wire builtin.editor to the active buffer + open files from the tree

EditorController mirrors the daemon's active buffer into the Flutter
UI. Hydrates on mount (editor.active → editor.read), subscribes to
editor.opened / active-changed / edited / saved / closed, and pushes
local edits back via editor.set-content. A one-shot echo-suppression
flag keeps the daemon's authoritative edit echo from clobbering the
caret the user just moved.

Text surface is EditableText directly — no TextField / Material
import, so D-007's "bare WidgetsApp" guardrail carries into the
editor tab. JetBrainsMono via the shared mono-family constants;
cursor + selection colours come from the theme tokens.

File-tree click now calls ipc.request('editor.open', {path}) instead
of the kernel command registry (which wouldn't have reached the
daemon). The opened file becomes active, the editor tab's controller
sees editor.active-changed, and the text content reconciles.

Linux release bundle still builds; 174 app tests + 74 core tests
stay green.

Co-Authored-By: Claude <noreply@anthropic.com>

CHANGELOG.md

@@ -18,6 +18,24 @@ heading, and (b) bumping `project.yaml` `version:` in the same commit.
 
 ### Added
 
+- `builtin.editor` — Tier-2 editor tab wired up. Contributes a
+  single `Editor` workspace tab that renders the daemon's active
+  buffer via a new `EditorController`. Hydrates on mount
+  (`editor.active` → `editor.read`), subscribes to
+  `editor.opened | active-changed | edited | saved | closed`, and
+  propagates user edits back through `editor.set-content`. Small
+  echo-suppression guard avoids clobbering the caret when the
+  daemon's authoritative edit echo comes back. Text surface is
+  Flutter's `EditableText` primitive — no `TextField` / Material —
+  so the D-007 "no Material root" stance carries into the editor;
+  JetBrainsMono via the shared `clideMonoFamily` constants, cursor
+  + selection colours bind to the theme.
+
+- File-tree click in `builtin.files` now opens the clicked file in
+  the editor via `ipc.request('editor.open', {path})`. No local
+  command hop — the dispatch goes straight to the daemon and the
+  UI reconciles through the `editor.active-changed` event.
+
 - CLI shortcuts per CLAUDE.md's Tier-2 list: `clide open <path>`,
   `clide active`, `clide insert <text | ->`, `clide replace-selection
   <text | ->`, `clide save`, `clide tail --events [--filter

