split lib/app.dart into lib/src/shell/ (T-394)

app.dart was 1187 LOC mixing five concerns. It now keeps ClideApp + the WidgetsApp root (~60 LOC); the shell moved to lib/src/shell/: - root_shell.dart — keyboard/intent routing (keymap resolution, double-tap modifiers, menu mnemonics), the overlay stack, and the welcome overlay - hat_bar.dart + project_switcher.dart — the window-chrome bar and its recents/file-actions dropdown (now in src/shell, not builtin/ — they're app chrome, not extension-shaped contributions) - slot_host.dart — slot mounting, focus-scope integration, the per-slot bodies incl. the workspace split + editor drag handle; _SlotBody's static title resolver became the shared resolveTabTitle - layout.dart — the three-column grid, status bar, collapse toggles, bottom icon rails app.dart re-exports RootLayout, SlotHost, StatusbarHost, and StatusbarCollapseToggle, so every existing import (incl. the three app-level test files) is unchanged. Pure move + minimal publics (RootShell, HatBar, ProjectSwitcherButton); full suite green with no test edits. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
2026-06-12 02:29:46 +02:00
parent 05584eb9e5
commit 7f16016bc3
8 changed files with 1292 additions and 1151 deletions
@@ -4060,3 +4060,34 @@ INSERT INTO ticket_history (ticket_record_id, field, old_value, new_value, chang
 Fix: drive both roster surfaces from TeamBroker membership (expose a listenable roster or change stream on the broker), delete TeamMemberJoined/TeamMemberLeft from kernel events/types.dart, and remove the dead listeners. Coordinate with T-395 (meta sidebar split) — whichever lands second adapts.

 Acceptance: spawning a team session through the orchestrator makes the member appear in both surfaces (widget test); the ghost event types are gone from types.dart; no kernel.events team-member subscriptions remain.', NULL, '2026-06-12 00:12:04', '2026-06-12 00:12:04', '2026-06-12 00:12:04', NULL, 'f04b7af4488069d004d99acbf9717cc6', 2) ON CONFLICT(hash) DO NOTHING;
+INSERT INTO ticket_history (ticket_record_id, field, old_value, new_value, changed_by, changed_at, created_at, updated_at, deleted_at, hash, canonical_version) VALUES ('06FBHCXFF5V1RT6QJETS2K4C0G', 'status', 'in_progress', 'done', NULL, '2026-06-12 00:23:13', '2026-06-12 00:23:13', '2026-06-12 00:23:13', NULL, '8c817e20084503af9ab849d4974eef97', 2) ON CONFLICT(hash) DO NOTHING;
+INSERT INTO ticket_history (ticket_record_id, field, old_value, new_value, changed_by, changed_at, created_at, updated_at, deleted_at, hash, canonical_version) VALUES ('06FBHCXFF5V1RT6QJETS2K4C0G', 'description', 'Verified-dead code worth one sweep (coverage denominator benefits too):
+
+- Legacy free-function git API (~250 LOC duplicating GitClient, kept alive only by its own tests, and carrying its own latent pipe-deadlock bug) — delete API + tests.
+- ToolCheck — zero callers.
+- ~60% of lib/src/pty/ffi/libc.dart — fd-passing-era bindings unused since D-56.
+- GraphView — unreachable placeholder (note: the Governance Graph idea (see Q-records from this review) may later want the slot; deleting now is still right, it is a 17-line stub).
+- ColumnHat — duplicated line-for-line in app.dart, kept alive by a zero-coverage test; the app.dart split ticket removes the duplicate, this sweep removes the orphan.
+- tmux-era team pipeline: TranscriptPublisher, TeamMemberJoined — nothing emits these events, yet the team roster UI listens to them exclusively (team tiles are populated by ghosts). Remove pipeline + dead listeners; if the roster UI stays, it needs a real data source first (surface that before deleting the UI).
+- Dead ptyc binary still committed in native/linux-x64/ against D-62/D-63 — remove binary + licenses.yaml entry if present.
+- mocktail — pinned, documented in D-25 as the IO-mocking strategy, imported by zero files: either adopt it where mocks are hand-rolled or drop the dep AND amend D-25.
+
+Each bullet is one commit. Run make test + coverage after each; expect the floor to ratchet up.
+
+Correction (2026-06-12, verified during T-394 breakdown): ColumnHat is NOT duplicated line-for-line in app.dart — it exists only in lib/widgets/src/clide_column_hat.dart. Before deleting it, verify it actually has zero non-test callers; if it is genuinely used by app chrome, drop that bullet from this sweep.', 'Verified-dead code worth one sweep (coverage denominator benefits too):
+
+- Legacy free-function git API (~250 LOC duplicating GitClient, kept alive only by its own tests, and carrying its own latent pipe-deadlock bug) — delete API + tests.
+- ToolCheck — zero callers.
+- ~60% of lib/src/pty/ffi/libc.dart — fd-passing-era bindings unused since D-56.
+- GraphView — unreachable placeholder (note: the Governance Graph idea (see Q-records from this review) may later want the slot; deleting now is still right, it is a 17-line stub).
+- ColumnHat — duplicated line-for-line in app.dart, kept alive by a zero-coverage test; the app.dart split ticket removes the duplicate, this sweep removes the orphan.
+- tmux-era team pipeline: TranscriptPublisher, TeamMemberJoined — nothing emits these events, yet the team roster UI listens to them exclusively (team tiles are populated by ghosts). Remove pipeline + dead listeners; if the roster UI stays, it needs a real data source first (surface that before deleting the UI).
+- Dead ptyc binary still committed in native/linux-x64/ against D-62/D-63 — remove binary + licenses.yaml entry if present.
+- mocktail — pinned, documented in D-25 as the IO-mocking strategy, imported by zero files: either adopt it where mocks are hand-rolled or drop the dep AND amend D-25.
+
+Each bullet is one commit. Run make test + coverage after each; expect the floor to ratchet up.
+
+Correction (2026-06-12, verified during T-394 breakdown): ColumnHat is NOT duplicated line-for-line in app.dart — it exists only in lib/widgets/src/clide_column_hat.dart. Before deleting it, verify it actually has zero non-test callers; if it is genuinely used by app chrome, drop that bullet from this sweep.
+
+Done 2026-06-12 across six commits. Notes: ColumnHat''s file carried the LIVE hatHeight constant (app hat bar + menu bar) — moved to widgets/src/chrome_metrics.dart before deleting the dead widget. TranscriptPublisher class removed; the ClaudeConversation addressing constants stay (still consumed). The TeamMemberJoined ghost-event rewiring is real work, split out as T-396. mocktail dropped with D-25 amended (hand-rolled fakes throughout). ptyc binary untracked+deleted (no licenses.yaml entry existed). Coverage rose 95.03% → 95.13% with the dead denominator gone; full push-check green.', NULL, '2026-06-12 00:23:24', '2026-06-12 00:23:24', '2026-06-12 00:23:24', NULL, '0791573d68f344d3edab4cd8b89d2d69', 2) ON CONFLICT(hash) DO NOTHING;
+INSERT INTO ticket_history (ticket_record_id, field, old_value, new_value, changed_by, changed_at, created_at, updated_at, deleted_at, hash, canonical_version) VALUES ('06FBHDGPXQN31NNRPJ00PFRAG4', 'status', 'backlog', 'in_progress', NULL, '2026-06-12 00:23:56', '2026-06-12 00:23:56', '2026-06-12 00:23:56', NULL, 'e2cf08e3a17b8f8ad8288061d263744c', 2) ON CONFLICT(hash) DO NOTHING;
@@ -4252,3 +4252,50 @@ INSERT INTO tickets (record_id, type, parent_record_id, title, description, stat
 Fix: drive both roster surfaces from TeamBroker membership (expose a listenable roster or change stream on the broker), delete TeamMemberJoined/TeamMemberLeft from kernel events/types.dart, and remove the dead listeners. Coordinate with T-395 (meta sidebar split) — whichever lands second adapts.

