fix: 移动端合并改为底部标签直接并入右侧栏（迁移式，删除双工作台堆叠方案）+ 窄屏断点收紧至 768px（不对齐宿主 1024）

README.md

@@ -14,7 +14,7 @@
 - **🌿 Git 面板**：真 diff + VSCode 式 diff tab、懒加载历史、右键暂存/放弃/提交/还原/捡取
 - **🧩 Subagent 页面**：主会话完整 agent 拓扑、点击直达执行记录、实时工具调用轮询、新子代理自动展开
 - **🪟 底部面板**：独立的第二个工作台（与右侧栏同类的标签页），只挤占中间 Agent 输出区、不覆盖左右侧边栏；**首次展开自动开一个新终端**（终端卡片二级设置可关）；右上角 x 一键折叠
-- **📱 移动端**：视口 < 1024px 时（与 DSH 自身的窄屏断点一致）自动合并为**单面板抽屉**——右侧栏与底部面板两个工作台上下同显（中间可拖分隔条，高度与桌面底部面板互通），右上角只剩一枚开关；新会话默认收起，聊天里点文件/外链自动展开，不挤压对话区
+- **📱 移动端**：视口 < 768px（真正的移动端宽度，不对齐宿主 1024 断点）时只显示右侧栏——进入窄屏时底部面板的标签页**直接并入右侧栏标签条**，右上角只剩一枚开关，面板为全宽抽屉；新会话默认收起，聊天里点文件/外链自动展开，不挤压对话区
 - **🔧 分栏工作台**：拖 Tab 拆分/合并分栏（可**跨面板拖 Tab**）、分隔线调比例；右上角持久按钮簇（底栏 + 侧拉 glyph）折叠/展开两个面板；两面板共享拐角双向拖动调节尺寸，拖动 rAF 直写 DOM 保持流畅
 - **🔁 会话隔离**：布局/分栏/Tab/两面板状态按会话持久化（localStorage），陈旧状态自动净化；聊天「产出文件」改在侧边栏打开
 - **⚙️ 声明式设置**：设置页「侧边卡片」分区按注册表渲染功能清单（小卡片网格，高亮 = 启用），每项可独立开/关；二级设置（子代理自动展开、终端工具、底部面板首展自动开终端、沙箱开关等）经齿轮按钮在原生弹窗中编辑
@@ -119,7 +119,7 @@ pnpm watch        # tsdown --watch
 - `.xlsx` 预览不保留单元格样式（SheetJS 社区版限制）；Office/PPTX 预览内联进 client bundle（约 23MB），首次加载较慢
 - 浏览器沙箱无登录态/第三方 Cookie 受限，部分站点登录需走弹窗；被 `X-Frame-Options`/`frame-ancestors` 拒绝嵌入的站点（如 arxiv.org）显示原因面板（含「在浏览器中打开」）；iframe 内部跳转不进后退栈
 - HTML 预览渲染的是已保存文件（不反映未保存草稿）
-- 移动端（<1024px）无底部面板概念：底部面板的标签页并入抽屉下工作台，桌面端的 `bottomOpen` 状态只在宽视口下生效；移动端底部首展自动开终端不触发
+- 移动端（<768px）无底部面板：进入窄屏时其标签页一次性并入右侧栏（迁移后回桌面仍保留在右侧栏），桌面端的底部面板只在宽视口下可用；移动端底部首展自动开终端不触发
 
 ## 🖥️ 平台支持
 

docs/plans/2026-08-12-mobile-layout-design.md

@@ -1,4 +1,4 @@
-# 移动端（窄视口 <1024px）侧边栏布局设计
+# 移动端（窄视口 <768px）侧边栏布局设计
 
 **日期**：2026-08-12
 **状态**：已实施（本文档含实施偏差记录）
@@ -6,68 +6,72 @@
 
 ## 1. 目标
 
-按**视口宽度**（<1024px，与 DSH 宿主 `SIDEBAR_AUTO_COLLAPSE` 一致）切换移动端侧边栏体验：
+按**视口宽度**（<768px——"真正的移动端宽度"，刻意不对齐宿主 1024 断点）切换移动端侧边栏体验：
 
 1. 移动端**不提供底部面板按钮**（右上角按钮簇只剩一枚右侧面板开关）。
-2. **底部面板与右侧面板合并显示**：右侧面板成为全屏抽屉，内部上下堆叠两个工作台——上 = 原右侧栏工作台（`state.splits`），下 = 原底部面板工作台（`state.bottomSplits`），中间可拖分隔条。底部面板浮层（关闭按钮 / 顶部拖动条 / 共享拐角）在移动端整体不渲染。
+2. **合并显示 = 只显示右侧栏**：进入窄屏时底部面板的标签页**直接并入右侧栏**（一次性状态迁移），右侧栏成为全宽抽屉，底部面板浮层整体不存在。
 3. 附带移动端优化：新会话默认收起抽屉、文件/外链打开自动展开、宽度拖动条禁用、布局不挤压（抽屉悬浮）、窄屏标签收窄。
 
 ## 2. 非目标
 
-- 不改持久化 schema：`bottomOpen` / `bottomHeight` / 两棵树字段原样保留，跨断点不迁移状态。
-- 不改桌面行为：≥1024px 时双面板布局与之前完全一致（含布局挤压、拐角、底部首展自动终端）。
+- 不改持久化 schema：`bottomOpen` / `bottomHeight` / `bottomSplits` 字段原样保留。
+- 不改桌面行为：≥768px 时双面板布局与之前完全一致（含布局挤压、拐角、底部首展自动终端）。
 - 不改公开服务 API、PrefsSchema、host 半。
 - 不处理 DSH 详情栏（宿主让步链在 <~996px 自动关闭详情栏，与本改动无交互）。
 
