fix: use binary flags for timezone/locale instead of detectable CDP emulation

- Remove locale and timezone_id from Playwright context kwargs (CDP)
- Pass timezone via --fingerprint-timezone binary flag (process-wide)
- Pass locale via --lang + --fingerprint-locale binary flags
- Accept both timezone and timezone_id param names silently (no deprecation)
- Update all wrapper tests to verify binary args, not CDP context params

cloakbrowser/browser.py

@@ -16,7 +16,6 @@ from __future__ import annotations
 
 import logging
 import os
-import warnings
 from typing import Any, Literal, TypedDict
 from urllib.parse import unquote, urlparse, urlunparse
 
@@ -26,10 +25,9 @@ from .download import ensure_binary
 logger = logging.getLogger("cloakbrowser")
 
 
-def _migrate_timezone_id(timezone: str | None, kwargs: dict[str, Any]) -> str | None:
-    """Pop deprecated timezone_id from kwargs, warn, return resolved timezone."""
+def _resolve_timezone(timezone: str | None, kwargs: dict[str, Any]) -> str | None:
+    """Accept both timezone and timezone_id — either works, no warning."""
     if "timezone_id" in kwargs:
-        warnings.warn("timezone_id is deprecated, use timezone instead", FutureWarning, stacklevel=3)
         if timezone is None:
             timezone = kwargs.pop("timezone_id")
         else:
@@ -279,7 +277,7 @@ def launch_persistent_context(
     """
     sync_playwright = _import_sync_playwright(_resolve_backend(backend))
 
-    timezone = _migrate_timezone_id(timezone, kwargs)
+    timezone = _resolve_timezone(timezone, kwargs)
 
     binary_path = ensure_binary()
     timezone, locale = _maybe_resolve_geoip(geoip, proxy, timezone, locale)
@@ -291,14 +289,12 @@ def launch_persistent_context(
         user_data_dir,
     )
 
+    # locale and timezone are set via binary flags (--lang, --fingerprint-timezone)
+    # — NOT via Playwright context kwargs which use detectable CDP emulation.
     context_kwargs: dict[str, Any] = {}
     if user_agent:
         context_kwargs["user_agent"] = user_agent
     context_kwargs["viewport"] = viewport or DEFAULT_VIEWPORT
-    if locale:
-        context_kwargs["locale"] = locale
-    if timezone:
-        context_kwargs["timezone_id"] = timezone
     if color_scheme:
         context_kwargs["color_scheme"] = color_scheme
     context_kwargs.update(kwargs)
@@ -394,7 +390,7 @@ async def launch_persistent_context_async(
     """
     async_playwright = _import_async_playwright(_resolve_backend(backend))
 
-    timezone = _migrate_timezone_id(timezone, kwargs)
+    timezone = _resolve_timezone(timezone, kwargs)
 
     binary_path = ensure_binary()
     timezone, locale = _maybe_resolve_geoip(geoip, proxy, timezone, locale)
@@ -406,14 +402,12 @@ async def launch_persistent_context_async(
         user_data_dir,
     )
 
+    # locale and timezone are set via binary flags (--lang, --fingerprint-timezone)
+    # — NOT via Playwright context kwargs which use detectable CDP emulation.
     context_kwargs: dict[str, Any] = {}
     if user_agent:
         context_kwargs["user_agent"] = user_agent
     context_kwargs["viewport"] = viewport or DEFAULT_VIEWPORT
-    if locale:
-        context_kwargs["locale"] = locale
-    if timezone:
-        context_kwargs["timezone_id"] = timezone
     if color_scheme:
         context_kwargs["color_scheme"] = color_scheme
     context_kwargs.update(kwargs)
@@ -491,25 +485,21 @@ def launch_context(
     Returns:
         Playwright BrowserContext object.
     """
-    timezone = _migrate_timezone_id(timezone, kwargs)
+    timezone = _resolve_timezone(timezone, kwargs)
 
