test(coverage): lift os/code-block/deeplink for gate headroom

The three worst-covered files were genuinely untested, not edge cases:
os.dart 27%→~85% (inject the process runner so openURL/reveal don't spawn a
real browser), clide_code_block 39%→~90% (expose the byte→char span mapper
as a top-level fn + render tests), deeplink 29%→~75% (the confirm-opens and
not-activated paths). Buys buffer above the 95% floor so a feature batch
doesn't immediately trip the gate. 95.01% → 95.22%.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

lib/kernel/src/os.dart

@@ -15,11 +15,16 @@ class OsLifecycleEvent extends ClideEvent {
   String get kind => _kind;
 }
 
+/// Runs an external command — injected so [OsBridge] is testable without
+/// spawning a real `xdg-open` / `open` / `explorer`.
+typedef OsProcessRunner = Future<ProcessResult> Function(String executable, List<String> arguments);
+
 class OsBridge {
-  OsBridge({required Logger log, required DaemonBus events}) : _log = log, _events = events;
+  OsBridge({required Logger log, required DaemonBus events, OsProcessRunner? run}) : _log = log, _events = events, _run = run ?? Process.run;
 
   final Logger _log;
   final DaemonBus _events;
+  final OsProcessRunner _run;
 
   Future<bool> openURL(String url) async {
     final cmd = _openCommand();
@@ -28,7 +33,7 @@ class OsBridge {
       return false;
     }
     try {
-      final r = await Process.run(cmd[0], [...cmd.skip(1), url]);
+      final r = await _run(cmd[0], [...cmd.skip(1), url]);
       return r.exitCode == 0;
     } catch (e) {
       _log.warn('os', 'openURL failed', error: e);
@@ -40,7 +45,7 @@ class OsBridge {
     final cmd = _revealCommand(path);
     if (cmd == null) return false;
     try {
-      final r = await Process.run(cmd[0], cmd.skip(1).toList());
+      final r = await _run(cmd[0], cmd.skip(1).toList());
       return r.exitCode == 0;
     } catch (e) {
       _log.warn('os', 'reveal failed', error: e);

lib/widgets/src/clide_code_block.dart

@@ -64,7 +64,7 @@ class _ClideCodeBlockState extends State<ClideCodeBlock> {
     if (spans == null || spans.isEmpty) {
       textSpan = TextSpan(text: widget.source, style: style);
     } else {
-      textSpan = _buildHighlightedSpan(widget.source, spans, style, tokens);
+      textSpan = buildHighlightedSpan(widget.source, spans, style, tokens);
     }
 
     return Container(
@@ -78,53 +78,57 @@ class _ClideCodeBlockState extends State<ClideCodeBlock> {
       child: SingleChildScrollView(scrollDirection: Axis.horizontal, child: Text.rich(textSpan)),
     );
   }
+}
 
-  static TextSpan _buildHighlightedSpan(String source, List<SyntaxSpan> spans, TextStyle base, dynamic tokens) {
-    final bytes = utf8.encode(source);
-    final byteToChar = List<int>.filled(bytes.length + 1, source.length);
-    var bi = 0;
-    for (var ci = 0; ci < source.length; ci++) {
-      byteToChar[bi] = ci;
-      final rune = source.codeUnitAt(ci);
-      if (rune < 0x80) {
-        bi += 1;
-      } else if (rune < 0x800) {
-        bi += 2;
-      } else if (rune >= 0xD800 && rune <= 0xDBFF) {
-        bi += 4;
-        ci++;
-      } else {
-        bi += 3;
-      }
+/// Maps tree-sitter byte-offset [spans] onto character ranges of [source]
+/// (handling multi-byte UTF-8 + surrogate pairs) and colours each run. Exposed
+/// so the byte→char mapping and span clipping are unit-tested directly.
+@visibleForTesting
+TextSpan buildHighlightedSpan(String source, List<SyntaxSpan> spans, TextStyle base, dynamic tokens) {
+  final bytes = utf8.encode(source);
+  final byteToChar = List<int>.filled(bytes.length + 1, source.length);
+  var bi = 0;
+  for (var ci = 0; ci < source.length; ci++) {
+    byteToChar[bi] = ci;
+    final rune = source.codeUnitAt(ci);
+    if (rune < 0x80) {
+      bi += 1;
+    } else if (rune < 0x800) {
+      bi += 2;
+    } else if (rune >= 0xD800 && rune <= 0xDBFF) {
+      bi += 4;
+      ci++;
+    } else {
+      bi += 3;
     }
-    byteToChar[bi] = source.length;
+  }
+  byteToChar[bi] = source.length;
 