 Acceptance: spawning a team session through the orchestrator makes the member appear in both surfaces (widget test); the ghost event types are gone from types.dart; no kernel.events team-member subscriptions remain.', 'backlog', 'medium', NULL, NULL, NULL, '2026-06-12 00:11:50', '2026-06-12 00:12:04', NULL, '57f7e568fe7c411fc4b45c6b140d8167', 2) ON CONFLICT(record_id) DO UPDATE SET type=excluded.type, parent_record_id=excluded.parent_record_id, title=excluded.title, description=excluded.description, status=excluded.status, priority=excluded.priority, assigned_to=excluded.assigned_to, team=excluded.team, decision_ref=excluded.decision_ref, updated_at=excluded.updated_at, deleted_at=excluded.deleted_at, hash=excluded.hash, canonical_version=excluded.canonical_version WHERE excluded.updated_at > tickets.updated_at OR (excluded.updated_at = tickets.updated_at AND excluded.hash > tickets.hash);
+INSERT INTO tickets (record_id, type, parent_record_id, title, description, status, priority, assigned_to, team, decision_ref, created_at, updated_at, deleted_at, hash, canonical_version) VALUES ('06FBHCXFF5V1RT6QJETS2K4C0G', 'task', '06FBHBGHNEQTAEPGNJKN42C1E8', 'Rat extermination: dead-code sweep (legacy git API, ToolCheck, libc, GraphView, ColumnHat, tmux-era team pipeline, ptyc binary, mocktail)', 'Verified-dead code worth one sweep (coverage denominator benefits too):
+
+- Legacy free-function git API (~250 LOC duplicating GitClient, kept alive only by its own tests, and carrying its own latent pipe-deadlock bug) — delete API + tests.
+- ToolCheck — zero callers.
+- ~60% of lib/src/pty/ffi/libc.dart — fd-passing-era bindings unused since D-56.
+- GraphView — unreachable placeholder (note: the Governance Graph idea (see Q-records from this review) may later want the slot; deleting now is still right, it is a 17-line stub).
+- ColumnHat — duplicated line-for-line in app.dart, kept alive by a zero-coverage test; the app.dart split ticket removes the duplicate, this sweep removes the orphan.
+- tmux-era team pipeline: TranscriptPublisher, TeamMemberJoined — nothing emits these events, yet the team roster UI listens to them exclusively (team tiles are populated by ghosts). Remove pipeline + dead listeners; if the roster UI stays, it needs a real data source first (surface that before deleting the UI).
+- Dead ptyc binary still committed in native/linux-x64/ against D-62/D-63 — remove binary + licenses.yaml entry if present.
+- mocktail — pinned, documented in D-25 as the IO-mocking strategy, imported by zero files: either adopt it where mocks are hand-rolled or drop the dep AND amend D-25.
+
+Each bullet is one commit. Run make test + coverage after each; expect the floor to ratchet up.
+
+Correction (2026-06-12, verified during T-394 breakdown): ColumnHat is NOT duplicated line-for-line in app.dart — it exists only in lib/widgets/src/clide_column_hat.dart. Before deleting it, verify it actually has zero non-test callers; if it is genuinely used by app chrome, drop that bullet from this sweep.', 'done', 'low', NULL, NULL, NULL, '2026-06-11 22:00:44', '2026-06-12 00:23:13', NULL, '9563a30ce5944315595343d612572909', 2) ON CONFLICT(record_id) DO UPDATE SET type=excluded.type, parent_record_id=excluded.parent_record_id, title=excluded.title, description=excluded.description, status=excluded.status, priority=excluded.priority, assigned_to=excluded.assigned_to, team=excluded.team, decision_ref=excluded.decision_ref, updated_at=excluded.updated_at, deleted_at=excluded.deleted_at, hash=excluded.hash, canonical_version=excluded.canonical_version WHERE excluded.updated_at > tickets.updated_at OR (excluded.updated_at = tickets.updated_at AND excluded.hash > tickets.hash);
+INSERT INTO tickets (record_id, type, parent_record_id, title, description, status, priority, assigned_to, team, decision_ref, created_at, updated_at, deleted_at, hash, canonical_version) VALUES ('06FBHCXFF5V1RT6QJETS2K4C0G', 'task', '06FBHBGHNEQTAEPGNJKN42C1E8', 'Rat extermination: dead-code sweep (legacy git API, ToolCheck, libc, GraphView, ColumnHat, tmux-era team pipeline, ptyc binary, mocktail)', 'Verified-dead code worth one sweep (coverage denominator benefits too):
+
+- Legacy free-function git API (~250 LOC duplicating GitClient, kept alive only by its own tests, and carrying its own latent pipe-deadlock bug) — delete API + tests.
+- ToolCheck — zero callers.
+- ~60% of lib/src/pty/ffi/libc.dart — fd-passing-era bindings unused since D-56.
+- GraphView — unreachable placeholder (note: the Governance Graph idea (see Q-records from this review) may later want the slot; deleting now is still right, it is a 17-line stub).
+- ColumnHat — duplicated line-for-line in app.dart, kept alive by a zero-coverage test; the app.dart split ticket removes the duplicate, this sweep removes the orphan.
+- tmux-era team pipeline: TranscriptPublisher, TeamMemberJoined — nothing emits these events, yet the team roster UI listens to them exclusively (team tiles are populated by ghosts). Remove pipeline + dead listeners; if the roster UI stays, it needs a real data source first (surface that before deleting the UI).
+- Dead ptyc binary still committed in native/linux-x64/ against D-62/D-63 — remove binary + licenses.yaml entry if present.
+- mocktail — pinned, documented in D-25 as the IO-mocking strategy, imported by zero files: either adopt it where mocks are hand-rolled or drop the dep AND amend D-25.
+
+Each bullet is one commit. Run make test + coverage after each; expect the floor to ratchet up.
+
+Correction (2026-06-12, verified during T-394 breakdown): ColumnHat is NOT duplicated line-for-line in app.dart — it exists only in lib/widgets/src/clide_column_hat.dart. Before deleting it, verify it actually has zero non-test callers; if it is genuinely used by app chrome, drop that bullet from this sweep.
+
+Done 2026-06-12 across six commits. Notes: ColumnHat''s file carried the LIVE hatHeight constant (app hat bar + menu bar) — moved to widgets/src/chrome_metrics.dart before deleting the dead widget. TranscriptPublisher class removed; the ClaudeConversation addressing constants stay (still consumed). The TeamMemberJoined ghost-event rewiring is real work, split out as T-396. mocktail dropped with D-25 amended (hand-rolled fakes throughout). ptyc binary untracked+deleted (no licenses.yaml entry existed). Coverage rose 95.03% → 95.13% with the dead denominator gone; full push-check green.', 'done', 'low', NULL, NULL, NULL, '2026-06-11 22:00:44', '2026-06-12 00:23:24', NULL, '0fedb8cda245d2ac1ece80f565e53049', 2) ON CONFLICT(record_id) DO UPDATE SET type=excluded.type, parent_record_id=excluded.parent_record_id, title=excluded.title, description=excluded.description, status=excluded.status, priority=excluded.priority, assigned_to=excluded.assigned_to, team=excluded.team, decision_ref=excluded.decision_ref, updated_at=excluded.updated_at, deleted_at=excluded.deleted_at, hash=excluded.hash, canonical_version=excluded.canonical_version WHERE excluded.updated_at > tickets.updated_at OR (excluded.updated_at = tickets.updated_at AND excluded.hash > tickets.hash);
+INSERT INTO tickets (record_id, type, parent_record_id, title, description, status, priority, assigned_to, team, decision_ref, created_at, updated_at, deleted_at, hash, canonical_version) VALUES ('06FBHDGPXQN31NNRPJ00PFRAG4', 'task', '06FBHBGHNEQTAEPGNJKN42C1E8', 'Split lib/app.dart (1187 LOC, five concerns)', 'lib/app.dart is 1187 LOC mixing five confirmed concerns. Split plan (verified against the file 2026-06-12):
+
+Inventory: ClideApp (14-29), _AppRoot (31-45), _RootShell/_RootShellState keyboard+intent routing (47-229), RootLayout (231-350), hat bar family _HatBar/_LeftHatContent/_RightHatContent/_WinBtn (352-439), project switcher family _ProjectSwitcherButton/_ProjectSwitcherDropdown/_RecentProjectRow/_ActionRow (441-672), SlotHost/_SlotHostState/_SlotBody/_SidebarSlot/_WorkspaceSlot/_RevealedTab/_ContextSlot (674-1030), _BottomRail (1032-1078), StatusbarCollapseToggle (1093-1126), StatusbarHost (1128-1170), _EditorDragHandle (924-1010), _WelcomeOverlay (1172-1187).
