diff --git a/App.xaml.cs b/App.xaml.cs
index 0ba296a..8dceaa4 100644
--- a/App.xaml.cs
+++ b/App.xaml.cs
@@ -26,6 +26,9 @@ public partial class App : Application
             AppLog.Write(args.Exception, "Dispatcher unhandled exception");
 
         AppLog.Write("App OnStartup begin");
+        // Attribution (2026-09-04): every take must be traceable to the exact binary
+        // that produced it — the wordmark superscript shows this same id.
+        AppLog.Write($"Build {ytLive.Helpers.BuildStamp.Id} (compiled {ytLive.Helpers.BuildStamp.BuiltLocal})");
 
         // Velopack auto-update bootstrap — checks for updates on startup and
         // applies them (the app restarts automatically if an update is found).
diff --git a/Controls/TopBar.xaml b/Controls/TopBar.xaml
index 54bff2b..232f24f 100644
--- a/Controls/TopBar.xaml
+++ b/Controls/TopBar.xaml
@@ -1,6 +1,7 @@
 <UserControl x:Class="ytLive.Controls.TopBar"
              xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
              xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+             xmlns:helpers="clr-namespace:ytLive.Helpers"
              x:Name="TopBarRoot">
     <!-- LOGO / BRAND — clicking opens the in-app About overlay -->
     <Grid>
@@ -20,7 +21,10 @@
                 </ControlTemplate>
             </Button.Template>
             <TextBlock FontSize="22" FontWeight="Bold">
-                <Run Text="LlamaCas" Foreground="#e0e0e0"/><Run Text="ty" Foreground="#e94560"/>
+                <Run Text="LlamaCas" Foreground="#e0e0e0"/><Run Text="ty" Foreground="#e94560"/><Run
+                    x:Name="BuildIdStamp" Text="{x:Static helpers:BuildStamp.Id}" FontSize="9"
+                    BaselineAlignment="Superscript" Foreground="#8888aa"
+                    ToolTipService.ToolTip="{x:Static helpers:BuildStamp.Id}"/><Run Text=" " FontSize="4"/>
             </TextBlock>
         </Button>
 
diff --git a/HANDOFF.md b/HANDOFF.md
index 5347d6b..e3c71d5 100644
--- a/HANDOFF.md
+++ b/HANDOFF.md
@@ -44,11 +44,18 @@ RealApp boot-smoke. Scope-check passed.
    raster on message/config change, blit the cached frame every tick (OBS text-source pattern).
    Tests: `ChatOverlayLayerCacheTests` (the ONE, RealApp) + full regression green (62 across
    touched classes), clean build 0 warnings.
-2. **Take 6 (user, ~30s record-only):** expect `≈300/300 frames per 5s, avg render ≤ ~10ms`. If
-   chat-burst drops one frame per message (avg fine but `n/300` sags during live chat): debounced
-   off-tick re-render is the next slice. If steady at ~300 with render <10 → recording saga
-   CLOSED, go Unit B (below).
-3. **Unit B — the top bar + session logic (user spec 2026-09-04, decisions settled):**
+2. **BUILD STAMP shipped (slice 4, same day):** take 6 came back 35-41ms — WORSE than take 5 —
+   and attribution was impossible (exe timestamp ≠ binary contents; incremental builds served
+   unverified exes). Every build now stamps a fresh GUID (`ytLive.csproj GenerateBuildStamp` →
+   `Helpers/BuildStamp`), shown as the wordmark superscript (build id) + `Build xxxxxxxx (compiled
+   ...)` in startup.log; stats report `avg render Xms (resolve Y)` so the hot half of the tick is
+   named. Tests `BuildStampTests` + `BuildStampDisplayTests` (real window, namescoped FindName).