 ## 3. 现状回顾
 
 - `Sidebar.tsx` 渲染两个独立浮层：右侧面板（全高、宽度可拖、布局挤压 `--dsh-sidebar-width`）与底部面板（只挤中间列、高度可拖、右上角按钮簇双按钮、共享拐角）。
-- 底部面板状态字段：`bottomOpen` / `bottomHeight`（钳制 `[BOTTOM_MIN, innerHeight-PANEL_MIN]`）/ `bottomOpenedOnce` / `bottomSplits`。
+- 底部面板状态字段：`bottomOpen` / `bottomHeight`（钳制 `[BOTTOM_MIN, innerHeight-PANEL_MIN]`）/ `bottomOpenedOnce` / `bottomSplits`（独立 split 树，pane/tab id 全局唯一）。
 - 首次展开底部面板自动开终端（`bottomPanelAutoTerminal` pref）。
 
 ## 4. 设计
 
 ### 4.1 断点模块（新 `src/client/breakpoints.ts`）
 
-- `NARROW_MAX_WIDTH = 1024`；`isNarrowWidth(width)` 纯函数；`useNarrowViewport()` hook（初始读 `window.innerWidth`，resize + rAF 节流，`typeof window` 守卫；不用 matchMedia——jsdom 未实现）。
-- CSS 侧配对 `@media (max-width: 1023px)`（1023 ≡ <1024），两端注释互指。
+- `NARROW_MAX_WIDTH = 768`；`isNarrowWidth(width)` 纯函数；`useNarrowViewport()` hook（初始读 `window.innerWidth`，resize + rAF 节流，`typeof window` 守卫；不用 matchMedia——jsdom 未实现）。
+- CSS 侧配对 `@media (max-width: 767px)`（767 ≡ <768），两端注释互指。
+- 刻意**不对齐**宿主 `SIDEBAR_AUTO_COLLAPSE = 1024`：1024px 窗口（小笔记本、分屏）保留桌面双面板；只有手机/竖屏平板才进移动布局。
 
-### 4.2 合并布局（`Sidebar.tsx` + `split-pane.tsx` `MobileWorkbench`）
+### 4.2 合并 = 底部标签并入右侧栏（状态迁移）
 
-- 窄屏下：面板宽度 `100vw`（全屏抽屉）；`--dsh-sidebar-*` 布局变量恒 0（抽屉悬浮覆盖，不挤压 AppFrame）；宽度拖动条、底部浮层、`bottomClose`、拐角、底部面板按钮全部不渲染。
-- `MobileWorkbench`：column flex → 上区 `Workbench(state.splits)`（flex:1）→ 分隔条（复用 `.dividerCol` 命中区 + hairline）→ 下区 `Workbench(state.bottomSplits)`（高度 = `state.bottomHeight`，`flex:none`）。
-- **下区高度复用 `bottomHeight`**：桌面底部面板高度语义延续到移动端；移动端拖分隔条写回同一字段并持久化，回桌面后一致。
-- 分隔条拖动：镜像现有面板拖动模式（pointer capture + rAF 批处理 DOM 直写 + 松手一次 `setBottomHeight` commit），避免终端/编辑器逐帧重渲染。
-- 两个工作台**始终渲染**（空底部树显示欢迎卡片）；跨工作台拖 Tab 由既有跨树 `moveTabToEdge` / `moveTab` 支持。
-- 底部树 tab 的 `visible` 在窄屏 = `panelOpen && active`（抽屉开合决定），不再看 `bottomOpen`。
+- **新 reducer `migrateBottomTabs(state)`**（`state.ts`）：
+  - 底部树所有标签按深度优先序**追加到右侧树第一个 leaf**（`firstLeaf(splits)`）的标签条；
+  - 底部树清空（结构保留——桌面端回显欢迎卡片）、`bottomOpen=false`、`activePane` 指向右侧树第一个 leaf（保证迁移后新开的标签落在可见面板）；
+  - 幂等：底部无标签且面板已关且 activePane 不在底部树时返回同一引用。
+- **Sidebar 触发 effect**：`narrow && sessionId 已定义` 时执行（覆盖：窄屏挂载、会话切换、桌面→窄屏过渡）；幂等性保证其自然收敛，不循环。
+- 迁移是**永久**的（符合"直接丢到右侧栏中"）：回桌面后标签仍留在右侧树，底部面板为空（欢迎卡片）；用户可在桌面重新往底部面板开标签，再进窄屏会再次迁移。
+- 迁移后右侧栏用**现有 `Workbench` 原样渲染**——零视图层特判、零 action 路由修补（标签真实住在右侧树，close/activate/drag 全部走原路径）。
 
-### 4.3 行为修正
+### 4.3 窄屏渲染（`Sidebar.tsx`）
+
+- 面板宽度 `100vw`（全宽抽屉）；`--dsh-sidebar-*` 布局变量恒 0（抽屉悬浮，不挤压 AppFrame）；宽度拖动条、底部浮层、`bottomClose`、拐角、底部面板按钮全部不渲染。
+- `visible` 语义回到原始：底部树只在桌面底部面板场景（`bottomOpen && active`）——窄屏下底部树为空且不渲染。
+- 底部首展自动终端 effect 加 `narrow` 守卫。
+
+### 4.4 行为修正
 
