diff --git a/test/builtin/editor/editor_controller_test.dart b/test/builtin/editor/editor_controller_test.dart
index c4a6cf63..ecfaddfe 100644
--- a/test/builtin/editor/editor_controller_test.dart
+++ b/test/builtin/editor/editor_controller_test.dart
@@ -200,26 +200,53 @@ void main() {
       expect(c.dirty, isFalse);
     });
 
-    test('editor.edited marks the buffer dirty', () async {
+    test('editor.edited marks the right buffer dirty, leaving siblings alone', () async {
       ipc.stub(
           'editor.list',
           (_) async => _ok({
-                'buffers': [_buf('b_1', 'a.dart')]
+                'buffers': [_buf('b_1', 'a.dart'), _buf('b_2', 'b.dart')]
               }));
       ipc.stub(
           'editor.active',
           (_) async => _ok({
                 'active': {'id': 'b_1'}
               }));
-      ipc.stub('editor.read', (_) async => _ok(_read('b_1', 'a.dart', 'x')));
+      ipc.stub('editor.read', (a) async => _ok(_read(a['id'] as String, 'a.dart', 'x')));
       await c.hydrate();
-      expect(c.buffers.single.dirty, isFalse);
+      expect(c.buffers.every((b) => !b.dirty), isTrue);
 
-      // A remote edit (not our own — no set-content was issued).
-      emitEditor(bus, 'editor.edited', {'id': 'b_1'});
+      // A remote edit of b_2 (not our own). b_1 stays clean — exercises
+      // the untouched-sibling branch of the dirty marker.
+      emitEditor(bus, 'editor.edited', {'id': 'b_2'});
       await pumpEventQueue();
 
-      expect(c.buffers.single.dirty, isTrue);
+      expect(c.buffers.firstWhere((b) => b.id == 'b_2').dirty, isTrue);
+      expect(c.buffers.firstWhere((b) => b.id == 'b_1').dirty, isFalse);
+    });
+
+    test('editor.active-changed to a different buffer loads its content', () async {
+      ipc.stub(
+          'editor.list',
+          (_) async => _ok({
+                'buffers': [_buf('b_1', 'a.dart'), _buf('b_2', 'b.dart')]
+              }));
+      ipc.stub(
+          'editor.active',
+          (_) async => _ok({
+                'active': {'id': 'b_1'}
+              }));
+      ipc.stub('editor.read', (a) async {
+        final id = a['id'] as String;
+        return _ok(_read(id, id == 'b_1' ? 'a.dart' : 'b.dart', 'body-$id'));
+      });
+      await c.hydrate();
+      expect(c.activeId, 'b_1');
+
+      emitEditor(bus, 'editor.active-changed', {'id': 'b_2'});
+      await pumpEventQueue();
+
+      expect(c.activeId, 'b_2');
+      expect(c.content, 'body-b_2');
     });
   });
 
