diff --git a/backend/src/routes/adminWorkflows.js b/backend/src/routes/adminWorkflows.js
index 4392fdba..325af114 100644
--- a/backend/src/routes/adminWorkflows.js
+++ b/backend/src/routes/adminWorkflows.js
@@ -131,8 +131,11 @@ router.post('/', requirePermission('workflows.manage'), async (req, res, next) =
         name: b.name, description: b.description || null, enabled: !!b.enabled, version: 1,
         trigger_type: b.trigger_type, trigger_config: b.trigger_config ? JSON.stringify(b.trigger_config) : null,
         created_by: req.admin?.id || null,
-      });
-      const newId = ins[0];
+      }).returning('id');
+      // Postgres returns [] without an explicit returning clause, so ins[0]
+      // would be undefined → the child node inserts would violate NOT NULL.
+      // Normalise the {id} (pg) vs bare id (sqlite) shapes.
+      const newId = ins[0]?.id ?? ins[0];
       await writeGraph(trx, newId, 1, b.nodes, b.edges);
       return newId;
     });
diff --git a/backend/src/services/_workflowSeedBoot.js b/backend/src/services/_workflowSeedBoot.js
index 6601c607..a6a70cc9 100644
--- a/backend/src/services/_workflowSeedBoot.js
+++ b/backend/src/services/_workflowSeedBoot.js
@@ -127,8 +127,12 @@ async function seedBuiltinWorkflowsAtBoot(db, logger) {
         trigger_config: JSON.stringify({ seedVersion: SEED_VERSION }),
         is_builtin: true,
         builtin_key: DUNNING_KEY,
-      });
-      await writeGraph(trx, ins[0], 1, nodes, edges);
+      }).returning('id');
+      // Postgres returns [] without `.returning`, so ins[0] would be undefined
+      // and the child node inserts would roll back on NOT NULL. Normalise the
+      // {id} (pg) vs bare-id (sqlite) shapes.
+      const workflowId = ins[0]?.id ?? ins[0];
+      await writeGraph(trx, workflowId, 1, nodes, edges);
     });
 
     booted = true;