 - `state.ts` `loadState`：窄屏新会话默认 `panelOpen=false`（首开才生效；用户手动展开后照常持久化）。
 - `service.ts` `openTab`：窄屏且 seed 带 `path`/`url` 且面板收起 → 自动展开抽屉（dedupe-focus 分支同样生效）；纯类型打开不展开；宽屏行为不变。
-- 底部首展自动终端 effect 加 `narrow` 守卫（桌面专属行为）。
-- 子代理自动展开 / jump-back 不动（展开 `panelOpen` = 展开抽屉，语义正确）。
 
-### 4.4 样式（`sidebar.module.css`）
+### 4.5 样式（`sidebar.module.css`）
 
-- `@media (max-width: 1023px)`：开放面板标签条预留宽度 72px → 40px（按钮簇只剩一枚）；`.tab` min/max 宽收窄（48/128px）。
-- 新增 `.mobileWorkbench` / `.mobilePane` / `.mobilePaneBottom`；分隔条复用 `.dividerCol`。
+- `@media (max-width: 767px)`：开放面板标签条预留宽度 72px → 40px（按钮簇只剩一枚）；`.tab` min/max 宽收窄（48/128px）。
 
-### 4.5 测试
+### 4.6 测试
 
-- `tests/breakpoints.spec.ts`：断点边界。
-- `tests/service.spec.ts`：窄屏 auto-expand 5 例（path/url 展开、类型不展开、宽屏不展开、dedupe 聚焦仍展开）。
-- `tests/unit.spec.ts`：窄屏新会话默认收起（stub `window.innerWidth=390`，try/finally 还原）。
-- `tests/mobile-workbench.spec.tsx`：双树并显 + 分隔条 + 底部高度（renderToString 结构断言）。
-- 分隔条拖动 = 指针捕获逻辑，人工验证（与桌面拖动同策略）；store 钳制由既有 `setBottomHeight` 测试覆盖。
+- `tests/breakpoints.spec.ts`：断点边界（767 窄 / 768 宽；1024 明确为宽）。
+- `tests/unit.spec.ts`：`migrateBottomTabs` 4 例（并入第一 leaf 且底部清空/面板关/activePane 重指、右树为 split 时并入最左 leaf、幂等性、空底部树但 activePane 在底部树时重指）+ 窄屏新会话默认收起（stub `window.innerWidth=390`）。
+- `tests/service.spec.ts`：窄屏 auto-expand 5 例（390 < 768 仍窄）。
 
 ## 5. 边界情况
 
-- 跨断点往返：状态零迁移；桌面 `bottomOpen=false` 但底部树有标签的会话，移动端仍显示（合并语义），回桌面仍隐藏。
-- 底部高度越界：渲染直接用 `state.bottomHeight`（store 写入已钳制）；拖动中按面板体高度钳制，松手再走 store 钳制。
+- 迁移触发：窄屏挂载 / 会话切换 / 桌面→窄屏过渡，均由同一 effect 覆盖；幂等保证收敛。
+- 迁移后新开标签：`activePane` 已重指右侧树第一 leaf，`openTabInActivePane` 必落在可见面板（含"空底部树但 activePane 指向它"的陈旧指针场景）。
+- 跨断点往返：迁移永久；桌面底部面板空显欢迎卡片；`bottomHeight` 不受影响。
 - jsdom 兼容：hook 不用 matchMedia；既有测试 stub `innerWidth=1024` 自动走桌面路径，零行为变化。
 
 ## 6. 实施偏差记录
 
-- 计划时考虑过「空底部树隐藏 + 拖 Tab 创建」方案，最终采用**始终渲染两工作台**（用户确认的选项语义：上下并显 + 可调分隔；空底部树显示欢迎卡片，发现性更好）。
-- 计划时考虑过 matchMedia 方案，最终用 resize + rAF（jsdom 兼容，仓库既有拖动模式同款）。
+- **v1（已提交 b391ebf，用户反馈推翻）**：合并 = 单面板内上下堆叠两个工作台（`MobileWorkbench` + 可拖分隔条，高度复用 `bottomHeight`），断点 1024（对齐宿主）。用户明确：合并 = 只显示右侧栏、底部标签直接丢进右侧栏；窄屏 = 真窄屏、不对齐 1024。
+- **v2（本文档，最终形态）**：删除 `MobileWorkbench`（组件 + CSS + spec），改为 `migrateBottomTabs` 状态迁移 + 现有 `Workbench` 渲染；断点 768。`bottomHeight` 不再参与移动端布局（仅桌面底部面板使用）。