@@ -251,5 +278,155 @@ void main() {
       expect(setArgs?['id'], 'b_1');
       expect(setArgs?['text'], 'xy');
     });
+
+    test('save() issues editor.save for the active buffer', () async {
+      ipc.stub(
+          'editor.list',
+          (_) async => _ok({
+                'buffers': [_buf('b_1', 'a.dart')]
+              }));
+      ipc.stub(
+          'editor.active',
+          (_) async => _ok({
+                'active': {'id': 'b_1'}
+              }));
+      ipc.stub('editor.read', (_) async => _ok(_read('b_1', 'a.dart', 'x')));
+      await c.hydrate();
+
+      String? saved;
+      ipc.stub('editor.save', (a) async {
+        saved = a['id'] as String?;
+        return _ok(const {});
+      });
+      await c.save();
+      expect(saved, 'b_1');
+    });
+
+    test('save() is a no-op with no active buffer', () async {
+      var calls = 0;
+      ipc.stub('editor.save', (_) async {
+        calls++;
+        return _ok(const {});
+      });
+      await c.save(); // never hydrated → no active
+      expect(calls, 0);
+    });
+  });
+
+  group('edge cases', () {
+    test('editor.active-changed to null clears the active buffer', () async {
+      ipc.stub(
+          'editor.list',
+          (_) async => _ok({
+                'buffers': [_buf('b_1', 'a.dart')]
+              }));
+      ipc.stub(
+          'editor.active',
+          (_) async => _ok({
+                'active': {'id': 'b_1'}
+              }));
+      ipc.stub('editor.read', (_) async => _ok(_read('b_1', 'a.dart', 'x')));
+      await c.hydrate();
+      expect(c.activeId, 'b_1');
+
+      emitEditor(bus, 'editor.active-changed', const {}); // no id
+      await pumpEventQueue();
+      expect(c.activeId, isNull);
+      expect(c.content, '');
+    });
+
+    test('hydrate surfaces an error when editor.active fails', () async {
+      ipc.stub('editor.list', (_) async => _ok({'buffers': const []}));
+      ipc.stub(
+        'editor.active',
+        (_) async => IpcResponse.err(
+          id: '',
+          error: IpcError(code: IpcExitCode.toolError, kind: IpcErrorKind.toolError, message: 'boom'),
+        ),
+      );
+      await c.hydrate();
+      expect(c.error, 'boom');
+    });
+
+    test('a missing-stub editor.list (not ok) leaves the buffer list empty', () async {
+      // No editor.list stub registered → FakeDaemonClient returns a
+      // notFound error; _refreshList bails without crashing.
+      ipc.stub('editor.active', (_) async => _ok(const {}));
+      await c.hydrate();
+      expect(c.buffers, isEmpty);
+    });
+
+    test('editor.opened with no id clears the active buffer', () async {
+      ipc.stub(
+          'editor.list',
+          (_) async => _ok({
+                'buffers': [_buf('b_1', 'a.dart')]
+              }));
+      ipc.stub(
+          'editor.active',
+          (_) async => _ok({
+                'active': {'id': 'b_1'}
+              }));
+      ipc.stub('editor.read', (_) async => _ok(_read('b_1', 'a.dart', 'x')));
+      await c.hydrate();
+      expect(c.activeId, 'b_1');
+
+      emitEditor(bus, 'editor.opened', const {}); // no id
+      await pumpEventQueue();
+      expect(c.activeId, isNull);
+    });
+
+    test('a failing editor.read surfaces the error', () async {
+      ipc.stub(
+          'editor.list',
+          (_) async => _ok({
+                'buffers': [_buf('b_1', 'a.dart')]
+              }));
+      ipc.stub(
+          'editor.active',
+          (_) async => _ok({
+                'active': {'id': 'b_1'}
+              }));
+      ipc.stub(
+        'editor.read',
+        (_) async => IpcResponse.err(
+          id: '',
+          error: IpcError(code: IpcExitCode.toolError, kind: IpcErrorKind.toolError, message: 'read failed'),
+        ),
+      );
+      await c.hydrate();
+      expect(c.error, 'read failed');
+    });
+
+    test('our own edit echo (editor.edited) is suppressed once, not reloaded', () async {
+      ipc.stub(
+          'editor.list',
+          (_) async => _ok({
+                'buffers': [_buf('b_1', 'a.dart')]
+              }));
+      ipc.stub(
+          'editor.active',
+          (_) async => _ok({
+                'active': {'id': 'b_1'}
+              }));
+      ipc.stub('editor.read', (_) async => _ok(_read('b_1', 'a.dart', 'original')));
+      ipc.stub('editor.set-content', (_) async => _ok(const {}));
+      await c.hydrate();
+
+      // Local edit arms _suppressNextRemoteEdit.
+      c.pushLocalEdit(newContent: 'local', newSelection: const Selection.collapsed(5));
+      var reads = 0;
+      ipc.stub('editor.read', (_) async {
+        reads++;
+        return _ok(_read('b_1', 'a.dart', 'reloaded'));
+      });
+      // The echo of our own set-content comes back as editor.edited.
+      emitEditor(bus, 'editor.edited', {'id': 'b_1'});
+      await pumpEventQueue();
+
+      // Suppressed: no reload, local content preserved.
+      expect(reads, 0);
+      expect(c.content, 'local');
+    });
   });
 }
diff --git a/test/builtin/editor/editor_view_test.dart b/test/builtin/editor/editor_view_test.dart
index b8941064..cecf6ac7 100644
--- a/test/builtin/editor/editor_view_test.dart
+++ b/test/builtin/editor/editor_view_test.dart
@@ -6,11 +6,16 @@ library;
 
 import 'package:clide/builtin/editor/src/editor_view.dart';
 import 'package:clide/clide.dart';
+import 'package:clide/widgets/widgets.dart';
+import 'package:flutter/services.dart';
+import 'package:flutter/widgets.dart';
 import 'package:flutter_test/flutter_test.dart';
 
 import '../../helpers/kernel_fixture.dart';
 import '../../helpers/widget_harness.dart';
 
