diff --git a/.github/workflows/common.yaml b/.github/workflows/common.yaml
index 8be2ff2..3783ec3 100644
--- a/.github/workflows/common.yaml
+++ b/.github/workflows/common.yaml
@@ -3,7 +3,9 @@ on:
   workflow_dispatch:
   push:
     branches: ["main"]
+    paths: ["common/**", ".github/workflows/common.yaml"]
   pull_request:
+    paths: ["common/**", ".github/workflows/common.yaml"]
 
 concurrency:
   group: ${{ github.workflow }}-${{ github.ref }}
diff --git a/.github/workflows/pyproject_fmt_build.yaml b/.github/workflows/pyproject_fmt_build.yaml
index 2dc8191..11c3873 100644
--- a/.github/workflows/pyproject_fmt_build.yaml
+++ b/.github/workflows/pyproject_fmt_build.yaml
@@ -14,7 +14,9 @@ on:
           - major
   push:
     branches: ["main"]
+    paths: ["common/**", "pyproject-fmt/**", ".github/workflows/pyproject_fmt_build.yaml"]
   pull_request:
+    paths: ["common/**", "pyproject-fmt/**", ".github/workflows/pyproject_fmt_build.yaml"]
   schedule:
     - cron: "0 8 * * *"
 
diff --git a/.github/workflows/pyproject_fmt_test.yaml b/.github/workflows/pyproject_fmt_test.yaml
index 1a923ee..13075c1 100644
--- a/.github/workflows/pyproject_fmt_test.yaml
+++ b/.github/workflows/pyproject_fmt_test.yaml
@@ -3,7 +3,9 @@ on:
   workflow_dispatch:
   push:
     branches: ["main"]
+    paths: ["common/**", "pyproject-fmt/**", ".github/workflows/pyproject_fmt_test.yaml"]
   pull_request:
+    paths: ["common/**", "pyproject-fmt/**", ".github/workflows/pyproject_fmt_test.yaml"]
 
 concurrency:
   group: ${{ github.workflow }}-${{ github.ref }}
diff --git a/.github/workflows/tox_toml_fmt_build.yaml b/.github/workflows/tox_toml_fmt_build.yaml
new file mode 100644
index 0000000..94c987d
--- /dev/null
+++ b/.github/workflows/tox_toml_fmt_build.yaml
@@ -0,0 +1,245 @@
+name: Build tox-toml-fmt
+on:
+  workflow_dispatch:
+    inputs:
+      release:
+        description: "Cut a release (select semver bump)?"
+        required: true
+        default: "no"
+        type: choice
+        options:
+          - "no"
+          - patch
+          - minor
+          - major
+  push:
+    branches: ["main"]
+    paths: ["common/**", "tox-toml-fmt/**", ".github/workflows/tox_toml_fmt_build.yaml"]
+  pull_request:
+    paths: ["common/**", "tox-toml-fmt/**", ".github/workflows/tox_toml_fmt_build.yaml"]
+  schedule:
+    - cron: "0 8 * * *"
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: ${{ github.event.inputs.release == 'no' || github.event.inputs.release == null }}
+
+permissions:
+  contents: read
+
+jobs:
+  bump:
+    runs-on: ubuntu-latest
+    permissions:
+      pull-requests: read
+    outputs:
+      version: ${{ steps.get-version.outputs.version }}
+      changelog: ${{ steps.get-version.outputs.changelog }}
+    steps:
+      - uses: actions-rust-lang/setup-rust-toolchain@v1
+      - name: Install cargo-edit from crates.io
+        uses: baptiste0928/cargo-install@v3
+        with:
+          crate: cargo-edit
+      - uses: actions/checkout@v4
+      - name: Bump version
+        run: cargo set-version -p tox-toml-fmt --bump '${{ github.event.inputs.release == 'no' || github.event.inputs.release == null && 'patch' || github.event.inputs.release }}'
+      - name: Install the latest version of uv
+        uses: astral-sh/setup-uv@v3
+        with:
+          enable-cache: true
+          cache-dependency-glob: "tasks/changelog.py"
+      - name: Generate changelog
+        id: get-version
+        run: uv run tasks/changelog.py tox-toml-fmt "${{ github.event.number }}" "${{ github.event.pull_request.base.sha }}"
+        env:
+          GITHUB_TOKEN: ${{secrets.GITHUB_TOKEN}}
+      - uses: actions/setup-python@v5
+        with:
+          python-version: "3.12"
+      - uses: pre-commit/action@v3.0.1
+        continue-on-error: true
+      - name: Show changes to the repository
+        run: git diff HEAD -u
+      - name: Store the patched distribution
+        uses: actions/upload-artifact@v4
+        with:
+          name: source
+          path: .
+          compression-level: 9
+          retention-days: 1
+          if-no-files-found: "error"
+
+  linux:
+    needs: [bump]
+    runs-on: ${{ matrix.platform.runner }}
+    strategy:
+      fail-fast: false
+      matrix:
+        platform:
+          - runner: ubuntu-latest
+            target: x86_64
+            interpreter: "3.8 pypy3.8 pypy3.9 pypy3.10"
+          - runner: ubuntu-latest
+            target: x86
+          - runner: ubuntu-latest
+            target: x86_64-unknown-linux-musl
+            manylinux: musllinux_1_1
+          - runner: ubuntu-latest
+            target: i686-unknown-linux-musl
+            manylinux: musllinux_1_1
+          - runner: ubuntu-latest
+            target: aarch64
+          - runner: ubuntu-latest
+            target: armv7
+          - runner: ubuntu-latest
+            target: s390x
+          - runner: ubuntu-latest
+            target: ppc64le
+    steps:
+      - name: Download the code
+        uses: actions/download-artifact@v4
+        with:
+          name: source
+      - name: Build wheels
+        uses: PyO3/maturin-action@ea5bac0f1ccd0ab11c805e2b804bfcb65dac2eab
+
+        with:
+          target: ${{ matrix.platform.target }}
+          args: -m tox-toml-fmt/Cargo.toml --release --out dist --interpreter ${{ matrix.platform.interpreter || '3.8' }} --target-dir target
+          sccache: "true"
+          manylinux: ${{ matrix.platform.manylinux || 'auto' }}
+      - name: Upload wheels
+        uses: actions/upload-artifact@v4
+        with:
+          name: wheels-linux-${{ matrix.platform.target }}
+          path: dist
+
+  windows:
+    needs: [bump]
+    runs-on: ${{ matrix.platform.runner }}
+    strategy:
+      matrix:
+        platform:
+          - runner: windows-latest
+            target: x64
+          - runner: windows-latest
+            target: x86
+    steps:
+      - name: Download the code
+        uses: actions/download-artifact@v4
+        with:
+          name: source
+      - name: Build wheels
+        uses: PyO3/maturin-action@ea5bac0f1ccd0ab11c805e2b804bfcb65dac2eab
+
+        with:
+          target: ${{ matrix.platform.target }}
+          args: -m tox-toml-fmt/Cargo.toml --release --out dist --interpreter ${{ matrix.platform.interpreter || '3.8' }} --target-dir target
+          sccache: "true"
+      - name: Upload wheels
+        uses: actions/upload-artifact@v4
+        with:
+          name: wheels-windows-${{ matrix.platform.target }}
+          path: dist
+
+  macos:
+    needs: [bump]
+    runs-on: ${{ matrix.platform.runner }}
+    strategy:
+      matrix:
+        platform:
+          - runner: macos-latest
+            target: x86_64
+          - runner: macos-14
+            target: aarch64
+    steps:
+      - name: Download the code
+        uses: actions/download-artifact@v4
+        with:
+          name: source
+      - name: Build wheels
+        uses: PyO3/maturin-action@ea5bac0f1ccd0ab11c805e2b804bfcb65dac2eab
+
+        with:
+          target: ${{ matrix.platform.target }}
+          args: -m tox-toml-fmt/Cargo.toml --release --out dist --interpreter "3.8 pypy3.8 pypy3.9 pypy3.10" --target-dir target
+          sccache: "true"
+      - name: Upload wheels
+        uses: actions/upload-artifact@v4
+        with:
+          name: wheels-macos-${{ matrix.platform.target }}
+          path: dist
+
+  sdist:
+    needs: [bump]
+    runs-on: ubuntu-latest
+    steps:
+      - name: Download the code
+        uses: actions/download-artifact@v4
+        with:
+          name: source
+      - name: Build sdist
+        uses: PyO3/maturin-action@ea5bac0f1ccd0ab11c805e2b804bfcb65dac2eab
+
+        with:
+          command: sdist
+          args: -m tox-toml-fmt/Cargo.toml --out dist
+      - name: Upload sdist
+        uses: actions/upload-artifact@v4
+        with:
+          name: wheels-sdist
+          path: dist
+
+  release:
+    name: Release
+    runs-on: ubuntu-latest
+    environment:
+      name: release
+      url: https://pypi.org/project/tox-toml-fmt/${{ needs.bump.outputs.version }}
+    permissions:
+      id-token: write
+      contents: write
+    if: github.event.inputs.release != 'no' && github.event.inputs.release != null && github.ref == 'refs/heads/main'
+    needs: [bump, sdist, linux, macos, windows]
+    steps:
+      - uses: actions/checkout@v4
+      - name: Download source
+        uses: actions/download-artifact@v4
+        with:
+          name: source
+          path: .