     # Resolve geoip BEFORE launch() to avoid double-resolution and ensure
-    # resolved values flow to both binary flags AND context params
+    # resolved values flow to binary flags
     timezone, locale = _maybe_resolve_geoip(geoip, proxy, timezone, locale)
-    # Skip --fingerprint-timezone binary flag: it only applies to the default
-    # context and interferes with Playwright's timezone_id on new contexts.
-    # Timezone is set via browser.new_context(timezone_id=...) below instead.
+    # --fingerprint-timezone is process-wide (reads CommandLine in renderer),
+    # so it applies to ALL contexts, not just the default one.
+    # locale and timezone are set via binary flags only — no CDP emulation.
     browser = launch(headless=headless, proxy=proxy, args=args, stealth_args=stealth_args,
-                     timezone=None, locale=locale, backend=backend)
+                     timezone=timezone, locale=locale, backend=backend)
 
     context_kwargs: dict[str, Any] = {}
     if user_agent:
         context_kwargs["user_agent"] = user_agent
     context_kwargs["viewport"] = viewport or DEFAULT_VIEWPORT
-    if locale:
-        context_kwargs["locale"] = locale
-    if timezone:
-        context_kwargs["timezone_id"] = timezone
     if color_scheme:
         context_kwargs["color_scheme"] = color_scheme
     context_kwargs.update(kwargs)
@@ -646,11 +636,11 @@ def _build_args(
             logger.debug("Arg override: %s -> %s", seen[key], flag)
         seen[key] = flag
     if locale:
-        key = "--lang"
-        flag = f"{key}={locale}"
-        if key in seen:
-            logger.debug("Arg override: %s -> %s", seen[key], flag)
-        seen[key] = flag
+        for key in ("--lang", "--fingerprint-locale"):
+            flag = f"{key}={locale}"
+            if key in seen:
+                logger.debug("Arg override: %s -> %s", seen[key], flag)
+            seen[key] = flag
 
     return list(seen.values())
 

js/src/args.ts

@@ -38,12 +38,13 @@ export function buildArgs(options: LaunchOptions): string[] {
     seen.set(key, flag);
   }
   if (options.locale) {
-    const key = "--lang";
-    const flag = `${key}=${options.locale}`;
-    if (seen.has(key)) {
-      if (DEBUG) console.debug(`[cloakbrowser] Arg override: ${seen.get(key)} -> ${flag}`);
+    for (const k of ["--lang", "--fingerprint-locale"] as const) {
+      const flag = `${k}=${options.locale}`;
+      if (seen.has(k)) {
+        if (DEBUG) console.debug(`[cloakbrowser] Arg override: ${seen.get(k)} -> ${flag}`);
+      }
+      seen.set(k, flag);
     }
-    seen.set(key, flag);
   }
   return [...seen.values()];
 }

js/src/playwright.ts

@@ -11,10 +11,9 @@ import { ensureBinary } from "./download.js";
 import { parseProxyUrl } from "./proxy.js";
 import { maybeResolveGeoip } from "./geoip.js";
 
-/** @internal Migrate deprecated timezoneId → timezone, warn once. Exported for testing. */
-export function migrateTimezoneId<T extends { timezone?: string; timezoneId?: string }>(options: T): T {
+/** @internal Accept both timezone and timezoneId — either works, no warning. Exported for testing. */
+export function resolveTimezone<T extends { timezone?: string; timezoneId?: string }>(options: T): T {
   if (options.timezoneId != null) {
-    console.warn("[cloakbrowser] timezoneId is deprecated, use timezone instead");
     const merged = { ...options, timezone: options.timezone ?? options.timezoneId };
     delete (merged as any).timezoneId;
     return merged;
@@ -86,21 +85,19 @@ export async function launch(options: LaunchOptions = {}): Promise<Browser> {
 export async function launchContext(
   options: LaunchContextOptions = {}
 ): Promise<BrowserContext> {
-  options = migrateTimezoneId(options);
+  options = resolveTimezone(options);
   // Resolve geoip BEFORE launch() to avoid double-resolution
   const resolved = await maybeResolveGeoip(options);
-  // Skip --fingerprint-timezone binary flag: it only applies to the default
-  // context and interferes with Playwright's timezoneId on new contexts.
-  // Timezone is set via browser.newContext(timezoneId: ...) below instead.
-  const browser = await launch({ ...options, ...resolved, geoip: false, timezone: undefined });
+  // --fingerprint-timezone is process-wide (reads CommandLine in renderer),
+  // so it applies to ALL contexts, not just the default one.
+  // locale and timezone are set via binary flags only — no CDP emulation.
+  const browser = await launch({ ...options, ...resolved, geoip: false });
 
