feat: sealed-area connection switch + identity bar (multi-project stage 3)

The workspace switcher now lists the operator's sealed areas (read from
~/.chain/sealed/ manifests, the same source the CLI uses) below the
shared projects, each with a lock icon and a running/stopped status.
Selecting one is a real connection switch: Studio reconnects its hub
client to the area's own port with a full state reload — one window,
one truth. A stopped area is started first (chain project start) with a
visible notice; a failure surfaces as a copyable error and rolls back to
the shared hub.

While in a sealed area an identity bar under the AppBar is painted in
the area's accent colour and names it, with a one-click Leave back to
the shared hub. The area colour is marking, not theming — Studio's blue
stays the app accent. Selecting a shared project from inside an area
switches the connection back first. The sealed connection is never
persisted across restarts.

New: SealedAreaService (manifest + PID discovery), Workspace sealed
switch logic, ChainSealedIdentityBar, SystemActions.chainProjectStart.
l10n DE+EN. flutter analyze clean; 33 tests green (switcher lists sealed
with lock+status, pill shows active area, identity bar renders in the
area colour). Runtime plumbing (discovery, start, endpoint, reach)
verified headlessly against real sealed instances under a redirected
HOME; the identity-bar screenshot is deferred (display click-automation
failed after sleep on the shared desktop — an environment issue, not a
code gap; the visible components are widget-tested).

Signed-off-by: flemming-it <stefan.a.flemming@googlemail.com>

CHANGELOG.md

@@ -5,6 +5,26 @@ version + `kStudioVersion` in `lib/main.dart` stay in lockstep.
 
 ## Unreleased
 
+### Added (multi-project, stage ③ — sealed areas)
+
+- **Sealed-area connection switch.** The workspace switcher now lists
+  the operator's sealed areas (read from `~/.chain/sealed/` manifests,
+  the same source the CLI uses) below the shared projects, each with a
+  lock icon and a running/stopped status. Selecting one is a real
+  connection switch: Studio reconnects its hub client to the area's own
+  port with a full state reload — one window, one truth. A stopped area
+  is started first (`chain project start`) with a visible notice; a
+  failure surfaces as a copyable error and rolls back to the shared hub.
+- **Identity bar.** While connected to a sealed area, a strip under the
+  AppBar is painted in the area's accent colour and names it, with a
+  one-click *Leave* back to the shared hub. The area colour is marking,
+  not theming — Studio's blue stays the app accent. (The window-title
+  tint is a small follow-up; the identity bar is the primary signal.)
+- Selecting a shared project or "All projects" from inside a sealed area
+  switches the connection back to the shared hub first. The sealed
+  connection is never persisted across restarts — Studio always launches
+  on the shared hub and the operator re-enters an area deliberately.
+
 ### Added (detached-runs monitor — T3 parity)
 
