diff --git a/docs/images/message-tooltips/README.md b/docs/images/message-tooltips/README.md
new file mode 100644
index 00000000..d28d90c9
--- /dev/null
+++ b/docs/images/message-tooltips/README.md
@@ -0,0 +1,40 @@
+# 消息操作提示的窄屏边界
+
+用户消息位于聊天右侧，操作提示原来从按钮左边向右展开。即使提示处于 `visibility: hidden`，其宽度仍扩大聊天滚动区域；鼠标悬停或键盘聚焦时，提示末尾被裁掉。
+
+本次仅将 `.v2-user-actions .v2-assistant-action-tooltip` 改为 `left: auto; right: 0`，让用户消息提示向左展开。助手消息提示保留原有对齐方式。
+
+## 真实页面对照
+
+2026-10-22，Windows Edge。修改前使用 #439 / `ef6ae6b1` 的现成生产 bundle，修改后使用本工作树的生产构建。两套页面连接同一份 SQLite 中已保存的对话，使用生产 API；对话由 `cmd/workbenchjourney` 离线模型提供者实际读取 README 后生成。未替换 DOM、注入修复样式或拦截接口制造结果。
+
+600px 中文，鼠标悬停“引用消息”：
+
+| 修改前 | 修改后 |
+| --- | --- |
+| ![中文提示修改前](before-zh-CN-600-hover.png) | ![中文提示修改后](after-zh-CN-600-hover.png) |
+
+390px 英文，使用 Tab 聚焦“Quote message”：
+
+| 修改前 | 修改后 |
+| --- | --- |
+| ![英文提示修改前](before-en-US-390-focus.png) | ![英文提示修改后](after-en-US-390-focus.png) |
+
+## 尺寸与滚动检查
+
+以下各组都检查了初始隐藏状态，以及四个用户操作按钮逐一悬停、逐一键盘聚焦。修改后所有消息提示均位于聊天容器左右边界内。
+
+| 语言 / 视口宽度 | 聊天 clientWidth | 修改前 scrollWidth | 修改后 scrollWidth |
+| --- | ---: | ---: | ---: |
+| 中文 / 600px | 600 | 621 | 600 |
+| 中文 / 390px | 390 | 411 | 390 |
+| English / 600px | 600 | 704 | 600 |
+| English / 390px | 390 | 494 | 390 |
+
+[完整 DOM 尺寸记录](measurements.csv)包含每次测量的提示边界、可见状态和透明度。基线生产 bundle 摘要为 `ecb366bd9e5d692d8dedc260669f3ac456b31113ca1565b50b400add6f97752b`，修改后为 `ddca30555373a91473dd60bb522246d39fc0b39c5f3a023bafe0a216bfbdd945`。
+
+另从真实输入框发送并保存了带长行的 JavaScript 代码块。代码区域的 `scrollWidth` 为 2570px，在 600px / 390px 视口下自身宽度分别为 401px / 237px。横向滚轮将代码自身的 `scrollLeft` 分别推进至 1200px / 2000px；聊天容器保持 `scrollLeft=0`，且 `scrollWidth=clientWidth`。完整代码原文保留。[滚动测量](code-scroll.json)
+
+![390px 代码块内部横向滚动](after-code-scroll-390.png)
+
+`npm run build` 通过。以上为生产网页验证，未作为原生打包窗口验证。
diff --git a/docs/images/message-tooltips/after-code-scroll-390.png b/docs/images/message-tooltips/after-code-scroll-390.png
new file mode 100644
index 00000000..8b31decb
Binary files /dev/null and b/docs/images/message-tooltips/after-code-scroll-390.png differ
diff --git a/docs/images/message-tooltips/after-en-US-390-focus.png b/docs/images/message-tooltips/after-en-US-390-focus.png
new file mode 100644
index 00000000..31c533ae
Binary files /dev/null and b/docs/images/message-tooltips/after-en-US-390-focus.png differ
diff --git a/docs/images/message-tooltips/after-zh-CN-600-hover.png b/docs/images/message-tooltips/after-zh-CN-600-hover.png
new file mode 100644
index 00000000..44316a6c
Binary files /dev/null and b/docs/images/message-tooltips/after-zh-CN-600-hover.png differ
diff --git a/docs/images/message-tooltips/before-en-US-390-focus.png b/docs/images/message-tooltips/before-en-US-390-focus.png
new file mode 100644
index 00000000..f56cd7cf
Binary files /dev/null and b/docs/images/message-tooltips/before-en-US-390-focus.png differ
diff --git a/docs/images/message-tooltips/before-zh-CN-600-hover.png b/docs/images/message-tooltips/before-zh-CN-600-hover.png
new file mode 100644
index 00000000..58e58ede
Binary files /dev/null and b/docs/images/message-tooltips/before-zh-CN-600-hover.png differ
diff --git a/docs/images/message-tooltips/code-scroll.json b/docs/images/message-tooltips/code-scroll.json
new file mode 100644
index 00000000..184f1da6
--- /dev/null
+++ b/docs/images/message-tooltips/code-scroll.json
@@ -0,0 +1,34 @@
+[
+  {
+    "width": 600,
+    "before": {
+      "clientWidth": 401,
+      "scrollWidth": 2570,
+      "scrollLeft": 400,
+      "overflowX": "auto"
+    },
