fix(frontend): Validate and sanitize cron expressions for scheduler API (#10719)

<!-- Clearly explain the need for these changes: -->

### Need for these changes 💥

This PR resolves Linear issue `SECRT-1290`, addressing a critical bug
where the scheduler API fails with a "Wrong number of fields" error when
empty or invalid cron expressions are submitted from the frontend. This
was causing production errors and a poor user experience. It was an off
by one error

### Changes 🏗️


Fix off by one error + add additional logging / error messaging when
someone makes an invalid cron


https://github.com/user-attachments/assets/775881a9-707b-4c4f-b23a-bd7118a358ee



### Checklist 📋

#### For code changes:
- [x] I have clearly listed my changes in the PR description
- [x] I have made a test plan
- [x] I have tested my changes according to the test plan:
- [x] Attempt to schedule an agent with an empty cron expression from
the UI and confirm a frontend toast error.
- [x] Attempt to schedule an agent with an incomplete yearly cron (no
months selected) from the UI and confirm a frontend toast error and UI
warning.
- [x] Attempt to schedule an agent with an incomplete monthly cron (no
days selected) from the UI and confirm a frontend toast error and UI
warning.
- [x] Attempt to schedule an agent with an incomplete weekly cron (no
days selected) from the UI and confirm a frontend toast error and UI
warning.
- [x] Verify that valid cron expressions can still be scheduled
successfully.
  - [x] Run backend unit tests for scheduler cron validation.
  - [x] Run frontend unit tests for cron expression utility.


---
Linear Issue: [SECRT-1290](https://linear.app/autogpt/issue/SECRT-1290)

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Co-authored-by: Cursor Agent <cursoragent@cursor.com>
Co-authored-by: Swifty <craigswift13@gmail.com>

autogpt_platform/frontend/src/components/cron-scheduler-dialog.tsx

@@ -39,6 +39,17 @@ export function CronSchedulerDialog({
       });
       return;
     }
+
+    // Validate cron expression before proceeding
+    if (!cronExpression || cronExpression.trim() === "") {
+      toast({
+        variant: "destructive",
+        title: "Invalid schedule",
+        description: "Please enter a valid cron expression",
+      });
+      return;
+    }
+
     afterCronCreation(cronExpression, scheduleName);
     setOpen(false);
   };

autogpt_platform/frontend/src/components/cron-scheduler.tsx

@@ -213,6 +213,11 @@ export function CronScheduler({
               </Button>
             ))}
           </div>
+          {selectedWeekDays.length === 0 && (
+            <p className="text-sm text-red-500">
+              Please select at least one day of the week
+            </p>
+          )}
         </div>
       )}
       {frequency === "monthly" && (
@@ -274,6 +279,11 @@ export function CronScheduler({
               ))}
             </div>
           )}
+          {selectedMonthDays.length === 0 && (
+            <p className="text-sm text-red-500">
+              Please select at least one day of the month
+            </p>
+          )}
         </div>
       )}
       {frequency === "yearly" && (
@@ -287,7 +297,9 @@ export function CronScheduler({
                 if (selectedMonths.length === months.length) {
                   setSelectedMonths([]);
                 } else {
-                  setSelectedMonths(Array.from({ length: 12 }, (_, i) => i));
+                  setSelectedMonths(
+                    Array.from({ length: 12 }, (_, i) => i + 1),
+                  );
                 }
               }}
             >
@@ -319,6 +331,11 @@ export function CronScheduler({
               );
             })}
           </div>
+          {selectedMonths.length === 0 && (
+            <p className="text-sm text-red-500">
+              Please select at least one month
+            </p>
+          )}
         </div>
       )}
 

autogpt_platform/frontend/src/hooks/useAgentGraph.tsx

@@ -872,6 +872,16 @@ export default function useAgentGraph(
     ) => {
       if (!savedAgent || isScheduling) return;
 
+      // Validate cron expression
+      if (!cronExpression || cronExpression.trim() === "") {
+        toast({
+          variant: "destructive",
+          title: "Invalid schedule",
+          description: "Please enter a valid cron expression",
+        });
+        return;
+      }
+
       setIsScheduling(true);
       try {
         await api.createGraphExecutionSchedule({
@@ -891,7 +901,7 @@ export default function useAgentGraph(
           router.push("/monitoring");
         }
       } catch (error) {
-        console.error(error);
+        console.error("Error scheduling agent:", error);
         toast({
           variant: "destructive",
           title: "Error scheduling agent",

autogpt_platform/frontend/src/lib/cron-expression-utils.ts

@@ -49,16 +49,19 @@ export function makeCronExpression(params: CronExpressionParams): string {
   if (frequency === "daily") return `${params.minute} ${params.hour} * * *`;
   if (frequency === "weekly") {
     const { minute, hour, days } = params;
+    if (days.length === 0) return ""; // Return empty string for invalid weekly schedule
     const weekDaysExpr = days.sort((a, b) => a - b).join(",");
     return `${minute} ${hour} * * ${weekDaysExpr}`;
   }
   if (frequency === "monthly") {
     const { minute, hour, days } = params;
+    if (days.length === 0) return ""; // Return empty string for invalid monthly schedule
     const monthDaysExpr = days.sort((a, b) => a - b).join(",");
     return `${minute} ${hour} ${monthDaysExpr} * *`;
   }
   if (frequency === "yearly") {
     const { minute, hour, months } = params;
+    if (months.length === 0) return ""; // Return empty string for invalid yearly schedule
     const monthList = months.sort((a, b) => a - b).join(",");
     return `${minute} ${hour} 1 ${monthList} *`;
   }