feat(tabs): add content-sized top tabs with Chrome, Minimal and Tag styles

architecture/notes/nebula_app/gpui_shell/workspace/2026-10-20-content-sized-top-tabs.md

@@ -0,0 +1,52 @@
+# Content-sized top tabs
+
+## Status
+Implemented.
+
+Overflow behavior superseded by [interactive tab titles](2026-10-20-interactive-tab-titles.md).
+
+## Context
+Equal-width tabs consumed a full 220px for short names. Three horizontal tab
+treatments also needed to share activation, closing and ordering behavior.
+
+## Evidence
+[The top tab renderer](../../../../../nebula_app/src/gpui_shell/workspace/top_tabs.rs) previously divided the viewport by the tab count and
+used that same fixed pitch for dragging. Applying variable widths only in CSS
+would leave overflow buttons and drag destinations using the wrong positions.
+Occluding tab hitboxes also suppress ancestor hover listeners. Top tab rows
+therefore receive movement directly; an unhovered-root release handler covers
+fast drops before the full-window drag overlay has painted.
+
+## Decision
+Measure names with GPUI's text shaper and reserve the existing identity, status,
+administrator and split-count slots. Cap each tab at 220 logical pixels and use
+an ellipsis plus the full-title tooltip. `top_tabs/layout.rs` owns the prefix
+positions used by layout, arrow navigation and drag ordering. Each horizontal
+gesture freezes that layout and captures the starting scroll offset; auto-scroll
+is included in pointer displacement. The pinned settings tab stays outside the
+reorderable range. Sidebar gestures retain their row pitch.
+
+`nebula_settings::TabStyle` owns the saved `tab_style` values: `chrome` (default),
+`minimal`, and `tag`. Appearance settings persist through the existing settings
+boundary; open windows use the cached global snapshot. Styling has no tab state.
+
+## Rejected alternatives
+Intrinsic widths without measured positions would leave ordering and overflow
+navigation inconsistent. Text marquees add perpetual movement; ellipses meet the
+requested overflow behavior while preserving a stable titlebar.
+
+## Consequences
+Long titles no longer force short titles to stretch. The existing left sidebar
+layout and session metadata keep their semantics.
+
+## Validation
+[Core preference round trips/reset](../../../../../nebula_settings/src/tab_style.rs); mixed-width navigation and ordering rules;
+rendered tests for all three styles, CJK/long titles, hover close and bidirectional
+dragging; [existing settings navigation and density coverage](../../../../../nebula_app/src/gpui_shell/workspace/settings_navigation/ui_tests.rs).
+
+## Supersedes
+None.
+
+## Revisit when
+The maximum tab width becomes user-configurable or window chrome changes its
+reserved toolbar geometry.

architecture/notes/nebula_app/gpui_shell/workspace/2026-10-20-interactive-tab-titles.md

@@ -0,0 +1,48 @@
+# Interactive long tab titles
+
+## Status
+Implemented.
+
+Superseded by [static tab overflow](2026-10-20-static-tab-overflow.md).
+
+## Context
+Long names must be readable while selected or hovered, while inactive tabs retain
+an ellipsis. A scrolling title must not move the identity, shell prefix or close button.
+
+## Evidence
+[The top tab renderer](../../../../../nebula_app/src/gpui_shell/workspace/top_tabs.rs)
+already measures titles and reserves fixed control slots. GPUI's keyed element
+state owns hover only while the element is rendered; its animation wrapper owns
+the clock and honors the application reduced-motion preference.
+
+## Decision
+Retain one hover flag per rendered tab using GPUI keyed state. Only overflowing,
+visible, selected/hovered titles in the active window receive a repeating
+animation. [The label](../../../../../nebula_app/src/gpui_shell/workspace/top_tabs/label.rs)
+clips its own text, pauses at either end and scrolls back at 32 logical pixels per
+second. Removing the animation restores ellipsis and discards its clock. No
+workspace timer or persistent settings are added. The selected terminal's muted
+shell prefix stays outside the moving name and replaces the former trailing
+shell indicator. The trailing close/status slot retains its size.
+
+## Rejected alternatives
+Animating entire tabs would move controls and hitboxes. Animating every long
+name would schedule frames for inactive and offscreen tabs. A second task-based
+timer would duplicate GPUI's element lifetime and reduced-motion handling.
+
+## Consequences
+At most the selected and hovered visible long titles move. Short titles and
+inactive windows remain static. Selecting a terminal adds its shell prefix to
+the measured width, still capped at 220 logical pixels.
+
+## Validation
+[Rendered interaction coverage](../../../../../nebula_app/src/gpui_shell/workspace/settings_navigation/ui_tests.rs)
+checks hover over tab padding, selection after pointer exit, idle ellipsis,
+short names, fixed tab width and separation from the close button.
+
+## Supersedes
+The ellipsis-only overflow choice in
+[content-sized top tabs](2026-10-20-content-sized-top-tabs.md).
+
+## Revisit when
+Text needs a different scrolling speed, or tab controls change their width.

