diff --git a/.github/workflows/publish-workflow-catalog.yml b/.github/workflows/publish-workflow-catalog.yml
index 71fac77..0210f5d 100644
--- a/.github/workflows/publish-workflow-catalog.yml
+++ b/.github/workflows/publish-workflow-catalog.yml
@@ -22,6 +22,15 @@ jobs:
     runs-on: ubuntu-latest
     timeout-minutes: 10
     steps:
+      - name: Validate workflow update token
+        env:
+          WORKFLOW_UPDATE_TOKEN: ${{ secrets.WORKFLOW_UPDATE_TOKEN }}
+        run: |
+          if [ -z "$WORKFLOW_UPDATE_TOKEN" ]; then
+            echo "::error::WORKFLOW_UPDATE_TOKEN is not configured. It must have access to the target repositories and permission to create/update pull requests."
+            exit 1
+          fi
+
       - name: Checkout workflow source
         uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
         with:
diff --git a/.github/workflows/sync-consumers.yml b/.github/workflows/sync-consumers.yml
index 9a4a1aa..428b58f 100644
--- a/.github/workflows/sync-consumers.yml
+++ b/.github/workflows/sync-consumers.yml
@@ -26,6 +26,15 @@ jobs:
     outputs:
       matrix: ${{ steps.matrix.outputs.matrix }}
     steps:
+      - name: Validate workflow update token
+        env:
+          WORKFLOW_UPDATE_TOKEN: ${{ secrets.WORKFLOW_UPDATE_TOKEN }}
+        run: |
+          if [ -z "$WORKFLOW_UPDATE_TOKEN" ]; then
+            echo "::error::WORKFLOW_UPDATE_TOKEN is not configured. It must have access to the target repositories and permission to create/update pull requests."
+            exit 1
+          fi
+
       - name: Checkout workflow source
         uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
         with:
diff --git a/tests/test_render_upstream.py b/tests/test_render_upstream.py
index 6f017b5..5234f05 100644
--- a/tests/test_render_upstream.py
+++ b/tests/test_render_upstream.py
@@ -127,6 +127,24 @@ def test_sync_reports_failure_and_continues(self) -> None:
             self.assertEqual(failed["name"], "broken")
             self.assertIn("failed to apply", failed["error"])
 
+    def test_failed_patch_preserves_previous_generated_template(self) -> None:
+        with tempfile.TemporaryDirectory() as directory:
+            root, manifest = self.fixture(directory)
+            source = root / "upstream/vendor/example.yml"
+            source.write_text("name: Changed upstream\n", encoding="utf-8")
+            destination = root / "workflow-templates/example.yml"
+            destination.parent.mkdir(parents=True)
+            destination.write_text("name: Last known good\n", encoding="utf-8")
+
+            report = sync(load_templates(manifest), root)
+
+            self.assertFalse(report["ok"])
+            self.assertEqual(report["failed"], 1)
+            self.assertEqual(
+                destination.read_text(encoding="utf-8"),
+                "name: Last known good\n",
+            )
+
     def test_write_report(self) -> None:
         with tempfile.TemporaryDirectory() as directory:
             report_path = Path(directory) / "report.json"
diff --git a/tests/test_sync_catalog.py b/tests/test_sync_catalog.py
index b2512e1..556b8d0 100644
--- a/tests/test_sync_catalog.py
+++ b/tests/test_sync_catalog.py
@@ -104,6 +104,26 @@ def test_requires_custom_svg_icon(self) -> None:
             )
             collect_publishable(source)
 
+    def test_invalid_source_does_not_partially_modify_catalog(self) -> None:
+        with tempfile.TemporaryDirectory() as directory:
+            root = Path(directory)
+            source = root / "source"
+            target = root / "target"
+            self.write_template(source)
+            target.mkdir()
+            existing = target / "reuse.yml"
+            existing.write_text("name: Published\n", encoding="utf-8")
+
+            (source / "reuse.properties.json").unlink()
+
+            with self.assertRaisesRegex(ValueError, "missing template metadata"):
+                sync_catalog(source, target)
+
+            self.assertEqual(
+                existing.read_text(encoding="utf-8"),
+                "name: Published\n",
+            )
+
     def test_check_detects_drift(self) -> None:
         with tempfile.TemporaryDirectory() as directory:
             root = Path(directory)