diff --git a/AGENTS.md b/AGENTS.md
index 4ceb9bf..df30631 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -604,7 +604,7 @@ interface OpenTabSeed {
 
 任意 tab（内置或插件注册的）可拖出侧边栏，成为悬浮在主会话区域上的**自由窗口**（free window）：
 
-- **拖出**：把标签栏的 tab 拖到**主会话区域**（conversation 列）上——虚线提示浮层标记落区，松开即浮动（`floatTab` reducer：tab 从 pane **移动**进 `SidebarState.floats`，窗口以默认尺寸 480×360 居中于松点、钳入视口；清空的 pane 折叠）。检测在 `src/client/Sidebar.tsx`：document 捕获 `dragover`/`drop`，以 `body[data-dsh-tab-dragging]`（TabBar 维护）门控，目标矩形取 `#root [data-slot="conversation"]` 的父列；窄视口（合并抽屉）禁用手势。tab 右键菜单的**「移动到自由窗口」**（两面板共用 TabBar，一处生效）始终可用，窗口落在会话列中心。
+- **拖出**：把标签栏的 tab 拖到**主会话区域**（conversation 列）上——虚线提示浮层标记落区，松开即浮动（`floatTab` reducer：tab 从 pane **移动**进 `SidebarState.floats`，窗口以默认尺寸 390×780（手机竖屏比例，创建时先按视口减 24px 钳高）居中于松点、钳入视口；清空的 pane 折叠）。检测在 `src/client/Sidebar.tsx`：document 捕获 `dragover`/`drop`，以 `body[data-dsh-tab-dragging]`（TabBar 维护）门控，目标矩形取 `#root [data-slot="conversation"]` 的父列；窄视口（合并抽屉）禁用手势。tab 右键菜单的**「移动到自由窗口」**（两面板共用 TabBar，一处生效）始终可用，窗口落在会话列中心。
 - **窗口操作**（`src/client/FreeWindow.tsx`，渲染在 `[data-dsh-panel-host]` 内、z-index 42）：头部 pointer 拖动移动（rAF 直写 DOM + 松手提交 store 的面板拖拽模式）；拖动中指针落在 pane（`[data-dsh-pane]`）上时该 pane 高亮（`data-dsh-float-dock-over`），松开即**停靠**（center 合并进该 pane，`dockFloat`）；右下角缩放（`FLOAT_MIN_W/H` = 320/200，SE 角锚定）；点击任意处置顶（层叠顺序 = `floats` 数组序，`raiseFloat`）；头部右键菜单「回到侧边栏 / 关闭」；X = `closeTab`（关闭 tab 与窗口，正常触发 `onClose` 生命周期、释放终端）。
 - **持久化**：`floats` 随会话进 localStorage（`dsh-sidebar:v1:<sessionId>`），刷新原样恢复；`sanitizeState` 对每条 float **宽容校验**（非法条目单独丢弃不动整体布局，几何钳入当前视口，diff/ephemeral tab 不持久化，旧文档缺字段 = `[]`）；`maxCounterId` 的 uid 播种覆盖 `float:N` 前缀。
 - **服务语义**（消费插件可见，`features` 含 `'floatWindows'`）：`openTab` 的 dedupeKey/id 聚焦命中**浮动中的 tab = 置顶其窗口**（不重复开、不展开面板）；`closeTab`/`activateTab` 对浮动 tab 分别关窗/置顶并照常触发 `onClose`/`onActivate`；agent 终端 reconcile 会随宿主列表移除已消失的浮动终端窗口。tab 内容复用常规 `renderTab`（`TabContent`），浮窗对 `visible` 恒为 true，所有 tab 类型无差别浮动。
diff --git a/docs/plans/2026-08-23-free-window-design.md b/docs/plans/2026-08-23-free-window-design.md
index 0704137..598e9d5 100644
--- a/docs/plans/2026-08-23-free-window-design.md
+++ b/docs/plans/2026-08-23-free-window-design.md
@@ -23,7 +23,7 @@
 