   let context: BrowserContext;
   try {
     context = await browser.newContext({
       ...(options.userAgent ? { userAgent: options.userAgent } : {}),
       viewport: options.viewport ?? DEFAULT_VIEWPORT,
-      ...(resolved.locale ? { locale: resolved.locale } : {}),
-      ...(resolved.timezone ? { timezoneId: resolved.timezone } : {}),
       ...(options.colorScheme ? { colorScheme: options.colorScheme } : {}),
     });
   } catch (err) {
@@ -153,13 +150,15 @@ export async function launchContext(
 export async function launchPersistentContext(
   options: LaunchPersistentContextOptions
 ): Promise<BrowserContext> {
-  options = migrateTimezoneId(options);
+  options = resolveTimezone(options);
   const { chromium } = await import("playwright-core");
 
   const binaryPath = process.env.CLOAKBROWSER_BINARY_PATH || (await ensureBinary());
   const resolved = await maybeResolveGeoip(options);
   const args = buildArgs({ ...options, ...resolved });
 
+  // locale and timezone are set via binary flags (--lang, --fingerprint-timezone)
+  // — NOT via Playwright context kwargs which use detectable CDP emulation.
   const context = await chromium.launchPersistentContext(options.userDataDir, {
     executablePath: binaryPath,
     headless: options.headless ?? true,
@@ -170,8 +169,6 @@ export async function launchPersistentContext(
       : {}),
     ...(options.userAgent ? { userAgent: options.userAgent } : {}),
     viewport: options.viewport ?? DEFAULT_VIEWPORT,
-    ...(resolved.locale ? { locale: resolved.locale } : {}),
-    ...(resolved.timezone ? { timezoneId: resolved.timezone } : {}),
     ...(options.colorScheme ? { colorScheme: options.colorScheme } : {}),
     ...options.launchOptions,
   });

js/src/types.ts

@@ -39,7 +39,7 @@ export interface LaunchContextOptions extends LaunchOptions {
   viewport?: { width: number; height: number };
   /** Browser locale, e.g. "en-US". */
   locale?: string;
-  /** @deprecated Use `timezone` (inherited from LaunchOptions) instead. */
+  /** IANA timezone — alias for `timezone`. Either works. */
   timezoneId?: string;
   /** Color scheme preference — 'light', 'dark', or 'no-preference'. */
   colorScheme?: "light" | "dark" | "no-preference";

js/tests/config.test.ts

@@ -9,7 +9,7 @@ import {
   getDownloadUrl,
   getFallbackDownloadUrl,
 } from "../src/config.js";
-import { _buildArgsForTest, migrateTimezoneId } from "../src/playwright.js";
+import { _buildArgsForTest, resolveTimezone } from "../src/playwright.js";
 
 describe("config", () => {
   it("CHROMIUM_VERSION matches expected format", () => {
@@ -97,21 +97,24 @@ describe("buildArgs timezone/locale", () => {
     expect(args).toContain("--fingerprint-timezone=America/New_York");
   });
 
-  it("injects --lang when locale is set", () => {
+  it("injects --lang and --fingerprint-locale when locale is set", () => {
     const args = _buildArgsForTest({ locale: "en-US" });
     expect(args).toContain("--lang=en-US");
+    expect(args).toContain("--fingerprint-locale=en-US");
   });
 
   it("injects both when both are set", () => {
     const args = _buildArgsForTest({ timezone: "Europe/Berlin", locale: "de-DE" });
     expect(args).toContain("--fingerprint-timezone=Europe/Berlin");
     expect(args).toContain("--lang=de-DE");
+    expect(args).toContain("--fingerprint-locale=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("--fingerprint-timezone=America/New_York");
     expect(args).toContain("--lang=en-US");
+    expect(args).toContain("--fingerprint-locale=en-US");
     expect(args.some(a => a.startsWith("--fingerprint="))).toBe(false);
   });
 
@@ -119,6 +122,7 @@ describe("buildArgs timezone/locale", () => {
     const args = _buildArgsForTest({});
     expect(args.some(a => a.startsWith("--fingerprint-timezone="))).toBe(false);
     expect(args.some(a => a.startsWith("--lang="))).toBe(false);
+    expect(args.some(a => a.startsWith("--fingerprint-locale="))).toBe(false);
   });
 });
 
@@ -147,14 +151,17 @@ describe("buildArgs deduplication", () => {
     expect(tzArgs[0]).toBe("--fingerprint-timezone=America/New_York");
   });
 