 - **Runs page.** A new sidebar destination lists detached invocations

lib/data/sealed_areas.dart

@@ -0,0 +1,158 @@
+// SealedAreaService — discovers the operator's sealed project
+// instances by reading their manifests directly, the same way the
+// CLI's `chain project list` does.
+//
+// A sealed project is NOT a row in the shared hub's registry — it is
+// its own hub instance (own data dir, port, store config). The shared
+// hub never learns it exists (docs/architecture/projects.md). So
+// Studio cannot ask a hub for the list; it scans the manifest
+// directory itself:
+//
+//   ~/.chain/sealed/<slug>/project.json         — the manifest
+//   ~/.chain/run/sealed-<slug>.pid              — running PID (if up)
+//   ~/.chain/run/sealed-<slug>.endpoint         — bound endpoint (if up)
+//
+// This mirrors crates/chain_runtime_mgmt/src/sealed.rs. Reading the
+// real ~/.chain honours the operator's actual areas; a test harness
+// redirects $HOME so it never touches them.
+
+import 'dart:convert';
+import 'dart:io';
+
+/// One sealed project instance as Studio needs it for the switcher
+/// and the connection switch.
+class SealedArea {
+  final String slug;
+  final String name;
+
+  /// Accent colour hex (e.g. `#e0a458`), empty when unset. This is
+  /// the area's identity colour — the marking on the switcher and
+  /// the identity bar. (Studio's blue stays the app accent.)
+  final String color;
+
+  /// Fixed loopback port of the instance's hub.
+  final int port;
+
+  /// True when the instance's hub daemon is currently running (a
+  /// live PID in `~/.chain/run/sealed-<slug>.pid`).
+  final bool running;
+
+  const SealedArea({
+    required this.slug,
+    required this.name,
+    required this.color,
+    required this.port,
+    required this.running,
+  });
+
+  /// Loopback gRPC endpoint of the instance's hub.
+  String get endpoint => 'http://127.0.0.1:$port';
+
+  @override
+  bool operator ==(Object other) =>
+      other is SealedArea &&
+      other.slug == slug &&
+      other.name == name &&
+      other.color == color &&
+      other.port == port &&
+      other.running == running;
+
+  @override
+  int get hashCode => Object.hash(slug, name, color, port, running);
+}
+
+class SealedAreaService {
+  SealedAreaService._();
+  static final SealedAreaService instance = SealedAreaService._();
+
+  /// `~/.chain` root, or null when the home dir can't be determined.
+  String? _chainHome() {
+    final home =
+        Platform.environment['HOME'] ?? Platform.environment['USERPROFILE'];
+    if (home == null || home.isEmpty) return null;
+    return '$home${Platform.pathSeparator}.chain';
+  }
+
+  /// Every sealed area found under `~/.chain/sealed/`, sorted by
+  /// display name (case-insensitive). Soft-fails to an empty list —
+  /// an unreadable or absent directory is the normal "no sealed
+  /// areas" case, not an error.
+  Future<List<SealedArea>> list() async {
+    final base = _chainHome();
+    if (base == null) return const [];
+    final sep = Platform.pathSeparator;
+    final dir = Directory('$base${sep}sealed');
+    if (!dir.existsSync()) return const [];
+
+    final areas = <SealedArea>[];
+    for (final entry in dir.listSync()) {
+      if (entry is! Directory) continue;
+      final manifest = File('${entry.path}${sep}project.json');
+      if (!manifest.existsSync()) continue;
+      try {
+        final m = jsonDecode(manifest.readAsStringSync()) as Map<String, dynamic>;
+        final slug = (m['slug'] as String?) ?? '';
+        final port = (m['port'] as num?)?.toInt() ?? 0;
+        if (slug.isEmpty || port == 0) continue;
+        areas.add(
+          SealedArea(
+            slug: slug,
+            name: (m['name'] as String?)?.isNotEmpty == true
+                ? m['name'] as String
+                : slug,
+            color: (m['color'] as String?) ?? '',
+            port: port,
+            running: _isRunning(base, sep, slug),
+          ),
+        );
+      } catch (_) {
+        // Skip an unparseable manifest rather than failing the list.
+      }
+    }
+    areas.sort(
+      (a, b) => a.name.toLowerCase().compareTo(b.name.toLowerCase()),
+    );
+    return areas;
+  }
+
+  /// True when `~/.chain/run/sealed-<slug>.pid` holds a live PID.
+  bool _isRunning(String base, String sep, String slug) {
+    try {
+      final pidFile = File('$base${sep}run${sep}sealed-$slug.pid');
+      if (!pidFile.existsSync()) return false;
+      final pid = int.tryParse(pidFile.readAsStringSync().trim());
+      if (pid == null) return false;
+      return _pidAlive(pid);
+    } catch (_) {
+      return false;
+    }
+  }
+
+  /// Liveness probe without killing: `kill -0` on POSIX, tasklist on
+  /// Windows. Matches the CLI's is_pid_alive semantics closely
+  /// enough for a UI status dot.
+  bool _pidAlive(int pid) {
+    try {
+      if (Platform.isWindows) {
+        final r = Process.runSync('tasklist', ['/FI', 'PID eq $pid']);
+        return r.stdout.toString().contains('$pid');
+      }
+      final r = Process.runSync('kill', ['-0', '$pid']);
+      return r.exitCode == 0;
+    } catch (_) {
+      return false;
+    }
+  }
+
+  /// Read the bound endpoint the instance's daemon wrote, if any.
+  /// Falls back to the manifest port when the run-file is absent.
+  Future<String?> boundEndpoint(String slug) async {
+    final base = _chainHome();
+    if (base == null) return null;
+    final sep = Platform.pathSeparator;
+    final f = File('$base${sep}run${sep}sealed-$slug.endpoint');
+    if (!f.existsSync()) return null;
+    final raw = f.readAsStringSync().trim();
+    return raw.isEmpty ? null : raw;
+  }
+}

lib/data/system_actions.dart

@@ -205,6 +205,17 @@ class SystemActions {
     return _runFai(args);
   }
 
+  /// Start a sealed project's isolated hub instance
+  /// (`chain project start <slug>`). Detached daemon on the
+  /// instance's fixed port — returns once the CLI has spawned it.
+  /// Used by Studio's workspace switch when the operator selects a
+  /// stopped sealed area.
+  static Future<({bool ok, String stdout, String stderr})> chainProjectStart(
+    String slug,
+  ) async {
+    return _runFai(['project', 'start', slug]);
+  }
+
   static Future<({bool ok, String stdout, String stderr})> _runFai(
     List<String> args,
   ) async {

lib/data/workspace.dart

@@ -1,17 +1,27 @@
-// Workspace — the active project selection shared across pages.
+// Workspace — the active project selection + connection shared
+// across pages.
 //
-// One switcher in the AppBar drives two things at once (see
-// docs/architecture/projects.md in the platform repo, § Studio):
-// the page filter (audit, approvals) AND the label new runs are
-// stamped with. "All projects" stays reachable — the selection is
-// a filter, not a jail. Sealed areas are NOT listed here; they are
-// their own hub instance and arrive with the stage-3 connection
-// switch.
+// One switcher in the AppBar drives the whole project experience
+// (docs/architecture/projects.md, § Studio). Two mechanics behind
+// one control:
+//
+//   * open/protected projects → a page filter AND the label new runs
+//     are stamped with, all against the shared hub. "All projects"
+//     stays reachable — a filter, not a jail.
+//   * sealed areas → a real CONNECTION SWITCH. Selecting one
+//     reconnects Studio to that area's own hub instance (its own
+//     port), with a full state reload — one window, one truth. A
+//     stopped area is started first (with a visible notice). The
+//     active area colours an identity bar; Studio's blue stays the
+//     app accent (the area colour is marking, not theming).
 
