diff --git a/frontend/public/lsf/lsf.html b/frontend/public/lsf/lsf.html
index 91a6f7f..101ad8c 100644
--- a/frontend/public/lsf/lsf.html
+++ b/frontend/public/lsf/lsf.html
@@ -314,6 +314,17 @@
               return;
             }
 
+            if (msg.type === "LS_EXPORT_CHECK") {
+              const raw = exportSelectedAnnotation();
+              const requestId =
+                msg.payload && typeof msg.payload === "object" ? msg.payload.requestId : null;
+              if (requestId) {
+                raw.requestId = requestId;
+              }
+              postToParent("LS_EXPORT_CHECK_RESULT", raw);
+              return;
+            }
+
             if (msg.type === "LS_RESET") {
               destroyLabelStudio();
               postToParent("LS_RESET_DONE", {});
diff --git a/frontend/src/pages/DataAnnotation/Annotate/LabelStudioTextEditor.tsx b/frontend/src/pages/DataAnnotation/Annotate/LabelStudioTextEditor.tsx
index b754d19..1a97e5c 100644
--- a/frontend/src/pages/DataAnnotation/Annotate/LabelStudioTextEditor.tsx
+++ b/frontend/src/pages/DataAnnotation/Annotate/LabelStudioTextEditor.tsx
@@ -68,6 +68,7 @@ type ExportPayload = {
   fileId?: string | null;
   segmentIndex?: number | string | null;
   annotation?: Record<string, unknown>;
+  requestId?: string | null;
 };
 
 const LSF_IFRAME_SRC = "/lsf/lsf.html";
@@ -91,20 +92,67 @@ const resolvePayloadMessage = (payload: unknown) => {
   return undefined;
 };
 
+const isRecord = (value: unknown): value is Record<string, unknown> =>
+  !!value && typeof value === "object" && !Array.isArray(value);
+
+const normalizeSnapshotValue = (value: unknown, seen: WeakSet<object>): unknown => {
+  if (!value || typeof value !== "object") return value;
+  const obj = value as object;
+  if (seen.has(obj)) return undefined;
+  seen.add(obj);
+  if (Array.isArray(value)) {
+    return value.map((item) => normalizeSnapshotValue(item, seen));
+  }
+  const record = value as Record<string, unknown>;
+  const sorted: Record<string, unknown> = {};
+  Object.keys(record)
+    .sort()
+    .forEach((key) => {
+      sorted[key] = normalizeSnapshotValue(record[key], seen);
+    });
+  return sorted;
+};
+
+const stableStringify = (value: unknown) => {
+  const normalized = normalizeSnapshotValue(value, new WeakSet<object>());
+  return JSON.stringify(normalized);
+};
+
+const buildAnnotationSnapshot = (annotation?: Record<string, unknown>) => {
+  if (!annotation) return "";
+  const cleaned: Record<string, unknown> = { ...annotation };
+  delete cleaned.updated_at;
+  delete cleaned.updatedAt;
+  delete cleaned.created_at;
+  delete cleaned.createdAt;
+  return stableStringify(cleaned);
+};
+
+const buildSnapshotKey = (fileId: string, segmentIndex?: number) =>
+  `${fileId}::${segmentIndex ?? "full"}`;
+
 export default function LabelStudioTextEditor() {
   const { projectId = "" } = useParams();
   const navigate = useNavigate();
-  const { message } = App.useApp();
+  const { message, modal } = App.useApp();
 
   const origin = useMemo(() => window.location.origin, []);
   const iframeRef = useRef<HTMLIFrameElement | null>(null);
   const initSeqRef = useRef(0);
   const expectedTaskIdRef = useRef<number | null>(null);
+  const exportCheckRef = useRef<{
+    requestId: string;
+    resolve: (payload?: ExportPayload) => void;
+    timer?: number;
+  } | null>(null);
+  const exportCheckSeqRef = useRef(0);
+  const savedSnapshotsRef = useRef<Record<string, string>>({});
 
   const [loadingProject, setLoadingProject] = useState(true);
   const [loadingTasks, setLoadingTasks] = useState(false);
   const [loadingTaskDetail, setLoadingTaskDetail] = useState(false);
   const [saving, setSaving] = useState(false);
+  const [segmentSwitching, setSegmentSwitching] = useState(false);
 
   const [iframeReady, setIframeReady] = useState(false);
   const [lsReady, setLsReady] = useState(false);
@@ -193,10 +241,13 @@ export default function LabelStudioTextEditor() {
       if (seq !== initSeqRef.current) return;
 