-  it("locale param overrides user --lang arg", () => {
+  it("locale param overrides user --lang and --fingerprint-locale args", () => {
     const args = _buildArgsForTest({
-      args: ["--lang=de-DE"],
+      args: ["--lang=de-DE", "--fingerprint-locale=de-DE"],
       locale: "en-US",
     });
     const langArgs = args.filter(a => a.startsWith("--lang="));
     expect(langArgs).toHaveLength(1);
     expect(langArgs[0]).toBe("--lang=en-US");
+    const localeArgs = args.filter(a => a.startsWith("--fingerprint-locale="));
+    expect(localeArgs).toHaveLength(1);
+    expect(localeArgs[0]).toBe("--fingerprint-locale=en-US");
   });
 
   it("no duplicate flag keys in output", () => {
@@ -175,29 +182,29 @@ describe("buildArgs deduplication", () => {
   });
 });
 
-describe("migrateTimezoneId deprecation", () => {
-  it("migrates timezoneId to timezone", () => {
-    const result = migrateTimezoneId({ timezoneId: "Europe/Paris" });
+describe("resolveTimezone alias", () => {
+  it("resolves timezoneId to timezone", () => {
+    const result = resolveTimezone({ timezoneId: "Europe/Paris" });
     expect(result.timezone).toBe("Europe/Paris");
     expect(result).not.toHaveProperty("timezoneId");
   });
 
   it("preserves explicit timezone over timezoneId", () => {
-    const result = migrateTimezoneId({ timezone: "UTC", timezoneId: "Europe/Paris" });
+    const result = resolveTimezone({ timezone: "UTC", timezoneId: "Europe/Paris" });
     expect(result.timezone).toBe("UTC");
     expect(result).not.toHaveProperty("timezoneId");
   });
 
   it("returns options unchanged when no timezoneId", () => {
     const opts = { timezone: "UTC" };
-    const result = migrateTimezoneId(opts);
+    const result = resolveTimezone(opts);
     expect(result).toBe(opts); // same reference, no copy
     expect(result.timezone).toBe("UTC");
   });
 
   it("returns options unchanged when neither is set", () => {
     const opts = {};
-    const result = migrateTimezoneId(opts);
+    const result = resolveTimezone(opts);
     expect(result).toBe(opts);
   });
 });

js/tests/launch.test.ts

@@ -96,20 +96,20 @@ describe("launchContext (unit)", () => {
     expect(ctxArgs.userAgent).toBe("Custom/1.0");
   });
 
-  it("passes timezone to context timezoneId, not to launch", async () => {
+  it("passes timezone via binary flag, not CDP context", async () => {
     const { launchContext } = await import("../src/playwright.js");
     await launchContext({ timezone: "America/New_York" });
 
-    // launch() called with timezone: undefined (skipped for binary flag)
+    // launch() called with --fingerprint-timezone binary flag
     const launchArgs = mockChromium.launch.mock.calls[0][0];
     const hasTimezoneFlag = launchArgs.args.some((a: string) =>
-      a.startsWith("--fingerprint-timezone=")
+      a.startsWith("--fingerprint-timezone=America/New_York")
     );
-    expect(hasTimezoneFlag).toBe(false);
+    expect(hasTimezoneFlag).toBe(true);
 
-    // newContext() gets timezoneId
+    // NOT in newContext() — no CDP emulation
     const ctxArgs = mockBrowser.newContext.mock.calls[0][0];
-    expect(ctxArgs.timezoneId).toBe("America/New_York");
+    expect(ctxArgs.timezoneId).toBeUndefined();
   });
 
   it("forwards colorScheme to newContext", async () => {
@@ -165,7 +165,7 @@ describe("launchPersistentContext (unit)", () => {
     expect(args.viewport).toEqual(DEFAULT_VIEWPORT);
   });
 
-  it("passes timezone and locale to context", async () => {
+  it("passes timezone and locale via binary args, not CDP context", async () => {
     const { launchPersistentContext } = await import("../src/playwright.js");
     await launchPersistentContext({
       userDataDir: "/tmp/profile",
@@ -174,11 +174,12 @@ describe("launchPersistentContext (unit)", () => {
     });
 
     const args = mockChromium.launchPersistentContext.mock.calls[0][1];
-    expect(args.timezoneId).toBe("Asia/Tokyo");
-    expect(args.locale).toBe("ja-JP");
-    // Also in binary args
+    // Binary args (native, undetectable)
     expect(args.args).toContain("--fingerprint-timezone=Asia/Tokyo");
     expect(args.args).toContain("--lang=ja-JP");
+    // NOT in context kwargs (would trigger detectable CDP emulation)
+    expect(args.timezoneId).toBeUndefined();
+    expect(args.locale).toBeUndefined();
   });
 
   it("forwards proxy string", async () => {

tests/test_build_args.py

@@ -1,8 +1,6 @@
-"""Unit tests for _build_args timezone/locale injection and deprecation compat."""
+"""Unit tests for _build_args timezone/locale injection and timezone alias."""
 
