T-127: replace InProcessClient with socket loopback

Fourth slice of T-99. The UI's DaemonClient now talks to its own
IpcServer through the same per-workspace Unix socket the C `clide`
client uses — one transport, one wire contract, no second path
through the dispatch tree.

Changes:
* lib/kernel/src/ipc/in_process.dart deleted. Nothing imports it.
* DaemonClient.socketPath becomes mutable + new `reconnectAt(path)`
  method swaps an active client onto a different socket without
  restart. Project switch in main.dart uses it — the dispatcher
  + IpcServer are rebuilt for the new workspace, and the client
  reconnects to the new path.
* main.dart's daemonClientFactory now builds a real DaemonClient
  pointed at workspaceSocketPath(workRoot); swapIpcServer kicks
  off server.start() then client.start() in sequence.
* lib/test_app.dart's pane.spawn smoke test uses dispatcher.dispatch
  directly instead of InProcessClient — same coverage, no dead-end
  import.
* DaemonClient client_test gets a reconnectAt round-trip test.

T-128 (delete IsolateClient + Backend + backend_entry.dart) unblocked.

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

.pql/changelog/ticket_history/2026-05.sql

@@ -1858,3 +1858,5 @@ INSERT INTO ticket_history (ticket_id, field, old_value, new_value, changed_by,
 INSERT INTO ticket_history (ticket_id, field, old_value, new_value, changed_by, changed_at, created_at, updated_at, deleted_at, hash, canonical_version) VALUES ('T-125', 'status', 'in_progress', 'done', NULL, '2026-05-18 15:51:09', '2026-05-18 15:51:09', '2026-05-18 15:51:09', NULL, '938624de487aa2f02e034424cae40c77', 1) ON CONFLICT(hash) DO NOTHING;
 INSERT INTO ticket_history (ticket_id, field, old_value, new_value, changed_by, changed_at, created_at, updated_at, deleted_at, hash, canonical_version) VALUES ('T-126', 'status', 'backlog', 'in_progress', NULL, '2026-05-18 15:54:20', '2026-05-18 15:54:20', '2026-05-18 15:54:20', NULL, '3266e7ea943867f49ff20a90b7f12ae6', 1) ON CONFLICT(hash) DO NOTHING;
 INSERT INTO ticket_history (ticket_id, field, old_value, new_value, changed_by, changed_at, created_at, updated_at, deleted_at, hash, canonical_version) VALUES ('T-126', 'status', 'in_progress', 'done', NULL, '2026-05-18 16:04:29', '2026-05-18 16:04:29', '2026-05-18 16:04:29', NULL, 'b6c783f599585e55ecc36f69ccbcefb1', 1) ON CONFLICT(hash) DO NOTHING;
+INSERT INTO ticket_history (ticket_id, field, old_value, new_value, changed_by, changed_at, created_at, updated_at, deleted_at, hash, canonical_version) VALUES ('T-127', 'status', 'backlog', 'in_progress', NULL, '2026-05-19 09:57:18', '2026-05-19 09:57:18', '2026-05-19 09:57:18', NULL, '64a14cb5d8b9274fd9d72d1e7474040c', 1) ON CONFLICT(hash) DO NOTHING;
+INSERT INTO ticket_history (ticket_id, field, old_value, new_value, changed_by, changed_at, created_at, updated_at, deleted_at, hash, canonical_version) VALUES ('T-127', 'status', 'in_progress', 'done', NULL, '2026-05-19 10:03:26', '2026-05-19 10:03:26', '2026-05-19 10:03:26', NULL, 'b8bf877d2057f7baa5acf6af7a13d529', 1) ON CONFLICT(hash) DO NOTHING;

.pql/changelog/tickets/2026-05.sql

@@ -2134,3 +2134,13 @@ Acceptance:
 5. Documented in assets/licenses.yaml + a one-paragraph note in CONTRIBUTING.md.
 
