fix(web): guard autosave against in-flight lost-update race

web/app/workflows/[id]/page.tsx

@@ -56,6 +56,8 @@ export default function WorkflowBuilder() {
     const [lastSaved, setLastSaved] = useState<Date | null>(null);
     const [, setTick] = useState(0);
     const savedSnapshotRef = useRef<string | null>(null);
+    const savingRef = useRef(false);
+    const wfRef = useRef<Workflow | null>(null);
     const [running, setRunning] = useState(false);
     const [error, setError] = useState<string | null>(null);
     const [notice, setNotice] = useState<string | null>(null);
@@ -107,6 +109,10 @@ export default function WorkflowBuilder() {
         return <div className="p-8 text-text-secondary">Loading…</div>;
     }
 
+    // Keep a ref to the latest workflow so an in-flight save can tell whether
+    // the user edited again while the request was on the wire.
+    wfRef.current = wf;
+
     const libById = (sid?: string) => (sid ? library?.find((l) => l.step_id === sid) : undefined);
 
     const sortedSteps = [...wf.steps].sort((a, b) => a.order - b.order);
@@ -115,23 +121,44 @@ export default function WorkflowBuilder() {
     const selectedIdxInWf = selectedRef ? wf.steps.indexOf(selectedRef) : -1;
 
     const save = async () => {
+        // Never run two saves concurrently: a request in flight would race the
+        // next one. The finally block re-triggers if edits landed meanwhile.
+        if (savingRef.current) return;
+        const current = wfRef.current;
+        if (!current) return;
+        const snapshot = JSON.stringify(current);
+        if (snapshot === savedSnapshotRef.current) return;
+        savingRef.current = true;
         setSaving(true);
         setError(null);
         try {
-            const updated = await api.updateWorkflow(id, wf);
+            const updated = await api.updateWorkflow(id, current);
             if (!updated || !Array.isArray(updated.steps)) {
                 setError("Save failed: server returned an unexpected response.");
                 return;
             }
-            // Record the snapshot BEFORE setWf so the autosave effect sees the
-            // incoming state as already-saved and doesn't re-trigger.
-            savedSnapshotRef.current = JSON.stringify(updated);
-            setWf(updated);
+            if (JSON.stringify(wfRef.current) === snapshot) {
+                // Nothing changed while the request was in flight: adopt the
+                // server echo as the new saved baseline.
+                savedSnapshotRef.current = JSON.stringify(updated);
+                setWf(updated);
+            } else {
+                // The user edited again mid-flight. Keep their newer state and
+                // mark only the SENT snapshot as saved, so the effect re-fires
+                // and persists the remaining changes.
+                savedSnapshotRef.current = snapshot;
+            }
             setLastSaved(new Date());
         } catch (e) {
             setError((e as Error).message);
         } finally {
+            savingRef.current = false;
             setSaving(false);
+            // If edits arrived during the save (or a concurrent save was
+            // skipped), persist them on the next tick.
+            if (wfRef.current && JSON.stringify(wfRef.current) !== savedSnapshotRef.current) {
+                setTimeout(() => save(), 0);
+            }
         }
     };
 
@@ -604,7 +631,17 @@ export default function WorkflowBuilder() {
                 </aside>
             </div>
 
-            <EditWorkflowModal open={editWorkflowOpen} workflow={wf} onSaved={(w) => setWf(w)} onClose={() => setEditWorkflowOpen(false)} />
+            <EditWorkflowModal
+                open={editWorkflowOpen}
+                workflow={wf}
+                onSaved={(w) => {
+                    // The modal already persisted w; sync the snapshot so
+                    // autosave doesn't fire a redundant follow-up save.
+                    savedSnapshotRef.current = JSON.stringify(w);
+                    setWf(w);
+                }}
+                onClose={() => setEditWorkflowOpen(false)}
+            />
             <StepPickerModal
                 open={pickerOpen}
                 onClose={() => setPickerOpen(false)}