+      - name: Show changes to the repository
+        run: git diff HEAD -u
+      - name: Commit changes
+        run: |
+          git config --global user.name 'Bernat Gabor'
+          git config --global user.email 'gaborbernat@users.noreply.github.com'
+          git commit -am "Release tox-toml-fmt ${{needs.bump.outputs.version}}"
+      - name: Tag release
+        run: git tag tox-toml-fmt/${{needs.bump.outputs.version}}
+      - name: Download wheels
+        uses: actions/download-artifact@v4
+        with:
+          pattern: wheels-*
+          path: dist
+          merge-multiple: "true"
+      - name: Show wheels
+        run: ls -lth dist
+      - name: Publish to PyPI
+        uses: PyO3/maturin-action@ea5bac0f1ccd0ab11c805e2b804bfcb65dac2eab
+        with:
+          command: upload
+          args: --non-interactive --skip-existing dist/*
+      - name: Push release commit+tag and create GitHub release
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        run: |
+          git push
+          git push --tags
+          gh release create "tox-toml-fmt/${{needs.bump.outputs.version}}" \
+              --title="tox-toml-fmt/${{needs.bump.outputs.version}}" --verify-tag \
+            --notes "$(cat << 'EOM'
+          ${{ needs.bump.outputs.changelog }}
+          EOM
+          )"
diff --git a/.github/workflows/tox_toml_fmt_test.yaml b/.github/workflows/tox_toml_fmt_test.yaml
new file mode 100644
index 0000000..d49f42f
--- /dev/null
+++ b/.github/workflows/tox_toml_fmt_test.yaml
@@ -0,0 +1,130 @@
+name: Test tox-toml-fmt
+on:
+  workflow_dispatch:
+  push:
+    branches: ["main"]
+    paths: ["common/**", "tox-toml-fmt/**", ".github/workflows/tox_toml_fmt_test.yaml"]
+  pull_request:
+    paths: ["common/**", "tox-toml-fmt/**", ".github/workflows/tox_toml_fmt_test.yaml"]
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  rust-lint:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions-rust-lang/setup-rust-toolchain@v1
+        with:
+          components: clippy
+      - name: Lint rust code with clippy
+        run: cargo clippy -p tox-toml-fmt --all-targets -- -D warnings
+
+  rust-fmt:
+    runs-on: ubuntu-latest
+    defaults:
+      run:
+        working-directory: tox-toml-fmt
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions-rust-lang/setup-rust-toolchain@v1
+        with:
+          components: rustfmt
+      - name: Rust formatting check
+        run: cargo fmt -p tox-toml-fmt --check
+
+  rust-build:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions-rust-lang/setup-rust-toolchain@v1
+      - name: Build library
+        run: cargo build -p tox-toml-fmt
+
+  rust-test:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions-rust-lang/setup-rust-toolchain@v1
+      - run: cargo test -p tox-toml-fmt
+
+  py-test:
+    name: test ${{ matrix.py }} ${{ matrix.os }}
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        py:
+          - "3.13"
+          - "3.12"
+          - "3.11"
+          - "3.10"
+          - "3.9"
+        os:
+          - ubuntu-latest
+          - windows-latest
+          - macos-latest
+    defaults:
+      run:
+        working-directory: tox-toml-fmt
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+      - name: Install the latest version of uv
+        uses: astral-sh/setup-uv@v3
+        with:
+          enable-cache: true
+          cache-dependency-glob: "pyproject.toml"
+      - name: Install tox
+        run: uv tool install --python-preference only-managed --python 3.13 tox --with tox-uv
+      - name: Install Python
+        if: matrix.py != '3.13'
+        run: uv python install --python-preference only-managed ${{ matrix.env }}
+      - uses: moonrepo/setup-rust@v1
+        with:
+          cache-base: main
+          bins: cargo-tarpaulin
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Setup test suite
+        run: tox run -vv --notest --skip-missing-interpreters false -e ${{ matrix.py }}
+      - name: Run test suite
+        run: tox run  --skip-pkg-install -e ${{ matrix.py }}
+        env:
+          PYTEST_ADDOPTS: "-vv --durations=20"
+
+  py-check:
+    name: tox env ${{ matrix.env }}
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        env:
+          - type
+          - dev
+          - pkg_meta
+    defaults:
+      run:
+        working-directory: tox-toml-fmt
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+      - name: Install the latest version of uv
+        uses: astral-sh/setup-uv@v3
+        with:
+          enable-cache: true
+          cache-dependency-glob: "pyproject.toml"
+          github-token: ${{ secrets.GITHUB_TOKEN }}
+      - name: Install tox
+        run: uv tool install --python-preference only-managed --python 3.13 tox --with tox-uv
+      - name: Setup test suite
+        run: tox run -vv --notest --skip-missing-interpreters false -e ${{ matrix.env }}
+      - name: Run test suite
+        run: tox run --skip-pkg-install -e ${{ matrix.env }}
+        env:
+          PYTEST_ADDOPTS: "-vv --durations=20"
diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 9b6eff4..da3fba3 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -14,8 +14,12 @@ repos:
     hooks:
       - id: codespell
         additional_dependencies: ["tomli>=2.0.1"]
+  - repo: https://github.com/abravalheri/validate-pyproject
+    rev: v0.22
+    hooks:
+      - id: validate-pyproject
   - repo: https://github.com/tox-dev/pyproject-fmt
-    rev: "v2.4.3"
+    rev: "v2.5.0"
     hooks:
       - id: pyproject-fmt
   - repo: https://github.com/astral-sh/ruff-pre-commit
diff --git a/Cargo.lock b/Cargo.lock
index a737793..cbdf294 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -818,6 +818,18 @@ dependencies = [
  "winnow",
 ]
 
+[[package]]
+name = "tox-toml-fmt"
+version = "2.5.0"
+dependencies = [
+ "common",
+ "indoc",
+ "lexical-sort",
+ "pyo3",
+ "regex",
+ "rstest",
+]
+
 [[package]]
 name = "tracing"
 version = "0.1.40"
diff --git a/Cargo.toml b/Cargo.toml
index 1ef9677..f3c5b9e 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -2,6 +2,7 @@
 members = [
     "common",
     "pyproject-fmt",
+    "tox-toml-fmt"
 ]
 resolver = "2"
 
diff --git a/README.md b/README.md
index 462a44e..494716f 100644
--- a/README.md
+++ b/README.md
@@ -1,9 +1,6 @@
 # Python TOML formatters
 
-This project includes the:
+This project includes the following TOML formatters for the Python ecosystem:
 
-- pyproject-fmt,
-- ruff-toml-fmt,
-- tox-toml-fmt,
-
-projects formatting your TOML files in the Python world.
