Select the flagship 27B tier by default

src/app/App.test.ts

@@ -1,6 +1,6 @@
 import { describe, expect, it } from 'vitest';
 import { EngineClientError } from '../engine';
-import { reconcileCompletionTokens, reconcileTotalTokens, requiresModelReload } from './App';
+import { DEFAULT_MODEL_ID, reconcileCompletionTokens, reconcileTotalTokens, requiresModelReload } from './App';
 
 function engineError(code: string): EngineClientError {
   return new EngineClientError({ code, message: code });
@@ -20,6 +20,12 @@ describe('App model invalidation policy', () => {
   });
 });
 
+describe('App release defaults', () => {
+  it('opens on the flagship tier required by the product contract', () => {
+    expect(DEFAULT_MODEL_ID).toBe('bonsai-27b');
+  });
+});
+
 describe('App streamed completion telemetry', () => {
   it('uses observed stream events when final engine usage is incomplete', () => {
     expect(reconcileCompletionTokens(5, 64)).toBe(64);

src/app/App.tsx

@@ -39,6 +39,7 @@ const CONVERSATION_ID = 'primary-field-log';
 const MAX_TOOL_ROUNDS = 5;
 const MAX_TOOL_CALLS_PER_ROUND = 4;
 const MAX_TOOL_CALLS_TOTAL = 12;
+export const DEFAULT_MODEL_ID: ModelId = 'bonsai-27b';
 
 const MODEL_DECOR: Record<ModelTierId, {
   id: ModelId;
@@ -258,7 +259,7 @@ export function App() {
   const [client] = useState(getEngineClient);
   const [manifest, setManifest] = useState<ModelManifestV2 | null>(null);
   const [capabilities, setCapabilities] = useState<EngineCapabilities | null>(null);
-  const [activeModelId, setActiveModelId] = useState<ModelId>('bonsai-1.7b');
+  const [activeModelId, setActiveModelId] = useState<ModelId>(DEFAULT_MODEL_ID);
   const [loadedModelId, setLoadedModelId] = useState<ModelId | null>(null);
   const [loadingModelId, setLoadingModelId] = useState<ModelId | null>(null);
   const [messages, setMessages] = useState<ChatMessage[]>([]);