+
+Target layout:
+- app.dart keeps ClideApp + _AppRoot and RE-EXPORTS the public symbols so tests keep importing package:clide/app.dart.
+- lib/widgets/root_shell.dart: _RootShell/_RootShellState (keyboard routing; depends on ModifierTapTracker, MenuBarController).
+- lib/builtin/hat/hat_bar.dart: _HatBar, _LeftHatContent, _RightHatContent, _WinBtn, hatHeight.
+- lib/builtin/hat/project_switcher.dart: the switcher family (~230 LOC).
+- lib/widgets/slot_host.dart: SlotHost + slot bodies (NOTE: _RevealedTab references _SlotBody._resolveTitle — keep them together or extract the helper).
+- lib/widgets/layout_status.dart: RootLayout internals, StatusbarHost, StatusbarCollapseToggle, _BottomRail, _EditorDragHandle(+Intent), _WelcomeOverlay.
+
+Order: mechanical first (hat bar, switcher rows, welcome overlay), then root shell, then slot host (tangled: _SlotHostState registers focus scopes via ClideKernel.of in didChangeDependencies), then layout/status.
+
+Tests importing app.dart: test/app_test.dart (RootLayout, StatusbarHost, ClideApp), test/app_statusbar_test.dart (StatusbarHost), test/app_collapse_toggle_test.dart (StatusbarCollapseToggle) — re-exports keep them unchanged.
+
+CORRECTION to fable-ous.md: ColumnHat is NOT duplicated line-for-line in app.dart (verified); ColumnHat lives only in lib/widgets/src/clide_column_hat.dart. The rat-sweep ticket T-385 was annotated accordingly — verify whether ColumnHat is dead before deleting.', 'in_progress', 'medium', NULL, NULL, NULL, '2026-06-11 22:03:21', '2026-06-12 00:23:56', NULL, '06f8ead95c7934a07b4b74813f74f001', 2) ON CONFLICT(record_id) DO UPDATE SET type=excluded.type, parent_record_id=excluded.parent_record_id, title=excluded.title, description=excluded.description, status=excluded.status, priority=excluded.priority, assigned_to=excluded.assigned_to, team=excluded.team, decision_ref=excluded.decision_ref, updated_at=excluded.updated_at, deleted_at=excluded.deleted_at, hash=excluded.hash, canonical_version=excluded.canonical_version WHERE excluded.updated_at > tickets.updated_at OR (excluded.updated_at = tickets.updated_at AND excluded.hash > tickets.hash);
@@ -0,0 +1,101 @@
+/// The top window-chrome bar (D-57): drag region, menu bar, project
+/// switcher, window controls. Split out of app.dart (T-394).
+library;
+
+import 'dart:io' show Platform;
+
+import 'package:clide/builtin/menubar/menubar.dart';
+import 'package:clide/kernel/kernel.dart';
+import 'package:clide/src/shell/project_switcher.dart';
+import 'package:clide/widgets/widgets.dart';
+import 'package:flutter/foundation.dart' show kIsWeb;
+import 'package:flutter/widgets.dart';
+
+class HatBar extends StatelessWidget {
+  const HatBar({super.key, required this.kernel, required this.menuBar});
+  final KernelServices kernel;
+  final MenuBarController menuBar;
+
+  @override
+  Widget build(BuildContext context) {
+    final tokens = ClideTheme.of(context).surface;
+    return GestureDetector(
+      onPanStart: (_) => kernel.window.startDrag(),
+      child: Container(
+        height: hatHeight,
+        decoration: BoxDecoration(
+          color: tokens.chromeBackground,
+          border: Border(bottom: BorderSide(color: tokens.chromeBorder, width: 1)),
+        ),
+        padding: const EdgeInsets.symmetric(horizontal: 8),
+        child: Row(
+          children: [
+            _LeftHatContent(tokens: tokens, wc: kernel.window),
+            MenuBar(controller: menuBar),
+            Expanded(
+              child: Center(
+                child: ProjectSwitcherButton(kernel: kernel, tokens: tokens),
+              ),
+            ),
+            _RightHatContent(tokens: tokens, wc: kernel.window),
+          ],
+        ),
+      ),
+    );
+  }
+}
+
+class _LeftHatContent extends StatelessWidget {
+  const _LeftHatContent({required this.tokens, required this.wc});
+  final SurfaceTokens tokens;
+  final WindowControls wc;
+
+  @override
+  Widget build(BuildContext context) {
+    if (kIsWeb) return const SizedBox.shrink();
+    // On macOS the native titlebar draws traffic lights; skip duplicates.
+    return const SizedBox.shrink();
+  }
+}
+
+class _RightHatContent extends StatelessWidget {
+  const _RightHatContent({required this.tokens, required this.wc});
+  final SurfaceTokens tokens;
+  final WindowControls wc;
+
+  @override
+  Widget build(BuildContext context) {
+    if (kIsWeb) return const SizedBox.shrink();
+    if (!kIsWeb && Platform.isMacOS) return const SizedBox.shrink();
+    return Row(
+      children: [
+        _WinBtn(icon: const PhosphorIconPainter(0xe32a), onTap: wc.minimize, tokens: tokens),
+        _WinBtn(icon: const PhosphorIconPainter(0xe45e), onTap: wc.toggleMaximize, tokens: tokens),
+        _WinBtn(icon: PhosphorIcons.byName('x'), onTap: wc.close, tokens: tokens, isClose: true),
+      ],
+    );
+  }
+}
+
+class _WinBtn extends StatelessWidget {
+  const _WinBtn({required this.icon, required this.onTap, required this.tokens, this.isClose = false});
+  final ClideIconPainter icon;
+  final VoidCallback onTap;
+  final SurfaceTokens tokens;
+  final bool isClose;
+
+  @override
+  Widget build(BuildContext context) {
+    final hoverBg = isClose ? tokens.windowControlCloseHoverBackground : tokens.listItemHoverBackground;
+    return ClideTappable(
+      onTap: onTap,
+      builder: (context, hovered, _) => Container(
+        width: 36,
+        height: hatHeight,
+        color: hovered ? hoverBg : null,
+        alignment: Alignment.center,
+        child: ClideIcon(icon, size: 14, color: hovered && isClose ? tokens.windowControlCloseHoverForeground : tokens.chromeForeground),
+      ),
+    );
+  }
+}
@@ -0,0 +1,270 @@
+/// The root three-column layout grid, the status bar, and its
+/// collapse toggles + bottom icon rails. Split out of app.dart (T-394).
+library;
+
+import 'package:clide/extension/src/contribution.dart';
+import 'package:clide/kernel/kernel.dart';
+import 'package:clide/src/shell/slot_host.dart';
+import 'package:clide/widgets/widgets.dart';
+import 'package:flutter/widgets.dart';
+
+class RootLayout extends StatelessWidget {
+  const RootLayout({super.key});
+
+  @override
+  Widget build(BuildContext context) {
+    final kernel = ClideKernel.of(context);
+    return ListenableBuilder(
+      listenable: Listenable.merge([kernel.panels, kernel.arrangement]),
+      builder: (ctx, _) {
+        final a = kernel.arrangement;
+        final sidebarVisible = a.isVisible(Slots.sidebar);
+        final sidebarCollapsed = a.isCollapsed(Slots.sidebar);
+        final contextVisible = a.isVisible(Slots.contextPanel);
+        final contextCollapsed = a.isCollapsed(Slots.contextPanel);
+        final statusVisible = a.isVisible(Slots.statusbar);
+        final sidebarSize = a.sizeOf(Slots.sidebar) ?? 400;
+        final contextSize = a.sizeOf(Slots.contextPanel) ?? 420;
+        final statusHeight = a.sizeOf(Slots.statusbar) ?? 26;
+        // Bottom output dock (T-54 / D-87): pushes the workspace up when open,
+        // capped at half the window so Claude stays the largest surface (the
+        // D-47 amendment).