+- [`pyproject-fmt`](./pyproject-fmt),
+- [`tox-toml-fmt`](./tox-toml-fmt).
diff --git a/pyproject-fmt/docs/conf.py b/pyproject-fmt/docs/conf.py
index 6042ced..e2b7ee5 100644
--- a/pyproject-fmt/docs/conf.py
+++ b/pyproject-fmt/docs/conf.py
@@ -22,6 +22,7 @@
     "sphinx.ext.intersphinx",
     "sphinx_argparse_cli",
     "sphinx_autodoc_typehints",
+    "sphinx_inline_tabs",
     "sphinx_copybutton",
 ]
 
@@ -34,8 +35,7 @@
 }
 
 extlinks = {
-    "issue": (f"https://github.com/{company}/{name}/issues/%s", "#%s"),
-    "user": ("https://github.com/%s", "@%s"),
+    "pypi": ("https://pypi.org/project/%s", "%s"),
     "gh": ("https://github.com/%s", "%s"),
 }
 intersphinx_mapping = {"python": ("https://docs.python.org/3", None)}
diff --git a/pyproject-fmt/docs/index.rst b/pyproject-fmt/docs/index.rst
index 78c395b..6c0bb15 100644
--- a/pyproject-fmt/docs/index.rst
+++ b/pyproject-fmt/docs/index.rst
@@ -1,16 +1,15 @@
 pyproject-fmt
 =============
 
-Apply a consistent format to your ``pyproject.toml`` file with comment support.
-See `changelog here <https://github.com/tox-dev/pyproject-fmt/releases>`_.
+Apply a consistent format to your ``pyproject.toml`` file with comment support. See
+`changelog here <https://github.com/tox-dev/toml-fmt/blob/main/pyproject-fmt/CHANGELOG.md>`_.
 
 
 Philosophy
 ----------
-This tool aims to be an *opinionated formatter*, with similar objectives to
-`black <https://github.com/psf/black>`_. This means it deliberately does not support
-a wide variety of configuration settings. In return, you get consistency, predictability,
-and smaller diffs.
+This tool aims to be an *opinionated formatter*, with similar objectives to `black <https://github.com/psf/black>`_.
+This means it deliberately does not support a wide variety of configuration settings. In return, you get consistency,
+predictability, and smaller diffs.
 
 Use
 ---
@@ -18,11 +17,39 @@ Use
 Via ``CLI``
 ~~~~~~~~~~~
 
-Use `pipx <https://pipx.pypa.io/stable/installation/>`_ to install the project:
+:pypi:`pyproject-fmt` is a CLI tool that needs a Python interpreter (version 3.7 or higher) to run. We recommend either
+:pypi:`pipx` or :pypi:`uv` to install tox into an isolated environment. This has the added benefit that later you'll
+be able to upgrade tox without affecting other parts of the system. We provide method for ``pip`` too here but we
+discourage that path if you can:
 
-.. code-block:: shell
+.. tab:: uv
 
-   pipx install pyproject-fmt
+    .. code-block:: bash
+
+        # install uv per https://docs.astral.sh/uv/#getting-started
+        uv tool install pyproject-fmt
+        pyproject-fmt --help
+
+
+.. tab:: pipx
+
+    .. code-block:: bash
+
+        python -m pip install pipx-in-pipx --user
+        pipx install pyproject-fmt
+        pyproject-fmt --help
+
+.. tab:: pip
+
+    .. code-block:: bash
+
+        python -m pip install --user pyproject-fmt
+        pyproject-fmt --help
+
+    You can install it within the global Python interpreter itself (perhaps as a user package via the
+    ``--user`` flag). Be cautious if you are using a Python installation that is managed by your operating system or
+    another package manager. ``pip`` might not coordinate with those tools, and may leave your system in an inconsistent
+    state. Note, if you go down this path you need to ensure pip is new enough per the subsections below
 
 
 Via ``pre-commit`` hook
@@ -33,7 +60,7 @@ See :gh:`pre-commit/pre-commit` for instructions, sample ``.pre-commit-config.ya
 .. code-block:: yaml
 
     - repo: https://github.com/tox-dev/pyproject-fmt
-      rev: "2.0.4"
+      rev: "v2.5.0"
       hooks:
         - id: pyproject-fmt
 
diff --git a/pyproject-fmt/pyproject.toml b/pyproject-fmt/pyproject.toml
index b9f5468..410238f 100644
--- a/pyproject-fmt/pyproject.toml
+++ b/pyproject-fmt/pyproject.toml
@@ -40,6 +40,42 @@ urls.Documentation = "https://github.com/tox-dev/toml-fmt/"
 urls."Source Code" = "https://github.com/tox-dev/toml-fmt"
 scripts.pyproject-fmt = "pyproject_fmt.__main__:runner"
 
+[dependency-groups]
+dev = [
+  { include-group = "docs" },
+  { include-group = "fix" },
+  { include-group = "test" },
+  { include-group = "type" },
+]
+test = [
+  "covdefaults>=2.3",
+  "pytest>=8.3.2",
+  "pytest-cov>=5",
+  "pytest-mock>=3.14",
+]
+type = [
+  "mypy==1.11.2",
+  "types-cachetools>=5.5.0.20240820",
+  "types-chardet>=5.0.4.6",
+  { include-group = "test" },
+]
+docs = [
+  "furo>=2024.8.6",
+  "sphinx>=8.0.2",
+  "sphinx-argparse-cli>=1.18.2",
+  "sphinx-autodoc-typehints>=2.4.4",
+  "sphinx-copybutton>=0.5.2",
+  "sphinx-inline-tabs>=2023.4.21",
+]
+fix = [
+  "pre-commit-uv>=4.1.3",
+]
+pkg-meta = [
+  "check-wheel-contents>=0.6",
+  "twine>=5.1.1",
+  "uv>=0.4.17",
+]
+
 [tool.maturin]
 bindings = "pyo3"
 manifest-path = "Cargo.toml"
@@ -85,43 +121,3 @@ run.plugins = [
 [tool.mypy]
 show_error_codes = true
 strict = true
-
-[dependency-groups]
-dev = [
-  { include-group = "docs" },
-  { include-group = "fix" },
-  { include-group = "tasks" },
-  { include-group = "test" },
-  { include-group = "type" },
-]
-docs = [
-  "furo>=2024.8.6",
-  "sphinx>=8.0.2",
-  "sphinx-argparse-cli>=1.18.2",
-  "sphinx-autodoc-typehints>=2.4.4",
-  "sphinx-copybutton>=0.5.2",
-]
-fix = [
-  "pre-commit-uv>=4.1.3",
-]
-pkg-meta = [
-  "check-wheel-contents>=0.6",
-  "twine>=5.1.1",
-  "uv>=0.4.17",
-]
-tasks = [
-  "gitpython>=3.1.43",
-  "pygithub>=2.4",
-]
-test = [
-  "covdefaults>=2.3",
-  "pytest>=8.3.2",
-  "pytest-cov>=5",
-  "pytest-mock>=3.14",
-]
-type = [
-  "mypy==1.11.2",
-  "types-cachetools>=5.5.0.20240820",
-  "types-chardet>=5.0.4.6",
-  { include-group = "test" },
-]
diff --git a/pyproject-fmt/tests/test_main.py b/pyproject-fmt/tests/test_main.py
index b26b262..a0f5b92 100644
--- a/pyproject-fmt/tests/test_main.py
+++ b/pyproject-fmt/tests/test_main.py
@@ -19,6 +19,7 @@
         True,
         False,
     ],
+    ids=("in_place", "print"),
 )
 @pytest.mark.parametrize(
     "check",
@@ -26,6 +27,7 @@
         True,
         False,
     ],
+    ids=["check", "no_check"],
 )
 @pytest.mark.parametrize(
     "cwd",
@@ -33,20 +35,23 @@
         True,
         False,
     ],
+    ids=["cwd", "absolute"],
 )
 @pytest.mark.parametrize(
     ("start", "outcome", "output"),
     [
-        (
+        pytest.param(
             '[build-system]\nrequires = [\n  "hatchling>=0.14",\n]\n',