+    "after": {
+      "codeLeft": 1200,
+      "chatLeft": 0,
+      "chatWidth": 600,
+      "chatScrollWidth": 600,
+      "fullCodePreserved": true
+    }
+  },
+  {
+    "width": 390,
+    "before": {
+      "clientWidth": 237,
+      "scrollWidth": 2570,
+      "scrollLeft": 1200,
+      "overflowX": "auto"
+    },
+    "after": {
+      "codeLeft": 2000,
+      "chatLeft": 0,
+      "chatWidth": 390,
+      "chatScrollWidth": 390,
+      "fullCodePreserved": true
+    }
+  }
+]
diff --git a/docs/images/message-tooltips/measurements.csv b/docs/images/message-tooltips/measurements.csv
new file mode 100644
index 00000000..a845a53e
--- /dev/null
+++ b/docs/images/message-tooltips/measurements.csv
@@ -0,0 +1,73 @@
+"phase","locale","viewportWidth","state","buttonIndex","clientWidth","scrollWidth","minTooltipLeft","maxTooltipRight","measuredTooltip","tooltipLeft","tooltipRight","visibility","opacity"
+"before","zh-CN","600","idle",,"600","621","20","620.515625","引用选中文字或整条消息","481.515625","620.515625","hidden","0"
+"before","zh-CN","600","hover","0","600","621","20","620.515625","复制消息","417.515625","479.515625","visible","1"
+"before","zh-CN","600","hover","1","600","621","20","620.515625","回填文字到输入框","449.515625","555.515625","visible","1"
+"before","zh-CN","600","hover","2","600","621","20","620.515625","引用选中文字或整条消息","481.515625","620.515625","visible","1"
+"before","zh-CN","600","hover","3","600","621","20","620.515625","分支到新聊天","513.515625","597.515625","visible","1"
+"before","zh-CN","600","focus","0","600","621","20","620.515625","复制消息","417.515625","479.515625","visible","1"
+"before","zh-CN","600","focus","1","600","621","20","620.515625","回填文字到输入框","449.515625","555.515625","visible","1"
+"before","zh-CN","600","focus","2","600","621","20","620.515625","引用选中文字或整条消息","481.515625","620.515625","visible","1"
+"before","zh-CN","600","focus","3","600","621","20","620.515625","分支到新聊天","513.515625","597.515625","visible","1"
+"before","zh-CN","390","idle",,"390","411","20","410.515625","引用选中文字或整条消息","271.515625","410.515625","hidden","0"
+"before","zh-CN","390","hover","0","390","411","20","410.515625","复制消息","207.515625","269.515625","visible","1"
+"before","zh-CN","390","hover","1","390","411","20","410.515625","回填文字到输入框","239.515625","345.515625","visible","1"
+"before","zh-CN","390","hover","2","390","411","20","410.515625","引用选中文字或整条消息","271.515625","410.515625","visible","1"
+"before","zh-CN","390","hover","3","390","411","20","410.515625","分支到新聊天","303.515625","387.515625","visible","1"
+"before","zh-CN","390","focus","0","390","411","20","410.515625","复制消息","207.515625","269.515625","visible","1"
+"before","zh-CN","390","focus","1","390","411","20","410.515625","回填文字到输入框","239.515625","345.515625","visible","1"
+"before","zh-CN","390","focus","2","390","411","20","410.515625","引用选中文字或整条消息","271.515625","410.515625","visible","1"
+"before","zh-CN","390","focus","3","390","411","20","410.515625","分支到新聊天","303.515625","387.515625","visible","1"
+"before","en-US","600","idle",,"600","704","20","703.578125","Quote selected text or the whole message","481.515625","703.578125","hidden","0"
+"before","en-US","600","hover","0","600","704","20","703.578125","Copy message","417.515625","505.96875","visible","1"
+"before","en-US","600","hover","1","600","704","20","703.578125","Reuse text in composer","449.515625","580.515625","visible","1"
+"before","en-US","600","hover","2","600","704","20","703.578125","Quote selected text or the whole message","481.515625","703.578125","visible","1"
