feat: wire timezone/locale params to Chromium binary flags

launch() and launch_context() now inject --timezone and --lang binary
flags when timezone/locale params are set. Previously only the Playwright
context layer was configured, leaving a detectable mismatch that CreepJS
flagged as a bot signal.

Closes: WM5

js/tests/config.test.ts

@@ -6,6 +6,7 @@ import {
   getBinaryDir,
   getDownloadUrl,
 } from "../src/config.js";
+import { _buildArgsForTest } from "../src/playwright.js";
 
 describe("config", () => {
   it("CHROMIUM_VERSION matches expected format", () => {
@@ -65,3 +66,34 @@ describe("config", () => {
     expect(url).toContain("cloakbrowser.dev");
   });
 });
+
+describe("buildArgs timezone/locale", () => {
+  it("injects --timezone when timezone is set", () => {
+    const args = _buildArgsForTest({ timezone: "America/New_York" });
+    expect(args).toContain("--timezone=America/New_York");
+  });
+
+  it("injects --lang when locale is set", () => {
+    const args = _buildArgsForTest({ locale: "en-US" });
+    expect(args).toContain("--lang=en-US");
+  });
+
+  it("injects both when both are set", () => {
+    const args = _buildArgsForTest({ timezone: "Europe/Berlin", locale: "de-DE" });
+    expect(args).toContain("--timezone=Europe/Berlin");
+    expect(args).toContain("--lang=de-DE");
+  });
+
+  it("injects timezone/locale even when stealthArgs=false", () => {
+    const args = _buildArgsForTest({ stealthArgs: false, timezone: "America/New_York", locale: "en-US" });
+    expect(args).toContain("--timezone=America/New_York");
+    expect(args).toContain("--lang=en-US");
+    expect(args.some(a => a.startsWith("--fingerprint="))).toBe(false);
+  });
+
+  it("does not inject flags when not set", () => {
+    const args = _buildArgsForTest({});
+    expect(args.some(a => a.startsWith("--timezone="))).toBe(false);
+    expect(args.some(a => a.startsWith("--lang="))).toBe(false);
+  });
+});

tests/test_build_args.py

@@ -0,0 +1,46 @@
+"""Unit tests for _build_args timezone/locale injection."""
+
+from cloakbrowser.browser import _build_args
+
+
+def test_timezone_injected():
+    """--timezone flag should appear when timezone is set."""
+    args = _build_args(stealth_args=True, extra_args=None, timezone="America/New_York")
+    assert "--timezone=America/New_York" in args
+
+
+def test_locale_injected():
+    """--lang flag should appear when locale is set."""
+    args = _build_args(stealth_args=True, extra_args=None, locale="en-US")
+    assert "--lang=en-US" in args
+
+
+def test_both_injected():
+    """Both flags should appear when both are set."""
+    args = _build_args(stealth_args=True, extra_args=None, timezone="Europe/Berlin", locale="de-DE")
+    assert "--timezone=Europe/Berlin" in args
+    assert "--lang=de-DE" in args
+
+
+def test_timezone_independent_of_stealth_args():
+    """--timezone should be injected even when stealth_args=False."""
+    args = _build_args(stealth_args=False, extra_args=None, timezone="America/New_York", locale="en-US")
+    assert "--timezone=America/New_York" in args
+    assert "--lang=en-US" in args
+    # No stealth fingerprint args
+    assert not any(a.startswith("--fingerprint=") for a in args)
+
+
+def test_no_flags_when_not_set():
+    """No timezone/lang flags when params are None."""
+    args = _build_args(stealth_args=True, extra_args=None)
+    assert not any(a.startswith("--timezone=") for a in args)
+    assert not any(a.startswith("--lang=") for a in args)
+
+
+def test_extra_args_preserved():
+    """Extra args should still be included alongside timezone/locale."""
+    args = _build_args(stealth_args=True, extra_args=["--disable-gpu"], timezone="Asia/Tokyo", locale="ja-JP")
+    assert "--disable-gpu" in args
+    assert "--timezone=Asia/Tokyo" in args
+    assert "--lang=ja-JP" in args