-import warnings
-
-from cloakbrowser.browser import _build_args, _migrate_timezone_id
+from cloakbrowser.browser import _build_args, _resolve_timezone
 
 
 def test_timezone_injected():
@@ -12,9 +10,10 @@ def test_timezone_injected():
 
 
 def test_locale_injected():
-    """--lang flag should appear when locale is set."""
+    """--lang and --fingerprint-locale flags should appear when locale is set."""
     args = _build_args(stealth_args=True, extra_args=None, locale="en-US")
     assert "--lang=en-US" in args
+    assert "--fingerprint-locale=en-US" in args
 
 
 def test_both_injected():
@@ -22,6 +21,7 @@ def test_both_injected():
     args = _build_args(stealth_args=True, extra_args=None, timezone="Europe/Berlin", locale="de-DE")
     assert "--fingerprint-timezone=Europe/Berlin" in args
     assert "--lang=de-DE" in args
+    assert "--fingerprint-locale=de-DE" in args
 
 
 def test_timezone_independent_of_stealth_args():
@@ -29,15 +29,17 @@ def test_timezone_independent_of_stealth_args():
     args = _build_args(stealth_args=False, extra_args=None, timezone="America/New_York", locale="en-US")
     assert "--fingerprint-timezone=America/New_York" in args
     assert "--lang=en-US" in args
+    assert "--fingerprint-locale=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."""
+    """No timezone/lang/fingerprint-locale flags when params are None."""
     args = _build_args(stealth_args=True, extra_args=None)
     assert not any(a.startswith("--fingerprint-timezone=") for a in args)
     assert not any(a.startswith("--lang=") for a in args)
+    assert not any(a.startswith("--fingerprint-locale=") for a in args)
 
 
 def test_extra_args_preserved():
@@ -46,52 +48,41 @@ def test_extra_args_preserved():
     assert "--disable-gpu" in args
     assert "--fingerprint-timezone=Asia/Tokyo" in args
     assert "--lang=ja-JP" in args
+    assert "--fingerprint-locale=ja-JP" in args
 
 
-# --- _migrate_timezone_id deprecation compat ---
+# --- _resolve_timezone alias ---
 
 
-def test_migrate_old_param_only():
+def test_resolve_timezone_id_alias():
     """timezone_id in kwargs should be promoted to timezone."""
     kwargs = {"timezone_id": "Europe/Paris"}
-    with warnings.catch_warnings(record=True) as w:
-        warnings.simplefilter("always")
-        result = _migrate_timezone_id(None, kwargs)
+    result = _resolve_timezone(None, kwargs)
     assert result == "Europe/Paris"
     assert "timezone_id" not in kwargs
-    assert len(w) == 1 and issubclass(w[0].category, FutureWarning)
 
 
-def test_migrate_new_param_wins():
+def test_resolve_timezone_wins_over_alias():
     """Explicit timezone takes precedence; timezone_id is still popped."""
     kwargs = {"timezone_id": "Europe/Paris"}
-    with warnings.catch_warnings(record=True) as w:
-        warnings.simplefilter("always")
-        result = _migrate_timezone_id("UTC", kwargs)
+    result = _resolve_timezone("UTC", kwargs)
     assert result == "UTC"
     assert "timezone_id" not in kwargs
-    assert len(w) == 1
 
 
-def test_migrate_no_old_param():
-    """No warning when timezone_id is absent."""
+def test_resolve_no_alias():
+    """No-op when timezone_id is absent."""
     kwargs = {"other": "value"}
-    with warnings.catch_warnings(record=True) as w:
-        warnings.simplefilter("always")
-        result = _migrate_timezone_id("UTC", kwargs)
+    result = _resolve_timezone("UTC", kwargs)
     assert result == "UTC"
     assert "other" in kwargs
-    assert len(w) == 0
 
