diff --git a/cibuildwheel/__main__.py b/cibuildwheel/__main__.py
index e16adca9c..eded443de 100644
--- a/cibuildwheel/__main__.py
+++ b/cibuildwheel/__main__.py
@@ -9,25 +9,21 @@
 import time
 import traceback
 import typing
-from collections.abc import Generator, Iterable, Sequence, Set
+from collections.abc import Generator, Iterable, Sequence
 from pathlib import Path
 from tempfile import mkdtemp
-from typing import Any, Protocol, TextIO, assert_never
+from typing import Any, Literal, TextIO
 
 import cibuildwheel
-import cibuildwheel.ios
-import cibuildwheel.linux
-import cibuildwheel.macos
-import cibuildwheel.pyodide
 import cibuildwheel.util
-import cibuildwheel.windows
 from cibuildwheel import errors
 from cibuildwheel.architecture import Architecture, allowed_architectures_check
 from cibuildwheel.ci import CIProvider, detect_ci_provider, fix_ansi_codes_for_github_actions
 from cibuildwheel.logger import log
 from cibuildwheel.options import CommandLineArguments, Options, compute_options
-from cibuildwheel.selector import BuildSelector, EnableGroup
-from cibuildwheel.typing import PLATFORMS, GenericPythonConfiguration, PlatformName
+from cibuildwheel.platforms import ALL_PLATFORM_MODULES, get_build_identifiers
+from cibuildwheel.selector import BuildSelector, EnableGroup, selector_matches
+from cibuildwheel.typing import PLATFORMS, PlatformName
 from cibuildwheel.util.file import CIBW_CACHE_PATH
 from cibuildwheel.util.helpers import strtobool
 
@@ -286,30 +282,6 @@ def _compute_platform(args: CommandLineArguments) -> PlatformName:
     return _compute_platform_auto()
 
 
-class PlatformModule(Protocol):
-    # note that as per PEP544, the self argument is ignored when the protocol
-    # is applied to a module
-    def get_python_configurations(
-        self, build_selector: BuildSelector, architectures: Set[Architecture]
-    ) -> Sequence[GenericPythonConfiguration]: ...
-
-    def build(self, options: Options, tmp_path: Path) -> None: ...
-
-
-def get_platform_module(platform: PlatformName) -> PlatformModule:
-    if platform == "linux":
-        return cibuildwheel.linux
-    if platform == "windows":
-        return cibuildwheel.windows
-    if platform == "macos":
-        return cibuildwheel.macos
-    if platform == "pyodide":
-        return cibuildwheel.pyodide
-    if platform == "ios":
-        return cibuildwheel.ios
-    assert_never(platform)
-
-
 @contextlib.contextmanager
 def print_new_wheels(msg: str, output_dir: Path) -> Generator[None, None, None]:
     """
@@ -362,7 +334,7 @@ def build_in_directory(args: CommandLineArguments) -> None:
         msg = f"Could not find any of {{{names}}} at root of package"
         raise errors.ConfigurationError(msg)
 
-    platform_module = get_platform_module(platform)
+    platform_module = ALL_PLATFORM_MODULES[platform]
     identifiers = get_build_identifiers(
         platform_module=platform_module,
         build_selector=options.globals.build_selector,
@@ -448,15 +420,6 @@ def print_preamble(platform: str, options: Options, identifiers: Sequence[str])
     print("Here we go!\n")
 
 
-def get_build_identifiers(
-    platform_module: PlatformModule,
-    build_selector: BuildSelector,
-    architectures: Set[Architecture],
-) -> list[str]:
-    python_configurations = platform_module.get_python_configurations(build_selector, architectures)
-    return [config.identifier for config in python_configurations]
-
-
 def detect_warnings(*, options: Options, identifiers: Iterable[str]) -> list[str]:
     warnings = []
 
@@ -482,6 +445,75 @@ def detect_warnings(*, options: Options, identifiers: Iterable[str]) -> list[str
             )
             raise errors.ConfigurationError(msg)
 
