diff --git a/frontend-web/src/open-canvas/api/rewrite.ts b/frontend-web/src/open-canvas/api/rewrite.ts
index 41474426..cae36bdd 100644
--- a/frontend-web/src/open-canvas/api/rewrite.ts
+++ b/frontend-web/src/open-canvas/api/rewrite.ts
@@ -1,7 +1,5 @@
 import { apiFetch } from "@/core/api/fetch-client";
-import { env } from "@/env";
-
-const BASE = (env.NEXT_PUBLIC_BACKEND_BASE_URL as string | undefined) ?? "http://localhost:8001";
+import { getBackendBaseURL } from "@/core/config";
 
 export type RewriteAction = "polish" | "expand" | "shorten" | "tone";
 export type RewriteTone =
@@ -12,7 +10,7 @@ export type RewriteTone =
   | "expressive";
 
 export interface RewriteRequest {
-  threadId: string;
+  threadId?: string | null;
   selection: { from: number; to: number; text: string };
   action: RewriteAction;
   tone?: RewriteTone;
@@ -71,7 +69,7 @@ export async function* streamRewrite(
   req: RewriteRequest,
   signal?: AbortSignal,
 ): AsyncGenerator<RewriteStreamEvent> {
-  const res = await apiFetch(`${BASE}/api/writing/rewrite`, {
+  const res = await apiFetch(`${getBackendBaseURL()}/api/writing/rewrite`, {
     method: "POST",
     headers: { "Content-Type": "application/json" },
     body: JSON.stringify(req),
diff --git a/frontend-web/src/open-canvas/components/ai-writing/AIWritingPanel.tsx b/frontend-web/src/open-canvas/components/ai-writing/AIWritingPanel.tsx
index ec63a4c3..4fdd9b7d 100644
--- a/frontend-web/src/open-canvas/components/ai-writing/AIWritingPanel.tsx
+++ b/frontend-web/src/open-canvas/components/ai-writing/AIWritingPanel.tsx
@@ -1,6 +1,6 @@
-import { useCallback, useState } from 'react';
+import { useCallback, useEffect, useRef, useState } from 'react';
 import { useNavigate } from 'react-router-dom';
-import { Plus, RotateCcw, Settings2, Square } from 'lucide-react';
+import { ChevronsDown, Plus, RotateCcw, Settings2, Square } from 'lucide-react';
 
 import { Button } from '@/components/ui/button';
 import { cn } from '@/lib/utils';
@@ -50,6 +50,84 @@ export function AIWritingPanel() {
   const isRunning = !isIdle && !isDone && !isError;
   const showSkeleton = isRunning && !state.currentPause;
 
+  // ── 自动滚底逻辑 ────────────────────────────────────────────────────────────
+  const scrollRef = useRef<HTMLDivElement>(null);
+  // 程序触发滚动时置 true，阻止 scroll 事件误判为用户上划
+  const isAutoScrollingRef = useRef(false);
+  // 同步 ref：让 scroll/wheel 回调可以立即读取最新值，不依赖 state 异步更新
+  const autoScrollRef = useRef(true);
+  const [autoScroll, setAutoScroll] = useState(true);
+
+  const disableAutoScroll = useCallback(() => {
+    autoScrollRef.current = false;
+    setAutoScroll(false);
+  }, []);
+
+  // 新会话 / 重置后恢复自动滚底
+  useEffect(() => {
+    if (isIdle) {
+      autoScrollRef.current = true;
+      setAutoScroll(true);
+    }
+  }, [isIdle]);
+
+  // 监听用户手动滚动（挂载一次）
+  useEffect(() => {
+    const el = scrollRef.current;
+    if (!el) return;
+
+    // wheel 事件：鼠标滚轮 / 触控板，只由用户触发
+    const onWheel = (e: WheelEvent) => {
+      if (e.deltaY < 0) disableAutoScroll(); // 向上滚
+    };
+
+    // scroll 事件：兼容拖动滚动条的场景
+    // 通过对比前后 scrollTop 判断是否向上滚（排除程序触发的向下滚）
+    let lastTop = el.scrollTop;
+    const onScroll = () => {
+      const cur = el.scrollTop;
+      if (!isAutoScrollingRef.current && cur < lastTop - 2) {
+        disableAutoScroll();
+      }
+      lastTop = cur;
+    };
+
+    el.addEventListener('wheel', onWheel, { passive: true });
+    el.addEventListener('scroll', onScroll, { passive: true });
+    return () => {
+      el.removeEventListener('wheel', onWheel);
+      el.removeEventListener('scroll', onScroll);
+    };
+  }, [disableAutoScroll]);
+
+  // 内容变化时若自动滚底开启则滚到底部
+  useEffect(() => {
+    // 检查同步 ref，避免 state 异步导致的时序竞争
+    if (!autoScrollRef.current || !isRunning || !scrollRef.current) return;
+    const el = scrollRef.current;
+    isAutoScrollingRef.current = true;
+    el.scrollTop = el.scrollHeight;
+    requestAnimationFrame(() => { isAutoScrollingRef.current = false; });
+  }, [
+    autoScroll,   // 点击按钮后重新触发一次
+    isRunning,
+    state.progressEvents.length,
+    state.streamingDraftSections.length,
+    state.streamingReviewItems.length,
+    state.outlineStreamingText,
+    state.currentPause,
+  ]);
+
+  const scrollToBottom = useCallback(() => {
+    const el = scrollRef.current;
+    if (!el) return;
+    isAutoScrollingRef.current = true;
+    el.scrollTop = el.scrollHeight;
+    requestAnimationFrame(() => { isAutoScrollingRef.current = false; });
+    autoScrollRef.current = true;
+    setAutoScroll(true);
+  }, []);
+
   const handleSelectHistory = useCallback((session: AIWritingSessionSummary) => {
     setHistorySession(session);
     // Push historical draft to the right panel
@@ -158,8 +236,9 @@ export function AIWritingPanel() {
         </div>
       </div>
 