src/client/Sidebar.tsx

@@ -17,13 +17,13 @@
  * terminal; editors open from the explorer). Tabs live in one tree only —
  * they never cross panels; only the panel sizes drag against each other.
  *
- * Narrow (mobile, <1024px) viewports collapse the two panels into one: the
- * right panel becomes a full-width drawer holding BOTH workbenches stacked
- * (MobileWorkbench, see split-pane.tsx), the bottom panel and its toggle
- * button disappear, and the layout push is disabled (the drawer floats).
- * Crossing the breakpoint never rewrites per-session state — bottomOpen /
- * bottomHeight / both trees survive untouched, so desktop restores exactly
- * what the user left.
+ * Narrow (mobile, <768px) viewports show ONLY the right sidebar: entering
+ * narrow migrates the bottom panel's tabs INTO the right tree
+ * (migrateBottomTabs) — one workbench, the bottom tabs thrown into its
+ * strips. The right panel becomes a full-width drawer, the bottom panel
+ * and its toggle button disappear, and the layout push is disabled (the
+ * drawer floats). Widening does not migrate back: the tabs keep living in
+ * the right tree.
  */
 import { useCallback, useEffect, useMemo, useRef, useState, type ReactNode } from 'react'
 import { useSyncExternalStore } from 'react'
@@ -31,13 +31,13 @@ import clsx from 'clsx'
 import { IconCloseFill14, Tooltip } from '@deepseek-ai/dsh-client-ui-primitives'
 import type { Context, SidebarConversation, SidebarSessionList } from '../context-types.ts'
 import {
-  BOTTOM_MIN, PANEL_MIN, agentUuidOf, closeTab, firstLeaf, isAgentTabId, leafWithTab, mapLeaf, moveTab, moveTabToEdge, openDiffTab,
+  BOTTOM_MIN, PANEL_MIN, agentUuidOf, closeTab, firstLeaf, isAgentTabId, leafWithTab, mapLeaf, migrateBottomTabs, moveTab, moveTabToEdge, openDiffTab,
   reconcileAgentTerminals,
   resizeSplitIn, setBottomHeight, setWidth, toggleBottomPanel, toggleExpanded, togglePanel,
   type DropZone, type SidebarState, type SidebarStore, type SidebarTab, type SplitNode,
 } from './state.ts'
 import { IconPanelBottomOutline16, IconPanelRightOutline16 } from './icons.tsx'
-import { MobileWorkbench, Workbench, type WorkbenchActions } from './split-pane.tsx'
+import { Workbench, type WorkbenchActions } from './split-pane.tsx'
 import { useNarrowViewport } from './breakpoints.ts'
 import type { NewTabOption } from './TabBar.tsx'
 import type { TabDragPayload } from './TabBar.tsx'
@@ -106,10 +106,11 @@ export function Sidebar(props: { ctx: Context; store: SidebarStore }) {
   // Narrow (mobile) viewports collapse the two panels into one: the right
   // panel becomes a full-width drawer holding BOTH workbenches, the bottom
   // panel (and its toggle button) disappears, and the layout push is
-  // disabled (the drawer floats over the app shell). Crossing the
-  // breakpoint never rewrites the per-session state — bottomOpen /
-  // bottomHeight / both trees survive untouched, so desktop restores
-  // exactly what the user left.
+  // disabled (the drawer floats over the app shell). Entering narrow
+  // MIGRATES the bottom tree's tabs into the right tree (migrateBottomTabs)
+  // — the merged display is the right sidebar alone, the bottom tabs thrown
+  // into its strips. Widening never rewrites the migrated state: the tabs
+  // keep living in the right tree.
   const narrow = useNarrowViewport()
 
   // Current conversation (the sessions list feed).
@@ -130,6 +131,18 @@ export function Sidebar(props: { ctx: Context; store: SidebarStore }) {
   const sessionId = snapshot.sessionId
   const summaryCwd = sessionId === undefined ? undefined : sessionList.byId[sessionId]?.cwd
 
+  /**
+   * Bottom-panel merge on narrow viewports: whenever a session is current
+   * while narrow (mount, session switch, or a desktop→narrow transition),
+   * throw the bottom tree's tabs into the right tree. Idempotent — after
+   * the first migration the bottom tree is empty and the reducer returns
+   * the same reference, so this effect settles immediately.
+   */
+  useEffect(() => {
+    if (!narrow || sessionId === undefined) return
+    store.reduce(migrateBottomTabs)
+  }, [narrow, sessionId, store])
+
   // While the session's header is still hydrating (or the session is blank),
   // the list summary may carry no cwd; ask the host once (it falls back to
   // the process cwd) so the explorer root and terminal cwd are real from
@@ -528,10 +541,7 @@ export function Sidebar(props: { ctx: Context; store: SidebarStore }) {
       onReferenceFile={referenceInChat}
       ctx={ctx}
       store={store}
-      // On narrow viewports BOTH trees live in the one drawer, so the bottom
-      // tree's visibility is the drawer's (panelOpen), not the bottom
-      // panel's — the bottom panel itself does not exist there.
-      visible={narrow ? state.panelOpen && active : bottom ? state.bottomOpen && active : state.panelOpen && active}
+      visible={bottom ? state.bottomOpen && active : state.panelOpen && active}
       onSubagentJump={(childSessionId) => { subagentJumpRef.current = childSessionId }}
       onOpenDiff={(diffTab) => { store.reduce(s => openDiffTab(s, paneId, diffTab)) }}
     />
@@ -617,19 +627,6 @@ export function Sidebar(props: { ctx: Context; store: SidebarStore }) {
             />
           )}
         <div className={css.panelBody}>
-          {narrow
-            ? (
-              <MobileWorkbench
-                state={state}
-                newTabOptions={buildNewTabOptions(state, ctx, { sessionId, cwd })}
-                actions={actions}
-                onNewTab={onNewTab}
-                renderTab={(tab, active, paneId) => renderTab(tab, active, paneId, true)}
-                getTabIcon={tabIconOf}
-                onBottomHeightCommit={(height) => { store.reduce(s => setBottomHeight(s, height)) }}
-              />
-            )
-            : (
           <Workbench
             state={state}
             newTabOptions={buildNewTabOptions(state, ctx, { sessionId, cwd })}
@@ -638,7 +635,6 @@ export function Sidebar(props: { ctx: Context; store: SidebarStore }) {
             renderTab={renderTab}
             getTabIcon={tabIconOf}
           />
-            )}
         </div>
       </div>
       {/*

