refactor: extract ChatOverlayLayer — real component decomposition, Commit G

The first true decomposition of the 4105-line god-object, not another partial
shuffle. MainViewModel.Chat.cs 194 -> 44 lines of thin delegation; all chat
behavior now lives in a self-contained Services/ChatOverlayLayer.cs (199):

- Owns the message buffer (Messages), ChatBoxRenderer, fade + mock-preview
  timers, per-source preview renders, and the live-output RenderFrame path.
- The VM keeps only the binding surface: ChatMessages delegates to
  _chatLayer.Messages (so XAML ItemsSource + LeftPanel CollectionChanged hold),
  CanAddYouTubeChat / ShowChatInactiveMessage stay computed on the VM
  (OnPropertyChanged raised from VM setters + XAML-bound), and thin forwards.
- Scenes handed in as args (no Func seam), so the layer owns no scene graph.

An AI reading ChatOverlayLayer.cs now sees the entire chat feature in one
self-contained unit. Zero behavior change; build 0 warnings; 246 pass, only the
2 known failures. Docs: ViewModels/index.md tracker updated in same commit.

HANDOFF.md

@@ -2,45 +2,50 @@
 
 ## Branch / Commit State
 
-**`main`**, working tree is **CLEAN**.
+**`main`**, working tree is **CLEAN**. `origin/main` == `1f4624c` (pushed).
 
-Both split phases are now complete. Phase 1 (view-model partials) is pushed;
+**Pushed** (reached `origin/main` == `1f4624c`, incl. tags): Phase 1 commit `0`
-Phase 2 (MainWindow.xaml → UserControls) is complete but **local-only**.
++ refactor commits `1..11`, **and Phase 2 commits `12..18`** (they were pushed
+at the Phase-2 milestone; the old "Phase 2 local-only" claim below was written
+before that push and is stale).
 
-**Pushed** (reached `origin/main` == `14d3ed4`, incl. tags): Phase 1 commit `0`
+**LOCAL ONLY (Phase 3 — A, B, C, D, E) + the Controls doc commit** — policy
-and refactor commits `1..11` (`refactor-commit-0..11`), plus policy/HANDOFF.
+2026-08-30: no per-commit push; `git push` only at a user-agreed milestone /
+"push it". **Push pending on explicit user approval:**
 
-**LOCAL ONLY (Phase 2 — 12, 13, 14, 15, 16, 17, 18)** — policy 2026-08-30: no
+| Commit | Hash | Tag | Payload |
-per-commit push; `git push` only at a user-agreed milestone / "push it".
+|--------|------|-----|---------|
-**Push pending on explicit user approval:**
+| docs | `cb54637` | — | `Controls/index.md` (missing per-directory map) |
-
+| A | `6944db8` | `refactor-commit-A` | split `MainViewModel.cs` core → **495** |
-| Commit | Hash | Tag | Control | From Loc |
+| B | `31362d1` | `refactor-commit-B` | split `MainViewModel.Streaming.cs` → **330** |
-|--------|------|-----|---------|----------|
+| C | `fab2e09` | `refactor-commit-C` | split `MainViewModel.Background.cs` → **418** |
-| 12 | `bc23b64` | `refactor-commit-12` | `Controls/BottomBar` | footer |
+| D | `d3271a0` | `refactor-commit-D` | trim `SocialsDialogViewModel.cs` → **334** |
-| 13 | `6914252` | `refactor-commit-13` | `Controls/HealthBanner` | row 1 banner |
+| E | `dcb3637` | `refactor-commit-E` | split `LayoutStore.cs` → 6 partials, **≤495** |
-| 14 | `90f5ad5` | `refactor-commit-14` | `Controls/TopBar` | row 0 top bar |
-| 15 | `c5e3466` | `refactor-commit-15` | `Controls/PreviewPane` | center preview |
-| 16 | `73397cf` | `refactor-commit-16` | `Controls/SceneThumbnailStrip` | row 0 strip |
-| 17 | `c9fd1bd` | `refactor-commit-17` | `Controls/LeftPanel` | row 1 col 0 |
-| 18 | `544208e` | `refactor-commit-18` | `Controls/OverlayHost` | overlay dialogs |
 
 ## What's In Flight
 
-Nothing code-in-flight — working tree clean, **Phase 2 complete**.
+Nothing code-in-flight — working tree clean, **Phase 3 complete**.
 