             '[build-system]\nrequires = [\n  "hatchling>=0.14",\n]\n',
             "no change for {0}\n",
+            id="formatted",
         ),
-        (
+        pytest.param(
             '[build-system]\nrequires = ["hatchling>=0.14.0"]',
             '[build-system]\nrequires = [ "hatchling>=0.14" ]\n',
             "--- {0}\n\n+++ {0}\n\n@@ -1,2 +1,2 @@\n\n [build-system]\n-requires = "
             '["hatchling>=0.14.0"]\n+requires = [ "hatchling>=0.14" ]\n',
+            id="format",
         ),
     ],
 )
diff --git a/tasks/changelog.py b/tasks/changelog.py
index c5e57d5..86579e5 100644
--- a/tasks/changelog.py
+++ b/tasks/changelog.py
@@ -78,7 +78,7 @@ def run() -> None:
 
 def parse_cli() -> Options:
     parser = ArgumentParser()
-    parser.add_argument("project", choices=["pyproject-fmt"])
+    parser.add_argument("project", choices=["pyproject-fmt", "tox-toml-fmt"])
     parser.add_argument("pr", type=lambda s: int(s) if s else None)
     parser.add_argument("base", type=str)
     options = Options()
diff --git a/tox-toml-fmt/.readthedocs.yaml b/tox-toml-fmt/.readthedocs.yaml
new file mode 100644
index 0000000..cbe9b7a
--- /dev/null
+++ b/tox-toml-fmt/.readthedocs.yaml
@@ -0,0 +1,10 @@
+version: 2
+build:
+  os: ubuntu-lts-latest
+  tools:
+    python: "3.12"
+    rust: "latest"
+  commands:
+    - pip install tox-uv
+    - tox -c tox-toml-fmt/tox.toml run -e docs -vv --notest
+    - tox -c tox-toml-fmt/tox.toml run -e docs --skip-pkg-install --
diff --git a/tox-toml-fmt/CHANGELOG.md b/tox-toml-fmt/CHANGELOG.md
new file mode 100644
index 0000000..e69de29
diff --git a/tox-toml-fmt/Cargo.toml b/tox-toml-fmt/Cargo.toml
new file mode 100644
index 0000000..21f99a2
--- /dev/null
+++ b/tox-toml-fmt/Cargo.toml
@@ -0,0 +1,27 @@
+[package]
+name = "tox-toml-fmt"
+version = "2.5.0"
+description = "Format pyproject.toml files"
+repository = "https://github.com/tox-dev/tox-toml-fmt"
+readme = "README.md"
+license = "MIT"
+edition = "2021"
+
+[lib]
+name = "_lib"
+path = "rust/src/main.rs"
+crate-type = ["cdylib"]
+
+[dependencies]
+common = {path = "../common" }
+regex = { version = "1.11.1" }
+pyo3 = { version = "0.22.5", features = ["abi3-py38"] } # integration with Python
+lexical-sort = { version = "0.3.1" }
+
+[features]
+extension-module = ["pyo3/extension-module"]
+default = ["extension-module"]
+
+[dev-dependencies]
+rstest = { version = "0.23.0" } # parametrized tests
+indoc = { version = "2.0.5" }   # dedented test cases for literal strings
diff --git a/tox-toml-fmt/LICENSE.txt b/tox-toml-fmt/LICENSE.txt
new file mode 100644
index 0000000..3649823
--- /dev/null
+++ b/tox-toml-fmt/LICENSE.txt
@@ -0,0 +1,18 @@
+Permission is hereby granted, free of charge, to any person obtaining a
+copy of this software and associated documentation files (the
+"Software"), to deal in the Software without restriction, including
+without limitation the rights to use, copy, modify, merge, publish,
+distribute, sublicense, and/or sell copies of the Software, and to
+permit persons to whom the Software is furnished to do so, subject to
+the following conditions:
+
+The above copyright notice and this permission notice shall be included
+in all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
+TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
+SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
diff --git a/tox-toml-fmt/README.md b/tox-toml-fmt/README.md
new file mode 100644
index 0000000..2bb977a
--- /dev/null
+++ b/tox-toml-fmt/README.md
@@ -0,0 +1,9 @@
+# tox-toml-fmt
+
+[![PyPI](https://img.shields.io/pypi/v/tox-toml-fmt?style=flat-square)](https://pypi.org/project/tox-toml-fmt)
+[![PyPI - Implementation](https://img.shields.io/pypi/implementation/tox-toml-fmt?style=flat-square)](https://pypi.org/project/tox-toml-fmt)
+[![PyPI - Python Version](https://img.shields.io/pypi/pyversions/tox-toml-fmt?style=flat-square)](https://pypi.org/project/tox-toml-fmt)
+[![Downloads](https://static.pepy.tech/badge/tox-toml-fmt/month)](https://pepy.tech/project/tox-toml-fmt)
+[![PyPI - License](https://img.shields.io/pypi/l/tox-toml-fmt?style=flat-square)](https://opensource.org/licenses/MIT)
+[![Build tox-toml-fmt](https://github.com/tox-dev/toml-fmt/actions/workflows/tox_toml_fmt_build.yaml/badge.svg)](https://github.com/tox-dev/toml-fmt/actions/workflows/tox_toml_fmt_build.yaml)
+[![Test tox-toml-fmt](https://github.com/tox-dev/toml-fmt/actions/workflows/tox_toml_fmt_test.yaml/badge.svg)](https://github.com/tox-dev/toml-fmt/actions/workflows/tox_toml_fmt_test.yaml)
diff --git a/tox-toml-fmt/docs/conf.py b/tox-toml-fmt/docs/conf.py
new file mode 100644
index 0000000..c817925
--- /dev/null
+++ b/tox-toml-fmt/docs/conf.py
@@ -0,0 +1,43 @@
+"""Configuration for documentation build."""  # noqa: INP001
+
+from __future__ import annotations
+
+from datetime import datetime, timezone
+from importlib.metadata import version as metadata_version
+
+company, name = "tox-dev", "tox-toml-fmt"
+ver = metadata_version("tox-toml-fmt")
+release, version = ver, ".".join(ver.split(".")[:2])
+now = datetime.now(tz=timezone.utc)
+project_copyright = f"2022-{now.year}, {company}"
+master_doc, source_suffix = "index", ".rst"
+
+html_theme = "furo"
+html_title, html_last_updated_fmt = name, now.isoformat()
+pygments_style, pygments_dark_style = "sphinx", "monokai"
+
+extensions = [
+    "sphinx.ext.autodoc",
+    "sphinx.ext.extlinks",
+    "sphinx.ext.intersphinx",
+    "sphinx_argparse_cli",
+    "sphinx_autodoc_typehints",
+    "sphinx_inline_tabs",
+    "sphinx_copybutton",
+]
+
+exclude_patterns = ["_build", "changelog/*", "_draft.rst"]
+autoclass_content, autodoc_member_order, autodoc_typehints = "class", "bysource", "none"
+autodoc_default_options = {
+    "member-order": "bysource",
+    "undoc-members": True,
+    "show-inheritance": True,
+}
+
+extlinks = {
+    "pypi": ("https://pypi.org/project/%s", "%s"),
+    "gh": ("https://github.com/%s", "%s"),
+}
+intersphinx_mapping = {"python": ("https://docs.python.org/3", None)}
+nitpicky = True
+nitpick_ignore = []
diff --git a/tox-toml-fmt/docs/index.rst b/tox-toml-fmt/docs/index.rst
new file mode 100644
index 0000000..a9964ee
--- /dev/null
+++ b/tox-toml-fmt/docs/index.rst
@@ -0,0 +1,101 @@
+tox-toml-fmt
+=============
+
+Apply a consistent format to your ``pyproject.toml`` file with comment support. See
+`changelog here <https://github.com/tox-dev/toml-fmt/blob/main/tox-toml-fmt/CHANGELOG.md>`_.