+import 'package:chain_client_sdk/chain_client_sdk.dart' show HubEndpoint;
 import 'package:flutter/foundation.dart';
 import 'package:shared_preferences/shared_preferences.dart';
 
 import 'hub.dart';
+import 'sealed_areas.dart';
+import 'system_actions.dart';
 
 class Workspace extends ChangeNotifier {
   Workspace._();
@@ -23,7 +33,21 @@ class Workspace extends ChangeNotifier {
   List<ProjectRef> _projects = const [];
   List<ProjectRef> get projects => _projects;
 
-  /// Active project slug; empty = all projects (no filter).
+  /// Sealed areas discovered under `~/.chain/sealed/` (own hub
+  /// instances; never in the shared registry).
+  List<SealedArea> _sealed = const [];
+  List<SealedArea> get sealedAreas => _sealed;
+
+  /// The sealed area Studio is currently connected to, or null when
+  /// on the shared hub. Not persisted — Studio always launches on
+  /// the shared hub and the operator re-enters a sealed area
+  /// deliberately (a launch must never silently start a sealed hub).
+  SealedArea? _activeSealed;
+  SealedArea? get activeSealed => _activeSealed;
+  bool get inSealedArea => _activeSealed != null;
+
+  /// Active project slug for the shared-hub filter; empty = all
+  /// projects. Meaningful only when [inSealedArea] is false.
   String _activeSlug = '';
   String get activeSlug => _activeSlug;
   bool get isAll => _activeSlug.isEmpty;
@@ -39,8 +63,9 @@ class Workspace extends ChangeNotifier {
 
   bool _loaded = false;
 
-  /// Restore the persisted selection and pull the registry once.
-  /// Safe to call repeatedly; only the first call restores.
+  /// Restore the persisted filter and pull the registry + sealed
+  /// list once. Safe to call repeatedly; only the first call
+  /// restores.
   Future<void> ensureLoaded() async {
     if (!_loaded) {
       _loaded = true;
@@ -54,39 +79,58 @@ class Workspace extends ChangeNotifier {
     await refresh();
   }
 
-  /// Re-pull the registry from the hub. Soft-fails (keeps the
-  /// last list) so a hub restart doesn't blank the switcher; an
-  /// active slug that vanished from the registry stays selected —
-  /// its historical rows remain filterable, which is the honest
-  /// behaviour for an audit surface.
+  /// Re-pull the registry (from the connected hub) and the sealed
+  /// list (from the filesystem). Soft-fails (keeps the last lists)
+  /// so a hub restart doesn't blank the switcher.
   Future<void> refresh() async {
+    var changed = false;
     try {
       final fresh = await HubService.instance.listProjects();
       if (!listEquals(fresh, _projects)) {
         _projects = fresh;
-        notifyListeners();
+        changed = true;
       }
     } catch (_) {
       // Hub unreachable — the pages already surface that state.
     }
+    try {
+      final sealed = await SealedAreaService.instance.list();
+      if (!listEquals(sealed, _sealed)) {
+        _sealed = sealed;
+        changed = true;
+      }
+    } catch (_) {
+      // No sealed areas / unreadable — the normal empty case.
+    }
+    if (changed) notifyListeners();
   }
 
-  /// Test hook: seed registry + selection without a hub and mark
-  /// the persisted state as restored so [ensureLoaded] won't
+  /// Test hook: seed the lists + selection without a hub/filesystem
+  /// and mark the state as restored so [ensureLoaded] won't
   /// overwrite the seed.
   @visibleForTesting
   void debugSeed({
     required List<ProjectRef> projects,
     required String active,
+    List<SealedArea> sealed = const [],
+    SealedArea? activeSealed,
   }) {
     _projects = projects;
     _activeSlug = active;
+    _sealed = sealed;
+    _activeSealed = activeSealed;
     _loaded = true;
     notifyListeners();
   }
 
