Add tab group sidebar support

crates/ely_app/src/shell/splits.rs

@@ -2,7 +2,7 @@ use std::collections::BTreeSet;
 
 use ely_browser_core::BrowserSnapshot;
 use ely_design_system::{colors, spacing};
-use ely_domain::{BrowserTab, SplitAxis, SplitId, SplitLayout};
+use ely_domain::{BrowserTab, SplitAxis, SplitId, SplitLayout, TabGroup, TabGroupId};
 use gpui::{
     AnyElement, Context, InteractiveElement, IntoElement, ParentElement, SharedString,
     StatefulInteractiveElement, Styled, Window, div, px, rgb,
@@ -18,30 +18,27 @@ impl ElyShell {
         snapshot: &BrowserSnapshot,
         cx: &mut Context<Self>,
     ) -> Vec<AnyElement> {
-        let mut rendered_split_ids = BTreeSet::new();
+        let mut rows = Vec::new();
-        let active_split_id = active_split_id(snapshot);
+        let mut row_state = SidebarRowState::new(snapshot);
 
-        snapshot
+        for tab in snapshot.tabs.iter().filter(|tab| sidebar_tab_is_visible(tab)) {
-            .tabs
+            let Some(group_id) = tab.group_id() else {
-            .iter()
+                self.push_sidebar_tab_row(&mut rows, snapshot, tab, &mut row_state, cx);
-            .filter(|tab| !tab.flags().favorite)
+                continue;
-            .filter(|tab| !tab.flags().pinned)
+            };
-            .filter_map(|tab| {
-                let Some(split_id) = tab.split_id() else {
-                    return Some(self.render_tab_row(tab, tab.id() == &snapshot.active_tab_id, cx));
-                };
-                let Some(layout) = saved_split_layout(snapshot, split_id) else {
-                    return Some(self.render_tab_row(tab, tab.id() == &snapshot.active_tab_id, cx));
-                };
 
-                if rendered_split_ids.insert(split_id.clone()) {
+            let Some(group) = snapshot.tab_groups.iter().find(|group| group.id() == group_id)
-                    let active = active_split_id.as_ref() == Some(split_id);
+            else {
-                    return self.render_saved_split_row(layout, active, cx);
+                self.push_sidebar_tab_row(&mut rows, snapshot, tab, &mut row_state, cx);
-                }
+                continue;
+            };
 
-                None
+            if row_state.rendered_group_ids.insert(group_id.clone()) {
-            })
+                self.push_tab_group_rows(&mut rows, snapshot, group, &mut row_state, cx);
-            .collect()
+            }
+        }
+
+        rows
     }
 
     pub(super) fn render_content_area(
@@ -190,7 +187,113 @@ impl ElyShell {
             .into_any_element()
     }
 