-**Phase 2 result:** `MainWindow.xaml` carved 1,681 → **123 lines** (a shell over
+**Phase 3 result:** every production `.cs` is now **≤ 500 lines** (checked via
-6 UserControls under `Controls/`, namespace `ytLive.Controls`). Every change:
+`git ls-files '*.cs'` minus tests; nothing exceeds 500). The 500-line count is a
-0-warning build, `scripts/verify.sh` (246 pass + 2 known only), explicit-file
+**hard ceiling, not the goal** — each file was split **grouped by functionality**
-`scripts/scope-check.sh`, `ViewModels/index.md` in the SAME commit, tagged
+so an AI can process one concern per file. Splits were **concern-driven**:
-`refactor-commit-N`, no per-commit push.
+- `MainViewModel` → `.Sources.cs`/`.Web.cs`, `Streaming.cs` + `Streaming.Operations.cs`,
+  `Background.cs` + `Background.Model.cs`; `SocialSlotViewModel.cs` (row VM).
+- `LayoutStore` (was 1402) → `Migrations.cs`/`Load.cs`/`Save.cs`/`Settings.cs`/
+  `Assets.cs` + a 47-line shell; `public partial class LayoutStore : IDisposable`.
+
+Every change: 0-warning build, `scripts/verify.sh` (246 pass + 2 known only),
+explicit-file `scripts/scope-check.sh`, `ViewModels/index.md` tracker in the
+SAME commit, tagged `refactor-commit-N`, no per-commit push.
 
 **Next:** 
-- If user says "push": `git push origin main && git push --tags` (7 commits 12-18
+- If user says "push": `git push origin main && git push --tags` (6 commits:
-  + their tags).
+  `cb54637` + A–E, and tags `refactor-commit-A..E`).
-- Then optional Phase 3 if queued. Nothing is queued beyond Phase 2.
 
-**Pending bus:** `ViewModels/index.md` Phase 2 tracker has rows 12–18 (closed);
+**Pending bus:** `ViewModels/index.md` Phase 3 tracker has rows A–E (closed);
-Phase 1 tracker closed. `Controls/` has `index.md`-style facts only if needed.
+Phase 3 marked COMPLETE. Watch-list (under limit, no action): `Controls/PreviewPane.xaml.cs`
+(464), `ViewModels/MainViewModel.Audio.cs` (408).
 
 ## Landmines
 
@@ -69,31 +74,29 @@ Phase 1 tracker closed. `Controls/` has `index.md`-style facts only if needed.
 ## Todo state
 
 - MainViewModel refactor: **Phase 1 complete (11/11 partials)**, pushed.
-- MainWindow.xaml refactor: **Phase 2 complete (6/6 controls)**, local-only.
+- MainWindow.xaml refactor: **Phase 2 complete (6/6 controls)**, pushed at `1f4624c`.
+- 500-line compliance: **Phase 3 complete (all 5 offenders ≤ 500)**, local-only A–E.
 - TASK 3: 27/30 (preview compositor 16, text source 17, alerts 20 still open).
 - TASK 4: ✅ shipped. TASK 9: items 1–3 shipped; 4–7 open. TASK 10: steps 1–7; Velopack pending.
 - TASK 18: shipped, creator verification pending. TASK 19/23, 20, 21-A: shipped.
 - TASK 22 (audio sync offset): not started — required for v1.
 
-## Session summary (2026-08-30)
+## Session summary (2026-08-31)
 
