fix: preserve native clock precision by default

Author: KSemenenko

README.md

@@ -139,7 +139,7 @@ On Chromium, `context.ApplyStealthAsync` also initializes dedicated, module, sha
 |-------|-------------|--------|
 | CDP detection | Masks Chrome DevTools Protocol traces | `CdpDetection` |
 | Automation properties | Removes `cdc_*`, `$cdc_*`, `domAutomationController` | `AutomationProperties` |
-| Performance jitter | Monotonic millisecond clock precision; enabled by default | `PerformanceJitter` |
+| Performance jitter | Optional monotonic millisecond clock precision; disabled by default to preserve native timing | `PerformanceJitter` |
 
 ### DOM & Internals
 | Patch | Description | Config |
@@ -174,6 +174,12 @@ string[] args = PlaywrightStealthExtensions.StealthArgs;
 
 On Linux these arguments select ANGLE's native OpenGL backend through EGL and allow the installed driver, including Mesa on CI runners, instead of falling back to SwiftShader. This also supports headless rendering without a display. WebGL rendering and shader reporting remain native in pages and workers. `LaunchStealthAsync` preserves an explicitly supplied `--use-angle` or `--use-gl` backend. Linux hosts need a working EGL/OpenGL driver; headful runs also need a display.
 
+For Ubuntu runners, install the native graphics libraries alongside Playwright's browser dependencies:
+
+```bash
+sudo apt-get install -y --no-install-recommends libegl1 libegl-mesa0 libgles2 libgl1-mesa-dri
+```
+
 ## Configuration Reference
 
 ### Toggle Options (bool)

src/Playwright.Stealth/StealthConfig.cs

@@ -31,7 +31,7 @@ public sealed class StealthConfig
     public bool AutomationProperties { get; init; } = true;
     public int NavigatorMaxTouchPoints { get; init; } = -1;
     public bool CanvasFingerprint { get; init; }
-    public bool PerformanceJitter { get; init; } = true;
+    public bool PerformanceJitter { get; init; }
     public bool NavigatorPdfViewer { get; init; } = true;
     public bool AudioContext { get; init; }
 

tests/Playwright.Stealth.Tests/StealthCompatibilityTests.cs

@@ -39,6 +39,7 @@ await WithBrowserAsync(headless, async browser =>
                         [HTMLImageElement.prototype, 'naturalHeight'],
                         [HTMLIFrameElement.prototype, 'contentWindow'],
                         [SpeechSynthesis.prototype, 'getVoices'],
+                        [Performance.prototype, 'now'],
                         [Permissions.prototype, 'query'],
                         [Navigator.prototype, 'webdriver'],
                         [WebGLRenderingContext.prototype, 'getParameter'],
@@ -121,18 +122,20 @@ public async Task LaunchStealth_DefaultOptions_RendersWebGlInPageAndWorker(bool
     }
 
     [Test]
-    [Arguments(true)]
-    [Arguments(false)]
-    public async Task ApplyStealth_PerformanceClock_RemainsMonotonicAndPreservesNativeErrors(bool headless)
+    [Arguments(true, false)]
+    [Arguments(false, false)]
+    [Arguments(true, true)]
+    [Arguments(false, true)]
+    public async Task ApplyStealth_PerformanceClock_RemainsMonotonicAndPreservesNativeErrors(bool headless, bool reducePrecision)
     {
         await WithBrowserAsync(headless, async browser =>
         {
             await using IBrowserContext context = await browser.NewContextAsync();
-            await context.ApplyStealthAsync();
+            await context.ApplyStealthAsync(new() { PerformanceJitter = reducePrecision });
             IPage page = await context.NewPageAsync();
             await page.GotoAsync("about:blank");
             string[] failures = await page.EvaluateAsync<string[]>("""
-                () => {
+                reducePrecision => {
                     const failures = [];
                     const now = Performance.prototype.now;
                     try { now.call({}); failures.push('accepted invalid receiver'); }
@@ -142,6 +145,7 @@ await WithBrowserAsync(headless, async browser =>
                     let previous = performance.now();
                     for (let i = 0; i < 10000; i++) {
                         const current = performance.now();
+                        if (reducePrecision && !Number.isInteger(current)) { failures.push('clock precision opt-in ignored'); break; }
                         if (current < previous) { failures.push('clock moved backwards'); break; }
                         previous = current;
                     }
@@ -150,7 +154,7 @@ await WithBrowserAsync(headless, async browser =>
                     if (Math.abs(performance.timeOrigin + performance.now() - Date.now()) > 1000) failures.push('clock time origin');
                     return failures;
                 }
-                """);
+                """, reducePrecision);
             await Assert.That(failures).IsEmpty();
         });
     }

tests/Playwright.Stealth.Tests/StealthConfigTests.cs

@@ -21,7 +21,7 @@ public async Task Defaults_Should_Enable_Core_Stealth_Scripts()
         await Assert.That(config.Languages.Count).IsEqualTo(0);
         await Assert.That(config.CanvasFingerprint).IsFalse();
         await Assert.That(config.AudioContext).IsFalse();
-        await Assert.That(config.PerformanceJitter).IsTrue();
+        await Assert.That(config.PerformanceJitter).IsFalse();
         await Assert.That(config.Vendor).IsEmpty();
         await Assert.That(config.Renderer).IsEmpty();
     }

tests/Playwright.Stealth.Tests/StealthScriptProviderTests.cs

@@ -30,7 +30,7 @@ public async Task BuildScripts_Should_Include_Default_Scripts()
         await Assert.That(ContainsScript(scripts, "automationPatterns")).IsTrue();
         await Assert.That(ContainsScript(scripts, "Object.getPrototypeOf(navigator), 'maxTouchPoints'")).IsFalse();
         await Assert.That(ContainsScript(scripts, "noiseSeed")).IsFalse();
-        await Assert.That(ContainsScript(scripts, "Math.floor(utils.cache.Reflect.apply")).IsTrue();
+        await Assert.That(ContainsScript(scripts, "Math.floor(utils.cache.Reflect.apply")).IsFalse();
         await Assert.That(ContainsScript(scripts, "pdfViewerEnabled")).IsTrue();
         await Assert.That(ContainsScript(scripts, "const audioNoiseSeed")).IsFalse();
     }