+        final dockVisible = a.isVisible(Slots.dock);
+        final dockMax = (((MediaQuery.of(ctx).size.height) - statusHeight) * 0.5).clamp(80.0, double.infinity).toDouble();
+        final dockHeight = dockVisible ? ((a.sizeOf(Slots.dock) ?? 200).clamp(0.0, dockMax)).toDouble() : 0.0;
+
+        final column = Column(
+          children: [
+            Expanded(
+              child: Row(
+                children: [
+                  if (sidebarVisible && sidebarCollapsed)
+                    ClideSpine(label: _sidebarSpineLabel(kernel), side: SpineSide.left, onExpand: () => a.setCollapsed(Slots.sidebar, false))
+                  else if (sidebarVisible) ...[
+                    SizedBox(
+                      width: sidebarSize,
+                      child: SlotHost(slot: Slots.sidebar),
+                    ),
+                    DragResizeHandle(arrangement: a, slot: Slots.sidebar, axis: Axis.horizontal),
+                  ],
+                  const Expanded(child: SlotHost(slot: Slots.workspace)),
+                  if (contextVisible && contextCollapsed)
+                    ClideSpine(label: 'context', side: SpineSide.right, onExpand: () => a.setCollapsed(Slots.contextPanel, false))
+                  else if (contextVisible) ...[
+                    DragResizeHandle(arrangement: a, slot: Slots.contextPanel, axis: Axis.horizontal),
+                    SizedBox(
+                      width: contextSize,
+                      child: SlotHost(slot: Slots.contextPanel),
+                    ),
+                  ],
+                ],
+              ),
+            ),
+            if (dockVisible)
+              SizedBox(
+                height: dockHeight,
+                child: DecoratedBox(
+                  decoration: BoxDecoration(
+                    border: Border(top: BorderSide(color: ClideTheme.of(ctx).surface.chromeBorder)),
+                  ),
+                  child: SlotHost(slot: Slots.dock),
+                ),
+              ),
+            if (statusVisible)
+              Container(
+                height: statusHeight,
+                decoration: BoxDecoration(
+                  border: Border(top: BorderSide(color: ClideTheme.of(ctx).surface.chromeBorder)),
+                ),
+                child: Row(
+                  crossAxisAlignment: CrossAxisAlignment.stretch,
+                  children: [
+                    // Collapse toggles are pinned to the screen edges (outermost
+                    // children) so they never shift when a pane collapses (T-294).
+                    StatusbarCollapseToggle(slot: Slots.sidebar, collapsed: sidebarCollapsed, visible: sidebarVisible),
+                    if (sidebarVisible && !sidebarCollapsed)
+                      SizedBox(
+                        width: sidebarSize,
+                        child: _BottomRail(slot: Slots.sidebar),
+                      )
+                    else if (sidebarVisible && sidebarCollapsed)
+                      const SizedBox(width: ClideSpine.width),
+                    const Expanded(child: StatusbarHost()),
+                    if (contextVisible && !contextCollapsed)
+                      SizedBox(
+                        width: contextSize,
+                        child: _BottomRail(slot: Slots.contextPanel),
+                      )
+                    else if (contextVisible && contextCollapsed)
+                      const SizedBox(width: ClideSpine.width),
+                    StatusbarCollapseToggle(slot: Slots.contextPanel, collapsed: contextCollapsed, visible: contextVisible),
+                  ],
+                ),
+              ),
+          ],
+        );
+        // When the status bar is hidden it no longer occupies the window's
+        // bottom edge, so the bottom-most content (the Claude composer, an
+        // editor, a terminal) would otherwise run flush into the resize-drag
+        // strip and look jammed against the window bottom (T-298). Reserve a
+        // matching inset so the interaction zone bottom-anchors consistently,
+        // independent of status-bar visibility.
+        if (statusVisible) return column;
+        return Padding(
+          padding: const EdgeInsets.only(bottom: ClideResizeBorder.edgeThickness),
+          child: column,
+        );
+      },
+    );
+  }
+
+  static String _sidebarSpineLabel(KernelServices kernel) {
+    final activeTab = kernel.panels.activeTabIn(Slots.sidebar);
+    if (activeTab == null) return 'overview';
+    final tabs = kernel.panels.tabsFor(Slots.sidebar);
+    for (final t in tabs) {
+      if (t.id == activeTab) return t.title.toLowerCase();
+    }
+    return 'overview';
+  }
+}
+
+class _BottomRail extends StatelessWidget {
+  const _BottomRail({required this.slot});
+  final SlotId slot;
+
+  @override
+  Widget build(BuildContext context) {
+    final kernel = ClideKernel.of(context);
+    final tokens = ClideTheme.of(context).surface;
+    return ListenableBuilder(
+      listenable: kernel.panels,
+      builder: (ctx, _) {
+        final tabs = kernel.panels.tabsFor(slot);
+        if (tabs.isEmpty) return Container(color: tokens.chromeBackground);
+        final activeId = kernel.panels.activeTabIn(slot) ?? tabs.first.id;
+        return Container(
+          color: tokens.chromeBackground,
+          child: ClideIconRail(
+            items: [for (final t in tabs) ClideIconRailItem(id: t.id, icon: _iconFor(slot, t), tooltip: resolveTabTitle(ctx, t))],
+            activeId: activeId,
+            onSelect: (id) => kernel.panels.activateTab(slot, id),
+          ),
+        );
+      },
+    );
+  }
+
+  static ClideIconPainter _iconFor(SlotId slot, TabContribution t) {
+    if (t.icon is ClideIconPainter) return t.icon as ClideIconPainter;
+    if (slot == Slots.sidebar) {
+      return switch (t.id) {
+        'files.tree' => PhosphorIcons.byName('folder'),
+        'git.panel' => PhosphorIcons.byName('git-branch'),
+        'pql.panel' => PhosphorIcons.byName('magnifying-glass'),
+        'problems.panel' => PhosphorIcons.byName('warning-circle'),
+        'decisions.panel' => PhosphorIcons.byName('lightbulb'),
+        'tickets.panel' => PhosphorIcons.byName('ticket'),
+        _ => PhosphorIcons.byName('circles-four'),
+      };
+    }
+    return switch (t.id) {
+      'markdown.viewer' => PhosphorIcons.byName('eye'),
+      'graph.view' => PhosphorIcons.byName('graph'),
+      'pql.backlinks' => PhosphorIcons.byName('link'),
+      _ => PhosphorIcons.byName('circles-four'),
+    };
+  }
+}
+
+/// A fixed-position collapse/expand toggle bookending the status bar (T-294).
+/// The left cell controls the sidebar, the right cell the context pane; both
+/// fire the existing `sidebar.collapse` / `context.collapse` commands and flip a
+/// caret-line chevron per `arrangement.isCollapsed` (outward = expand, inward =
+/// collapse). The collapse behaviour itself lives in the commands (D-51/D-54);
+/// this is the mouse affordance for the keyboard/CLI-addressable action (D-6).
+/// A fixed collapse/expand toggle pinned to a screen edge of the status bar
+/// (T-294). Lives at the outer ends of the bar — NOT inside the centre
+/// [StatusbarHost] — so it never shifts when a pane collapses and the centre
+/// bar resizes. [collapsed]/[visible] are passed in (not read from the
+/// arrangement here) so the widget varies with state and rebuilds when its
+/// parent's `ListenableBuilder` fires — a const widget reading the arrangement
+/// itself is skipped as identical on rebuild, freezing the chevron.
+class StatusbarCollapseToggle extends StatelessWidget {
+  const StatusbarCollapseToggle({super.key, required this.slot, required this.collapsed, required this.visible});
+
+  final SlotId slot;
+  final bool collapsed;
+  final bool visible;
+
+  bool get _isSidebar => slot == Slots.sidebar;
+
+  @override
+  Widget build(BuildContext context) {
+    final kernel = ClideKernel.of(context);
+    final tokens = ClideTheme.of(context).surface;
+    if (!visible) return const SizedBox(width: 24);
+    // The chevron points the DIRECTION OF THE ACTION: collapsing tucks the pane
+    // toward its own edge, expanding brings it back toward the centre.