+3. **Take 7 (user, ~30s record-only):** FIRST read the superscript + startup.log Build line — the
+   take is meaningless without it. Expect slice 3 in any post-stamp build: `avg render ≤ ~10ms
+   (resolve ≪ render), ≈300/300`. If resolve dominates → resolver-side surprise (chat config thrash
+   / web frame); if blit dominates → measure the general-path element sizes. If chat-burst sags
+   `n/300`: debounced off-tick re-render slice. If clean → recording saga CLOSED, Unit B.
+4. **Unit B — the top bar + session logic (user spec 2026-09-04 re-sent twice + decisions settled in Q&A):**
    - Two-line top bar. Line 1: center = REC + **LIVE** pills (text renamed from ON-AIR; pills become
      mutually-exclusive RADIOS — record-OR-stream ruling), right = avatar + **Login/Logout** button
      (no account status light). Line 2: centered primary **Start** (grayed while NO pill armed —
@@ -67,6 +74,12 @@ RealApp boot-smoke. Scope-check passed.
      live is scary — confirmation allows back-out + testing up to go-live").
    - Bottom-bar metrics init/maintain: `ResetHealth` + `HealthUpdated` exist — verify on take 6.
    - F6 "start/end" hotkey routes through `HandleHotkey` — check it honors the new grayed-Start gate.
+   - Login button text: "Login" (disconnected, LIVE pill greyed) → "Logout" (connected, avatar
+     appears left of it). The account status LIGHT is deleted per spec 2a.
+   - Primary button: grayed "Start" when NO pill armed (inverts 2026-09-01 rule — fix the map in
+     the landing commit); enabled when either armed; REC path = file dialog flow; LIVE path =
+     go-live after dialog confirm; becomes the Stop/End face while active (user's "Stop button
+     never active" complaint gets a hermetic test pinning visibility+CanExecute).
    - ONE integration test (hermetic): pills↔button state machine + record-path seam (an
      `internal static Func<SaveFileDialog-ish prompt>` override seam mirroring `RegistrarOverride`
      — never pop real dialogs in tests).
diff --git a/MyMistakes.md b/MyMistakes.md
index b5b131c..5911e24 100644
--- a/MyMistakes.md
+++ b/MyMistakes.md
@@ -213,3 +213,18 @@ one-line provenance — *who asked, what triggered it* ("creator: OBS delay-filt
 Features without attribution become roadmap orphans that get punted, removed, or re-litigated. Same
 disease as an unexplained "known failure" label — a fact recorded without its reason is a future
 argument.
+
+## An un-attributed build invalidated three takes of a perf saga — stamp the binary
+
+(2026-09-04, takes 4–6) After each render-perf fix the creator "exed the code" and re-recorded, but
+the exe timestamp ≠ binary contents (incremental builds reuse whatever compiles clean; a source edit
+with no rebuild serves the OLD exe). Take 6 measured render WORSE than take 5 (35-41ms) and there was
+no honest way to tell "the chat cache fix doesn't work" from "the fix was never running" — three
+hours of diagnosis on an unattributable sample. Rule: if takes measure the app, EVERY build carries
+an id and EVERY log line traces to it — `GenerateBuildStamp` (csproj) writes a fresh GUID per
+compile (deliberately defeating incremental lies), the wordmark shows it as a superscript, startup.log
+records `Build <id> (compiled <time>)`. A perf claim without build attribution is a guess; ask for the
+stamp BEFORE theorizing. (Also this session: a sentinel-byte test where the source pattern could
+GENERATE the sentinel, and a fixed-point bilinear that shifted BOTH stages and silently drew nothing —
+see the rawvideo recipe.)
+
diff --git a/Services/Encoder/FramePump.cs b/Services/Encoder/FramePump.cs
index 507a40e..08d2983 100644
--- a/Services/Encoder/FramePump.cs
+++ b/Services/Encoder/FramePump.cs
@@ -265,7 +265,11 @@ public sealed class FramePump : IDisposable
         // Log the render/submit split every 5s so the next take names the stage.
         var renderSw = new System.Diagnostics.Stopwatch();
         var submitSw = new System.Diagnostics.Stopwatch();
-        long renderTicks = 0, submitTicks = 0;
+        // Resolve-vs-composite split (2026-09-04, take-6 ambiguity): "render" was a
+        // black box — the stats line now reports resolver time separately so a take
+        // names the stage (get-frame vs blit) instead of feeding another guess.