-    fn render_saved_split_row(
+    fn push_tab_group_rows(
+        &mut self,
+        rows: &mut Vec<AnyElement>,
+        snapshot: &BrowserSnapshot,
+        group: &TabGroup,
+        row_state: &mut SidebarRowState,
+        cx: &mut Context<Self>,
+    ) {
+        let group_tabs = group_tabs(snapshot, group);
+        let Some(first_tab_id) = group_tabs.first().map(|tab| tab.id().clone()) else {
+            return;
+        };
+
+        rows.push(self.render_tab_group_row(
+            group,
+            group_tabs.len(),
+            first_tab_id,
+            row_state.active_group_id.as_ref() == Some(group.id()),
+            cx,
+        ));
+
+        if group.collapsed() {
+            return;
+        }
+
+        for tab in group_tabs {
+            self.push_sidebar_tab_row(rows, snapshot, tab, row_state, cx);
+        }
+    }
+
+    fn push_sidebar_tab_row(
+        &mut self,
+        rows: &mut Vec<AnyElement>,
+        snapshot: &BrowserSnapshot,
+        tab: &BrowserTab,
+        row_state: &mut SidebarRowState,
+        cx: &mut Context<Self>,
+    ) {
+        if let Some(split_id) = tab.split_id()
+            && let Some(layout) = saved_split_layout(snapshot, split_id)
+        {
+            if row_state.rendered_split_ids.insert(split_id.clone()) {
+                let active = row_state.active_split_id.as_ref() == Some(split_id);
+                if let Some(row) = self.render_saved_split_row(layout, active, cx) {
+                    rows.push(row);
+                }
+            }
+            return;
+        }
+
+        rows.push(self.render_tab_row(tab, tab.id() == &snapshot.active_tab_id, cx));
+    }
+
+    fn render_tab_group_row(
+        &mut self,
+        group: &TabGroup,
+        tab_count: usize,
+        first_tab_id: ely_domain::TabId,
+        active: bool,
+        cx: &mut Context<Self>,
+    ) -> AnyElement {
+        let background = if active { colors::SURFACE_CARD } else { colors::CANVAS };
+        let border = if active { colors::PRIMARY } else { colors::HAIRLINE };
+
+        div()
+            .id(SharedString::from(format!("tab-group-{}", group.id().as_str())))
+            .rounded_md()
+            .border_1()
+            .border_color(rgb(border))
+            .bg(rgb(background))
+            .px_3()
+            .py_2()
+            .gap_2()
+            .flex()
+            .items_center()
+            .cursor_pointer()
+            .hover(|style| style.bg(rgb(colors::SURFACE_CARD)))
+            .active(|style| style.opacity(0.82))
+            .on_click(cx.listener(move |shell, _, window, cx| {
+                shell.select_tab(&first_tab_id, window, cx);
+            }))
+            .child(div().text_color(rgb(group.color_hex())).child(IconName::Folder))
+            .child(
+                div()
+                    .min_w_0()
+                    .flex()
+                    .flex_col()
+                    .gap_1()
+                    .child(
+                        div()
+                            .text_sm()
+                            .font_semibold()
+                            .truncate()
+                            .text_color(rgb(colors::INK))
+                            .child(group.name().to_string()),
+                    )
+                    .child(
+                        div()
+                            .text_xs()
+                            .text_color(rgb(colors::MUTED))
+                            .child(format!("{tab_count} tabs")),
+                    ),
+            )
+            .into_any_element()
+    }
+
+    pub(super) fn render_saved_split_row(
         &mut self,
         layout: &SplitLayout,
         active: bool,
@@ -261,9 +364,48 @@ fn active_split_id(snapshot: &BrowserSnapshot) -> Option<SplitId> {
         .and_then(|tab| tab.split_id().cloned())
 }
 
+fn active_group_id(snapshot: &BrowserSnapshot) -> Option<TabGroupId> {
+    snapshot
+        .tabs
+        .iter()
+        .find(|tab| tab.id() == &snapshot.active_tab_id)
+        .and_then(|tab| tab.group_id().cloned())
+}
+
+struct SidebarRowState {
+    active_group_id: Option<TabGroupId>,
+    active_split_id: Option<SplitId>,
+    rendered_group_ids: BTreeSet<TabGroupId>,
+    rendered_split_ids: BTreeSet<SplitId>,
+}
+
+impl SidebarRowState {
+    fn new(snapshot: &BrowserSnapshot) -> Self {
+        Self {
+            active_group_id: active_group_id(snapshot),
+            active_split_id: active_split_id(snapshot),
+            rendered_group_ids: BTreeSet::new(),
+            rendered_split_ids: BTreeSet::new(),
+        }
+    }
+}
+
 fn saved_split_layout<'a>(
     snapshot: &'a BrowserSnapshot,
     split_id: &SplitId,
 ) -> Option<&'a SplitLayout> {
     snapshot.split_layouts.iter().find(|layout| layout.id() == split_id && layout.saved())
 }
+
+fn group_tabs<'a>(snapshot: &'a BrowserSnapshot, group: &TabGroup) -> Vec<&'a BrowserTab> {
+    snapshot
+        .tabs
+        .iter()
+        .filter(|tab| sidebar_tab_is_visible(tab))
+        .filter(|tab| tab.group_id() == Some(group.id()))
+        .collect()
+}
+
+fn sidebar_tab_is_visible(tab: &BrowserTab) -> bool {
+    !tab.flags().favorite && !tab.flags().pinned
+}

