diff --git a/src/E2E/Expect/ScreenshotAssertion.cs b/src/E2E/Expect/ScreenshotAssertion.cs
index 91353468..a068c9d8 100644
--- a/src/E2E/Expect/ScreenshotAssertion.cs
+++ b/src/E2E/Expect/ScreenshotAssertion.cs
@@ -253,9 +253,7 @@ private static async Task KeepAsync(Run run, Locator? subject, RgbaImage? expect
         }
 
         Directory.CreateDirectory(Path.GetDirectoryName(run.File)!);
-        var temporary = run.File + "." + Guid.NewGuid().ToString("N")[..8] + ".tmp";
-        await System.IO.File.WriteAllBytesAsync(temporary, ImageOps.EncodePng(settled)).ConfigureAwait(false);
-        System.IO.File.Move(temporary, run.File, overwrite: true);
+        await AtomicWrite.WriteFileAtomicAsync(run.File, ImageOps.EncodePng(settled)).ConfigureAwait(false);
         store.MarkWritten(run.File);
         if (expected is null && !store.Update)
         {
diff --git a/src/E2E/Internal/AiTrace.cs b/src/E2E/Internal/AiTrace.cs
index b7ecfc54..0251845b 100644
--- a/src/E2E/Internal/AiTrace.cs
+++ b/src/E2E/Internal/AiTrace.cs
@@ -901,16 +901,13 @@ public void Flush(bool force)
                 _pending = null;
 
                 Directory.CreateDirectory(System.IO.Path.GetDirectoryName(Path)!);
-                var temp = Path + "." + Guid.NewGuid().ToString("n") + ".tmp";
                 try
                 {
-                    File.WriteAllText(temp, JsonSerializer.Serialize(Collector.Document(), Options));
-                    File.Move(temp, Path, overwrite: true);
+                    AtomicWrite.WriteFileAtomic(Path, JsonSerializer.Serialize(Collector.Document(), Options));
                     _dirty = false;
                 }
                 finally
                 {
-                    File.Delete(temp);
                     _written = Stopwatch.GetTimestamp();
                 }
             }
diff --git a/src/E2E/Internal/AtomicWrite.cs b/src/E2E/Internal/AtomicWrite.cs
index 3ca864ae..6225ff96 100644
--- a/src/E2E/Internal/AtomicWrite.cs
+++ b/src/E2E/Internal/AtomicWrite.cs
@@ -27,12 +27,16 @@ internal static class AtomicWrite
     private static readonly UTF8Encoding Utf8 = new(false);
 
     /// <summary>Writes <paramref name="content"/> to <paramref name="filePath"/> atomically; a failed write leaves no temporary file behind.</summary>
-    public static async Task WriteFileAtomicAsync(string filePath, string content, CancellationToken cancellationToken = default)
+    public static Task WriteFileAtomicAsync(string filePath, string content, CancellationToken cancellationToken = default) =>
+        WriteFileAtomicAsync(filePath, Utf8.GetBytes(content), cancellationToken);
+
+    /// <summary>The bytes form of <see cref="WriteFileAtomicAsync(string, string, CancellationToken)"/> (upstream accepts a <c>Uint8Array</c>).</summary>
+    public static async Task WriteFileAtomicAsync(string filePath, byte[] content, CancellationToken cancellationToken = default)
     {
         var temporary = TemporaryPath(filePath);
         try
         {
-            await File.WriteAllTextAsync(temporary, content, Utf8, cancellationToken).ConfigureAwait(false);
+            await File.WriteAllBytesAsync(temporary, content, cancellationToken).ConfigureAwait(false);
             for (var attempt = 1; ; attempt++)
             {
                 try