+
+
+Philosophy
+----------
+This tool aims to be an *opinionated formatter*, with similar objectives to `black <https://github.com/psf/black>`_.
+This means it deliberately does not support a wide variety of configuration settings. In return, you get consistency,
+predictability, and smaller diffs.
+
+Use
+---
+
+Via ``CLI``
+~~~~~~~~~~~
+
+:pypi:`tox-toml-fmt` is a CLI tool that needs a Python interpreter (version 3.7 or higher) to run. We recommend either
+:pypi:`pipx` or :pypi:`uv` to install tox into an isolated environment. This has the added benefit that later you'll
+be able to upgrade tox without affecting other parts of the system. We provide method for ``pip`` too here but we
+discourage that path if you can:
+
+.. tab:: uv
+
+    .. code-block:: bash
+
+        # install uv per https://docs.astral.sh/uv/#getting-started
+        uv tool install tox-toml-fmt
+        tox-toml-fmt --help
+
+
+.. tab:: pipx
+
+    .. code-block:: bash
+
+        python -m pip install pipx-in-pipx --user
+        pipx install tox-toml-fmt
+        tox-toml-fmt --help
+
+.. tab:: pip
+
+    .. code-block:: bash
+
+        python -m pip install --user tox-toml-fmt
+        tox-toml-fmt --help
+
+    You can install it within the global Python interpreter itself (perhaps as a user package via the
+    ``--user`` flag). Be cautious if you are using a Python installation that is managed by your operating system or
+    another package manager. ``pip`` might not coordinate with those tools, and may leave your system in an inconsistent
+    state. Note, if you go down this path you need to ensure pip is new enough per the subsections below
+
+
+Via ``pre-commit`` hook
+~~~~~~~~~~~~~~~~~~~~~~~
+
+See :gh:`pre-commit/pre-commit` for instructions, sample ``.pre-commit-config.yaml``:
+
+.. code-block:: yaml
+
+    - repo: https://github.com/tox-dev/tox-toml-fmt
+      rev: "v1.0.0"
+      hooks:
+        - id: tox-toml-fmt
+
+Via Python
+~~~~~~~~~~
+
+.. automodule:: tox_toml_fmt
+   :members:
+
+.. toctree::
+   :hidden:
+
+   self
+
+Configuration via file
+----------------------
+
+The ``tox-toml-fmt`` table is used when present in the ``tox.toml`` file:
+
+.. code-block:: toml
+
+  [tox-toml-fmt]
+
+  # after how many column width split arrays/dicts into multiple lines, 1 will force always
+  column_width = 120
+
+  # how many spaces use for indentation
+  indent = 2
+
+If not set they will default to values from the CLI, the example above shows the defaults.
+
+Command line interface
+----------------------
+.. sphinx_argparse_cli::
+  :module: tox_toml_fmt.__main__
+  :func: _build_our_cli
+  :prog: tox-toml-fmt
+  :title:
diff --git a/tox-toml-fmt/pyproject.toml b/tox-toml-fmt/pyproject.toml
new file mode 100644
index 0000000..e035b47
--- /dev/null
+++ b/tox-toml-fmt/pyproject.toml
@@ -0,0 +1,123 @@
+[build-system]
+build-backend = "maturin"
+requires = [
+  "maturin>=1.7.4",
+]
+
+[project]
+name = "tox-toml-fmt"
+description = "Format your pyproject.toml file"
+readme = "README.md"
+keywords = [
+  "format",
+  "pyproject",
+]
+license.file = "LICENSE.txt"
+authors = [
+  { name = "Bernat Gabor", email = "gaborjbernat@gmail.com" },
+]
+requires-python = ">=3.9"
+classifiers = [
+  "License :: OSI Approved :: MIT License",
+  "Operating System :: OS Independent",
+  "Programming Language :: Python",
+  "Programming Language :: Python :: 3 :: Only",
+  "Programming Language :: Python :: 3.9",
+  "Programming Language :: Python :: 3.10",
+  "Programming Language :: Python :: 3.11",
+  "Programming Language :: Python :: 3.12",
+  "Programming Language :: Python :: 3.13",
+]
+dynamic = [
+  "version",
+]
+dependencies = [
+  "toml-fmt-common==1.0.1",
+]
+urls."Bug Tracker" = "https://github.com/tox-dev/toml-fmt/issues"
+urls."Changelog" = "https://github.com/tox-dev/toml-fmt/blob/main/tox-toml-fmt/CHANGELOG.md"
+urls.Documentation = "https://github.com/tox-dev/toml-fmt/"
+urls."Source Code" = "https://github.com/tox-dev/toml-fmt"
+scripts.tox-toml-fmt = "tox_toml_fmt.__main__:runner"
+
+[dependency-groups]
+dev = [
+  { include-group = "docs" },
+  { include-group = "fix" },
+  { include-group = "test" },
+  { include-group = "type" },
+]
+test = [
+  "covdefaults>=2.3",
+  "pytest>=8.3.2",
+  "pytest-cov>=5",
+  "pytest-mock>=3.14",
+]
+type = [
+  "mypy==1.11.2",
+  "types-cachetools>=5.5.0.20240820",
+  "types-chardet>=5.0.4.6",
+  { include-group = "test" },
+]
+docs = [
+  "furo>=2024.8.6",
+  "sphinx>=8.0.2",
+  "sphinx-argparse-cli>=1.18.2",
+  "sphinx-autodoc-typehints>=2.4.4",
+  "sphinx-copybutton>=0.5.2",
+  "sphinx-inline-tabs>=2023.4.21",
+]
+fix = [
+  "pre-commit-uv>=4.1.3",
+]
+pkg-meta = [
+  "check-wheel-contents>=0.6",
+  "twine>=5.1.1",
+  "uv>=0.4.17",
+]
+
+[tool.maturin]
+bindings = "pyo3"
+manifest-path = "Cargo.toml"
+module-name = "tox_toml_fmt._lib"
+python-source = "src"
+strip = true
+include = [
+  "rust-toolchain.toml",
+]
+
+[tool.cibuildwheel]
+skip = [
+  "pp*",
+  "*musl*",
+]
+
+[tool.pyproject-fmt]
+max_supported_python = "3.13"
+
+[tool.pytest]
+ini_options.testpaths = [
+  "tests",
+]
+
+[tool.coverage]
+html.show_contexts = true
+html.skip_covered = false
+paths.source = [
+  "src",
+  ".tox/*/.venv/lib/*/site-packages",
+  ".tox\\*\\.venv\\Lib\\site-packages",
+  ".tox/*/lib/*/site-packages",
+  ".tox\\*\\Lib\\site-packages",
+  "**/src",
+  "**\\src",
+]
+report.fail_under = 100
+run.parallel = true
+run.plugins = [
+  "covdefaults",
+]
+
+[tool.mypy]
+show_error_codes = true
+strict = true
diff --git a/tox-toml-fmt/rust/src/global.rs b/tox-toml-fmt/rust/src/global.rs
new file mode 100644
index 0000000..ec85f89
--- /dev/null
+++ b/tox-toml-fmt/rust/src/global.rs
@@ -0,0 +1,8 @@
+use common::taplo::rowan::SyntaxNode;
+use common::taplo::syntax::Lang;
+
+use common::table::Tables;
+
+pub fn reorder_tables(root_ast: &SyntaxNode<Lang>, tables: &Tables) {
+    tables.reorder(root_ast, &["", "env_run_base", "env"]);
+}
diff --git a/tox-toml-fmt/rust/src/main.rs b/tox-toml-fmt/rust/src/main.rs
new file mode 100644
index 0000000..7754472
--- /dev/null
+++ b/tox-toml-fmt/rust/src/main.rs
@@ -0,0 +1,71 @@
+use std::string::String;
+
+use common::taplo::formatter::{format_syntax, Options};
+use common::taplo::parser::parse;
+use pyo3::prelude::{PyModule, PyModuleMethods};
+use pyo3::{pyclass, pyfunction, pymethods, pymodule, wrap_pyfunction, Bound, PyResult};
+
+use crate::global::reorder_tables;
+use common::table::Tables;
+mod global;
+#[cfg(test)]