+    build_selector = options.globals.build_selector
+    test_selector = options.globals.test_selector
+
+    all_valid_identifiers = [
+        config.identifier
+        for module in ALL_PLATFORM_MODULES.values()
+        for config in module.all_python_configurations()
+    ]
+
+    enabled_selector = BuildSelector(
+        build_config="*", skip_config="", enable=options.globals.build_selector.enable
+    )
+    all_enabled_identifiers = [
+        identifier for identifier in all_valid_identifiers if enabled_selector(identifier)
+    ]
+
+    warnings += check_for_invalid_selectors(
+        selector_name="build",
+        selector_value=build_selector.build_config,
+        all_valid_identifiers=all_valid_identifiers,
+        all_enabled_identifiers=all_enabled_identifiers,
+    )
+    warnings += check_for_invalid_selectors(
+        selector_name="skip",
+        selector_value=build_selector.skip_config,
+        all_valid_identifiers=all_valid_identifiers,
+        all_enabled_identifiers=all_enabled_identifiers,
+    )
+    warnings += check_for_invalid_selectors(
+        selector_name="test_skip",
+        selector_value=test_selector.skip_config,
+        all_valid_identifiers=all_valid_identifiers,
+        all_enabled_identifiers=all_enabled_identifiers,
+    )
+
+    return warnings
+
+
+def check_for_invalid_selectors(
+    *,
+    selector_name: Literal["build", "skip", "test_skip"],
+    selector_value: str,
+    all_valid_identifiers: Sequence[str],
+    all_enabled_identifiers: Sequence[str],
+) -> list[str]:
+    warnings = []
+
+    for selector in selector_value.split():
+        if not any(selector_matches(selector, i) for i in all_enabled_identifiers):
+            msg = f"Invalid {selector_name} selector: {selector!r}. "
+            error_type: type = errors.ConfigurationError
+
+            if any(selector_matches(selector, i) for i in all_valid_identifiers):
+                msg += "This selector matches a group that wasn't enabled. Enable it using the `enable` option or remove this selector. "
+
+            if "p2" in selector or "p35" in selector:
+                msg += f"cibuildwheel 3.x no longer supports Python < 3.8. Please use the 1.x series or update `{selector_name}`. "
+                error_type = errors.DeprecationError
+            if "p36" in selector or "p37" in selector:
+                msg += f"cibuildwheel 3.x no longer supports Python < 3.8. Please use the 2.x series or update `{selector_name}`. "
+                error_type = errors.DeprecationError
+
+            if selector_name == "build":
+                raise error_type(msg)
+
+            msg += "This selector will have no effect. "
+
+            warnings.append(msg)
+
     return warnings
 
 
diff --git a/cibuildwheel/options.py b/cibuildwheel/options.py
index 5ab256232..482035a8e 100644
--- a/cibuildwheel/options.py
+++ b/cibuildwheel/options.py
@@ -863,14 +863,6 @@ def check_for_invalid_configuration(self, identifiers: Iterable[str]) -> None:
                     )
                 )
 
-    def check_for_deprecated_options(self) -> None:
-        build_selector = self.globals.build_selector
-        test_selector = self.globals.test_selector
-
-        deprecated_selectors("CIBW_BUILD", build_selector.build_config, error=True)
-        deprecated_selectors("CIBW_SKIP", build_selector.skip_config)
-        deprecated_selectors("CIBW_TEST_SKIP", test_selector.skip_config)
-
     @functools.cached_property
     def defaults(self) -> Self:
         return self.__class__(
@@ -985,9 +977,7 @@ def compute_options(
     command_line_arguments: CommandLineArguments,
     env: Mapping[str, str],
 ) -> Options:
-    options = Options(platform=platform, command_line_arguments=command_line_arguments, env=env)
-    options.check_for_deprecated_options()
-    return options
+    return Options(platform=platform, command_line_arguments=command_line_arguments, env=env)
 