-    final sorted = List.of(spans)..sort((a, b) => a.start.compareTo(b.start));
-    final children = <TextSpan>[];
-    var lastChar = 0;
+  final sorted = List.of(spans)..sort((a, b) => a.start.compareTo(b.start));
+  final children = <TextSpan>[];
+  var lastChar = 0;
 
-    for (final span in sorted) {
-      final sChar = span.start < byteToChar.length ? byteToChar[span.start] : source.length;
-      final eChar = span.end < byteToChar.length ? byteToChar[span.end] : source.length;
-      final clippedStart = sChar < lastChar ? lastChar : sChar;
-      if (clippedStart > lastChar) {
-        children.add(TextSpan(text: source.substring(lastChar, clippedStart)));
-      }
-      if (eChar > clippedStart) {
-        final color = TreeSitterService.colorForRole(span.role, tokens);
-        children.add(
-          TextSpan(
-            text: source.substring(clippedStart, eChar),
-            style: base.copyWith(color: color),
-          ),
-        );
-      }
-      if (eChar > lastChar) lastChar = eChar;
+  for (final span in sorted) {
+    final sChar = span.start < byteToChar.length ? byteToChar[span.start] : source.length;
+    final eChar = span.end < byteToChar.length ? byteToChar[span.end] : source.length;
+    final clippedStart = sChar < lastChar ? lastChar : sChar;
+    if (clippedStart > lastChar) {
+      children.add(TextSpan(text: source.substring(lastChar, clippedStart)));
     }
-    if (lastChar < source.length) {
-      children.add(TextSpan(text: source.substring(lastChar)));
+    if (eChar > clippedStart) {
+      final color = TreeSitterService.colorForRole(span.role, tokens);
+      children.add(
+        TextSpan(
+          text: source.substring(clippedStart, eChar),
+          style: base.copyWith(color: color),
+        ),
+      );
     }
+    if (eChar > lastChar) lastChar = eChar;
+  }
+  if (lastChar < source.length) {
+    children.add(TextSpan(text: source.substring(lastChar)));
+  }
 
-    return TextSpan(style: base, children: children);
-  }
+  return TextSpan(style: base, children: children);
 }

test/builtin/deeplink/extension_test.dart

@@ -5,6 +5,7 @@ library;
 import 'dart:async';
 
 import 'package:clide/builtin/deeplink/deeplink.dart';
+import 'package:clide/extension/extension.dart' show CommandContribution;
 import 'package:flutter/widgets.dart';
 import 'package:flutter_test/flutter_test.dart';
 
@@ -53,4 +54,25 @@ void main() {
     expect(f.services.dialog.isOpen, isFalse);
     expect(r.data['status'], 'rejected');
   });
+
+  testWidgets('confirming an allowlisted link opens the file (T-56)', (tester) async {
+    await tester.pumpWidget(harness(f, const SizedBox()));
+    await tester.pump();
+
+    final future = f.services.commands.execute('deeplink.invoke', args: ['clide://open?path=/x.dart&line=5']);
+    await tester.pump();
+    expect(f.services.dialog.isOpen, isTrue);
+    f.services.dialog.dismiss(true); // confirm → the handler runs editor.open
+    await tester.pumpAndSettle();
+
+    final r = await future;
+    expect(r.data['status'], 'opened');
+    expect(r.data['path'], '/x.dart');
+  });
+
+  test('reports not-activated when invoked before activation', () async {
+    final ext = DeepLinkExtension(); // never activated → no context
+    final run = (ext.contributions.single as CommandContribution).run;
+    expect((await run(['clide://open?path=/x'])).data['status'], 'not-activated');
+  });
 }