app/lib/builtin/editor/src/editor_controller.dart

@@ -0,0 +1,171 @@
+/// Flutter-side mirror of the daemon's active-editor state.
+///
+/// Listens to `editor.*` events over IPC and tracks: the active
+/// buffer's id/path/content/selection, and whether the buffer is
+/// dirty. The widget layer consumes this via [ListenableBuilder].
+///
+/// User edits flow the other way — the widget calls into the
+/// controller, which calls `editor.set-content` / `editor.save` on
+/// the daemon. The daemon is the source of truth; the widget is a
+/// reconciled view.
+library;
+
+import 'dart:async';
+
+import 'package:clide/clide.dart';
+import 'package:clide_app/kernel/kernel.dart';
+import 'package:flutter/foundation.dart';
+
+class EditorController extends ChangeNotifier {
+  EditorController({required this.ipc, required EventBus events})
+      : _events = events {
+    _eventSub = events.on<DaemonEvent>().listen(_onEvent);
+  }
+
+  final DaemonClient ipc;
+  // ignore: unused_field  — kept for future subscription changes
+  final EventBus _events;
+
+  StreamSubscription<DaemonEvent>? _eventSub;
+
+  String? _activeId;
+  String? _activePath;
+  String _content = '';
+  Selection _selection = const Selection.collapsed(0);
+  bool _dirty = false;
+  String? _error;
+
+  bool _suppressNextRemoteEdit = false;
+  int _pendingLocalEdits = 0;
+
+  String? get activeId => _activeId;
+  String? get activePath => _activePath;
+  String get content => _content;
+  Selection get selection => _selection;
+  bool get dirty => _dirty;
+  String? get error => _error;
+
+  /// On first mount we don't know what (if anything) is already
+  /// active. Ask the daemon.
+  Future<void> hydrate() async {
+    final r = await ipc.request('editor.active');
+    if (!r.ok) {
+      _error = r.error?.message;
+      notifyListeners();
+      return;
+    }
+    final active = r.data['active'];
+    if (active is! Map) {
+      _activeId = null;
+      _activePath = null;
+      _content = '';
+      notifyListeners();
+      return;
+    }
+    final id = active['id']! as String;
+    await _loadBuffer(id);
+  }
+
+  Future<void> _loadBuffer(String id) async {
+    final r = await ipc.request('editor.read', args: {'id': id});
+    if (!r.ok) {
+      _error = r.error?.message;
+      notifyListeners();
+      return;
+    }
+    _activeId = r.data['id']! as String;
+    _activePath = r.data['path']! as String;
+    _content = (r.data['content'] as String?) ?? '';
+    final sel = r.data['selection'];
+    _selection = sel is Map
+        ? Selection.fromJson(sel.cast<String, Object?>())
+        : const Selection.collapsed(0);
+    _dirty = (r.data['dirty'] as bool?) ?? false;
+    _error = null;
+    notifyListeners();
+  }
+
+  /// Called by the widget on every local text edit.
+  void pushLocalEdit({
+    required String newContent,
+    required Selection newSelection,
+  }) {
+    final id = _activeId;
+    if (id == null) return;
+
+    _content = newContent;
+    _selection = newSelection;
+    _dirty = true;
+    notifyListeners();
+
+    // Mirror to daemon. Use editor.set-content for the first cut —
+    // it's coarse but simple and avoids diff computation. Future
+    // tuning: diff + editor.insert / editor.replace-selection for
+    // large buffers, so event broadcasts stay small.
+    _pendingLocalEdits++;
+    _suppressNextRemoteEdit = true;
+    ipc.request('editor.set-content', args: {
+      'id': id,
+      'text': newContent,
+      'selection': newSelection.toJson(),
+    }).whenComplete(() => _pendingLocalEdits--);
+  }
+
+  Future<void> save() async {
+    final id = _activeId;
+    if (id == null) return;
+    await ipc.request('editor.save', args: {'id': id});
+  }
+
+  void _onEvent(DaemonEvent e) {
+    if (e.subsystem != 'editor') return;
+    switch (e.kind) {
+      case 'editor.opened':
+      case 'editor.active-changed':
+        final id = e.data['id'] as String?;
+        if (id == null) {
+          _activeId = null;
+          _activePath = null;
+          _content = '';
+          _selection = const Selection.collapsed(0);
+          _dirty = false;
+          notifyListeners();
+        } else if (id != _activeId) {
+          _loadBuffer(id);
+        }
+      case 'editor.edited':
+        // Our own set-content echoes back as editor.edited. Skip one
+        // bounce so we don't clobber the caret the user just moved.
+        if (_suppressNextRemoteEdit) {
+          _suppressNextRemoteEdit = false;
+          return;
+        }
+        // Remote edit (another client, or the CLI inserting bytes).
+        // Reload the authoritative buffer.
+        final id = e.data['id'] as String?;
+        if (id != null && id == _activeId && _pendingLocalEdits == 0) {
+          _loadBuffer(id);
+        }
+      case 'editor.saved':
+        if (e.data['id'] == _activeId) {
+          _dirty = false;
+          notifyListeners();
+        }
+      case 'editor.closed':
+        if (e.data['id'] == _activeId) {
+          _activeId = null;
+          _activePath = null;
+          _content = '';
+          _dirty = false;
+          notifyListeners();
+        }
+    }
+  }
+
+  @override
+  void dispose() {
+    _eventSub?.cancel();
+    _eventSub = null;
+    super.dispose();
+  }
+}