src/client/breakpoints.ts

@@ -1,18 +1,19 @@
 /**
  * Narrow-viewport ("mobile") breakpoint for the sidebar. Width-based, shared
  * by the layout logic (JS) and the style gates (CSS). The CSS side pairs
- * with this file via `@media (max-width: 1023px)` rules (sidebar.module.css)
- * — 1023px ≡ widths below NARROW_MAX_WIDTH, documented at both ends.
+ * with this file via `@media (max-width: 767px)` rules (sidebar.module.css)
+ * — 767px ≡ widths below NARROW_MAX_WIDTH, documented at both ends.
  *
- * The value matches the DSH app shell's own narrow breakpoint
- * (SIDEBAR_AUTO_COLLAPSE = 1024, ui-layout/columns.ts), so the sidebar's
- * mobile layout switches at exactly the width where the host app collapses
- * its own sidebar to the rail.
+ * "Real narrow" on purpose: the mobile layout (one full-screen drawer, the
+ * bottom panel's tabs merged into the right sidebar) is a phone / portrait
+ * tablet experience. The value is deliberately NOT aligned to the DSH app
+ * shell's own 1024px breakpoint — 1024px windows (small laptops, split
+ * panes) keep the desktop two-panel layout.
  */
 import { useEffect, useState } from 'react'
 
-/** Viewport widths strictly below this are "mobile" (paired CSS: max-width: 1023px). */
-export const NARROW_MAX_WIDTH = 1024
+/** Viewport widths strictly below this are "mobile" (paired CSS: max-width: 767px). */
+export const NARROW_MAX_WIDTH = 768
 
 /** Whether a viewport width is narrow (mobile). */
 export function isNarrowWidth(width: number): boolean {

src/client/sidebar.module.css

@@ -264,38 +264,6 @@
   display: flex;
 }
 
-/* The narrow-viewport workbench (MobileWorkbench): BOTH workbench trees
-   stacked in the one drawer — the right panel's tree flexes after the
-   fixed-height bottom tree, with a draggable divider (the .dividerCol
-   hit-strip + hairline) between them. */
-.mobileWorkbench {
-  flex: 1;
-  min-width: 0;
-  min-height: 0;
-  display: flex;
-  flex-direction: column;
-}
-
-.mobilePane {
-  position: relative;
-  display: flex;
-  min-width: 0;
-  min-height: 0;
-}
-
-/* The bottom tree of the merged layout: fixed height (state.bottomHeight),
-   flex: none so the top tree takes the remainder. */
-.mobilePaneBottom {
-  flex: none;
-}
-
-/* The divider of the merged layout sits between the two panes; .dividerCol
-   already supplies the 7px hit strip, row-resize cursor and hairline. */
-.mobileWorkbench > .dividerCol {
-  flex: none;
-  margin: 0;
-}
-
 .split {
   flex: 1;
   min-width: 0;
@@ -1899,13 +1867,13 @@
 
 /* ── Narrow (mobile) viewport ──────────────────────────────────────────── */
 
-/* Pairs with NARROW_MAX_WIDTH = 1024 in src/client/breakpoints.ts: widths
-   strictly below 1024px (i.e. max-width: 1023px) switch the sidebar to the
-   mobile layout — one drawer holding both workbenches, one toggle button.
-   The structural switches (which panels render, the merged MobileWorkbench)
-   are JS-driven via useNarrowViewport; this block only adapts the pure
-   style details. */
-@media (max-width: 1023px) {
+/* Pairs with NARROW_MAX_WIDTH = 768 in src/client/breakpoints.ts: widths
+   strictly below 768px (i.e. max-width: 767px) switch the sidebar to the
+   mobile layout — one full-screen drawer (the bottom panel's tabs were
+   migrated into the right tree), one toggle button. The structural
+   switches (which panels render, the migration) are JS-driven via
+   useNarrowViewport; this block only adapts the pure style details. */
+@media (max-width: 767px) {
   /* The toggle cluster holds a single button on narrow viewports (the
      bottom panel button is not rendered), so the open panel's tab strip
      reserves 40px instead of the desktop 72px — the tabs and + menu still