+        var resolveSw = new System.Diagnostics.Stopwatch();
+        long renderTicks = 0, submitTicks = 0, resolveTicks = 0;
         int statFrames = 0;
         var statsNext = DateTime.UtcNow + TimeSpan.FromSeconds(5);
         void ReportStats()
@@ -275,13 +279,25 @@ public sealed class FramePump : IDisposable
             _log?.Invoke(statFrames == 0
                 ? "FramePump stats: NO frames produced in 5s (loop stalled?)"
                 : $"FramePump stats: {statFrames}/{target:F0} frames per 5s, " +
-                  $"avg render {renderTicks / (double)System.Diagnostics.Stopwatch.Frequency * 1000 / statFrames:F1}ms, " +
+                  $"avg render {renderTicks / (double)System.Diagnostics.Stopwatch.Frequency * 1000 / statFrames:F1}ms " +
+                  $"(resolve {resolveTicks / (double)System.Diagnostics.Stopwatch.Frequency * 1000 / statFrames:F1}), " +
                   $"avg submit {submitTicks / (double)System.Diagnostics.Stopwatch.Frequency * 1000 / statFrames:F1}ms");
-            renderTicks = submitTicks = 0;
+            renderTicks = submitTicks = resolveTicks = 0;
             statFrames = 0;
             statsNext = DateTime.UtcNow + TimeSpan.FromSeconds(5);
         }
 
+        // One wrapper shared by every render of the run — resolve time accumulates
+        // inside the render measurement, and the stats line reports the split.
+        VideoFrame? TimedResolver(SceneElement element)
+        {
+            resolveSw.Restart();
+            var frame = _frameResolver(element);
+            resolveSw.Stop();
+            resolveTicks += resolveSw.ElapsedTicks;
+            return frame;
+        }
+
         try
         {
             while (!ct.IsCancellationRequested)
@@ -312,12 +328,15 @@ public sealed class FramePump : IDisposable
                     // pooling change because its buffer's only consumer was its own release.
                     renderSw.Restart();
                     var scratch = AcquireScratch(scratchSize);
-                    frame = RenderScene(scene, compositorOptions, socialBarFrame, socialBarTop, scratch);
+                    frame = RenderScene(scene, compositorOptions, socialBarFrame, socialBarTop, scratch, TimedResolver);
                     if (_transition is { Active: true } transition)
                     {
                         frame = transition.BlendFrame(frame);
                         transition.Tick(lastTick.Elapsed.TotalMilliseconds);
                     }
+                    // Restarted EVERY frame (transition or not) so a transition's first
+                    // Tick sees per-frame time, not the pump's whole uptime.
+                    lastTick.Restart();
                     // Restarted EVERY frame (transition or not) — the old per-frame reset
                     // is what stops a transition that begins after idle from inheriting
                     // a giant ElapsedMs and completing instantly on its first tick.
@@ -394,10 +413,14 @@ public sealed class FramePump : IDisposable
         CompositorOptions options,
         VideoFrame? socialBarFrame,
         int socialBarTop,
-        byte[]? scratch = null)
+        byte[]? scratch = null,
+        Func<SceneElement, VideoFrame?>? resolver = null)
     {
+        // per-tick composites use the (timed) resolver; the rare bake uses the raw one
+        // so bake cost lands in "render" but not "resolve".
