handle /resume in clide with a native session picker

Like /clear (T-156), Claude Code's /resume forks to a session the
transcript reader can't follow. clide now owns it: /resume opens a modal
picker of the workspace's recorded sessions — each labelled by its first
… last user prompt and last-active time — and re-binds the pane to the
chosen session-id (killing the current tmux session and respawning on the
picked id). Session enumeration reads bookend prompts from a bounded
window at each end of the transcript, so even multi-MB sessions summarise
cheaply.

T-156.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

CHANGELOG.md

@@ -144,6 +144,10 @@ heading, and (b) bumping `pubspec.yaml` `version:` in the same commit.
   empty session — instead of being forwarded to Claude Code, whose `/clear`
   forked to a new session clide couldn't follow and left the pane
   unresponsive (T-156).
+- `/resume` is now handled by clide too (T-156): it opens a picker of the
+  workspace's past sessions — each labelled by its first … last user message
+  and when it was last active — and re-binds the pane to the chosen one,
+  instead of forwarding Claude Code's session-forking `/resume`.
 - Claude secondary panes no longer flash a false "session exited" while
   the session is alive (a transient tmux client exit is now verified
   against the live session), and the tab and banner agree on the label

lib/builtin/claude/src/claude_pane.dart

@@ -14,7 +14,9 @@ import 'claude_status.dart';
 import 'clipboard_paste.dart';
 import 'conversation_controller.dart';
 import 'conversation_view.dart';
+import 'session_index.dart';
 import 'session_naming.dart';
+import 'session_picker.dart';
 import 'slash_commands.dart';
 import 'tmux_session.dart' as tmux;
 import 'transcript_publisher.dart';
@@ -302,11 +304,16 @@ class _ClaudePaneState extends State<ClaudePane> {
   // does reach it.
   void _send(String text) {
     // Commands clide owns (T-156) are handled here, never forwarded — Claude
-    // Code's /clear forks the session to a new id our reader can't follow, so
-    // we tear this session down and start a fresh one instead.
-    if (clideOwnedCommand(text) == 'clear') {
-      unawaited(_clearSession());
-      return;
+    // Code's /clear and /resume fork the session to a new id our reader can't
+    // follow, so clide drives them: /clear starts fresh, /resume picks a past
+    // session and re-binds to it.
+    switch (clideOwnedCommand(text)) {
+      case 'clear':
+        unawaited(_clearSession());
+        return;
+      case 'resume':
+        unawaited(_resumeFlow());
+        return;
     }
     if (_usingTmux) {
       final session = _sessionName;
@@ -328,13 +335,42 @@ class _ClaudePaneState extends State<ClaudePane> {
     unawaited(ipc.request('pane.write', args: {'id': id, 'text': encodeClaudeInput(text)}));
   }
 