src/client/split-pane.tsx

@@ -12,7 +12,7 @@
 import { Fragment, useEffect, useRef, useState } from 'react'
 import type { ReactNode } from 'react'
 import clsx from 'clsx'
-import { BOTTOM_MIN, type SidebarState, type SidebarTab, type SplitNode } from './state.ts'
+import type { SidebarState, SidebarTab, SplitNode } from './state.ts'
 import type { DropZone } from './state.ts'
 import { TabBar, type NewTabOption, parseDrag, type TabDragPayload } from './TabBar.tsx'
 import css from './sidebar.module.css'
@@ -290,114 +290,3 @@ export function Workbench(props: {
     </div>
   )
 }
-
-/**
- * The narrow-viewport workbench: BOTH workbench trees stacked in one panel —
- * the right panel's tree on top, the bottom panel's tree below, with a
- * draggable divider between them (the desktop "two panels" collapse into one
- * on mobile; see the breakpoint module). The bottom tree's height is the
- * shared `state.bottomHeight` — the same field the desktop bottom panel uses
- * — so a height set on mobile carries over to the desktop bottom panel and
- * vice versa. Tabs stay in their own trees; the cross-tree drag logic
- * (state.moveTabToEdge / moveTab) already handles moving a tab between the
- * two panes.
- *
- * The divider writes the height DIRECTLY to the DOM while dragging (the top
- * tree flexes after the fixed-height bottom tree), committing to the store
- * once on release — the same pattern as the desktop panel drags, so
- * terminals/editors never re-render on every pointer move.
- */
-export function MobileWorkbench(props: {
-  state: SidebarState
-  actions: WorkbenchActions
-  newTabOptions: NewTabOption[]
-  onNewTab: (optionId: string) => void
-  renderTab: (tab: SidebarTab, active: boolean, paneId: string) => ReactNode
-  getTabIcon?: (tab: SidebarTab) => ReactNode
-  /** Commit a new bottom-tree height (store-backed, clamped by setBottomHeight). */
-  onBottomHeightCommit: (height: number) => void
-}) {
-  const {
-    state, actions, newTabOptions, onNewTab, renderTab, getTabIcon, onBottomHeightCommit,
-  } = props
-  const bottomRef = useRef<HTMLDivElement | null>(null)
-  const dividerRef = useRef<HTMLDivElement | null>(null)
-  const dragRef = useRef({ startY: 0, startHeight: 0 })
-  const [dragging, setDragging] = useState(false)
-  // One DOM write per frame (like the desktop panel drags): pointer events
-  // outrun the display refresh, and each write reflows the pane content.
-  const dragFrame = useRef<number | null>(null)
-  const pending = useRef<number | null>(null)
-  const scheduleHeight = (height: number): void => {
-    pending.current = height
-    if (dragFrame.current !== null) return
-    dragFrame.current = requestAnimationFrame(() => {
-      dragFrame.current = null
-      const next = pending.current
-      if (next !== null) bottomRef.current?.style.setProperty('height', `${next}px`)
-    })
-  }
-
-  return (
-    <div className={css.mobileWorkbench}>
-      <div className={css.mobilePane}>
-        <Workbench
-          state={state}
-          newTabOptions={newTabOptions}
-          actions={actions}
-          onNewTab={onNewTab}
-          renderTab={renderTab}
-          getTabIcon={getTabIcon}
-        />
-      </div>
-      <div
-        ref={dividerRef}
-        className={clsx(css.divider, css.dividerCol, dragging && css.dividerActive)}
-        onPointerDown={(event) => {
-          event.preventDefault()
-          event.currentTarget.setPointerCapture(event.pointerId)
-          dragRef.current = { startY: event.clientY, startHeight: state.bottomHeight }
-          setDragging(true)
-        }}
-        onPointerMove={(event) => {
-          if (!event.currentTarget.hasPointerCapture(event.pointerId)) return
-          const { startY, startHeight } = dragRef.current
-          const box = dividerRef.current?.parentElement?.getBoundingClientRect()
-          const bodyHeight = box === undefined || box.height === 0 ? window.innerHeight : box.height
-          const next = Math.min(
-            Math.max(BOTTOM_MIN, startHeight + (event.clientY - startY)),
-            Math.max(BOTTOM_MIN, bodyHeight - BOTTOM_MIN),
-          )
-          scheduleHeight(next)
-        }}
-        onPointerUp={(event) => {
-          if (!event.currentTarget.hasPointerCapture(event.pointerId)) return
-          event.currentTarget.releasePointerCapture(event.pointerId)
-          if (dragFrame.current !== null) {
-            cancelAnimationFrame(dragFrame.current)
-            dragFrame.current = null
-          }
-          const final = pending.current
-          pending.current = null
-          setDragging(false)
-          if (final !== null) onBottomHeightCommit(final)
-        }}
-      />
-      <div
-        ref={bottomRef}
-        className={clsx(css.mobilePane, css.mobilePaneBottom)}
-        style={{ height: state.bottomHeight }}
-      >
-        <Workbench
-          state={state}
-          tree={state.bottomSplits}
-          newTabOptions={newTabOptions}
-          actions={actions}
-          onNewTab={onNewTab}
-          renderTab={renderTab}
-          getTabIcon={getTabIcon}
-        />
-      </div>
-    </div>
-  )
-}

src/client/state.ts

@@ -206,6 +206,44 @@ export function firstLeaf(node: SplitNode): SidebarLeaf {
   return firstLeaf(node.children[0]!)
 }
 
+/** Empty every leaf of a tree (the bottom tree after its tabs migrate out). */
+function clearAllTabs(node: SplitNode): SplitNode {
+  if (node.kind === 'leaf') return { ...node, tabs: [], active: null }
+  return { ...node, children: node.children.map(clearAllTabs) }
+}
+
+/**
+ * Narrow-viewport migration: the bottom panel's tabs are thrown INTO the
+ * right sidebar — the "merged display" on mobile is the right panel alone,
+ * whose tab strips now carry the bottom tree's tabs (depth-first order,
+ * appended to the right tree's FIRST leaf). The bottom tree is emptied (its
+ * structure stays — the desktop bottom panel re-renders its welcome cards)
+ * and the panel closes. The active pane moves to the right tree's first
+ * leaf so every new tab lands in the visible panel.
+ *
+ * Idempotent: a bottom tree with no tabs and a closed panel returns the
+ * same reference. Runs when the viewport enters narrow (see the Sidebar
+ * shell); migrating is permanent for the session — the tabs now live in the
+ * right tree, exactly like the user "threw them in".
+ */
+export function migrateBottomTabs(state: SidebarState): SidebarState {
+  const bottomTabs = allLeaves(state.bottomSplits).flatMap(leaf => leaf.tabs)
+  const activeInBottom = state.activePane !== null && treeHasId(state.bottomSplits, state.activePane)
+  if (bottomTabs.length === 0 && !state.bottomOpen && !activeInBottom) return state
+  const target = firstLeaf(state.splits)
+  return {
+    ...state,
+    activePane: target.id,
+    bottomOpen: false,
+    splits: bottomTabs.length > 0
+      ? mapLeaf(state.splits, target.id, leaf => {
+        leaf.tabs = [...leaf.tabs, ...bottomTabs]
+      })
+      : state.splits,
+    bottomSplits: bottomTabs.length > 0 ? clearAllTabs(state.bottomSplits) : state.bottomSplits,
+  }
+}
+
 /** Find the leaf containing a tab id, if any. */
 export function leafWithTab(node: SplitNode, tabId: string): SidebarLeaf | undefined {
   if (node.kind === 'leaf') {