 
 @functools.cache
@@ -1002,16 +992,3 @@ def _get_pinned_container_images() -> Mapping[str, Mapping[str, str]]:
     all_pinned_images = configparser.ConfigParser()
     all_pinned_images.read(resources.PINNED_DOCKER_IMAGES)
     return all_pinned_images
-
-
-def deprecated_selectors(name: str, selector: str, *, error: bool = False) -> None:
-    if "p2" in selector or "p35" in selector:
-        msg = f"cibuildwheel 3.x no longer supports Python < 3.8. Please use the 1.x series or update {name}"
-        if error:
-            raise errors.DeprecationError(msg)
-        log.warning(msg)
-    if "p36" in selector or "p37" in selector:
-        msg = f"cibuildwheel 3.x no longer supports Python < 3.8. Please use the 2.x series or update {name}"
-        if error:
-            raise errors.DeprecationError(msg)
-        log.warning(msg)
diff --git a/cibuildwheel/platforms/__init__.py b/cibuildwheel/platforms/__init__.py
new file mode 100644
index 000000000..a56fb9036
--- /dev/null
+++ b/cibuildwheel/platforms/__init__.py
@@ -0,0 +1,41 @@
+from __future__ import annotations
+
+from collections.abc import Sequence
+from pathlib import Path
+from typing import Final, Protocol
+
+from cibuildwheel.architecture import Architecture
+from cibuildwheel.options import Options
+from cibuildwheel.platforms import ios, linux, macos, pyodide, windows
+from cibuildwheel.selector import BuildSelector
+from cibuildwheel.typing import GenericPythonConfiguration, PlatformName
+
+
+class PlatformModule(Protocol):
+    # note that as per PEP544, the self argument is ignored when the protocol
+    # is applied to a module
+    def all_python_configurations(self) -> Sequence[GenericPythonConfiguration]: ...
+
+    def get_python_configurations(
+        self, build_selector: BuildSelector, architectures: set[Architecture]
+    ) -> Sequence[GenericPythonConfiguration]: ...
+
+    def build(self, options: Options, tmp_path: Path) -> None: ...
+
+
+ALL_PLATFORM_MODULES: Final[dict[PlatformName, PlatformModule]] = {
+    "linux": linux,
+    "windows": windows,
+    "macos": macos,
+    "pyodide": pyodide,
+    "ios": ios,
+}
+
+
+def get_build_identifiers(
+    platform_module: PlatformModule,
+    build_selector: BuildSelector,
+    architectures: set[Architecture],
+) -> list[str]:
+    python_configurations = platform_module.get_python_configurations(build_selector, architectures)
+    return [config.identifier for config in python_configurations]
diff --git a/cibuildwheel/ios.py b/cibuildwheel/platforms/ios.py
similarity index 97%
rename from cibuildwheel/ios.py
rename to cibuildwheel/platforms/ios.py
index 52411e31a..25dc2a461 100644
--- a/cibuildwheel/ios.py
+++ b/cibuildwheel/platforms/ios.py
@@ -12,34 +12,34 @@
 
 from filelock import FileLock
 
-from . import errors
-from .architecture import Architecture
-from .environment import ParsedEnvironment
-from .frontend import (
+from .. import errors
+from ..architecture import Architecture
+from ..environment import ParsedEnvironment
+from ..frontend import (
     BuildFrontendConfig,
     BuildFrontendName,
     get_build_frontend_extra_flags,
 )
-from .logger import log
-from .macos import install_cpython as install_build_cpython
-from .options import Options
-from .selector import BuildSelector
-from .typing import PathOrStr
-from .util import resources
-from .util.cmd import call, shell
-from .util.file import (
+from ..logger import log
+from ..options import Options
+from ..selector import BuildSelector
+from ..typing import PathOrStr
+from ..util import resources
+from ..util.cmd import call, shell
+from ..util.file import (
     CIBW_CACHE_PATH,
     copy_test_sources,
     download,
     move_file,
 )
-from .util.helpers import prepare_command
-from .util.packaging import (
+from ..util.helpers import prepare_command
+from ..util.packaging import (
     combine_constraints,
     find_compatible_wheel,
     get_pip_version,
 )
-from .venv import virtualenv
+from ..venv import virtualenv
+from .macos import install_cpython as install_build_cpython
 
 
 @dataclass(frozen=True)
@@ -72,10 +72,7 @@ def xcframework_slice(self) -> str:
         return "ios-arm64_x86_64-simulator" if self.is_simulator else "ios-arm64"
 
 
-def get_python_configurations(
-    build_selector: BuildSelector,
-    architectures: Set[Architecture],
-) -> list[PythonConfiguration]:
+def all_python_configurations() -> list[PythonConfiguration]:
     # iOS builds are always cross builds; we need to install a macOS Python as
     # well. Rather than duplicate the location of the URL of macOS installers,
     # load the macos configurations, determine the macOS configuration that
@@ -97,7 +94,7 @@ def build_url(config_dict: dict[str, str]) -> str:
     # Load the platform configuration
     full_python_configs = resources.read_python_configs("ios")
     # Build the configurations, annotating with macOS URL details.
-    python_configurations = [
+    return [
         PythonConfiguration(
             **item,
             build_url=build_url(item),
@@ -105,6 +102,13 @@ def build_url(config_dict: dict[str, str]) -> str:
         for item in full_python_configs
     ]
 
