropertyChanged += (_, e) =>
+                {
+                    if (e.PropertyName is nameof(Source.ChatFontSize) or nameof(Source.ChatFontColor)
+                        or nameof(Source.ChatBackgroundColor) or nameof(Source.ChatBackgroundOpacity)
+                        or nameof(Source.ChatMaxMessages) or nameof(Source.ChatShowTimestamps)
+                        or nameof(Source.ChatShowBadges) or nameof(Source.ChatMemberColor)
+                        or nameof(Source.ChatSuperChatColor) or nameof(Source.ChatFontFamily)
+                        or nameof(Source.ChatFadeSeconds) or nameof(Source.Width) or nameof(Source.Height))
+                        UpdateChatBoxPreview(chatBox);
+                };
+                UpdateChatBoxPreview(chatBox);
+            }
+    }
+}

ViewModels/MainViewModel.Socials.cs

@@ -0,0 +1,161 @@
+using System.Windows;
+using System.Windows.Input;
+using System.Windows.Media;
+using ytLive;
+using ytLive.Helpers;
+using ytLive.Models;
+using ytLive.Services;
+using ytLive.Services.Compositor;
+
+namespace ytLive.ViewModels;
+
+public partial class MainViewModel
+{
+    private SocialsConfig? _socials;
+    private VideoFrame? _socialBarFrame;
+    private readonly ISocialValidator _socialValidator = new HttpSocialValidator();
+
+    public ICommand OpenSocialDialogCommand { get; }
+
+    // ─── Social bar (global resource, shown on every scene) ───
+
+    /// <summary>True when the global socials config has at least one validated entry.</summary>
+    public bool HasSocials => _socials != null && _socials.Entries.Count > 0;
+
+    /// <summary>The bar is on the stream when it's enabled and has entries.</summary>
+    public bool SocialBarVisible => (_socials?.BarEnabled ?? false) && HasSocials;
+
+    /// <summary>Footer indicator dot: green when the bar is on the stream, red otherwise.</summary>
+    public SolidColorBrush SocialBarDotBrush => SocialBarVisible ? BarOnBrush : BarOffBrush;
+
+    /// <summary>Green glow on the bar while it's on the stream.</summary>
+    public SolidColorBrush SocialBarGlowBrush => BarOnBrush;
+
+    /// <summary>The global socials config (entries + bar settings), or null.</summary>
+    public SocialsConfig? Socials => _socials;
+
+    /// <summary>Canvas.Top for the social bar: 0 = top, 1040 = bottom (40px from the 1080 edge).</summary>
+    public double SocialBarTop => _socials?.BarPosition == SocialBarPosition.Top ? 0 : 1040;
+
+
+    /// <summary>
+    /// Resolves a missing nodeinfo software name (mastodon, peertube, ...) for every
+    /// fediverse entry that doesn't have one, so the bar shows the instance's real
+    /// logo instead of the generic fediverse glyph. Best-effort: a failed resolution
+    /// leaves the glyph untouched. Returns handle → software for what was resolved —
+    /// the caller applies + persists (the app hops to the dispatcher; a test applies
+    /// directly).
+    /// </summary>
+    public static async Task<Dictionary<string, string>> HealFediverseSoftwareAsync(
+        SocialsConfig socials,
+        ISocialValidator validator,
+        Action<string>? log = null)
+    {
+        var resolved = new Dictionary<string, string>();
+        if (socials == null || validator == null) return resolved;
+        foreach (var entry in socials.Entries)
+        {
+            if (entry.Service != SocialService.Fediverse
+                || !string.IsNullOrWhiteSpace(entry.FediverseSoftware))
+                continue;
+            if (!SocialServiceIcons.TryParseFediverse(entry.Handle, out _, out var domain))
+                continue;
+            var software = await validator.ResolveFediverseSoftwareAsync(
+                domain, System.Threading.CancellationToken.None);
+            if (string.IsNullOrWhiteSpace(software)) continue;
+            resolved[entry.Handle] = software;
+            log?.Invoke($"Socials heal: {entry.Handle} → {software}");
+        }
+        return resolved;
+    }
+
+    /// <summary>Runs the heal off the UI thread and applies + saves any result.</summary>
+    private void HealFediverseSoftwareInBackground()
+    {
+        var socials = _socials;
+        if (socials == null) return;
+        _ = Task.Run(async () =>
+        {
+            try
+            {
+                var resolved = await HealFediverseSoftwareAsync(
+                    socials, _socialValidator, m => AppLog.Write(m));
+                if (resolved.Count == 0) return;
+                await Application.Current.Dispatcher.InvokeAsync(() =>
+                {
+                    var current = _socials;
+                    if (current == null) return;
+                    var applied = false;
+                    foreach (var entry in current.Entries)
+                    {
+                        if (!resolved.TryGetValue(entry.Handle, out var software)) continue;
+                        if (entry.FediverseSoftware == software) continue;
+                        entry.FediverseSoftware = software;
+                        applied = true;
+                    }
+                    if (applied) NotifySocialsChanged(); // re-renders the bar + saves
+                });
+            }
+            catch (Exception ex)
+            {
+                AppLog.Write($"Socials heal failed: {ex.Message}");
+            }
+        });
+    }
+
+    /// <summary>
+    /// Re-rasterizes the social bar strip the output compositor overlays. UI thread
+    /// only (WPF rendering); the resulting frame is immutable, so the frame pump may
+    /// read it from its own thread. Null when the bar is off or empty.
