Use the fast model for the onboarding setup chat (#23586)

The workspace setup chat ran on the smart model. The hidden kickoff turn
enqueued its job without a `modelId`, and the frontend sends none unless
the user picks one, so every turn fell through to `modelId ??
workspace.smartModel` in `chat-execution.service.ts`.

Two halves, since the kickoff is server-initiated and the frontend never
sends it:
- `startHiddenKickoffStream` takes a `modelId` and the setup chat passes
`workspace.fastModel`.
- `useAgentChatModelId` requests `workspace.fastModel` on the setup
page, so user turns follow. Everywhere else it still sends nothing and
the server fallback is unchanged.

`workspace.fastModel` defaults to the `default-fast-model` sentinel, so
the model still resolves through the registry and stays
admin-overridable. An explicit pick from the model picker still wins.

packages/twenty-server/src/engine/metadata-modules/ai/ai-chat/services/__tests__/agent-chat-streaming.service.kickoff.spec.ts

@@ -85,6 +85,7 @@ describe('AgentChatStreamingService.startHiddenKickoffStream', () => {
     userWorkspaceId: 'user-workspace-id',
     workspace,
     text: kickoffText,
+    modelId: 'default-fast-model',
   };
 
   it('should return null without queueing a visible copy when the claim is lost', async () => {
@@ -124,7 +125,7 @@ describe('AgentChatStreamingService.startHiddenKickoffStream', () => {
     });
   });
 
-  it('should enqueue the hidden kickoff turn without a pinned model and without notifying thread activity', async () => {
+  it('should enqueue the hidden kickoff turn with the given model and without notifying thread activity', async () => {
     const { service, threadRepository, agentChatService, messageQueueService } =
       buildService();
 
@@ -143,13 +144,13 @@ describe('AgentChatStreamingService.startHiddenKickoffStream', () => {
       expect.objectContaining({
         threadId: 'thread-id',
         browsingContext: null,
+        modelId: 'default-fast-model',
         lastUserMessageText: kickoffText,
         lastUserMessageParts: [{ type: 'text', text: kickoffText }],
         hasTitle: true,
         existingTurnId: 'kickoff-turn-id',
       }),
     );
-    expect(messageQueueService.add.mock.calls[0][1].modelId).toBeUndefined();
     expect(agentChatService.notifyThreadActivityUpdated).not.toHaveBeenCalled();
     expect(result).toEqual({
       streamId: expect.any(String),

packages/twenty-server/src/engine/metadata-modules/ai/ai-chat/services/__tests__/workspace-setup-chat.service.spec.ts

@@ -28,6 +28,8 @@ const EXPECTED_THREAD_ID = v5(
 describe('WorkspaceSetupChatService', () => {
   const workspace = {
     id: 'workspace-id',
+    fastModel: 'fast-model-id',
+    smartModel: 'smart-model-id',
   } as WorkspaceEntity;
 
   const startArguments = {
@@ -235,6 +237,7 @@ describe('WorkspaceSetupChatService', () => {
       text: expect.stringContaining(
         'No information about the company that owns this workspace is available.',
       ),
+      modelId: 'fast-model-id',
     });
     expect(result).toEqual({
       outcome: WorkspaceSetupChatOutcome.STARTED,

packages/twenty-server/src/engine/metadata-modules/ai/ai-chat/services/agent-chat-streaming.service.ts

@@ -302,11 +302,13 @@ export class AgentChatStreamingService {
     userWorkspaceId,
     workspace,
     text,
+    modelId,
   }: {
     thread: AgentChatThreadEntity;
     userWorkspaceId: string;
     workspace: WorkspaceEntity;
     text: string;
+    modelId: string;
   }): Promise<{ streamId: string; messageId: string; turnId: string } | null> {
     const threadId = thread.id;
     const streamId = generateId();
@@ -372,6 +374,7 @@ export class AgentChatStreamingService {
           workspaceId: workspace.id,
           messages,
           browsingContext: null,
+          modelId,
           lastUserMessageText: text,
           lastUserMessageParts: [{ type: 'text' as const, text }],
           hasTitle: !!thread.title,
@@ -389,7 +392,7 @@ export class AgentChatStreamingService {
         key: MetricsKeys.AiChatTurnFailed,
         amount: 1,
         attributes: {
-          model: 'unknown',
+          model: modelId,
           failure_phase: 'enqueue',
           error_code: streamError.code,
         },

packages/twenty-server/src/engine/metadata-modules/ai/ai-chat/services/workspace-setup-chat.service.ts

@@ -164,6 +164,7 @@ export class WorkspaceSetupChatService {
           companyEnrichment: companyContext,
           locale,
         }),
+        modelId: workspace.fastModel,
       });
 
     if (!isDefined(kickoffResult)) {