diff --git a/.github/workflows/presubmit.yaml b/.github/workflows/presubmit.yaml
index 6c3677c..6124d48 100644
--- a/.github/workflows/presubmit.yaml
+++ b/.github/workflows/presubmit.yaml
@@ -23,7 +23,7 @@ jobs:
     - name: Install dependencies
       run: pip install -e .[dev]
     - name: Check formatting
-      run: nox -s format
+      run: nox -s lint
 
   test:
     name: Test (Python ${{ matrix.python-version }})
diff --git a/notebooks/audience_e2e_advertiser_flow.ipynb b/notebooks/audience_e2e_advertiser_flow.ipynb
index 76037e5..d848de5 100644
--- a/notebooks/audience_e2e_advertiser_flow.ipynb
+++ b/notebooks/audience_e2e_advertiser_flow.ipynb
@@ -485,8 +485,10 @@
     "        print(f\"{ingest_res}\")\n",
     "\n",
     "        if ingest_res.field_warnings:\n",
-    "            print(\"Request ingested successfully, but field warnings were returned. \"\n",
-    "                \"Review warning details and update your implementation as needed.\")\n",
+    "            print(\n",
+    "                \"Request ingested successfully, but field warnings were returned. \"\n",
+    "                \"Review warning details and update your implementation as needed.\"\n",
+    "            )\n",
     "\n",
     "    except Exception as e:\n",
     "        print(f\"Failed to ingest data: {e}\")\n",
diff --git a/notebooks/audience_e2e_data_partner_dual_persona.ipynb b/notebooks/audience_e2e_data_partner_dual_persona.ipynb
index 92426cb..9fc1bbb 100644
--- a/notebooks/audience_e2e_data_partner_dual_persona.ipynb
+++ b/notebooks/audience_e2e_data_partner_dual_persona.ipynb
@@ -656,8 +656,10 @@
     "        print(f\"{ingest_res}\")\n",
     "\n",
     "        if ingest_res.field_warnings:\n",
-    "            print(\"Request ingested successfully, but field warnings were returned. \"\n",
-    "                \"Review warning details and update your implementation as needed.\")\n",
+    "            print(\n",
+    "                \"Request ingested successfully, but field warnings were returned. \"\n",
+    "                \"Review warning details and update your implementation as needed.\"\n",
+    "            )\n",
     "\n",
     "    except Exception as e:\n",
     "        print(f\"Failed to ingest data: {e}\")\n",
diff --git a/notebooks/audience_e2e_data_partner_simplified.ipynb b/notebooks/audience_e2e_data_partner_simplified.ipynb
index aa0ea6f..8b11bb8 100644
--- a/notebooks/audience_e2e_data_partner_simplified.ipynb
+++ b/notebooks/audience_e2e_data_partner_simplified.ipynb
@@ -497,8 +497,10 @@
     "        print(f\"{ingest_res}\")\n",
     "\n",
     "        if ingest_res.field_warnings:\n",
-    "            print(\"Request ingested successfully, but field warnings were returned. \"\n",
-    "                \"Review warning details and update your implementation as needed.\")\n",
+    "            print(\n",
+    "                \"Request ingested successfully, but field warnings were returned. \"\n",
+    "                \"Review warning details and update your implementation as needed.\"\n",
+    "            )\n",
     "\n",
     "    except Exception as e:\n",
     "        print(f\"Failed to ingest data: {e}\")\n",
diff --git a/noxfile.py b/noxfile.py
index cdf45dd..eea9842 100644
--- a/noxfile.py
+++ b/noxfile.py
@@ -55,10 +55,24 @@ def tests(session):
     session.run(*COVERAGE_COMMAND)
 
 
+def _format(session, check=False):
+    black_command = ["black"]
+    if check:
+        black_command.append("--check")
+    black_command.append(".")
+    session.run(*black_command)
+
+
+@nox.session(venv_backend="none")
+def lint(session):
+    """Fails if the code is not formatted correctly."""
+    _format(session, check=True)
+
+
 @nox.session(venv_backend="none")
 def format(session):
     """Runs the black formatter and applies formatting fixes."""
-    session.run("black", ".")
+    _format(session)
 
 
 @nox.session(python="3.12")