diff --git a/.idea/material_theme_project_new.xml b/.idea/material_theme_project_new.xml
index 766912b..2abc67e 100644
--- a/.idea/material_theme_project_new.xml
+++ b/.idea/material_theme_project_new.xml
@@ -3,7 +3,10 @@
   <component name="MaterialThemeProjectNewConfig">
     <option name="metadata">
       <MTProjectMetadataState>
-        <option name="userId" value="3d6f1b06:19d820f26b8:-7ffd" />
+        <option name="migrated" value="true" />
+        <option name="pristineConfig" value="false" />
+        <option name="userId" value="2c1a2bb7:18a988f44a2:-8000" />
+        <option name="version" value="8.13.2" />
       </MTProjectMetadataState>
     </option>
   </component>
diff --git a/src/features/writing/components/WritingChecker.tsx b/src/features/writing/components/WritingChecker.tsx
index e03a846..7028939 100644
--- a/src/features/writing/components/WritingChecker.tsx
+++ b/src/features/writing/components/WritingChecker.tsx
@@ -17,7 +17,7 @@ export function WritingChecker() {
   const [improvedExpanded, setImprovedExpanded] = useState(false)
   const [remaining, setRemaining] = useState(getRemainingChecks)
 
-  const { mutate: checkWriting, isPending, isError, error, data: feedback } = useWritingCheck()
+  const { mutate: checkWriting, isPending, isError, error, data: feedback, reset: resetMutation } = useWritingCheck()
   const { requireAuth } = useRequireAuth()
   const user = useAuthStore((s) => s.user)
   const { mutate: awardActivity } = useAwardActivity()
@@ -28,12 +28,13 @@ export function WritingChecker() {
   useEffect(() => {
     if (!user) {
       setRemaining(getRemainingChecks())
+      resetMutation()
       return
     }
     countTodayWritingSubmissions(user.id).then((used) => {
       setRemaining(AUTH_LIMIT - used)
     })
-  }, [user])
+  }, [user, resetMutation])
 
   const charCount = text.length
   const canSubmit = text.trim().length > 0 && remaining > 0 && charCount <= MAX_CHARS && !isPending
diff --git a/src/hooks/use-writing-check.ts b/src/hooks/use-writing-check.ts
index 8a60946..a03b5c8 100644
--- a/src/hooks/use-writing-check.ts
+++ b/src/hooks/use-writing-check.ts
@@ -13,7 +13,18 @@ async function callEdgeFunction(content: string): Promise<WritingFeedback> {
     body: { content },
   })
 
-  if (error) throw new Error(error.message ?? "Đã có lỗi khi chấm bài. Vui lòng thử lại.")
+  if (error) {
+    // The Supabase SDK wraps non-2xx responses in a generic FunctionsHttpError.
+    // Try to parse the actual error body returned by the edge function.
+    try {
+      const body = await (error as unknown as { context: Response }).context.json()
+      if (body?.error) throw new Error(body.error)
+    } catch {
+      // ignore parse failure, fall through to generic message
+    }
+    throw new Error("Đã có lỗi khi chấm bài. Vui lòng thử lại.")
+  }
+
   if (!data) throw new Error("Phản hồi từ AI không hợp lệ. Vui lòng thử lại.")
 
   return data