fix: harden runtime operation capability contracts

apps/flutter/lib/src/client/t4_client_controller.dart

@@ -188,8 +188,7 @@ final class T4ClientController extends ChangeNotifier implements T4Actions {
     final choices = <ComposerModelChoice>[];
     final seen = <String>{};
     final slashCommands = <String, ComposerSlashCommand>{};
-    final operationCapabilities =
-        _catalogFrame?.operations ?? const <OperationCapability>[];
+    final operationCapabilities = _catalogFrame?.operations;
     for (final item in _catalogItems) {
       if (item.kind == 'model') {
         final selector = modelItemSelector(item);
@@ -207,7 +206,11 @@ final class T4ClientController extends ChangeNotifier implements T4Actions {
         );
         continue;
       }
-      if (item.kind != 'command' || operationCapabilities.isNotEmpty) continue;
+      if (item.kind != 'command' || operationCapabilities != null) continue;
+      final metadata = item.metadata ?? const <String, Object?>{};
+      if (!item.name.startsWith('/') && metadata['slashCommand'] != true) {
+        continue;
+      }
       final bareName = item.name.replaceFirst(RegExp(r'^/+'), '');
       final missingCapability = item.capabilities
           ?.where((capability) => !_grantedCapabilities.contains(capability))
@@ -225,7 +228,8 @@ final class T4ClientController extends ChangeNotifier implements T4Actions {
         disabledReason: disabledReason,
       );
     }
-    for (final operation in operationCapabilities) {
+    for (final operation
+        in operationCapabilities ?? const <OperationCapability>[]) {
       if (!operation.operationId.startsWith('slash.')) continue;
       final bareName = operation.operationId.substring('slash.'.length);
       if (bareName.isEmpty) continue;
@@ -241,8 +245,12 @@ final class T4ClientController extends ChangeNotifier implements T4Actions {
                 .map((alias) => '/${alias.replaceFirst(RegExp(r'^/+'), '')}')
                 .toList(growable: false)
           : const <String>[];
-      final missingCapability = operation.capabilities
-          ?.where((capability) => !_grantedCapabilities.contains(capability))
+      final requiredCapabilities = <String>{
+        'sessions.prompt',
+        ...?operation.capabilities,
+      };
+      final missingCapability = requiredCapabilities
+          .where((capability) => !_grantedCapabilities.contains(capability))
           .firstOrNull;
       String? disabledReason;
       if (!operation.supported) {
@@ -252,11 +260,9 @@ final class T4ClientController extends ChangeNotifier implements T4Actions {
         disabledReason = missingCapability == 'terminal.io'
             ? 'Needs terminal access on this host'
             : 'Not granted on this host';
-      } else if ((session.turnActive || _submitting) &&
-          bareName == 'compact') {
+      } else if ((session.turnActive || _submitting) && bareName == 'compact') {
         disabledReason = 'Wait for the turn to finish';
-      } else if ((session.turnActive || _submitting) &&
-          bareName == 'retry') {
+      } else if ((session.turnActive || _submitting) && bareName == 'retry') {
         disabledReason = 'A turn is already running';
       }
       slashCommands[name] = ComposerSlashCommand(

apps/flutter/lib/src/protocol/models.dart

@@ -585,12 +585,12 @@ final class CatalogResult {
   const CatalogResult({
     required this.revision,
     required this.items,
-    this.operations = const <OperationCapability>[],
+    this.operations,
   });
 
   final String revision;
   final List<CatalogItem> items;
-  final List<OperationCapability> operations;
+  final List<OperationCapability>? operations;
 }
 
 final class SettingsResult {
@@ -1235,14 +1235,14 @@ final class CatalogFrame extends WireFrame {
     required this.hostId,
     required this.revision,
     required this.items,
-    this.operations = const <OperationCapability>[],
+    this.operations,
     required super.raw,
   });
 
   final String hostId;
   final String revision;
   final List<CatalogItem> items;
-  final List<OperationCapability> operations;
+  final List<OperationCapability>? operations;
 }
 
 final class SettingsFrame extends WireFrame {

apps/flutter/lib/src/protocol/wire_decoder.dart

@@ -1299,12 +1299,12 @@ OperationCapability _operationCapability(Object? value, String path) {
   );
 }
 