-  /// clide-owned `/clear` (T-156): tear this pane's session down and respawn a
-  /// brand-new, empty one. A fresh session id is forced — even for the primary,
-  /// whose id is normally deterministic — so we start empty rather than resume
-  /// the old transcript; _spawn's self-heal kills the now-stale tmux session
-  /// because the new id has no transcript yet. The old transcript is left on
-  /// disk (history preserved, just detached from this pane).
+  /// clide-owned `/clear` (T-156): respawn this pane on a brand-new, empty
+  /// session. A fresh id is forced — even for the primary, whose id is normally
+  /// deterministic — so we start empty rather than resume the old transcript.
   Future<void> _clearSession() async {
+    if (mounted) setState(() => _statusLine = 'clearing…');
+    await _respawnWithSession(freshSessionId());
+  }
+
+  /// clide-owned `/resume` (T-156): pick a past session for this workspace and
+  /// re-bind the pane to it. Claude Code's own /resume forks to a session our
+  /// reader can't follow, so clide drives the switch.
+  Future<void> _resumeFlow() async {
+    final root = _repoRoot;
+    final dialog = _kernel()?.dialog;
+    if (root == null || dialog == null) return;
+    final home = Platform.environment['HOME'] ?? '';
+    final dir = Directory('$home/.claude/projects/${root.replaceAll('/', '-')}');
+    final sessions = await listSessions(dir);
+    if (!mounted) return;
+    final picked = await dialog.show<String>(
+      (ctx, dismiss) => SessionPickerDialog(
+        sessions: sessions,
+        onPick: (id) => dismiss(id),
+        onCancel: dismiss,
+      ),
+    );
+    if (picked == null || !mounted) return;
+    setState(() => _statusLine = 'resuming…');
+    await _respawnWithSession(picked);
+  }
+
+  /// Tear the current session down and respawn the pane bound to [sessionId].
+  /// The tmux session is killed first so `new-session` starts a fresh client
+  /// on the new id rather than re-attaching the still-running old claude; the
+  /// old transcript is left on disk (history preserved, detached).
+  Future<void> _respawnWithSession(String sessionId) async {
     _conversation?.dispose();
     _conversation = null;
     unawaited(_feed?.dispose());
@@ -343,13 +379,10 @@ class _ClaudePaneState extends State<ClaudePane> {
     _statusSub = null;
     _eventSub?.cancel();
     _eventSub = null;
-    _sessionId = freshSessionId();
-    if (mounted) {
-      setState(() {
-        _status = const SessionStatus();
-        _statusLine = 'clearing…';
-      });
-    }
+    final old = _sessionName;
+    if (old != null) await tmux.killSession(old);
+    _sessionId = sessionId;
+    if (mounted) setState(() => _status = const SessionStatus());
     await _spawn();
   }
 

lib/builtin/claude/src/session_index.dart

@@ -0,0 +1,140 @@
+/// Enumerates the Claude sessions recorded for a workspace and summarises
+/// each by its first and last user message — the labels the /resume picker
+/// shows (T-156). Flutter-free so it unit-tests under `dart test`.
+///
+/// Each session is a `<uuid>.jsonl` transcript in the munged project dir
+/// (`~/.claude/projects/<munged-cwd>/`). Bookends are read from a bounded
+/// window at each end of the file, so even a multi-MB transcript summarises
+/// cheaply.
+library;
+
+import 'dart:convert';
+import 'dart:io';
+
+/// One session in the workspace, summarised for the picker.
+class SessionSummary {
+  const SessionSummary({
+    required this.id,
+    required this.modified,
+    this.firstUser,
+    this.lastUser,
+  });
+
+  /// The session id (the `<uuid>` of `<uuid>.jsonl`).
+  final String id;
+  final DateTime modified;
+
+  /// First / last *user prompt* text in the session (tool-result-only user
