diff --git a/.github/workflows/python-release.yml b/.github/workflows/python-release.yml
index fca94cb0..5a8b3a9c 100644
--- a/.github/workflows/python-release.yml
+++ b/.github/workflows/python-release.yml
@@ -8,17 +8,17 @@ jobs:
   release:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v3
-    - name: Set up Python 3.10
-      uses: actions/setup-python@v4
+    - uses: actions/checkout@v4
+    - name: Set up Python 3.12
+      uses: actions/setup-python@v5
       with:
-        python-version: "3.10"
+        python-version: "3.12"
     - name: Install build requirements
-      run: python -m pip install wheel
+      run: python -m pip install setuptools wheel
     - name: Build package
       run: python setup.py sdist bdist_wheel
     - name: Publish package
-      uses: pypa/gh-action-pypi-publish@master
+      uses: pypa/gh-action-pypi-publish@release/v1
       with:
         user: __token__
         password: ${{ secrets.pypi_password }}
diff --git a/.github/workflows/python-test.yml b/.github/workflows/python-test.yml
index 802028c4..b781e118 100644
--- a/.github/workflows/python-test.yml
+++ b/.github/workflows/python-test.yml
@@ -14,12 +14,12 @@ jobs:
   format:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
 
-    - name: Set up Python 3.10
-      uses: actions/setup-python@v4
+    - name: Set up Python 3.12
+      uses: actions/setup-python@v5
       with:
-        python-version: "3.10"
+        python-version: "3.12"
 
     - name: Install dependencies
       run: pip install tox
@@ -32,12 +32,12 @@ jobs:
     strategy:
       max-parallel: 4
       matrix:
-        python-version: ["3.8", "3.9", "3.10", "3.11"]
+        python-version: ["3.12"]
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
 
     - name: Set up Python ${{ matrix.python-version }}
-      uses: actions/setup-python@v4
+      uses: actions/setup-python@v5
       with:
         python-version: ${{ matrix.python-version }}
 
@@ -52,26 +52,27 @@ jobs:
     - name: Prepare artifacts
       run: mkdir .coverage-data && mv .coverage.* .coverage-data/
 
-    - uses: actions/upload-artifact@master
+    - uses: actions/upload-artifact@v4
       with:
         name: coverage-data-${{ matrix.python-version }}
         path: .coverage-data/
+        include-hidden-files: true
 
   coverage:
     runs-on: ubuntu-latest
     needs: [test]
     steps:
-    - uses: actions/checkout@v3
-    - uses: actions/download-artifact@master
+    - uses: actions/checkout@v4
+    - uses: actions/download-artifact@v4
       with:
         pattern: coverage-data-*
         path: .
         merge-multiple: true
 
-    - name: Set up Python 3.10
-      uses: actions/setup-python@v4
+    - name: Set up Python 3.12
+      uses: actions/setup-python@v5
       with:
-        python-version: "3.10"
+        python-version: "3.12"
 
     - name: Install dependencies
       run: |
diff --git a/CHANGES.md b/CHANGES.md
index 2d051192..0e856d6b 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -1,3 +1,14 @@
+26.9.28
+-------
+- Add Python 3.12 support and drop Python 3.6-3.11 (`python_requires >= 3.12`).
+- Import `RAISE` from `marshmallow` instead of `marshmallow.utils`.
+- Require `marshmallow>=3.13`: deserialization fails on 3.10-3.12.
+- Cap `marshmallow<4`: 4.x removes APIs used by `helpers.Discriminator`.
+- Install setuptools explicitly for release builds (Python 3.12 ships without it).
+- Update test tooling for Python 3.12 (pytest, pytest-cov, flake8, mypy).
+- Pin `pypi-publish` and artifact actions instead of tracking `@master`.
+- Fix timing flake in `test_auto_refresh`.
+
 23.6.29
 --------
 - Regenerate code with latest RAML specifications, bringing the SDK up to date
diff --git a/Makefile b/Makefile
index dc8f6875..b2777f47 100644
--- a/Makefile
+++ b/Makefile
@@ -31,7 +31,7 @@ format:
 	black src/ tests/
 
 release:
-	pip install twine wheel
+	pip install setuptools twine wheel
 	rm -rf build/* dist/*
 	python setup.py sdist bdist_wheel
 	twine upload dist/*
diff --git a/README.rst b/README.rst
index 073ef3b3..323e2b4e 100644
--- a/README.rst
+++ b/README.rst
@@ -18,7 +18,7 @@ Python SDK for Commercetools
 ============================
 
 This is an unofficial Python SDK for the Commercetools platform. It only
-supports Python 3.6+ and uses type annotation for an improved development
+supports Python 3.12+ and uses type annotation for an improved development
 experience.
 
 The API is generated using the commercetools api RAML file and uses
diff --git a/docs/index.rst b/docs/index.rst
index cd0bedad..daa03d95 100644
--- a/docs/index.rst
+++ b/docs/index.rst
@@ -2,7 +2,7 @@ Commercetools Python SDK
 ========================
 
 This is an unofficial Python SDK for the Commercetools platform. It only
-supports Python 3.6+ and uses type annotation for an improved development
+supports Python 3.12+ and uses type annotation for an improved development
 experience.
 