 Source: T-99 sketch. Depends on T-124 (server) + T-125 (argv translator).', 'done', 'high', NULL, NULL, NULL, '2026-05-18 11:58:57', '2026-05-18 16:04:29', NULL, 'e4be31e3d80dbaadd64e3a4a2fa029e0', 1) ON CONFLICT(id) DO UPDATE SET type=excluded.type, parent_id=excluded.parent_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 (id, type, parent_id, title, description, status, priority, assigned_to, team, decision_ref, created_at, updated_at, deleted_at, hash, canonical_version) VALUES ('T-127', 'task', 'T-99', 'replace InProcessClient call sites with the socket loopback', 'Fourth slice of T-99(a). Convert the in-process callers — KernelServices.boot''s daemonClientFactory and friends — to talk to the local socket instead of the direct in-process dispatch path. Delete InProcessClient afterward.
+
+Acceptance:
+1. lib/kernel/src/ipc/in_process.dart removed; nothing imports it.
+2. main.dart''s daemonClientFactory builds a socket-connected DaemonClient pointed at the local server.
+3. Test fixtures use a synthetic in-memory socket pair (or short-lived AF_UNIX socket in /tmp) for isolation.
+4. Wall-clock perf delta is within reason (no widget rebuild storm; round-trip ~ms) — measure before/after under a representative test.
+5. Falls back to in-process direct dispatch if the perf delta is unacceptable; surface the finding in a Q-record before doing so.
+
+Source: T-99 sketch. Depends on T-124 (server must exist). Blocks T-128 (legacy IPC cleanup).', 'done', 'high', NULL, NULL, NULL, '2026-05-18 11:59:02', '2026-05-19 10:03:26', NULL, 'af4a706880181411b2aecf51d90ea748', 1) ON CONFLICT(id) DO UPDATE SET type=excluded.type, parent_id=excluded.parent_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);

CHANGELOG.md

@@ -30,6 +30,8 @@ heading, and (b) bumping `pubspec.yaml` `version:` in the same commit.
   the umbrella commands (`status`, `tail`, `version`, `ping`) per D-6
   into the wire envelope. Pure Dart; lets the C client (T-126) stay a
   dumb pipe (T-99 / T-125).
+- `DaemonClient.reconnectAt(newPath)` — swap an active client onto a
+  different socket without restart (project switch in T-127).
 - C `clide` shell client at `native/clide-cli/clide.c`. Walks CWD up
   to the git root, hashes to the per-workspace socket (D-70), ships
   argv. `make clide-cli` builds it; on PATH, `clide status` works
@@ -43,10 +45,18 @@ heading, and (b) bumping `pubspec.yaml` `version:` in the same commit.
 
 ### Changed
 
+- In-process IPC dispatch swapped for socket loopback (T-127). The
+  Flutter UI's `DaemonClient` now talks to its own `IpcServer` over
+  the same per-workspace Unix socket the C `clide` client uses — one
+  transport, one contract.
+
 ### Deprecated
 
 ### Removed
 
+- `lib/kernel/src/ipc/in_process.dart` (`InProcessClient`) — replaced
+  by the socket-loopback `DaemonClient` (T-127).
+
 ### Fixed
 
 ### Security

lib/kernel/src/ipc/client.dart

@@ -11,13 +11,15 @@ import 'package:flutter/foundation.dart';
 
 class DaemonClient extends ChangeNotifier {
   DaemonClient({
-    required this.socketPath,
+    required String socketPath,
     required Logger log,
     required DaemonBus events,
-  })  : _log = log,
+  })  : _socketPath = socketPath,
+        _log = log,
         _events = events;
 
-  final String socketPath;
+  String _socketPath;
+  String get socketPath => _socketPath;
   final Logger _log;
   final DaemonBus _events;
 
@@ -47,6 +49,28 @@ class DaemonClient extends ChangeNotifier {
     _setConnected(false);
   }
 
+  /// Point the client at a different socket path and reconnect.
+  /// Used on project switch — the workspace-derived socket path
+  /// (D-70) changes when the user opens a different project, so the
+  /// client follows. Cancels the reconnect timer, closes the live
+  /// socket (failing in-flight requests with `disconnect`), updates
+  /// the path, and re-arms the connect loop. Idempotent if the new
+  /// path equals the current one.
+  Future<void> reconnectAt(String newPath) async {
+    if (newPath == _socketPath && _connected) return;
+    _socketPath = newPath;
+    _reconnectTimer?.cancel();
+    _reconnectTimer = null;
+    final s = _socket;
+    _socket = null;
+    await s?.close();
+    _failPending('socket path changed');
+    _setConnected(false);
+    _disposed = false;
+    _backoff = const Duration(milliseconds: 200);
+    await _connect();
+  }
+
   Future<IpcResponse> request(
     String cmd, {
     Map<String, Object?> args = const {},
@@ -72,12 +96,12 @@ class DaemonClient extends ChangeNotifier {
   Future<void> _connect() async {
     if (_disposed) return;
     try {
-      final addr = InternetAddress(socketPath, type: InternetAddressType.unix);
+      final addr = InternetAddress(_socketPath, type: InternetAddressType.unix);
       final socket = await Socket.connect(addr, 0);
       _socket = socket;
       _backoff = const Duration(milliseconds: 200);
       _setConnected(true);
-      _log.info('ipc', 'connected to $socketPath');
+      _log.info('ipc', 'connected to $_socketPath');
       socket.cast<List<int>>().transform(utf8.decoder).transform(const LineSplitter()).listen(
         _handleLine,
         onDone: _handleDisconnect,