       // 更新分段状态
+      const segmentIndex = data?.segmented
+        ? resolveSegmentIndex(data.currentSegmentIndex) ?? 0
+        : undefined;
       if (data?.segmented) {
         setSegmented(true);
         setSegments(data.segments || []);
-        setCurrentSegmentIndex(data.currentSegmentIndex || 0);
+        setCurrentSegmentIndex(segmentIndex ?? 0);
       } else {
         setSegmented(false);
         setSegments([]);
@@ -209,15 +260,20 @@ export default function LabelStudioTextEditor() {
         fileId: fileId,
       };
       if (data?.segmented) {
-        const segmentIndex = resolveSegmentIndex(data.currentSegmentIndex) ?? 0;
-        taskData.segment_index = segmentIndex;
-        taskData.segmentIndex = segmentIndex;
+        const normalizedIndex = segmentIndex ?? 0;
+        taskData.segment_index = normalizedIndex;
+        taskData.segmentIndex = normalizedIndex;
       }
       const taskForIframe = {
         ...task,
         data: taskData,
       };
 
+      const annotations = Array.isArray(taskForIframe.annotations) ? taskForIframe.annotations : [];
+      const initialAnnotation = annotations.length > 0 && isRecord(annotations[0]) ? annotations[0] : undefined;
+      savedSnapshotsRef.current[buildSnapshotKey(fileId, segmentIndex)] =
+        buildAnnotationSnapshot(initialAnnotation);
+
       expectedTaskIdRef.current = Number(taskForIframe?.id) || null;
       postToIframe("LS_INIT", {
         labelConfig: project.labelConfig,
@@ -262,14 +318,14 @@ export default function LabelStudioTextEditor() {
     if (expectedTaskIdRef.current && payloadTaskId) {
       if (Number(payloadTaskId) !== expectedTaskIdRef.current) {
         message.warning("已忽略过期的保存请求");
-        return;
+        return false;
       }
     }
     const fileId = payload?.fileId || selectedFileId;
     const annotation = payload?.annotation;
     if (!fileId || !annotation || typeof annotation !== "object") {
       message.error("导出标注失败：缺少 fileId/annotation");
-      return;
+      return false;
     }
     const payloadSegmentIndex = resolveSegmentIndex(payload?.segmentIndex);
     const segmentIndex =
@@ -288,6 +344,10 @@ export default function LabelStudioTextEditor() {
       message.success("标注已保存");
       await loadTasks(true);
 
+      const snapshotKey = buildSnapshotKey(String(fileId), segmentIndex);
+      const snapshot = buildAnnotationSnapshot(isRecord(annotation) ? annotation : undefined);
+      savedSnapshotsRef.current[snapshotKey] = snapshot;
+
       // 分段模式下更新当前段落的标注状态
       if (segmented && segmentIndex !== undefined) {
         setSegments((prev) =>
@@ -298,9 +358,11 @@ export default function LabelStudioTextEditor() {
           )
         );
       }
+      return true;
     } catch (e) {
       console.error(e);
       message.error("保存失败");
+      return false;
     } finally {
       setSaving(false);
     }
@@ -313,6 +375,45 @@ export default function LabelStudioTextEditor() {
     selectedFileId,
   ]);
 