+    /// </summary>
+    private void RenderSocialBarFrame()
+    {
+        _socialBarFrame = _socials != null && _socials.BarEnabled
+            ? SocialBarRenderer.Render(_socials.Entries)
+            : null;
+    }
+
+    /// <summary>
+    /// Opens the Social Media Site Promotion dialog (6 slots, sign-in gate,
+    /// validation). On save the working copy replaces <see cref="_socials"/>.
+    /// </summary>
+    private void OpenSocialDialog()
+    {
+        var dialog = new SocialsDialogViewModel(
+            _socialValidator,
+            SignInAsync,
+            SignOutYouTubeAsync,
+            _youtubeAuth.CurrentChannel,
+            _socials);
+        var window = new ytLive.SocialsDialog(dialog) { Owner = Application.Current.MainWindow };
+        if (window.ShowDialog() == true)
+        {
+            _socials = dialog.BuildSocialsConfig();
+            NotifySocialsChanged();
+        }
+    }
+
+    private void NotifySocialsChanged()
+    {
+        RenderSocialBarFrame();
+        OnPropertyChanged(nameof(HasSocials));
+        OnPropertyChanged(nameof(SocialBarVisible));
+        OnPropertyChanged(nameof(SocialBarDotBrush));
+        ScheduleSave();
+    }
+
+    /// <summary>Sets the bar's edge; called by the preview click-toggle.</summary>
+    public void SetSocialBarPosition(SocialBarPosition position)
+    {
+        if (_socials == null || _socials.BarPosition == position) return;
+        _socials.BarPosition = position;
+        OnPropertyChanged(nameof(SocialBarTop));
+        ScheduleSave();
+    }
+
+    /// <summary>Preview click flips the bar top ⇄ bottom (KISS — no drag math).</summary>
+    public void ToggleSocialBarPosition()
+        => SetSocialBarPosition(_socials?.BarPosition == SocialBarPosition.Top
+            ? SocialBarPosition.Bottom
+            : SocialBarPosition.Top);
+}

ViewModels/MainViewModel.Streaming.cs

@@ -0,0 +1,789 @@
+using System.Collections.ObjectModel;
+using System.IO;
+using System.Windows;
+using System.Windows.Input;
+using System.Windows.Threading;
+using Microsoft.Win32;
+using ytLive.Helpers;
+using ytLive.Models;
+using ytLive.Services;
+using ytLive.Services.Encoder;
+
+namespace ytLive.ViewModels;
+
+public partial class MainViewModel : ViewModelBase
+{
+
+    private readonly DispatcherTimer _liveTimer;
+    private readonly DispatcherTimer _healthPollTimer;
+
+    private StreamStatus _streamStatus = StreamStatus.Offline;
+    private StreamHealth _currentHealth = new();
+    private string _streamTitle = string.Empty;
+    private string _streamDescription = string.Empty;
+    private string _streamVisibility = "Private";
+    private string? _currentBroadcastId;
+    private string? _reusableStreamUrl;
+    private ReusableStream? _reusableStream;
+    private string? _healthIssueBanner;
+    private string _healthIssueBackground = "Transparent";
+    private string _windowTitle = "LlamaCasty";
+    private string _topBarBackground = "#16213e";
+    private string _previewGlowBrush = "Transparent";
+    private Thickness _previewGlowThickness = new(0);
+    private string _liveElapsedText = "00:00:00";
+    private double _recDotPulse = 1.0;
+    private TimeSpan _liveElapsed;
+
+    // ─── Recording (TASK 18): independent REC / ON-AIR pills. The pills are
+    // ─── intent; IsRecording / IsLive are reality. ON-AIR needs a sign-in.
+    private bool _recordPillOn;
+    private bool _onAirPillOn;
+    private bool _isRecording;
+    private string? _recordFolder;
+
+    /// <summary>Resolved record folder — the configured choice, or Downloads (0th case).</summary>
+    public string RecordFolderDisplay => _recordFolder ?? DefaultRecordFolder();
+
+    private string? _activeRecordPath;
+    private DateTime _recordStartTime;
+    private TimeSpan _recordLength;
+
+    private readonly FramePump _framePump;
+
+    public StreamStatus StreamStatus
+    {
+        get => _streamStatus;
+        set
+        {
+            if (SetProperty(ref _streamStatus, value))
+            {
+                OnPropertyChanged(nameof(IsOffline));
+                OnPropertyChanged(nameof(IsLive));
+                OnPropertyChanged(nameof(IsEditMode));
+                OnPropertyChanged(nameof(RecDotBrush));
+                OnPropertyChanged(nameof(RecTextBrush));
+                OnPropertyChanged(nameof(RecDotOpacity));
+                OnPropertyChanged(nameof(OnAirBrush));
+                OnPropertyChanged(nameof(IsLivePrivate));
+                OnPropertyChanged(nameof(ShowPrimaryStartButton));
+                OnPropertyChanged(nameof(ShowLogInButton));
+                OnPropertyChanged(nameof(ShowEndStreamButton));
+                OnPropertyChanged(nameof(EndButtonText));
+                OnPropertyChanged(nameof(AccountStatusLightToolTip));
+                OnPropertyChanged(nameof(ShowChatInactiveMessage));
+                OnPropertyChanged(nameof(ShowPreviewPlaceholder));
+                UpdateLiveVisuals();
+            }
+        }
+    }
+
+    public bool IsOffline => StreamStatus == StreamStatus.Offline;
+    public bool IsLive => StreamStatus == StreamStatus.Streaming;
+    public bool IsLivePrivate => IsLive && string.Equals(StreamVisibility, "Private", StringComparison.OrdinalIgnoreCase);
+    public string RecDotBrush => !IsRecording ? "#555555" : "#e94560";
+    public string RecTextBrush => (IsLive || IsRecording) ? "#ffffff" : "#888888";
+    public double RecDotOpacity => IsRecording ? _recDotPulse : 0.55;
+    public string OnAirBrush => !IsLive ? "#555555" : IsLivePrivate ? "#22c55e" : "#e94560";
