add check before dataset upload

ui/src/components/HFJobsWorkflow.tsx

@@ -253,6 +253,18 @@ export default function HFJobsWorkflow({ jobConfig, onComplete, hackathonEligibl
         throw new Error('Unable to determine a namespace. Validate your HF token or set a namespace in Settings.');
       }
 
+      if (requiresControlImages) {
+        if (!hasControlDataset) {
+          throw new Error('Instruction models require a control dataset. Please select or upload a control dataset before continuing.');
+        }
+
+        const samples = jobConfig?.config?.process?.[0]?.sample?.samples ?? [];
+        const missingCtrl = samples.filter((sample: any) => !sample?.ctrl_img || !String(sample.ctrl_img).trim());
+        if (missingCtrl.length > 0) {
+          throw new Error('Instruction models require a control image for every sample prompt. Please add control images before continuing.');
+        }
+      }
+
       if (datasetSource === 'existing') {
         // Use existing dataset - just validate it exists
         if (!existingDatasetId) {
@@ -318,7 +330,7 @@ export default function HFJobsWorkflow({ jobConfig, onComplete, hackathonEligibl
         }
       }
     } catch (err: any) {
-      setError(err.response?.data?.error || 'Failed to process dataset');
+      setError(err.response?.data?.error || err.message || 'Failed to process dataset');
     } finally {
       setLoading(false);
     }