 | 手势/入口 | 行为 |
 |---|---|
-| 按住 tab 拖到主会话区域 | 会话列出现虚线提示浮层「松开以在自由窗口中打开」；松开 → tab **移动**（pane 中移除）为浮窗，默认 480×360 居中于松点、钳入视口 |
+| 按住 tab 拖到主会话区域 | 会话列出现虚线提示浮层「松开以在自由窗口中打开」；松开 → tab **移动**（pane 中移除）为浮窗，默认 390×780（手机竖屏比例；创建时按视口钳制）居中于松点、钳入视口 |
 | tab 右键菜单「移动到自由窗口」 | 同上，落点为会话列中心（右面板与底面板的 TabBar 共用组件，一处生效） |
 | 浮窗头部按住拖动 | 移动窗口（pointer capture + rAF 直写 DOM + 松手提交 store）；拖到侧边栏 pane 上方时该 pane 高亮，松开即停靠（center 合并） |
 | 浮窗头部右键 | 菜单：「回到侧边栏」（停靠到激活 pane）/「关闭」 |
diff --git a/src/client/sidebar.module.css b/src/client/sidebar.module.css
index 4b90cc6..3419e9a 100644
--- a/src/client/sidebar.module.css
+++ b/src/client/sidebar.module.css
@@ -876,7 +876,7 @@ body[data-dsh-sidebar-dragging] .bottomPanel {
   overflow-y: auto;
   /* Deep trees truncate their labels instead of scrolling horizontally. */
   overflow-x: hidden;
-  padding: 2px 6px 8px;
+  padding: 4px 8px 8px;
 }
 
 /* One tree row: the app's session-row cell (34px, radius 8, inset, hover
@@ -1196,7 +1196,7 @@ body[data-dsh-sidebar-dragging] .bottomPanel {
   display: flex;
   align-items: center;
   gap: 6px;
-  padding: 4px 8px;
+  padding: 6px 8px;
   border-bottom: 1px solid var(--dsw-alias-border-l1);
 }
 
@@ -1215,6 +1215,7 @@ body[data-dsh-sidebar-dragging] .bottomPanel {
 .editorPathInput {
   flex: 1;
   min-width: 0;
+  box-sizing: border-box;
   height: 28px;
   padding: 0 10px;
   border: 1px solid var(--dsw-alias-border-l1);
@@ -1297,7 +1298,7 @@ body[data-dsh-sidebar-dragging] .bottomPanel {
   flex: none;
   display: flex;
   align-items: center;
-  gap: 4px;
+  gap: 6px;
   padding: 6px 8px;
   border-bottom: 1px solid var(--dsw-alias-border-l1);
 }
@@ -1430,7 +1431,7 @@ body[data-dsh-sidebar-dragging] .bottomPanel {
 
 .editorBanner {
   flex: none;
-  padding: 4px 12px;
+  padding: 4px 8px;
   font: var(--dsw-font-xxxs-11);
   color: var(--dsw-alias-state-warn-label);
   background: var(--dsw-alias-state-warn-tertiary);
@@ -1633,6 +1634,12 @@ body[data-dsh-sidebar-dragging] .bottomPanel {
   height: 100%;
 }
 
+/* Code lines get the same 12/16 inset as the markdown preview, so toggling
+   preview/edit never jumps the text's resting position. */
+.editorCm :global(.cm-scroller) {
+  padding: 12px 16px;
+}
+
 .editorCm :global(.cm-editor.cm-focused) {
   outline: none;
 }
@@ -1688,7 +1695,7 @@ body[data-dsh-sidebar-dragging] .bottomPanel {
   flex: 1;
   min-height: 0;
   overflow-y: auto;
-  padding: 10px 14px;
+  padding: 12px 16px;
   font: var(--dsw-font-xs-13);
 }
 
diff --git a/src/client/state.ts b/src/client/state.ts
index 2dc3792..fef1b62 100644
--- a/src/client/state.ts
+++ b/src/client/state.ts
@@ -120,9 +120,12 @@ export const BOTTOM_DEFAULT = 220
  *  header plus some content), the ceiling is the viewport. */
 export const FLOAT_MIN_W = 320
 export const FLOAT_MIN_H = 200
-/** Geometry a fresh free window starts with (clamped to the viewport). */
-export const FLOAT_DEFAULT_W = 480
-export const FLOAT_DEFAULT_H = 360
+/** Geometry a fresh free window starts with: a phone-like portrait ratio
+ *  (390×780 ≈ 1:2). The creation path additionally caps the size to the
+ *  viewport (minus a 24px margin), so a short viewport gets a shorter —
+ *  not overflowing — window instead of an exact ratio. */
+export const FLOAT_DEFAULT_W = 390
+export const FLOAT_DEFAULT_H = 780
 
