diff --git a/.github/skills/perf-compare/SKILL.md b/.github/skills/perf-compare/SKILL.md
index 3b5e45eb2..213f359b5 100644
--- a/.github/skills/perf-compare/SKILL.md
+++ b/.github/skills/perf-compare/SKILL.md
@@ -58,8 +58,8 @@ reconcile/diff phase — those read *n/a*.
    (committed) and `git status --porcelain` (uncommitted). If both are empty,
    tell the user there is nothing to compare and stop.
 3. **Capability check.** The harness opens a real WinUI window. If you are
-   running on a headless box, runs will crash with `0xC000027B` right after
-   `MountAndActivate ok`. If a first run fails that way, do **not** keep
+   running on a headless box, runs will crash with `0xC000027B` during
+   first-frame window activation. If a first run fails that way, do **not** keep
    retrying — report it (see [Failure handling](#failure-handling)).
 
 ### 2. Set up the `main` baseline worktree
diff --git a/src/Reactor/Hosting/ReactorApp.cs b/src/Reactor/Hosting/ReactorApp.cs
index 01ad70399..7ed6264c2 100644
--- a/src/Reactor/Hosting/ReactorApp.cs
+++ b/src/Reactor/Hosting/ReactorApp.cs
@@ -480,30 +480,16 @@ internal static ReactorWindow OpenWindowCore(
         Action<ReactorHost>? configure,
         bool excludeFromShutdownPolicy = false)
     {
-        Console.Error.WriteLine("[embed:trace] OpenWindowCore enter (embed=" + (spec.Embed is not null) + ")");
-        ReactorWindow window;
-        try
-        {
-            window = new ReactorWindow(spec);
-            window.ExcludeFromShutdownPolicy = excludeFromShutdownPolicy;
-            Console.Error.WriteLine("[embed:trace] OpenWindowCore: ReactorWindow ctor ok");
-        }
-        catch (Exception ex)
-        {
-            Console.Error.WriteLine("[embed:trace] ReactorWindow ctor THREW: " + ex);
-            throw;
-        }
-        try { configure?.Invoke(window.Host); Console.Error.WriteLine("[embed:trace] OpenWindowCore: configure ok"); }
-        catch (Exception ex) { Console.Error.WriteLine("[embed:trace] configure THREW: " + ex); throw; }
+        ReactorWindow window = new ReactorWindow(spec);
+        window.ExcludeFromShutdownPolicy = excludeFromShutdownPolicy;
+        configure?.Invoke(window.Host);
         RegisterWindow(window);
         try
         {
             window.MountAndActivate(rootFactory, renderFunc);
-            Console.Error.WriteLine("[embed:trace] OpenWindowCore: MountAndActivate ok");
         }
-        catch (Exception ex)
+        catch
         {
-            Console.Error.WriteLine("[embed:trace] MountAndActivate THREW: " + ex);
             UnregisterWindow(window);
             try { window.Dispose(); } catch { /* best effort */ }
             throw;
diff --git a/src/Reactor/Hosting/ReactorWindow.cs b/src/Reactor/Hosting/ReactorWindow.cs
index e0644ac48..ca56fb7c5 100644
--- a/src/Reactor/Hosting/ReactorWindow.cs
+++ b/src/Reactor/Hosting/ReactorWindow.cs
@@ -338,27 +338,14 @@ internal ReactorWindow(WindowSpec spec)
 
         if (spec.Embed is { } embed)
         {
-            Console.Error.WriteLine("[embed:trace] entering embed setup (style=" + embed.Style + " hostPid=" + embed.HostPid + ")");
-            try
-            {
-                VerifyEmbedDpiAwareness(embed.Style);
-                Console.Error.WriteLine("[embed:trace] VerifyEmbedDpiAwareness ok");
-                ApplyEmbedInitialStyles(embed.Style);
-                Console.Error.WriteLine("[embed:trace] ApplyEmbedInitialStyles ok");
-                _embedWatchdog = new EmbedHostWatchdog();
-                _embedWatchdog.Start(embed.HostPid, () =>
-                {
-                    try { NativeShell.SetParent(_hwnd, 0); } catch { }
-                    Environment.Exit(0);
-                });
-                Console.Error.WriteLine("[embed:trace] EmbedHostWatchdog started");
-            }
-            catch (Exception ex)
+            VerifyEmbedDpiAwareness(embed.Style);
+            ApplyEmbedInitialStyles(embed.Style);
+            _embedWatchdog = new EmbedHostWatchdog();
+            _embedWatchdog.Start(embed.HostPid, () =>
             {
-                Console.Error.WriteLine("[embed:trace] embed setup THREW: " + ex.GetType().FullName + ": " + ex.Message);
-                Console.Error.WriteLine(ex.ToString());
-                throw;
-            }
+                try { NativeShell.SetParent(_hwnd, 0); } catch { }
+                Environment.Exit(0);
+            });
         }
 
         // Snapshot initial per-window DPI before applying spec sizing so the
diff --git a/tests/stress_perf/ci/README.md b/tests/stress_perf/ci/README.md
index 9dce53875..bcdfac974 100644
--- a/tests/stress_perf/ci/README.md
+++ b/tests/stress_perf/ci/README.md
@@ -234,7 +234,7 @@ default `-Reps 12` (drop to e.g. `-Reps 3` only for a quick smoke run).
 
 ## Troubleshooting
 
-- **Run crashes with `0xC000027B` right after "MountAndActivate ok".** That is a
+- **Run crashes with `0xC000027B` during first-frame window activation.** That is a
   stowed XAML/compositor exception. Most often the box cannot composite a real
   WinUI window (headless server, no GPU/desktop session, or an RDP session
   without composition) — run from an interactive desktop session. **On an ARM64