lib/kernel/src/ipc/in_process.dart

@@ -1,29 +0,0 @@
-import 'package:clide/clide.dart';
-import 'package:clide/kernel/src/ipc/client.dart';
-
-class InProcessClient extends DaemonClient {
-  InProcessClient({
-    required super.log,
-    required super.events,
-    required this.dispatcher,
-  }) : super(socketPath: '');
-
-  DaemonDispatcher dispatcher;
-  int _nextReqId = 0;
-
-  @override
-  bool get isConnected => true;
-
-  @override
-  Future<void> start() async {}
-
-  @override
-  Future<void> stop() async {}
-
-  @override
-  Future<IpcResponse> request(String cmd, {Map<String, Object?> args = const {}}) {
-    final id = '${_nextReqId++}';
-    final req = IpcRequest(id: id, cmd: cmd, args: args);
-    return dispatcher.dispatch(req);
-  }
-}

lib/main.dart

@@ -29,7 +29,6 @@ import 'package:clide/builtin/welcome/welcome.dart';
 import 'dart:io' show Directory, Platform;
 
 import 'package:clide/kernel/kernel.dart';
-import 'package:clide/kernel/src/ipc/in_process.dart';
 import 'package:clide/src/daemon/dispatcher.dart';
 import 'package:clide/src/daemon/editor_commands.dart';
 import 'package:clide/src/daemon/files_commands.dart';
@@ -40,6 +39,7 @@ import 'package:clide/src/editor/registry.dart' show EditorRegistry;
 import 'package:clide/src/git/client.dart';
 import 'package:clide/src/cli/argv_dispatch.dart';
 import 'package:clide/src/ipc/envelope.dart';
+import 'package:clide/src/ipc/paths.dart' show workspaceSocketPath;
 import 'package:clide/src/ipc/server.dart';
 import 'package:clide/src/panes/event_sink.dart';
 import 'package:clide/src/panes/registry.dart';
@@ -78,11 +78,13 @@ Future<void> main() async {
     toolchain.applyResolved(resolveToolchainPaths());
   }
 
-  InProcessClient? ipcClient;
+  DaemonClient? ipcClient;
   DaemonBus? daemonBus;
   // IPC socket server (T-99 / T-124, per D-70/71/72). One server per
   // workspace; restarted when the active project switches because the
-  // socket path is workspace-derived.
+  // socket path is workspace-derived. The local DaemonClient connects
+  // back to it over the socket so all IPC — including from UI widgets
+  // in the same process — goes through the wire contract (T-127).
   IpcServer? ipcServer;
   final ipcLog = Logger();
 
@@ -100,6 +102,14 @@ Future<void> main() async {
       await server.start();
     } catch (e, st) {
       ipcLog.error('ipc', 'server start failed', error: e, stackTrace: st);
+      return;
+    }
+    // Point the in-process DaemonClient at the new socket. On first
+    // boot (no client yet) the daemonClientFactory below kicks it
+    // off; on project switch we just reconnect to the new path.
+    final client = ipcClient;
+    if (client != null) {
+      await client.reconnectAt(server.socketPath);
     }
   }
 
@@ -133,18 +143,28 @@ Future<void> main() async {
             daemonBus = events;
             final workRoot = FilesService.atCwd(events: _BusEventSink(events)).root;
             final dispatcher = buildDispatcher(events, toolchain, workRoot);
-            ipcClient = InProcessClient(log: log, events: events, dispatcher: dispatcher);
-            // Fire-and-forget: bring up the IPC socket server alongside.
-            // Failure is logged, not fatal — the UI still works.
-            unawaited(swapIpcServer(dispatcher, workRoot));
-            return ipcClient!;
+            // Build the client at the workspace's socket path. The
+            // server is started below (swapIpcServer) which the
+            // client will then auto-connect to via its reconnect
+            // loop. autoStartDaemonClient:false means we own the
+            // lifecycle here.
+            final client = DaemonClient(
+              socketPath: workspaceSocketPath(workRoot.path),
+              log: log,
+              events: events,
+            );
+            ipcClient = client;
+            unawaited(() async {
+              await swapIpcServer(dispatcher, workRoot);
+              await client.start();
+            }());
+            return client;
           },
     onProjectOpen: kIsWeb
         ? null
         : (path) async {
-            if (ipcClient == null || daemonBus == null) return;
+            if (daemonBus == null) return;
             final dispatcher = buildDispatcher(daemonBus!, toolchain, Directory(path));
-            ipcClient!.dispatcher = dispatcher;
             await swapIpcServer(dispatcher, Directory(path));
           },
   );