app/lib/builtin/editor/src/editor_view.dart

@@ -0,0 +1,198 @@
+import 'dart:async';
+
+import 'package:clide/clide.dart';
+import 'package:clide_app/kernel/kernel.dart';
+import 'package:clide_app/widgets/widgets.dart';
+import 'package:flutter/services.dart';
+import 'package:flutter/widgets.dart';
+
+import 'editor_controller.dart';
+
+/// Tier-2 editor tab. One tab — the content reflects the daemon's
+/// active buffer. Multi-file tabs live in the workspace-slot plan but
+/// aren't in Tier 2's scope; opening a new file swaps this view's
+/// content.
+///
+/// Uses Flutter's low-level `EditableText` so we stay off Material
+/// per D-007. Owning more of the editor stack (line numbers, gutter,
+/// syntax highlighting) lands in later tiers; Tier 2 is plain text.
+class EditorView extends StatefulWidget {
+  const EditorView({super.key});
+
+  @override
+  State<EditorView> createState() => _EditorViewState();
+}
+
+class _EditorViewState extends State<EditorView> {
+  EditorController? _controller;
+  late final TextEditingController _text;
+  late final FocusNode _focus;
+  String? _lastRemoteContent;
+
+  @override
+  void initState() {
+    super.initState();
+    _text = TextEditingController();
+    _focus = FocusNode();
+    _text.addListener(_onTextChanged);
+  }
+
+  @override
+  void didChangeDependencies() {
+    super.didChangeDependencies();
+    if (_controller != null) return;
+    final kernel = ClideKernel.of(context);
+    _controller = EditorController(ipc: kernel.ipc, events: kernel.events)
+      ..addListener(_onControllerChanged);
+    unawaited(_controller!.hydrate());
+  }
+
+  @override
+  void dispose() {
+    _text.removeListener(_onTextChanged);
+    _text.dispose();
+    _focus.dispose();
+    _controller?.removeListener(_onControllerChanged);
+    _controller?.dispose();
+    super.dispose();
+  }
+
+  void _onControllerChanged() {
+    final c = _controller!;
+    if (c.content != _lastRemoteContent) {
+      _lastRemoteContent = c.content;
+      final sel = TextSelection(
+        baseOffset: c.selection.start.clamp(0, c.content.length),
+        extentOffset: c.selection.end.clamp(0, c.content.length),
+      );
+      _text.removeListener(_onTextChanged);
+      _text.value = TextEditingValue(text: c.content, selection: sel);
+      _text.addListener(_onTextChanged);
+    }
+    setState(() {}); // subtitle refresh
+  }
+
+  void _onTextChanged() {
+    final c = _controller;
+    if (c == null || c.activeId == null) return;
+    final value = _text.value;
+    if (value.text == c.content &&
+        value.selection.baseOffset == c.selection.start &&
+        value.selection.extentOffset == c.selection.end) {
+      return;
+    }
+    _lastRemoteContent = value.text;
+    c.pushLocalEdit(
+      newContent: value.text,
+      newSelection: Selection(
+        start: value.selection.start < 0
+            ? value.text.length
+            : value.selection.start,
+        end: value.selection.end < 0
+            ? value.text.length
+            : value.selection.end,
+      ),
+    );
+  }
+
+  KeyEventResult _onKey(FocusNode node, KeyEvent event) {
+    if (event is! KeyDownEvent) return KeyEventResult.ignored;
+    final isCmd = HardwareKeyboard.instance.isMetaPressed ||
+        HardwareKeyboard.instance.isControlPressed;
+    if (isCmd && event.logicalKey == LogicalKeyboardKey.keyS) {
+      unawaited(_controller?.save());
+      return KeyEventResult.handled;
+    }
+    return KeyEventResult.ignored;
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    final c = _controller;
+    final tokens = ClideTheme.of(context).surface;
+    if (c == null) return const SizedBox.shrink();
+
+    return ListenableBuilder(
+      listenable: c,
+      builder: (context, _) {
+        final title = c.activePath ?? 'editor';
+        final subtitle = c.activeId == null
+            ? 'no buffer · use `clide open <path>` or pick a file in the tree'
+            : '${c.activeId} · ${c.dirty ? 'modified' : 'saved'}'
+                '${c.error == null ? '' : ' · ${c.error}'}';
+
+        return ClidePaneChrome(
+          title: title,
+          subtitle: subtitle,
+          child: c.activeId == null
+              ? const Center(
+                  child: ClideText(
+                    'Open a file to begin editing.',
+                    muted: true,
+                    fontSize: 13,
+                  ),
+                )
+              : Focus(
+                  onKeyEvent: _onKey,
+                  child: _TextBody(
+                    controller: _text,
+                    focus: _focus,
+                    background: tokens.panelBackground,
+                    foreground: tokens.globalForeground,
+                    accent: tokens.globalFocus,
+                  ),
+                ),
+        );
+      },
+    );
+  }
+}
+
+class _TextBody extends StatelessWidget {
+  const _TextBody({
+    required this.controller,
+    required this.focus,
+    required this.background,
+    required this.foreground,
+    required this.accent,
+  });
+
+  final TextEditingController controller;
+  final FocusNode focus;
+  final Color background;
+  final Color foreground;
+  final Color accent;
+
+  @override
+  Widget build(BuildContext context) {
+    return Semantics(
+      label: 'editor text area',
+      textField: true,
+      multiline: true,
+      child: ColoredBox(
+        color: background,
+        child: Padding(
+          padding: const EdgeInsets.all(8),
+          child: EditableText(
+            controller: controller,
+            focusNode: focus,
+            style: TextStyle(
+              color: foreground,
+              fontSize: 13,
+              fontFamily: clideMonoFamily,
+              fontFamilyFallback: clideMonoFamilyFallback,
+            ),
+            cursorColor: foreground,
+            backgroundCursorColor: foreground.withAlpha(0x44),
+            selectionColor: accent.withAlpha(0x55),
+            maxLines: null,
+            expands: true,
+            keyboardType: TextInputType.multiline,
+            textAlign: TextAlign.start,
+            showCursor: true,
+          ),
+        ),
+      ),
+    );
+  }
+}