+        resolver ??= _frameResolver;
         if (_sceneGraph == null)
-            return _compositor.Render(scene, _frameResolver, null, options, socialBarFrame, socialBarTop, scratch: scratch);
+            return _compositor.Render(scene, resolver, null, options, socialBarFrame, socialBarTop, scratch: scratch);
 
         var split = _sceneGraph.GetSplitPoint(scene);
         if (split == scene.Elements.Count)
@@ -412,11 +435,11 @@ public sealed class FramePump : IDisposable
         if (baseFrame != null)
         {
             return SceneCompositor.CompositeLayers(
-                baseFrame, scene, split, _frameResolver, options, socialBarFrame, socialBarTop, scratch: scratch);
+                baseFrame, scene, split, resolver, options, socialBarFrame, socialBarTop, scratch: scratch);
         }
 
         // No static base (first layer is dynamic or empty scene) — full render.
-        return _compositor.Render(scene, _frameResolver, null, options, socialBarFrame, socialBarTop, scratch: scratch);
+        return _compositor.Render(scene, resolver, null, options, socialBarFrame, socialBarTop, scratch: scratch);
     }
 
     private void OnProcessFailed(object? sender, string message)
diff --git a/TASKS.md b/TASKS.md
index 6448101..ee5853b 100644
--- a/TASKS.md
+++ b/TASKS.md
@@ -973,7 +973,7 @@ click (volume sliders keep their manual `SetSliderValueFromClick`, harmless dupl
 
 **Goal:** record the stream output to a local file, with or without simultaneously streaming.
 
-### Status: ✅ Shipped `a9eb360` (2026-08-29) — code done (incl. manual-rename modal), build 0 warnings, 244/246 tests; **running-app verification (takes 1–5 done)**: files land (ffmpeg re-pinned month-end), **webcam-in-output + social bar visually CONFIRMED from take 3's extracted frame**, rename modal used for real (take 3 was named via it); take 3 exposed the ~2fps producer starvation and the pump stage-timing (`97ffc42`) named it in one line — `avg render 258.1ms` — **slice 1 fixed 2026-09-03** (deadline pacing per OBS video-io.c + libyuv-style row blits in `SceneCompositor`, test `Pump_Paces_To_The_Deadline_Compensating_Render_Cost`); **take 4: pacing held but render stayed 58.9ms** (2M-iteration row walk + 8.3MB/tick LOH) — **slice 2 shipped 2026-09-04**: `VideoFrame.IsOpaque` producer-contract flag → full-cover backdrop is one `Buffer.BlockCopy`; integer fixed-point bilinear general path; pump scratch pool (release strictly post-submit, owned-by-reference so cache frames are untouchable); dead per-tick `fromScene` render + the `fromSceneProvider` seam removed (BlendFrame uses `TransitionService.FromFrame` — the old render fed nothing). Tests `Pump_Pools_ScratchBuffers_Across_Frames_Without_Stale_Pixels` (the ONE) + `Composite_OpaqueFullCover_Backdrop_CopiesEveryPixel_Into_Scratch`; 59/59 per-class green, clean build 0 warnings. **take 5 ran: render 58.9→25.5ms (`138/300` ≈ 2.2x still) — cause: the per-tick chat raster (`RenderFrame` hit `RenderTargetBitmap` every tick whenever the message buffer was non-empty — the buffer survives sessions); slice 3 shipped 2026-09-04: `ChatOverlayLayer` rasters on message/config change and blits a cached frame every tick (OBS text-source pattern; test `ChatOverlayLayerCacheTests`).** **take 6 pending**: stats must show `avg render ≤ ~10ms, ≈300/300`. Known remaining churn (follow-ups, not silently done): vertical tier's final `BilinearScale` still allocates per frame; one slow tick (~15-25ms) per arriving chat message — debounced off-tick re-render if take 6 shows burst loss. **User UX spec (2026-09-04) queued behind this**: two-line top bar (LIVE rename, radio pills, Login/Logout button + avatar right-click Change Account, no account light; line 2 centered Start↔Stop grayed-until-armed) + up-front SaveFileDialog for REC (native overwrite prompt; retires the stop-time rename modal) + Go-Live dialog KEPT as preflight confirmation prefilled from the Text drawer — decisions captured in HANDOFF