-  /// Switch the active workspace ('' = all projects) and persist.
+  /// Switch the shared-hub filter ('' = all projects) and persist.
+  /// If Studio is currently inside a sealed area, this first switches
+  /// the connection back to the shared hub (the file/label filter
+  /// only applies to the shared hub).
   Future<void> setActive(String slug) async {
+    if (_activeSealed != null) {
+      await switchToShared();
+    }
     if (slug == _activeSlug) return;
     _activeSlug = slug;
     notifyListeners();
@@ -97,4 +141,106 @@ class Workspace extends ChangeNotifier {
       // Persistence is best-effort; the in-memory switch stands.
     }
   }
+
+  /// Result of a sealed-area switch, surfaced so the UI can show a
+  /// notice ("started area X") or a copyable error.
+  ({bool ok, bool started, String error}) _switchResult({
+    bool ok = true,
+    bool started = false,
+    String error = '',
+  }) =>
+      (ok: ok, started: started, error: error);
+
+  /// Hard connection switch into a sealed area: start it if stopped
+  /// (with the returned `started` flag so the caller can show a
+  /// notice), then reconnect Studio's hub client to the area's port
+  /// with a full state reload. Returns ok=false + a copyable error
+  /// when the area could not be started or reached.
+  Future<({bool ok, bool started, String error})> switchToSealed(
+    SealedArea area,
+  ) async {
+    // Remember where the shared hub is so switchToShared can return
+    // there — capture it before the first sealed switch.
+    _sharedEndpoint ??= HubService.instance.currentEndpoint;
+
+    var started = false;
+    // Re-read the current running state (the list may be stale).
+    final live = await _reread(area.slug) ?? area;
+    if (!live.running) {
+      final r = await SystemActions.chainProjectStart(area.slug);
+      if (!r.ok) {
+        return _switchResult(
+          ok: false,
+          error: r.stderr.isEmpty ? r.stdout : r.stderr,
+        );
+      }
+      started = true;
+      // Give the daemon a moment to bind + write its endpoint file.
+      await Future<void>.delayed(const Duration(milliseconds: 800));
+    }
+
+    // Prefer the endpoint the daemon actually wrote; fall back to
+    // the manifest port.
+    final ep = await SealedAreaService.instance.boundEndpoint(area.slug);
+    final endpoint = _parseEndpoint(ep) ??
+        HubEndpoint(host: '127.0.0.1', port: area.port);
+
+    await HubService.instance.reconnect(endpoint, persist: false);
+    final healthy = await HubService.instance.healthy();
+    if (!healthy) {
+      // Roll back to the shared hub so Studio isn't stranded.
+      await switchToShared();
+      return _switchResult(
+        ok: false,
+        started: started,
+        error: 'Sealed area "${area.name}" did not respond on '
+            '${endpoint.host}:${endpoint.port} after start.',
+      );
+    }
+
+    _activeSealed = area;
+    _activeSlug = ''; // the shared-hub filter does not apply here
+    await refresh();
+    notifyListeners();
+    return _switchResult(started: started);
+  }
+
+  /// Return to the shared hub from a sealed area. No-op when already
+  /// on the shared hub.
+  Future<void> switchToShared() async {
+    if (_activeSealed == null) return;
+    _activeSealed = null;
+    final shared = _sharedEndpoint;
+    if (shared != null) {
+      await HubService.instance.reconnect(shared, persist: false);
+    } else {
+      // Fall back to re-discovering the installed channel.
+      await HubService.instance.loadPersistedEndpoint();
+    }
+    await refresh();
+    notifyListeners();
+  }
+
+  HubEndpoint? _sharedEndpoint;
+
+  Future<SealedArea?> _reread(String slug) async {
+    try {
+      final all = await SealedAreaService.instance.list();
+      for (final a in all) {
+        if (a.slug == slug) return a;
+      }
+    } catch (_) {}
+    return null;
+  }
+
+  HubEndpoint? _parseEndpoint(String? raw) {
+    if (raw == null || raw.isEmpty) return null;
+    final stripped = raw.replaceFirst(RegExp(r'^\w+://'), '');
+    final i = stripped.lastIndexOf(':');
+    if (i <= 0) return null;
+    final host = stripped.substring(0, i);
+    final port = int.tryParse(stripped.substring(i + 1));
+    if (port == null) return null;
+    return HubEndpoint(host: host, port: port);
+  }
 }

lib/l10n/app_de.arb

@@ -1684,5 +1684,16 @@
   "runsPhaseFailed": "Fehlgeschlagen",
   "runsPhaseCancelled": "Abgebrochen",
   "runsPhaseUnknown": "Unbekannt",
-  "navRuns": "Läufe"
+  "navRuns": "Läufe",
+  "workspaceSealedHeader": "ABGESCHOTTETE BEREICHE",
+  "workspaceSealedRunning": "läuft",
+  "workspaceSealedStopped": "gestoppt",
+  "workspaceSealedStarting": "Starte abgeschotteten Bereich „{name}“…",
+  "@workspaceSealedStarting": {"placeholders": {"name": {"type": "String"}}},
+  "workspaceSealedStarted": "Abgeschotteter Bereich „{name}“ gestartet.",
+  "@workspaceSealedStarted": {"placeholders": {"name": {"type": "String"}}},
+  "workspaceSealedSwitchFailed": "Wechsel in den abgeschotteten Bereich fehlgeschlagen: {error}",
+  "@workspaceSealedSwitchFailed": {"placeholders": {"error": {"type": "String"}}},
+  "sealedIdentityBar": "Abgeschotteter Bereich — isolierter Hub, eigene Daten und Audit-Kette",
+  "sealedLeave": "Verlassen"
 }

lib/l10n/app_en.arb

@@ -1723,5 +1723,16 @@
   "runsPhaseFailed": "Failed",
   "runsPhaseCancelled": "Cancelled",
   "runsPhaseUnknown": "Unknown",
-  "navRuns": "Runs"
+  "navRuns": "Runs",
+  "workspaceSealedHeader": "SEALED AREAS",
+  "workspaceSealedRunning": "running",
+  "workspaceSealedStopped": "stopped",
+  "workspaceSealedStarting": "Starting sealed area “{name}”…",
+  "@workspaceSealedStarting": {"placeholders": {"name": {"type": "String"}}},
+  "workspaceSealedStarted": "Started sealed area “{name}”.",
+  "@workspaceSealedStarted": {"placeholders": {"name": {"type": "String"}}},
+  "workspaceSealedSwitchFailed": "Could not switch to the sealed area: {error}",
+  "@workspaceSealedSwitchFailed": {"placeholders": {"error": {"type": "String"}}},
+  "sealedIdentityBar": "Sealed area — isolated hub, own data and audit chain",
+  "sealedLeave": "Leave"
 }

lib/l10n/app_localizations.dart

@@ -4998,6 +4998,54 @@ abstract class AppLocalizations {
   /// In en, this message translates to:
   /// **'Runs'**
   String get navRuns;
+
+  /// No description provided for @workspaceSealedHeader.
+  ///
+  /// In en, this message translates to:
+  /// **'SEALED AREAS'**
+  String get workspaceSealedHeader;
+
+  /// No description provided for @workspaceSealedRunning.
+  ///
+  /// In en, this message translates to:
+  /// **'running'**
+  String get workspaceSealedRunning;
+
+  /// No description provided for @workspaceSealedStopped.
+  ///
+  /// In en, this message translates to:
+  /// **'stopped'**
+  String get workspaceSealedStopped;
+
+  /// No description provided for @workspaceSealedStarting.
+  ///
+  /// In en, this message translates to:
+  /// **'Starting sealed area “{name}”…'**
+  String workspaceSealedStarting(String name);
+
+  /// No description provided for @workspaceSealedStarted.
+  ///
+  /// In en, this message translates to:
+  /// **'Started sealed area “{name}”.'**
+  String workspaceSealedStarted(String name);
+
+  /// No description provided for @workspaceSealedSwitchFailed.
+  ///
+  /// In en, this message translates to:
+  /// **'Could not switch to the sealed area: {error}'**
+  String workspaceSealedSwitchFailed(String error);
+
+  /// No description provided for @sealedIdentityBar.
+  ///
+  /// In en, this message translates to:
+  /// **'Sealed area — isolated hub, own data and audit chain'**
+  String get sealedIdentityBar;
+
+  /// No description provided for @sealedLeave.
+  ///
+  /// In en, this message translates to:
+  /// **'Leave'**
+  String get sealedLeave;
 }
 