+"before","en-US","600","hover","3","600","704","20","703.578125","Branch into new chat","513.515625","633.4375","visible","1"
+"before","en-US","600","focus","0","600","704","20","703.578125","Copy message","417.515625","505.96875","visible","1"
+"before","en-US","600","focus","1","600","704","20","703.578125","Reuse text in composer","449.515625","580.515625","visible","1"
+"before","en-US","600","focus","2","600","704","20","703.578125","Quote selected text or the whole message","481.515625","703.578125","visible","1"
+"before","en-US","600","focus","3","600","704","20","703.578125","Branch into new chat","513.515625","633.4375","visible","1"
+"before","en-US","390","idle",,"390","494","20","493.578125","Quote selected text or the whole message","271.515625","493.578125","hidden","0"
+"before","en-US","390","hover","0","390","494","20","493.578125","Copy message","207.515625","295.96875","visible","1"
+"before","en-US","390","hover","1","390","494","20","493.578125","Reuse text in composer","239.515625","370.515625","visible","1"
+"before","en-US","390","hover","2","390","494","20","493.578125","Quote selected text or the whole message","271.515625","493.578125","visible","1"
+"before","en-US","390","hover","3","390","494","20","493.578125","Branch into new chat","303.515625","423.4375","visible","1"
+"before","en-US","390","focus","0","390","494","20","493.578125","Copy message","207.515625","295.96875","visible","1"
+"before","en-US","390","focus","1","390","494","20","493.578125","Reuse text in composer","239.515625","370.515625","visible","1"
+"before","en-US","390","focus","2","390","494","20","493.578125","Quote selected text or the whole message","271.515625","493.578125","visible","1"
+"before","en-US","390","focus","3","390","494","20","493.578125","Branch into new chat","303.515625","423.4375","visible","1"
+"after","zh-CN","600","idle",,"600","600","20","541.515625","引用选中文字或整条消息","370.515625","509.515625","hidden","0"
+"after","zh-CN","600","hover","0","600","600","20","541.515625","复制消息","383.515625","445.515625","visible","1"
+"after","zh-CN","600","hover","1","600","600","20","541.515625","回填文字到输入框","371.515625","477.515625","visible","1"
+"after","zh-CN","600","hover","2","600","600","20","541.515625","引用选中文字或整条消息","370.515625","509.515625","visible","1"
+"after","zh-CN","600","hover","3","600","600","20","541.515625","分支到新聊天","457.515625","541.515625","visible","1"
+"after","zh-CN","600","focus","0","600","600","20","541.515625","复制消息","383.515625","445.515625","visible","1"
+"after","zh-CN","600","focus","1","600","600","20","541.515625","回填文字到输入框","371.515625","477.515625","visible","1"
+"after","zh-CN","600","focus","2","600","600","20","541.515625","引用选中文字或整条消息","370.515625","509.515625","visible","1"
+"after","zh-CN","600","focus","3","600","600","20","541.515625","分支到新聊天","457.515625","541.515625","visible","1"
+"after","zh-CN","390","idle",,"390","390","20","331.515625","引用选中文字或整条消息","160.515625","299.515625","hidden","0"
+"after","zh-CN","390","hover","0","390","390","20","331.515625","复制消息","173.515625","235.515625","visible","1"
+"after","zh-CN","390","hover","1","390","390","20","331.515625","回填文字到输入框","161.515625","267.515625","visible","1"
+"after","zh-CN","390","hover","2","390","390","20","331.515625","引用选中文字或整条消息","160.515625","299.515625","visible","1"
+"after","zh-CN","390","hover","3","390","390","20","331.515625","分支到新聊天","247.515625","331.515625","visible","1"
