diff --git a/.github/workflows/reusable-linters.yml b/.github/workflows/reusable-linters.yml
index 68417ea5..95eee3e1 100644
--- a/.github/workflows/reusable-linters.yml
+++ b/.github/workflows/reusable-linters.yml
@@ -71,9 +71,7 @@ jobs:
       with:
         token: ${{ secrets.codecov-token }}
         files: >-
-          .tox/.tmp/.mypy/python-3.12/cobertura.xml,
-          .tox/.tmp/.mypy/python-3.10/cobertura.xml,
-          .tox/.tmp/.mypy/python-3.8/cobertura.xml
+          .tox/.tmp/.mypy/python-3.11/cobertura.xml
         flags: >-
           CI-GHA,
           MyPy
diff --git a/.mypy.ini b/.mypy.ini
index 912c9402..9741fed6 100644
--- a/.mypy.ini
+++ b/.mypy.ini
@@ -1,48 +1,33 @@
 [mypy]
-python_version = 3.8
-color_output = True
-error_summary = True
-files =
-  frozenlist/,
-  packaging/,
-  tests/
-
+files = frozenlist, packaging, tests
 check_untyped_defs = True
-
-disallow_untyped_defs = True
+follow_imports_for_stubs = True
+disallow_any_decorated = True
 disallow_any_generics = True
-
-enable_error_code =
-  ignore-without-code
-
-follow_imports = normal
-
-ignore_missing_imports = False
-
-pretty = true
-
-show_column_numbers = true
-show_error_codes = true
-strict_optional = True
-
-warn_no_return = True
+disallow_any_unimported = True
+disallow_incomplete_defs = True
+disallow_subclassing_any = True
+disallow_untyped_calls = True
+disallow_untyped_decorators = True
+disallow_untyped_defs = True
+# TODO(PY312): explicit-override
+enable_error_code = ignore-without-code, possibly-undefined, redundant-expr, redundant-self, truthy-bool, truthy-iterable, unused-awaitable
+extra_checks = True
+implicit_reexport = False
+no_implicit_optional = True
+pretty = True
+show_column_numbers = True
+show_error_codes = True
+show_error_code_links = True
+strict_equality = True
+warn_incomplete_stub = True
 warn_redundant_casts = True
+warn_return_any = True
+warn_unreachable = True
 warn_unused_ignores = True
 
 [mypy-Cython.*]
 ignore_missing_imports = true
 
-[mypy-distutils.*]
-ignore_missing_imports = true
-
-[mypy-expandvars]
-ignore_missing_imports = true
-
-[mypy-pep517_backend.*]
-check_untyped_defs = False
-disallow_any_generics = False
-disallow_untyped_defs = False
-warn_unused_ignores = False
-
-[mypy-tomllib]
+[mypy-expandvars.*]
 ignore_missing_imports = true
diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 176aaabd..6ac89ef2 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -168,8 +168,8 @@ repos:
   rev: v1.14.1
   hooks:
   - id: mypy
-    alias: mypy-py312
-    name: MyPy, for Python 3.12
+    alias: mypy-py311
+    name: MyPy, for Python 3.11
     additional_dependencies:
     - lxml  # dep of `--txt-report`, `--cobertura-xml-report` & `--html-report`
     - pytest
@@ -178,42 +178,10 @@ repos:
     args:
     - --install-types
     - --non-interactive
-    - --python-version=3.12
-    - --txt-report=.tox/.tmp/.mypy/python-3.12
-    - --cobertura-xml-report=.tox/.tmp/.mypy/python-3.12
-    - --html-report=.tox/.tmp/.mypy/python-3.12
-    pass_filenames: false
-  - id: mypy
-    alias: mypy-py310
-    name: MyPy, for Python 3.10
-    additional_dependencies:
-    - lxml  # dep of `--txt-report`, `--cobertura-xml-report` & `--html-report`
-    - pytest
-    - tomli  # requirement of packaging/pep517_backend/
-    - types-setuptools  # requirement of packaging/pep517_backend/
-    args:
-    - --install-types
-    - --non-interactive
-    - --python-version=3.10
-    - --txt-report=.tox/.tmp/.mypy/python-3.10
-    - --cobertura-xml-report=.tox/.tmp/.mypy/python-3.10
-    - --html-report=.tox/.tmp/.mypy/python-3.10
-    pass_filenames: false
-  - id: mypy
-    alias: mypy-py38
-    name: MyPy, for Python 3.8
-    additional_dependencies:
-    - lxml  # dep of `--txt-report`, `--cobertura-xml-report` & `--html-report`
-    - pytest
-    - tomli  # requirement of packaging/pep517_backend/
-    - types-setuptools  # requirement of packaging/pep517_backend/
-    args:
-    - --install-types
-    - --non-interactive
-    - --python-version=3.8
-    - --txt-report=.tox/.tmp/.mypy/python-3.8
-    - --cobertura-xml-report=.tox/.tmp/.mypy/python-3.8
-    - --html-report=.tox/.tmp/.mypy/python-3.8
+    - --python-version=3.11
+    - --txt-report=.tox/.tmp/.mypy/python-3.11
+    - --cobertura-xml-report=.tox/.tmp/.mypy/python-3.11
+    - --html-report=.tox/.tmp/.mypy/python-3.11
     pass_filenames: false
 