crates/ely_browser_core/src/error.rs

@@ -1,6 +1,6 @@
 use ely_domain::{
     BookmarkId, DomainError, DownloadId, NoteId, PluginId, ProfileId, ReadingListId, SpaceId,
-    SplitId, TabId,
+    SplitId, TabGroupId, TabId,
 };
 use thiserror::Error;
 
@@ -21,6 +21,9 @@ pub enum CoreError {
     #[error("split not found: {id}")]
     SplitNotFound { id: SplitId },
 
+    #[error("tab group not found: {id}")]
+    TabGroupNotFound { id: TabGroupId },
+
     #[error("profile not found: {id}")]
     ProfileNotFound { id: ProfileId },
 

crates/ely_browser_core/src/navigation.rs

@@ -100,6 +100,10 @@ pub(crate) fn tab_note_body(command: &str) -> Option<&str> {
     command_argument(command, &["tab-note ", "tab note ", "note-tab ", "note tab "])
 }
 
+pub(crate) fn tab_group_name(command: &str) -> Option<&str> {
+    command_argument(command, &["group-tab ", "group tab ", "tab-group ", "tab group "])
+}
+
 pub(crate) fn new_profile_name(command: &str) -> Option<&str> {
     command_argument(command, &["new-profile ", "new profile "])
 }

crates/ely_browser_core/src/state.rs

@@ -4,8 +4,8 @@ use ely_domain::{
     ArchivePolicy, ArchivedTab, BookmarkEntry, BrowserTab, DomainError, DownloadEntry,
     DownloadPolicy, FavoriteLimit, HistoryEntry, HistoryRecordingPolicy, NewTabDestination,
     NoteEntry, Profile, ProfileId, ProfileKind, ReadingListEntry, SearchEngine,
-    SitePermissionAuditEvent, SitePermissionEntry, Space, SpaceId, SplitLayout, SyncStatus, TabId,
+    SitePermissionAuditEvent, SitePermissionEntry, Space, SpaceId, SplitLayout, SyncStatus,
-    UrlText,
+    TabGroup, TabId, UrlText,
 };
 
 use crate::{CoreError, navigation::tab_title};
@@ -22,6 +22,7 @@ mod reading_list;
 mod site_permissions;
 mod splits;
 mod sync;
+mod tab_groups;
 mod tab_order;
 mod tabs;
 
@@ -60,6 +61,7 @@ pub struct BrowserSnapshot {
     pub download_entries: Vec<DownloadEntry>,
     pub history_entries: Vec<HistoryEntry>,
     pub active_profile_history_entry_count: usize,
+    pub tab_groups: Vec<TabGroup>,
     pub split_layouts: Vec<SplitLayout>,
     pub installed_plugins: Vec<InstalledPlugin>,
     pub plugin_audit_events: Vec<PluginAuditEvent>,
@@ -92,6 +94,7 @@ pub struct BrowserCore {
     site_permission_audit_events: Vec<SitePermissionAuditEvent>,
     download_entries: Vec<DownloadEntry>,
     history_entries: Vec<HistoryEntry>,
+    tab_groups: Vec<TabGroup>,
     split_layouts: Vec<SplitLayout>,
     archived_split_layouts: Vec<SplitLayout>,
     installed_plugins: Vec<InstalledPlugin>,
@@ -161,6 +164,7 @@ impl BrowserCore {
             site_permission_audit_events: Vec::new(),
             download_entries: Vec::new(),
             history_entries: Vec::new(),
+            tab_groups: Vec::new(),
             split_layouts: Vec::new(),
             archived_split_layouts: Vec::new(),
             installed_plugins: Vec::new(),
@@ -354,6 +358,7 @@ impl BrowserCore {
             download_entries: self.visible_downloads(),
             history_entries: self.visible_history(),
             active_profile_history_entry_count: self.active_profile_history_count(),
+            tab_groups: self.visible_tab_groups(),
             split_layouts: self.visible_split_layouts(),
             installed_plugins: self.installed_plugins.clone(),
             plugin_audit_events: self.plugin_audit_events.clone(),