+### Status: ✅ Shipped `a9eb360` (2026-08-29) — code done (incl. manual-rename modal), build 0 warnings, 244/246 tests; **running-app verification (takes 1–5 done)**: files land (ffmpeg re-pinned month-end), **webcam-in-output + social bar visually CONFIRMED from take 3's extracted frame**, rename modal used for real (take 3 was named via it); take 3 exposed the ~2fps producer starvation and the pump stage-timing (`97ffc42`) named it in one line — `avg render 258.1ms` — **slice 1 fixed 2026-09-03** (deadline pacing per OBS video-io.c + libyuv-style row blits in `SceneCompositor`, test `Pump_Paces_To_The_Deadline_Compensating_Render_Cost`); **take 4: pacing held but render stayed 58.9ms** (2M-iteration row walk + 8.3MB/tick LOH) — **slice 2 shipped 2026-09-04**: `VideoFrame.IsOpaque` producer-contract flag → full-cover backdrop is one `Buffer.BlockCopy`; integer fixed-point bilinear general path; pump scratch pool (release strictly post-submit, owned-by-reference so cache frames are untouchable); dead per-tick `fromScene` render + the `fromSceneProvider` seam removed (BlendFrame uses `TransitionService.FromFrame` — the old render fed nothing). Tests `Pump_Pools_ScratchBuffers_Across_Frames_Without_Stale_Pixels` (the ONE) + `Composite_OpaqueFullCover_Backdrop_CopiesEveryPixel_Into_Scratch`; 59/59 per-class green, clean build 0 warnings. **take 5 ran: render 58.9→25.5ms (`138/300` ≈ 2.2x still) — cause: the per-tick chat raster (`RenderFrame` hit `RenderTargetBitmap` every tick whenever the message buffer was non-empty — the buffer survives sessions); slice 3 shipped 2026-09-04: `ChatOverlayLayer` rasters on message/config change and blits a cached frame every tick (OBS text-source pattern; test `ChatOverlayLayerCacheTests`).** **take 6 ran WITHOUT attribution (35-41ms — build provenance unknown; slice 3 effectiveness UNCONFIRMED) → build-stamp shipped instead of guessing again: `Helpers/BuildStamp` GUID per build (csproj GenerateBuildStamp; incremental builds can no longer lie), wordmark superscript + startup.log line; stats split `render (resolve)` so the next take names the stage. **take 7 pending**: read stamp → confirm slice 3 build → stats must show `avg render ≤ ~10ms (resolve ≪), ≈300/300`. Known remaining churn (follow-ups, not silently done): vertical tier's final `BilinearScale` still allocates per frame; one slow tick (~15-25ms) per arriving chat message — debounced off-tick re-render if take 6 shows burst loss. **User UX spec (2026-09-04) queued behind this**: two-line top bar (LIVE rename, radio pills, Login/Logout button + avatar right-click Change Account, no account light; line 2 centered Start↔Stop grayed-until-armed) + up-front SaveFileDialog for REC (native overwrite prompt; retires the stop-time rename modal) + Go-Live dialog KEPT as preflight confirmation prefilled from the Text drawer — decisions captured in HANDOFF
 
 1. ✅ `EncoderOptions` extended with `StreamEnabled` / `RecordEnabled` / `RecordPath` (independent intent flags)
 2. ✅ `FfmpegArgs.Build` reworked into per-output blocks (stream `-f flv`, record `-f mp4`) via `AddVideoTags`
diff --git a/ai.md b/ai.md
index 7d85bc9..72237a0 100644
