diff --git a/src/lib/server/auth.ts b/src/lib/server/auth.ts
index 25246b5..1450088 100644
--- a/src/lib/server/auth.ts
+++ b/src/lib/server/auth.ts
@@ -474,9 +474,11 @@ async function getMachineAuthenticatedUser(): Promise<AuthUser | null> {
     return null;
   }
 
-  const machineUserId = process.env.GANTT_MACHINE_USER_ID || "machine-service-user";
-  const machineUserName = process.env.GANTT_MACHINE_USER_NAME || "Mission Control Service";
-  const machineUserEmail = process.env.GANTT_MACHINE_USER_EMAIL || "mission-control@internal.local";
+  // Must always be a valid UUID because tasks.created_by_id / updated_by_id are UUID columns.
+  // Keep a UUID fallback to avoid runtime 22P02 write failures when env injection is missing.
+  const machineUserId = process.env.GANTT_MACHINE_USER_ID || "9c29cc99-81a1-4e75-8dff-cd7cc5ceb5aa";
+  const machineUserName = process.env.GANTT_MACHINE_USER_NAME || "Max";
+  const machineUserEmail = process.env.GANTT_MACHINE_USER_EMAIL || "max@internal.local";
 
   return {
     id: machineUserId,