+
+    // ─── REC / ON-AIR pills (TASK 18) ───
+    public bool RecordPillOn
+    {
+        get => _recordPillOn;
+        set
+        {
+            if (!SetProperty(ref _recordPillOn, value)) return;
+            OnPropertyChanged(nameof(ShowPrimaryStartButton));
+            OnPropertyChanged(nameof(CanStartSession));
+        }
+    }
+
+    public bool OnAirPillOn
+    {
+        get => _onAirPillOn;
+        set
+        {
+            if (value && !CanToggleOnAir) return; // needs a sign-in
+            if (!SetProperty(ref _onAirPillOn, value)) return;
+            OnPropertyChanged(nameof(ShowPrimaryStartButton));
+            OnPropertyChanged(nameof(CanStartSession));
+        }
+    }
+
+    /// <summary>The ON-AIR pill (and thus live streaming) needs a YouTube sign-in.</summary>
+    public bool CanToggleOnAir => IsConnected;
+
+    /// <summary>Whether the session is actively recording — the REC status light
+    /// turns green only when this is true (the pill is intent, this is reality).</summary>
+    public bool IsRecording
+    {
+        get => _isRecording;
+        private set
+        {
+            if (!SetProperty(ref _isRecording, value)) return;
+            OnPropertyChanged(nameof(RecDotBrush));
+            OnPropertyChanged(nameof(RecTextBrush));
+            OnPropertyChanged(nameof(RecDotOpacity));
+            OnPropertyChanged(nameof(IsEditMode));
+            OnPropertyChanged(nameof(ShowEndStreamButton));
+            OnPropertyChanged(nameof(ShowPrimaryStartButton));
+            OnPropertyChanged(nameof(EndButtonText));
+            UpdateSessionTimer();
+        }
+    }
+
+    /// <summary>The primary button shows when there's something to start, but never
+    /// while a session is running — once recording/live the ONLY control is the End
+    /// button.</summary>
+    public bool ShowPrimaryStartButton =>
+        IsOffline && !IsRecording && !IsLive
+        && (IsConnected || (RecordPillOn && !OnAirPillOn));
+
+    /// <summary>Either output selected makes the button actionable.</summary>
+    public bool CanStartSession => RecordPillOn || OnAirPillOn;
+
+    /// <summary>The End button shows while recording OR live.</summary>
+    public bool ShowEndStreamButton => IsLive || IsRecording;
+
+    /// <summary>The one button whose label changes: while recording it reads
+    /// "Stop Recording", while live "End Stream".</summary>
+    public string EndButtonText => IsRecording && !IsLive ? "Stop Recording" : "End Stream";
+
+    public bool ShowLogInButton => !IsConnected && IsOffline && !IsRecording;
+
+    public StreamHealth CurrentHealth
+    {
+        get => _currentHealth;
+        set => SetProperty(ref _currentHealth, value);
+    }
+
+    /// <summary>Report-by-exception YouTube health (TASK 5 item 3): non-null only
+    /// while a warning/error configuration issue exists — the banner's text.
+    /// good/ok/noData keep it null so nothing renders.</summary>
+    public string? HealthIssueBanner
+    {
+        get => _healthIssueBanner;
+        private set => SetProperty(ref _healthIssueBanner, value);
+    }
+
+    /// <summary>Banner background: app red (#8f1f1f) for an error issue, amber
+    /// (#b8860b) for a warning. Transparent when no banner is shown.</summary>
+    public string HealthIssueBackground
+    {
+        get => _healthIssueBackground;
+        private set => SetProperty(ref _healthIssueBackground, value);
+    }
+
+    public string StreamTitle
+    {
+        get => _streamTitle;
+        set => SetProperty(ref _streamTitle, value);
+    }
+
+    public string StreamDescription
+    {
+        get => _streamDescription;
+        set => SetProperty(ref _streamDescription, value);
+    }
+
+    public string StreamVisibility
+    {
+        get => _streamVisibility;
+        set
+        {
+            if (SetProperty(ref _streamVisibility, value))
+            {
+                OnPropertyChanged(nameof(RecDotBrush));
+                OnPropertyChanged(nameof(RecTextBrush));
+                OnPropertyChanged(nameof(OnAirBrush));
+                OnPropertyChanged(nameof(IsLivePrivate));
+            }
+        }
+    }
+
+    public string WindowTitle
+    {
+        get => _windowTitle;
+        set => SetProperty(ref _windowTitle, value);
+    }
+
+    public string TopBarBackground
+    {
+        get => _topBarBackground;
+        set => SetProperty(ref _topBarBackground, value);
+    }
+
+    public string PreviewGlowBrush
+    {
+        get => _previewGlowBrush;
+        set => SetProperty(ref _previewGlowBrush, value);
+    }
+
+    public Thickness PreviewGlowThickness
+    {
+        get => _previewGlowThickness;
+        set => SetProperty(ref _previewGlowThickness, value);
+    }
+
+    public string LiveElapsedText
+    {
+        get => _liveElapsedText;
+        set => SetProperty(ref _liveElapsedText, value);
+    }
+
+    // ─── Broadcast metadata pull-out (the "Text" tab on the Live screen) ───
+
+    /// <summary>The broadcast id of the current/last session; null until Go Live
+    /// succeeds. Gates the pull-out's Update button (nothing remote to patch).</summary>
+    public string? CurrentBroadcastId => _currentBroadcastId;
+
+    public Services.LiveBroadcastFormViewModel BroadcastForm { get; }
+
+    // ─── Resolution quality dropdown (bottom bar) ───
+    // Tiers offered to the creator before going live. First = default. The
+    // dropdown is disabled while live because YouTube stream resolution is
+    // immutable after stream creation (see TASKS.md compliance notes).