+  /// records don't count), or null if none.
+  final String? firstUser;
+  final String? lastUser;
+
+  /// "first … last" — the picker's primary label. Falls back to the id when
+  /// the session carries no user prompt.
+  String get label {
+    final f = firstUser, l = lastUser;
+    if (f == null && l == null) return id;
+    if (f == null) return l!;
+    if (l == null || l == f) return f;
+    return '$f … $l';
+  }
+}
+
+/// The user-prompt text in a transcript record, or null if [record] isn't a
+/// user prompt (e.g. a tool_result-only user record, or a non-user record).
+String? userText(Map<String, Object?> record) {
+  if (record['type'] != 'user') return null;
+  final msg = record['message'];
+  if (msg is! Map) return null;
+  final content = msg['content'];
+  if (content is String) {
+    final t = content.trim();
+    return t.isEmpty ? null : t;
+  }
+  if (content is List) {
+    final texts = content.whereType<Map>().where((b) => b['type'] == 'text').map((b) => b['text']).whereType<String>();
+    final joined = texts.join(' ').trim();
+    return joined.isEmpty ? null : joined;
+  }
+  return null;
+}
+
+String? _firstUserText(Iterable<String> lines) {
+  for (final line in lines) {
+    final t = _userTextOf(line);
+    if (t != null) return t;
+  }
+  return null;
+}
+
+String? _lastUserText(Iterable<String> lines) {
+  String? last;
+  for (final line in lines) {
+    final t = _userTextOf(line);
+    if (t != null) last = t;
+  }
+  return last;
+}
+
+String? _userTextOf(String line) {
+  final trimmed = line.trim();
+  if (trimmed.isEmpty || !trimmed.startsWith('{')) return null;
+  try {
+    return userText(jsonDecode(trimmed) as Map<String, Object?>);
+  } catch (_) {
+    return null;
+  }
+}
+
+/// Sessions in [dir] (the munged project dir), most-recently-modified first,
+/// capped at [max]. Each is summarised by bookend user prompts read from a
+/// bounded [window] at each end of its transcript.
+Future<List<SessionSummary>> listSessions(
+  Directory dir, {
+  int max = 20,
+  int window = 128 * 1024,
+}) async {
+  if (!await dir.exists()) return const [];
+  final files = <File>[];
+  await for (final e in dir.list(followLinks: false)) {
+    if (e is File && e.path.endsWith('.jsonl')) files.add(e);
+  }
+  final summaries = <SessionSummary>[];
+  for (final f in files) {
+    final stat = await f.stat();
+    final bookends = await _bookends(f, window);
+    summaries.add(SessionSummary(
+      id: _sessionId(f.path),
+      modified: stat.modified,
+      firstUser: bookends.first,
+      lastUser: bookends.last,
+    ));
+  }
+  summaries.sort((a, b) => b.modified.compareTo(a.modified));
+  return summaries.length > max ? summaries.sublist(0, max) : summaries;
+}
+
+String _sessionId(String path) {
+  final base = path.split(Platform.pathSeparator).last;
+  return base.endsWith('.jsonl') ? base.substring(0, base.length - 6) : base;
+}
+
+Future<({String? first, String? last})> _bookends(File f, int window) async {
+  final len = await f.length();
+  final raf = await f.open();
+  try {
+    final headLen = len < window ? len : window;
+    final head = const LineSplitter().convert(utf8.decode(await raf.read(headLen), allowMalformed: true));
+    final first = _firstUserText(head);
+
+    if (len <= window) {
+      return (first: first, last: _lastUserText(head));
+    }
+    await raf.setPosition(len - window);
+    var tail = const LineSplitter().convert(utf8.decode(await raf.read(window), allowMalformed: true));
+    if (tail.isNotEmpty) tail = tail.sublist(1); // drop the partial first line
+    return (first: first, last: _lastUserText(tail));
+  } finally {
+    await raf.close();
+  }
+}