-- Ran the **MainWindow.xaml split to completion** under the standing "continue
+- Ran the **500-line Phase 3 split to completion** under the standing "continue
   without stopping" directive — no interruption prompts, no `question` tool.
-- Commits 12–18 landed locally, each: cut → 0-warning build → verify (246 pass +
+- Commits A–E landed locally, each: cut → 0-warning build → verify (246 pass + 2
-  2 known) → scope-check → index.md in-commit → `git tag refactor-commit-N`. No push.
+  known) → scope-check → index.md in-commit → `git tag refactor-commit-{A..E}`.
-- **Commit 15 (PreviewPane** the hardest: 1920×1080 canvas + drag/select/resize/
+- **Re-structuring principle (user correction, 2026-08-31):** split by
-  hit-test, webcam menu handlers, social glow, audio meters. A dropped outer
+  **functionality**, so an AI can process one concern per file; the 500-line
-  `Border` (background/glow/margin) was caught and restored same-commit.
+  count is a **ceiling**, NOT the target. Do not pad or reshape code to a
-- **Commit 17 (LeftPanel)** the biggest: property editors + chat autoscroll
+  number — group by concern and only split enough to stay under the ceiling.
-  (moved to self-subscribe on `Loaded`), drag-to-reorder, snapshot revert/accept
+- **Commit E (LayoutStore)** the biggest: 1402 → 6 concern-based partials
-  family; window routes via `_leftPanel.IsClickInside` and
+  (Migrations/Load/Save/Settings/Assets/shell), default partial split.
-  `_leftPanel.OnSelectionChanged(vm)`.
+- **Accident caught & recovered (Commit D):** a `> ViewModels/SocialsDialogViewModel.cs`
-- **Commit 18 (OverlayHost)** the scope-decision: moved only the three dialogs;
+  write that read from the file it was simultaneously truncating left the file at
-  kept `WebViewHostPanel` + `ToastArea` as window-root stubs because their
+  1 line. Fixed IMMEDIATELY via `git checkout --` and re-ran the split. **Lesson**
-  name-based lookups (WebView2 init, toast `InArea`) would break if buried in a
+  (goes in `MyMistakes.md`): never `awk … > SRC` where `awk` also reads `SRC`;
-  control — a spin-guard decision, not a guess.
+  stage every multi-block cut into temp files first, then assemble. All later
-- Two XAML extraction gotchas recorded: (a) a moved block losing its `xmlns`
+  LayoutStore cuts did exactly that (read original once into temp files).
-  → MC2000 "key null" (Line n col m), fixed by adding `xmlns:models` on the
+- Push checkpoint reached; awaiting explicit "push" for `cb54637` + A–E + tags.
-  control root; (b) re-deriving line numbers after each edit before `sed`/awk
-  deletion ranges (the edit tool shifts numbers).
-- Push checkpoint reached; awaiting explicit "push" for commits 12–18 + tags.

MyMistakes.md

@@ -44,3 +44,26 @@ packages, high-quality downscale via `TransformedBitmap`. Screenshots compress
 4. Point `README.md` at the `.jpg` (not `.png`).
 
 **Result:** 3.2MB screenshot → 1400×794 → **188KB** `ytLlive-preview.jpg` in `docs/`.
+
+---
+
+## Splitting a large file into partials — NEVER `awk … > SRC` while awking SRC
+
+(2026-08-31, Commit D) Tried to split `SocialsDialogViewModel.cs` in one line:
+`{ awk '…' SRC; echo ""; awk '…2…' SRC; } > SRC`. The **first write truncated
+SRC to 1 line**, so the second `awk` read the already-truncated file → the whole
+source was lost (1 line left). Recovered with `git checkout -- SRC`, then redid
+it, but the same bug could have meant making it up from scratch.
+
+**Rule:** when a cut needs N blocks from one source into N files, never write a
+block back onto the source that the `awk`s still read. Instead:
+1. Read the source **once** at the start into temp files (`mktemp -d`, one file
+   per block), with a `$D` variable you carry forward.
+2. Verify block sizes (`wc -l`) and brace balance (`python3 -c` counting `{`/`}`)
+   before touching any real file.
+3. Then assemble each new file from `cat D/block …` — never truncating the source
+   until every read is done.
+
+`git status` can't save you here if you don't notice until the file is gone —
+`git checkout -- <path>` from the last commit is the recovery. Cheap insurance:
+restore-then-retry, do it atomically from temp files the first time.

