diff --git a/.github/workflows/python.yml b/.github/workflows/python.yml
index 7ad16f0..dcba4b5 100644
--- a/.github/workflows/python.yml
+++ b/.github/workflows/python.yml
@@ -24,11 +24,11 @@ jobs:
     strategy:
       matrix:
         python-version: [
-          '3.10',
           '3.11',
           '3.12',
           '3.13',
           '3.14',
+          '3.15',
         ]
 
     steps:
@@ -37,16 +37,20 @@ jobs:
         uses: actions/setup-python@v7
         with:
           python-version: ${{ matrix.python-version }}
+          cache: 'pip'
       - name: Install dependencies
         run: |
           python -m pip install --upgrade pip
-          cd python && pip install .[dev]
+          cd python && pip install . --group test
       - name: Run tests
         run: cd python && tox
         env:
           TOX_GH_MAJOR_MINOR: ${{ matrix.python-version }}
-      - uses: astral-sh/ruff-action@v3
+      - uses: astral-sh/ruff-action@v4.1.0
         with:
           src: "./python"
+          args: "--version"
+      - name: Lint code
+        run: ruff check -v
       - name: Check formatting
-        run: cd python && black --check .
+        run: ruff format -v
diff --git a/python/.gitignore b/python/.gitignore
index 25aacff..0cebcfc 100644
--- a/python/.gitignore
+++ b/python/.gitignore
@@ -1,3 +1,4 @@
 build/
 dist/
 *.egg-info/
+*.lock
diff --git a/python/MANIFEST.in b/python/MANIFEST.in
index fce3334..509e6a6 100644
--- a/python/MANIFEST.in
+++ b/python/MANIFEST.in
@@ -1,6 +1,5 @@
 include README.rst
 include LICENSE
-include tox.ini
 recursive-include http_ece/tests *
 global-exclude */__pycache__/*
 
diff --git a/python/http_ece/tests/test_ece.py b/python/http_ece/tests/test_ece.py
index 3d9f713..c0f09b3 100644
--- a/python/http_ece/tests/test_ece.py
+++ b/python/http_ece/tests/test_ece.py
@@ -30,7 +30,6 @@ def logbuf(msg, buf):
     logmsg(msg + ": [" + str(len(buf)) + "]")
     for i in list(range(0, len(buf), 48)):
         logmsg("    " + repr(buf[i : i + 48]))
-    return
 
 
 def b64e(arg):
diff --git a/python/pyproject.toml b/python/pyproject.toml
index 9f07f0a..38f447b 100644
--- a/python/pyproject.toml
+++ b/python/pyproject.toml
@@ -6,30 +6,36 @@ build-backend = "setuptools.build_meta"
 name = "http_ece"
 version = "1.2.1"
 license = "MIT"
+license-files = ["LICENSE"]
 authors = [{ name = "Martin Thomson", email = "martin.thomson@gmail.com" }]
 keywords = ["crypto http"]
 classifiers = [
     "Development Status :: 4 - Beta",
-    "Programming Language :: Python :: 3.10",
     "Programming Language :: Python :: 3.11",
     "Programming Language :: Python :: 3.12",
     "Programming Language :: Python :: 3.13",
     "Programming Language :: Python :: 3.14",
+    "Programming Language :: Python :: 3.15",
 ]
 description = "Encrypted Content Encoding for HTTP"
 readme = { file = "README.rst", content-type = "text/x-rst" }
-requires-python = ">=3.10"
+requires-python = ">=3.11"
 dependencies = ["cryptography>=46.0.1"]
 
-[project.optional-dependencies]
-dev = [
-    "black>=26.3.1",
-    "pytest",
+[dependency-groups]
+lint = [
+    "ruff==0.17.4",
+]
+test = [
+    "pytest>=9",
     "pytest-cov",
-    "ruff==0.14.10",
-    "tox",
+    "tox>=4.22",
     "tox-gh",
 ]
+dev = [
+    { include-group = "lint" },
+    { include-group = "test" },
+]
 
 [project.urls]
 Repository = "https://github.com/web-push-libs/encrypted-content-encoding"
@@ -52,3 +58,26 @@ lint.select = ["A", "F", "FURB", "I", "PERF", "PT", "PTH", "RUF", "S", "UP"]
 
 [tool.setuptools]
 packages = ["http_ece"]
+
+[tool.tox]
+env_list = [
+    "py311",
+    "py312",
+    "py313",
+    "py314",
+    "py315",
+]
+
+[tool.tox.env_run_base]
+description = "run tests with pytest under {base_python}"
+dependency_groups = ["test"]
+commands = [
+    ["pytest", "{posargs}"],
+]
+
+[tool.tox.gh.python]
+"3.11" = ["py311"]
+"3.12" = ["py312"]
+"3.13" = ["py313"]
+"3.14" = ["py314"]
+"3.15" = ["py315"]
diff --git a/python/tox.ini b/python/tox.ini
deleted file mode 100644
index 800e88b..0000000
--- a/python/tox.ini
+++ /dev/null
@@ -1,31 +0,0 @@
-# Tox (http://tox.testrun.org/) is a tool for running tests
-# in multiple virtualenvs. This configuration file will run the
-# test suite on all supported python versions. To use it, "pip install tox"
-# and then run "tox" from this directory.
-
-[tox]
-envlist = py310,py311,py312,py313,py314
-
-[gh]
-; Github Action
-python =
-  3.10 = py310
-  3.11 = py311
-  3.12 = py312
-  3.13 = py313
-  3.14 = py314
-
-[testenv]
-basepython =
-  py310: python3.10
-  py311: python3.11
-  py312: python3.12
-  py313: python3.13
-  py314: python3.14
-commands =
-  pytest \
-    []
-deps =
-  pytest
-  pytest-cov
-  flake8