lib/builtin/claude/src/session_picker.dart

@@ -0,0 +1,147 @@
+/// Modal picker for `/resume` (T-156): lists the workspace's Claude sessions,
+/// each labelled `first user line … last user line` with its last-modified
+/// time, and returns the chosen session id. No-Material (D-7); shown via the
+/// [DialogRouter].
+library;
+
+import 'package:clide/builtin/claude/src/session_index.dart';
+import 'package:clide/kernel/src/theme/controller.dart';
+import 'package:clide/kernel/src/theme/tokens.dart';
+import 'package:clide/widgets/widgets.dart';
+import 'package:flutter/services.dart';
+import 'package:flutter/widgets.dart';
+
+class SessionPickerDialog extends StatefulWidget {
+  const SessionPickerDialog({
+    super.key,
+    required this.sessions,
+    required this.onPick,
+    required this.onCancel,
+  });
+
+  final List<SessionSummary> sessions;
+  final void Function(String id) onPick;
+  final VoidCallback onCancel;
+
+  @override
+  State<SessionPickerDialog> createState() => _SessionPickerDialogState();
+}
+
+class _SessionPickerDialogState extends State<SessionPickerDialog> {
+  int _selected = 0;
+
+  void _move(int delta) {
+    if (widget.sessions.isEmpty) return;
+    setState(() {
+      _selected = (_selected + delta) % widget.sessions.length;
+      if (_selected < 0) _selected += widget.sessions.length;
+    });
+  }
+
+  void _confirm() {
+    if (widget.sessions.isEmpty) return;
+    widget.onPick(widget.sessions[_selected].id);
+  }
+
+  KeyEventResult _onKey(FocusNode node, KeyEvent e) {
+    if (e is! KeyDownEvent && e is! KeyRepeatEvent) return KeyEventResult.ignored;
+    switch (e.logicalKey) {
+      case LogicalKeyboardKey.arrowDown:
+        _move(1);
+        return KeyEventResult.handled;
+      case LogicalKeyboardKey.arrowUp:
+        _move(-1);
+        return KeyEventResult.handled;
+      case LogicalKeyboardKey.escape:
+        widget.onCancel();
+        return KeyEventResult.handled;
+      case LogicalKeyboardKey.enter:
+      case LogicalKeyboardKey.numpadEnter:
+        _confirm();
+        return KeyEventResult.handled;
+    }
+    return KeyEventResult.ignored;
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    final theme = ClideTheme.of(context).surface;
+    return Focus(
+      autofocus: true,
+      onKeyEvent: _onKey,
+      child: Container(
+        width: 560,
+        constraints: const BoxConstraints(maxHeight: 420),
+        decoration: BoxDecoration(
+          color: theme.panelBackground,
+          border: Border.all(color: theme.globalBorder),
+          borderRadius: BorderRadius.circular(8),
+        ),
+        child: Column(
+          mainAxisSize: MainAxisSize.min,
+          crossAxisAlignment: CrossAxisAlignment.stretch,
+          children: [
+            Padding(
+              padding: const EdgeInsets.fromLTRB(14, 12, 14, 8),
+              child: ClideText('Resume a Claude session', fontSize: clideFontBody, color: theme.globalForeground),
+            ),
+            if (widget.sessions.isEmpty)
+              Padding(
+                padding: const EdgeInsets.fromLTRB(14, 4, 14, 16),
+                child: ClideText('No sessions found for this workspace.', muted: true, fontSize: clideFontSmall),
+              )
+            else
+              Flexible(
+                child: ListView.builder(
+                  shrinkWrap: true,
+                  itemCount: widget.sessions.length,
+                  itemBuilder: (ctx, i) => _row(theme, i),
+                ),
+              ),
+          ],
+        ),
+      ),
+    );
+  }
+
+  Widget _row(SurfaceTokens theme, int i) {
+    final s = widget.sessions[i];
+    final selected = i == _selected;
+    return GestureDetector(
+      onTap: () => widget.onPick(s.id),
+      child: MouseRegion(
+        cursor: SystemMouseCursors.click,
+        child: Container(
+          color: selected ? theme.panelActiveBorder : null,
+          padding: const EdgeInsets.symmetric(horizontal: 14, vertical: 8),
+          child: Column(
+            crossAxisAlignment: CrossAxisAlignment.start,
+            children: [
+              ClideText(
+                s.label,
+                fontSize: clideFontSmall,
+                color: theme.globalForeground,
+                maxLines: 2,
+                overflow: TextOverflow.ellipsis,
+              ),
+              const SizedBox(height: 2),
+              ClideText(relativeTime(s.modified), muted: true, fontSize: clideFontSmall),
+            ],
+          ),
+        ),
+      ),
+    );
+  }
+}
+
+/// Short human label for [when] relative to now ("just now", "5m ago", …).
+String relativeTime(DateTime when, {DateTime? now}) {
+  final d = (now ?? DateTime.now()).difference(when);
+  if (d.inSeconds < 45) return 'just now';
+  if (d.inMinutes < 60) return '${d.inMinutes}m ago';
+  if (d.inHours < 24) return '${d.inHours}h ago';
+  if (d.inDays < 7) return '${d.inDays}d ago';
+  final w = when.toLocal();
+  String two(int n) => n.toString().padLeft(2, '0');
+  return '${w.year}-${two(w.month)}-${two(w.day)}';
+}

lib/builtin/claude/src/slash_commands.dart

@@ -30,7 +30,7 @@ bool isKnownSlashCommand(String text, Iterable<String> known) {
 /// Slash commands clide handles itself instead of forwarding to Claude:
 /// Claude Code's own handling forks the session to a new id that clide's
 /// transcript reader can't follow, so clide owns the semantics (T-156).
-const Set<String> kClideOwnedCommands = {'clear'};
+const Set<String> kClideOwnedCommands = {'clear', 'resume'};
 
 /// The clide-owned command in [text] (a single-line leading-slash token in
 /// [kClideOwnedCommands]), or null.

