diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index f9cc2a7..63b6524 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -23,40 +23,79 @@ jobs:
             tox-env: typecheck
     steps:
       - name: Checkout
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
       - name: Setup Python ${{ matrix.python-version }}
-        uses: actions/setup-python@v4
+        uses: actions/setup-python@v5
         with:
           python-version: "${{ matrix.python-version }}"
       - name: Check ${{ matrix.check-name }}
-        uses: pantsbuild/actions/run-tox@e63d2d0e3c339bdffbe5e51e7c39550e3bc527bb
+        uses: pantsbuild/actions/run-tox@b16b9cf47cd566acfe217b1dafc5b452e27e6fd7
         with:
           tox-env: ${{ matrix.tox-env }}
+  unit-tests-legacy:
+    name: (${{ matrix.os }}) TOXENV=py${{ matrix.python-version[0] }}${{ matrix.python-version[1] }}
+    needs: org-check
+    runs-on: ${{ matrix.os }}
+    strategy:
+      matrix:
+        include:
+          - python-version: [2, 7, 18]
+            os: ubuntu-22.04
+          - python-version: [3, 5, 10]
+            os: ubuntu-22.04
+          - python-version: [3, 6, 15]
+            os: ubuntu-22.04
+          - python-version: [2, 7, 18]
+            os: macos-12
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+      - name: Setup Python ${{ join(matrix.python-version, '.') }}
+        id: pyenv
+        uses: gabrielfalcao/pyenv-action@v18
+        with:
+          default: "${{ join(matrix.python-version, '.') }}"
+      - name: Run Unit Tests
+        run: |
+          alias python="${{ steps.pyenv.outputs.pyenv_root }}/versions/${{ join(matrix.python-version, '.') }}/bin/python"
+          python -V
+          python -mensurepip -U
+          python -mpip install -U tox
+          python -mtox -epy${{ matrix.python-version[0] }}${{ matrix.python-version[1] }} -- -vvs
   unit-tests:
     name: (${{ matrix.os }}) TOXENV=py${{ matrix.python-version[0] }}${{ matrix.python-version[1] }}
     needs: org-check
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
-        python-version: [[2, 7], [3, 7], [3, 8], [3, 9], [3, 10], [3, 11], [3, 12, "0-beta.2"]]
-        os: [ubuntu-22.04, macos-12]
-        exclude:
-          - os: macos-12
+        include:
+          - os: ubuntu-22.04
             python-version: [3, 7]
-          - os: macos-12
+          - os: ubuntu-22.04
             python-version: [3, 8]
-          - os: macos-12
+          - os: ubuntu-22.04
             python-version: [3, 9]
-          - os: macos-12
+          - os: ubuntu-22.04
             python-version: [3, 10]
+          - os: ubuntu-22.04
+            python-version: [3, 11]
+          - os: ubuntu-22.04
+            python-version: [3, 12]
+          - os: ubuntu-22.04
+            python-version: [3, 13, "0-alpha.2"]
+          - os: macos-12
+            python-version: [3, 12]
+          - os: macos-12
+            python-version: [3, 13, "0-alpha.2"]
     steps:
       - name: Checkout
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
       - name: Setup Python ${{ join(matrix.python-version, '.') }}
-        uses: actions/setup-python@v4
+        uses: actions/setup-python@v5
         with:
           python-version: "${{ join(matrix.python-version, '.') }}"
       - name: Run Unit Tests
-        uses: pantsbuild/actions/run-tox@e63d2d0e3c339bdffbe5e51e7c39550e3bc527bb
-        with:
-          tox-env: py${{ matrix.python-version[0] }}${{ matrix.python-version[1] }} -- -vvs
+        run: |
+          pip install -U pip
+          pip install -U tox
+          tox -epy${{ matrix.python-version[0] }}${{ matrix.python-version[1] }} -- -vvs
diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
index 71620a2..597b9af 100644
--- a/.github/workflows/release.yml
+++ b/.github/workflows/release.yml
@@ -47,15 +47,15 @@ jobs:
       id-token: write
     steps:
       - name: Checkout ${{ needs.determine-tag.outputs.release-tag }}
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
         with:
           ref: ${{ needs.determine-tag.outputs.release-tag }}
       - name: Setup Python 3.9
-        uses: actions/setup-python@v4
+        uses: actions/setup-python@v5
         with:
           python-version: 3.9
       - name: Package ${{ needs.determine-tag.outputs.release-tag }}
-        uses: pantsbuild/actions/run-tox@e63d2d0e3c339bdffbe5e51e7c39550e3bc527bb
+        uses: pantsbuild/actions/run-tox@b16b9cf47cd566acfe217b1dafc5b452e27e6fd7
         with:
           tox-env: package
       - name: Publish ${{ needs.determine-tag.outputs.release-tag }}
diff --git a/pyproject.toml b/pyproject.toml
index 76f554b..07ac806 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,5 +1,5 @@
 [build-system]
-requires = ["flit_core>=2,<3"]
+requires = ["flit_core>=2,<4"]
 build-backend = "flit_core.buildapi"
 
 [tool.flit.metadata]
@@ -24,9 +24,10 @@ classifiers = [
   "Programming Language :: Python :: 3.10",
   "Programming Language :: Python :: 3.11",
   "Programming Language :: Python :: 3.12",
+  "Programming Language :: Python :: 3.13",
   "Topic :: Utilities",
 ]
-requires-python = ">=2.7,<3.13,!=3.0.*,!=3.1.*,!=3.2.*,!=3.3.*,!=3.4.*"
+requires-python = ">=2.7,<3.14,!=3.0.*,!=3.1.*,!=3.2.*,!=3.3.*,!=3.4.*"
 requires = [
   "setuptools; python_version <= '3.5'",
   "importlib-metadata; python_version == '3.6' or python_version == '3.7'",
diff --git a/tox.ini b/tox.ini
index 046ff55..aede814 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,5 +1,5 @@
 [tox]
-minversion = 3.23.0
+minversion = 3.28.0
 isolated_build = true
 skip_missing_interpreters = true
 
@@ -16,11 +16,16 @@ envlist =
   py310
   py311
   py312
+  py313
 
 [testenv]
 deps =
-  pex==2.1.137; python_version < "3.12"
-  shiv==1.0.3; python_version >= "3.6"
+  pex==2.1.156; python_version < "3.13"
+
+  # The fix for shiv under Python 3.123 is off for review in https://github.com/linkedin/shiv/pull/249
+  shiv==1.0.4; python_version >= "3.6" and python_version < "3.13"
+  git+https://github.com/jsirois/shiv@0c8b3e83238327e51955d66ba4fee28c4fc7107f#egg=shiv; python_version >= "3.13"
+
   pytest==4.6.11; python_version < "3.6"
   pytest==6.2.5; python_version >= "3.6"
 commands =
@@ -70,6 +75,7 @@ commands =
   mypy --python-version 3.10 .
   mypy --python-version 3.11 .
   mypy --python-version 3.12 .
+  mypy --python-version 3.13 .
 
 [_flit]
 basepython = python3