diff --git a/.github/dependabot.yml b/.github/dependabot.yml
index 9d866e3..6af4d85 100644
--- a/.github/dependabot.yml
+++ b/.github/dependabot.yml
@@ -5,6 +5,11 @@
 
 version: 2
 updates:
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    target-branch: "develop"
+    schedule:
+      interval: "weekly"
   - package-ecosystem: "pip" # See documentation for possible values
     directory: "/" # Location of package manifests
     schedule:
diff --git a/.github/workflows/build-and-deploy.yml b/.github/workflows/build-and-deploy.yml
index faccd5c..b7e1ab8 100644
--- a/.github/workflows/build-and-deploy.yml
+++ b/.github/workflows/build-and-deploy.yml
@@ -9,10 +9,10 @@ jobs:
   build-and-deploy:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v4
-    - uses: actions/setup-python@v5
+    - uses: actions/checkout@v7
+    - uses: actions/setup-python@v7
       with:
-        python-version: "3.14"
+        python-version: "3.15"
     - name: install dependencies
       run: |
         python -m pip install --upgrade pip
diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 873bc6d..b764da4 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -1,30 +1,38 @@
 name: tests
 
-on: [push, pull_request]
+on:
+  push:
+  pull_request:
+  workflow_dispatch:
+
+permissions:
+  contents: read
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
 
 jobs:
 
   test:
+    timeout-minutes: 60
     strategy:
       fail-fast: false
       matrix:
         include:
-          - python: "3.14"
+          - python: "3.15"
             toxenv: flake8
             os: ubuntu-latest
-          - python: "3.14"
+          - python: "3.15"
             toxenv: mypy
             os: ubuntu-latest
-          - python: "3.14"
+          - python: "3.15"
             toxenv: pylint
             os: ubuntu-latest
-          - python: "3.14"
+          - python: "3.15"
             toxenv: black
             os: ubuntu-latest
 
-          - python: "3.10"
-            toxenv: py310
-            os: ubuntu-latest
           - python: "3.11"
             toxenv: py311
             os: ubuntu-latest
@@ -37,32 +45,35 @@ jobs:
           - python: "3.14"
             toxenv: py314
             os: ubuntu-latest
-
-          - python: "pypy3.10"
-            toxenv: pypy310
+          - python: "3.15"
+            toxenv: py315
             os: ubuntu-latest
-          - python: "pypy3.11"
+
+          - python: "pypy-3.11"
             toxenv: pypy311
             os: ubuntu-latest
+          - python: "pypy-3.12"
+            toxenv: pypy312
+            os: ubuntu-latest
 
-          - python: "3.14"
-            toxenv: py314
+          - python: "3.15"
+            toxenv: py315
             os: macos-latest
-          - python: "3.14"
-            toxenv: py314
+          - python: "3.15"
+            toxenv: py315
             os: windows-latest
 
     runs-on: ${{ matrix.os }}
     steps:
-      - uses: actions/checkout@v4
-      - uses: actions/setup-python@v5
+      - uses: actions/checkout@v7
+      - uses: actions/setup-python@v7
         with:
-          python-version: ${{  matrix.python }}
-      - name: install dependencies
-        run: python -m pip install --upgrade pip tox
-      - name: run
-        env:
-          TOXENV: ${{ matrix.toxenv }}
-        run: tox
-      - name: setup
-        run: pip install -e .
+          python-version: ${{ matrix.python }}
+          cache: pip
+          cache-dependency-path: |
+            pyproject.toml
+            tox.ini
+      - name: Install tox
+        run: python -m pip install --upgrade pip "tox>=4,<5"
+      - name: Run checks
+        run: python -m tox run -e ${{ matrix.toxenv }}
diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index fe30c3b..640716b 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -1,5 +1,5 @@
 repos:
   - repo: https://github.com/psf/black
-    rev: 22.10.0
+    rev: 25.12.0
     hooks:
       - id: black
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 50ecb90..6dd2a9e 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -6,7 +6,17 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 
 ## Unreleased
 
+### Changed
+- Minimum Python version is now 3.11; CPython and PyPy 3.10 are no longer supported.
+- Python 3.15 is primary for linting, packaging, and cross-platform tests, with
+  CPython 3.11 through 3.14 compatibility coverage.
+- Modernized GitHub Actions, dependency caching, and Black configuration.
+
+### Added
+- Required CI coverage for stable PyPy 3.12 alongside PyPy 3.11.
+
 ### Fixed
+- Supply the dependencies of PyPy's bundled cffi and HPy packages in tox.
 - Fixed bug in `Perm.rtlmax_ltrmin_decomposition` and fixed associated tests.
 
 ## 2.3.1 - 2025-06-13 
diff --git a/README.rst b/README.rst
index 1277f39..a79fd9e 100644
--- a/README.rst
+++ b/README.rst
@@ -43,6 +43,8 @@ To install Permuta on your system, run:
 
     pip install permuta
 
+Python 3.11 or newer is required.
+
 It is also possible to install Permuta in development mode to work on the
 source code, in which case you run the following after cloning the repository:
 
diff --git a/pyproject.toml b/pyproject.toml
index 6835be4..10b31a9 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -17,16 +17,17 @@ classifiers = [
     "Intended Audience :: Education",
     "Intended Audience :: Science/Research",
     "License :: OSI Approved :: BSD License",
-    "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",
     "Programming Language :: Python :: Implementation :: CPython",
     "Programming Language :: Python :: Implementation :: PyPy",
     "Topic :: Education",
     "Topic :: Scientific/Engineering :: Mathematics",
 ]
-requires-python = ">=3.10"
+requires-python = ">=3.11"
 dependencies = [
     "automata-lib==9.2.0",
 ]
@@ -53,7 +54,7 @@ include = [
 ]
 
 [tool.black]
-target-version = ['py310']
+target-version = ['py311']
 include = '\.pyi?$'
 exclude = '''
 
diff --git a/tox.ini b/tox.ini
index 082c98b..c0808e0 100644
--- a/tox.ini
+++ b/tox.ini
@@ -4,28 +4,35 @@
 # and then run "tox" from this directory.
 
 [tox]
+minversion = 4
 envlist =
     flake8, mypy, pylint, black
-    py{310,311,312,313,314},
-    pypy{310,311}
+    py{311,312,313,314,315},
+    pypy{311,312}
 
 [default]
-basepython=python3.14
+basepython=python3.15
 
 [testenv]
 description = run test
 basepython =
-    py310: python3.10
     py311: python3.11
     py312: python3.12
     py313: python3.13
     py314: python3.14
-    pypy310: pypy3.10
+    py315: python3.15
     pypy311: pypy3.11
+    pypy312: pypy3.12
 deps =
     pytest
     pytest-timeout
-commands = pytest
+    # PyPy bundles cffi and HPy; virtualenv may omit their dependencies.
+    pycparser; platform_python_implementation == "PyPy"
+    setuptools; platform_python_implementation == "PyPy"
+commands =
+    python -m pip check
+    python -m pip freeze
+    python -m pytest {posargs}
 
 [pytest]
 addopts = --doctest-modules --doctest-ignore-import-errors
@@ -59,6 +66,7 @@ commands = mypy
 [testenv:black]
 description = check that comply with autoformating
 basepython = {[default]basepython}
+skip_install = True
 deps =
     black==25.12.0
 commands = black --check --diff .