architecture/notes/nebula_app/gpui_shell/workspace/2026-10-20-static-tab-overflow.md

@@ -0,0 +1,60 @@
+# Static tab overflow and overlapping Chrome feet
+
+## Status
+Implemented.
+
+## Context
+Long names must stay still when selected or hovered and fade out at the trailing
+edge. Chrome hover and selected surfaces should be close despite the 12px flared
+corners. Tabs use spacing alone rather than separator lines.
+
+## Evidence
+[The label painter](../../../../../nebula_app/src/gpui_shell/workspace/top_tabs/label.rs)
+uses GPUI content masks and opacity on a containing Div. Canvas style opacity is
+not applied by GPUI's Canvas painter; Div applies it to both monochrome glyphs
+and color emoji. Overpainting a gradient with a theme background would
+hide wallpaper or show a rectangle with translucent/custom themes.
+
+## Decision
+Remove title animations and their hover state. A frame-local shared shaped line
+paints a solid area and 24 clipped opacity bands over the final 48 logical
+pixels. It retains the normal text height and full accessible name. No animation
+frames, timers, or persistent caches are requested by labels.
+
+Chrome tabs overlap by 10px, leaving about 2px between a neighboring hover surface
+and the selected tab's inset body. The shared strip geometry stores this gap for
+layout, navigation and frozen drag snapshots. Selected tabs paint after inactive
+neighbors; a dragged tab paints above both. No separator lines are drawn between
+tabs. Other tab styles retain their existing gap.
+
+The shell indicator uses the trailing status slot; it is visible on
+the selected tab and yields to the hover close button.
+
+A live preview exposed an out-of-bounds read when Runtime API tab creation
+changed the tab count during a pending drag. Reconcile the frozen snapshot before
+rendering or updating the pointer position, canceling it when the count changes
+or the source disappears. The renderer also rejects mismatched snapshot counts.
+
+## Rejected alternatives
+Opaque fade overlays would change the underlying surface. Per-glyph colors would
+not fade color emoji. Moving only the background without changing geometry would
+leave hit testing and drag positions inconsistent with the displayed tabs.
+
+## Consequences
+Overflow remains static in every interaction state. Glyph shaping is shared
+within each label's paint; the trailing fade uses a fixed number of clip bands.
+Chrome content has 20px horizontal padding: 12px for the flared feet plus 8px
+inside the visible body. Overlap stays outside its controls.
+
+## Validation
+[Rendered interaction tests](../../../../../nebula_app/src/gpui_shell/workspace/settings_navigation/ui_tests.rs)
+cover static fading, hover close hitboxes, absence of separators, overlapping
+tab bounds, content padding, count changes during pending gestures
+and bidirectional dragging. Shared geometry tests cover Chrome's
+negative gap alongside the existing positive-gap navigation cases.
+
+## Supersedes
+The scrolling behavior in [interactive tab titles](2026-10-20-interactive-tab-titles.md).
+
+## Revisit when
+Tab padding/corner sizes change or GPUI supplies a native gradient content mask.