+mod tests;
+
+#[pyclass(frozen, get_all)]
+pub struct Settings {
+    column_width: usize,
+    indent: usize,
+}
+
+#[pymethods]
+impl Settings {
+    #[new]
+    #[pyo3(signature = (*, column_width, indent ))]
+    const fn new(column_width: usize, indent: usize) -> Self {
+        Self { column_width, indent }
+    }
+}
+
+/// Format toml file
+#[must_use]
+#[pyfunction]
+pub fn format_toml(content: &str, opt: &Settings) -> String {
+    let root_ast = parse(content).into_syntax().clone_for_update();
+    let tables = Tables::from_ast(&root_ast);
+
+    reorder_tables(&root_ast, &tables);
+
+    let options = Options {
+        align_entries: false,         // do not align by =
+        align_comments: true,         // align inline comments
+        align_single_comments: true,  // align comments after entries
+        array_trailing_comma: true,   // ensure arrays finish with trailing comma
+        array_auto_expand: true,      // arrays go to multi line when too long
+        array_auto_collapse: false,   // do not collapse for easier diffs
+        compact_arrays: false,        // leave whitespace
+        compact_inline_tables: false, // leave whitespace
+        compact_entries: false,       // leave whitespace
+        column_width: opt.column_width,
+        indent_tables: false,
+        indent_entries: false,
+        inline_table_expand: true,
+        trailing_newline: true,
+        allowed_blank_lines: 1, // one blank line to separate
+        indent_string: " ".repeat(opt.indent),
+        reorder_keys: false,   // respect custom order
+        reorder_arrays: false, // for natural sorting we need to this ourselves
+        crlf: false,
+    };
+    format_syntax(root_ast, options)
+}
+
+/// # Errors
+///
+/// Will return `PyErr` if an error is raised during formatting.
+#[pymodule]
+#[pyo3(name = "_lib")]
+pub fn _lib(m: &Bound<'_, PyModule>) -> PyResult<()> {
+    m.add_function(wrap_pyfunction!(format_toml, m)?)?;
+    m.add_class::<Settings>()?;
+    Ok(())
+}
diff --git a/tox-toml-fmt/rust/src/tests/global_tests.rs b/tox-toml-fmt/rust/src/tests/global_tests.rs
new file mode 100644
index 0000000..5c2c84a
--- /dev/null
+++ b/tox-toml-fmt/rust/src/tests/global_tests.rs
@@ -0,0 +1,55 @@
+use common::taplo::formatter::{format_syntax, Options};
+use common::taplo::parser::parse;
+use indoc::indoc;
+use rstest::rstest;
+
+use crate::global::reorder_tables;
+use common::table::Tables;
+
+#[rstest]
+#[case::reorder(
+        indoc ! {r#"
+        # comment
+        requires = ["tox>=4.22"]
+
+        [demo]
+        desc = "demo"
+
+        [env.type]
+        description = "type"
+
+        [env.docs]
+        description = "docs"
+
+        [env_run_base]
+        description = "base"
+
+    "#},
+        indoc ! {r#"
+        # comment
+        requires = ["tox>=4.22"]
+
+        [env_run_base]
+        description = "base"
+
+        [env.type]
+        description = "type"
+
+        [env.docs]
+        description = "docs"
+
+        [demo]
+        desc = "demo"
+    "#},
+)]
+fn test_reorder_table(#[case] start: &str, #[case] expected: &str) {
+    let root_ast = parse(start).into_syntax().clone_for_update();
+    let tables = Tables::from_ast(&root_ast);
+    reorder_tables(&root_ast, &tables);
+    let opt = Options {
+        column_width: 120,
+        ..Options::default()
+    };
+    let got = format_syntax(root_ast, opt);
+    assert_eq!(got, expected);
+}
diff --git a/tox-toml-fmt/rust/src/tests/main_tests.rs b/tox-toml-fmt/rust/src/tests/main_tests.rs
new file mode 100644
index 0000000..ed0092f
--- /dev/null
+++ b/tox-toml-fmt/rust/src/tests/main_tests.rs
@@ -0,0 +1,84 @@
+use indoc::indoc;
+use rstest::rstest;
+
+use crate::{format_toml, Settings};
+
+#[rstest]
+#[case::simple(
+        indoc ! {r#"
+        requires = ["tox>=4.22"]
+        env_list = ["3.13", "3.12"]
+        skip_missing_interpreters = true
+
+        [env_run_base]
+        description = "run the tests with pytest under {env_name}"
+        commands = [ ["pytest"] ]
+
+        [env.type]
+        description = "run type check on code base"
+        commands = [["mypy", "src{/}tox_toml_fmt"], ["mypy", "tests"]]
+    "#},
+        indoc ! {r#"
+        requires = [ "tox>=4.22" ]
+        env_list = [ "3.13", "3.12" ]
+        skip_missing_interpreters = true
+
+        [env_run_base]
+        description = "run the tests with pytest under {env_name}"
+        commands = [ [ "pytest" ] ]
+
+        [env.type]
+        description = "run type check on code base"
+        commands = [ [ "mypy", "src{/}tox_toml_fmt" ], [ "mypy", "tests" ] ]
+    "#},
+        2,
+)]
+#[case::empty(
+        indoc ! {r""},
+        "\n",
+        2,
+)]
+fn test_format_toml(#[case] start: &str, #[case] expected: &str, #[case] indent: usize) {
+    let settings = Settings {
+        column_width: 80,
+        indent,
+    };
+    let got = format_toml(start, &settings);
+    assert_eq!(got, expected);
+    let second = format_toml(got.as_str(), &settings);
+    assert_eq!(second, got);
+}
+
+/// Test that the column width is respected,
+/// and that arrays are neither exploded nor collapsed without reason
+#[test]
+fn test_column_width() {
+    let start = indoc! {r#"
+        # comment
+        requires = ["tox>=4.22"]
+        env_list = ["fix", "3.13", "3.12", "3.11", "3.10", "3.9", "type", "docs", "pkg_meta"]
+        "#};
+    let settings = Settings {
+        column_width: 50,
+        indent: 4,
+    };
+    let got = format_toml(start, &settings);
+    let expected = indoc! {r#"
+        # comment
+        requires = [ "tox>=4.22" ]
+        env_list = [
+            "fix",
+            "3.13",
+            "3.12",
+            "3.11",
+            "3.10",
+            "3.9",
+            "type",
+            "docs",
+            "pkg_meta",
+        ]
+        "#};
+    assert_eq!(got, expected);
+    let second = format_toml(got.as_str(), &settings);
+    assert_eq!(second, got);
+}
diff --git a/tox-toml-fmt/rust/src/tests/mod.rs b/tox-toml-fmt/rust/src/tests/mod.rs
new file mode 100644
index 0000000..68e908a
--- /dev/null
+++ b/tox-toml-fmt/rust/src/tests/mod.rs
@@ -0,0 +1,2 @@
+mod global_tests;
+mod main_tests;
diff --git a/tox-toml-fmt/src/tox_toml_fmt/__init__.py b/tox-toml-fmt/src/tox_toml_fmt/__init__.py
new file mode 100644
index 0000000..ceef8d6
--- /dev/null
+++ b/tox-toml-fmt/src/tox_toml_fmt/__init__.py
@@ -0,0 +1,9 @@
+"""Format pyproject.toml files."""