 - repo: https://github.com/rhysd/actionlint
diff --git a/packaging/pep517_backend/_backend.py b/packaging/pep517_backend/_backend.py
index 23f80c2a..bce4a9e1 100644
--- a/packaging/pep517_backend/_backend.py
+++ b/packaging/pep517_backend/_backend.py
@@ -4,7 +4,6 @@
 from __future__ import annotations
 
 import os
-import typing as t
 from contextlib import contextmanager, nullcontext, suppress
 from functools import partial
 from pathlib import Path
@@ -12,6 +11,7 @@
 from sys import implementation as _system_implementation
 from sys import stderr as _standard_error_stream
 from tempfile import TemporaryDirectory
+from typing import Dict, Iterator, List, Union
 from warnings import warn as _warn_that
 
 from setuptools.build_meta import build_sdist as _setuptools_build_sdist
@@ -55,7 +55,7 @@
     'get_requires_for_build_wheel',
     'prepare_metadata_for_build_wheel',
     *(
-        () if _setuptools_build_editable is None
+        () if _setuptools_build_editable is None  # type: ignore[redundant-expr]
         else (
             'build_editable',
             'get_requires_for_build_editable',
@@ -64,7 +64,7 @@
     ),
 )
 
-_ConfigDict = t.Dict[str, t.Union[str, t.List[str], None]]
+_ConfigDict = Dict[str, Union[str, List[str], None]]
 
 
 CYTHON_TRACING_CONFIG_SETTING = 'with-cython-tracing'
@@ -86,7 +86,7 @@
 """A fallback for ``pure-python`` is not set."""
 
 
-def _is_truthy_setting_value(setting_value) -> bool:
+def _is_truthy_setting_value(setting_value: str) -> bool:
     truthy_values = {'', None, 'true', '1', 'on'}
     return setting_value.lower() in truthy_values
 
@@ -107,7 +107,7 @@ def _get_setting_value(
             continue
 
         with suppress(lookup_errors):  # type: ignore[arg-type]
-            return _is_truthy_setting_value(src_mapping[src_key])  # type: ignore[index]
+            return _is_truthy_setting_value(src_mapping[src_key])  # type: ignore[arg-type,index]
 
     return default
 
@@ -124,7 +124,7 @@ def _make_pure_python(config_settings: _ConfigDict | None = None) -> bool:
 def _include_cython_line_tracing(
         config_settings: _ConfigDict | None = None,
         *,
-        default=False,
+        default: bool = False,
 ) -> bool:
     return _get_setting_value(
         config_settings,
@@ -135,7 +135,7 @@ def _include_cython_line_tracing(
 
 
 @contextmanager
-def patched_distutils_cmd_install():
+def patched_distutils_cmd_install() -> Iterator[None]:
     """Make `install_lib` of `install` cmd always use `platlib`.
 