+  const requestExportForCheck = useCallback(() => {
+    if (!iframeReady || !lsReady) return Promise.resolve(undefined);
+    if (exportCheckRef.current) {
+      if (exportCheckRef.current.timer) {
+        window.clearTimeout(exportCheckRef.current.timer);
+      }
+      exportCheckRef.current.resolve(undefined);
+      exportCheckRef.current = null;
+    }
+    const requestId = `check_${Date.now()}_${++exportCheckSeqRef.current}`;
+    return new Promise<ExportPayload | undefined>((resolve) => {
+      const timer = window.setTimeout(() => {
+        if (exportCheckRef.current?.requestId === requestId) {
+          exportCheckRef.current = null;
+        }
+        resolve(undefined);
+      }, 3000);
+      exportCheckRef.current = {
+        requestId,
+        resolve,
+        timer,
+      };
+      postToIframe("LS_EXPORT_CHECK", { requestId });
+    });
+  }, [iframeReady, lsReady, postToIframe]);
+
+  const confirmSaveBeforeSwitch = useCallback(() => {
+    return new Promise<boolean>((resolve) => {
+      modal.confirm({
+        title: "当前段落有未保存标注",
+        content: "切换段落前请先保存当前标注。",
+        okText: "保存并切换",
+        cancelText: "取消",
+        onOk: () => resolve(true),
+        onCancel: () => resolve(false),
+      });
+    });
+  }, [modal]);
+
   const requestExport = () => {
     if (!selectedFileId) {
       message.warning("请先选择文件");
@@ -324,8 +425,55 @@ export default function LabelStudioTextEditor() {
   // 段落切换处理
   const handleSegmentChange = async (newIndex: number) => {
     if (newIndex === currentSegmentIndex) return;
-    setCurrentSegmentIndex(newIndex);
-    await initEditorForFile(selectedFileId, newIndex);
+    if (segmentSwitching || saving || loadingTaskDetail) return;
+    if (!iframeReady || !lsReady) {
+      message.warning("编辑器未就绪，无法切换段落");
+      return;
+    }
+
+    setSegmentSwitching(true);
+    try {
+      const payload = await requestExportForCheck();
+      if (!payload) {
+        message.warning("无法读取当前标注，已取消切换");
+        return;
+      }
+
+      const payloadTaskId = payload.taskId;
+      if (expectedTaskIdRef.current && payloadTaskId) {
+        if (Number(payloadTaskId) !== expectedTaskIdRef.current) {
+          message.warning("已忽略过期的标注数据");
+          return;
+        }
+      }
+
+      const payloadFileId = payload.fileId || selectedFileId;
+      const payloadSegmentIndex = resolveSegmentIndex(payload.segmentIndex);
+      const resolvedSegmentIndex =
+        payloadSegmentIndex !== undefined
+          ? payloadSegmentIndex
+          : segmented
+            ? currentSegmentIndex
+            : undefined;
+      const annotation = isRecord(payload.annotation) ? payload.annotation : undefined;
+      const snapshotKey = payloadFileId
+        ? buildSnapshotKey(String(payloadFileId), resolvedSegmentIndex)
+        : undefined;
+      const latestSnapshot = buildAnnotationSnapshot(annotation);
+      const lastSnapshot = snapshotKey ? savedSnapshotsRef.current[snapshotKey] : undefined;
+      const hasUnsavedChange = snapshotKey !== undefined && lastSnapshot !== undefined && latestSnapshot !== lastSnapshot;
+
+      if (hasUnsavedChange) {
+        const shouldSave = await confirmSaveBeforeSwitch();
+        if (!shouldSave) return;
+        const saved = await saveFromExport(payload);
+        if (!saved) return;
+      }
+
+      await initEditorForFile(selectedFileId, newIndex);
+    } finally {
+      setSegmentSwitching(false);
+    }
   };
 
   useEffect(() => {
@@ -340,6 +488,11 @@ export default function LabelStudioTextEditor() {
     setSegmented(false);
     setSegments([]);
     setCurrentSegmentIndex(0);
+    savedSnapshotsRef.current = {};
+    if (exportCheckRef.current?.timer) {
+      window.clearTimeout(exportCheckRef.current.timer);
+    }
+    exportCheckRef.current = null;
 
     if (projectId) loadProject();
   }, [projectId, loadProject]);
@@ -381,6 +534,19 @@ export default function LabelStudioTextEditor() {
         return;
       }
 
+      if (msg.type === "LS_EXPORT_CHECK_RESULT") {
+        const pending = exportCheckRef.current;
+        if (!pending) return;
+        const requestId = payload?.requestId;
+        if (requestId && requestId !== pending.requestId) return;
+        if (pending.timer) {
+          window.clearTimeout(pending.timer);
+        }
+        exportCheckRef.current = null;
+        pending.resolve(payload);
+        return;
+      }
+
       // 兼容 iframe 内部在 submit 时直接上报（若启用）
       if (msg.type === "LS_SUBMIT") {
         saveFromExport(payload);
@@ -531,6 +697,7 @@ export default function LabelStudioTextEditor() {
                     size="small"
                     type={seg.idx === currentSegmentIndex ? "primary" : "default"}
                     onClick={() => handleSegmentChange(seg.idx)}
+                    disabled={segmentSwitching || saving || loadingTaskDetail || !lsReady}
                     style={{ minWidth: 32, padding: "0 8px" }}
                   >
                     {seg.idx + 1}