--- a/ai.md
+++ b/ai.md
@@ -171,7 +171,7 @@ C# / WPF (.NET 8) following MVVM:
 | `Models/` | Plain data types — Scene, Source (incl. `ClipShape`, `IsMirrored`, `VideoImageSource`), QualityOption, StreamConfig, StreamHealth, YouTubeChannel, ChatMessage, **Socials (`SocialService` enum + `SocialEntry`/`SocialsConfig` + `SocialServiceIcons`) — the social bar** |
 | `ViewModels/` | MainViewModel — `public partial class`, one file per functional area (Scenes, Background, Webcam, Audio, Trax, Socials, Streaming, Chat, Overlays, Account, License, Recording — split complete, see `ViewModels/index.md`); **Chat.cs is a thin delegating facade over `Services/ChatOverlayLayer.cs` (Commit G, first true decomposition)**; GoLiveViewModel, ReuseImageViewModel, CameraPickerViewModel, **SocialsDialogViewModel** |
 | `Services/` | YouTube OAuth2, stream/broadcast management, live chat polling, LayoutStore (SQLite), **SocialValidator (`ISocialValidator` seam + `HttpSocialValidator` default)**, **webcam: `VideoFrame` seam + `CameraDeviceInfo`/`ICameraEnumerator`/`ICameraFrameSource` interfaces + `MediaCaptureCameraEnumerator`/`MediaCaptureFrameSource` (WinRT) + `CameraManager`**, **screen capture: `IFullScreenDetector`/`Win32FullScreenDetector` + `IScreenCaptureSource`/`ScreenCaptureFrameSource` (WinRT GraphicsCapture) + `ScreenCaptureManager` + `ScreenCaptureSourceFactory` + `Direct3D11Helper`/`CaptureInterop` (COM bridges)**, **media source: `IMediaFrameSource` + `MediaVideoSource` (spawns ffmpeg `rawvideo` BGRA decode) + `MediaVideoSourceManager` (refcount-by-path session owner) + pure `RawVideoFrameReader` + `IDecodeProcess`/`FfmpegDecodeProcess` process seam (binary-stdout mirror of `IEncoderProcess`; see "Media source")**, **compositor: `SceneCompositor` + `CompositorOptions` + pure `StretchMath` + `StaticPixelCache` (see "Scene compositor")**, **audio: `IAudioSource` seam + `WasapiLoopbackAudioSource`/`WasapiMicAudioSource` (NAudio WASAPI) + `AudioMixer` + pure `AudioLevelMeter`/`WaveToFloat`/`VoiceFilterChain`/`LowShelfFilter`/`HighShelfFilter`/`NoiseGate`/`Compressor`/`AutoDucker`/`AudioRingBuffer`/`TinyResampler`/`AudioSyncDelay` + `MusicPlayer` + `IAudioPipeWriter`/`NamedPipeAudioWriter` (see "Live audio capture")**, **encoder: `IFfmpegEncoder`/`FfmpegEncoder` + `IEncoderProcess`/`FfmpegEncoderProcess` + `IFfmpegLocator`/`FfmpegLocator` + pure `FfmpegArgs`/`FfmpegProgressParser`/`FfmpegEncoderPicker` + the `FramePump` frame producer (see "Live encoder" + "Live frame pipeline")**, **notifications: `INotificationService` seam (`AppNotificationSeverity` Info/Success/Warning/Error) + `NotificationService` (Notification.Wpf toasts, see "Toast notifications")** |
-| `Helpers/` | ViewModelBase (INotifyPropertyChanged), RelayCommand, ImageCache, AppLog (file logger), FocusPreservingListBox, OAuthCredentials, **TokenStore (DPAPI session persistence)**, visibility converters |
+| `Helpers/` | ViewModelBase (INotifyPropertyChanged), RelayCommand, ImageCache, AppLog (file logger), FocusPreservingListBox, OAuthCredentials, **TokenStore (DPAPI session persistence)**, **BuildStamp (per-build GUID generated by `GenerateBuildStamp` in ytLive.csproj — wordmark superscript + startup.log line, 2026-09-04)**, visibility converters |
 | `Themes/` | `Controls.xaml` — the single dark-theme source, merged once in `App.xaml` (see `Themes/index.md`) |
 | `MainWindow.xaml` | Dark theme; layout: top bar (controls), center (preview + live controls below), left (scenes/sources), right (chat), bottom (gear + stream stats + resolution) |
 