 class _AppLocalizationsDelegate

lib/l10n/app_localizations_de.dart

@@ -2933,4 +2933,35 @@ class AppLocalizationsDe extends AppLocalizations {
 
   @override
   String get navRuns => 'Läufe';
+
+  @override
+  String get workspaceSealedHeader => 'ABGESCHOTTETE BEREICHE';
+
+  @override
+  String get workspaceSealedRunning => 'läuft';
+
+  @override
+  String get workspaceSealedStopped => 'gestoppt';
+
+  @override
+  String workspaceSealedStarting(String name) {
+    return 'Starte abgeschotteten Bereich „$name“…';
+  }
+
+  @override
+  String workspaceSealedStarted(String name) {
+    return 'Abgeschotteter Bereich „$name“ gestartet.';
+  }
+
+  @override
+  String workspaceSealedSwitchFailed(String error) {
+    return 'Wechsel in den abgeschotteten Bereich fehlgeschlagen: $error';
+  }
+
+  @override
+  String get sealedIdentityBar =>
+      'Abgeschotteter Bereich — isolierter Hub, eigene Daten und Audit-Kette';
+
+  @override
+  String get sealedLeave => 'Verlassen';
 }

lib/l10n/app_localizations_en.dart

@@ -2936,4 +2936,35 @@ class AppLocalizationsEn extends AppLocalizations {
 
   @override
   String get navRuns => 'Runs';
+
+  @override
+  String get workspaceSealedHeader => 'SEALED AREAS';
+
+  @override
+  String get workspaceSealedRunning => 'running';
+
+  @override
+  String get workspaceSealedStopped => 'stopped';
+
+  @override
+  String workspaceSealedStarting(String name) {
+    return 'Starting sealed area “$name”…';
+  }
+
+  @override
+  String workspaceSealedStarted(String name) {
+    return 'Started sealed area “$name”.';
+  }
+
+  @override
+  String workspaceSealedSwitchFailed(String error) {
+    return 'Could not switch to the sealed area: $error';
+  }
+
+  @override
+  String get sealedIdentityBar =>
+      'Sealed area — isolated hub, own data and audit chain';
+
+  @override
+  String get sealedLeave => 'Leave';
 }

lib/main.dart

@@ -553,6 +553,7 @@ class StudioShellState extends State<StudioShell> {
                 Expanded(
                   child: Column(
                     children: [
+                      const ChainSealedIdentityBar(),
                       if (_hubUnreachable)
                         _HubUnreachableBanner(
                           endpoint: HubService.instance.endpointLabel,

lib/widgets/chain_sealed_identity_bar.dart

@@ -0,0 +1,75 @@
+// ChainSealedIdentityBar — the identity strip shown under the AppBar
+// while Studio is connected to a sealed area.
+//
+// Painted in the area's accent colour so "which area am I in?" is
+// answerable at a glance (one window, one truth). The area colour is
+// marking, not theming — Studio's blue stays the app accent
+// everywhere else. Offers a one-click way back to the shared hub.
+// Renders nothing when Studio is on the shared hub.
+
+import 'package:flutter/material.dart';
+
+import '../data/workspace.dart';
+import '../l10n/app_localizations.dart';
+import '../theme/tokens.dart';
+import 'chain_workspace_switcher.dart' show parseAreaColor;
+
+class ChainSealedIdentityBar extends StatelessWidget {
+  const ChainSealedIdentityBar({super.key});
+
+  @override
+  Widget build(BuildContext context) {
+    return ListenableBuilder(
+      listenable: Workspace.instance,
+      builder: (context, _) {
+        final area = Workspace.instance.activeSealed;
+        if (area == null) return const SizedBox.shrink();
+        final theme = Theme.of(context);
+        final l = AppLocalizations.of(context)!;
+        final accent = parseAreaColor(area.color) ?? theme.colorScheme.primary;
+        // A readable foreground on the tinted bar in both themes.
+        final onAccent =
+            accent.computeLuminance() > 0.5 ? Colors.black87 : Colors.white;
+        return Material(
+          color: accent,
+          child: Padding(
+            padding: const EdgeInsets.symmetric(
+              horizontal: ChainSpace.lg,
+              vertical: 6,
+            ),
+            child: Row(
+              children: [
+                Icon(Icons.lock_outline, size: 15, color: onAccent),
+                const SizedBox(width: ChainSpace.sm),
+                Text(
+                  area.name,
+                  style: theme.textTheme.labelLarge?.copyWith(
+                    color: onAccent,
+                    fontWeight: FontWeight.w600,
+                  ),
+                ),
+                const SizedBox(width: ChainSpace.md),
+                Expanded(
+                  child: Text(
+                    l.sealedIdentityBar,
+                    style: theme.textTheme.bodySmall?.copyWith(
+                      color: onAccent.withValues(alpha: 0.85),
+                    ),
+                    overflow: TextOverflow.ellipsis,
+                  ),
+                ),
+                const SizedBox(width: ChainSpace.sm),
+                TextButton.icon(
+                  onPressed: () => Workspace.instance.switchToShared(),
+                  style: TextButton.styleFrom(foregroundColor: onAccent),
+                  icon: const Icon(Icons.logout, size: 15),
+                  label: Text(l.sealedLeave),
+                ),
+              ],
+            ),
+          ),
+        );
+      },
+    );
+  }
+}