+    final icon = _isSidebar
+        ? (collapsed ? PhosphorIcons.byName('caret-line-right') : PhosphorIcons.byName('caret-line-left'))
+        : (collapsed ? PhosphorIcons.byName('caret-line-left') : PhosphorIcons.byName('caret-line-right'));
+    final what = _isSidebar ? 'sidebar' : 'context panel';
+    return SizedBox(
+      width: 24,
+      child: ClideTappable(
+        onTap: () => kernel.commands.execute(_isSidebar ? 'sidebar.collapse' : 'context.collapse'),
+        tooltip: collapsed ? 'Show $what' : 'Hide $what',
+        builder: (ctx, hovered, focused) => Container(
+          alignment: Alignment.center,
+          color: (hovered || focused) ? tokens.listItemHoverBackground : null,
+          child: ClideIcon(icon, size: 13, color: tokens.statusBarForeground),
+        ),
+      ),
+    );
+  }
+}
+
+class StatusbarHost extends StatelessWidget {
+  const StatusbarHost({super.key});
+
+  @override
+  Widget build(BuildContext context) {
+    final kernel = ClideKernel.of(context);
+    final tokens = ClideTheme.of(context).surface;
+    return ListenableBuilder(
+      listenable: kernel.panels,
+      builder: (ctx, _) {
+        final items = kernel.panels.contributionsFor(Slots.statusbar).whereType<StatusItemContribution>().toList();
+        final left = items.where((i) => i.priority < 100).toList();
+        final right = items.where((i) => i.priority >= 100).toList();
+        // Two explicit columns within the center (workspace) bar: the LEFT
+        // group lives in an Expanded so it absorbs all free space and is
+        // start-aligned, and the RIGHT group (tool status, theme switcher)
+        // trails it at intrinsic width — so it hugs the workspace block's
+        // right edge by construction, no Spacer to fight a flex item (T-239).
+        // Left items with flex > 0 wrap in Flexible(loose) so they yield width
+        // when tight (T-160).
+        return Container(
+          color: tokens.chromeBackground,
+          padding: const EdgeInsets.symmetric(horizontal: 8),
+          child: Row(
+            crossAxisAlignment: CrossAxisAlignment.center,
+            children: [
+              Expanded(
+                child: Row(
+                  crossAxisAlignment: CrossAxisAlignment.center,
+                  children: [
+                    for (final item in left)
+                      if (item.flex > 0) Flexible(flex: item.flex, fit: FlexFit.loose, child: item.build(ctx)) else item.build(ctx),
+                  ],
+                ),
+              ),
+              for (final item in right) item.build(ctx),
+            ],
+          ),
+        );
+      },
+    );
+  }
+}
@@ -0,0 +1,245 @@
+/// The hat bar's project switcher: current-project label opening a
+/// recents + file-actions dropdown. Split out of app.dart (T-394).
+library;
+
+import 'dart:async';
+import 'dart:io' show Platform;
+
+import 'package:clide/clide.dart' show clideName;
+import 'package:clide/kernel/kernel.dart';
+import 'package:clide/widgets/widgets.dart';
+import 'package:flutter/services.dart';
+import 'package:flutter/widgets.dart';
+
+class ProjectSwitcherButton extends StatelessWidget {
+  const ProjectSwitcherButton({super.key, required this.kernel, required this.tokens});
+  final KernelServices kernel;
+  final SurfaceTokens tokens;
+
+  void _openSwitcher() {
+    kernel.dialog.show<String>((ctx, dismiss) {
+      return _ProjectSwitcherDropdown(kernel: kernel, onDismiss: dismiss);
+    });
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return ListenableBuilder(
+      listenable: kernel.project,
+      builder: (ctx, _) {
+        final name = kernel.project.current?.path.split('/').last;
+        final label = name != null ? '$clideName > $name' : clideName;
+        return ClideTappable(
+          onTap: _openSwitcher,
+          builder: (context, hovered, _) => Row(
+            mainAxisSize: MainAxisSize.min,
+            children: [
+              ClideText(label, fontSize: 12, color: hovered ? tokens.globalForeground : tokens.chromeForeground, fontFamily: clideMonoFamily),
+              const SizedBox(width: 4),
+              ClideIcon(PhosphorIcons.byName('caret-down'), size: 8, color: tokens.chromeForeground),
+            ],
+          ),
+        );
+      },
+    );
+  }
+}
+
+class _ProjectSwitcherDropdown extends StatefulWidget {
+  const _ProjectSwitcherDropdown({required this.kernel, required this.onDismiss});
+  final KernelServices kernel;
+  final void Function([String?]) onDismiss;
+
+  @override
+  State<_ProjectSwitcherDropdown> createState() => _ProjectSwitcherDropdownState();
+}
+
+class _ProjectSwitcherDropdownState extends State<_ProjectSwitcherDropdown> {
+  String _filter = '';
+  late final FocusNode _focus;
+
+  @override
+  void initState() {
+    super.initState();
+    _focus = FocusNode()..requestFocus();
+  }
+
+  @override
+  void dispose() {
+    _focus.dispose();
+    super.dispose();
+  }
+
+  Future<void> _openProject(String path) async {
+    final ok = await widget.kernel.project.open(path);
+    if (ok) {
+      widget.kernel.panels.activateTab(Slots.workspace, 'claude.primary');
+      widget.onDismiss();
+    }
+  }
+
+  // File actions now live as commands (file.openFolder / file.newWindow /
+  // file.closeWorkspace) owned by the menu-bar extension (T-48). The switcher
+  // dismisses itself and dispatches the command so both surfaces share one
+  // implementation.
+  void _runFileCommand(String command) {
+    widget.onDismiss();
+    unawaited(widget.kernel.commands.execute(command));
+  }
+
+  KeyEventResult _onKey(FocusNode node, KeyEvent event) {
+    if (event is KeyDownEvent && event.logicalKey == LogicalKeyboardKey.escape) {
+      widget.onDismiss();
+      return KeyEventResult.handled;
+    }
+    return KeyEventResult.ignored;
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    final tokens = ClideTheme.of(context).surface;
+    final recents = widget.kernel.project.recents;
+    final lf = _filter.toLowerCase();
+    final filtered = lf.isEmpty ? recents : recents.where((r) => r.name.toLowerCase().contains(lf) || r.path.toLowerCase().contains(lf)).toList();
+
+    return Focus(
+      focusNode: _focus,
+      onKeyEvent: _onKey,
+      child: Container(
+        width: 480,
+        constraints: const BoxConstraints(maxHeight: 420),
+        decoration: BoxDecoration(
+          color: tokens.dropdownBackground,
+          border: Border.all(color: tokens.dropdownBorder),
+          borderRadius: BorderRadius.circular(6),
+        ),
+        child: Column(
+          mainAxisSize: MainAxisSize.min,
+          crossAxisAlignment: CrossAxisAlignment.stretch,
+          children: [
+            ClideFilterBox(hint: 'Search projects…', onChanged: (v) => setState(() => _filter = v)),
+            if (filtered.isNotEmpty) ...[
+              Padding(
+                padding: const EdgeInsets.symmetric(horizontal: 12, vertical: 4),
+                child: ClideText('Recent Projects', fontSize: clideFontCaption, color: tokens.globalTextMuted),
+              ),
+              Flexible(
+                child: ListView.builder(
+                  shrinkWrap: true,
+                  padding: EdgeInsets.zero,
+                  itemCount: filtered.length,
+                  itemBuilder: (ctx, i) => _RecentProjectRow(project: filtered[i], tokens: tokens, onTap: () => _openProject(filtered[i].path)),
+                ),
+              ),
+            ] else
+              const Padding(padding: EdgeInsets.all(12), child: ClideText('No recent projects.', muted: true)),
+            Container(
+              decoration: BoxDecoration(
+                border: Border(top: BorderSide(color: tokens.dividerColor)),
+              ),
+              child: Column(
+                children: [
+                  _ActionRow(
+                    label: 'Open Local Project',
+                    shortcut: Platform.isMacOS ? '⌘O' : 'Ctrl+O',
+                    tokens: tokens,
+                    onTap: () => _runFileCommand('file.openFolder'),
+                  ),
+                  _ActionRow(
+                    label: 'New Window',
+                    shortcut: Platform.isMacOS ? '⌘⇧N' : 'Ctrl+Shift+N',
+                    tokens: tokens,
+                    onTap: () => _runFileCommand('file.newWindow'),
+                  ),
+                  if (widget.kernel.project.isOpen)
+                    _ActionRow(label: 'Close Project', shortcut: '', tokens: tokens, onTap: () => _runFileCommand('file.closeWorkspace')),
+                ],
+              ),
+            ),
+          ],
+        ),
+      ),
+    );
+  }
+}
+
+class _RecentProjectRow extends StatelessWidget {
+  const _RecentProjectRow({required this.project, required this.tokens, required this.onTap});
+  final RecentProject project;
+  final SurfaceTokens tokens;
+  final VoidCallback onTap;
+
+  @override
+  Widget build(BuildContext context) {
+    return ClideTappable(
+      onTap: onTap,
+      builder: (context, hovered, _) => Container(
+        color: hovered ? tokens.listItemHoverBackground : null,
+        padding: const EdgeInsets.symmetric(horizontal: 12, vertical: 6),
+        child: Row(
+          children: [
+            ClideIcon(PhosphorIcons.byName('folder'), size: 14, color: tokens.globalTextMuted),
+            const SizedBox(width: 8),
+            Expanded(
+              child: Column(
+                crossAxisAlignment: CrossAxisAlignment.start,
+                children: [
+                  ClideText(project.name, fontSize: 14),
+                  if (project.branch != null)
+                    Row(
+                      children: [
+                        // Elide a long path instead of overflowing the row
+                        // (matches the welcome recents row; T-160 discipline).