-List<OperationCapability> _operationCapabilities(
+List<OperationCapability>? _operationCapabilities(
   Map<String, Object?> raw,
   String path,
 ) {
   if (!raw.containsKey('operations')) {
-    return const <OperationCapability>[];
+    return null;
   }
   final values = _list(raw['operations'], path);
   return List<OperationCapability>.unmodifiable([

apps/flutter/lib/src/ui/conversation_pane.dart

@@ -930,6 +930,7 @@ final class _PromptComposerState extends State<_PromptComposer> {
   bool get _ready =>
       widget.state.connectionPhase == ConnectionPhase.ready &&
       widget.state.selectedSession != null &&
+      widget.state.grantedCapabilities.contains('sessions.prompt') &&
       !_sending;
 
   bool get _canSubmit =>

apps/flutter/test/client/t4_client_controller_test.dart

@@ -522,7 +522,6 @@ void main() {
             'description': 'Compact the active conversation',
             'execution': 'headless',
             'supported': true,
-            'capabilities': <Object?>['sessions.prompt'],
             'metadata': <String, Object?>{
               'aliases': <Object?>['compress'],
             },
@@ -553,6 +552,86 @@ void main() {
         commands.last.disabledReason,
         '/plan requires the OMP terminal interface.',
       );
+
+      channel.emit(<String, Object?>{
+        'v': 'omp-app/1',
+        'type': 'catalog',
+        'hostId': 'host-alpha',
+        'revision': 'catalog-authoritative-empty',
+        'items': <Object?>[
+          <String, Object?>{
+            'id': 'command:legacy-compact',
+            'kind': 'command',
+            'name': '/compact',
+          },
+          <String, Object?>{
+            'id': 'command:session.cancel',
+            'kind': 'command',
+            'name': 'session.cancel',
+          },
+        ],
+        'operations': <Object?>[],
+      });
+      await _flush();
+      expect(controller.state.composer.slashCommands, isEmpty);
+    },
+  );
+
+  test(
+    'read-only catalog clients see official headless commands disabled',
+    () async {
+      final profile = _profile('alpha');
+      final connector = _FakeConnector();
+      final controller = _controller(
+        _MemoryDirectoryStore(
+          directory: const HostDirectory.empty().upsert(profile),
+        ),
+        _MemoryCredentialStore(),
+        connector,
+      );
+      addTearDown(controller.dispose);
+      await controller.initialize();
+      final channel = connector.channels.single;
+
+      channel.emit(
+        _welcome(
+          'host-alpha',
+          capabilities: const <String>['sessions.read', 'catalog.read'],
+          features: const <String>['catalog.metadata'],
+        ),
+      );
+      await _flush();
+      final list = channel.sentJson.firstWhere(
+        (frame) => frame['command'] == 'session.list',
+      );
+      channel.emit(
+        _response(
+          list,
+          command: 'session.list',
+          result: _sessionListResult('host-alpha'),
+        ),
+      );
+      channel.emit(<String, Object?>{
+        'v': 'omp-app/1',
+        'type': 'catalog',
+        'hostId': 'host-alpha',
+        'revision': 'catalog-read-only',
+        'items': <Object?>[],
+        'operations': <Object?>[
+          <String, Object?>{
+            'operationId': 'slash.compact',
+            'label': '/compact',
+            'execution': 'headless',
+            'supported': true,
+          },
+        ],
+      });
+      await _flush();
+
+      expect(
+        controller.state.composer.slashCommands.single.disabledReason,
+        'Not granted on this host',
+      );
     },
   );
 

apps/flutter/test/protocol/wire_conformance_test.dart

@@ -207,7 +207,7 @@ void main() {
 
       expect(result.revision, 'capabilities-v1');
       expect(
-        result.operations.map((operation) => operation.operationId),
+        result.operations!.map((operation) => operation.operationId),
         <String>[
           'session.prompt',
           'slash.compact',
@@ -216,7 +216,7 @@ void main() {
         ],
       );
       expect(
-        result.operations.map((operation) => operation.execution),
+        result.operations!.map((operation) => operation.execution),
         <OperationExecution>[
           OperationExecution.typed,
           OperationExecution.headless,
@@ -225,13 +225,13 @@ void main() {
         ],
       );
       expect(
-        result.operations
+        result.operations!
             .skip(2)
             .map((operation) => operation.disabledReason!.code),
         <String>['terminal_only', 'capability_unavailable'],
       );
       expect(
-        () => result.operations.add(result.operations.first),
+        () => result.operations!.add(result.operations!.first),
         throwsUnsupportedError,
       );
 
@@ -245,6 +245,31 @@ void main() {
       ]);
     });
 
+    test(
+      'catalog decoding preserves missing versus authoritative empty operations',
+      () {
+        Map<String, Object?> catalog([List<Object?>? operations]) {
+          final frame = <String, Object?>{
+            'v': 'omp-app/1',
+            'type': 'catalog',
+            'hostId': 'host-alpha',
+            'revision': operations == null ? 'legacy' : 'authoritative-empty',
+            'items': <Object?>[],
+          };
+          if (operations != null) frame['operations'] = operations;
+          return frame;
+        }
+
+        final legacy =
+            WireDecoder.decode(jsonEncode(catalog())) as CatalogFrame;
+        final authoritative =
+            WireDecoder.decode(jsonEncode(catalog(<Object?>[])))
+                as CatalogFrame;
+        expect(legacy.operations, isNull);
+        expect(authoritative.operations, isEmpty);
+      },
+    );
+
     test(
       'every non-corpus ServerFrame branch rejects a missing requirement',
       () {