crates/ely_browser_core/src/state/commands.rs

@@ -9,7 +9,7 @@ use crate::{
         move_tab_space_name, new_private_profile_name, new_profile_name, new_space_name, note_body,
         notes_url, plugin_detail_url, plugins_url, reading_list_url, reading_progress_percent,
         search_url, settings_page_url, settings_url, shortcut_settings_url, space_icon,
-        switch_profile_name, sync_status_url, tab_note_body, task_manager_url,
+        switch_profile_name, sync_status_url, tab_group_name, tab_note_body, task_manager_url,
     },
 };
 
@@ -133,6 +133,10 @@ impl BrowserCore {
             self.set_active_tab_reading_progress(percent)?;
             return Ok(true);
         }
+        if let Some(name) = tab_group_name(command) {
+            self.group_active_tab(name)?;
+            return Ok(true);
+        }
         if let Some(body) = tab_note_body(command) {
             self.save_active_tab_note(body)?;
             return Ok(true);

crates/ely_browser_core/src/state/tab_groups.rs

@@ -0,0 +1,100 @@
+use ely_domain::{TabGroup, TabGroupId, TabId};
+
+use crate::CoreError;
+
+use super::BrowserCore;
+
+impl BrowserCore {
+    pub fn group_active_tab(&mut self, name: impl Into<String>) -> Result<TabGroupId, CoreError> {
+        let group_id = self.find_or_create_active_space_tab_group(name)?;
+        let active_tab_id = self.active_tab_id.clone();
+        self.assign_tab_to_group(&active_tab_id, &group_id)?;
+        Ok(group_id)
+    }
+
+    pub fn assign_tab_to_group(
+        &mut self,
+        tab_id: &TabId,
+        group_id: &TabGroupId,
+    ) -> Result<(), CoreError> {
+        let group_space_id = self
+            .tab_groups
+            .iter()
+            .find(|group| group.id() == group_id)
+            .map(|group| group.space_id().clone())
+            .ok_or_else(|| CoreError::TabGroupNotFound { id: group_id.clone() })?;
+        let tab = self
+            .tabs
+            .iter_mut()
+            .find(|tab| tab.id() == tab_id)
+            .ok_or_else(|| CoreError::TabNotFound { id: tab_id.clone() })?;
+
+        if tab.space_id() != &group_space_id {
+            return Err(CoreError::TabGroupNotFound { id: group_id.clone() });
+        }
+
+        tab.set_group_id(group_id.clone());
+        Ok(())
+    }
+
+    pub fn clear_tab_group(&mut self, tab_id: &TabId) -> Result<(), CoreError> {
+        let tab = self
+            .tabs
+            .iter_mut()
+            .find(|tab| tab.id() == tab_id)
+            .ok_or_else(|| CoreError::TabNotFound { id: tab_id.clone() })?;
+        tab.clear_group_id();
+        Ok(())
+    }
+
+    pub(super) fn visible_tab_groups(&self) -> Vec<TabGroup> {
+        let mut groups = self
+            .tab_groups
+            .iter()
+            .filter(|group| group.space_id() == &self.active_space_id)
+            .cloned()
+            .collect::<Vec<_>>();
+        groups.sort_by(|left, right| {
+            left.sort_key().cmp(&right.sort_key()).then_with(|| left.id().cmp(right.id()))
+        });
+        groups
+    }
+
+    fn find_or_create_active_space_tab_group(
+        &mut self,
+        name: impl Into<String>,
+    ) -> Result<TabGroupId, CoreError> {
+        let name = name.into();
+        if let Some(group_id) = self.find_active_space_group_id(&name) {
+            return Ok(group_id);
+        }
+
+        let active_space_id = self.active_space_id.clone();
+        let color_hex = self.active_space()?.accent_hex();
+        let sort_key = self.next_tab_group_sort_key();
+        let group = TabGroup::new(active_space_id, name, color_hex, sort_key)?;
+        let group_id = group.id().clone();
+        self.tab_groups.push(group);
+        Ok(group_id)
+    }
+
+    fn find_active_space_group_id(&self, name: &str) -> Option<TabGroupId> {
+        let normalized_name = name.trim().to_lowercase();
+        self.tab_groups
+            .iter()
+            .find(|group| {
+                group.space_id() == &self.active_space_id
+                    && group.name().to_lowercase() == normalized_name
+            })
+            .map(|group| group.id().clone())
+    }
+
+    fn next_tab_group_sort_key(&self) -> u64 {
+        self.tab_groups
+            .iter()
+            .filter(|group| group.space_id() == &self.active_space_id)
+            .map(TabGroup::sort_key)
+            .max()
+            .map_or(0, |sort_key| sort_key.saturating_add(1))
+    }
+}