+                        Flexible(
+                          child: ClideText(
+                            project.relativePath,
+                            muted: true,
+                            fontSize: 12,
+                            fontFamily: clideMonoFamily,
+                            maxLines: 1,
+                            overflow: TextOverflow.ellipsis,
+                          ),
+                        ),
+                        ClideText('  ·  ', muted: true, fontSize: 12),
+                        ClideIcon(PhosphorIcons.byName('git-branch'), size: 10, color: tokens.globalTextMuted),
+                        const SizedBox(width: 3),
+                        ClideText(project.branch!, muted: true, fontSize: 12, fontFamily: clideMonoFamily),
+                      ],
+                    )
+                  else
+                    ClideText(project.relativePath, muted: true, fontSize: 12, fontFamily: clideMonoFamily, maxLines: 1, overflow: TextOverflow.ellipsis),
+                ],
+              ),
+            ),
+            ClideText(project.timeAgo, muted: true, fontSize: 11),
+          ],
+        ),
+      ),
+    );
+  }
+}
+
+class _ActionRow extends StatelessWidget {
+  const _ActionRow({required this.label, this.shortcut, required this.tokens, required this.onTap});
+  final String label;
+  final String? shortcut;
+  final SurfaceTokens tokens;
+  final VoidCallback onTap;
+
+  @override
+  Widget build(BuildContext context) {
+    return ClideTappable(
+      onTap: onTap,
+      builder: (context, hovered, _) => Container(
+        color: hovered ? tokens.listItemHoverBackground : null,
+        padding: const EdgeInsets.symmetric(horizontal: 12, vertical: 8),
+        child: Row(
+          children: [
+            Expanded(child: ClideText(label, fontSize: 14)),
+            if (shortcut != null && shortcut!.isNotEmpty) ClideText(shortcut!, fontSize: 12, color: tokens.globalTextMuted, fontFamily: clideMonoFamily),
+          ],
+        ),
+      ),
+    );
+  }
+}
@@ -0,0 +1,215 @@
+/// The application root shell: global keyboard/intent routing (keymap
+/// resolution, double-tap modifiers, menu mnemonics), the hat bar, and
+/// the overlay stack (palette, quick-open, welcome, toasts). Split out
+/// of app.dart (T-394).
+library;
+
+import 'package:clide/builtin/menubar/menubar.dart';
+import 'package:clide/builtin/welcome/src/welcome_view.dart';
+import 'package:clide/kernel/kernel.dart';
+import 'package:clide/src/shell/hat_bar.dart';
+import 'package:clide/src/shell/layout.dart';
+import 'package:clide/widgets/widgets.dart';
+import 'package:flutter/services.dart';
+import 'package:flutter/widgets.dart';
+
+class RootShell extends StatefulWidget {
+  const RootShell({super.key, required this.services});
+  final KernelServices services;
+
+  @override
+  State<RootShell> createState() => RootShellState();
+}
+
+class RootShellState extends State<RootShell> {
+  late final FocusNode _keyFocus;
+  final MenuBarController _menuBar = MenuBarController();
+  // Detects double-tapped bare modifiers (e.g. double-Shift → quick-open,
+  // JetBrains "Search Everywhere"). Bare modifiers never resolve as a single
+  // chord, so this is the only path that handles them (T-341).
+  final ModifierTapTracker _modTap = ModifierTapTracker();
+
+  @override
+  void initState() {
+    super.initState();
+    _keyFocus = FocusNode()..requestFocus();
+    widget.services.textZoom.addListener(_onZoom);
+  }
+
+  @override
+  void dispose() {
+    widget.services.textZoom.removeListener(_onZoom);
+    _menuBar.dispose();
+    _keyFocus.dispose();
+    super.dispose();
+  }
+
+  void _onZoom() => setState(() {});
+
+  @override
+  Widget build(BuildContext context) {
+    final tokens = ClideTheme.of(context).surface;
+    return DefaultTextStyle(
+      style: TextStyle(
+        color: tokens.globalForeground,
+        fontSize: 15,
+        height: clideLineHeight,
+        fontWeight: clideUiDefaultWeight,
+        fontFamily: clideUiFamily,
+        fontFamilyFallback: clideUiFamilyFallback,
+      ),
+      child: MediaQuery(
+        data: MediaQuery.of(context).copyWith(textScaler: TextScaler.linear(widget.services.textZoom.scale)),
+        child: Actions(
+          actions: <Type, Action<Intent>>{
+            TextScaleIncreaseIntent: CallbackAction<TextScaleIncreaseIntent>(
+              onInvoke: (_) {
+                widget.services.textZoom.increase();
+                return null;
+              },
+            ),
+            TextScaleDecreaseIntent: CallbackAction<TextScaleDecreaseIntent>(
+              onInvoke: (_) {
+                widget.services.textZoom.decrease();
+                return null;
+              },
+            ),
+            TextScaleResetIntent: CallbackAction<TextScaleResetIntent>(
+              onInvoke: (_) {
+                widget.services.textZoom.reset();
+                return null;
+              },
+            ),
+            InvokeCommandIntent: CallbackAction<InvokeCommandIntent>(
+              onInvoke: (intent) {
+                widget.services.commands.execute(intent.commandId);
+                return null;
+              },
+            ),
+            PaletteOpenIntent: CallbackAction<PaletteOpenIntent>(
+              onInvoke: (_) {
+                widget.services.palette.open();
+                return null;
+              },
+            ),
+            QuickOpenIntent: CallbackAction<QuickOpenIntent>(
+              onInvoke: (_) {
+                widget.services.quickOpen.open();
+                return null;
+              },
+            ),
+            FindInFilesIntent: CallbackAction<FindInFilesIntent>(
+              onInvoke: (_) {
+                widget.services.arrangement.setVisible(Slots.sidebar, true);
+                widget.services.arrangement.setCollapsed(Slots.sidebar, false);
+                widget.services.panels.activateTab(Slots.sidebar, 'search.findInFiles');
+                return null;
+              },
+            ),
+            FocusNextPanelIntent: CallbackAction<FocusNextPanelIntent>(
+              onInvoke: (_) {
+                widget.services.focus.focusNextSlot();
+                return null;
+              },
+            ),
+            FocusPreviousPanelIntent: CallbackAction<FocusPreviousPanelIntent>(
+              onInvoke: (_) {
+                widget.services.focus.focusPreviousSlot();
+                return null;
+              },
+            ),
+          },
+          child: KeyboardListener(
+            focusNode: _keyFocus,
+            autofocus: true,
+            onKeyEvent: _onKey,
+            child: ColoredBox(
+              color: tokens.globalBackground,
+              child: ClideResizeBorder(
+                windowControls: widget.services.window,
+                child: Column(
+                  children: [
+                    HatBar(kernel: widget.services, menuBar: _menuBar),
+                    Expanded(
+                      child: DialogHost(
+                        router: widget.services.dialog,
+                        child: Stack(
+                          children: [
+                            const Positioned.fill(child: RootLayout()),
+                            const ClidePalette(),
+                            const QuickOpenOverlay(),
+                            const Positioned.fill(child: _WelcomeOverlay()),
+                            const ToastOverlay(),
+                          ],
+                        ),
+                      ),
+                    ),
+                  ],
+                ),
+              ),
+            ),
+          ),
+        ),
+      ),
+    );
+  }
+
+  void _onKey(KeyEvent event) {
+    if (_handleMenuMnemonic(event)) return;
+    // Double-tapped bare modifier (e.g. double-Shift → quick-open). Handle
+    // it here because a bare modifier never forms a single chord — an
+    // intervening non-modifier key breaks the gesture (T-341).