+
+def get_python_configurations(
+    build_selector: BuildSelector,
+    architectures: Set[Architecture],
+) -> list[PythonConfiguration]:
+    python_configurations = all_python_configurations()
+
     # Filter out configs that don't match any of the selected architectures
     python_configurations = [
         c
diff --git a/cibuildwheel/linux.py b/cibuildwheel/platforms/linux.py
similarity index 96%
rename from cibuildwheel/linux.py
rename to cibuildwheel/platforms/linux.py
index 7f0a6e77d..4932298aa 100644
--- a/cibuildwheel/linux.py
+++ b/cibuildwheel/platforms/linux.py
@@ -8,18 +8,18 @@
 from pathlib import Path, PurePath, PurePosixPath
 from typing import assert_never
 
-from . import errors
-from .architecture import Architecture
-from .frontend import BuildFrontendConfig, get_build_frontend_extra_flags
-from .logger import log
-from .oci_container import OCIContainer, OCIContainerEngineConfig, OCIPlatform
-from .options import BuildOptions, Options
-from .selector import BuildSelector
-from .typing import PathOrStr
-from .util import resources
-from .util.file import copy_test_sources
-from .util.helpers import prepare_command, unwrap
-from .util.packaging import find_compatible_wheel
+from .. import errors
+from ..architecture import Architecture
+from ..frontend import BuildFrontendConfig, get_build_frontend_extra_flags
+from ..logger import log
+from ..oci_container import OCIContainer, OCIContainerEngineConfig, OCIPlatform
+from ..options import BuildOptions, Options
+from ..selector import BuildSelector
+from ..typing import PathOrStr
+from ..util import resources
+from ..util.file import copy_test_sources
+from ..util.helpers import prepare_command, unwrap
+from ..util.packaging import find_compatible_wheel
 
 ARCHITECTURE_OCI_PLATFORM_MAP = {
     Architecture.x86_64: OCIPlatform.AMD64,
@@ -50,13 +50,16 @@ class BuildStep:
     container_image: str
 
 
+def all_python_configurations() -> list[PythonConfiguration]:
+    config_dicts = resources.read_python_configs("linux")
+    return [PythonConfiguration(**item) for item in config_dicts]
+
+
 def get_python_configurations(
     build_selector: BuildSelector,
     architectures: Set[Architecture],
 ) -> list[PythonConfiguration]:
-    full_python_configs = resources.read_python_configs("linux")
-
-    python_configurations = [PythonConfiguration(**item) for item in full_python_configs]
+    python_configurations = all_python_configurations()
 
     # return all configurations whose arch is in our `architectures` set,
     # and match the build/skip rules
diff --git a/cibuildwheel/macos.py b/cibuildwheel/platforms/macos.py
similarity index 97%
rename from cibuildwheel/macos.py
rename to cibuildwheel/platforms/macos.py
index b27348d7a..4c75859f0 100644
--- a/cibuildwheel/macos.py
+++ b/cibuildwheel/platforms/macos.py
@@ -15,26 +15,26 @@
 from filelock import FileLock
 from packaging.version import Version
 
-from . import errors
-from .architecture import Architecture
-from .ci import detect_ci_provider
-from .environment import ParsedEnvironment
-from .frontend import BuildFrontendConfig, BuildFrontendName, get_build_frontend_extra_flags
-from .logger import log
-from .options import Options
-from .selector import BuildSelector
-from .typing import PathOrStr
-from .util import resources
-from .util.cmd import call, shell
-from .util.file import (
+from .. import errors
+from ..architecture import Architecture
+from ..ci import detect_ci_provider
+from ..environment import ParsedEnvironment
+from ..frontend import BuildFrontendConfig, BuildFrontendName, get_build_frontend_extra_flags
+from ..logger import log
+from ..options import Options
+from ..selector import BuildSelector
+from ..typing import PathOrStr
+from ..util import resources
+from ..util.cmd import call, shell
+from ..util.file import (
     CIBW_CACHE_PATH,
     copy_test_sources,
     download,
     move_file,
 )
-from .util.helpers import prepare_command, unwrap
-from .util.packaging import combine_constraints, find_compatible_wheel, get_pip_version
-from .venv import find_uv, virtualenv
+from ..util.helpers import prepare_command, unwrap
+from ..util.packaging import combine_constraints, find_compatible_wheel, get_pip_version
+from ..venv import find_uv, virtualenv
 
