diff --git a/atomizer-dashboard/frontend/src/components/canvas/SpecRenderer.tsx b/atomizer-dashboard/frontend/src/components/canvas/SpecRenderer.tsx
index 7370e852..d60fa1c0 100644
--- a/atomizer-dashboard/frontend/src/components/canvas/SpecRenderer.tsx
+++ b/atomizer-dashboard/frontend/src/components/canvas/SpecRenderer.tsx
@@ -273,6 +273,15 @@ function SpecRendererInner({
   const [showResults, setShowResults] = useState(false);
   const [validationStatus, setValidationStatus] = useState<'valid' | 'invalid' | 'unchecked'>('unchecked');
 
+  // When connecting Extractor → Objective/Constraint and the extractor has multiple outputs,
+  // we prompt the user to choose which output_name to use.
+  const [pendingOutputSelect, setPendingOutputSelect] = useState<null | {
+    sourceId: string;
+    targetId: string;
+    outputNames: string[];
+    selected: string;
+  }>(null);
+
   // Build trial history for sparklines (extract objective values from recent trials)
   const trialHistory = useMemo(() => {
     const history: Record<string, number[]> = {};
@@ -589,39 +598,43 @@ function SpecRendererInner({
       const targetType = classify(targetId);
 
       try {
-        // Always persist the visual edge (for now)
-        await addEdge(sourceId, targetId);
-
         // Option A truth model: objective/constraint source is the real linkage.
-        // When user connects Extractor -> Objective/Constraint, update *.source accordingly.
+        // When user connects Extractor -> Objective/Constraint, we must choose an output_name.
         if (spec && sourceType === 'extractor' && (targetType === 'objective' || targetType === 'constraint')) {
           const ext = spec.extractors.find((e) => e.id === sourceId);
+          const outputNames = (ext?.outputs || []).map((o) => o.name).filter(Boolean);
 
-          // Choose a sensible default output:
-          // - prefer 'value' if present
-          // - else if only one output, use it
-          // - else use first output
-          const outputs = ext?.outputs || [];
-          const preferred = outputs.find((o) => o.name === 'value')?.name;
-          const outputName =
-            preferred || (outputs.length === 1 ? outputs[0].name : outputs.length > 0 ? outputs[0].name : 'value');
-
-          if (targetType === 'objective') {
-            await updateNode(targetId, {
-              source: { extractor_id: sourceId, output_name: outputName },
-            });
-          } else {
-            await updateNode(targetId, {
-              source: { extractor_id: sourceId, output_name: outputName },
+          // If extractor has multiple outputs, prompt the user.
+          if (outputNames.length > 1) {
+            const preferred = outputNames.includes('value') ? 'value' : outputNames[0];
+            setPendingOutputSelect({
+              sourceId,
+              targetId,
+              outputNames,
+              selected: preferred,
             });
+            return;
           }
+
+          // Single (or zero) output: choose deterministically.
+          const outputName = outputNames[0] || 'value';
+
+          // Persist edge + runnable source.
+          await addEdge(sourceId, targetId);
+          await updateNode(targetId, {
+            source: { extractor_id: sourceId, output_name: outputName },
+          });
+          return;
         }
+
+        // Default: just persist the visual edge.
+        await addEdge(sourceId, targetId);
       } catch (err) {
         console.error('Failed to add connection:', err);
         setError(err instanceof Error ? err.message : 'Failed to add connection');
       }
     },
-    [editable, addEdge, setError, spec, updateNode]
+    [editable, addEdge, setError, spec, updateNode, setPendingOutputSelect]
   );
 
   // Handle node clicks for selection
@@ -760,6 +773,34 @@ function SpecRendererInner({
     [editable, addNode, selectNode, setError, localNodes]
   );
 
+  // -------------------------------------------------------------------------
+  // Output selection modal handlers (Extractor → Objective/Constraint)
+  // -------------------------------------------------------------------------
+
+  const confirmOutputSelection = useCallback(async () => {
+    if (!pendingOutputSelect) return;
+
+    const { sourceId, targetId, selected } = pendingOutputSelect;
+
+    try {
+      // Persist edge + runnable source wiring
+      await addEdge(sourceId, targetId);
+      await updateNode(targetId, {
+        source: { extractor_id: sourceId, output_name: selected },
+      });
+    } catch (err) {
+      console.error('Failed to apply output selection:', err);
+      setError(err instanceof Error ? err.message : 'Failed to apply output selection');
+    } finally {
+      setPendingOutputSelect(null);
+    }
+  }, [pendingOutputSelect, addEdge, updateNode, setError]);
+
+  const cancelOutputSelection = useCallback(() => {
+    // User canceled: do not create the edge, do not update source
+    setPendingOutputSelect(null);
+  }, []);
+
   // Loading state
   if (showLoadingOverlay && isLoading && !spec) {
     return (
@@ -842,6 +883,55 @@ function SpecRendererInner({
         </div>
       )}
 
+      {/* Output selection modal (Extractor → Objective/Constraint) */}
+      {pendingOutputSelect && (
+        <div className="absolute inset-0 z-30 flex items-center justify-center bg-black/60 backdrop-blur-sm">
+          <div className="w-[520px] max-w-[90vw] bg-dark-850 border border-dark-600 rounded-xl shadow-2xl p-5">
+            <h3 className="text-white font-semibold text-lg">Select extractor output</h3>
+            <p className="text-sm text-dark-300 mt-1">
+              This extractor provides multiple outputs. Choose which output the target should use.
+            </p>
+
+            <div className="mt-4">
+              <label className="block text-sm font-medium text-dark-300 mb-1">Output</label>
+              <select
+                value={pendingOutputSelect.selected}
+                onChange={(e) =>
+                  setPendingOutputSelect((prev) =>
+                    prev ? { ...prev, selected: e.target.value } : prev
+                  )
+                }
+                className="w-full px-3 py-2 bg-dark-800 border border-dark-600 text-white rounded-lg focus:border-primary-500 focus:outline-none transition-colors"
+              >
+                {pendingOutputSelect.outputNames.map((name) => (
+                  <option key={name} value={name}>
+                    {name}
+                  </option>
+                ))}
+              </select>
+              <p className="text-xs text-dark-500 mt-2">
+                Tip: we default to <span className="text-dark-300 font-medium">value</span> when available.
+              </p>
+            </div>
+
+            <div className="mt-5 flex justify-end gap-2">
+              <button
+                onClick={cancelOutputSelection}
+                className="px-4 py-2 bg-dark-700 text-dark-200 hover:bg-dark-600 rounded-lg border border-dark-600 transition-colors"
+              >
+                Cancel
+              </button>
+              <button
+                onClick={confirmOutputSelection}
+                className="px-4 py-2 bg-primary-600 text-white hover:bg-primary-500 rounded-lg border border-primary-500 transition-colors"
+              >
+                Connect
+              </button>
+            </div>
+          </div>
+        </div>
+      )}
+
       <ReactFlow
         nodes={localNodes}
         edges={edges}