 
-def test_migrate_both_none():
-    """Neither param set — returns None, no warning."""
+def test_resolve_both_none():
+    """Neither param set — returns None."""
     kwargs = {}
-    with warnings.catch_warnings(record=True) as w:
-        warnings.simplefilter("always")
-        result = _migrate_timezone_id(None, kwargs)
+    result = _resolve_timezone(None, kwargs)
     assert result is None
-    assert len(w) == 0
 
 
 # --- Deduplication tests ---
@@ -126,15 +117,18 @@ def test_timezone_param_overrides_user_arg():
 
 
 def test_locale_param_overrides_user_arg():
-    """Dedicated locale param should override user --lang arg."""
+    """Dedicated locale param should override user --lang and --fingerprint-locale args."""
     args = _build_args(
         stealth_args=True,
-        extra_args=["--lang=de-DE"],
+        extra_args=["--lang=de-DE", "--fingerprint-locale=de-DE"],
         locale="en-US",
     )
     lang_args = [a for a in args if a.startswith("--lang=")]
     assert len(lang_args) == 1
     assert lang_args[0] == "--lang=en-US"
+    locale_args = [a for a in args if a.startswith("--fingerprint-locale=")]
+    assert len(locale_args) == 1
+    assert locale_args[0] == "--fingerprint-locale=en-US"
 
 
 def test_no_duplicate_flags():

tests/test_launch_context.py

@@ -1,6 +1,5 @@
 """Unit tests for launch_context() — context kwargs, viewport defaults, close cleanup."""
 
-import warnings
 from unittest.mock import MagicMock, call, patch
 
 import pytest
@@ -66,7 +65,7 @@ def test_user_agent(mock_launch, _mock_bin):
 @patch("cloakbrowser.browser.ensure_binary", return_value="/fake/chrome")
 @patch("cloakbrowser.browser.launch")
 def test_locale_forwarded(mock_launch, _mock_bin):
-    """locale flows to both launch() binary args AND new_context()."""
+    """locale flows to launch() for --lang binary flag, NOT to new_context() CDP."""
     browser, context = _make_mock_browser()
     mock_launch.return_value = browser
 
@@ -75,18 +74,18 @@ def test_locale_forwarded(mock_launch, _mock_bin):
 
     # Locale in launch() call (for --lang binary flag)
     assert mock_launch.call_args[1]["locale"] == "de-DE"
-    # Locale in new_context() call
+    # NOT in new_context() — would trigger detectable CDP emulation
     ctx_kwargs = browser.new_context.call_args
-    assert ctx_kwargs[1]["locale"] == "de-DE"
+    assert "locale" not in ctx_kwargs[1]
 
 
 @patch("cloakbrowser.browser.ensure_binary", return_value="/fake/chrome")
 @patch("cloakbrowser.browser.launch")
-def test_timezone_via_context_not_binary(mock_launch, _mock_bin):
-    """timezone passed to new_context(timezone_id=...) but NOT to launch(timezone=...).
+def test_timezone_via_binary_not_cdp(mock_launch, _mock_bin):
+    """timezone passed to launch() for binary flag, NOT to new_context() CDP.
 
-    This is intentional: the --fingerprint-timezone binary flag only applies to the
-    default context and would conflict with Playwright's timezone_id on new contexts.
+    --fingerprint-timezone is process-wide (reads CommandLine in renderer),
+    so it applies to ALL contexts, not just the default one.
     """
     browser, context = _make_mock_browser()
     mock_launch.return_value = browser
@@ -94,11 +93,11 @@ def test_timezone_via_context_not_binary(mock_launch, _mock_bin):
     from cloakbrowser.browser import launch_context
     launch_context(timezone="America/New_York")
 
-    # timezone=None in launch() — binary flag skipped
-    assert mock_launch.call_args[1]["timezone"] is None
-    # timezone_id in new_context()
+    # timezone in launch() — binary flag set
+    assert mock_launch.call_args[1]["timezone"] == "America/New_York"
+    # NOT in new_context() — no CDP emulation
     ctx_kwargs = browser.new_context.call_args
-    assert ctx_kwargs[1]["timezone_id"] == "America/New_York"
+    assert "timezone_id" not in ctx_kwargs[1]
 