     :yields: None
@@ -143,19 +143,19 @@ def patched_distutils_cmd_install():
     # Without this, build_lib puts stuff under `*.data/purelib/` folder
     orig_finalize = _distutils_install_cmd.finalize_options
 
-    def new_finalize_options(self):  # noqa: WPS430
+    def new_finalize_options(self: _distutils_install_cmd) -> None:  # noqa: WPS430
         self.install_lib = self.install_platlib
         orig_finalize(self)
 
-    _distutils_install_cmd.finalize_options = new_finalize_options
+    _distutils_install_cmd.finalize_options = new_finalize_options  # type: ignore[method-assign]
     try:
         yield
     finally:
-        _distutils_install_cmd.finalize_options = orig_finalize
+        _distutils_install_cmd.finalize_options = orig_finalize  # type: ignore[method-assign]
 
 
 @contextmanager
-def patched_dist_has_ext_modules():
+def patched_dist_has_ext_modules() -> Iterator[None]:
     """Make `has_ext_modules` of `Distribution` always return `True`.
 
     :yields: None
@@ -163,15 +163,15 @@ def patched_dist_has_ext_modules():
     # Without this, build_lib puts stuff under `*.data/platlib/` folder
     orig_func = _DistutilsDistribution.has_ext_modules
 
-    _DistutilsDistribution.has_ext_modules = lambda *args, **kwargs: True
+    _DistutilsDistribution.has_ext_modules = lambda *args, **kwargs: True  # type: ignore[method-assign]
     try:
         yield
     finally:
-        _DistutilsDistribution.has_ext_modules = orig_func
+        _DistutilsDistribution.has_ext_modules = orig_func  # type: ignore[method-assign]
 
 
 @contextmanager
-def patched_dist_get_long_description():
+def patched_dist_get_long_description() -> Iterator[None]:
     """Make `has_ext_modules` of `Distribution` always return `True`.
 
     :yields: None
@@ -179,16 +179,17 @@ def patched_dist_get_long_description():
     # Without this, build_lib puts stuff under `*.data/platlib/` folder
     _orig_func = _DistutilsDistributionMetadata.get_long_description
 
-    def _get_sanitized_long_description(self):
+    def _get_sanitized_long_description(self: _DistutilsDistributionMetadata) -> str:
+        assert self.long_description is not None
         return sanitize_rst_roles(self.long_description)
 
-    _DistutilsDistributionMetadata.get_long_description = (
+    _DistutilsDistributionMetadata.get_long_description = (  # type: ignore[method-assign]
         _get_sanitized_long_description
     )
     try:
         yield
     finally:
-        _DistutilsDistributionMetadata.get_long_description = _orig_func
+        _DistutilsDistributionMetadata.get_long_description = _orig_func  # type: ignore[method-assign]
 
 
 def _exclude_dir_path(
@@ -215,7 +216,7 @@ def _exclude_dir_path(
 
 
 @contextmanager
-def _in_temporary_directory(src_dir: Path) -> t.Iterator[None]:
+def _in_temporary_directory(src_dir: Path) -> Iterator[None]:
     with TemporaryDirectory(prefix='.tmp-frozenlist-pep517-') as tmp_dir:
         tmp_dir_path = Path(tmp_dir)
         root_tmp_dir_path = tmp_dir_path.parent
@@ -238,7 +239,7 @@ def maybe_prebuild_c_extensions(
         line_trace_cython_when_unset: bool = False,
         build_inplace: bool = False,
         config_settings: _ConfigDict | None = None,
-) -> t.Generator[None, t.Any, t.Any]:
+) -> Iterator[None]:
     """Pre-build C-extensions in a temporary directory, when needed.
 
