diff --git a/apps/desktop/src/renderer/src/components/MessageItem.tsx b/apps/desktop/src/renderer/src/components/MessageItem.tsx
index 2989441..abfb83c 100644
--- a/apps/desktop/src/renderer/src/components/MessageItem.tsx
+++ b/apps/desktop/src/renderer/src/components/MessageItem.tsx
@@ -217,11 +217,13 @@ export function AssistantTurn({
       if (seg.kind === 'thinking') {
         const rows = thinkingRows(seg.text)
         if (rows.length === 0) return
-        // 该思考段之后已有正文段在流：思考已完成，表头从「正在思考」切回
+        // 只有「最后一段且之后没有正文」才算仍在流式；否则一旦 pi 在回合内
+        // 分多轮发出（静默间隙 streaming 抖动），已完成段会被误判回流式态
+        const isLast = i === segments.length - 1
         const followedByText = segments.some((s, k) => k > i && s.kind === 'text' && s.text.length > 0)
         streamNodes.push(
           <div key={`seg-${i}`} className={collapsed && hasProcess ? 'hidden' : 'mb-3'}>
-            <Thinking rows={rows} streaming={streaming && !followedByText} />
+            <Thinking rows={rows} streaming={streaming && isLast && !followedByText} />
           </div>
         )
         return
diff --git a/apps/desktop/src/renderer/src/components/Thinking.tsx b/apps/desktop/src/renderer/src/components/Thinking.tsx
index a5f0749..d1e8f86 100644
--- a/apps/desktop/src/renderer/src/components/Thinking.tsx
+++ b/apps/desktop/src/renderer/src/components/Thinking.tsx
@@ -1,10 +1,10 @@
-import { useRef, useState } from 'react'
+import { useEffect, useRef, useState } from 'react'
 import type { ReactNode } from 'react'
 
 /** 可展开的思考轨迹（ZCode 式实时预览）。
- * 流式收起时表头显示「正在思考 · 最新一行」持续刷新，不展示全部；
- * 展开时完整展示全部思考（不截断），新内容在尾部、由会话级自动滚动跟随，
- * 用户上滚即取消跟随（外层滚动已实现）。结束后收起为「思考过程」，
+ * 流式中默认收起：表头「正在思考 · 最新一行」持续刷新，不展示全部；
+ * 手动展开时限高滚动预览——新内容在尾部并自动吸底，用户上滚即取消吸底
+ * （滚回底部恢复）。完成后默认展开完整展示全部思考，表头「思考 · 首行」。
  * 点击表头可手动展开/收起。rows 由真实思考文本逐行喂入。 */
 export function Thinking({
   rows,
@@ -17,16 +17,37 @@ export function Thinking({
   activeLabel?: string
   doneLabel?: string
 }): ReactNode {
+  // 流式中默认收起，完成后默认展开；用户点击后以手动状态为准
   const [manualExpanded, setManualExpanded] = useState<boolean | null>(null)
-  const expanded = manualExpanded ?? streaming
+  const expanded = manualExpanded ?? !streaming
 
   // 流式轨迹的行必须「随到随显」：fade-up 的 both+delay 会让新行在延迟期间
   // 透明但占高，流式期间底部因此持续留出一大片空白。交错入场只保留给
   // 非流式一次性渲染的静态轨迹（挂载时决定，之后不变更，避免整段重播动画）。
   const streamedMountRef = useRef(streaming)
 
+  // 流式展开时的滚动吸底：新内容到达且当前贴着底部时跟随；用户上滚即取消，
+  // 滚回底部恢复。收起时重置吸底，重新展开直接落在最新内容。完成后不限高。
+  const scrollRef = useRef<HTMLDivElement>(null)
+  const pinnedRef = useRef(true)
+  const handleScroll = (): void => {
+    const el = scrollRef.current
+    if (!el) return
+    pinnedRef.current = el.scrollHeight - el.scrollTop - el.clientHeight < 24
+  }
+  useEffect(() => {
+    if (!expanded) {
+      pinnedRef.current = true
+      return
+    }
+    const el = scrollRef.current
+    if (el && pinnedRef.current && streaming) el.scrollTop = el.scrollHeight
+  }, [rows, expanded, streaming])
+
   const latest = rows.length > 0 ? rows[rows.length - 1].primary : ''
-  const suffix = streaming && !expanded ? latest : ''
+  const firstLine = rows.length > 0 ? rows[0].primary : ''
+  const statusWord = streaming ? activeLabel : expanded ? '思考' : doneLabel
+  const suffix = streaming ? (expanded ? '' : latest) : expanded ? firstLine : ''
 
   return (
     <div className="flex w-full max-w-95 flex-col">
@@ -50,14 +71,14 @@ export function Thinking({
                 animation: 'shimmer-text 1.4s linear infinite'
               }}
             >
-              {activeLabel}
+              {statusWord}
             </span>
           ) : (
             <span
               className="whitespace-nowrap text-[13px] font-medium text-ink-2"
               style={{ animation: 'fade-in 350ms ease-out both' }}
             >
-              {doneLabel}
+              {statusWord}
             </span>
           )}
           {suffix && (
@@ -80,7 +101,7 @@ export function Thinking({
         </svg>
       </button>
 
-      {/* 展开轨迹：完整展示全部思考，左侧 hairline 随内容延伸 */}
+      {/* 展开轨迹：流式时限高滚动预览（吸底跟随），完成后完整展示全部思考 */}
       <div
         className="grid transition-[grid-template-rows,opacity]"
         style={{
@@ -90,24 +111,30 @@ export function Thinking({
         }}
       >
         <div className="min-h-0 overflow-hidden">
-          <div className="relative mt-1 ml-[5px] pl-4">
-            <span aria-hidden className="absolute bottom-0 left-[3px] top-0 w-px bg-line" />
-            <div className="flex flex-col gap-1 py-1">
-              {rows.map((row, i) => (
-                <div
-                  key={i}
-                  className="flex min-h-7 w-full items-start gap-2 rounded-control px-1.5 py-0.5 text-left"
-                  style={{
-                    animation: streamedMountRef.current
-                      ? 'fade-up 250ms ease'
-                      : `fade-up 400ms ease ${Math.min(i, 8) * 120}ms both`
-                  }}
-                >
-                  <span className="min-w-0 text-[12.5px] leading-relaxed break-words text-ink-2">
-                    {row.primary}
-                  </span>
-                </div>
-              ))}
+          <div
+            ref={scrollRef}
+            onScroll={handleScroll}
+            className={`mt-1 ml-[5px] pl-4 ${streaming ? 'max-h-[220px] overflow-y-auto' : ''}`}
+          >
+            <div className="relative">
+              <span aria-hidden className="absolute bottom-0 left-[3px] top-0 w-px bg-line" />
+              <div className="flex flex-col gap-1 py-1">
+                {rows.map((row, i) => (
+                  <div
+                    key={i}
+                    className="flex min-h-7 w-full items-start gap-2 rounded-control px-1.5 py-0.5 text-left"
+                    style={{
+                      animation: streamedMountRef.current
+                        ? 'fade-up 250ms ease'
+                        : `fade-up 400ms ease ${Math.min(i, 8) * 120}ms both`
+                    }}
+                  >
+                    <span className="min-w-0 text-[12.5px] leading-relaxed break-words text-ink-2">
+                      {row.primary}
+                    </span>
+                  </div>
+                ))}
+              </div>
             </div>
           </div>
         </div>