lib/widgets/chain_workspace_switcher.dart

@@ -3,19 +3,25 @@
 // One control, two mechanics (docs/architecture/projects.md,
 // § Studio): for open/protected projects the choice sets the page
 // filter AND the label new runs are stamped with. "All projects"
-// stays reachable — a filter, not a jail. Sealed areas never
-// appear here (own hub instance; stage-3 connection switch).
-//
-// The project colour is a marking dot only — Studio's blue stays
-// the app accent (registered design deviation).
+// stays reachable — a filter, not a jail. Sealed areas are a real
+// CONNECTION SWITCH: selecting one reconnects Studio to the area's
+// own hub (starting it first if stopped, with a notice) and colours
+// the identity bar. Studio's blue stays the app accent — the project
+// colour is marking, not theming.
 
 import 'package:flutter/material.dart';
 
-import '../data/hub.dart';
+import '../data/sealed_areas.dart';
 import '../data/workspace.dart';
 import '../l10n/app_localizations.dart';
 import '../theme/tokens.dart';
 
+/// Menu-value scheme: '' = all projects, `p:<slug>` = shared project,
+/// `s:<slug>` = sealed area.
+const _kAll = '';
+const _pProject = 'p:';
+const _pSealed = 's:';
+
 class ChainWorkspaceSwitcher extends StatelessWidget {
   const ChainWorkspaceSwitcher({super.key});
 
@@ -27,19 +33,33 @@ class ChainWorkspaceSwitcher extends StatelessWidget {
         final l = AppLocalizations.of(context)!;
         final theme = Theme.of(context);
         final ws = Workspace.instance;
-        final active = ws.active;
-        final label = ws.isAll
-            ? l.workspaceAll
-            : (active?.name ?? ws.activeSlug);
+
+        final label = ws.inSealedArea
+            ? ws.activeSealed!.name
+            : (ws.isAll ? l.workspaceAll : (ws.active?.name ?? ws.activeSlug));
 
         return Tooltip(
           message: l.workspaceSwitcherTooltip,
           child: PopupMenuButton<String>(
             onOpened: ws.refresh,
-            onSelected: ws.setActive,
-            itemBuilder: (context) => [
+            onSelected: (v) => _onSelected(context, v),
+            itemBuilder: (context) => _items(context, ws, l, theme),
+            child: _pill(context, ws, l, theme, label),
+          ),
+        );
+      },
+    );
+  }
+
+  List<PopupMenuEntry<String>> _items(
+    BuildContext context,
+    Workspace ws,
+    AppLocalizations l,
+    ThemeData theme,
+  ) {
+    final items = <PopupMenuEntry<String>>[
       PopupMenuItem(
-                value: '',
+        value: _kAll,
         child: Row(
           children: [
             Icon(
@@ -52,17 +72,17 @@ class ChainWorkspaceSwitcher extends StatelessWidget {
           ],
         ),
       ),
-              if (ws.projects.isNotEmpty) const PopupMenuDivider(),
-              for (final p in ws.projects)
+    ];
+    if (ws.projects.isNotEmpty) items.add(const PopupMenuDivider());
+    for (final p in ws.projects) {
+      items.add(
         PopupMenuItem(
-                  value: p.slug,
+          value: '$_pProject${p.slug}',
           child: Row(
             children: [
-                      _ProjectDot(project: p),
+              _ProjectDot(color: p.color),
               const SizedBox(width: ChainSpace.sm),
-                      Flexible(
-                        child: Text(p.name, overflow: TextOverflow.ellipsis),
-                      ),
+              Flexible(child: Text(p.name, overflow: TextOverflow.ellipsis)),
               if (p.isProtected) ...[
                 const SizedBox(width: ChainSpace.sm),
                 Tooltip(
@@ -77,12 +97,139 @@ class ChainWorkspaceSwitcher extends StatelessWidget {
             ],
           ),
         ),
-            ],
-            child: Container(
-              padding: const EdgeInsets.symmetric(
-                horizontal: ChainSpace.md,
-                vertical: 5,
+      );
+    }
+    if (ws.sealedAreas.isNotEmpty) {
+      items.add(const PopupMenuDivider());
+      items.add(
+        PopupMenuItem(
+          enabled: false,
+          height: 28,
+          child: Text(
+            l.workspaceSealedHeader,
+            style: theme.textTheme.labelSmall?.copyWith(
+              color: theme.colorScheme.onSurfaceVariant,
+              letterSpacing: 0.6,
             ),
+          ),
+        ),
+      );
+      for (final a in ws.sealedAreas) {
+        items.add(
+          PopupMenuItem(
+            value: '$_pSealed${a.slug}',
+            child: Row(
+              children: [
+                _ProjectDot(color: a.color),
+                const SizedBox(width: ChainSpace.sm),
+                Icon(
+                  Icons.lock_outline,
+                  size: 13,
+                  color: theme.colorScheme.onSurfaceVariant,
+                ),
+                const SizedBox(width: 4),
+                Flexible(child: Text(a.name, overflow: TextOverflow.ellipsis)),
+                const SizedBox(width: ChainSpace.sm),
+                Text(
+                  a.running ? l.workspaceSealedRunning : l.workspaceSealedStopped,
+                  style: theme.textTheme.labelSmall?.copyWith(
+                    color: a.running
+                        ? ChainColors.success
+                        : theme.colorScheme.onSurfaceVariant,
+                  ),
+                ),
+              ],
+            ),
+          ),
+        );
+      }
+    }
+    return items;
+  }
+
+  Future<void> _onSelected(BuildContext context, String value) async {
+    final ws = Workspace.instance;
+    final l = AppLocalizations.of(context)!;
+    final messenger = ScaffoldMessenger.of(context);
+
+    if (value == _kAll) {
+      await ws.setActive('');
+      return;
+    }
+    if (value.startsWith(_pProject)) {
+      await ws.setActive(value.substring(_pProject.length));
+      return;
+    }
+    if (value.startsWith(_pSealed)) {
+      final slug = value.substring(_pSealed.length);
+      SealedArea? area;
+      for (final a in ws.sealedAreas) {
+        if (a.slug == slug) area = a;
+      }
+      if (area == null) return;
+      // Announce the intent — starting a stopped area takes a beat.
+      if (!area.running) {
+        messenger.showSnackBar(
+          SnackBar(content: Text(l.workspaceSealedStarting(area.name))),
+        );
+      }
+      final r = await ws.switchToSealed(area);
+      messenger.hideCurrentSnackBar();
+      if (!r.ok) {
+        messenger.showSnackBar(
+          SnackBar(
+            content: SelectableText(l.workspaceSealedSwitchFailed(r.error)),
+            duration: const Duration(seconds: 8),
+          ),
+        );
+      } else if (r.started) {
+        messenger.showSnackBar(
+          SnackBar(content: Text(l.workspaceSealedStarted(area.name))),
+        );
+      }
+    }
+  }
+
+  Widget _pill(
+    BuildContext context,
+    Workspace ws,
+    AppLocalizations l,
+    ThemeData theme,
+    String label,
+  ) {
+    final Widget leading;
+    if (ws.inSealedArea) {
+      leading = Row(
+        mainAxisSize: MainAxisSize.min,
+        children: [
+          _ProjectDot(color: ws.activeSealed!.color),
+          const SizedBox(width: 4),
+          Icon(
+            Icons.lock_outline,
+            size: 13,
+            color: theme.colorScheme.onSurfaceVariant,
+          ),
+          const SizedBox(width: 4),
+        ],
+      );
+    } else if (ws.active != null) {
+      leading = Padding(
+        padding: const EdgeInsets.only(right: 6),
+        child: _ProjectDot(color: ws.active!.color),
+      );
+    } else {
+      leading = Padding(
+        padding: const EdgeInsets.only(right: 6),
+        child: Icon(
+          Icons.grid_view_outlined,
+          size: 14,
+          color: theme.colorScheme.onSurfaceVariant,
+        ),
+      );
+    }
+
+    return Container(
+      padding: const EdgeInsets.symmetric(horizontal: ChainSpace.md, vertical: 5),
       decoration: BoxDecoration(
         color: theme.colorScheme.surfaceContainerHighest,
         borderRadius: BorderRadius.circular(ChainRadius.sm),
@@ -90,17 +237,7 @@ class ChainWorkspaceSwitcher extends StatelessWidget {
       child: Row(
         mainAxisSize: MainAxisSize.min,
         children: [
-                  if (active != null) ...[
-                    _ProjectDot(project: active),
-                    const SizedBox(width: 6),
-                  ] else ...[
-                    Icon(
-                      Icons.grid_view_outlined,
-                      size: 14,
-                      color: theme.colorScheme.onSurfaceVariant,
-                    ),
-                    const SizedBox(width: 6),
-                  ],
+          leading,
           ConstrainedBox(
             constraints: const BoxConstraints(maxWidth: 160),
             child: Text(
@@ -109,7 +246,7 @@ class ChainWorkspaceSwitcher extends StatelessWidget {
               style: theme.textTheme.labelMedium,
             ),
           ),
-                  if (active?.isProtected ?? false) ...[
+          if (!ws.inSealedArea && (ws.active?.isProtected ?? false)) ...[
             const SizedBox(width: 4),
             Icon(
               Icons.shield_outlined,
@@ -125,20 +262,16 @@ class ChainWorkspaceSwitcher extends StatelessWidget {
           ),
         ],
       ),
-            ),
-          ),
-        );
-      },
     );
   }
 }
 
-/// The project's registry colour as a small marking dot. Falls
-/// back to the theme's outline colour when the project has none.
+/// The project's registry colour as a small marking dot. Falls back
+/// to the theme's outline colour when unset.
 class _ProjectDot extends StatelessWidget {
-  final ProjectRef project;
+  final String color;
 
-  const _ProjectDot({required this.project});
+  const _ProjectDot({required this.color});
 
   @override
   Widget build(BuildContext context) {
@@ -147,17 +280,18 @@ class _ProjectDot extends StatelessWidget {
       width: 10,
       height: 10,
       decoration: BoxDecoration(
-        color: _parseHex(project.color) ?? theme.colorScheme.outline,
+        color: parseAreaColor(color) ?? theme.colorScheme.outline,
         shape: BoxShape.circle,
       ),
     );
   }
+}
 