+"after","zh-CN","390","focus","0","390","390","20","331.515625","复制消息","173.515625","235.515625","visible","1"
+"after","zh-CN","390","focus","1","390","390","20","331.515625","回填文字到输入框","161.515625","267.515625","visible","1"
+"after","zh-CN","390","focus","2","390","390","20","331.515625","引用选中文字或整条消息","160.515625","299.515625","visible","1"
+"after","zh-CN","390","focus","3","390","390","20","331.515625","分支到新聊天","247.515625","331.515625","visible","1"
+"after","en-US","600","idle",,"600","600","20","541.515625","Quote selected text or the whole message","287.453125","509.515625","hidden","0"
+"after","en-US","600","hover","0","600","600","20","541.515625","Copy message","357.0625","445.515625","visible","1"
+"after","en-US","600","hover","1","600","600","20","541.515625","Reuse text in composer","346.515625","477.515625","visible","1"
+"after","en-US","600","hover","2","600","600","20","541.515625","Quote selected text or the whole message","287.453125","509.515625","visible","1"
+"after","en-US","600","hover","3","600","600","20","541.515625","Branch into new chat","421.59375","541.515625","visible","1"
+"after","en-US","600","focus","0","600","600","20","541.515625","Copy message","357.0625","445.515625","visible","1"
+"after","en-US","600","focus","1","600","600","20","541.515625","Reuse text in composer","346.515625","477.515625","visible","1"
+"after","en-US","600","focus","2","600","600","20","541.515625","Quote selected text or the whole message","287.453125","509.515625","visible","1"
+"after","en-US","600","focus","3","600","600","20","541.515625","Branch into new chat","421.59375","541.515625","visible","1"
+"after","en-US","390","idle",,"390","390","20","331.515625","Quote selected text or the whole message","77.453125","299.515625","hidden","0"
+"after","en-US","390","hover","0","390","390","20","331.515625","Copy message","147.0625","235.515625","visible","1"
+"after","en-US","390","hover","1","390","390","20","331.515625","Reuse text in composer","136.515625","267.515625","visible","1"
+"after","en-US","390","hover","2","390","390","20","331.515625","Quote selected text or the whole message","77.453125","299.515625","visible","1"
+"after","en-US","390","hover","3","390","390","20","331.515625","Branch into new chat","211.59375","331.515625","visible","1"
+"after","en-US","390","focus","0","390","390","20","331.515625","Copy message","147.0625","235.515625","visible","1"
+"after","en-US","390","focus","1","390","390","20","331.515625","Reuse text in composer","136.515625","267.515625","visible","1"
+"after","en-US","390","focus","2","390","390","20","331.515625","Quote selected text or the whole message","77.453125","299.515625","visible","1"
+"after","en-US","390","focus","3","390","390","20","331.515625","Branch into new chat","211.59375","331.515625","visible","1"
diff --git a/web/src/v2/styles.css b/web/src/v2/styles.css
index 1f074fc7..f78e6504 100644
--- a/web/src/v2/styles.css
+++ b/web/src/v2/styles.css
@@ -403,6 +403,7 @@
   transition: opacity 140ms var(--prayu-ease-out), transform 140ms var(--prayu-ease-out), visibility 140ms;
   visibility: hidden;
 }
+.v2-user-actions .v2-assistant-action-tooltip { left: auto; right: 0; }
 .v2-assistant-action-btn:focus-visible > .v2-assistant-action-tooltip { opacity: 1; transform: translateY(0); visibility: visible; }
 @media (hover: hover) {
   .v2-assistant-action-btn:hover > .v2-assistant-action-tooltip { opacity: 1; transform: translateY(0); visibility: visible; }