fix(args): align feature set with stock Chrome for the Windows font profile

Playwright's launch defaults switch off a feature stock Chrome ships enabled.
When the Windows font-metrics profile is requested, re-enable it so the feature
set matches a real browser rather than a test harness. Merged into any existing
--enable-features value instead of appending a second flag.

Python, JS and .NET wrappers.

cloakbrowser/browser.py

@@ -1222,6 +1222,18 @@ def build_args(
                 logger.debug("Arg override: %s -> %s", seen[key], arg)
             seen[key] = arg
 
+    # Playwright's default launch args switch off a browser feature that stock Chrome
+    # ships enabled. Re-enable it alongside the Windows font-metrics profile so the
+    # feature set matches a stock browser rather than a test harness. Merged into any
+    # existing --enable-features value rather than added as a second flag.
+    if "--fingerprint-windows-font-metrics" in seen:
+        key = "--enable-features"
+        current = seen[key].split("=", 1)[-1] if key in seen else ""
+        features = [f for f in current.split(",") if f]
+        if "MediaRouter" not in features:
+            features.append("MediaRouter")
+            seen[key] = f"{key}={','.join(features)}"
+
     # Timezone/locale flags are independent of stealth_args — always inject when set
     if timezone:
         key = "--fingerprint-timezone"

dotnet/src/CloakBrowser/CloakLauncher.cs

@@ -376,6 +376,24 @@ public static class CloakLauncher
                 Set(arg.Split('=', 2)[0], arg);
         }
 
+        // Playwright's default launch args switch off a browser feature that stock Chrome
+        // ships enabled. Re-enable it alongside the Windows font-metrics profile so the
+        // feature set matches a stock browser rather than a test harness. Merged into any
+        // existing --enable-features value rather than added as a second flag.
+        if (seen.ContainsKey("--fingerprint-windows-font-metrics"))
+        {
+            const string key = "--enable-features";
+            var current = seen.TryGetValue(key, out var existing)
+                ? existing.Split('=', 2).ElementAtOrDefault(1) ?? ""
+                : "";
+            var features = current.Split(',', StringSplitOptions.RemoveEmptyEntries).ToList();
+            if (!features.Contains("MediaRouter"))
+            {
+                features.Add("MediaRouter");
+                Set(key, $"{key}={string.Join(",", features)}");
+            }
+        }
+
         if (!string.IsNullOrEmpty(timezone))
             Set("--fingerprint-timezone", $"--fingerprint-timezone={timezone}");
 

js/src/args.ts

@@ -38,6 +38,20 @@ export function buildArgs(options: LaunchOptions): string[] {
       seen.set(key, arg);
     }
   }
+  // Playwright's default launch args switch off a browser feature that stock Chrome
+  // ships enabled. Re-enable it alongside the Windows font-metrics profile so the
+  // feature set matches a stock browser rather than a test harness. Merged into any
+  // existing --enable-features value rather than added as a second flag.
+  if (seen.has("--fingerprint-windows-font-metrics")) {
+    const key = "--enable-features";
+    const current = seen.get(key)?.split("=")[1] ?? "";
+    const features = current.split(",").filter(Boolean);
+    if (!features.includes("MediaRouter")) {
+      features.push("MediaRouter");
+      seen.set(key, `${key}=${features.join(",")}`);
+    }
+  }
+
   if (options.timezone) {
     const key = "--fingerprint-timezone";
     const flag = `${key}=${options.timezone}`;