+    if (event is KeyDownEvent) {
+      final mod = KeyChord.modifierForLogicalKey(event.logicalKey);
+      if (mod != null) {
+        if (_modTap.tap(mod, DateTime.now()) != null) {
+          final seq = [KeyChord.bareModifier(mod), KeyChord.bareModifier(mod)];
+          final tapIntent = widget.services.keymap.resolveSequence(seq);
+          if (tapIntent != null) _dispatchIntent(tapIntent);
+        }
+        return; // a bare modifier resolves nothing else
+      }
+      _modTap.reset();
+    }
+    final intent = widget.services.keymap.resolveEvent(event, HardwareKeyboard.instance);
+    if (intent == null) return;
+    _dispatchIntent(intent);
+  }
+
+  void _dispatchIntent(Intent intent) {
+    // Try the focused context first so feature widgets (palette, editor, …)
+    // get a chance to handle their own intents; fall back to the app root's
+    // Actions for global ones (text scale, generic command bridge).
+    final ctx = FocusManager.instance.primaryFocus?.context ?? context;
+    Actions.maybeInvoke(ctx, intent);
+  }
+
+  /// `Alt+<mnemonic>` opens (or toggles) the matching application menu (T-48).
+  /// Returns true when consumed so it never falls through to keymap resolution.
+  bool _handleMenuMnemonic(KeyEvent event) {
+    if (event is! KeyDownEvent || !HardwareKeyboard.instance.isAltPressed) return false;
+    final label = event.logicalKey.keyLabel.toLowerCase();
+    if (label.length != 1) return false;
+    final idx = _menuBar.indexForMnemonic(label);
+    if (idx == null) return false;
+    _menuBar.toggle(idx);
+    return true;
+  }
+}
+
+class _WelcomeOverlay extends StatelessWidget {
+  const _WelcomeOverlay();
+
+  @override
+  Widget build(BuildContext context) {
+    final kernel = ClideKernel.of(context);
+    return ListenableBuilder(
+      listenable: kernel.project,
+      builder: (ctx, _) {
+        if (kernel.project.isOpen) return const SizedBox.shrink();
+        final tokens = ClideTheme.of(ctx).surface;
+        return ColoredBox(color: tokens.globalBackground, child: const WelcomeView());
+      },
+    );
+  }
+}
@@ -0,0 +1,372 @@
+/// Slot hosting: mounts a slot's tab contributions, integrates focus
+/// scopes, and renders the slot-specific bodies (sidebar / workspace
+/// split incl. the editor drag handle / context). Split out of
+/// app.dart (T-394).
+library;
+
+import 'package:clide/extension/src/contribution.dart';
+import 'package:clide/kernel/kernel.dart';
+import 'package:clide/widgets/widgets.dart';
+import 'package:flutter/services.dart';
+import 'package:flutter/widgets.dart';
+
+class SlotHost extends StatefulWidget {
+  const SlotHost({super.key, required this.slot});
+  final SlotId slot;
+
+  @override
+  State<SlotHost> createState() => _SlotHostState();
+}
+
+class _SlotHostState extends State<SlotHost> {
+  late final FocusScopeNode _scope = FocusScopeNode(debugLabel: 'SlotScope:${widget.slot.value}');
+  FocusTracker? _tracker;
+
+  @override
+  void didChangeDependencies() {
+    super.didChangeDependencies();
+    final kernel = ClideKernel.of(context);
+    if (!identical(_tracker, kernel.focus)) {
+      _tracker?.unregisterSlotScope(widget.slot, _scope);
+      _tracker = kernel.focus;
+      _tracker!.registerSlotScope(widget.slot, _scope);
+    }
+  }
+
+  @override
+  void dispose() {
+    _tracker?.unregisterSlotScope(widget.slot, _scope);
+    _scope.dispose();
+    super.dispose();
+  }
+
+  void _onFocusChange(bool hasFocus) {
+    if (!hasFocus || _tracker == null) return;
+    final kernel = ClideKernel.of(context);
+    final activeId = kernel.panels.activeTabIn(widget.slot);
+    if (activeId != null) {
+      _tracker!.setActive(slot: widget.slot, contributionId: activeId);
+    }
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    final kernel = ClideKernel.of(context);
+    final tokens = ClideTheme.of(context).surface;
+    return FocusScope(
+      node: _scope,
+      onFocusChange: _onFocusChange,
+      child: FocusTraversalGroup(
+        child: ListenableBuilder(
+          listenable: Listenable.merge([kernel.panels, kernel.i18n]),
+          builder: (ctx, _) {
+            final tabs = kernel.panels.tabsFor(widget.slot);
+            if (tabs.isEmpty) {
+              return Container(color: tokens.panelBackground);
+            }
+            final activeId = kernel.panels.activeTabIn(widget.slot) ?? tabs.first.id;
+            final active = tabs.firstWhere((t) => t.id == activeId, orElse: () => tabs.first);
+            return _SlotBody(slot: widget.slot, tabs: tabs, active: active, activeId: activeId);
+          },
+        ),
+      ),
+    );
+  }
+}
+
+class _SlotBody extends StatelessWidget {
+  const _SlotBody({required this.slot, required this.tabs, required this.active, required this.activeId});
+  final SlotId slot;
+  final List<TabContribution> tabs;
+  final TabContribution active;
+  final String activeId;
+
+  @override
+  Widget build(BuildContext context) {
+    final kernel = ClideKernel.of(context);
+    final tokens = ClideTheme.of(context).surface;
+
+    if (slot == Slots.sidebar) {
+      return _SidebarSlot(tabs: tabs, active: active, activeId: activeId, onSelect: (id) => kernel.panels.activateTab(slot, id));
+    }
+
+    if (slot == Slots.contextPanel) {
+      return _ContextSlot(tabs: tabs, active: active, activeId: activeId, onSelect: (id) => kernel.panels.activateTab(slot, id));
+    }
+
+    if (slot == Slots.workspace) {
+      return _WorkspaceSlot(tabs: tabs, active: active);
+    }
+
+    return Container(
+      color: tokens.panelBackground,
+      child: Column(
+        children: [
+          ClideTabBar(
+            items: [for (final t in tabs) ClideTabItem(id: t.id, title: resolveTabTitle(context, t))],
+            activeId: active.id,
+            onSelect: (id) => kernel.panels.activateTab(slot, id),
+          ),
+          ClideDivider(),
+          Expanded(child: active.build(context)),
+        ],
+      ),
+    );
+  }
+}
+
+class _SidebarSlot extends StatelessWidget {
+  const _SidebarSlot({required this.tabs, required this.active, required this.activeId, required this.onSelect});
+
+  final List<TabContribution> tabs;
+  final TabContribution active;
+  final String activeId;
+  final ValueChanged<String> onSelect;
+
+  @override
+  Widget build(BuildContext context) {
+    final tokens = ClideTheme.of(context).surface;
+    return Container(
+      color: tokens.chromeBackground,
+      alignment: Alignment.topLeft,
+      padding: const EdgeInsets.fromLTRB(2, 2, 0, 0),
+      child: active.build(context),
+    );
+  }
+}
+
+// Stable identity for the workspace's primary pane (Claude). Opening the
+// editor reparents it from a direct child into a Column/Expanded; without a
+// stable key Flutter disposes + rebuilds the subtree, and the Claude
+// conversation's SelectableRegion then runs a pending selection update
+// against now-inactive elements ("selectable not in this registrar" /
+// "renderObject of inactive element"). The GlobalKey makes Flutter MOVE the
+// element instead, preserving the selection subtree.
+final GlobalKey _kWorkspacePrimary = GlobalKey(debugLabel: 'workspace.primary');
+
+class _WorkspaceSlot extends StatelessWidget {
+  const _WorkspaceSlot({required this.tabs, required this.active});
+
+  final List<TabContribution> tabs;
+  final TabContribution active;
+
+  static const _editorTabId = 'editor.active';
+  static const _claudeTabId = 'claude.primary';
+
+  @override
+  Widget build(BuildContext context) {
+    final kernel = ClideKernel.of(context);
+    final tokens = ClideTheme.of(context).surface;
+    return ListenableBuilder(
+      listenable: kernel.arrangement,
+      builder: (ctx, _) {
+        final editorOpen = kernel.arrangement.editorOpen;
+        final editorTab = tabs.where((t) => t.id == _editorTabId).firstOrNull;
+
+        final claude = tabs.where((t) => t.id == _claudeTabId).firstOrNull;
+        final primaryPane = KeyedSubtree(key: _kWorkspacePrimary, child: (claude ?? active).build(ctx));
+
+        // A non-Claude, non-editor workspace tab being the active one (e.g.