 
 @functools.cache
@@ -84,12 +84,15 @@ class PythonConfiguration:
     url: str
 
 
+def all_python_configurations() -> list[PythonConfiguration]:
+    config_dicts = resources.read_python_configs("macos")
+    return [PythonConfiguration(**item) for item in config_dicts]
+
+
 def get_python_configurations(
     build_selector: BuildSelector, architectures: Set[Architecture]
 ) -> list[PythonConfiguration]:
-    full_python_configs = resources.read_python_configs("macos")
-
-    python_configurations = [PythonConfiguration(**item) for item in full_python_configs]
+    python_configurations = all_python_configurations()
 
     # filter out configs that don't match any of the selected architectures
     python_configurations = [
diff --git a/cibuildwheel/pyodide.py b/cibuildwheel/platforms/pyodide.py
similarity index 95%
rename from cibuildwheel/pyodide.py
rename to cibuildwheel/platforms/pyodide.py
index 3c56df7e7..ca9edcb20 100644
--- a/cibuildwheel/pyodide.py
+++ b/cibuildwheel/platforms/pyodide.py
@@ -11,17 +11,17 @@
 
 from filelock import FileLock
 
-from . import errors
-from .architecture import Architecture
-from .environment import ParsedEnvironment
-from .frontend import BuildFrontendConfig, get_build_frontend_extra_flags
-from .logger import log
-from .options import Options
-from .selector import BuildSelector
-from .typing import PathOrStr
-from .util import resources
-from .util.cmd import call, shell
-from .util.file import (
+from .. import errors
+from ..architecture import Architecture
+from ..environment import ParsedEnvironment
+from ..frontend import BuildFrontendConfig, get_build_frontend_extra_flags
+from ..logger import log
+from ..options import Options
+from ..selector import BuildSelector
+from ..typing import PathOrStr
+from ..util import resources
+from ..util.cmd import call, shell
+from ..util.file import (
     CIBW_CACHE_PATH,
     copy_test_sources,
     download,
@@ -29,9 +29,9 @@
     extract_zip,
     move_file,
 )
-from .util.helpers import prepare_command
-from .util.packaging import combine_constraints, find_compatible_wheel, get_pip_version
-from .venv import virtualenv
+from ..util.helpers import prepare_command
+from ..util.packaging import combine_constraints, find_compatible_wheel, get_pip_version
+from ..venv import virtualenv
 
 IS_WIN: Final[bool] = sys.platform.startswith("win")
 
@@ -215,15 +215,16 @@ def setup_python(
     return env
 
 
+def all_python_configurations() -> list[PythonConfiguration]:
+    full_python_configs = resources.read_python_configs("pyodide")
+    return [PythonConfiguration(**item) for item in full_python_configs]
+
+
 def get_python_configurations(
     build_selector: BuildSelector,
     architectures: Set[Architecture],  # noqa: ARG001
 ) -> list[PythonConfiguration]:
-    full_python_configs = resources.read_python_configs("pyodide")
-
-    python_configurations = [PythonConfiguration(**item) for item in full_python_configs]
-    python_configurations = [c for c in python_configurations if build_selector(c.identifier)]
-    return python_configurations
+    return [c for c in all_python_configurations() if build_selector(c.identifier)]
 
 
 def build(options: Options, tmp_path: Path) -> None:
diff --git a/cibuildwheel/windows.py b/cibuildwheel/platforms/windows.py
similarity index 96%
rename from cibuildwheel/windows.py
rename to cibuildwheel/platforms/windows.py
index 374b68d71..6d56236a2 100644
--- a/cibuildwheel/windows.py
+++ b/cibuildwheel/platforms/windows.py
@@ -11,20 +11,20 @@
 
 from filelock import FileLock
 
-from . import errors
-from .architecture import Architecture
-from .environment import ParsedEnvironment
-from .frontend import BuildFrontendConfig, BuildFrontendName, get_build_frontend_extra_flags
-from .logger import log
-from .options import Options
-from .selector import BuildSelector
-from .typing import PathOrStr
-from .util import resources
-from .util.cmd import call, shell
-from .util.file import CIBW_CACHE_PATH, copy_test_sources, download, extract_zip, move_file
-from .util.helpers import prepare_command, unwrap
-from .util.packaging import combine_constraints, find_compatible_wheel, get_pip_version
-from .venv import find_uv, virtualenv
+from .. import errors
+from ..architecture import Architecture
+from ..environment import ParsedEnvironment
+from ..frontend import BuildFrontendConfig, BuildFrontendName, get_build_frontend_extra_flags
+from ..logger import log
+from ..options import Options
+from ..selector import BuildSelector
+from ..typing import PathOrStr
+from ..util import resources
+from ..util.cmd import call, shell
+from ..util.file import CIBW_CACHE_PATH, copy_test_sources, download, extract_zip, move_file
+from ..util.helpers import prepare_command, unwrap
+from ..util.packaging import combine_constraints, find_compatible_wheel, get_pip_version
+from ..venv import find_uv, virtualenv
 
 
 def get_nuget_args(
@@ -59,13 +59,16 @@ class PythonConfiguration:
     url: str | None = None
 