+
+from __future__ import annotations
+
+from .__main__ import runner as run
+
+__all__ = [
+    "run",
+]
diff --git a/tox-toml-fmt/src/tox_toml_fmt/__main__.py b/tox-toml-fmt/src/tox_toml_fmt/__main__.py
new file mode 100644
index 0000000..42775de
--- /dev/null
+++ b/tox-toml-fmt/src/tox_toml_fmt/__main__.py
@@ -0,0 +1,82 @@
+"""Main entry point for the formatter."""
+
+from __future__ import annotations
+
+from typing import TYPE_CHECKING, Sequence
+
+from toml_fmt_common import ArgumentGroup, FmtNamespace, TOMLFormatter, _build_cli, run  # noqa: PLC2701
+
+from ._lib import Settings, format_toml
+
+if TYPE_CHECKING:
+    from argparse import ArgumentParser
+
+
+class PyProjectFmtNamespace(FmtNamespace):
+    """Formatting arguments."""
+
+
+class ToxTOMLFormatter(TOMLFormatter[PyProjectFmtNamespace]):
+    """Format pyproject.toml."""
+
+    def __init__(self) -> None:
+        """Create a formatter."""
+        super().__init__(PyProjectFmtNamespace())
+
+    @property
+    def prog(self) -> str:
+        """:return: program name"""
+        return "tox-toml-fmt"
+
+    @property
+    def filename(self) -> str:
+        """:return: filename operating on"""
+        return "pyproject.toml"
+
+    def add_format_flags(self, parser: ArgumentGroup) -> None:
+        """
+        Additional formatter  config.
+
+        :param parser: parser to operate on.
+        """
+
+    @property
+    def override_cli_from_section(self) -> tuple[str, ...]:
+        """:return: path where config overrides live"""
+        return ("tox-toml-fmt",)
+
+    def format(self, text: str, opt: PyProjectFmtNamespace) -> str:  # noqa: PLR6301
+        """
+        Perform the formatting.
+
+        :param text: content to operate on
+        :param opt: formatter config
+        :return: formatted text
+        """
+        settings = Settings(
+            column_width=opt.column_width,
+            indent=opt.indent,
+        )
+        return format_toml(text, settings)
+
+
+def runner(args: Sequence[str] | None = None) -> int:
+    """
+    Run the formatter.
+
+    :param args: CLI arguments
+    :return: exit code
+    """
+    return run(ToxTOMLFormatter(), args)
+
+
+def _build_our_cli() -> ArgumentParser:
+    return _build_cli(ToxTOMLFormatter())[0]  # pragma: no cover
+
+
+__all__ = [
+    "runner",
+]
+
+if __name__ == "__main__":
+    raise SystemExit(runner())
diff --git a/tox-toml-fmt/src/tox_toml_fmt/_lib.pyi b/tox-toml-fmt/src/tox_toml_fmt/_lib.pyi
new file mode 100644
index 0000000..56e571f
--- /dev/null
+++ b/tox-toml-fmt/src/tox_toml_fmt/_lib.pyi
@@ -0,0 +1,13 @@
+class Settings:
+    def __init__(
+        self,
+        *,
+        column_width: int,
+        indent: int,
+    ) -> None: ...
+    @property
+    def column_width(self) -> int: ...
+    @property
+    def indent(self) -> int: ...
+
+def format_toml(content: str, settings: Settings) -> str: ...
diff --git a/tox-toml-fmt/src/tox_toml_fmt/py.typed b/tox-toml-fmt/src/tox_toml_fmt/py.typed
new file mode 100644
index 0000000..e69de29
diff --git a/tox-toml-fmt/tests/test_lib.py b/tox-toml-fmt/tests/test_lib.py
new file mode 100644
index 0000000..7f13131
--- /dev/null
+++ b/tox-toml-fmt/tests/test_lib.py
@@ -0,0 +1,46 @@
+from __future__ import annotations
+
+from textwrap import dedent
+
+import pytest
+from tox_toml_fmt._lib import Settings, format_toml
+
+
+@pytest.mark.parametrize(
+    ("start", "expected"),
+    [
+        pytest.param(
+            """\
+            requires = ["tox>=4.22"]
+            env_list = ["3.13", "3.12"]
+            skip_missing_interpreters = true
+
+            [env_run_base]
+            description = "run the tests with pytest under {env_name}"
+            commands = [ ["pytest"] ]
+
+            [env.type]
+            description = "run type check on code base"
+            commands = [["mypy", "src{/}tox_toml_fmt"], ["mypy", "tests"]]
+            """,
+            """\
+            requires = [ "tox>=4.22" ]
+            env_list = [ "3.13", "3.12" ]
+            skip_missing_interpreters = true
+
+            [env_run_base]
+            description = "run the tests with pytest under {env_name}"
+            commands = [ [ "pytest" ] ]
+
+            [env.type]
+            description = "run type check on code base"
+            commands = [ [ "mypy", "src{/}tox_toml_fmt" ], [ "mypy", "tests" ] ]
+            """,
+            id="example",
+        ),
+    ],
+)
+def test_format_toml(start: str, expected: str) -> None:
+    settings = Settings(column_width=120, indent=4)
+    res = format_toml(dedent(start), settings)
+    assert res == dedent(expected)
diff --git a/tox-toml-fmt/tests/test_main.py b/tox-toml-fmt/tests/test_main.py
new file mode 100644
index 0000000..9b55276
--- /dev/null
+++ b/tox-toml-fmt/tests/test_main.py
@@ -0,0 +1,149 @@
+from __future__ import annotations
+
+from textwrap import dedent
+from typing import TYPE_CHECKING
+
+import pytest
+from tox_toml_fmt.__main__ import runner as run
+
+if TYPE_CHECKING:
+    from pathlib import Path
+
+    from pytest_mock import MockerFixture
+
+
+@pytest.mark.parametrize(
+    "in_place",
+    [
+        True,
+        False,
+    ],
+    ids=("in_place", "print"),
+)
+@pytest.mark.parametrize(
+    "check",
+    [
+        True,
+        False,
+    ],
+    ids=["check", "no_check"],
+)
+@pytest.mark.parametrize(
+    "cwd",
+    [
+        True,
+        False,
+    ],
+    ids=["cwd", "absolute"],
+)
+@pytest.mark.parametrize(
+    ("start", "outcome", "output"),
+    [
+        pytest.param(
+            'requires = [ "tox>=4.22" ]\n',
+            'requires = [ "tox>=4.22" ]\n',
+            "no change for {0}\n",
+            id="formatted",
+        ),
+        pytest.param(
+            'requires = ["tox>=4.22"]\n',
+            'requires = [ "tox>=4.22" ]\n',
+            '--- {0}\n\n+++ {0}\n\n@@ -1 +1 @@\n\n-requires = ["tox>=4.22"]\n+requires = [ "tox>=4.22" ]\n',