apps/flutter/test/ui/host_flow_test.dart

@@ -709,6 +709,47 @@ void main() {
       expect(actions.submittedPrompts, <String>['Alpha draft']);
     },
   );
+  testWidgets(
+    'composer stays disabled when prompt permission was not granted',
+    (tester) async {
+      final profile = HostProfile.parseTailnetAddress(
+        'https://alpha.tailnet-name.ts.net',
+      );
+      final state = T4ViewState(
+        connectionPhase: ConnectionPhase.ready,
+        hostDirectory: HostDirectory.empty().upsert(profile),
+        authenticationPhase: AuthenticationPhase.paired,
+        grantedCapabilities: const <String>{'sessions.read', 'catalog.read'},
+        selectedSessionId: 'session-alpha',
+        sessions: const <SessionSummary>[
+          SessionSummary(
+            hostId: 'host-alpha',
+            sessionId: 'session-alpha',
+            projectId: 'project-alpha',
+            projectName: 'Project Alpha',
+            title: 'Read-only session',
+            revision: 'revision-alpha',
+            status: 'idle',
+          ),
+        ],
+      );
+
+      await pumpApp(
+        tester,
+        state: state,
+        actions: _FakeActions(),
+        size: compactPhone,
+      );
+      await tester.enterText(find.byType(TextField).last, 'Cannot send');
+      await tester.pump();
+      expect(
+        tester
+            .widget<FilledButton>(find.widgetWithText(FilledButton, 'Send'))
+            .onPressed,
+        isNull,
+      );
+    },
+  );
   testWidgets(
     'Fast toggle reads as an inactive toggle when available and off, and selected when on',
     (tester) async {

apps/web/src/features/composer/slash.ts

@@ -42,7 +42,7 @@ export function slashCommandsFromCatalog(
   items: readonly CatalogItem[],
   context: SlashCatalogContext,
   granted: readonly string[],
-  operations: readonly OperationCapability[] = [],
+  operations?: readonly OperationCapability[],
 ): SlashCommand[] {
   const offlineReason =
     context.link === "cached"
@@ -55,12 +55,13 @@ export function slashCommandsFromCatalog(
   // Fall back to legacy command items only when an older host does not expose
   // the new contract at all; otherwise typed commands such as session.cancel
   // would be mistaken for slash commands.
-  if (operations.length === 0) {
+  if (operations === undefined) {
     for (const item of items) {
       if (item.kind !== "command") continue;
+      const metadata = item.metadata ?? {};
+      if (!item.name.startsWith("/") && metadata.slashCommand !== true) continue;
       const bareName = item.name.replace(/^\/+/, "");
       const name = `/${bareName}`;
-      const metadata = item.metadata ?? {};
       const rawAliases = Array.isArray(metadata.aliases) ? metadata.aliases : [];
       const aliases = rawAliases
         .filter((alias): alias is string => typeof alias === "string" && alias !== "")
@@ -93,7 +94,7 @@ export function slashCommandsFromCatalog(
       });
     }
   }
-  for (const operation of operations) {
+  for (const operation of operations ?? []) {
     const operationId = String(operation.operationId);
     if (!operationId.startsWith("slash.")) continue;
     const bareName = operationId.slice("slash.".length);
@@ -107,7 +108,8 @@ export function slashCommandsFromCatalog(
     const aliases = rawAliases
       .filter((alias): alias is string => typeof alias === "string" && alias !== "")
       .map((alias) => `/${alias.replace(/^\/+/, "")}`);
-    const missingCapability = (operation.capabilities ?? []).find(
+    const requiredCapabilities = ["sessions.prompt", ...(operation.capabilities ?? [])];
+    const missingCapability = requiredCapabilities.find(
       (capability) => !granted.includes(capability),
     );
     const disabledReason =
@@ -128,7 +130,7 @@ export function slashCommandsFromCatalog(
       name,
       aliases,
       description: operation.description ?? "",
-      argsHint: "",
+      argsHint: typeof metadata.inlineHint === "string" ? metadata.inlineHint : "",
       disabledReason,
       insert: `${name} `,
     });

apps/web/src/features/session-runtime/live-runtime.ts

@@ -1215,7 +1215,7 @@ export function createLiveSessionRuntime(options: LiveRuntimeOptions): SessionRu
                     readOnlyReason: controlGate === null ? null : controlGate.slashReason,
                   },
                   granted,
-                  catalog.operations ?? [],
+                  catalog.operations,
                 ),
           contextUsedTokens: contextUsage?.used ?? 0,
           contextWindowTokens: contextUsage?.limit ?? 0,