 let nextIdCounter = 0
 /** Unique pane/tab id within one state instance. */
@@ -777,11 +780,17 @@ export function floatTab(state: SidebarState, tabId: string, x: number, y: numbe
     if (leaf.tabs.length === 0) emptied = true
   })
   if (emptied) node = removeLeafAt(node, source.id)
+  // Phone-ratio default, capped to the viewport before centering so the
+  // clamped position never leaves the window's bottom past the fold.
+  const vw = viewportW()
+  const vh = viewportH()
+  const width = Math.min(FLOAT_DEFAULT_W, Math.max(FLOAT_MIN_W, vw - 24))
+  const height = Math.min(FLOAT_DEFAULT_H, Math.max(FLOAT_MIN_H, vh - 24))
   const window = clampFloatGeometry(
-    x - FLOAT_DEFAULT_W / 2,
-    y - FLOAT_DEFAULT_H / 2,
-    FLOAT_DEFAULT_W,
-    FLOAT_DEFAULT_H,
+    x - width / 2,
+    y - height / 2,
+    width,
+    height,
   )
   const next: SidebarState = {
     ...state,
diff --git a/tests/e2e/float-window.e2e.ts b/tests/e2e/float-window.e2e.ts
index 52c5bb7..e2e819b 100644
--- a/tests/e2e/float-window.e2e.ts
+++ b/tests/e2e/float-window.e2e.ts
@@ -174,7 +174,7 @@ test('float a tab, move the window, reload restores it, dock it back', async ({
   const leftBefore = await floatWindow.evaluate((node) => Number.parseFloat((node as HTMLElement).style.left))
   expect(Number.isFinite(leftBefore), `style.left must be numeric, got ${leftBefore}`).toBe(true)
   expect(leftBefore).toBeGreaterThan(0)
-  expect(leftBefore).toBeLessThan(1440 - 480)
+  expect(leftBefore).toBeLessThan(1440 - 390)
   await assertNoCrash(page)
 