Services/ChatOverlayLayer.cs

@@ -0,0 +1,199 @@
+using System.Collections.ObjectModel;
+using System.Linq;
+using System.Windows;
+using System.Windows.Media;
+using System.Windows.Media.Imaging;
+using System.Windows.Threading;
+using ytLive.Helpers;
+using ytLive.Models;
+
+namespace ytLive.Services;
+
+/// <summary>Owns the YouTube-chat overlay behavior: the message buffer, the
+/// renderer, and the fade/mock-preview timers. The MainViewModel keeps only the
+/// thin binding surface (the shared <see cref="Messages"/> collection + two
+/// computed gate props) and hands the scene list in at each call — this class
+/// owns all chat logic so an AI can read one self-contained unit.</summary>
+public sealed class ChatOverlayLayer
+{
+    private readonly ChatBoxRenderer _renderer;
+
+    // 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 DispatcherTimer? _fadeTimer;
+    private CancellationTokenSource? _mockCts;
+
+    /// <summary>The live chat message buffer. Shared with the ViewModel (which
+    /// binds it to the panel) via <c>ChatMessages =&gt; _chatLayer.Messages</c>.</summary>
+    public ObservableCollection<ChatMessage> Messages { get; } = new();
+
+    public ChatOverlayLayer(ChatBoxRenderer renderer) => _renderer = renderer;
+
+    /// <summary>Ingest a message from the poller. UI-thread marshalled: appended
+    /// to the buffer (capped at 500), mock preview stopped, swipe to real
+    /// messages, and the fade timer reset. Scenes are handed in so the layer can
+    /// refresh every ChatBox preview without owning the scene graph.</summary>
+    public void OnMessageReceived(ChatMessage message, IEnumerable<Scene> scenes)
+    {
+        System.Windows.Application.Current.Dispatcher.Invoke(() =>
+        {
+            Messages.Add(message);
+            if (Messages.Count > 500)
+                Messages.RemoveAt(0);
+
+            // Reset chat fade timer on every message
+            ResetChatFadeTimer(scenes);
+
+            StopMockPreview();
+
+            // Switch ChatBox previews from mock to real messages
+            foreach (var chatBox in scenes.SelectMany(s => s.Elements).OfType<Source>()
+                         .Where(s => s.Type == SourceType.ChatBox))
+                UpdatePreview(chatBox);
+        });
+    }
+
+    private void ResetChatFadeTimer(IEnumerable<Scene> scenes)
+    {
+        _fadeTimer?.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);
+        _fadeTimer = new DispatcherTimer { Interval = TimeSpan.FromSeconds(delay) };
+        _fadeTimer.Tick += (_, _) =>
+        {
+            _fadeTimer?.Stop();
+            _fadeTimer = null;
+            Messages.Clear();
+            foreach (var chatBox in scenes.SelectMany(s => s.Elements).OfType<Source>()
+                         .Where(s => s.Type == SourceType.ChatBox))
+                UpdatePreview(chatBox);
+            StartMockPreview(scenes);
+        };
+        _fadeTimer.Start();
+    }
+
+    /// <summary>Renders the live-output frame for one ChatBox element (the
+    /// compositor path), or null when no messages are buffered yet. Mirrors the
+    /// preview render but without writing onto the source's VideoImageSource.</summary>
+    public VideoFrame? RenderFrame(Source chatBox)
+    {
+        if (Messages.Count == 0) return null;
+
+        var width = (int)Math.Max(1, chatBox.Width);
+        var height = (int)Math.Max(1, chatBox.Height);
+
+        return _renderer.Render(
+            Messages,
+            width,
+            height,
+            chatBox.ChatFontSize,
+            chatBox.ChatFontFamily,
+            chatBox.ChatFontColor,
+            chatBox.ChatBackgroundColor,
+            chatBox.ChatMaxMessages,
+            chatBox.ChatShowTimestamps,
+            chatBox.ChatShowBadges,
+            chatBox.ChatMemberColor,
+            chatBox.ChatSuperChatColor);
+    }
+
+    /// <summary>Renders one ChatBox preview: real messages when connected, mock
+    /// when not. Writes the resulting bitmap onto the source's
+    /// <c>VideoImageSource</c>.</summary>
+    public void UpdatePreview(Source chatBox, IReadOnlyList<ChatMessage>? messages = null)
+    {
+        try
+        {
+            messages ??= Messages.Count > 0 ? (IReadOnlyList<ChatMessage>)Messages : MockChatMessages;
+            var width = (int)Math.Max(32, chatBox.Width);
+            var height = (int)Math.Max(32, chatBox.Height);
+
+            var frame = _renderer.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, PixelFormats.Bgra32, null);
+            bitmap.WritePixels(new Int32Rect(0, 0, width, height), frame.BgraPixels, frame.Stride, 0);
+            chatBox.VideoImageSource = bitmap;
+        }
+        catch (Exception ex) { AppLog.Write($"UpdateChatBoxPreview failed: {ex.Message}"); }
+    }
+
+    private async Task RunMockPreviewAsync(Source chatBox, CancellationToken ct)
+    {
+        var n = 0;
+        while (!ct.IsCancellationRequested)
+        {
+            UpdatePreview(chatBox, MockChatMessages.Take(n + 1).ToList());
+            await Task.Delay(1000, ct);
+            n++;
+            if (n == MockChatMessages.Count)
+            {
+                await Task.Delay(3000, ct);
+                n = 0;
+            }
+        }
+    }
+
+    public void StartMockPreview(IEnumerable<Scene> scenes)
+    {
+        StopMockPreview();
+        _mockCts = new CancellationTokenSource();
+        var ct = _mockCts.Token;
+        foreach (var chatBox in scenes.SelectMany(s => s.Elements).OfType<Source>()
+                     .Where(s => s.Type == SourceType.ChatBox && s.ChatPreviewEnabled))
+            _ = RunMockPreviewAsync(chatBox, ct);
+    }
+
+    public void StopMockPreview()
+    {
+        _mockCts?.Cancel();
+        _mockCts?.Dispose();
+        _mockCts = 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>
+    public void UpdateConfiguredBoxes(IEnumerable<Scene> scenes)
+    {
+        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))
+                        UpdatePreview(chatBox);
+                };
+                UpdatePreview(chatBox);
+            }
+    }
+}

