refactor(chat): route browser chat through one runtime (P3 Slice-Zero Task 5) (#1172)

Co-authored-by: shaggy <[email protected]>

apps/gateway/src/__tests__/conversation-persistence.test.ts

@@ -417,7 +417,7 @@ describe('ConversationsController — search endpoint', () => {
       },
     ];
     brain = createMockBrain({ searchResults });
-    controller = new ConversationsController(brain as never);
+    controller = new ConversationsController(brain as never, { runtimeMode: 'legacy' });
   });
 
   it('returns matching messages for a valid search query', async () => {
@@ -479,7 +479,7 @@ describe('ConversationsController — search endpoint', () => {
 describe('ConversationsController — message CRUD', () => {
   it('listMessages returns 404 when conversation is not owned by user', async () => {
     const brain = createMockBrain({ conversation: undefined });
-    const controller = new ConversationsController(brain as never);
+    const controller = new ConversationsController(brain as never, { runtimeMode: 'legacy' });
 
     await expect(controller.listMessages(CONV_ID, { id: USER_ID })).rejects.toBeInstanceOf(
       NotFoundException,
@@ -489,7 +489,7 @@ describe('ConversationsController — message CRUD', () => {
   it('listMessages returns the messages for an owned conversation', async () => {
     const msgs = [makeMessage('user', 'Test message'), makeMessage('assistant', 'Test reply')];
     const brain = createMockBrain({ conversation: makeConversation(), messages: msgs });
-    const controller = new ConversationsController(brain as never);
+    const controller = new ConversationsController(brain as never, { runtimeMode: 'legacy' });
 
     const result = await controller.listMessages(CONV_ID, { id: USER_ID });
 
@@ -500,7 +500,7 @@ describe('ConversationsController — message CRUD', () => {
 
   it('addMessage returns the persisted message', async () => {
     const brain = createMockBrain({ conversation: makeConversation() });
-    const controller = new ConversationsController(brain as never);
+    const controller = new ConversationsController(brain as never, { runtimeMode: 'legacy' });
 
     const result = await controller.addMessage(
       CONV_ID,

apps/gateway/src/__tests__/integration/tess-cross-surface.integration.test.ts

@@ -35,6 +35,25 @@ function payload(content: string, messageId: string, correlationId: string): Dis
   };
 }
 
+/**
+ * The chat runtime router must never be exercised on the Discord approval/stop control paths —
+ * those paths run entirely through the command-authorization, runtime-provider and durable-session
+ * dependencies. Placed in the gateway's chat-runtime-router slot (the former direct `AgentService`
+ * slot) so any accidental chat-runtime dispatch throws loudly instead of silently passing. Because
+ * approval/stop never resolve a chat runtime, this fixture is never triggered and the integration
+ * stays a GREEN cross-surface control.
+ */
+function failIfUsedChatRuntimeRouter() {
+  return {
+    onModuleInit: () => {
+      throw new Error('chat runtime router must not initialise on the Discord control path');
+    },
+    get active(): never {
+      throw new Error('chat runtime must not be resolved on the Discord approval/stop path');
+    },
+  };
+}
+
 function authorization(): CommandAuthorizationService {
   const entries = new Map<string, string>();
   return new CommandAuthorizationService(
@@ -113,7 +132,7 @@ describe('interaction Discord/CLI durable-session integration', () => {
       },
     );
     const gateway = new ChatGateway(
-      {} as never,
+      failIfUsedChatRuntimeRouter() as never,
       {} as never,
       {} as never,
       {} as never,

apps/gateway/src/__tests__/resource-ownership.test.ts

@@ -60,7 +60,7 @@ describe('Resource ownership checks', () => {
     // The repo enforces ownership via the WHERE clause; it returns undefined when the
     // conversation does not belong to the requesting user.
     brain.conversations.findById.mockResolvedValue(undefined);
-    const controller = new ConversationsController(brain as never);
+    const controller = new ConversationsController(brain as never, { runtimeMode: 'legacy' });
 
     await expect(controller.findOne('conv-1', { id: 'user-1' })).rejects.toBeInstanceOf(
       NotFoundException,