+Finder _closeIcons() => find.byWidgetPredicate((w) => w is ClideIcon && w.painter is CloseIcon);
+
 IpcResponse _ok(Map<String, Object?> data) => IpcResponse.ok(id: '', data: data);
 
 Map<String, Object?> _buf(String id, String path, {bool dirty = false}) => {'id': id, 'path': path, 'dirty': dirty};
@@ -82,5 +87,59 @@ void main() {
 
       expect(activated, 'b_2');
     });
+
+    testWidgets('closing a tab routes to editor.close', (tester) async {
+      stubBuffers([_buf('b_1', 'lib/a.dart')], active: 'b_1');
+      String? closed;
+      f.ipc.stub('editor.close', (a) async {
+        closed = a['id'] as String?;
+        return _ok(const {});
+      });
+      await tester.pumpWidget(harness(f, const EditorView()));
+      await tester.pumpAndSettle();
+
+      expect(_closeIcons(), findsWidgets);
+      await tester.tap(_closeIcons().first);
+      await tester.pumpAndSettle();
+
+      expect(closed, 'b_1');
+    });
+
+    testWidgets('typing in the editor mirrors to editor.set-content', (tester) async {
+      stubBuffers([_buf('b_1', 'lib/a.dart')], active: 'b_1');
+      Map<String, Object?>? setArgs;
+      f.ipc.stub('editor.set-content', (a) async {
+        setArgs = a;
+        return _ok(const {});
+      });
+      await tester.pumpWidget(harness(f, const EditorView()));
+      await tester.pumpAndSettle();
+
+      await tester.enterText(find.byType(EditableText), 'edited body');
+      await tester.pumpAndSettle();
+
+      expect(setArgs?['id'], 'b_1');
+      expect(setArgs?['text'], 'edited body');
+    });
+
+    testWidgets('Ctrl+S in the editor triggers editor.save', (tester) async {
+      stubBuffers([_buf('b_1', 'lib/a.dart')], active: 'b_1');
+      String? saved;
+      f.ipc.stub('editor.save', (a) async {
+        saved = a['id'] as String?;
+        return _ok(const {});
+      });
+      await tester.pumpWidget(harness(f, const EditorView()));
+      await tester.pumpAndSettle();
+
+      await tester.tap(find.byType(EditableText));
+      await tester.pump();
+      await tester.sendKeyDownEvent(LogicalKeyboardKey.controlLeft);
+      await tester.sendKeyEvent(LogicalKeyboardKey.keyS);
+      await tester.sendKeyUpEvent(LogicalKeyboardKey.controlLeft);
+      await tester.pumpAndSettle();
+
+      expect(saved, 'b_1');
+    });
   });
 }
diff --git a/test/builtin/editor/syntax_text_controller_test.dart b/test/builtin/editor/syntax_text_controller_test.dart
new file mode 100644
index 00000000..20901b09
--- /dev/null
+++ b/test/builtin/editor/syntax_text_controller_test.dart
@@ -0,0 +1,130 @@
+/// Tests SyntaxTextController — the editor's TextEditingController that
+/// turns tree-sitter spans into styled TextSpans. A fake
+/// TreeSitterService supplies canned spans so the byte→char mapping and
+/// span-rendering logic can be exercised without the native grammar.
+library;
+
+import 'package:clide/builtin/editor/src/syntax_text_controller.dart';
+import 'package:clide/kernel/kernel.dart';
+import 'package:clide/kernel/src/syntax/tree_sitter_service.dart';
+import 'package:flutter/widgets.dart';
+import 'package:flutter_test/flutter_test.dart';
+
+import '../../helpers/kernel_fixture.dart';
+import '../../helpers/widget_harness.dart';
+
+/// TreeSitterService stub returning canned spans (constructor does no
+/// FFI work — `_init` is lazy and never reached here).
+class _FakeSyntax extends TreeSitterService {
+  _FakeSyntax(this.spans);
+  final List<SyntaxSpan> spans;
+  @override
+  Future<SyntaxResult> highlight(String path, String source) async => SyntaxResult(spans);
+}
+
+/// Counts highlight invocations so a test can assert a same-path
+/// updatePath doesn't kick off a redundant highlight.
+class _CountingSyntax extends TreeSitterService {
+  int calls = 0;
+  @override
+  Future<SyntaxResult> highlight(String path, String source) async {