     This context manager also patches metadata, setuptools and distutils.
diff --git a/packaging/pep517_backend/_compat.py b/packaging/pep517_backend/_compat.py
index 5e2ffe09..af50e577 100644
--- a/packaging/pep517_backend/_compat.py
+++ b/packaging/pep517_backend/_compat.py
@@ -1,16 +1,19 @@
 """Cross-python stdlib shims."""
 
 import os
-import typing as t
+import sys
 from contextlib import contextmanager
 from pathlib import Path
+from typing import Iterator
 
-try:
-    from contextlib import chdir as chdir_cm  # type: ignore[attr-defined]
-except ImportError:
+if sys.version_info >= (3, 11):
+    from contextlib import chdir as chdir_cm
+    from tomllib import loads as load_toml_from_string
+else:
+    from tomli import loads as load_toml_from_string
 
     @contextmanager  # type: ignore[no-redef]
-    def chdir_cm(path: os.PathLike) -> t.Iterator[None]:
+    def chdir_cm(path: "os.PathLike[str]") -> Iterator[None]:
         """Temporarily change the current directory, recovering on exit."""
         original_wd = Path.cwd()
         os.chdir(path)
@@ -20,10 +23,4 @@ def chdir_cm(path: os.PathLike) -> t.Iterator[None]:
             os.chdir(original_wd)
 
 
-try:
-    from tomllib import loads as load_toml_from_string
-except ImportError:
-    from tomli import loads as load_toml_from_string  # type: ignore[no-redef]
-
-
 __all__ = ("chdir_cm", "load_toml_from_string")  # noqa: WPS410
diff --git a/packaging/pep517_backend/_cython_configuration.py b/packaging/pep517_backend/_cython_configuration.py
index ef5ea391..b55df672 100644
--- a/packaging/pep517_backend/_cython_configuration.py
+++ b/packaging/pep517_backend/_cython_configuration.py
@@ -6,6 +6,7 @@
 from contextlib import contextmanager
 from pathlib import Path
 from sys import version_info as _python_version_tuple
+from typing import Iterator, TypedDict
 
 from expandvars import expandvars
 
@@ -13,7 +14,14 @@
 from ._transformers import get_cli_kwargs_from_config, get_enabled_cli_flags_from_config
 
 
-def get_local_cython_config() -> dict:
+class Config(TypedDict):
+    env: dict[str, str]
+    flags: dict[str, bool]
+    kwargs: dict[str, str]
+    src: list[str]
+
+
+def get_local_cython_config() -> Config:
     """Grab optional build dependencies from pyproject.toml config.
 
     :returns: config section from ``pyproject.toml``
@@ -67,10 +75,10 @@ def get_local_cython_config() -> dict:
     """
     config_toml_txt = (Path.cwd().resolve() / 'pyproject.toml').read_text()
     config_mapping = load_toml_from_string(config_toml_txt)
-    return config_mapping['tool']['local']['cythonize']
+    return config_mapping['tool']['local']['cythonize']  # type: ignore[no-any-return]
 
 
-def make_cythonize_cli_args_from_config(config) -> list[str]:
+def make_cythonize_cli_args_from_config(config: Config) -> list[str]:
     py_ver_arg = f'-{_python_version_tuple.major!s}'
 
     cli_flags = get_enabled_cli_flags_from_config(config['flags'])
@@ -80,7 +88,7 @@ def make_cythonize_cli_args_from_config(config) -> list[str]:
 
 
 @contextmanager
-def patched_env(env: dict[str, str], cython_line_tracing_requested: bool):
+def patched_env(env: dict[str, str], cython_line_tracing_requested: bool) -> Iterator[None]:
     """Temporary set given env vars.
 