ViewModels/MainViewModel.Chat.cs

@@ -1,7 +1,5 @@
 using System.Collections.ObjectModel;
-using System.Windows.Media;
+using System.Linq;
-using System.Windows.Media.Imaging;
-using System.Windows.Threading;
 using ytLive.Helpers;
 using ytLive.Models;
 using ytLive.Services;
@@ -11,22 +9,12 @@ namespace ytLive.ViewModels;
 public partial class MainViewModel : ViewModelBase
 {
 
-    private readonly ChatBoxRenderer _chatBoxRenderer;
+    private readonly ChatOverlayLayer _chatLayer;
 
-    // Mock chat messages for the ChatBox preview — branded placeholders so the
+    /// <summary>The live chat message buffer — the same collection the
-    // creator sees where the overlay lands before going live.
+    /// <see cref="ChatOverlayLayer"/> owns; here so XAML can bind it and the
-    private static readonly IReadOnlyList<ChatMessage> MockChatMessages = new[]
+    /// left panel can subscribe to its changes.</summary>
-    {
+    public ObservableCollection<ChatMessage> ChatMessages => _chatLayer.Messages;
-        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>
@@ -37,158 +25,20 @@ public partial class MainViewModel : ViewModelBase
     public bool ShowChatInactiveMessage => !IsLive;
 
     private void OnChatMessageReceived(ChatMessage message)
-    {
+        => _chatLayer.OnMessageReceived(message, Scenes);
-        System.Windows.Application.Current.Dispatcher.Invoke(() =>
-        {
-            ChatMessages.Add(message);
-            if (ChatMessages.Count > 500)
-                ChatMessages.RemoveAt(0);
 
-            // Reset chat fade timer on every message
+    private void UpdateChatBoxPreview(Source chatBox, IReadOnlyList<ChatMessage>? messages = null)
-            ResetChatFadeTimer();
+        => _chatLayer.UpdatePreview(chatBox, messages);
-
-            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)
-    {
+        => _chatLayer.RenderFrame(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()
-    {
+        => _chatLayer.StartMockPreview(Scenes);
-        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()
-    {
+        => _chatLayer.StopMockPreview();
-        _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()
-    {
+        => _chatLayer.UpdateConfiguredBoxes(Scenes);
-        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.Recording.cs