+        // diff.view revealed by `clide ui open diff`, T-233) shows in the split
+        // region above Claude — "review alongside the conversation" — with a
+        // close affordance back to full-Claude. Only when Claude exists below
+        // it; with no Claude pane the active tab just takes the whole slot, as
+        // before. The editor keeps its own editorOpen-gated split.
+        final reveal = (claude != null && active.id != _claudeTabId && active.id != _editorTabId) ? active : null;
+        final topTab = reveal ?? (editorOpen ? editorTab : null);
+
+        if (topTab == null) {
+          return Container(color: tokens.panelBackground, child: primaryPane);
+        }
+
+        final ratio = kernel.arrangement.editorRatio;
+        return Container(
+          color: tokens.panelBackground,
+          child: LayoutBuilder(
+            builder: (ctx, constraints) {
+              final totalHeight = constraints.maxHeight;
+              final topHeight = (totalHeight * ratio).clamp(60.0, totalHeight - 60.0);
+              return Column(
+                children: [
+                  SizedBox(
+                    height: topHeight,
+                    child: reveal != null
+                        ? _RevealedTab(tab: reveal, onClose: () => kernel.panels.activateTab(Slots.workspace, _claudeTabId))
+                        : topTab.build(ctx),
+                  ),
+                  _EditorDragHandle(arrangement: kernel.arrangement, totalHeight: totalHeight),
+                  Expanded(child: primaryPane),
+                ],
+              );
+            },
+          ),
+        );
+      },
+    );
+  }
+}
+
+/// A non-Claude workspace tab revealed in the split region above Claude
+/// (T-233): a thin chrome header (title + close) over the tab's body, so the
+/// user can review it alongside the conversation and dismiss it back to
+/// full-Claude. The editor uses its own split path and never renders here.
+class _RevealedTab extends StatelessWidget {
+  const _RevealedTab({required this.tab, required this.onClose});
+
+  final TabContribution tab;
+  final VoidCallback onClose;
+
+  @override
+  Widget build(BuildContext context) {
+    final tokens = ClideTheme.of(context).surface;
+    return Column(
+      children: [
+        Container(
+          height: 28,
+          padding: const EdgeInsets.only(left: 10, right: 4),
+          color: tokens.panelHeader,
+          child: Row(
+            children: [
+              Expanded(
+                child: ClideText(resolveTabTitle(context, tab), fontSize: clideFontCaption, color: tokens.panelHeaderForeground, maxLines: 1),
+              ),
+              Semantics(
+                button: true,
+                label: 'Close',
+                excludeSemantics: true,
+                onTap: onClose,
+                child: ClideTappable(
+                  onTap: onClose,
+                  tooltip: 'Close',
+                  builder: (_, hovered, _) => Padding(
+                    padding: const EdgeInsets.all(6),
+                    child: ClideIcon(PhosphorIcons.byName('x'), size: 12, color: hovered ? tokens.globalForeground : tokens.globalTextMuted),
+                  ),
+                ),
+              ),
+            ],
+          ),
+        ),
+        Expanded(child: tab.build(context)),
+      ],
+    );
+  }
+}
+
+class _EditorDragHandle extends StatefulWidget {
+  const _EditorDragHandle({required this.arrangement, required this.totalHeight});
+
+  final LayoutArrangement arrangement;
+  final double totalHeight;
+
+  @override
+  State<_EditorDragHandle> createState() => _EditorDragHandleState();
+}
+
+class _EditorDragHandleState extends State<_EditorDragHandle> {
+  bool _hovered = false;
+  bool _focused = false;
+  double? _dragStartRatio;
+  double? _dragStartY;
+
+  // Editor split is a 0..1 fraction; the kernel clamps to 0.15..0.70.
+  // 2% per fine step, 10% per Shift step keeps keyboard feel close to
+  // the pixel-based DragResizeHandle.
+  static const double _stepFine = 0.02;
+  static const double _stepCoarse = 0.10;
+
+  @override
+  Widget build(BuildContext context) {
+    final tokens = ClideTheme.of(context).surface;
+    final lineColor = (_hovered || _focused) ? tokens.panelActiveBorder : tokens.panelBorder;
+
+    final ratio = widget.arrangement.editorRatio;
+    String pct(double r) => '${(r.clamp(0.15, 0.70) * 100).round()}%';
+    return Semantics(
+      container: true,
+      slider: true,
+      label: 'Editor split',
+      value: pct(ratio),
+      // increase/decrease actions require matching increased/decreased
+      // values, or Flutter asserts on every semantics flush.
+      increasedValue: pct(ratio + _stepFine),
+      decreasedValue: pct(ratio - _stepFine),
+      onIncrease: () => _bump(_stepFine),
+      onDecrease: () => _bump(-_stepFine),
+      child: FocusableActionDetector(
+        onShowFocusHighlight: (v) => setState(() => _focused = v),
+        shortcuts: const <ShortcutActivator, Intent>{
+          SingleActivator(LogicalKeyboardKey.arrowUp): _EditorBumpIntent(-_stepFine),
+          SingleActivator(LogicalKeyboardKey.arrowDown): _EditorBumpIntent(_stepFine),
+          SingleActivator(LogicalKeyboardKey.arrowUp, shift: true): _EditorBumpIntent(-_stepCoarse),
+          SingleActivator(LogicalKeyboardKey.arrowDown, shift: true): _EditorBumpIntent(_stepCoarse),
+        },
+        actions: <Type, Action<Intent>>{
+          _EditorBumpIntent: CallbackAction<_EditorBumpIntent>(
+            onInvoke: (intent) {
+              _bump(intent.delta);
+              return null;
+            },
+          ),
+        },
+        child: MouseRegion(
+          cursor: SystemMouseCursors.resizeRow,
+          onEnter: (_) => setState(() => _hovered = true),
+          onExit: (_) => setState(() => _hovered = false),
+          child: Listener(
+            onPointerDown: (e) {
+              _dragStartRatio = widget.arrangement.editorRatio;
+              _dragStartY = e.position.dy;
+            },
+            onPointerMove: (e) {
+              final startR = _dragStartRatio;
+              final startY = _dragStartY;
+              if (startR == null || startY == null || widget.totalHeight <= 0) return;
+              final deltaRatio = (e.position.dy - startY) / widget.totalHeight;
+              widget.arrangement.setEditorRatio(startR + deltaRatio);
+            },
+            onPointerUp: (_) {
+              _dragStartRatio = null;
+              _dragStartY = null;
+            },
+            child: Container(height: 4, color: lineColor),
+          ),
+        ),
+      ),
+    );
+  }
+
+  void _bump(double delta) {
+    widget.arrangement.setEditorRatio(widget.arrangement.editorRatio + delta);
+  }
+}
+
+class _EditorBumpIntent extends Intent {
+  const _EditorBumpIntent(this.delta);
+  final double delta;
+}
+
+class _ContextSlot extends StatelessWidget {
+  const _ContextSlot({required this.tabs, required this.active, required this.activeId, required this.onSelect});
+
+  final List<TabContribution> tabs;
+  final TabContribution active;
+  final String activeId;
+  final ValueChanged<String> onSelect;
+
+  @override
+  Widget build(BuildContext context) {
+    final tokens = ClideTheme.of(context).surface;
+    return Container(color: tokens.panelBackground, alignment: Alignment.topLeft, padding: const EdgeInsets.only(right: 2), child: active.build(context));
+  }
+}
+
+/// Resolve a tab's display title through i18n when it carries a key +
+/// namespace, else its static title. Shared by the slot bodies, the
+/// revealed-tab header, and the bottom icon rails.
+String resolveTabTitle(BuildContext context, TabContribution t) {
+  final key = t.titleKey;
+  final ns = t.i18nNamespace;
+  if (key == null || ns == null) return t.title;
+  return ClideKernel.of(context).i18n.string(key, namespace: ns, placeholder: t.title);
+}