fix(python): key the browser floor on Playwright instead of a flat minimum

The incompatibility is two-dimensional -- it needs both a Playwright >= 1.61
and a browser < beta.30 -- but MIN_VERSION only knows about the browser. To
stay safe a flat floor has to assume the worst Playwright, which means:

  * every 0.5.6 user re-downloads the browser, including the majority on
    <1.61 who are in no danger;
  * installs pinned to an older build lose the pin, and prerelease/alpha users
    are moved off their channel, since every alpha sorts below beta.30;
  * the library cannot run at all until the matching browser release is
    published, making the PyPI-after-release ordering load-bearing.

Key it on the resolved Playwright instead. Measured: 1.60 works on beta.29 and
beta.30; 1.61 and 1.62 fail on beta.29 and pass on beta.30.

  playwright <1.61  -> floor alpha.1  -> every install kept
  playwright >=1.61 -> floor beta.30  -> below-beta.30 installs upgraded
  version unreadable -> floor alpha.1 -> kept; a spurious forced re-download is
                                        worse than leaving a working install

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

pythonlib/camoufox/__version__.py

@@ -8,9 +8,27 @@ class CONSTRAINTS:
     The minimum and maximum supported versions of the Camoufox browser.
     """
 
-    MIN_VERSION = 'beta.30'
+    MIN_VERSION = 'alpha.1'
     MAX_VERSION = '1'
 
+    # The browser floor is conditional on the resolved Playwright, not fixed.
+    #
+    # Each entry is (playwright_version, required_browser_build): from that
+    # Playwright on, the browser must be at least that build. 1.61 began
+    # sending viewport isMobile/screenSize in Browser.setDefaultViewport and
+    # Page.setViewportSize; beta.30 is the first build whose Protocol.js schema
+    # accepts them. Below that pairing every new_context() dies with
+    # "Protocol error (Browser.setDefaultViewport)". Measured: 1.60 works on
+    # beta.29 and beta.30; 1.61 and 1.62 fail on beta.29 and pass on beta.30.
+    #
+    # A flat MIN_VERSION cannot express this. It only knows about the browser,
+    # so to stay safe it has to assume the worst Playwright and force *every*
+    # user to re-download -- including the majority on <1.61, who are in no
+    # danger -- and it leaves the library unusable until the matching browser
+    # release is published. Keyed on Playwright, only the users who would
+    # actually break get moved.
+    PLAYWRIGHT_BROWSER_FLOORS = (((1, 61), 'beta.30'),)
+
     @staticmethod
     def as_range() -> str:
         """

pythonlib/camoufox/pkgman.py

@@ -367,7 +367,7 @@ class Version:
         return self.sorted_rel < other.sorted_rel
 
     def is_supported(self) -> bool:
-        return VERSION_MIN <= self < VERSION_MAX
+        return effective_version_min() <= self < VERSION_MAX
 
     @staticmethod
     def from_path(path: Optional[Path] = None) -> 'Version':
@@ -406,6 +406,34 @@ class Version:
 VERSION_MIN, VERSION_MAX = Version.build_minmax()
 
 
+def _resolved_playwright_version() -> Optional[Tuple[int, ...]]:
+    """The installed Playwright version, or None if it cannot be determined."""
+    from importlib.metadata import version
+
+    try:
+        return _parse_semver(version('playwright'))
+    except Exception:
+        return None
+
+
+def effective_version_min() -> 'Version':
+    """The lowest browser build this install can actually talk to.
+
+    VERSION_MIN, raised by whatever the resolved Playwright requires. When the
+    Playwright version cannot be read we fall back to VERSION_MIN rather than
+    assuming the worst: a spurious forced re-download is worse than leaving a
+    working install alone, and pyproject caps Playwright anyway.
+    """
+    floor = VERSION_MIN
+    playwright_version = _resolved_playwright_version()
+    if playwright_version is None:
+        return floor
+    for required_playwright, build in CONSTRAINTS.PLAYWRIGHT_BROWSER_FLOORS:
+        if playwright_version >= required_playwright and floor < Version(build=build):
+            floor = Version(build=build)
+    return floor
+
+
 class GitHubDownloader:
     """
     Manages fetching GitHub releases with fallback repos

pythonlib/tests/test_version_floor_upgrade.py

@@ -119,3 +119,49 @@ def test_unsatisfiable_floor_reports_instead_of_recursing(tmp_path, monkeypatch)
         pkgman.camoufox_path()
 
     assert attempts == [True], "should fetch once, not spin"
+
+
+class TestConditionalFloor:
+    """The browser floor is keyed on the resolved Playwright, not fixed.
+
+    A flat floor can only speak about the browser, so to be safe it has to
+    assume the worst Playwright and re-download for everyone -- and it makes
+    the library unusable until the matching browser release exists. Keyed on
+    Playwright, only the pairing that actually breaks gets moved.
+    """
+
+    @staticmethod
+    def _with_playwright(monkeypatch, version):
+        parsed = pkgman._parse_semver(version) if version else None
+        monkeypatch.setattr(pkgman, "_resolved_playwright_version", lambda: parsed)
+
+    @pytest.mark.parametrize("version", ["1.53.0", "1.60.0"])
+    def test_old_playwright_leaves_older_builds_alone(self, monkeypatch, version):
+        """<1.61 never sends the fields beta.29 rejects, so nothing must move."""
+        self._with_playwright(monkeypatch, version)
+        assert pkgman.effective_version_min() == pkgman.Version(build="alpha.1")
+
+    @pytest.mark.parametrize("version", ["1.61.0", "1.62.0"])
+    def test_new_playwright_raises_the_floor(self, monkeypatch, version):
+        self._with_playwright(monkeypatch, version)
+        assert pkgman.effective_version_min() == pkgman.Version(build="beta.30")
+
+    def test_unreadable_playwright_falls_back_permissive(self, monkeypatch):
+        """A spurious forced re-download is worse than leaving a working install."""
+        self._with_playwright(monkeypatch, None)
+        assert pkgman.effective_version_min() == pkgman.Version(build="alpha.1")
+
+    def test_old_playwright_keeps_a_below_floor_install(self, tmp_path, monkeypatch):
+        _install(tmp_path, monkeypatch, "versioned", build="beta.29", floor="alpha.1")
+        self._with_playwright(monkeypatch, "1.60.0")
+
+        resolved = pkgman.camoufox_path(download_if_missing=False)
+
+        assert resolved.name == "152.0.4-beta.29"
+
+    def test_new_playwright_moves_a_below_floor_install(self, tmp_path, monkeypatch):
+        _install(tmp_path, monkeypatch, "versioned", build="beta.29", floor="alpha.1")
+        self._with_playwright(monkeypatch, "1.62.0")
+
+        with pytest.raises(UnsupportedVersion):
+            pkgman.camoufox_path(download_if_missing=False)