-      {/* 主体：可滚动 */}
-      <div className="flex-1 overflow-y-auto">
+      {/* 主体：relative 父容器 + absolute 滚动容器，确保滚动容器尺寸始终正确 */}
+      <div className="flex-1 min-h-0 relative">
+      <div ref={scrollRef} className="absolute inset-0 overflow-y-auto">
         {/* 未开始时显示表单 */}
         {isIdle && (
           <AIWritingForm onSubmit={startWriting} />
@@ -233,7 +312,21 @@ export function AIWritingPanel() {
             {state.error}
           </div>
         )}
-      </div>
+      </div>{/* 滚动内容区结束 */}
+
+      {/* 回到底部悬浮按钮：生成中且用户已上划时出现 */}
+      {isRunning && !autoScroll && (
+        <div className="absolute inset-x-0 bottom-4 flex justify-center z-10 pointer-events-none">
+          <button
+            onClick={scrollToBottom}
+            className="pointer-events-auto flex items-center gap-1.5 px-3 py-1.5 text-xs rounded-full bg-background border shadow-md hover:bg-muted transition-colors whitespace-nowrap"
+          >
+            <ChevronsDown className="size-3.5" />
+            回到底部
+          </button>
+        </div>
+      )}
+      </div>{/* 相对定位容器结束 */}
 
       {/* 状态栏 */}
       {!isIdle && (
diff --git a/frontend-web/src/open-canvas/hooks/useWritingRewrite.ts b/frontend-web/src/open-canvas/hooks/useWritingRewrite.ts
index ab70fcaf..de8a303d 100644
--- a/frontend-web/src/open-canvas/hooks/useWritingRewrite.ts
+++ b/frontend-web/src/open-canvas/hooks/useWritingRewrite.ts
@@ -122,7 +122,7 @@ export function useWritingRewrite(editor: Editor | null) {
 
   const rewrite = useCallback(
     async (action: RewriteAction, tone?: RewriteTone, customInstruction?: string) => {
-      if (!writingSelection || !threadId || !editor) return;
+      if (!writingSelection || !editor) return;
 
       abortRef.current?.abort();
       const abort = new AbortController();
@@ -152,12 +152,12 @@ export function useWritingRewrite(editor: Editor | null) {
       await runStream(req, abort);
     },
     // eslint-disable-next-line react-hooks/exhaustive-deps
-    [writingSelection, threadId, modelName, editor, runStream],
+    [writingSelection, modelName, editor, runStream],
   );
 
   const rewriteFollowUp = useCallback(
     async (instruction: string, action: RewriteAction, tone?: RewriteTone) => {
-      if (!writingSelection || !threadId || !editor) return;
+      if (!writingSelection || !editor) return;
       const prevResult = result;
       if (!prevResult) return;
 
@@ -190,7 +190,7 @@ export function useWritingRewrite(editor: Editor | null) {
       await runStream(req, abort);
     },
     // eslint-disable-next-line react-hooks/exhaustive-deps
-    [writingSelection, threadId, modelName, editor, result, runStream],
+    [writingSelection, modelName, editor, result, runStream],
   );
 
   const reset = useCallback(() => {
diff --git a/offline-backend-20260512/backend/app/gateway/routers/writing.py b/offline-backend-20260512/backend/app/gateway/routers/writing.py
index 6380b88b..b8fe31ab 100644
--- a/offline-backend-20260512/backend/app/gateway/routers/writing.py
+++ b/offline-backend-20260512/backend/app/gateway/routers/writing.py
@@ -70,7 +70,7 @@ class SurroundingContext(BaseModel):
 
 
 class RewriteRequest(BaseModel):
-    thread_id: str = Field(..., alias="threadId")
+    thread_id: str | None = Field(default=None, alias="threadId")
     selection: SelectionInfo
     action: str = Field(..., description="polish | expand | shorten | tone")
     tone: str | None = Field(default=None)