 
+def all_python_configurations() -> list[PythonConfiguration]:
+    config_dicts = resources.read_python_configs("windows")
+    return [PythonConfiguration(**item) for item in config_dicts]
+
+
 def get_python_configurations(
     build_selector: BuildSelector,
     architectures: Set[Architecture],
 ) -> list[PythonConfiguration]:
-    full_python_configs = resources.read_python_configs("windows")
-
-    python_configurations = [PythonConfiguration(**item) for item in full_python_configs]
+    python_configurations = all_python_configurations()
 
     map_arch = {"32": Architecture.x86, "64": Architecture.AMD64, "ARM64": Architecture.ARM64}
 
diff --git a/cibuildwheel/selector.py b/cibuildwheel/selector.py
index bd0ce597c..0e9736f53 100644
--- a/cibuildwheel/selector.py
+++ b/cibuildwheel/selector.py
@@ -1,6 +1,6 @@
 import itertools
 from dataclasses import dataclass
-from enum import Enum
+from enum import StrEnum
 from fnmatch import fnmatch
 from typing import Any
 
@@ -24,7 +24,7 @@ def selector_matches(patterns: str, string: str) -> bool:
     return any(fnmatch(string, pat) for pat in expanded_patterns)
 
 
-class EnableGroup(Enum):
+class EnableGroup(StrEnum):
     """
     Groups of build selectors that are not enabled by default.
     """
@@ -33,6 +33,10 @@ class EnableGroup(Enum):
     CPythonPrerelease = "cpython-prerelease"
     PyPy = "pypy"
 
+    @classmethod
+    def all_groups(cls) -> frozenset["EnableGroup"]:
+        return frozenset(cls)
+
 
 @dataclass(frozen=True, kw_only=True)
 class BuildSelector:
diff --git a/test/test_0_basic.py b/test/test_0_basic.py
index 317e876d4..4ef40a2c2 100644
--- a/test/test_0_basic.py
+++ b/test/test_0_basic.py
@@ -83,7 +83,7 @@ def test_allow_empty(tmp_path, add_args, env_allow_empty):
     # without error
     actual_wheels = utils.cibuildwheel_run(
         project_dir,
-        add_env={"CIBW_BUILD": "BUILD_NOTHING_AT_ALL", **env_allow_empty},
+        add_env={"CIBW_SKIP": "*", **env_allow_empty},
         add_args=add_args,
     )
 
diff --git a/test/utils.py b/test/utils.py
index 4548f0a52..4ea3dd4c5 100644
--- a/test/utils.py
+++ b/test/utils.py
@@ -17,6 +17,7 @@
 
 from cibuildwheel.architecture import Architecture
 from cibuildwheel.ci import CIProvider, detect_ci_provider
+from cibuildwheel.selector import EnableGroup
 from cibuildwheel.util.file import CIBW_CACHE_PATH
 
 EMULATED_ARCHS: Final[list[str]] = sorted(
@@ -120,7 +121,7 @@ def cibuildwheel_run(
 
     _update_pip_cache_dir(env)
 
-    env["CIBW_ENABLE"] = "cpython-prerelease cpython-freethreading pypy"
+    env["CIBW_ENABLE"] = " ".join(EnableGroup.all_groups())
 
     if single_python:
         env["CIBW_BUILD"] = "cp{}{}-*".format(*SINGLE_PYTHON_VERSION)
diff --git a/unit_test/get_platform_test.py b/unit_test/get_platform_test.py
index 6f691bf6f..9bd46cd99 100644
--- a/unit_test/get_platform_test.py
+++ b/unit_test/get_platform_test.py
@@ -7,7 +7,7 @@
 
 from cibuildwheel.ci import CIProvider, detect_ci_provider
 from cibuildwheel.errors import FatalError
-from cibuildwheel.windows import PythonConfiguration, setup_setuptools_cross_compile
+from cibuildwheel.platforms.windows import PythonConfiguration, setup_setuptools_cross_compile
 