+
+    // The composition master frame. Every tier is an output rect + target
+    // resolution over this frame (see ai.md "Resolution tiers"): 16:9 tiers
+    // use the full frame; the vertical tier uses a centered 9:16 window and
+    // the preview dims the cropped strips (semi-crop).
+    private const double MasterFrameWidth = 1920;
+    private const double MasterFrameHeight = 1080;
+
+    public QualityOption[] QualityOptions { get; } =
+    {
+        new("1080p60", 60, 8.0, 1920, 1080),
+        new("1080p30", 30, 8.0, 1920, 1080),
+        new("720p60", 60, 6.0, 1280, 720),
+        new("720p30", 30, 6.0, 1280, 720),
+        new("Vertical 1080p60", 60, 8.0, 1080, 1920),
+    };
+
+    public string ResolutionHelp { get; } =
+        "Pick the highest resolution your upload bandwidth can comfortably sustain. " +
+        "Find your upload speed on your ISP plan or with a speed test (e.g. fast.com), " +
+        "then choose a tier your upload comfortably exceeds. 1080p60 is the default.";
+
+    private QualityOption _selectedQuality;
+    public QualityOption SelectedQuality
+    {
+        get => _selectedQuality;
+        set
+        {
+            if (SetProperty(ref _selectedQuality, value))
+                ApplyStreamQuality(value);
+        }
+    }
+
+    // Output frame of the selected tier over the 1920x1080 master. The strips
+    // outside it are dimmed in the preview so the cropped area stays visible.
+    public double OutputRectX { get; private set; }
+    public double OutputRectY { get; private set; }
+    public double OutputRectWidth { get; private set; }
+    public double OutputRectHeight { get; private set; }
+    public bool IsOutputCropped { get; private set; }
+    public string ResolutionBadgeText { get; private set; } = string.Empty;
+    public ObservableCollection<Rect> DimRects { get; } = new();
+
+    private void ApplyStreamQuality(QualityOption quality)
+    {
+        var health = CurrentHealth;
+        health.CurrentBitrate = quality.Bitrate;
+        health.FPS = quality.Fps;
+        OnPropertyChanged(nameof(CurrentHealth));
+
+        var scale = Math.Min(MasterFrameWidth / quality.Width, MasterFrameHeight / quality.Height);
+        var rectW = quality.Width * scale;
+        var rectH = quality.Height * scale;
+        var rectX = (MasterFrameWidth - rectW) / 2;
+        var rectY = (MasterFrameHeight - rectH) / 2;
+
+        OutputRectX = rectX;
+        OutputRectY = rectY;
+        OutputRectWidth = rectW;
+        OutputRectHeight = rectH;
+
+        DimRects.Clear();
+        if (rectX > 0) DimRects.Add(new Rect(0, 0, rectX, MasterFrameHeight));
+        if (rectX + rectW < MasterFrameWidth)
+            DimRects.Add(new Rect(rectX + rectW, 0, MasterFrameWidth - rectX - rectW, MasterFrameHeight));
+        if (rectY > 0) DimRects.Add(new Rect(0, 0, MasterFrameWidth, rectY));
+        if (rectY + rectH < MasterFrameHeight)
+            DimRects.Add(new Rect(0, rectY + rectH, MasterFrameWidth, MasterFrameHeight - rectY - rectH));
+
+        IsOutputCropped = DimRects.Count > 0;
+        ResolutionBadgeText = $"{quality.Label} · {quality.Width}×{quality.Height}";
+
+        OnPropertyChanged(nameof(OutputRectX));
+        OnPropertyChanged(nameof(OutputRectY));
+        OnPropertyChanged(nameof(OutputRectWidth));
+        OnPropertyChanged(nameof(OutputRectHeight));
+        OnPropertyChanged(nameof(IsOutputCropped));
+        OnPropertyChanged(nameof(ResolutionBadgeText));
+    }
+
+    public ICommand StartStreamCommand { get; }
+    public ICommand EndStreamCommand { get; }
+    public ICommand ChooseRecordFolderCommand { get; }
+    public ICommand ResetRecordFolderCommand { get; }
+
+    /// <summary>Entry point for the primary Start button (and the start/stop hotkey):
+    /// routes to a record session or the YouTube go-live dialog by the pill state.</summary>
+    private void StartSession()
+    {
+        if (IsLive || IsRecording) return;
+        var streaming = OnAirPillOn;
+        var recording = RecordPillOn;
+        if (!streaming && !recording) return;
+
+        if (!streaming)
+        {
+            BeginRecordOnly();
+            return;
+        }
+        BeginGoLive(recording);
+    }
+
+    /// <summary>Record-only (REC pill on, ON-AIR off): no YouTube dialog — recording
+    /// is local and works signed-out. Generates the auto-named file and starts the
+    /// pipeline immediately.</summary>
+    private async void BeginRecordOnly()
+    {
+        var path = StartRecordFile();
+        if (path == null)
+        {
+            _notifications.Error("Couldn't record", "No record output path could be created.");
+            return;
+        }
+        _recordStartTime = DateTime.Now;
+        _liveElapsed = TimeSpan.Zero;
+        _recordLength = TimeSpan.Zero;
+        ResetHealth(StreamStatus.Offline);
+        _audioMixer.StartLive(EncoderOptions.DefaultAudioPipeName);
+        IsRecording = true;
+        await _framePump.StartAsync();
+    }
+
+    private void BeginGoLive(bool alsoRecord)
+    {
+        var dialog = new GoLiveViewModel(() => SignInAsync(), _youtubeAuth.CurrentChannel)
+        {
+            StreamTitle = BroadcastForm.Title,
+            StreamDescription = BroadcastForm.Description,
+        };
+        var window = new ytLive.GoLiveWindow(dialog) { Owner = System.Windows.Application.Current.MainWindow };
+        if (window.ShowDialog() == true)
+        {
+            StreamTitle = dialog.StreamTitle;