+    calls++;
+    return const SyntaxResult([]);
+  }
+}
+
+void main() {
+  group('SyntaxTextController', () {
+    late KernelFixture f;
+    setUp(() async => f = await KernelFixture.create());
+    tearDown(() => f.dispose());
+
+    /// Pump a themed context, run [body] with a controller already
+    /// given tokens from the active theme.
+    Future<void> withController(
+      WidgetTester tester,
+      SyntaxTextController c,
+      Future<void> Function(BuildContext ctx) body,
+    ) async {
+      late BuildContext ctx;
+      await tester.pumpWidget(harness(f, Builder(builder: (context) {
+        ctx = context;
+        return const SizedBox();
+      })));
+      c.tokens = ClideTheme.of(ctx).surface;
+      await body(ctx);
+    }
+
+    testWidgets('renders highlighted spans as styled TextSpan children', (tester) async {
+      final c = SyntaxTextController(
+          syntax: _FakeSyntax(const [
+        SyntaxSpan(start: 0, end: 5, role: 'keyword'), // "class"
+        SyntaxSpan(start: 6, end: 9, role: 'type'), // "Foo"
+      ]));
+      await withController(tester, c, (ctx) async {
+        c.text = 'class Foo {}';
+        c.updatePath('a.dart');
+        await tester.pumpAndSettle();
+        final span = c.buildTextSpan(context: ctx, withComposing: false);
+        expect(span.children, isNotNull);
+        // keyword + gap + type + trailing → several children.
+        expect(span.children!.length, greaterThan(2));
+      });
+    });
+
+    testWidgets('maps byte offsets across multi-byte (surrogate) characters', (tester) async {
+      // '😀' is a surrogate pair (4 UTF-8 bytes). A span after it must
+      // still land on the right character offset.
+      final c = SyntaxTextController(
+          syntax: _FakeSyntax(const [
+        SyntaxSpan(start: 5, end: 8, role: 'type'), // "Foo" after "😀 "
+      ]));
+      await withController(tester, c, (ctx) async {
+        c.text = '😀 Foo';
+        c.updatePath('a.dart');
+        await tester.pumpAndSettle();
+        final span = c.buildTextSpan(context: ctx, withComposing: false);
+        expect(span.children, isNotNull);
+        expect(span.toPlainText(), '😀 Foo');
+      });
+    });
+
+    testWidgets('with no spans falls back to a plain TextSpan', (tester) async {
+      final c = SyntaxTextController(syntax: _FakeSyntax(const []));
+      await withController(tester, c, (ctx) async {
+        c.text = 'plain text';
+        final span = c.buildTextSpan(context: ctx, withComposing: false);
+        expect(span.children, isNull);
+        expect(span.text, 'plain text');
+      });
+    });
+
+    testWidgets('updatePath to the same path is a no-op', (tester) async {
+      final syntax = _CountingSyntax();
+      final c = SyntaxTextController(syntax: syntax);
+      await withController(tester, c, (ctx) async {
+        c.text = 'x';
+        c.updatePath('a.dart');
+        await tester.pumpAndSettle();
+        final first = syntax.calls;
+        expect(first, greaterThan(0));
+        c.updatePath('a.dart'); // same path → early return
+        await tester.pumpAndSettle();
+        expect(syntax.calls, first); // no new highlight request
+      });
+    });
+
+    testWidgets('a path with no known grammar skips highlighting', (tester) async {
+      final c = SyntaxTextController(syntax: _FakeSyntax(const [SyntaxSpan(start: 0, end: 1, role: 'x')]));
+      await withController(tester, c, (ctx) async {
+        c.text = 'data';
+        c.updatePath('notes.unknownext');
+        await tester.pumpAndSettle();
+        final span = c.buildTextSpan(context: ctx, withComposing: false);
+        // No grammar → no spans applied → plain text.
+        expect(span.children, isNull);
+        expect(span.text, 'data');
+      });
+    });
+  });
+}