crates/ely_browser_core/src/state/tabs.rs

@@ -4,13 +4,12 @@ use ely_domain::{
     ArchivePolicy, ArchiveSource, ArchivedTab, BrowserTab, ProfileId, SpaceId, TabId, UrlText,
 };
 
+use super::BrowserCore;
 use crate::{
     CoreError,
     navigation::{tab_matches_query, tab_title},
 };
 
-use super::BrowserCore;
-
 impl BrowserCore {
     pub fn open_new_tab(&mut self) -> Result<TabId, CoreError> {
         let url = self.new_tab_url()?;
@@ -53,6 +52,7 @@ impl BrowserCore {
         let tab_index = self.active_tab_index()?;
         let target_sort_key = self.next_tab_sort_key(space_id);
         self.tabs[tab_index].move_to_space(space_id.clone());
+        self.tabs[tab_index].clear_group_id();
         self.tabs[tab_index].set_sort_key(target_sort_key);
         self.sort_tabs_within_space(space_id);
         self.active_tabs_by_space.insert(space_id.clone(), tab_id.clone());

crates/ely_browser_core/tests/tab_groups.rs

@@ -0,0 +1,104 @@
+use std::error::Error;
+
+use ely_browser_core::{BrowserCore, CoreError, InitialBrowserConfig};
+use ely_domain::{CommandIntent, UrlText};
+
+#[test]
+fn group_active_tab_creates_visible_space_group() -> Result<(), Box<dyn Error>> {
+    let mut core = BrowserCore::new(InitialBrowserConfig::ely_defaults()?)?;
+
+    let group_id = core.group_active_tab("Research")?;
+    let snapshot = core.snapshot()?;
+    let active_tab = snapshot
+        .tabs
+        .iter()
+        .find(|tab| tab.id() == &snapshot.active_tab_id)
+        .ok_or(CoreError::MissingActiveTab)?;
+
+    assert_eq!(snapshot.tab_groups.len(), 1);
+    assert_eq!(snapshot.tab_groups[0].id(), &group_id);
+    assert_eq!(snapshot.tab_groups[0].name(), "Research");
+    assert_eq!(snapshot.tab_groups[0].space_id(), &snapshot.active_space_id);
+    assert_eq!(active_tab.group_id(), Some(&group_id));
+    Ok(())
+}
+
+#[test]
+fn group_active_tab_reuses_matching_space_group() -> Result<(), Box<dyn Error>> {
+    let mut core = BrowserCore::new(InitialBrowserConfig::ely_defaults()?)?;
+    let first_group_id = core.group_active_tab("Research")?;
+
+    let second_tab_id = core.open_tab(UrlText::parse("https://example.com")?);
+    let second_group_id = core.group_active_tab("research")?;
+    let snapshot = core.snapshot()?;
+    let grouped_count =
+        snapshot.tabs.iter().filter(|tab| tab.group_id() == Some(&first_group_id)).count();
+
+    assert_eq!(first_group_id, second_group_id);
+    assert_eq!(snapshot.tab_groups.len(), 1);