+            StreamDescription = dialog.StreamDescription;
+            StreamVisibility = dialog.Visibility; // always "Private" (ship step 7)
+            BroadcastForm.CaptureGoLive(dialog.StreamTitle, dialog.StreamDescription, DateTime.UtcNow);
+            WindowTitle = string.IsNullOrWhiteSpace(dialog.StreamTitle)
+                ? "LlamaCasty"
+                : $"{dialog.StreamTitle} — LlamaCasty";
+            StreamStatus = StreamStatus.Streaming;
+            ResetHealth(StreamStatus.Streaming);
+            _audioMixer.StartLive(EncoderOptions.DefaultAudioPipeName);
+            _liveElapsed = TimeSpan.Zero;
+            _recordLength = TimeSpan.Zero;
+
+            var recordStarted = false;
+            if (alsoRecord)
+            {
+                if (StartRecordFile() == null)
+                {
+                    _notifications.Error("Couldn't record",
+                        "No record output path could be created — streaming continues without recording.");
+                }
+                else
+                {
+                    _recordStartTime = DateTime.Now;
+                    recordStarted = true;
+                }
+            }
+            IsRecording = recordStarted;
+
+            _ = PrepareAndStartLiveAsync();
+        }
+    }
+
+    /// <summary>Creates the record file (auto-named <c>ty-…-0000.mp4</c> in the record
+    /// folder) and returns its path, or null when the folder can't be prepared.</summary>
+    private string? StartRecordFile()
+    {
+        try
+        {
+            var folder = _recordFolder ?? DefaultRecordFolder();
+            Directory.CreateDirectory(folder);
+            var name = RecordingFile.BuildStartName(DateTime.Now) + ".mp4";
+            var path = Path.Combine(folder, name);
+            _activeRecordPath = path;
+            return path;
+        }
+        catch (Exception ex)
+        {
+            AppLog.Write(ex, "Recording: failed to prepare output path");
+            return null;
+        }
+    }
+
+    /// <summary>One-click go-live (TASK 5): ensure the reusable stream, create a
+    /// broadcast bound to it, then start the frame pump. The pump reads the RTMP
+    /// URL once at startup (FramePump.StartAsync), so the stream URL must be set
+    /// before the pump starts — hence the ordering here. Failures surface as an
+    /// error health state, never a crash.</summary>
+    private async Task PrepareAndStartLiveAsync()
+    {
+        try
+        {
+            var stream = await _youtubeStream.GetOrCreateReusableStreamAsync();
+            if (stream == null)
+            {
+                AppLog.Write("Reusable stream unavailable; check the OAuth session");
+                _notifications.Error("Couldn't go live",
+                    "The reusable stream is unavailable — check the YouTube sign-in and try again.");
+                StreamStatus = StreamStatus.Error;
+                return;
+            }
+            _reusableStream = stream;
+            _reusableStreamUrl = stream.RtmpUrl;
+            _layoutStore.SaveReusableStream(stream);
+
+            _currentBroadcastId = await _youtubeStream.CreateBroadcast(
+                StreamTitle, StreamDescription, DateTime.UtcNow, stream.Id);
+            if (_currentBroadcastId == null)
+            {
+                AppLog.Write("Broadcast creation failed; check the OAuth session");
+                _notifications.Error("Couldn't go live", "YouTube rejected the broadcast — check the sign-in and try again.");
+                StreamStatus = StreamStatus.Error;
+                return;
+            }
+            AppLog.Write($"Broadcast created: {_currentBroadcastId}");
+            OnPropertyChanged(nameof(CurrentBroadcastId));
+
+            if (string.IsNullOrWhiteSpace(StreamTitle) && string.IsNullOrWhiteSpace(StreamDescription))
+            {
+                BroadcastForm.IsDrawerOpen = true;
+                _notifications.Warning("Complete your broadcast details",
+                    "Your title and description are empty — fill them in from the Text panel on the right.");
+            }
+
+            // Start chat polling (TASK 9.4): fetch the liveChatId from the broadcast's
+            // contentDetails, then start the poll loop. Chat is non-fatal — if it fails,
+            // the stream continues without on-panel chat.
+            try
+            {
+                var liveChatId = await _youtubeStream.GetBroadcastLiveChatIdAsync(_currentBroadcastId);
+                if (liveChatId != null)
+                {
+                    _youtubeChat.Start(liveChatId);
+                    AppLog.Write($"Chat polling started: {liveChatId}");
+                }
+                else
+                {
+                    AppLog.Write("Could not retrieve liveChatId; chat polling disabled");
+                }
+            }
+            catch (Exception chatEx)
+            {
+                AppLog.Write($"Chat start failed (non-fatal): {chatEx.Message}");
+            }
+        }
+        catch (Exception ex)
+        {
+            AppLog.Write($"Go-live preparation failed: {ex.Message}");
+            _notifications.Error("Couldn't go live", ex.Message);
+            StreamStatus = StreamStatus.Error;
+            return;
+        }
+
+        await _framePump.StartAsync(); // never throws; failures log + surface via Failed
+
+        // Health polling (TASK 5 item 3): poll immediately, then every 30s while
+        // live. Report-by-exception — a banner appears only on warning/error.