 
 @patch("cloakbrowser.browser.ensure_binary", return_value="/fake/chrome")
@@ -119,40 +118,37 @@ def test_color_scheme(mock_launch, _mock_bin):
 @patch("cloakbrowser.browser.ensure_binary", return_value="/fake/chrome")
 @patch("cloakbrowser.browser.launch")
 def test_geoip_resolution(mock_launch, _mock_bin, _mock_geoip):
-    """geoip fills timezone+locale, both flow to correct places."""
+    """geoip fills timezone+locale, both flow to binary args only."""
     browser, context = _make_mock_browser()
     mock_launch.return_value = browser
 
     from cloakbrowser.browser import launch_context
     launch_context(proxy="http://proxy:8080", geoip=True)
 
-    # Locale goes to launch() for binary flag
+    # Both go to launch() for binary flags
     assert mock_launch.call_args[1]["locale"] == "de-DE"
-    # Timezone goes to context, not binary
-    assert mock_launch.call_args[1]["timezone"] is None
+    assert mock_launch.call_args[1]["timezone"] == "Europe/Berlin"
+    # Neither in context — no CDP emulation
     ctx_kwargs = browser.new_context.call_args
-    assert ctx_kwargs[1]["timezone_id"] == "Europe/Berlin"
-    assert ctx_kwargs[1]["locale"] == "de-DE"
+    assert "timezone_id" not in ctx_kwargs[1]
+    assert "locale" not in ctx_kwargs[1]
 
 
 @patch("cloakbrowser.browser.ensure_binary", return_value="/fake/chrome")
 @patch("cloakbrowser.browser.launch")
-def test_timezone_id_deprecation(mock_launch, _mock_bin):
-    """timezone_id kwarg triggers FutureWarning, value migrated to timezone."""
+def test_timezone_id_alias(mock_launch, _mock_bin):
+    """timezone_id kwarg accepted as alias for timezone."""
     browser, context = _make_mock_browser()
     mock_launch.return_value = browser
 
     from cloakbrowser.browser import launch_context
-    with warnings.catch_warnings(record=True) as w:
-        warnings.simplefilter("always")
-        launch_context(timezone_id="Europe/Paris")
+    launch_context(timezone_id="Europe/Paris")
 
-    assert len(w) == 1
-    assert issubclass(w[0].category, FutureWarning)
-    assert "timezone_id" in str(w[0].message)
-    # Migrated value flows to context
+    # Resolved value flows to launch() for binary flag
+    assert mock_launch.call_args[1]["timezone"] == "Europe/Paris"
+    # NOT in context — no CDP emulation
     ctx_kwargs = browser.new_context.call_args
-    assert ctx_kwargs[1]["timezone_id"] == "Europe/Paris"
+    assert "timezone_id" not in ctx_kwargs[1]
 
 
 @patch("cloakbrowser.browser.ensure_binary", return_value="/fake/chrome")

tests/test_persistent_context.py

@@ -3,7 +3,6 @@
 All tests mock playwright to avoid needing a binary.
 """
 
-import warnings
 from unittest.mock import AsyncMock, MagicMock, patch
 
 import pytest
@@ -87,7 +86,7 @@ def test_persistent_context_user_agent(_mock_geoip, _mock_bin):
 
 @patch("cloakbrowser.browser.ensure_binary", return_value="/fake/chrome")
 def test_persistent_context_locale_and_timezone(_mock_bin):
-    """Both timezone and locale flow to context kwargs and binary args."""
+    """Timezone and locale flow to binary args only, NOT to CDP context kwargs."""
     pw_cm, pw, context = _make_mock_pw_and_context()
 
     with patch("playwright.sync_api.sync_playwright", return_value=pw_cm):
@@ -95,12 +94,12 @@ def test_persistent_context_locale_and_timezone(_mock_bin):
         launch_persistent_context("/tmp/profile", timezone="Asia/Tokyo", locale="ja-JP")
 
     call_kwargs = pw.chromium.launch_persistent_context.call_args[1]
-    # Context kwargs
-    assert call_kwargs["timezone_id"] == "Asia/Tokyo"
-    assert call_kwargs["locale"] == "ja-JP"
-    # Binary args
+    # Binary args (native, undetectable)
     assert "--fingerprint-timezone=Asia/Tokyo" in call_kwargs["args"]
     assert "--lang=ja-JP" in call_kwargs["args"]
+    # NOT in context kwargs (would trigger detectable CDP emulation)
+    assert "timezone_id" not in call_kwargs
+    assert "locale" not in call_kwargs
 
