fix: prevent duplicate consultations with db unique constraint, frontend init once guard, chat history preserved

backend/src/HealthManager.Application/Services/ConsultationService.cs

@@ -41,7 +41,19 @@ public class ConsultationService(AppDbContext db)
             Subject = subject,
         };
         db.Consultations.Add(consultation);
-        await db.SaveChangesAsync();
+        try
+        {
+            await db.SaveChangesAsync();
+        }
+        catch (DbUpdateException)
+        {
+            // Race condition: another request created one between our check and save
+            // The unique index on (PatientId, DoctorId) where Status='active' caught it
+            db.ChangeTracker.Clear();
+            var retry = await db.Consultations
+                .FirstOrDefaultAsync(c => c.PatientId == patientId && c.DoctorId == doctorId && c.Status == "active");
+            return retry!;
+        }
         return consultation;
     }
 

frontend-patient/src/pages/services/ChatPage.tsx

@@ -13,6 +13,7 @@ export function ChatPage() {
   const [text, setText] = useState('');
   const [sending, setSending] = useState(false);
   const bottomRef = useRef<HTMLDivElement>(null);
+  const initRef = useRef(false);
 
   const loadMessages = useCallback((cid: string) => {
     api.get<ConsultationMessage[]>(`/api/consultations/${cid}/messages`)
@@ -20,14 +21,30 @@ export function ChatPage() {
       .catch(() => {});
   }, []);
 
+  // Init once - prevent Strict Mode double-fire
   useEffect(() => {
+    if (initRef.current) return;
+    initRef.current = true;
+
     consultationService.getDoctors().then((docs) => {
       if (docs.length > 0) {
         const doc = docs[0];
         setDoctor(doc);
-        consultationService.startConsultation(doc.id, '在线咨询').then((c) => {
+        // Find existing active consultation first
-          setConsultation(c);
+        api.get<Consultation[]>('/api/consultations').then((res) => {
-          loadMessages(c.id);
+          const existing = (res.data as Record<string, unknown>[]).find(
+            (c) => c.doctorId === doc.id && c.status === 'active'
+          );
+          if (existing) {
+            setConsultation(existing as unknown as Consultation);
+            loadMessages((existing as Record<string, string>).id);
+          } else {
+            // Create new only if none exists
+            consultationService.startConsultation(doc.id, '在线咨询').then((c) => {
+              setConsultation(c);
+              loadMessages(c.id);
+            });
+          }
         });
       }
     });