@@ -679,7 +679,10 @@ scene each tick, resolves every element to its latest frame, composites it into
 and paces frames into the encoder at the tier's FPS. **rawvideo is stamped by ARRIVAL:** ffmpeg assigns
 pts from frame order at the declared fps — supply rate = output speed. A starved producer (pump < fps)
 ships a time-lapse, truncated file with NO error (take-2 lesson, 2026-09-01); the pump therefore logs
-`FramePump stats: n/target frames per 5s, avg render Xms submit Yms` so a slow stage names itself. **Pattern — everything is a constructor-injected
+`FramePump stats: n/target frames per 5s, avg render Xms (resolve R), avg submit Yms` so a slow stage names itself — and since 2026-09-04 so does the BUILD: every build gets a GUID stamped
+into `Helpers/BuildStamp` (csproj `GenerateBuildStamp` target, fresh per compile — no lying incremental build), shown as the wordmark superscript and logged at startup
+("Build xxxxxxxx (compiled ...)"). **Take 6 (stamp-less, ambiguous): render 35-41ms with slice 3 built or not unknown — attribution is why the stamp exists; takes 7+ are
+readable.** If the breakdown says resolve dominates, the suspects are pre-cached chat/config thrash or the web frame; if blit dominates, the general-path element sizes. **Pattern — everything is a constructor-injected
 seam:** `Func<Scene?>`, `Func<SceneElement, VideoFrame?>` resolver, `Func<CompositorOptions>`,
 `Func<EncoderOptions?>`, `Func<IFfmpegEncoder>`, `Action<string>` log, and an injectable pacing delay
 (default `Task.Delay`; tests inject `Task.Yield`). The pump is free of WPF and of the capture managers.
diff --git a/ytLive.csproj b/ytLive.csproj
index f11b987..85c810b 100644
--- a/ytLive.csproj
+++ b/ytLive.csproj
@@ -19,6 +19,30 @@
     <Page Remove="ytLive.Tests\**" />
   </ItemGroup>
 
+  <!-- Per-build identity stamp (2026-09-04): takes 1–6 could not be attributed to an
+       exact binary — render perf "fixes" were being judged against builds we could not
+       prove were running. A fresh GUID per build makes an incremental compile impossible
+       (that is the point: every exe you launch was compiled NOW), the wordmark shows the
+       id, and startup.log records id + build time. -->
+  <Target Name="GenerateBuildStamp" BeforeTargets="CoreCompile">
+    <PropertyGroup>
+      <BuildStampFile>$(IntermediateOutputPath)BuildStamp.g.cs</BuildStampFile>
+      <BuildStampId>$([System.Guid]::NewGuid().ToString('N').Substring(0,8))</BuildStampId>
+      <BuildStampTime>$([System.DateTime]::Now.ToString('yyyy-MM-dd HH:mm:ss'))</BuildStampTime>
+    </PropertyGroup>
+    <ItemGroup>
+      <BuildStampLines Include="// &lt;auto-generated&gt; Per-build identity (ytLive.csproj GenerateBuildStamp)."/>
+      <BuildStampLines Include="// Shown as the wordmark superscript and logged at startup: proof of which"/>
+      <BuildStampLines Include="// binary produced a test recording (2026-09-04). Never edit by hand."/>
+      <BuildStampLines Include="namespace ytLive.Helpers%3B"/>
+      <BuildStampLines Include="public static class BuildStamp { public const string Id = &quot;$(BuildStampId)&quot;%3B public const string BuiltLocal = &quot;$(BuildStampTime)&quot;%3B }"/>
+    </ItemGroup>
+    <WriteLinesToFile File="$(BuildStampFile)" Lines="@(BuildStampLines)" Overwrite="true" WriteOnlyWhenDifferent="false" />
+    <ItemGroup>
+      <Compile Include="$(BuildStampFile)" />
+    </ItemGroup>
+  </Target>
+
   <ItemGroup>
     <Resource Include="Assets\llamacasty-icon.png" />
     <Resource Include="Assets\llamacasty-logo.jpg" />