nebula_app/i18n/en-US.json

@@ -160,6 +160,13 @@
       "refresh": "Refresh system environment for new terminals",
       "refresh_description": "Read current Windows environment settings when opening a terminal. Turn off to inherit the environment used to launch Pebrel, including temporary PATH entries. Open terminals are unchanged."
     },
+    "tabs": {
+      "title": "Top tab style",
+      "description": "Chrome, a thin top line, or outlined tags. Tab widths follow their titles; long names fade out at the end.",
+      "chrome": "Chrome",
+      "minimal": "Minimal",
+      "tag": "Tag"
+    },
     "cursor_motion": {
       "title": "Smooth cursor",
       "description": "Animate terminal cursor movement; large jumps remain instant.",

nebula_app/i18n/zh-CN.json

@@ -160,6 +160,13 @@
       "refresh": "新建终端时刷新系统环境变量",
       "refresh_description": "打开终端时读取 Windows 当前环境设置。关闭后继承启动 Pebrel 时的环境，包括临时添加的 PATH。已打开的终端不受影响。"
     },
+    "tabs": {
+      "title": "顶部标签栏样式",
+      "description": "谷歌、顶部细线或标签外观。标签宽度随名称自动调整，超长名称在末尾渐隐。",
+      "chrome": "谷歌样式",
+      "minimal": "简约样式",
+      "tag": "标签样式"
+    },
     "cursor_motion": {
       "title": "平滑光标",
       "description": "让终端光标平滑移动，大范围跳转仍立即定位。",

nebula_app/src/gpui_shell/config.rs

@@ -92,6 +92,7 @@ pub struct Settings {
     /// 标签关闭按钮与标签插入动画都在渲染热路径读取，必须随全局设置驻留内存。
     pub tab_close_visible: bool,
     pub tab_reveal: nebula_settings::TabRevealName,
+    pub tab_style: nebula_settings::TabStyle,
     /// 命令补全设置（settings.txt 的 `ghost`/`completion_style`），
     /// 类型直接用旧壳 display 的语义枚举：接受键判定与样式分支两壳同源。
     pub ghost: bool,
@@ -306,6 +307,7 @@ impl Settings {
             notification_duration: runtime.notification_duration,
             tab_close_visible: runtime.tab_close_visible,
             tab_reveal: runtime.tab_reveal,
+            tab_style: runtime.tab_style,
             ghost: runtime.ghost,
             completion_style: runtime.completion_style,
             cell_width_mode: runtime.cell_width_mode,

nebula_app/src/gpui_shell/settings_pane.rs

@@ -798,6 +798,7 @@ impl SettingsPane {
             "accept" => pick!(accept),
             "completion_style" => pick!(completion_style),
             "tabs_position" => pick!(tabs_position),
+            "tab_style" => pick!(tab_style),
             "tab_reveal" => pick!(tab_reveal),
             "density" => pick!(density),
             "new_tab_position" => pick!(new_tab_position),

nebula_app/src/gpui_shell/settings_pane/appearance_advanced.rs

@@ -84,6 +84,12 @@ impl SettingsPane {
             ));
         let interface = self
             .group(language.pick("界面", "Interface"), cx)
+            .child(self.select_row(
+                "tab_style",
+                language.text(crate::i18n::Message::SettingsTabsTitle),
+                language.text(crate::i18n::Message::SettingsTabsDescription),
+                cx,
+            ))
             .child(self.font_size_row(true, cx))
             .child(self.switch_row(
                 "dim_inactive_panes",