test/builtin/claude/session_index_test.dart

@@ -0,0 +1,116 @@
+import 'dart:convert';
+import 'dart:io';
+
+import 'package:clide/builtin/claude/src/session_index.dart';
+import 'package:test/test.dart';
+
+String userLine(String text) => jsonEncode({
+      'type': 'user',
+      'message': {'role': 'user', 'content': text},
+    });
+
+String userBlocksLine(String text) => jsonEncode({
+      'type': 'user',
+      'message': {
+        'role': 'user',
+        'content': [
+          {'type': 'text', 'text': text},
+        ],
+      },
+    });
+
+String toolResultLine() => jsonEncode({
+      'type': 'user',
+      'message': {
+        'role': 'user',
+        'content': [
+          {'type': 'tool_result', 'content': 'output'},
+        ],
+      },
+    });
+
+String assistantLine(String text) => jsonEncode({
+      'type': 'assistant',
+      'message': {
+        'role': 'assistant',
+        'content': [
+          {'type': 'text', 'text': text},
+        ],
+      },
+    });
+
+void main() {
+  group('userText', () {
+    test('extracts string and text-block content', () {
+      expect(userText(jsonDecode(userLine('hello')) as Map<String, Object?>), 'hello');
+      expect(userText(jsonDecode(userBlocksLine('blocky')) as Map<String, Object?>), 'blocky');
+    });
+
+    test('ignores tool-result-only user records and non-user records', () {
+      expect(userText(jsonDecode(toolResultLine()) as Map<String, Object?>), isNull);
+      expect(userText(jsonDecode(assistantLine('hi')) as Map<String, Object?>), isNull);
+    });
+  });
+
+  group('listSessions', () {
+    late Directory dir;
+    setUp(() async => dir = await Directory.systemTemp.createTemp('session_index_test'));
+    tearDown(() async {
+      if (await dir.exists()) await dir.delete(recursive: true);
+    });
+
+    Future<void> writeSession(String id, List<String> lines) async {
+      await File('${dir.path}/$id.jsonl').writeAsString('${lines.join('\n')}\n');
+    }
+
+    test('empty / missing dir yields no sessions', () async {
+      expect(await listSessions(dir), isEmpty);
+      expect(await listSessions(Directory('${dir.path}/nope')), isEmpty);
+    });
+
+    test('summarises each session with first … last bookends', () async {
+      await writeSession('aaaa', [
+        userLine('start the swallow'),
+        assistantLine('ok'),
+        toolResultLine(),
+        userLine('now the peacock'),
+      ]);
+      final sessions = await listSessions(dir);
+      expect(sessions, hasLength(1));
+      expect(sessions.single.id, 'aaaa');
+      expect(sessions.single.firstUser, 'start the swallow');
+      expect(sessions.single.lastUser, 'now the peacock');
+      expect(sessions.single.label, 'start the swallow … now the peacock');
+    });
+
+    test('a single-prompt session labels without an ellipsis', () async {
+      await writeSession('bbbb', [userLine('only one'), assistantLine('reply')]);
+      expect((await listSessions(dir)).single.label, 'only one');
+    });
+
+    test('orders most-recently-modified first', () async {
+      await writeSession('old', [userLine('older')]);
+      await Future<void>.delayed(const Duration(milliseconds: 50));
+      await writeSession('new', [userLine('newer')]);
+      final sessions = await listSessions(dir);
+      expect(sessions.map((s) => s.id), ['new', 'old']);
+      // Defensive: timestamps are non-increasing regardless of FS granularity.
+      for (var i = 1; i < sessions.length; i++) {
+        expect(sessions[i - 1].modified.isBefore(sessions[i].modified), isFalse);
+      }
+    });
+
+    test('reads the last user prompt from the tail of a large transcript', () async {
+      final lines = [
+        userLine('the very first prompt'),
+        for (var i = 0; i < 50; i++) assistantLine('filler line number $i to push past the window'),
+        userLine('the very last prompt'),
+      ];
+      await writeSession('big', lines);
+      // Tiny window forces the head/tail split path.
+      final sessions = await listSessions(dir, window: 256);
+      expect(sessions.single.firstUser, 'the very first prompt');
+      expect(sessions.single.lastUser, 'the very last prompt');
+    });
+  });
+}