+        _healthPollTimer.Start();
+        _ = PollHealthAsync();
+    }
+
+    private void OnHealthPollTick(object? sender, EventArgs e) => _ = PollHealthAsync();
+
+    /// <summary>One liveStreams.list poll (TASK 5 item 3): updates the YouTube
+    /// health state + the report-by-exception banner. Never throws — a poll
+    /// failure logs and leaves the last state untouched.</summary>
+    private async Task PollHealthAsync()
+    {
+        if (_reusableStream == null || !IsLive) return;
+        try
+        {
+            var health = await _youtubeStream.GetStreamHealthAsync(_reusableStream.Id);
+            if (health == null)
+            {
+                AppLog.Write("Stream health poll failed; check the OAuth session");
+                return;
+            }
+            CurrentHealth.HealthStatus = health.HealthStatus;
+            CurrentHealth.HealthMessage = health.HealthStatus;
+            CurrentHealth.ConfigurationIssues.Clear();
+            CurrentHealth.ConfigurationIssues.AddRange(health.ConfigurationIssues);
+            OnPropertyChanged(nameof(CurrentHealth));
+            ApplyHealthIssue(health.ConfigurationIssues);
+        }
+        catch (Exception ex)
+        {
+            AppLog.Write($"Stream health poll failed: {ex.Message}");
+        }
+    }
+
+    // Report-by-exception: good/ok/noData (or info-only issues) clear the banner;
+    // the first warning/error issue raises it, colored by the worst severity.
+    private void ApplyHealthIssue(List<StreamConfigurationIssue> issues)
+    {
+        var report = StreamHealthReporter.BannerFor(issues);
+        if (report.Text == null)
+        {
+            HealthIssueBanner = null;
+            HealthIssueBackground = "Transparent";
+            return;
+        }
+
+        HealthIssueBackground = report.IsError ? "#8f1f1f" : "#b8860b";
+        HealthIssueBanner = report.Text;
+    }
+
+    private async void StopStream()
+    {
+        var wasLive = IsLive;
+        var wasRecording = IsRecording;
+
+        StreamStatus = StreamStatus.Offline;
+        IsRecording = false;
+        WindowTitle = "LlamaCasty";
+        ResetHealth(StreamStatus.Offline);
+        // Stop chat polling first (TASK 9.4) — no more messages arriving while
+        // we're tearing down the stream.
+        _youtubeChat.Stop();
+        // Close the audio pipe FIRST so ffmpeg sees EOF on the audio input,
+        // then stop the pump (stdin EOF) — both inputs end and the encoder
+        // finalizes the output. Audio capture itself is always-on (preview
+        // monitoring); only the live/report pipe, the pump, and the session stop here.
+        _audioMixer.StopLive();
+        await _framePump.StopAsync();
+        _currentBroadcastId = null;
+        OnPropertyChanged(nameof(CurrentBroadcastId));
+
+        if (wasRecording) await FinalizeRecordingAsync();
+
+        // Explicit sign-out only (TASK 18): stopping the stream does NOT clear
+        // the session/token — the creator signs out deliberately via the
+        // Logout / Change Account commands.
+        AppLog.Write(wasLive ? "Stream ended" : "Recording ended");
+    }
+
+    /// <summary>On stop the auto-named <c>ty-…-0000.mp4</c> file is renamed to carry
+    /// the real recording length (<c>ty-…-hh2mm2.mp4</c>), with a numeric suffix on
+    /// name collisions. Runs only after the pump has fully closed the file.</summary>
+    private async Task FinalizeRecordingAsync()
+    {
+        var startPath = _activeRecordPath;
+        _activeRecordPath = null;
+        if (string.IsNullOrEmpty(startPath)) return;
+        try
+        {
+            while (_framePump.IsRunning) await Task.Delay(50);
+
+            if (!File.Exists(startPath))
+            {
+                AppLog.Write($"Recording: output not found for rename: {startPath}");
+                return;
+            }
+            _recordLength = _liveElapsed;
+            var autoStem = RecordingFile.BuildFinalName(_recordStartTime, _recordLength);
+            var dir = Path.GetDirectoryName(startPath)!;
+
+            // Manual rename modal: give the creator a chance to name the recording;
+            // null = keep the auto name (or the default recorded above).