lib/test_app.dart

@@ -29,7 +29,6 @@ import 'dart:ffi' as ffi;
 import 'package:ffi/ffi.dart' as pkg_ffi;
 import 'kernel/kernel.dart';
 import 'src/pty/ffi/libc.dart' as libc;
-import 'kernel/src/ipc/in_process.dart';
 import 'src/daemon/pane_commands.dart';
 import 'src/ipc/envelope.dart';
 import 'src/panes/event_sink.dart';
@@ -325,19 +324,25 @@ class _ClideTestAppState extends State<ClideTestApp> {
   Future<void> _runTerminalTests(Toolchain tc, String workDir) async {
     _say('--- terminal ---');
 
-    // Test PTY via InProcessClient — same path as the real app.
+    // Test PTY via the dispatcher directly — skip the socket
+    // round-trip for the smoke test since it adds setup without
+    // testing anything new for pane.spawn. The real app's path is
+    // covered by the IPC server + client tests under test/ipc/.
     await _testAsync('pane.spawn via IPC', () async {
       final dispatcher = DaemonDispatcher();
       final bus = DaemonBus();
       final eventSink = _TestEventSink(bus);
       final paneRegistry = PaneRegistry(events: eventSink);
       registerPaneCommands(dispatcher, paneRegistry);
-      final ipc = InProcessClient(log: Logger(), events: bus, dispatcher: dispatcher);
+
+      Future<IpcResponse> dispatch(String cmd, Map<String, Object?> args) {
+        return dispatcher.dispatch(IpcRequest(id: 'tm-${DateTime.now().microsecondsSinceEpoch}', cmd: cmd, args: args));
+      }
 
       // Spawn a pane running /bin/echo.
       // Use interactive shell — fast-exiting commands lose output on macOS
       // because the slave closes before we can read the master.
-      final spawnResp = await ipc.request('pane.spawn', args: {
+      final spawnResp = await dispatch('pane.spawn', {
         'argv': [tc.shell],
         'kind': 'terminal',
       });

test/kernel/src/ipc/client_test.dart

@@ -276,5 +276,45 @@ void main() {
       await Future<void>.delayed(const Duration(milliseconds: 100));
       expect(flips, contains(true));
     });
+
+    test('reconnectAt swaps socket paths and re-binds (T-127)', () async {
+      final pathA = await _tmpSocket();
+      final daemonA = _TestDaemon(pathA);
+      await daemonA.start();
+      addTearDown(daemonA.close);
+
+      final bus = DaemonBus();
+      addTearDown(bus.dispose);
+      final client = _build(pathA, bus);
+      addTearDown(client.dispose);
+      await client.start();
+      await daemonA.waitForClient();
+      await Future<void>.delayed(const Duration(milliseconds: 50));
+      expect(client.isConnected, isTrue);
+      expect(client.socketPath, pathA);
+
+      // Spin up a SECOND daemon on a different socket and move the
+      // client over to it.
+      final pathB = await _tmpSocket();
+      final daemonB = _TestDaemon(pathB);
+      await daemonB.start();
+      addTearDown(daemonB.close);
+
+      await client.reconnectAt(pathB);
+      await daemonB.waitForClient();
+      await Future<void>.delayed(const Duration(milliseconds: 50));
+      expect(client.socketPath, pathB);
+      expect(client.isConnected, isTrue);
+
+      // A request goes to the NEW daemon — verify by reading the
+      // line off daemonB.lines.
+      final lineFuture = daemonB.lines.first;
+      final responseFuture = client.request('ping');
+      final reqLine = await lineFuture;
+      final reqJson = jsonDecode(reqLine) as Map<String, Object?>;
+      daemonB.send(IpcResponse.ok(id: reqJson['id'] as String, data: const {'pong': true}).encode());
+      final resp = await responseFuture;
+      expect(resp.ok, isTrue);
+    });
   });
 }