nebula_app/src/gpui_shell/settings_pane/initialization.rs

@@ -44,6 +44,21 @@ impl SettingsPane {
                                 this.set_cursor_motion(value, window, cx);
                                 return;
                             }
+                            if key == "tab_style" {
+                                if let Err(error) =
+                                    this.try_persist(&[(key, (*value).to_owned())], cx)
+                                {
+                                    let current = this.runtime.tab_style.settings_value();
+                                    this.sync_select(key, current, window, cx);
+                                    super::super::toast::toast(
+                                        window,
+                                        cx,
+                                        crate::display::ToastKind::Warning,
+                                        error.to_string(),
+                                    );
+                                }
+                                return;
+                            }
                             if key == "notification_duration" {
                                 this.set_notification_duration(value, window, cx);
                                 return;
@@ -73,6 +88,13 @@ impl SettingsPane {
         );
         let cursor_current =
             runtime.cursor_shape.map(|shape| shape.settings_value()).unwrap_or("beam");
+        add_select(
+            "tab_style",
+            nebula_settings::TabStyle::VALUES,
+            runtime.tab_style.settings_value(),
+            window,
+            cx,
+        );
         add_select(
             "cursor_motion",
             nebula_settings::CursorMotion::VALUES,

nebula_app/src/gpui_shell/settings_pane/localization.rs

@@ -72,6 +72,11 @@ pub(super) fn localized_select_labels(
             language.text(crate::i18n::Message::SettingsCursorMotionOff),
             language.text(crate::i18n::Message::SettingsCursorMotionSmooth),
         ],
+        "tab_style" => vec![
+            language.text(crate::i18n::Message::SettingsTabsChrome),
+            language.text(crate::i18n::Message::SettingsTabsMinimal),
+            language.text(crate::i18n::Message::SettingsTabsTag),
+        ],
         "tabs_position" => {
             vec![language.pick("左侧边栏", "Left sidebar"), language.pick("顶部", "Top")]
         },

nebula_app/src/gpui_shell/settings_pane/tab_style_settings_tests.rs

@@ -0,0 +1,45 @@
+use super::*;
+
+#[gpui::test]
+fn tab_style_persists_keyboard_choices_reopens_and_cancels(cx: &mut TestAppContext) {
+    use crate::gpui_shell::config::Settings;
+    let _lock = lock_theme_studio();
+    let _bytes = SettingsBytesGuard::capture();
+    std::fs::create_dir_all(nebula_settings::settings_dir()).unwrap();
+    std::fs::write(nebula_settings::settings_path(), TEST_SETTINGS).unwrap();
+    let (pane, mut window) = open_settings(cx);
+    pane.update(&mut window, |pane, cx| {
+        pane.active_section = 1;
+        cx.notify();
+    });
+    window.simulate_resize(size(px(1200.0), px(2400.0)));
+    let values = nebula_settings::TabStyle::VALUES;
+    for (row, &value) in values.iter().enumerate().skip(1) {
+        draw(&mut window);
+        click("settings-select-tab_style", &mut window);
+        press("down", &mut window);
+        press("enter", &mut window);
+        assert_eq!(RuntimeSettings::load().tab_style.settings_value(), value);
+        window.read(|cx| {
+            let settings = cx.global::<Settings>();
+            assert_eq!(settings.tab_style.settings_value(), value);
+        });
+        let reopened = window.update(|window, cx| cx.new(|cx| SettingsPane::new(window, cx)));
+        reopened.read_with(&mut window, |pane, cx| {
+            assert_eq!(
+                pane.select_of("tab_style").unwrap().read(cx).selected_index(cx).unwrap().row,
+                row
+            );
+        });
+    }
+    click("settings-select-tab_style", &mut window);
+    press("up", &mut window);
+    press("escape", &mut window);
+    pane.read_with(&mut window, |pane, _| {
+        assert_eq!(
+            pane.runtime.tab_style.settings_value(),
+            *values.last().unwrap(),
+            "Escape cancels"
+        );
+    });
+}

nebula_app/src/gpui_shell/settings_pane/theme_studio_tests.rs

@@ -17,6 +17,8 @@ use nebula_settings::{RawSettings, RuntimeSettings, ThemeDefinition, ThemeName};
 mod background_tests;
 #[path = "theme_package_tests.rs"]
 mod package_tests;
+#[path = "tab_style_settings_tests.rs"]
+mod tab_style_settings_tests;
 #[cfg(feature = "shader-background")]
 #[path = "terminal_effect_tests.rs"]
 mod terminal_effect_tests;