+            string stem = autoStem;
+            var dialog = new RenameRecordingDialog(autoStem);
+            if (dialog.ShowDialog() == true && !string.IsNullOrEmpty(dialog.ResultFileName))
+                stem = dialog.ResultFileName;
+
+            var finalPath = UniquePath(Path.Combine(dir, stem + ".mp4"));
+            File.Move(startPath, finalPath);
+            AppLog.Write($"Recording saved: {finalPath}");
+            _notifications.Info("Recording saved",
+                Path.GetFileName(finalPath) + " — you can rename it in your videos folder at any time.");
+        }
+        catch (Exception ex)
+        {
+            AppLog.Write(ex, "Recording: rename-on-stop failed");
+            _notifications.Error("Recording saved",
+                $"The recording was written but couldn't be renamed: {Path.GetFileName(startPath)}");
+        }
+    }
+
+    private static string UniquePath(string path)
+    {
+        if (!File.Exists(path)) return path;
+        var dir = Path.GetDirectoryName(path)!;
+        var name = Path.GetFileNameWithoutExtension(path);
+        var ext = Path.GetExtension(path);
+        for (var i = 2; ; i++)
+        {
+            var candidate = Path.Combine(dir, $"{name}-{i}{ext}");
+            if (!File.Exists(candidate)) return candidate;
+        }
+    }
+
+    private void ChooseRecordFolder()
+    {
+        var dialog = new Microsoft.Win32.OpenFolderDialog
+        {
+            Title = "Choose a folder for local recordings",
+            InitialDirectory = _recordFolder ?? DefaultRecordFolder(),
+        };
+        if (dialog.ShowDialog() == true)
+        {
+            _recordFolder = dialog.FolderName;
+            _layoutStore.SaveRecordFolder(_recordFolder);
+            OnPropertyChanged(nameof(RecordFolderDisplay));
+            _notifications.Info("Record folder set", _recordFolder);
+        }
+    }
+
+    private void ResetRecordFolder()
+    {
+        _recordFolder = null;
+        _layoutStore.SaveRecordFolder(null);
+        OnPropertyChanged(nameof(RecordFolderDisplay));
+        _notifications.Info("Record folder reset", RecordFolderDisplay);
+    }
+
+    /// <summary>Falls back to the user's Downloads folder when no preference is set;
+    /// returns MyVideos if Downloads doesn't exist.</summary>
+    internal static string DefaultRecordFolder()
+    {
+        var downloads = Path.Combine(
+            Environment.GetFolderPath(Environment.SpecialFolder.UserProfile), "Downloads");
+        return Directory.Exists(downloads)
+            ? downloads
+            : Environment.GetFolderPath(Environment.SpecialFolder.MyVideos);
+    }
+
+    // Full encoder options for the current tier, or null when no RTMP URL is
+    // available — the pump then skips the encoder entirely (TASK 5 fills the seam).
+    private EncoderOptions? BuildEncoderOptions()
+    {
+        var url = _rtmpUrlProvider();
+        var quality = SelectedQuality;
+        return new EncoderOptions
+        {
+            RtmpUrl = url ?? string.Empty,
+            StreamEnabled = OnAirPillOn,
+            RecordEnabled = RecordPillOn,
+            RecordPath = _activeRecordPath,
+            Width = quality.Width,
+            Height = quality.Height,
+            Fps = quality.Fps,
+            BitrateKbps = (int)Math.Round(quality.Bitrate * 1000),
+        };
+    }
+
+    private void OnFramePumpFailed(object? sender, string message)
+    {
+        AppLog.Write($"Frame pump failed: {message}");
+        _notifications.Error("The stream pipeline stopped", message);
+        if (IsLive) StreamStatus = StreamStatus.Error;
+    }
+
+    // TASK 4 ship step 6: the encoder's parsed health (bitrate/FPS/dropped/
+    // duration) lands in the bottom bar. The stderr loop raises on a background
+    // thread — marshal to the UI thread like the audio level handlers.
+    private void OnFramePumpHealthUpdated(object? sender, StreamHealth health)
+    {
+        var dispatcher = System.Windows.Application.Current?.Dispatcher;
+        if (dispatcher != null && !dispatcher.CheckAccess())
+            dispatcher.BeginInvoke(() => ApplyHealth(health));
+        else
+            ApplyHealth(health);
+    }
+
+    private void ApplyHealth(StreamHealth health)
+    {
+        CurrentHealth.Status = health.Status;
+        CurrentHealth.CurrentBitrate = health.CurrentBitrate;
+        CurrentHealth.FPS = health.FPS;
+        CurrentHealth.DroppedFrames = health.DroppedFrames;
+        CurrentHealth.StreamDuration = health.StreamDuration;
+        CurrentHealth.LastError = health.LastError;
+        CurrentHealth.HealthMessage = health.HealthMessage;
+        OnPropertyChanged(nameof(CurrentHealth));
+    }
+
+    // Keeps the bottom-bar stats honest across sessions: dropped frames and the
+    // elapsed duration must not linger from a previous go-live (bitrate/FPS stay
+    // on the tier's targets — ApplyStreamQuality sets them on pick).
+    private void ResetHealth(StreamStatus status)
+    {
+        CurrentHealth.Status = status;
+        CurrentHealth.DroppedFrames = 0;
+        CurrentHealth.StreamDuration = TimeSpan.Zero;
+        CurrentHealth.LastError = null;
+        CurrentHealth.HealthStatus = null;
+        CurrentHealth.HealthMessage = null;
+        CurrentHealth.ConfigurationIssues.Clear();
+        HealthIssueBanner = null;
+        HealthIssueBackground = "Transparent";
+        OnPropertyChanged(nameof(CurrentHealth));
+    }
+
+    private void UpdateLiveVisuals()
+    {
+        var live = IsLive;
+        TopBarBackground = live ? "#e94560" : "#16213e";
+        PreviewGlowBrush = live ? "#e94560" : "Transparent";
+        PreviewGlowThickness = live ? new Thickness(3) : new Thickness(0);
+
+        if (live)
+        {
+            if (BrandFlashEnabled) StartBrandFlashTimer();
+        }
+        else
+        {
+            _healthPollTimer.Stop();
+            _brandFlashTimer.Stop();
+            _brandFlashOffTimer.Stop();
+            BrandFlashActive = false;
+        }
+        UpdateSessionTimer();
+    }
+
+    /// <summary>Runs the elapsed/rec-dot-pulse timer while a session is active —
+    /// live (Streaming) OR recording. Reset the elapsed when a new session starts.</summary>
+    private void UpdateSessionTimer()
+    {
+        var active = IsLive || IsRecording;
+        if (active)
+        {
+            _recDotPulse = 1.0;
+            _liveTimer.Start();
+        }
+        else
+        {
+            _liveTimer.Stop();
+            LiveElapsedText = "00:00:00";
+            _recDotPulse = 1.0;
+        }
+        OnPropertyChanged(nameof(RecDotOpacity));
+        OnPropertyChanged(nameof(LiveElapsedText));
+    }
+
+    private void OnLiveTimerTick(object? sender, EventArgs e)
+    {
+        _liveElapsed = _liveElapsed.Add(TimeSpan.FromSeconds(1));
+        LiveElapsedText = _liveElapsed.ToString(@"hh\:mm\:ss");
+        _recordLength = _liveElapsed;
+        _recDotPulse = _recDotPulse > 0.5 ? 0.35 : 1.0;
+        OnPropertyChanged(nameof(RecDotOpacity));
+    }
+}

ViewModels/MainViewModel.Trax.cs

@@ -0,0 +1,132 @@
+using System.IO;
+using System.Windows.Media;
+using Microsoft.Win32;
+using ytLive.Helpers;
+using ytLive.Models;
+using ytLive.Services.Audio;
+
+namespace ytLive.ViewModels;
+
+public partial class MainViewModel
+{
+    // TRAX (TASK 9): free background music at a fixed quiet volume, playing to
+    // the default device so it rides the loopback into the stream. The dot is
+    // red (no track) / yellow (loaded, stopped) / green (playing).