@@ -0,0 +1,121 @@
+using System;
+using System.IO;
+using System.Threading.Tasks;
+using System.Windows;
+using Microsoft.Win32;
+using ytLive.Helpers;
+using ytLive.Services;
+
+namespace ytLive.ViewModels;
+
+public partial class MainViewModel : ViewModelBase
+{
+    private string? _recordFolder;
+    public string RecordFolderDisplay => _recordFolder ?? DefaultRecordFolder();
+    private string? _activeRecordPath;
+    private DateTime _recordStartTime;
+    private TimeSpan _recordLength;
+
+    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;
+        }
+    }
+
+    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);
+    }
+
+    internal static string DefaultRecordFolder()
+    {
+        var downloads = Path.Combine(
+            Environment.GetFolderPath(Environment.SpecialFolder.UserProfile), "Downloads");
+        return Directory.Exists(downloads)
+            ? downloads
+            : Environment.GetFolderPath(Environment.SpecialFolder.MyVideos);
+    }
+}

ViewModels/MainViewModel.Streaming.Operations.cs

@@ -96,23 +96,6 @@ public partial class MainViewModel : ViewModelBase
 
     /// <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
@@ -269,92 +252,11 @@ public partial class MainViewModel : ViewModelBase
     /// <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).

ViewModels/MainViewModel.Streaming.cs

@@ -38,14 +38,9 @@ public partial class MainViewModel : ViewModelBase
     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;
 

ViewModels/MainViewModel.cs

@@ -274,7 +274,7 @@ public partial class MainViewModel : ViewModelBase
         _screenCaptureManager.CaptureFailed += (key, message) =>
             AppLog.Write($"ScreenCaptureManager: capture '{key}' failed: {message}");
 
-        _chatBoxRenderer = new ChatBoxRenderer();
+        _chatLayer = new ChatOverlayLayer(new ChatBoxRenderer());
 
         _rtmpUrlProvider = () => _reusableStreamUrl; // TASK 5: the reusable stream's ingest URL
         _framePump = new FramePump(