nebula_app/src/gpui_shell/terminal/view.rs

@@ -503,6 +503,7 @@ impl TerminalView {
     const RESIZE_SETTLE_DELAY: std::time::Duration = std::time::Duration::from_millis(150);
     /// 与 legacy `config::cursor::Cursor::default().blink_interval` 保持一致。
     const CURSOR_BLINK_INTERVAL: std::time::Duration = std::time::Duration::from_millis(750);
+    const CONTENT_PADDING_TOP: f32 = 4.0;
 
     /// 首帧前的当前单元格度量（与 element prepaint 同一公式：shape "M" 的
     /// advance / ascent / descent + 配置 offset）。让 spawn 网格与首帧布局一致，避免启动
@@ -1460,10 +1461,10 @@ impl Render for TerminalView {
             // 不画自己的背景：卡容器统一负责"卡底色（带窗口透明度）→
             // 壁纸"两层，这里再铺一层不透明 bg 会把它们全部盖死。圆角也
             // 只属于整个终端卡外壳；分屏 pane 自己带圆角会露出四个独立卡片。
-            // 卡内呼吸边距，对齐旧壳网格 reserve 的换算值：上下 8（chrome
-            // 64/底 16 各减 8px 卡缝），左右 12（CONTENT_PAD_X 20 − 卡缝 8）。
+            // 卡内边距：顶部 4px 收紧 chrome 下方留白，底部 8px，左右 12px。
             // 网格因此不贴圆角；padding 区点击由 grid_point 的钳制兜底。
-            .py(px(8.0))
+            .pt(px(Self::CONTENT_PADDING_TOP))
+            .pb(px(8.0))
             .px(px(12.0))
             .track_focus(&self.focus_handle)
             .on_action(cx.listener(Self::on_terminal_tab))

nebula_app/src/gpui_shell/terminal/view/pointer/tests.rs

@@ -202,6 +202,20 @@ fn clipboard(cx: &mut VisualTestContext) -> Option<String> {
     cx.update(|_, cx| cx.read_from_clipboard().and_then(|item| item.text()))
 }
 
+#[gpui::test]
+fn terminal_grid_keeps_inset_coordinates_after_tightening_top_padding(cx: &mut TestAppContext) {
+    let (terminal, mut cx, _receiver) = link_fixture(cx, b"prompt> ");
+    let bounds = cx.debug_bounds("mouse-terminal").unwrap();
+    terminal.read_with(&cx, |view, _| {
+        assert_eq!(view.origin, bounds.origin + point(px(12.0), px(4.0)));
+    });
+    let first_row = cell(&terminal, &cx, 2);
+    terminal.read_with(&cx, |view, _| {
+        let (grid, _) = view.grid_point(first_row);
+        assert_eq!(grid, TermPoint::new(Line(0), Column(2)));
+    });
+}
+
 #[gpui::test]
 fn right_click_menu_does_not_paste_and_quick_mode_remains_explicit(cx: &mut TestAppContext) {
     let (terminal, mut cx, receiver) = link_fixture(cx, b"prompt> ");

nebula_app/src/gpui_shell/terminal/view/reading/output_hover.rs

@@ -77,8 +77,8 @@ impl TerminalView {
                 ),
                 gpui::size((self.cell_width * self.cols as f32).min(px(180.0)), px(32.0)),
             ),
-            // 此偏移相对终端 root 的8px内边距，不参与网格或PTY尺寸计算。
-            top: px(8.0) + offset,
+            // 相对终端 root 的顶部内边距，不参与网格或PTY尺寸计算。
+            top: px(Self::CONTENT_PADDING_TOP) + offset,
         })
     }
     pub(in crate::gpui_shell::terminal) fn clear_output_hover(&mut self, cx: &mut Context<Self>) {