 # monkeypatching os.name is too flaky. E.g. It works on my machine, but fails in pipeline
 if not sys.platform.startswith("win"):
diff --git a/unit_test/linux_build_steps_test.py b/unit_test/linux_build_steps_test.py
index b493496ef..cd295a5e9 100644
--- a/unit_test/linux_build_steps_test.py
+++ b/unit_test/linux_build_steps_test.py
@@ -4,7 +4,7 @@
 
 import pytest
 
-import cibuildwheel.linux
+import cibuildwheel.platforms.linux
 from cibuildwheel.oci_container import OCIContainerEngineConfig
 from cibuildwheel.options import CommandLineArguments, Options
 
@@ -46,20 +46,22 @@ def test_linux_container_split(tmp_path: Path, monkeypatch: pytest.MonkeyPatch)
     monkeypatch.chdir(tmp_path)
     options = Options("linux", command_line_arguments=args, env={})
 
-    python_configurations = cibuildwheel.linux.get_python_configurations(
+    python_configurations = cibuildwheel.platforms.linux.get_python_configurations(
         options.globals.build_selector, options.globals.architectures
     )
 
-    build_steps = list(cibuildwheel.linux.get_build_steps(options, python_configurations))
+    build_steps = list(cibuildwheel.platforms.linux.get_build_steps(options, python_configurations))
 
     # helper functions to extract test info
-    def identifiers(step: cibuildwheel.linux.BuildStep) -> list[str]:
+    def identifiers(step: cibuildwheel.platforms.linux.BuildStep) -> list[str]:
         return [c.identifier for c in step.platform_configs]
 
-    def before_alls(step: cibuildwheel.linux.BuildStep) -> list[str]:
+    def before_alls(step: cibuildwheel.platforms.linux.BuildStep) -> list[str]:
         return [options.build_options(c.identifier).before_all for c in step.platform_configs]
 
-    def container_engines(step: cibuildwheel.linux.BuildStep) -> list[OCIContainerEngineConfig]:
+    def container_engines(
+        step: cibuildwheel.platforms.linux.BuildStep,
+    ) -> list[OCIContainerEngineConfig]:
         return [options.build_options(c.identifier).container_engine for c in step.platform_configs]
 
     pprint(build_steps)
diff --git a/unit_test/main_tests/conftest.py b/unit_test/main_tests/conftest.py
index 3751b78a5..e01c8c027 100644
--- a/unit_test/main_tests/conftest.py
+++ b/unit_test/main_tests/conftest.py
@@ -6,7 +6,8 @@
 
 import pytest
 
-from cibuildwheel import __main__, architecture, linux, macos, pyodide, windows
+from cibuildwheel import __main__, architecture
+from cibuildwheel.platforms import linux, macos, pyodide, windows
 from cibuildwheel.util import file
 
 
diff --git a/unit_test/main_tests/main_options_test.py b/unit_test/main_tests/main_options_test.py
index a869d615f..efc1074cc 100644
--- a/unit_test/main_tests/main_options_test.py
+++ b/unit_test/main_tests/main_options_test.py
@@ -50,22 +50,49 @@ def test_output_dir_argument(also_set_environment, intercepted_build_args, monke
 
 @pytest.mark.usefixtures("platform", "allow_empty")
 def test_build_selector(intercepted_build_args, monkeypatch):
-    BUILD = "some build* *-selector"
-    SKIP = "some skip* *-selector"
-
-    monkeypatch.setenv("CIBW_BUILD", BUILD)
-    monkeypatch.setenv("CIBW_SKIP", SKIP)
+    monkeypatch.setenv("CIBW_BUILD", "cp313-*")
+    monkeypatch.setenv("CIBW_SKIP", "cp39-*")
 
     main()
 
     intercepted_build_selector = intercepted_build_args.args[0].globals.build_selector
     assert isinstance(intercepted_build_selector, BuildSelector)
-    assert intercepted_build_selector("build24-this")
-    assert not intercepted_build_selector("skip65-that")
+    assert intercepted_build_selector("cp313-something-to-build")
+    assert not intercepted_build_selector("cp39-something-to-skip")
     # This unit test is just testing the options of 'main'
     # Unit tests for BuildSelector are in build_selector_test.py
 