app/lib/builtin/editor/src/extension.dart

@@ -1,17 +1,30 @@
+import 'package:clide_app/builtin/editor/src/editor_view.dart';
 import 'package:clide_app/extension/extension.dart';
+import 'package:clide_app/kernel/kernel.dart';
 
-/// Tier-0 stub. Real implementation lands in a later tier; the extension
-/// is registered so the extensions-ui surface can list it as "installed,
-/// not yet implemented" and its id is reserved.
+/// Tier-2 editor pane. Contributes a single workspace tab that
+/// renders the daemon's active buffer. Multi-file tabs live in the
+/// follow-up plan; today the pane is one-at-a-time.
 class EditorExtension extends ClideExtension {
   @override
   String get id => 'builtin.editor';
   @override
   String get title => 'Editor';
   @override
-  String get version => '0.0.0-stub';
+  String get version => '0.1.0';
   @override
   List<String> get dependsOn => const [];
+
   @override
-  List<ContributionPoint> get contributions => const [];
+  List<ContributionPoint> get contributions => [
+        TabContribution(
+          id: 'editor.active',
+          slot: Slots.workspace,
+          title: 'Editor',
+          titleKey: 'tab.title',
+          i18nNamespace: id,
+          priority: 80, // between Claude (90) and welcome (-100)
+          build: (_) => const EditorView(),
+        ),
+      ];
 }

app/lib/builtin/files/src/file_tree_view.dart

@@ -197,11 +197,14 @@ class _FileRow extends StatelessWidget {
 
   void _openFile(BuildContext context, String path) {
     final kernel = ClideKernel.of(context);
-    // editor.open is a Tier-2 command; the registry's contract takes
-    // a positional argv, so pass the path as argv[0]. Response is
-    // ignored — until the editor extension registers the handler,
-    // execute() returns a not-found error.
-    unawaited(kernel.commands.execute('editor.open', args: [path]));
+    // editor.open is a daemon-side IPC handler (lib/src/daemon/
+    // editor_commands.dart), not a kernel command. Fire the request
+    // and let the editor extension's controller pick up the
+    // editor.active-changed / editor.opened event — no need to await
+    // or handle the response here.
+    unawaited(
+      kernel.ipc.request('editor.open', args: {'path': path}),
+    );
   }
 }
 

app/lib/kernel/src/i18n/catalog/builtin.editor_en_us.json

@@ -0,0 +1,5 @@
+{
+  "tab.title": { "translation": "Editor" },
+  "empty": { "translation": "Open a file to begin editing." },
+  "subtitle.no-buffer": { "translation": "no buffer · use `clide open <path>` or pick a file in the tree" }
+}

app/lib/main.dart

@@ -125,4 +125,5 @@ const List<String> _tier0Namespaces = [
   'builtin.terminal',
   'builtin.files',
   'builtin.claude',
+  'builtin.editor',
 ];