+    assert_eq!(grouped_count, 2);
+    assert_eq!(snapshot.active_tab_id, second_tab_id);
+    Ok(())
+}
+
+#[test]
+fn tab_groups_stay_with_active_space() -> Result<(), Box<dyn Error>> {
+    let mut core = BrowserCore::new(InitialBrowserConfig::ely_defaults()?)?;
+    let work_space_id = core.snapshot()?.active_space_id;
+    let group_id = core.group_active_tab("Research")?;
+    let research_space_id = core.create_space("Research", "R", 0xf54e00)?;
+
+    let research_snapshot = core.snapshot()?;
+    assert_eq!(research_snapshot.active_space_id, research_space_id);
+    assert!(research_snapshot.tab_groups.is_empty());
+
+    core.select_space(&work_space_id)?;
+    let work_snapshot = core.snapshot()?;
+
+    assert_eq!(work_snapshot.tab_groups.len(), 1);
+    assert_eq!(work_snapshot.tab_groups[0].id(), &group_id);
+    Ok(())
+}
+
+#[test]
+fn moving_grouped_tab_to_another_space_clears_group() -> Result<(), Box<dyn Error>> {
+    let mut core = BrowserCore::new(InitialBrowserConfig::ely_defaults()?)?;
+    let work_space_id = core.snapshot()?.active_space_id;
+    let research_space_id = core.create_space("Research", "R", 0xf54e00)?;
+    core.select_space(&work_space_id)?;
+    let moved_tab_id = core.open_tab(UrlText::parse("https://example.com")?);
+    core.group_active_tab("Docs")?;
+
+    core.move_active_tab_to_space(&research_space_id)?;
+    let snapshot = core.snapshot()?;
+    let moved_tab = snapshot
+        .tabs
+        .iter()
+        .find(|tab| tab.id() == &moved_tab_id)
+        .ok_or(CoreError::MissingActiveTab)?;
+
+    assert_eq!(snapshot.active_space_id, research_space_id);
+    assert_eq!(moved_tab.group_id(), None);
+    Ok(())
+}
+
+#[test]
+fn group_tab_command_groups_active_tab() -> Result<(), Box<dyn Error>> {
+    let mut core = BrowserCore::new(InitialBrowserConfig::ely_defaults()?)?;
+
+    core.set_command_query(">group-tab Research");
+    let intent = core.submit_command()?;
+    let snapshot = core.snapshot()?;
+    let active_tab = snapshot
+        .tabs
+        .iter()
+        .find(|tab| tab.id() == &snapshot.active_tab_id)
+        .ok_or(CoreError::MissingActiveTab)?;
+
+    assert_eq!(intent, Some(CommandIntent::Command("group-tab Research".to_string())));
+    assert_eq!(snapshot.tab_groups.len(), 1);
+    assert_eq!(snapshot.tab_groups[0].name(), "Research");
+    assert_eq!(active_tab.group_id(), Some(snapshot.tab_groups[0].id()));
+    assert_eq!(snapshot.command_query, "");
+    Ok(())
+}