 
+@pytest.mark.usefixtures("platform", "allow_empty")
+def test_invalid_build_selector(monkeypatch, capsys):
+    monkeypatch.setenv("CIBW_BUILD", "invalid")
+
+    with pytest.raises(SystemExit) as e:
+        main()
+
+    assert e.value.code == 2
+    _, err = capsys.readouterr()
+    assert "Invalid build selector" in err
+
+
+@pytest.mark.parametrize(
+    ("option_name", "option_env_var"),
+    [
+        ("skip", "CIBW_SKIP"),
+        ("test_skip", "CIBW_TEST_SKIP"),
+    ],
+)
+@pytest.mark.usefixtures("platform", "intercepted_build_args")
+def test_invalid_skip_selector(monkeypatch, capsys, option_name, option_env_var):
+    monkeypatch.setenv(option_env_var, "invalid")
+
+    main()
+
+    _, err = capsys.readouterr()
+    print(err)
+    assert f"Invalid {option_name} selector" in err
+
+
 @pytest.mark.usefixtures("platform", "intercepted_build_args")
 def test_empty_selector(monkeypatch):
     monkeypatch.setenv("CIBW_SKIP", "*")
@@ -313,7 +340,7 @@ def test_build_selector_deprecated_error(monkeypatch, selector, pattern, capsys)
 
     stderr = capsys.readouterr().err
     series = "2" if "6" in pattern else "1"
-    msg = f"cibuildwheel 3.x no longer supports Python < 3.8. Please use the {series}.x series or update {selector}"
+    msg = f"cibuildwheel 3.x no longer supports Python < 3.8. Please use the {series}.x series or update"
     assert msg in stderr
 
 
diff --git a/unit_test/option_prepare_test.py b/unit_test/option_prepare_test.py
index 27b25377c..f17841fbe 100644
--- a/unit_test/option_prepare_test.py
+++ b/unit_test/option_prepare_test.py
@@ -8,7 +8,7 @@
 
 import pytest
 
-from cibuildwheel import linux
+from cibuildwheel import platforms
 from cibuildwheel.__main__ import main
 from cibuildwheel.oci_container import OCIPlatform
 from cibuildwheel.util import file
@@ -39,10 +39,11 @@ def ignore_context_call(*args, **kwargs):
     monkeypatch.setattr(subprocess, "Popen", fail_on_call)
     monkeypatch.setattr(subprocess, "run", ignore_call)
     monkeypatch.setattr(file, "download", fail_on_call)
-    monkeypatch.setattr("cibuildwheel.linux.OCIContainer", ignore_context_call)
+    monkeypatch.setattr("cibuildwheel.platforms.linux.OCIContainer", ignore_context_call)
 
     monkeypatch.setattr(
-        "cibuildwheel.linux.build_in_container", mock.Mock(spec=linux.build_in_container)
+        "cibuildwheel.platforms.linux.build_in_container",
+        mock.Mock(spec=platforms.linux.build_in_container),
     )
     monkeypatch.setattr("cibuildwheel.__main__.print_new_wheels", ignore_context_call)
 
@@ -53,7 +54,7 @@ def test_build_default_launches(monkeypatch):
 
     main()
 
-    build_in_container = typing.cast(mock.Mock, linux.build_in_container)
+    build_in_container = typing.cast(mock.Mock, platforms.linux.build_in_container)
 
     assert build_in_container.call_count == 4
 
@@ -121,7 +122,7 @@ def test_build_with_override_launches(monkeypatch, tmp_path):
 
     main()
 
-    build_in_container = typing.cast(mock.Mock, linux.build_in_container)
+    build_in_container = typing.cast(mock.Mock, platforms.linux.build_in_container)
 
     assert build_in_container.call_count == 6
 
diff --git a/unit_test/options_test.py b/unit_test/options_test.py
index 7f497a375..143f7fdc0 100644
--- a/unit_test/options_test.py
+++ b/unit_test/options_test.py
@@ -6,13 +6,13 @@
 import pytest
 
 from cibuildwheel import errors
-from cibuildwheel.__main__ import get_build_identifiers, get_platform_module
 from cibuildwheel.bashlex_eval import local_environment_executor
 from cibuildwheel.options import (
     CommandLineArguments,
     Options,
     _get_pinned_container_images,
 )
+from cibuildwheel.platforms import ALL_PLATFORM_MODULES, get_build_identifiers
 from cibuildwheel.selector import EnableGroup
 from cibuildwheel.util import resources
 from cibuildwheel.util.packaging import DependencyConstraints
@@ -51,7 +51,7 @@ def test_options_1(tmp_path, monkeypatch):
 
     options = Options(platform="linux", command_line_arguments=args, env={})
 
-    module = get_platform_module("linux")
+    module = ALL_PLATFORM_MODULES["linux"]
     identifiers = get_build_identifiers(
         platform_module=module,
         build_selector=options.globals.build_selector,