diff --git a/.github/workflows/daily.yml b/.github/workflows/daily.yml
index 8e3379db4..a881a5bdc 100644
--- a/.github/workflows/daily.yml
+++ b/.github/workflows/daily.yml
@@ -67,6 +67,8 @@ jobs:
       - uses: actions/checkout@v4
       - uses: actions/setup-python@v5
         with:
+          # TODO: Use Python 3.12. As of 2024-03-08, several third-party
+          # packages fail to install with Python 3.12.
           python-version: "3.10"
           cache: pip
           cache-dependency-path: |
@@ -115,7 +117,7 @@ jobs:
           path: stub_uploader
       - uses: actions/setup-python@v5
         with:
-          python-version: "3.11"
+          python-version: "3.12"
       - name: Install uv
         run: curl -LsSf https://astral.sh/uv/install.sh | sh
       - name: Run tests
diff --git a/.github/workflows/meta_tests.yml b/.github/workflows/meta_tests.yml
index 5c32d8ab4..fe85b1177 100644
--- a/.github/workflows/meta_tests.yml
+++ b/.github/workflows/meta_tests.yml
@@ -37,7 +37,7 @@ jobs:
       - uses: actions/checkout@v4
       - uses: actions/setup-python@v5
         with:
-          python-version: "3.11"
+          python-version: "3.12"
       - run: curl -LsSf https://astral.sh/uv/install.sh | sh
       - run: uv pip install -r requirements-tests.txt --system
       - run: python ./tests/typecheck_typeshed.py --platform=${{ matrix.platform }}
@@ -52,7 +52,8 @@ jobs:
       - uses: actions/checkout@v4
       - uses: actions/setup-python@v5
         with:
-          python-version: "3.9"
+          # Max supported Python version as of pytype 2024.2.27.
+          python-version: "3.11"
       - run: curl -LsSf https://astral.sh/uv/install.sh | sh
       - run: uv pip install -r requirements-tests.txt --system
       - name: Get pyright version
@@ -66,7 +67,7 @@ jobs:
         with:
           version: ${{ steps.pyright_version.outputs.value }}
           python-platform: ${{ matrix.python-platform }}
-          python-version: "3.9"
+          python-version: "3.9" # The Python version to test against.
           project: ./pyrightconfig.scripts_and_tests.json
   stubsabot-dry-run:
     name: Stubsabot dry run
@@ -75,7 +76,7 @@ jobs:
       - uses: actions/checkout@v4
       - uses: actions/setup-python@v5
         with:
-          python-version: "3.11"
+          python-version: "3.12"
       - run: curl -LsSf https://astral.sh/uv/install.sh | sh
       - name: Git config
         run: |
diff --git a/.github/workflows/mypy_primer.yml b/.github/workflows/mypy_primer.yml
index 5ef85217b..a7082d8e7 100644
--- a/.github/workflows/mypy_primer.yml
+++ b/.github/workflows/mypy_primer.yml
@@ -31,6 +31,8 @@ jobs:
           fetch-depth: 0
       - uses: actions/setup-python@v5
         with:
+          # TODO: As of 2024-03-08, confluent-kafka fails to install with
+          # Python 3.12.
           python-version: "3.11"
       - name: Install dependencies
         run: pip install git+https://github.com/hauntsaninja/mypy_primer.git
diff --git a/.github/workflows/stubsabot.yml b/.github/workflows/stubsabot.yml
index 2e76e3d9a..c3cf596f2 100644
--- a/.github/workflows/stubsabot.yml
+++ b/.github/workflows/stubsabot.yml
@@ -26,7 +26,7 @@ jobs:
           fetch-depth: 0
       - uses: actions/setup-python@v5
         with:
-          python-version: "3.11"
+          python-version: "3.12"
       - run: curl -LsSf https://astral.sh/uv/install.sh | sh
       - name: git config
         run: |
diff --git a/.github/workflows/stubtest_third_party.yml b/.github/workflows/stubtest_third_party.yml
index a5c0f7e79..7d1a80e1d 100644
--- a/.github/workflows/stubtest_third_party.yml
+++ b/.github/workflows/stubtest_third_party.yml
@@ -41,6 +41,8 @@ jobs:
           fetch-depth: 0
       - uses: actions/setup-python@v5
         with:
+          # TODO: Use Python 3.12. As of 2024-03-08, several third-party
+          # packages fail to install with Python 3.12.
           python-version: "3.10"
           cache: pip
           cache-dependency-path: |
diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index f69eb0a21..3dc1ce1fa 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -29,7 +29,7 @@ jobs:
       - uses: actions/checkout@v4
       - uses: actions/setup-python@v5
         with:
-          python-version: "3.11"
+          python-version: "3.12"
       - run: curl -LsSf https://astral.sh/uv/install.sh | sh
       - run: uv pip install -r requirements-tests.txt --system
       - run: python ./tests/check_consistent.py
@@ -41,7 +41,7 @@ jobs:
       - uses: actions/checkout@v4
       - uses: actions/setup-python@v5
         with:
-          python-version: "3.11"
+          python-version: "3.12"
       - run: ./tests/check_new_syntax.py
 
   pytype:
@@ -51,6 +51,7 @@ jobs:
       - uses: actions/checkout@v4
       - uses: actions/setup-python@v5
         with:
+          # Max supported Python version as of pytype 2024.2.27.
           python-version: "3.11"
       - name: Install uv
         run: curl -LsSf https://astral.sh/uv/install.sh | sh
@@ -89,7 +90,7 @@ jobs:
       - uses: actions/checkout@v4
       - uses: actions/setup-python@v5
         with:
-          python-version: "3.11"
+          python-version: "3.12"
       - run: curl -LsSf https://astral.sh/uv/install.sh | sh
       - run: uv pip install -r requirements-tests.txt --system
       - run: python ./tests/regr_test.py --all --verbosity QUIET
@@ -106,7 +107,7 @@ jobs:
       - uses: actions/checkout@v4
       - uses: actions/setup-python@v5
         with:
-          python-version: "3.11"
+          python-version: "3.12"
       - name: Install uv
         run: curl -LsSf https://astral.sh/uv/install.sh | sh
       - name: Install typeshed test-suite requirements
@@ -171,7 +172,7 @@ jobs:
           path: stub_uploader
       - uses: actions/setup-python@v5
         with:
-          python-version: "3.11"
+          python-version: "3.12"
       - name: Install uv
         run: curl -LsSf https://astral.sh/uv/install.sh | sh
       - name: Run tests