fix(wrapper): track real window geometry on headed launches

Headed launches applied a fixed emulated viewport on top of the real
browser window, yielding outerWidth < innerWidth (an impossible window).
Default headed new_page()/new_context() to no_viewport so the page tracks
the real window; headless keeps a deterministic viewport. Covers Python
launch/launch_context/launch_persistent_context (+async) and the JS
Playwright/Puppeteer wrappers. Explicit viewport still honored.

tests/test_launch_context.py

@@ -33,6 +33,82 @@ def test_default_viewport(mock_launch, _mock_bin):
     assert ctx_kwargs[1]["viewport"] == DEFAULT_VIEWPORT
 
 
+@patch("cloakbrowser.browser.ensure_binary", return_value="/fake/chrome")
+@patch("cloakbrowser.browser.launch")
+def test_headed_no_viewport(mock_launch, _mock_bin):
+    """Headed (headless=False): no emulated viewport — no_viewport=True so the page
+    tracks the real window (CDP viewport emulation would force outerWidth < innerWidth)."""
+    browser, context = _make_mock_browser()
+    mock_launch.return_value = browser
+
+    from cloakbrowser.browser import launch_context
+    launch_context(headless=False)
+
+    ctx_kwargs = browser.new_context.call_args[1]
+    assert ctx_kwargs.get("no_viewport") is True
+    assert "viewport" not in ctx_kwargs
+
+
+def test_default_no_viewport_helper():
+    """_default_no_viewport defaults new_page()/new_context() to no_viewport=True,
+    but never overrides an explicit viewport (Playwright rejects passing both)."""
+    from cloakbrowser.browser import _default_no_viewport
+
+    browser = MagicMock()
+    orig_new_page = browser.new_page
+    orig_new_context = browser.new_context
+    _default_no_viewport(browser)
+
+    browser.new_page()
+    orig_new_page.assert_called_once_with(no_viewport=True)
+    browser.new_context()
+    orig_new_context.assert_called_once_with(no_viewport=True)
+
+    # Explicit viewport respected — no_viewport NOT injected.
+    orig_new_page.reset_mock()
+    browser.new_page(viewport={"width": 800, "height": 600})
+    orig_new_page.assert_called_once_with(viewport={"width": 800, "height": 600})
+
+
+@pytest.mark.asyncio
+async def test_default_no_viewport_helper_async():
+    """_default_no_viewport_async mirrors the sync helper for async new_page/new_context."""
+    from cloakbrowser.browser import _default_no_viewport_async
+
+    browser = MagicMock()
+    browser.new_page = AsyncMock()
+    browser.new_context = AsyncMock()
+    orig_new_page = browser.new_page
+    orig_new_context = browser.new_context
+    _default_no_viewport_async(browser)
+
+    await browser.new_page()
+    orig_new_page.assert_awaited_once_with(no_viewport=True)
+    await browser.new_context()
+    orig_new_context.assert_awaited_once_with(no_viewport=True)
+
+    # Explicit viewport respected — no_viewport NOT injected.
+    orig_new_page.reset_mock()
+    await browser.new_page(viewport={"width": 800, "height": 600})
+    orig_new_page.assert_awaited_once_with(viewport={"width": 800, "height": 600})
+
+
+@patch("cloakbrowser.browser.ensure_binary", return_value="/fake/chrome")
+@patch("cloakbrowser.browser.launch")
+def test_conflicting_viewport_kwargs_deduped(mock_launch, _mock_bin):
+    """If a caller forces no_viewport via **kwargs alongside viewport=, only one
+    reaches Playwright (which rejects both). The explicit kwargs value wins."""
+    browser, context = _make_mock_browser()
+    mock_launch.return_value = browser
+
+    from cloakbrowser.browser import launch_context
+    launch_context(viewport={"width": 1280, "height": 800}, no_viewport=True)
+
+    ctx_kwargs = browser.new_context.call_args[1]
+    assert ctx_kwargs.get("no_viewport") is True
+    assert "viewport" not in ctx_kwargs
+
+
 @patch("cloakbrowser.browser.ensure_binary", return_value="/fake/chrome")
 @patch("cloakbrowser.browser.launch")
 def test_custom_viewport(mock_launch, _mock_bin):

tests/test_persistent_context.py

@@ -55,6 +55,22 @@ def test_persistent_context_default_viewport(_mock_geoip, _mock_bin):
     assert call_kwargs["viewport"] == DEFAULT_VIEWPORT
 
 
+@patch("cloakbrowser.browser.ensure_binary", return_value="/fake/chrome")
+@patch("cloakbrowser.browser.maybe_resolve_geoip", return_value=(None, None, None))
+def test_persistent_context_headed_no_viewport(_mock_geoip, _mock_bin):
+    """Headed (headless=False): no_viewport=True instead of DEFAULT_VIEWPORT so the
+    page tracks the real window (avoids the outerWidth < innerWidth tell)."""
+    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
+        launch_persistent_context("/tmp/profile", headless=False)
+
+    call_kwargs = pw.chromium.launch_persistent_context.call_args[1]
+    assert call_kwargs.get("no_viewport") is True
+    assert "viewport" not in call_kwargs
+
+
 @patch("cloakbrowser.browser.ensure_binary", return_value="/fake/chrome")
 @patch("cloakbrowser.browser.maybe_resolve_geoip", return_value=(None, None, None))
 def test_persistent_context_custom_viewport(_mock_geoip, _mock_bin):