test/kernel/src/os_test.dart

@@ -0,0 +1,58 @@
+import 'dart:io';
+
+import 'package:clide/kernel/src/events/bus.dart';
+import 'package:clide/kernel/src/log.dart';
+import 'package:clide/kernel/src/os.dart';
+import 'package:flutter_test/flutter_test.dart';
+
+void main() {
+  OsBridge bridge(OsProcessRunner run) => OsBridge(log: Logger(), events: DaemonBus(), run: run);
+
+  group('openURL', () {
+    test('runs the platform open command with the url and returns true on exit 0', () async {
+      final calls = <List<String>>[];
+      final os = bridge((exe, args) async {
+        calls.add([exe, ...args]);
+        return ProcessResult(0, 0, '', '');
+      });
+      expect(await os.openURL('https://example.com'), isTrue);
+      expect(calls.single.last, 'https://example.com');
+      expect(calls.single.first, isNotEmpty); // xdg-open / open / start
+    });
+
+    test('returns false on a non-zero exit', () async {
+      expect(await bridge((_, _) async => ProcessResult(0, 1, '', 'nope')).openURL('x'), isFalse);
+    });
+
+    test('returns false (never throws) when the runner fails', () async {
+      expect(await bridge((_, _) async => throw 'boom').openURL('x'), isFalse);
+    });
+  });
+
+  group('reveal', () {
+    test('runs the platform reveal command and returns true on exit 0', () async {
+      final calls = <List<String>>[];
+      final os = bridge((exe, args) async {
+        calls.add([exe, ...args]);
+        return ProcessResult(0, 0, '', '');
+      });
+      expect(await os.reveal('/tmp/some/file.txt'), isTrue);
+      expect(calls.single.first, isNotEmpty);
+    });
+
+    test('returns false (never throws) when the runner fails', () async {
+      expect(await bridge((_, _) async => throw 'x').reveal('/tmp/x'), isFalse);
+    });
+  });
+
+  test('fire emits an OS lifecycle event', () async {
+    final bus = DaemonBus();
+    final seen = <OsLifecycleEvent>[];
+    final sub = bus.on<OsLifecycleEvent>().listen(seen.add);
+    OsBridge(log: Logger(), events: bus).fire('resume');
+    await Future<void>.delayed(Duration.zero);
+    await sub.cancel();
+    expect(seen.single.kind, 'resume');
+    expect(seen.single.subsystem, 'os');
+  });
+}

test/widgets/clide_code_block_test.dart

@@ -0,0 +1,72 @@
+import 'package:clide/kernel/src/syntax/syntax_result.dart' show SyntaxSpan;
+import 'package:clide/kernel/src/theme/tokens.dart' show SurfaceTokens;
+import 'package:clide/widgets/src/clide_code_block.dart';
+import 'package:clide/widgets/src/clide_settings.dart';
+import 'package:flutter/widgets.dart';
+import 'package:flutter_test/flutter_test.dart';
+
+import '../helpers/kernel_fixture.dart';
+import '../helpers/widget_harness.dart';
+
+void main() {
+  late KernelFixture f;
+  setUp(() async => f = await KernelFixture.create());
+  tearDown(() => f.dispose());
+
+  Future<SurfaceTokens> pumpForTokens(WidgetTester tester) async {
+    late SurfaceTokens tokens;
+    await tester.pumpWidget(
+      anchoredHarness(
+        f,
+        Builder(
+          builder: (ctx) {
+            tokens = ClideSettings.theme.of(ctx).surface;
+            return const SizedBox();
+          },
+        ),
+      ),
+    );
+    return tokens;
+  }
+
+  testWidgets('renders plain source when no language is given', (tester) async {
+    await tester.pumpWidget(anchoredHarness(f, const ClideCodeBlock(source: 'hello world')));
+    await tester.pump();
+    expect(find.byType(ClideCodeBlock), findsOneWidget);
+  });
+
+  testWidgets('renders plain source for an unknown language (no grammar)', (tester) async {
+    await tester.pumpWidget(anchoredHarness(f, const ClideCodeBlock(source: 'x = 1', language: 'nolang')));
+    await tester.pump();
+    expect(find.byType(ClideCodeBlock), findsOneWidget);
+  });
+
+  testWidgets('buildHighlightedSpan maps byte spans to char ranges across multi-byte + surrogate chars', (tester) async {
+    final tokens = await pumpForTokens(tester);
+    // 'h😀é' — h=1 byte, 😀=surrogate pair (4 bytes / 2 code units), é=2 bytes.
+    // Spans on the h (bytes 0–1) and the é (bytes 5–7); the emoji gap is filled
+    // as plain text. The children must reconstruct the whole source — no bytes
+    // dropped or mis-mapped.
+    const src = 'h😀é';
+    final span = buildHighlightedSpan(
+      src,
+      const [SyntaxSpan(start: 0, end: 1, role: 'keyword'), SyntaxSpan(start: 5, end: 7, role: 'string')],
+      const TextStyle(),
+      tokens,
+    );
+    final joined = span.children!.map((c) => (c as TextSpan).text ?? '').join();
+    expect(joined, src);
+  });
+
+  testWidgets('buildHighlightedSpan clips overlapping spans without duplicating text', (tester) async {
+    final tokens = await pumpForTokens(tester);
+    final span = buildHighlightedSpan(
+      'abcd',
+      const [SyntaxSpan(start: 0, end: 3, role: 'a'), SyntaxSpan(start: 1, end: 4, role: 'b')], // overlap
+      const TextStyle(),
+      tokens,
+    );
+    final joined = span.children!.map((c) => (c as TextSpan).text ?? '').join();
+    expect(joined, 'abcd');
+  });
+}