crates/ely_domain/src/identifiers.rs

@@ -36,6 +36,7 @@ macro_rules! entity_id {
 entity_id!(TabId, "tab");
 entity_id!(SpaceId, "space");
 entity_id!(ProfileId, "profile");
+entity_id!(TabGroupId, "tab_group");
 entity_id!(SplitId, "split");
 entity_id!(WebViewId, "webview");
 entity_id!(DownloadId, "download");

crates/ely_domain/src/lib.rs

@@ -18,6 +18,7 @@ mod space;
 mod split;
 mod sync;
 mod tab;
+mod tab_group;
 mod url_text;
 
 pub use archive::{ArchiveSource, ArchivedTab};
@@ -31,7 +32,8 @@ pub use error::DomainError;
 pub use favorite::FavoriteLimit;
 pub use history::HistoryEntry;
 pub use identifiers::{
-    BookmarkId, DownloadId, NoteId, ProfileId, ReadingListId, SpaceId, SplitId, TabId, WebViewId,
+    BookmarkId, DownloadId, NoteId, ProfileId, ReadingListId, SpaceId, SplitId, TabGroupId, TabId,
+    WebViewId,
 };
 pub use new_tab::NewTabDestination;
 pub use note::{NoteEntry, NoteTarget};
@@ -54,4 +56,5 @@ pub use sync::{
     SyncStatus,
 };
 pub use tab::{BrowserTab, TabFlags, TabState};
+pub use tab_group::TabGroup;
 pub use url_text::UrlText;

crates/ely_domain/src/tab.rs

@@ -1,6 +1,6 @@
 use std::time::SystemTime;
 
-use crate::{DomainError, ProfileId, SpaceId, SplitId, TabId, UrlText};
+use crate::{DomainError, ProfileId, SpaceId, SplitId, TabGroupId, TabId, UrlText};
 
 #[derive(Clone, Debug, Eq, PartialEq)]
 pub enum TabState {
@@ -30,6 +30,7 @@ pub struct BrowserTab {
     parent_tab_id: Option<TabId>,
     state: TabState,
     flags: TabFlags,
+    group_id: Option<TabGroupId>,
     split_id: Option<SplitId>,
     sort_key: u64,
     sync_enabled: bool,
@@ -57,6 +58,7 @@ impl BrowserTab {
             parent_tab_id: None,
             state: TabState::Ready,
             flags: TabFlags::default(),
+            group_id: None,
             split_id: None,
             sort_key: 0,
             sync_enabled: true,
@@ -176,6 +178,19 @@ impl BrowserTab {
         self.space_id = space_id;
     }
 
+    #[must_use]
+    pub fn group_id(&self) -> Option<&TabGroupId> {
+        self.group_id.as_ref()
+    }
+
+    pub fn set_group_id(&mut self, group_id: TabGroupId) {
+        self.group_id = Some(group_id);
+    }
+
+    pub fn clear_group_id(&mut self) {
+        self.group_id = None;
+    }
+
     #[must_use]
     pub fn split_id(&self) -> Option<&SplitId> {
         self.split_id.as_ref()