tests/breakpoints.spec.ts

@@ -1,21 +1,24 @@
 /**
  * Narrow-viewport breakpoint tests: the boundary the mobile sidebar layout
- * keys off (paired with the CSS @media (max-width: 1023px) gates in
- * sidebar.module.css — 1023px ≡ widths strictly below NARROW_MAX_WIDTH).
+ * keys off (paired with the CSS @media (max-width: 767px) gates in
+ * sidebar.module.css — 767px ≡ widths strictly below NARROW_MAX_WIDTH).
+ * Deliberately NOT aligned to the DSH app shell's 1024px breakpoint: the
+ * mobile layout is for real narrow screens (phones / portrait tablets).
  */
 import { describe, expect, it } from 'vitest'
 import { isNarrowWidth, NARROW_MAX_WIDTH } from '../src/client/breakpoints.ts'
 
 describe('narrow-viewport breakpoint', () => {
   it('treats widths below NARROW_MAX_WIDTH as narrow (mobile)', () => {
-    expect(NARROW_MAX_WIDTH).toBe(1024)
+    expect(NARROW_MAX_WIDTH).toBe(768)
     expect(isNarrowWidth(320)).toBe(true)
     expect(isNarrowWidth(390)).toBe(true)
-    expect(isNarrowWidth(768)).toBe(true)
-    expect(isNarrowWidth(1023)).toBe(true)
+    expect(isNarrowWidth(600)).toBe(true)
+    expect(isNarrowWidth(767)).toBe(true)
   })
 
   it('treats NARROW_MAX_WIDTH and above as wide (desktop)', () => {
+    expect(isNarrowWidth(768)).toBe(false)
     expect(isNarrowWidth(1024)).toBe(false)
     expect(isNarrowWidth(1280)).toBe(false)
     expect(isNarrowWidth(1920)).toBe(false)

tests/mobile-workbench.spec.tsx

@@ -1,68 +0,0 @@
-/**
- * MobileWorkbench tests: the narrow-viewport merged workbench — BOTH trees
- * (right + bottom) stacked in one panel with a draggable divider between
- * them, the bottom tree at the shared state.bottomHeight. Structure
- * assertions via renderToString (the repo's component-test pattern). The
- * divider drag itself is pointer-capture logic — exercised manually, like
- * the desktop panel drags; the store clamp it commits through
- * (setBottomHeight) is unit-tested in unit.spec.ts.
- */
-import { describe, expect, it } from 'vitest'
-import { renderToString } from 'react-dom/server'
-import { MobileWorkbench, type WorkbenchActions } from '../src/client/split-pane.tsx'
-import { makeDefaultState } from '../src/client/state.ts'
-
-const noopActions: WorkbenchActions = {
-  closeTab: () => {},
-  activateTab: () => {},
-  focusPane: () => {},
-  moveTabToEdge: () => {},
-  moveTabBefore: () => {},
-  resizeSplit: () => {},
-}
-
-describe('MobileWorkbench (narrow merged layout)', () => {
-  it('renders BOTH trees stacked, with the divider and the shared bottom height', () => {
-    const state = makeDefaultState()
-    // A terminal tab in the bottom tree (a desktop bottom-panel session).
-    const bottomPane = state.bottomSplits as { tabs: Array<{ id: string; type: string; title: string }> }
-    bottomPane.tabs = [{ id: 'tab:b1', type: 'terminal', title: 'Terminal' }]
-    const html = renderToString((
-      <MobileWorkbench
-        state={state}
-        actions={noopActions}
-        newTabOptions={[]}
-        onNewTab={() => {}}
-        renderTab={(tab) => <div data-testid={`tab-${tab.id}`}>{tab.title}</div>}
-        onBottomHeightCommit={() => {}}
-      />
-    ))
-    // The right tree's default explorer tab renders (tab strip).
-    expect(html).toContain('Explorer')
-    // The bottom tree's terminal tab renders — the merge shows both trees.
-    expect(html).toContain('Terminal')
-    // The divider sits between the two workbenches.
-    expect(html).toContain('divider')
-    // The bottom pane carries the shared bottomHeight (the desktop bottom
-    // panel's height field drives the mobile bottom tree's height).
-    expect(html).toContain(`height:${state.bottomHeight}px`)
-  })
-
-  it('renders an empty bottom tree with its welcome cards (both workbenches always visible)', () => {
-    const state = makeDefaultState()
-    const html = renderToString((
-      <MobileWorkbench
-        state={state}
-        actions={noopActions}
-        newTabOptions={[{ id: 'explorer', label: 'Explorer' }, { id: 'terminal', label: 'Terminal' }]}
-        onNewTab={() => {}}
-        renderTab={() => null}
-        onBottomHeightCommit={() => {}}
-      />
-    ))
-    // The top tree's explorer TAB and the empty bottom pane's welcome cards
-    // both render (each option card carries its label).
-    expect(html).toContain('Explorer')
-    expect(html).toContain('Terminal')
-  })
-})

tests/unit.spec.ts

@@ -4,7 +4,7 @@ import { parseLogLines, parsePorcelainZ } from '../src/git.ts'
 import { parseUnifiedDiff } from '../src/client/DiffView.tsx'
 import {
   activateTab, allLeaves, BOTTOM_DEFAULT, BOTTOM_MIN, closeTab, createSidebarStore, defaultWidthFor, insertLeafAt, makeDefaultState,
-  moveTab, moveTabToEdge, openDiffTab, openTabInActivePane, patchTab, reconcileAgentTerminals, resizeSplit, resizeSplitIn, sanitizeState, setBottomHeight, splitPane, tabOpenIn, toggleBottomPanel, toggleExpanded, togglePanel,
+  migrateBottomTabs, moveTab, moveTabToEdge, openDiffTab, openTabInActivePane, patchTab, reconcileAgentTerminals, resizeSplit, resizeSplitIn, sanitizeState, setBottomHeight, splitPane, tabOpenIn, toggleBottomPanel, toggleExpanded, togglePanel,
   type SidebarState, type SidebarTab, type SplitNode,
 } from '../src/client/state.ts'
 import { loadPrefs, type SidebarSettingsClient } from '../src/client/prefs.ts'
@@ -550,6 +550,66 @@ describe('sidebar state', () => {
     }
   })
 
+  // ── Narrow-viewport merge (bottom tabs thrown into the right sidebar) ──
+
+  it('migrateBottomTabs throws the bottom tree tabs into the right tree’s FIRST leaf', () => {
+    let s = state()
+    s = toggleBottomPanel(s)
+    const bottomPane = (s.bottomSplits as { id: string }).id
+    // Two bottom tabs in their own pane; the right pane holds explorer.
+    s = openTabInActivePane({ ...s, activePane: bottomPane }, { id: 'terminal:1', type: 'terminal', title: 'T1' })
+    s = openTabInActivePane(s, { id: 'terminal:2', type: 'terminal', title: 'T2' })
+    const migrated = migrateBottomTabs(s)
+    // All tabs now live in the right tree's first leaf, bottom tabs appended.
+    expect((migrated.splits as { tabs: SidebarTab[] }).tabs.map(t => t.id))
+      .toEqual([expect.stringMatching(/^tab:/), 'terminal:1', 'terminal:2'])
+    // The bottom tree is emptied (structure stays), the panel closes, and
+    // new tabs land in the right tree.
+    expect((migrated.bottomSplits as { tabs: SidebarTab[] }).tabs).toHaveLength(0)
+    expect(migrated.bottomOpen).toBe(false)
+    expect(migrated.activePane).toBe((migrated.splits as { id: string }).id)
+    // The migrated tabs are fully functional: closing one works through the
+    // right tree.
+    expect(tabOpenIn(migrated, 'terminal:1')).toBe(true)
+    expect(tabOpenIn(closeTab(migrated, migrated.activePane!, 'terminal:1'), 'terminal:1')).toBe(false)
+  })
+
+  it('migrateBottomTabs appends into the FIRST leaf when the right tree is a split', () => {
+    let s = state()
+    s = splitPane(s, 'row') // splits the active pane into two leaves
+    s = toggleBottomPanel(s)
+    const bottomPane = (s.bottomSplits as { id: string }).id
+    s = openTabInActivePane({ ...s, activePane: bottomPane }, { id: 'terminal:9', type: 'terminal', title: 'T9' })
+    const migrated = migrateBottomTabs(s)
+    // The first (leftmost) leaf carries the bottom tab; the second leaf
+    // keeps its own tabs untouched.
+    const leaves = allLeaves(migrated.splits)
+    expect(leaves[0]!.tabs.map(t => t.id)).toContain('terminal:9')
+    expect(allLeaves(migrated.bottomSplits).flatMap(l => l.tabs)).toHaveLength(0)
+  })
+
+  it('migrateBottomTabs is idempotent (same reference) once the bottom tree is empty and closed', () => {
+    const s = state()
+    expect(migrateBottomTabs(s)).toBe(s)
+    // With the panel open but no tabs, the migration only closes the panel.
+    const open = toggleBottomPanel(s)
+    const migrated = migrateBottomTabs(open)
+    expect(migrated).not.toBe(open)
+    expect(migrated.bottomOpen).toBe(false)
+    expect(migrateBottomTabs(migrated)).toBe(migrated)
+  })
+
+  it('migrateBottomTabs repoints an active pane that lives in the bottom tree', () => {
+    let s = state()
+    const bottomPane = (s.bottomSplits as { id: string }).id
+    s = { ...s, activePane: bottomPane } // empty bottom pane, panel closed
+    const migrated = migrateBottomTabs(s)
+    expect(migrated.activePane).toBe((migrated.splits as { id: string }).id)
+    // A tab opened after the migration lands in the VISIBLE right tree.
+    const landed = openTabInActivePane(migrated, { id: 'git', type: 'git' as const, title: 'Git' })
+    expect((landed.splits as { tabs: SidebarTab[] }).tabs.map(t => t.type)).toContain('git')
+  })
+
   it('openTabInActivePane lands in the bottom tree when the active pane lives there', () => {
     let s = state()
     s = toggleBottomPanel(s)