 
 @patch("cloakbrowser.browser.ensure_binary", return_value="/fake/chrome")
@@ -120,7 +119,7 @@ def test_persistent_context_color_scheme(_mock_geoip, _mock_bin):
 @patch("cloakbrowser.browser._maybe_resolve_geoip", return_value=("Europe/Berlin", "de-DE"))
 @patch("cloakbrowser.browser.ensure_binary", return_value="/fake/chrome")
 def test_persistent_context_geoip(_mock_bin, _mock_geoip):
-    """geoip fills missing tz/locale."""
+    """geoip fills missing tz/locale — flows to binary args, not CDP context."""
     pw_cm, pw, context = _make_mock_pw_and_context()
 
     with patch("playwright.sync_api.sync_playwright", return_value=pw_cm):
@@ -128,25 +127,26 @@ def test_persistent_context_geoip(_mock_bin, _mock_geoip):
         launch_persistent_context("/tmp/profile", proxy="http://proxy:8080", geoip=True)
 
     call_kwargs = pw.chromium.launch_persistent_context.call_args[1]
-    assert call_kwargs["timezone_id"] == "Europe/Berlin"
-    assert call_kwargs["locale"] == "de-DE"
+    # Binary args
+    assert "--fingerprint-timezone=Europe/Berlin" in call_kwargs["args"]
+    assert "--lang=de-DE" in call_kwargs["args"]
+    # NOT in context kwargs
+    assert "timezone_id" not in call_kwargs
+    assert "locale" not in call_kwargs
 
 
 @patch("cloakbrowser.browser.ensure_binary", return_value="/fake/chrome")
-def test_persistent_context_timezone_id_deprecation(_mock_bin):
-    """Old timezone_id kwarg migrated with warning."""
+def test_persistent_context_timezone_id_alias(_mock_bin):
+    """timezone_id kwarg accepted as alias for timezone."""
     pw_cm, pw, context = _make_mock_pw_and_context()
 
     with patch("playwright.sync_api.sync_playwright", return_value=pw_cm):
         from cloakbrowser.browser import launch_persistent_context
-        with warnings.catch_warnings(record=True) as w:
-            warnings.simplefilter("always")
-            launch_persistent_context("/tmp/profile", timezone_id="Europe/Paris")
+        launch_persistent_context("/tmp/profile", timezone_id="Europe/Paris")
 
-    assert len(w) == 1
-    assert issubclass(w[0].category, FutureWarning)
     call_kwargs = pw.chromium.launch_persistent_context.call_args[1]
-    assert call_kwargs["timezone_id"] == "Europe/Paris"
+    assert "--fingerprint-timezone=Europe/Paris" in call_kwargs["args"]
+    assert "timezone_id" not in call_kwargs
 
 
 @patch("cloakbrowser.browser.ensure_binary", return_value="/fake/chrome")
@@ -246,17 +246,14 @@ async def test_persistent_context_async_close_stops_pw(_mock_geoip, _mock_bin):
 
 @pytest.mark.asyncio
 @patch("cloakbrowser.browser.ensure_binary", return_value="/fake/chrome")
-async def test_persistent_context_async_timezone_id_deprecation(_mock_bin):
-    """Deprecated timezone_id kwarg migrated with warning in async path."""
+async def test_persistent_context_async_timezone_id_alias(_mock_bin):
+    """timezone_id kwarg accepted as alias in async path."""
     pw_cm, pw, context = _make_mock_async_pw_and_context()
 
     with patch("playwright.async_api.async_playwright", return_value=pw_cm):
         from cloakbrowser.browser import launch_persistent_context_async
-        with warnings.catch_warnings(record=True) as w:
-            warnings.simplefilter("always")
-            await launch_persistent_context_async("/tmp/profile", timezone_id="Europe/Paris")
+        await launch_persistent_context_async("/tmp/profile", timezone_id="Europe/Paris")
 
-    assert len(w) == 1
-    assert issubclass(w[0].category, FutureWarning)
     call_kwargs = pw.chromium.launch_persistent_context.call_args[1]
-    assert call_kwargs["timezone_id"] == "Europe/Paris"
+    assert "--fingerprint-timezone=Europe/Paris" in call_kwargs["args"]
+    assert "timezone_id" not in call_kwargs