   // 2. The header drag moves the window (pointer capture + commit).
diff --git a/tests/free-window.spec.tsx b/tests/free-window.spec.tsx
index d3fd343..c90d498 100644
--- a/tests/free-window.spec.tsx
+++ b/tests/free-window.spec.tsx
@@ -213,9 +213,10 @@ describe('free windows: the window', () => {
       const state = store.getSnapshot().state!
       expect(state.floats).toHaveLength(1)
       expect(state.floats[0]!.tab.id).toBe('notes')
-      // Born at the conversation column's center, minus half the default
-      // size (480x360), clamped into the 1024x768 viewport.
-      expect(state.floats[0]).toMatchObject({ x: 400 - 240, y: 325 - 180, w: 480, h: 360 })
+      // Born at the conversation column's center with the phone-ratio
+      // default (390x780), created capped to the jsdom viewport (h 744) and
+      // clamped in (the centered y would be negative).
+      expect(state.floats[0]).toMatchObject({ x: 400 - 195, y: 0, w: 390, h: 744 })
       expect(container.querySelector('[data-dsh-float-window]')).not.toBeNull()
     } finally {
       unmount()
@@ -230,20 +231,22 @@ describe('free windows: the window', () => {
       act(() => { store.reduce(s => floatTabReducer(s, 'notes', 512, 384)) })
       const win = container.querySelector<HTMLElement>('[data-dsh-float-window]')!
       const header = win.querySelector<HTMLElement>('[class*="floatHeader"]')!
-      expect(win.style.left).toBe('272px')
+      expect(win.style.left).toBe('317px')
       // Grab at (300, 220) — the drag records the window's own origin, so
-      // moving the pointer to (200, 250) lands the window at (172, 234).
+      // moving the pointer to (200, 250) lands the window at (217, 42) —
+      // clamped back up to y 24 (the 744-tall window must stay in the
+      // 768-tall viewport: 768 - 744 = 24).
       act(() => {
         header.dispatchEvent(new MouseEvent('pointerdown', { bubbles: true, clientX: 300, clientY: 220, button: 0 }))
         header.dispatchEvent(new MouseEvent('pointermove', { bubbles: true, clientX: 200, clientY: 250 }))
       })
       await flushFrame()
-      expect(win.style.left).toBe('172px')
-      expect(win.style.top).toBe('234px')
+      expect(win.style.left).toBe('217px')
+      expect(win.style.top).toBe('24px')
       // The store is untouched mid-drag (DOM is the only record).
-      expect(store.getSnapshot().state!.floats[0]!.x).toBe(272)
+      expect(store.getSnapshot().state!.floats[0]!.x).toBe(317)
       act(() => { header.dispatchEvent(new MouseEvent('pointerup', { bubbles: true, clientX: 200, clientY: 250, button: 0 })) })
-      expect(store.getSnapshot().state!.floats[0]).toMatchObject({ x: 172, y: 234 })
+      expect(store.getSnapshot().state!.floats[0]).toMatchObject({ x: 217, y: 24 })
     } finally {
       unmount()
     }
@@ -258,14 +261,16 @@ describe('free windows: the window', () => {
       const win = container.querySelector<HTMLElement>('[data-dsh-float-window]')!
       const handle = win.querySelector<HTMLElement>('[class*="floatResize"]')!
       act(() => {
-        handle.dispatchEvent(new MouseEvent('pointerdown', { bubbles: true, clientX: 752, clientY: 564, button: 0 }))
-        handle.dispatchEvent(new MouseEvent('pointermove', { bubbles: true, clientX: 852, clientY: 614 }))
+        handle.dispatchEvent(new MouseEvent('pointerdown', { bubbles: true, clientX: 700, clientY: 750, button: 0 }))
+        handle.dispatchEvent(new MouseEvent('pointermove', { bubbles: true, clientX: 800, clientY: 800 }))
       })
       await flushFrame()
-      expect(win.style.width).toBe('580px')
-      expect(win.style.height).toBe('410px')
-      act(() => { handle.dispatchEvent(new MouseEvent('pointerup', { bubbles: true, clientX: 852, clientY: 614, button: 0 })) })
-      expect(store.getSnapshot().state!.floats[0]).toMatchObject({ w: 580, h: 410 })
+      // +100/+50 from the created 390x744: height clamps to the viewport
+      // ceiling (768 - y 12 = 756).
+      expect(win.style.width).toBe('490px')
+      expect(win.style.height).toBe('756px')
+      act(() => { handle.dispatchEvent(new MouseEvent('pointerup', { bubbles: true, clientX: 800, clientY: 800, button: 0 })) })
+      expect(store.getSnapshot().state!.floats[0]).toMatchObject({ w: 490, h: 756 })
     } finally {
       unmount()
     }
@@ -279,7 +284,7 @@ describe('free windows: the window', () => {
       act(() => { store.reduce(s => floatTabReducer(s, 'notes', 512, 384)) })
       const win = container.querySelector<HTMLElement>('[data-dsh-float-window]')!
       const header = win.querySelector<HTMLElement>('[class*="floatHeader"]')!
-      expect(win.style.left).toBe('272px')
+      expect(win.style.left).toBe('317px')
       act(() => { header.dispatchEvent(new MouseEvent('contextmenu', { bubbles: true, cancelable: true, clientX: 300, clientY: 220 })) })
       // The menu list is PORTALED to document.body, yet its events still
       // bubble through the React tree into the header's onPointerDown —
@@ -293,7 +298,7 @@ describe('free windows: the window', () => {
         header.dispatchEvent(new MouseEvent('pointermove', { bubbles: true, clientX: 200, clientY: 250 }))
       })
       await flushFrame()
-      expect(win.style.left).toBe('272px')
+      expect(win.style.left).toBe('317px')
       act(() => { dockRow.dispatchEvent(new MouseEvent('click', { bubbles: true })) })
       expect(store.getSnapshot().state!.floats).toHaveLength(0)
       expect(paneTabs(store)).toContain('notes')
diff --git a/tests/state.spec.ts b/tests/state.spec.ts
index 482558c..d542b12 100644
--- a/tests/state.spec.ts
+++ b/tests/state.spec.ts
@@ -919,8 +919,9 @@ describe('free windows (v0.16.0)', () => {
     expect(leaf.active).toBe('term:1')
     expect(floated.floats).toHaveLength(1)
     expect(floated.floats[0]!.tab).toEqual(git)
-    // Default size centered on the drop point (no viewport → floors only).
-    expect(floated.floats[0]).toMatchObject({ x: 300 - 240, y: 200 - 180, w: 480, h: 360 })
+    // Phone-ratio default (390x780) centered on the drop point (no viewport
+    // → size cap never bites; only the negative y clamps to 0).
+    expect(floated.floats[0]).toMatchObject({ x: 300 - 195, y: 0, w: 390, h: 780 })
     expect(floated.activePane).toBe(leaf.id)
   })
 
@@ -961,8 +962,9 @@ describe('free windows (v0.16.0)', () => {
       expect(moved.floats[0]).toMatchObject({ x: 0, y: 0 })
       // Beyond the right/bottom edge clamps the top-left so the window fits.
       moved = moveFloat(moved, id, 5000, 5000)
-      expect(moved.floats[0]!.x).toBe(1024 - 480)
-      expect(moved.floats[0]!.y).toBe(768 - 360)
+      // The float was CREATED capped to the viewport: w 390, h 768-24=744.
+      expect(moved.floats[0]!.x).toBe(1024 - 390)
+      expect(moved.floats[0]!.y).toBe(768 - 744)
       // No-op move returns the same reference (no persist churn).
       expect(moveFloat(moved, id, moved.floats[0]!.x, moved.floats[0]!.y)).toBe(moved)
       // Resize: floors, viewport ceiling, and the SE-corner anchor (x/y keep).