     :param env: tmp env vars to set
diff --git a/packaging/pep517_backend/_transformers.py b/packaging/pep517_backend/_transformers.py
index 76f15f40..4e6dca4e 100644
--- a/packaging/pep517_backend/_transformers.py
+++ b/packaging/pep517_backend/_transformers.py
@@ -2,25 +2,26 @@
 
 from itertools import chain
 from re import sub as _substitute_with_regexp
+from typing import Dict, Iterable, Iterator, List, Mapping, Tuple, Union
 
 
-def _emit_opt_pairs(opt_pair):
+def _emit_opt_pairs(opt_pair: Tuple[str, Union[str, Dict[str, str]]]) -> Iterator[str]:
     flag, flag_value = opt_pair
     flag_opt = f"--{flag!s}"
     if isinstance(flag_value, dict):
-        sub_pairs = flag_value.items()
+        sub_pairs: Iterable[Tuple[str, ...]] = flag_value.items()
     else:
         sub_pairs = ((flag_value,),)
 
     yield from ("=".join(map(str, (flag_opt,) + pair)) for pair in sub_pairs)
 
 
-def get_cli_kwargs_from_config(kwargs_map):
+def get_cli_kwargs_from_config(kwargs_map: Mapping[str, str]) -> List[str]:
     """Make a list of options with values from config."""
     return list(chain.from_iterable(map(_emit_opt_pairs, kwargs_map.items())))
 
 
-def get_enabled_cli_flags_from_config(flags_map):
+def get_enabled_cli_flags_from_config(flags_map: Mapping[str, bool]) -> List[str]:
     """Make a list of enabled boolean flags from config."""
     return [f"--{flag}" for flag, is_enabled in flags_map.items() if is_enabled]
 
diff --git a/packaging/pep517_backend/cli.py b/packaging/pep517_backend/cli.py
index f3a1c85c..52cfcbcb 100644
--- a/packaging/pep517_backend/cli.py
+++ b/packaging/pep517_backend/cli.py
@@ -5,6 +5,7 @@
 import sys
 from itertools import chain
 from pathlib import Path
+from typing import Sequence
 
 from Cython.Compiler.Main import compile as _translate_cython_cli_cmd
 from Cython.Compiler.Main import parse_command_line as _split_cython_cli_args
@@ -18,7 +19,7 @@
 _PROJECT_PATH = Path(__file__).parents[2]
 
 
-def run_main_program(argv) -> int | str:
+def run_main_program(argv: Sequence[str]) -> int | str:
     """Invoke ``translate-cython`` or fail."""
     if len(argv) != 2:
         return 'This program only accepts one argument -- "translate-cython"'
@@ -43,7 +44,7 @@ def run_main_program(argv) -> int | str:
     )
 
     with _patched_cython_env(config['env'], cython_line_tracing_requested=True):
-        return _translate_cython_cli_cmd(
+        return _translate_cython_cli_cmd(  # type: ignore[no-any-return]
             cython_sources,
             cython_options,
         ).num_errors
diff --git a/packaging/pep517_backend/hooks.py b/packaging/pep517_backend/hooks.py
index f8f3fb24..f601b193 100644
--- a/packaging/pep517_backend/hooks.py
+++ b/packaging/pep517_backend/hooks.py
@@ -2,7 +2,7 @@
 
 from contextlib import suppress as _suppress
 
-from setuptools.build_meta import *  # Re-exporting PEP 517 hooks  # pylint: disable=unused-wildcard-import,wildcard-import  # noqa: E501, F401, F403
+from setuptools.build_meta import *  # Re-exporting PEP 517 hooks  # pylint: disable=unused-wildcard-import,wildcard-import  # noqa: F401, F403
 
 # Re-exporting PEP 517 hooks
 from ._backend import (  # type: ignore[assignment]
diff --git a/requirements/ci.txt b/requirements/ci.txt
index b1283dae..08ff38d0 100644
--- a/requirements/ci.txt
+++ b/requirements/ci.txt
@@ -7,3 +7,4 @@ pytest==7.4.3
 pytest-cov==4.1.0
 tox==4.11.4
 twine==4.0.2
+types-setuptools==75.8.0.20250210
diff --git a/setup.cfg b/setup.cfg
index d8c9f7e9..c2148c55 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -65,7 +65,8 @@ include_package_data = True
 max-line-length=88
 
 [flake8]
-ignore = N801,N802,N803,E226,W503,W504,E252
+extend-select = B950
+ignore = E226,E252,E501,N801,N802,N803,W503,W504
 max-line-length = 88
 
 # Allow certain violations in certain files: