diff --git a/.github/workflows/python-test.yml b/.github/workflows/python-test.yml
index d1da7d2..288dc6b 100644
--- a/.github/workflows/python-test.yml
+++ b/.github/workflows/python-test.yml
@@ -4,33 +4,42 @@ on:
   workflow_dispatch:
   pull_request:
     branches: ["dev", "main"]
-    paths: ["kaievolve/**", "tests/**", "configs/**", "pyproject.toml", ".github/workflows/python-test.yml"]
+    paths: ["kaievolve/**", "tests/**", "scripts/**", "configs/**", "pyproject.toml", ".github/workflows/python-test.yml"]
   push:
     branches: ["dev", "main"]
-    paths: ["kaievolve/**", "tests/**", "configs/**", "pyproject.toml", ".github/workflows/python-test.yml"]
+    paths: ["kaievolve/**", "tests/**", "scripts/**", "configs/**", "pyproject.toml", ".github/workflows/python-test.yml"]
 
 jobs:
-  test:
+  lint:
+    name: Lint (black)
     runs-on: ubuntu-latest
-
     steps:
-    - name: Checkout code
-      uses: actions/checkout@v3
-
-    - name: Set up Python
-      uses: actions/setup-python@v4
-      with:
-        python-version: '3.9'
-
-    - name: Install dependencies
-      run: |
-        python -m pip install --upgrade pip
-        pip install -e .
-        # Install test dependencies
-        pip install pytest numpy
+      - uses: actions/checkout@v4
+      - uses: actions/setup-python@v5
+        with:
+          python-version: '3.11'
+      - run: pip install "black==25.1.0"
+      - name: Black formatting check
+        run: black --check --line-length 100 kaievolve tests scripts
 
-    - name: Run unit tests
-      env:
-        OPENAI_API_KEY: ${{ secrets.OPENAI_API_KEY }}
-      run: |
-        python -m unittest discover -s tests -p "test_*.py" -v
+  test:
+    name: Tests (py${{ matrix.python-version }})
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        python-version: ['3.9', '3.10', '3.11', '3.12']
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-python@v5
+        with:
+          python-version: ${{ matrix.python-version }}
+      - name: Install dependencies
+        run: |
+          python -m pip install --upgrade pip
+          pip install -e .
+          pip install pytest numpy
+      - name: Run unit tests
+        env:
+          OPENAI_API_KEY: ${{ secrets.OPENAI_API_KEY }}
+        run: python -m unittest discover -s tests -p "test_*.py"
diff --git a/kaievolve/cli.py b/kaievolve/cli.py
index 4c3af53..34ca0e5 100644
--- a/kaievolve/cli.py
+++ b/kaievolve/cli.py
@@ -118,6 +118,7 @@ def _resolve_best_program(run_dir):
     candidates = [os.path.join(run_dir, "best", "best_program.py")]
     ckpts = glob.glob(os.path.join(run_dir, "checkpoints", "checkpoint_*"))
     if ckpts:
+
         def _ckpt_num(p):
             m = re.search(r"checkpoint_(\d+)$", p.rstrip("/"))
             return int(m.group(1)) if m else -1
diff --git a/tests/test_cli_init_from.py b/tests/test_cli_init_from.py
index fdaf5fd..8459a49 100644
--- a/tests/test_cli_init_from.py
+++ b/tests/test_cli_init_from.py
@@ -20,9 +20,7 @@ def test_prefers_best_dir(self):
         with TemporaryDirectory() as d:
             _write(os.path.join(d, "best", "best_program.py"))
             _write(os.path.join(d, "checkpoints", "checkpoint_10", "best_program.py"))
-            self.assertEqual(
-                _resolve_best_program(d), os.path.join(d, "best", "best_program.py")
-            )
+            self.assertEqual(_resolve_best_program(d), os.path.join(d, "best", "best_program.py"))
 
     def test_falls_back_to_latest_checkpoint(self):
         with TemporaryDirectory() as d: