[codex] fix server LLM model auto-selection

lib/store/settings.ts

@@ -1325,11 +1325,15 @@ export const useSettingsStore = create<SettingsState>()(
                 if (models?.length) recoveredVideoModel = models[0].id;
               }
 
+              const llmModels = validLLMProvider
+                ? (newProvidersConfig[validLLMProvider as ProviderId]?.models ?? [])
+                : [];
               const validLLMModel = validLLMProvider
-                ? validateModel(
-                    state.modelId,
-                    newProvidersConfig[validLLMProvider as ProviderId]?.models ?? [],
-                  )
+                ? validateModel(state.modelId, llmModels) ||
+                  (newProvidersConfig[validLLMProvider as ProviderId]?.isServerConfigured
+                    ? llmModels[0]?.id
+                    : '') ||
+                  ''
                 : '';
               const imageModels =
                 IMAGE_PROVIDERS[validImageProvider as ImageProviderId]?.models ?? [];

tests/store/settings-server-sync.test.ts

@@ -41,6 +41,18 @@ vi.mock('@/lib/ai/providers', () => ({
         { id: 'claude-haiku-4-5', name: 'Claude Haiku 4.5' },
       ],
     },
+    deepseek: {
+      id: 'deepseek',
+      name: 'DeepSeek',
+      type: 'openai',
+      defaultBaseUrl: 'https://api.deepseek.com/v1',
+      requiresApiKey: true,
+      icon: '/logos/deepseek.svg',
+      models: [
+        { id: 'deepseek-v4-pro', name: 'DeepSeek V4 Pro' },
+        { id: 'deepseek-v4-flash', name: 'DeepSeek V4 Flash' },
+      ],
+    },
   },
 }));
 
@@ -506,6 +518,23 @@ describe('fetchServerProviders — provider availability sync', () => {
     expect(store.getState().modelId).toBe('gpt-4o');
   });
 
+  it('selects the server LLM model when provider fallback replaces the default provider', async () => {
+    const store = await getStore();
+
+    expect(store.getState().providerId).toBe('openai');
+    expect(store.getState().modelId).toBe('');
+
+    mockServerResponse({
+      providers: {
+        deepseek: { models: ['deepseek-chat'] },
+      },
+    });
+    await store.getState().fetchServerProviders();
+
+    expect(store.getState().providerId).toBe('deepseek');
+    expect(store.getState().modelId).toBe('deepseek-chat');
+  });
+
   // ---- Error handling ----
 
   it('does not modify state when fetch returns non-ok response', async () => {