test/builtin/claude/session_picker_test.dart

@@ -0,0 +1,81 @@
+import 'package:clide/builtin/claude/src/session_index.dart';
+import 'package:clide/builtin/claude/src/session_picker.dart';
+import 'package:flutter/services.dart';
+import 'package:flutter_test/flutter_test.dart';
+
+import '../../helpers/kernel_fixture.dart';
+import '../../helpers/widget_harness.dart';
+
+void main() {
+  group('relativeTime', () {
+    final now = DateTime(2026, 5, 23, 12);
+    test('buckets recent times', () {
+      expect(relativeTime(now.subtract(const Duration(seconds: 10)), now: now), 'just now');
+      expect(relativeTime(now.subtract(const Duration(minutes: 5)), now: now), '5m ago');
+      expect(relativeTime(now.subtract(const Duration(hours: 3)), now: now), '3h ago');
+      expect(relativeTime(now.subtract(const Duration(days: 2)), now: now), '2d ago');
+    });
+
+    test('falls back to a date for older sessions', () {
+      expect(relativeTime(DateTime(2026, 1, 9), now: now), '2026-01-09');
+    });
+  });
+
+  group('SessionPickerDialog', () {
+    late KernelFixture f;
+    setUp(() async => f = await KernelFixture.create());
+    tearDown(() => f.dispose());
+
+    List<SessionSummary> two() => [
+          SessionSummary(id: 'aaa', modified: DateTime.now(), firstUser: 'first a', lastUser: 'last a'),
+          SessionSummary(id: 'bbb', modified: DateTime.now(), firstUser: 'first b', lastUser: 'last b'),
+        ];
+
+    testWidgets('renders first … last labels and picks with arrow + Enter', (tester) async {
+      String? picked;
+      await tester.pumpWidget(harness(
+        f,
+        SessionPickerDialog(sessions: two(), onPick: (id) => picked = id, onCancel: () {}),
+      ));
+      await tester.pump();
+      expect(find.text('first a … last a'), findsOneWidget);
+      expect(find.text('first b … last b'), findsOneWidget);
+
+      await tester.sendKeyEvent(LogicalKeyboardKey.arrowDown); // select bbb
+      await tester.pump();
+      await tester.sendKeyEvent(LogicalKeyboardKey.enter);
+      expect(picked, 'bbb');
+    });
+
+    testWidgets('Escape cancels', (tester) async {
+      var cancelled = false;
+      await tester.pumpWidget(harness(
+        f,
+        SessionPickerDialog(sessions: two(), onPick: (_) {}, onCancel: () => cancelled = true),
+      ));
+      await tester.pump();
+      await tester.sendKeyEvent(LogicalKeyboardKey.escape);
+      expect(cancelled, isTrue);
+    });
+
+    testWidgets('tap picks a row', (tester) async {
+      String? picked;
+      await tester.pumpWidget(harness(
+        f,
+        SessionPickerDialog(sessions: two(), onPick: (id) => picked = id, onCancel: () {}),
+      ));
+      await tester.pump();
+      await tester.tap(find.text('first b … last b'));
+      expect(picked, 'bbb');
+    });
+
+    testWidgets('empty list shows a message', (tester) async {
+      await tester.pumpWidget(harness(
+        f,
+        SessionPickerDialog(sessions: const [], onPick: (_) {}, onCancel: () {}),
+      ));
+      await tester.pump();
+      expect(find.text('No sessions found for this workspace.'), findsOneWidget);
+    });
+  });
+}

test/builtin/claude/slash_commands_test.dart

@@ -37,9 +37,10 @@ void main() {
   });
 
   group('clideOwnedCommand', () {
-    test('recognises /clear as clide-owned', () {
+    test('recognises /clear and /resume as clide-owned', () {
       expect(clideOwnedCommand('/clear'), 'clear');
       expect(clideOwnedCommand('/clear '), 'clear');
+      expect(clideOwnedCommand('/resume'), 'resume');
     });
 
     test('returns null for commands clide forwards to Claude', () {