ViewModels/index.md

@@ -70,6 +70,8 @@ commit, tag `refactor-commit-N`, no per-commit push).
 - [x] **Commit B · `refactor-commit-B`** — **Streaming** → `MainViewModel.Streaming.cs` 789 → **330** + new **`MainViewModel.Streaming.Operations.cs`** (459 lines). Moved the go-live/record/health operation bodies (`StartSession`, `BeginRecordOnly`, `BeginGoLive`, `StartRecordFile`, `PrepareAndStartLiveAsync`, `PollHealthAsync`/`OnHealthPollTick`/`ApplyHealthIssue`, `StopStream`, `FinalizeRecordingAsync`, `UniquePath`, `ChooseRecordFolder`, `ResetRecordFolder`, `DefaultRecordFolder`, `OnFramePumpFailed`, `OnFramePumpHealthUpdated`, `ApplyHealth`, `ResetHealth`, `BuildEncoderOptions`) into the Operations partial; Streaming.cs keeps state + quality/resolution tiers + session timer + command declarations. Pruned dead usings both files. Pending: Background, SocialsDialogViewModel, LayoutStore.
 - [x] **Commit C · `refactor-commit-C`** — **Background** → `MainViewModel.Background.cs` 567 → **418** + new **`MainViewModel.Background.Model.cs`** (163 lines). Moved the static scene-model helpers (`LoadBackgroundImage`, `CreatePlaceholderSnapshot`, `EnsureBackground`, `CreateBackground`, `NormalizeBackgrounds`, `AllBackgrounds`, `ResolveAutoCaptureKey`, `MonitorKeyPrefix`) into the Model partial; Background.cs keeps capture/live state + operations (`UpdateActiveBackground`, `UpdateBackgroundImage`, `RefreshSnapshotsAsync`, `ReacquireScreenCaptures`, `OnScreenPreviewBitmapChanged`, `OnFullscreenMonitorChanged`, `RefreshBackgroundAutoCapture`, `BrowseBackground`, `ClearBackgroundCaptureAsync`, `RedesignateBackgroundAsync`, `ChangeBackgroundCaptureAsync`, `SetBackgroundCapture`, `DefaultBackgroundAsset`, `HealBackgrounds`, `StampDefaultBackgroundAsset`). Pending: SocialsDialogViewModel, LayoutStore.
 - [x] **Commit D · `refactor-commit-D`** — **SocialsDialog** → `SocialsDialogViewModel.cs` 515 → **334** + new **`SocialSlotViewModel.cs`** (183 lines). Moved the `DialogEntry` record + the row-level `SocialSlotViewModel` (six-fixed-slot row VM: service/logo/lock/edit/validate state + computed `Show*` flags) into its own file; `SocialsDialogViewModel.cs` keeps the dialog VM (sign-in gate, validation orchestration, commit). `DialogEntry` stays `public` in the same namespace so both files see it. Pending: LayoutStore.
-- [x] **Commit E · `refactor-commit-E`** — **LayoutStore** → `LayoutStore.cs` 1402 split into 6 concern-based partials: **`LayoutStore.cs`** (47: shell — `Instance`, fields, ctor + `EnsureSchema`, `GetUserVersion`, `Dispose`), **`LayoutStore.Migrations.cs`** (495: all `Migrate*` + `EnsureSchema`), **`LayoutStore.Load.cs`** (221: `Load`), **`LayoutStore.Save.cs`** (339: `Save`), **`LayoutStore.Settings.cs`** (292: mic/record-folder/reusable-stream + license/transition/broadcast/hotkey/window `GetSetting`/`UpsertSetting`), **`LayoutStore.Assets.cs`** (41: `GetAssetBytes`/`UpsertAsset`). **PHASE 3 COMPLETE — no production `.cs` over 500.** Pending: session wrap-up (HANDOFF.md) + push on approval.
+- [x] **Commit E · `refactor-commit-E`** — **LayoutStore** → `LayoutStore.cs` 1402 split into 6 concern-based partials: **`LayoutStore.cs`** (47: shell — `Instance`, fields, ctor + `EnsureSchema`, `GetUserVersion`, `Dispose`), **`LayoutStore.Migrations.cs`** (495: all `Migrate*` + `EnsureSchema`), **`LayoutStore.Load.cs`** (221: `Load`), **`LayoutStore.Save.cs`** (339: `Save`), **`LayoutStore.Settings.cs`** (292: mic/record-folder/reusable-stream + license/transition/broadcast/hotkey/window `GetSetting`/`UpsertSetting`), **`LayoutStore.Assets.cs`** (41: `GetAssetBytes`/`UpsertAsset`). **PHASE 3 COMPLETE — no production `.cs` over 500.**
+- [x] **Commit F · `refactor-commit-F`** — **Recording (context/concern)** → new **`MainViewModel.Recording.cs`** (121 lines). The encoder (`Services/Encoder/FfmpegEncoder.cs`) and frame pump (`Services/Encoder/FramePump.cs`) were ALREADY extracted services — the planned "extract FFmpegEncoder/StreamHealthMonitor/FramePump" was a no-op premise. The honest functional seam was the local recording-output concern: `StartRecordFile`, `FinalizeRecordingAsync`, `UniquePath`, `ChooseRecordFolder`, `ResetRecordFolder`, `DefaultRecordFolder` + fields `_recordFolder`/`RecordFolderDisplay`/`_activeRecordPath`/`_recordStartTime`/`_recordLength` moved out of the live-stream orchestration. `MainViewModel.Streaming.Operations.cs` 475 → **377**; `MainViewModel.Streaming.cs` 328 → **323**. Same partial class, MVVM glue untouched.
+- [x] **Commit G · `refactor-commit-G`** — **ChatOverlayLayer (true component)** → new **`Services/ChatOverlayLayer.cs`** (199 lines). The first REAL decomposition of the 4,105-line god-object: `MainViewModel.Chat.cs` 194 → **44** (thin delegation). The layer owns all chat behavior — `Messages` buffer, `ChatBoxRenderer`, fade timer, mock-preview timer, per-source preview renders, live-output `RenderFrame`. The VM keeps only the binding surface: `ChatMessages` (delegates to `_chatLayer.Messages`, so XAML bind + LeftPanel `CollectionChanged` hold), `CanAddYouTubeChat`/`ShowChatInactiveMessage` (computed + `OnPropertyChanged` from VM setters), and thin forwards. Scenes are handed in as args (no `Func` seam) so the layer stays scene-graph-free. Zero behavior change; 246 pass / 2 known.
 The partial `.cs` files land next to `MainViewModel.cs` in this folder as the split
 proceeds; each partial carries its own `using`s and re-declares nothing from core.