+    private readonly MusicPlayer _musicPlayer = new();
+    private Music? _music;
+    private bool _musicPlaying;
+
+    private static readonly SolidColorBrush TraxIdleBrush = CreateBrush("#555");
+    /// <summary>True while the TRAX background track is playing.</summary>
+    public bool IsMusicPlaying
+    {
+        get => _musicPlaying;
+        private set
+        {
+            if (SetProperty(ref _musicPlaying, value))
+            {
+                OnPropertyChanged(nameof(TraxDotBrush));
+                OnPropertyChanged(nameof(TraxToolTip));
+            }
+        }
+    }
+
+    private string? _traxError;
+
+    /// <summary>Error message from the last TRAX load/playback failure; null = no error.</summary>
+    public string? TraxError
+    {
+        get => _traxError;
+        private set => SetProperty(ref _traxError, value);
+    }
+
+    /// <summary>TRAX status dot: green = playing, gray = idle or no track.</summary>
+    public SolidColorBrush TraxDotBrush => _musicPlayer.IsPlaying
+        ? BarOnBrush
+        : TraxIdleBrush;
+
+    public string TraxToolTip => _musicPlayer.TrackName != null
+        ? $"TRAX: {_musicPlayer.TrackName} — left-click {(IsMusicPlaying ? "pauses" : "plays")}, right-click chooses a track"
+        : "No track — left-click or right-click to choose background music";
+
+    /// <summary>Left-click on TRAX: no track → pick one; otherwise toggle play/pause.</summary>
+    public void TraxLeftClick()
+    {
+        if (_music == null || string.IsNullOrWhiteSpace(_music.TrackPath))
+            PickTraxTrack();
+        else if (IsMusicPlaying)
+            PauseTrax();
+        else
+            PlayTrax();
+    }
+
+    /// <summary>Right-click on TRAX: always open the track picker (never the OS viewer).</summary>
+    public void TraxRightClick() => PickTraxTrack();
+
+    private void PickTraxTrack()
+    {
+        var dialog = new OpenFileDialog
+        {
+            Title = "Choose background music",
+            Filter = "Music (*.mp3;*.wav;*.m4a;*.aac;*.flac;*.ogg)|*.mp3;*.wav;*.m4a;*.aac;*.flac;*.ogg|All files (*.*)|*.*",
+        };
+        if (dialog.ShowDialog() != true)
+            return;
+
+        _music = new Music { TrackPath = dialog.FileName, IsEnabled = true };
+        LoadTrax(play: true);
+    }
+
+    private void LoadTrax(bool play)
+    {
+        if (_music == null || string.IsNullOrWhiteSpace(_music.TrackPath))
+            return;
+
+        try
+        {
+            _musicPlayer.Load(_music.TrackPath);
+            UpdateTraxLocalGain();
+            _music.IsEnabled = true;
+            TraxError = null;
+            if (play)
+                _musicPlayer.Play();
+        }
+        catch (Exception ex)
+        {
+            AppLog.Write($"TRAX: failed to load '{_music.TrackPath}': {ex.Message}");
+            TraxError = $"Failed to load: {Path.GetFileName(_music.TrackPath)} — {ex.Message}";
+        }
+        RefreshTraxUi();
+        ScheduleSave();
+    }
+
+    private void PlayTrax() => _musicPlayer.Play();
+
+    private void PauseTrax() => _musicPlayer.Pause();
+
+    private void OnTraxPlaybackEnded(Exception? ex)
+    {
+        if (ex != null)
+        {
+            AppLog.Write($"TRAX: playback error: {ex.Message}");
+            TraxError = $"Playback error: {ex.Message}";
+        }
+        RefreshTraxUi();
+    }
+
+    private void RefreshTraxUi()
+    {
+        IsMusicPlaying = _musicPlayer.IsPlaying;
+        OnPropertyChanged(nameof(TraxDotBrush));
+        OnPropertyChanged(nameof(TraxToolTip));
+    }
+
+    /// <summary>Mirrors the desktop/game audio bar's volume and mute onto the
+    /// music so the creator hears the controls work in the headphones (the
+    /// track rides the loopback channel, so it must duck the same way locally).
+    /// Called whenever the game volume/mute change and on TRAX load.</summary>
+    private void UpdateTraxLocalGain()
+    {
+        _musicPlayer.LocalGain = GameMuted ? 0f : 1f;
+    }
+}