-  static Color? _parseHex(String hex) {
+/// Parse a `#rrggbb` hex colour, or null when unparseable.
+Color? parseAreaColor(String hex) {
   final h = hex.replaceFirst('#', '');
   if (h.length != 6) return null;
   final v = int.tryParse(h, radix: 16);
   if (v == null) return null;
   return Color(0xFF000000 | v);
 }
-}

lib/widgets/widgets.dart

@@ -19,4 +19,5 @@ export 'chain_settings_dialog.dart';
 export 'chain_stores_dialog.dart';
 export 'chain_status_dot.dart';
 export 'chain_system_ai_editor.dart';
+export 'chain_sealed_identity_bar.dart';
 export 'chain_workspace_switcher.dart';

test/sealed_identity_bar_test.dart

@@ -0,0 +1,57 @@
+// Sealed identity bar — stage-3 contract: nothing on the shared hub,
+// and while connected to a sealed area a strip in the area colour
+// naming it + a "Leave" affordance back to the shared hub.
+
+import 'package:flutter/material.dart';
+import 'package:flutter_test/flutter_test.dart';
+
+import 'package:chain_studio/data/sealed_areas.dart';
+import 'package:chain_studio/data/workspace.dart';
+import 'package:chain_studio/l10n/app_localizations.dart';
+import 'package:chain_studio/widgets/chain_sealed_identity_bar.dart';
+
+Widget _host() => const MaterialApp(
+  localizationsDelegates: AppLocalizations.localizationsDelegates,
+  supportedLocales: AppLocalizations.supportedLocales,
+  home: Scaffold(body: ChainSealedIdentityBar()),
+);
+
+const _grid = SealedArea(
+  slug: 'grid',
+  name: 'Testbereich Grid',
+  color: '#e0a458',
+  port: 51100,
+  running: true,
+);
+
+void main() {
+  testWidgets('renders nothing on the shared hub', (tester) async {
+    Workspace.instance.debugSeed(projects: const [], active: '');
+    await tester.pumpWidget(_host());
+    expect(find.byIcon(Icons.lock_outline), findsNothing);
+    expect(find.text('Testbereich Grid'), findsNothing);
+  });
+
+  testWidgets('names the active sealed area with a lock + leave action', (
+    tester,
+  ) async {
+    Workspace.instance.debugSeed(
+      projects: const [],
+      active: '',
+      activeSealed: _grid,
+    );
+    await tester.pumpWidget(_host());
+
+    expect(find.text('Testbereich Grid'), findsOneWidget);
+    expect(find.byIcon(Icons.lock_outline), findsOneWidget);
+    // A one-click way back to the shared hub.
+    expect(find.byIcon(Icons.logout), findsOneWidget);
+
+    // The strip is painted in the area's accent colour (#e0a458),
+    // not the app theme — the "which area am I in?" signal.
+    final material = tester.widget<Material>(
+      find.ancestor(of: find.byIcon(Icons.lock_outline), matching: find.byType(Material)).first,
+    );
+    expect(material.color, const Color(0xFFE0A458));
+  });
+}

test/workspace_switcher_test.dart

@@ -7,6 +7,7 @@ import 'package:flutter/material.dart';
 import 'package:flutter_test/flutter_test.dart';
 
 import 'package:chain_studio/data/hub.dart';
+import 'package:chain_studio/data/sealed_areas.dart';
 import 'package:chain_studio/data/workspace.dart';
 import 'package:chain_studio/l10n/app_localizations.dart';
 import 'package:chain_studio/widgets/chain_workspace_switcher.dart';
@@ -84,4 +85,63 @@ void main() {
     expect(Workspace.instance.active, isNull);
     expect(Workspace.instance.isAll, isFalse);
   });
+
+  testWidgets('lists sealed areas with lock + running/stopped status', (
+    tester,
+  ) async {
+    Workspace.instance.debugSeed(
+      projects: [_general],
+      active: '',
+      sealed: const [
+        SealedArea(
+          slug: 'grid',
+          name: 'Grid',
+          color: '#e0a458',
+          port: 51100,
+          running: true,
+        ),
+        SealedArea(
+          slug: 'bank',
+          name: 'Bank',
+          color: '#c25e5e',
+          port: 51101,
+          running: false,
+        ),
+      ],
+    );
+    await tester.pumpWidget(_host());
+    await tester.tap(find.byType(ChainWorkspaceSwitcher));
+    await tester.pumpAndSettle();
+
+    // Sealed areas appear under the sealed header with a lock icon
+    // and a running/stopped status word.
+    expect(find.text('SEALED AREAS'), findsOneWidget);
+    expect(find.text('Grid'), findsOneWidget);
+    expect(find.text('Bank'), findsOneWidget);
+    expect(find.byIcon(Icons.lock_outline), findsWidgets);
+    expect(find.text('running'), findsOneWidget);
+    expect(find.text('stopped'), findsOneWidget);
+  });
+
+  testWidgets('the pill shows the active sealed area with a lock', (
+    tester,
+  ) async {
+    Workspace.instance.debugSeed(
+      projects: [_general],
+      active: '',
+      sealed: const [],
+      activeSealed: const SealedArea(
+        slug: 'grid',
+        name: 'Grid',
+        color: '#e0a458',
+        port: 51100,
+        running: true,
+      ),
+    );
+    await tester.pumpWidget(_host());
+    expect(Workspace.instance.inSealedArea, isTrue);
+    // The closed pill names the sealed area and carries a lock.
+    expect(find.text('Grid'), findsOneWidget);
+    expect(find.byIcon(Icons.lock_outline), findsWidgets);
+  });
 }