+            id="format",
+        ),
+    ],
+)
+def test_main(
+    tmp_path: Path,
+    capsys: pytest.CaptureFixture[str],
+    in_place: bool,
+    start: str,
+    outcome: str,
+    output: str,
+    monkeypatch: pytest.MonkeyPatch,
+    mocker: MockerFixture,
+    cwd: bool,
+    check: bool,
+) -> None:
+    mocker.patch("toml_fmt_common._color_diff", lambda t: t)
+    if cwd:
+        monkeypatch.chdir(tmp_path)
+    pyproject_toml = tmp_path / "tox.toml"
+    pyproject_toml.write_text(start)
+    args = [str(pyproject_toml)]
+    if not in_place:
+        args.append("--stdout")
+
+    if check:
+        args.append("--check")
+
+        if not in_place:
+            with pytest.raises(SystemExit):
+                run(args)
+            assert pyproject_toml.read_text() == start
+            return
+
+    result = run(args)
+    assert result == (0 if start == outcome else 1)
+
+    out, err = capsys.readouterr()
+    assert not err
+
+    if check:
+        assert pyproject_toml.read_text() == start
+    elif in_place:
+        name = "tox.toml" if cwd else str(tmp_path / "tox.toml")
+        output = output.format(name)
+        assert pyproject_toml.read_text() == outcome
+        assert out == output
+    else:
+        assert out == outcome
+
+
+@pytest.mark.parametrize("indent", [0, 2, 4])
+def test_indent(tmp_path: Path, indent: int) -> None:
+    start = """\
+    requires = [
+     "a"
+    ]
+    """
+
+    expected = f"""\
+    requires = [
+    {" " * indent}"a",
+    ]
+    """
+    pyproject_toml = tmp_path / "tox.toml"
+    pyproject_toml.write_text(dedent(start))
+    args = [str(pyproject_toml), "--indent", str(indent)]
+    run(args)
+    output = pyproject_toml.read_text()
+    assert output == dedent(expected)
+
+
+def test_tox_toml_config(tmp_path: Path, capsys: pytest.CaptureFixture[str]) -> None:
+    txt = """\
+    requires = [
+     "a",
+    ]
+
+    [tox-toml-fmt]
+    indent = 6
+    """
+    filename = tmp_path / "tox.toml"
+    filename.write_text(dedent(txt))
+    run([str(filename)])
+
+    expected = """\
+    requires = [
+          "a",
+    ]
+
+    [tox-toml-fmt]
+    indent = 6
+    """
+    got = filename.read_text()
+    assert got == dedent(expected)
+    out, err = capsys.readouterr()
+    assert out
+    assert not err
diff --git a/tox-toml-fmt/tests/test_pyproject_toml_fmt.py b/tox-toml-fmt/tests/test_pyproject_toml_fmt.py
new file mode 100644
index 0000000..3e9eb74
--- /dev/null
+++ b/tox-toml-fmt/tests/test_pyproject_toml_fmt.py
@@ -0,0 +1,15 @@
+from __future__ import annotations
+
+import subprocess  # noqa: S404
+import sys
+from pathlib import Path
+
+
+def test_help_invocation_as_module() -> None:
+    subprocess.check_call([sys.executable, "-m", "tox_toml_fmt", "--help"])
+
+
+def test_help_invocation_as_script() -> None:
+    subprocess.check_call(
+        [str(Path(sys.executable).parent / "tox-toml-fmt"), "--help"],
+    )
diff --git a/tox-toml-fmt/tox.toml b/tox-toml-fmt/tox.toml
new file mode 100644
index 0000000..f758e8f
--- /dev/null
+++ b/tox-toml-fmt/tox.toml
@@ -0,0 +1,102 @@
+requires = ["tox>=4.22"]
+env_list = ["fix", "3.13", "3.12", "3.11", "3.10", "3.9", "type", "docs", "pkg_meta"]
+skip_missing_interpreters = true
+
+[env_run_base]
+description = "run the tests with pytest under {env_name}"
+package = "wheel"
+wheel_build_env = ".pkg"
+dependency_groups = ["test"]
+pass_env = ["PYTEST_*", "SSL_CERT_FILE"]
+set_env.COVERAGE_FILE = { replace = "env", name = "COVERAGE_FILE", default = "{work_dir}{/}.coverage.{env_name}" }
+set_env.COVERAGE_FILECOVERAGE_PROCESS_START = "{tox_root}{/}pyproject.toml"
+commands = [
+    [
+        "pytest",
+        { replace = "posargs", extend = true, default = [
+            "--durations",
+            "5",
+            "--junitxml",
+            "{work_dir}{/}junit.{env_name}.xml",
+            "--no-cov-on-fail",
+            "--cov",
+            "{env_site_packages_dir}{/}tox_toml_fmt",
+            "--cov",
+            "{tox_root}{/}tests",
+            "--cov-config",
+            "{tox_root}{/}pyproject.toml",
+            "--cov-context",
+            "test",
+            "--cov-report",
+            "term-missing:skip-covered",
+            "--cov-report",
+            "html:{env_tmp_dir}{/}htmlcov",
+            "--cov-report",
+            "xml:{work_dir}{/}coverage.{env_name}.xml",
+            "tests",
+        ] },
+    ],
+]
+
+[env.type]
+description = "run type check on code base"
+dependency_groups = ["type"]
+commands = [["mypy", "src{/}tox_toml_fmt"], ["mypy", "tests"]]
+
+[env.docs]
+description = "build documentation"
+dependency_groups = ["docs"]
+commands = [
+    [
+        "sphinx-build",
+        "-d",
+        "{env_tmp_dir}{/}docs_tree",
+        "docs",
+        "{env:READTHEDOCS_OUTPUT:{work_dir}{/}docs_out}/html",
+        "--color",
+        "-b",
+        "html",
+        { replace = "posargs", default = [
+            "-b",
+            "linkcheck",
+        ], extend = true },
+        "-W",
+    ],
+    [
+        "python",
+        "-c",
+        'print(r"documentation available under file://{work_dir}{/}docs_out{/}index.html")',
+    ],
+]
+
+[env.pkg_meta]
+description = "check that the long description is valid"
+skip_install = true
+dependency_groups = ["pkg_meta"]
+commands = [
+    [
+        "uv",
+        "build",
+        "--sdist",
+        "--wheel",
+        "--out-dir",
+        "{env_tmp_dir}",
+        ".",
+    ],
+    [
+        "twine",
+        "check",
+        "{env_tmp_dir}{/}*",
+    ],
+    [
+        "check-wheel-contents",
+        "--no-config",
+        "{env_tmp_dir}",
+    ],
+]
+
+[env.dev]
+description = "dev environment with all deps at {envdir}"
+package = "editable"
+dependency_groups = ["dev"]
+commands = [["uv", "pip", "tree"], ["python", "-c", 'print(r"{env_python}")']]