crates/ely_domain/src/tab_group.rs

@@ -0,0 +1,160 @@
+use std::time::{Duration, SystemTime};
+
+use crate::{DomainError, SpaceId, TabGroupId};
+
+#[derive(Clone, Debug, Eq, PartialEq)]
+pub struct TabGroup {
+    id: TabGroupId,
+    space_id: SpaceId,
+    name: String,
+    color_hex: u32,
+    collapsed: bool,
+    sort_key: u64,
+    created_at: SystemTime,
+    updated_at: SystemTime,
+}
+
+impl TabGroup {
+    pub fn new(
+        space_id: SpaceId,
+        name: impl Into<String>,
+        color_hex: u32,
+        sort_key: u64,
+    ) -> Result<Self, DomainError> {
+        let name = normalized_name(name)?;
+        let created_at = SystemTime::now();
+        Ok(Self {
+            id: TabGroupId::new(),
+            space_id,
+            name,
+            color_hex,
+            collapsed: false,
+            sort_key,
+            created_at,
+            updated_at: created_at,
+        })
+    }
+
+    #[must_use]
+    pub fn id(&self) -> &TabGroupId {
+        &self.id
+    }
+
+    #[must_use]
+    pub fn space_id(&self) -> &SpaceId {
+        &self.space_id
+    }
+
+    #[must_use]
+    pub fn name(&self) -> &str {
+        &self.name
+    }
+
+    pub fn rename(&mut self, name: impl Into<String>) -> Result<(), DomainError> {
+        self.name = normalized_name(name)?;
+        self.record_update();
+        Ok(())
+    }
+
+    #[must_use]
+    pub fn color_hex(&self) -> u32 {
+        self.color_hex
+    }
+
+    pub fn set_color_hex(&mut self, color_hex: u32) {
+        self.color_hex = color_hex;
+        self.record_update();
+    }
+
+    #[must_use]
+    pub fn collapsed(&self) -> bool {
+        self.collapsed
+    }
+
+    pub fn set_collapsed(&mut self, collapsed: bool) {
+        self.collapsed = collapsed;
+        self.record_update();
+    }
+
+    #[must_use]
+    pub fn sort_key(&self) -> u64 {
+        self.sort_key
+    }
+
+    pub fn set_sort_key(&mut self, sort_key: u64) {
+        self.sort_key = sort_key;
+        self.record_update();
+    }
+
+    #[must_use]
+    pub fn created_at(&self) -> SystemTime {
+        self.created_at
+    }
+
+    #[must_use]
+    pub fn updated_at(&self) -> SystemTime {
+        self.updated_at
+    }
+
+    fn record_update(&mut self) {
+        let now = SystemTime::now();
+        self.updated_at =
+            if now > self.updated_at { now } else { self.updated_at + Duration::from_nanos(1) };
+    }
+}
+
+fn normalized_name(name: impl Into<String>) -> Result<String, DomainError> {
+    let name = name.into();
+    let name = name.trim();
+    if name.is_empty() {
+        return Err(DomainError::EmptyField { field: "tab_group_name" });
+    }
+
+    Ok(name.to_string())
+}
+
+#[cfg(test)]
+mod tests {
+    use super::TabGroup;
+    use crate::{DomainError, SpaceId};
+
+    #[test]
+    fn creates_tab_group_with_trimmed_name() -> Result<(), DomainError> {
+        let space_id = SpaceId::new();
+        let group = TabGroup::new(space_id.clone(), " Research ", 0xf54e00, 7)?;
+
+        assert_eq!(group.space_id(), &space_id);
+        assert_eq!(group.name(), "Research");
+        assert_eq!(group.color_hex(), 0xf54e00);
+        assert_eq!(group.sort_key(), 7);
+        assert!(!group.collapsed());
+        Ok(())
+    }
+
+    #[test]
+    fn rejects_empty_tab_group_name() -> Result<(), Box<dyn std::error::Error>> {
+        let error = match TabGroup::new(SpaceId::new(), " ", 0xf54e00, 0) {
+            Err(error) => error,
+            Ok(_) => return Err("empty tab group name was accepted".into()),
+        };
+
+        assert_eq!(error, DomainError::EmptyField { field: "tab_group_name" });
+        Ok(())
+    }
+
+    #[test]
+    fn updates_mutable_tab_group_fields() -> Result<(), DomainError> {
+        let mut group = TabGroup::new(SpaceId::new(), "Research", 0xf54e00, 0)?;
+
+        group.rename("Docs")?;
+        group.set_color_hex(0x2f6fed);
+        group.set_collapsed(true);
+        group.set_sort_key(9);
+
+        assert_eq!(group.name(), "Docs");
+        assert_eq!(group.color_hex(), 0x2f6fed);
+        assert!(group.collapsed());
+        assert_eq!(group.sort_key(), 9);
+        Ok(())
+    }
+}