diff --git a/.cz.yaml b/.cz.yaml
index 48d7b00..f069e4b 100644
--- a/.cz.yaml
+++ b/.cz.yaml
@@ -4,7 +4,7 @@ commitizen:
   name: cz_conventional_commits
   tag_format: v$version
   update_changelog_on_bump: true
-  version: 3.0.2
+  version: 4.0.0
   version_files:
   - README.md
   version_scheme: semver
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 9b90c6e..fd917b6 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,13 @@
+## v4.0.0 (2024-06-18)
+
+### BREAKING CHANGE
+
+- drop python-version input
+
+### Refactor
+
+- **tox-docker**: use coatldev/six:latest container (#31)
+
 ## v3.0.2 (2024-05-20)
 
 ### Refactor
diff --git a/README.md b/README.md
index f725600..a680175 100644
--- a/README.md
+++ b/README.md
@@ -60,7 +60,7 @@ on:
 
 jobs:
   pip-compile-upgrade:
-    uses: coatl-dev/workflows/.github/workflows/pip-compile-upgrade.yml@v3.0.2
+    uses: coatl-dev/workflows/.github/workflows/pip-compile-upgrade.yml@v4.0.0
     with:
       path: requirements.txt
     secrets:
@@ -109,7 +109,7 @@ on:
 
 jobs:
   pre-commit-autoupdate:
-    uses: coatl-dev/workflows/.github/workflows/pre-commit-autoupdate.yml@v3.0.2
+    uses: coatl-dev/workflows/.github/workflows/pre-commit-autoupdate.yml@v4.0.0
     with:
       skip-repos: 'flake8'
     secrets:
@@ -134,7 +134,7 @@ to install Python and invoke [`pre-commit`].
 ```yaml
 jobs:
   main:
-    uses: coatl-dev/workflows/.github/workflows/pre-commit.yml@v3.0.2
+    uses: coatl-dev/workflows/.github/workflows/pre-commit.yml@v4.0.0
     with:
       skip-hooks: 'pylint'
 ```
@@ -148,7 +148,7 @@ This workflow will install Python and invoke `pylint` to analyze your code.
 ```yaml
 jobs:
   main:
-    uses: coatl-dev/workflows/.github/workflows/pylint.yml@v3.0.2
+    uses: coatl-dev/workflows/.github/workflows/pylint.yml@v4.0.0
 ```
 
 ### .github/workflows/pypi-upload.yml
@@ -178,7 +178,7 @@ Secrets:
 ```yaml
 jobs:
   main:
-    uses: coatl-dev/workflows/.github/workflows/pypi-upload.yml@v3.0.2
+    uses: coatl-dev/workflows/.github/workflows/pypi-upload.yml@v4.0.0
     with:
       python-version: '3.11'
     secrets:
@@ -206,7 +206,7 @@ requires =
 ```yaml
 jobs:
   main:
-    uses: coatl-dev/workflows/.github/workflows/tox-docker.yml@v3.0.2
+    uses: coatl-dev/workflows/.github/workflows/tox-docker.yml@v4.0.0
 ```
 
 ### .github/workflows/tox-envs.yml
@@ -238,7 +238,7 @@ requires =
 ```yaml
 jobs:
   main:
-    uses: coatl-dev/workflows/.github/workflows/tox-envs.yml@v3.0.2
+    uses: coatl-dev/workflows/.github/workflows/tox-envs.yml@v4.0.0
     with:
       python-versions: '["3.7", "3.8", "3.9", "3.10", "3.11", "3.12"]'
 ```
@@ -276,7 +276,7 @@ and on your workflow:
 ```yaml
 jobs:
   main:
-    uses: coatl-dev/workflows/.github/workflows/tox-gh.yml@v3.0.2
+    uses: coatl-dev/workflows/.github/workflows/tox-gh.yml@v4.0.0
     with:
       python-versions: '["3.7", "3.8", "3.9", "3.10", "3.11", "3.12"]'
 ```
@@ -291,7 +291,7 @@ This workflow will install Python and invoke `tox` to run all envs found in
 ```yaml
 jobs:
   main:
-    uses: coatl-dev/workflows/.github/workflows/tox.yml@v3.0.2
+    uses: coatl-dev/workflows/.github/workflows/tox.yml@v4.0.0
 ```
 
 [`actions/setup-python`]: https://github.com/actions/setup-python