 The API is mostly generated using the commercetools api RAML file and uses the
diff --git a/mypy.ini b/mypy.ini
index 88ed9fd7..77d5b5b7 100644
--- a/mypy.ini
+++ b/mypy.ini
@@ -1,6 +1,6 @@
 [mypy]
 ignore_missing_imports = True
-python_version = 3.6
+python_version = 3.12
 warn_unused_configs = True
 mypy_path = src
 check_untyped_defs = True
diff --git a/setup.py b/setup.py
index f1a8a499..c616b46a 100644
--- a/setup.py
+++ b/setup.py
@@ -7,7 +7,9 @@
     "pytz",
     "requests-oauthlib>=1.0.0",
     "requests_mock>=1.8.0",
-    "marshmallow>=3.10.0",
+    # marshmallow 4 drops `default=`, `Schema(context=)` and `Field.fail()`, all
+    # used by helpers.Discriminator; hold at 3.x until that is ported.
+    "marshmallow>=3.13.0,<4",
     "marshmallow-enum>=1.5.1",
     "WebOb>=1.8.0",
     "Werkzeug>=0.15.2",
@@ -25,15 +27,14 @@
     "mock==4.0.3",
     "pretend==1.0.9",
     "coverage[toml]>=6.2",
-    "pytest-cov==3.0.0",
-    "pytest==7.0.1",
+    "pytest-cov==7.1.0",
+    "pytest==9.1.1",
     # Linting
     "isort==5.10.1",
-    "flake8==4.0.1",
-    "flake8-blind-except==0.2.0",
-    "flake8-debugger==4.0.0",
-    "flake8-imports==0.1.1",
-    "mypy==0.931",
+    "flake8==7.4.1",
+    "flake8-blind-except==0.2.1",
+    "flake8-debugger==4.1.2",
+    "mypy==2.3.1",
 ]
 
 
@@ -44,12 +45,13 @@
 
 setup(
     name="commercetools",
-    version="2023.6.29",
+    version="2026.9.28",
     description="SDK for Commercetools",
     long_description=long_description,
     author="Lab Digital B.V.",
     author_email="opensource@labdigital.nl",
     url="https://github.com/labd/commercetools-python-sdk",
+    python_requires=">=3.12",
     install_requires=install_requires,
     tests_require=tests_require,
     extras_require={
@@ -65,10 +67,7 @@
         "Development Status :: 5 - Production/Stable",
         "License :: OSI Approved :: MIT License",
         "Programming Language :: Python :: 3",
-        "Programming Language :: Python :: 3.8",
-        "Programming Language :: Python :: 3.9",
-        "Programming Language :: Python :: 3.10",
-        "Programming Language :: Python :: 3.10",
+        "Programming Language :: Python :: 3.12",
         "Programming Language :: Python :: Implementation :: CPython",
     ],
     zip_safe=False,
diff --git a/src/commercetools/helpers.py b/src/commercetools/helpers.py
index 6655fb3c..fdd08f58 100644
--- a/src/commercetools/helpers.py
+++ b/src/commercetools/helpers.py
@@ -2,14 +2,14 @@
 import inspect
 import typing
 
-from marshmallow import Schema, class_registry, fields, missing, post_dump
+from marshmallow import RAISE, Schema, class_registry, fields, missing, post_dump
 from marshmallow.exceptions import (
     RegistryError,
     StringNotCollectionError,
     ValidationError,
 )
 from marshmallow.fields import Field, Nested
-from marshmallow.utils import RAISE, is_collection
+from marshmallow.utils import is_collection
 from marshmallow.utils import missing as missing_
 
 from commercetools.exceptions import CommercetoolsError
diff --git a/src/commercetools/version.py b/src/commercetools/version.py
index 70f7a685..7522a125 100644
--- a/src/commercetools/version.py
+++ b/src/commercetools/version.py
@@ -1 +1 @@
-__version__ = "2023.6.29"
+__version__ = "2026.9.28"
diff --git a/tests/platform/test_client.py b/tests/platform/test_client.py
index a0541d95..272bf593 100644
--- a/tests/platform/test_client.py
+++ b/tests/platform/test_client.py
@@ -39,7 +39,8 @@ def test_auto_refresh(commercetools_api):
         token_url="https://auth.europe-west1.gcp.commercetools.com/oauth/token",
     )
     client.products.query()
-    time.sleep(1)
+    # oauthlib stores an integer expires_at, so wait past the 1s expiry with margin
+    time.sleep(2)
     client.products.query()
     client.products.query()
 
diff --git a/tox.ini b/tox.ini
index 65240019..d2b10c75 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,20 +1,16 @@
 [tox]
-envlist = py36,py37,py38,py39,py310
+envlist = py312
 
 [gh-actions]
 python =
-    3.6: py36
-    3.7: py37
-    3.8: py38
-    3.9: py39
-    3.10: py310
+    3.12: py312
 
 [testenv]
 commands = coverage run --source commercetools --parallel -m pytest {posargs}
 extras = test
 
 [testenv:coverage-report]
-basepython = python3.10
+basepython = python3.12
 deps = coverage[toml]
 skip_install = true
 commands =
@@ -23,7 +19,7 @@ commands =
     coverage report
 
 [testenv:format]
-basepython = python3.10
+basepython = python3.12
 deps =
     black==22.6.0
     isort[toml]==5.10.1