fix(desktop): default new sessions to provider main model (#818)

Tested: bun run check:desktop
Confidence: high
Scope-risk: narrow

desktop/src/components/controls/ModelSelector.test.tsx

@@ -97,11 +97,12 @@ describe('ModelSelector', () => {
 
     render(<ModelSelector runtimeKey="session-oauth-on-open" />)
 
-    await clickByRole(/alpha/i)
+    await clickByRole(/provider-main/i)
     await act(async () => {
+      fireEvent.keyDown(document, { key: 'Escape' })
       await Promise.resolve()
     })
-    await clickByRole(/alpha/i)
+    await clickByRole(/provider-main/i)
 
     expect(fetchClaudeStatus).toHaveBeenCalledTimes(1)
     expect(fetchOpenAIStatus).toHaveBeenCalledTimes(1)
@@ -192,7 +193,7 @@ describe('ModelSelector', () => {
 
     render(<ModelSelector runtimeKey="session-1" />)
 
-    await clickByRole(/alpha/i)
+    await clickByRole(/provider-main/i)
     await act(async () => {
       fireEvent.click(screen.getByRole('button', { name: /provider-fast/ }))
       await Promise.resolve()
@@ -210,6 +211,51 @@ describe('ModelSelector', () => {
     })
   })
 
+  it('defaults blank provider-scoped runtime selections to the active provider main model', async () => {
+    useSettingsStore.setState({
+      locale: 'en',
+      availableModels: [
+        { id: 'deepseek-v4-flash', name: 'deepseek-v4-flash', description: 'Main Model · Haiku Model', context: '' },
+        { id: 'deepseek-v4-pro', name: 'deepseek-v4-pro', description: 'Sonnet Model · Opus Model', context: '' },
+      ],
+      currentModel: { id: 'deepseek-v4-pro', name: 'deepseek-v4-pro', description: 'Sonnet Model · Opus Model', context: '' },
+      activeProviderName: 'Custom-DeepSeek-OpenAI',
+    })
+    useProviderStore.setState({
+      providers: [{
+        id: 'deepseek-provider',
+        presetId: 'custom',
+        name: 'Custom-DeepSeek-OpenAI',
+        apiKey: '***',
+        baseUrl: 'https://api.deepseek.com',
+        apiFormat: 'openai_chat',
+        models: {
+          main: 'deepseek-v4-flash',
+          haiku: 'deepseek-v4-flash',
+          sonnet: 'deepseek-v4-pro',
+          opus: 'deepseek-v4-pro',
+        },
+      }],
+      activeId: 'deepseek-provider',
+      hasLoadedProviders: true,
+      isLoading: true,
+    })
+
+    render(<ModelSelector runtimeKey="blank-session" />)
+
+    const trigger = screen.getByRole('button', { name: /deepseek-v4-flash/i })
+    await act(async () => {
+      fireEvent.click(trigger)
+      await Promise.resolve()
+    })
+
+    const flashOption = screen
+      .getAllByRole('button', { name: /deepseek-v4-flash/i })
+      .find((button) => button.textContent?.includes('Main Model'))
+    expect(flashOption).toBeDefined()
+    expect(flashOption?.className).toContain('border-[var(--color-model-option-selected-border)]')
+  })
+
   it('keeps runtime effort scoped to the selected session', async () => {
     const setSessionRuntime = vi.fn()
     useSettingsStore.setState({
@@ -249,12 +295,12 @@ describe('ModelSelector', () => {
 
     render(<ModelSelector runtimeKey="session-1" />)
 
-    await clickByRole(/alpha/i)
+    await clickByRole(/provider-main/i)
     await clickByRole(/^High$/)
 
     expect(useSessionRuntimeStore.getState().selections['session-1']).toEqual({
       providerId: 'provider-a',
-      modelId: 'alpha',
+      modelId: 'provider-main',
       effortLevel: 'high',
     })
     expect(useSessionRuntimeStore.getState().selections['session-2']).toEqual({
@@ -264,7 +310,7 @@ describe('ModelSelector', () => {
     })
     expect(setSessionRuntime).toHaveBeenCalledWith('session-1', {
       providerId: 'provider-a',
-      modelId: 'alpha',
+      modelId: 'provider-main',
       effortLevel: 'high',
     })
     expect(useSettingsStore.getState().effortLevel).toBe('max')
@@ -357,7 +403,7 @@ describe('ModelSelector', () => {
 
     render(<ModelSelector runtimeKey="session-hide" />)
 
-    await clickByRole(/alpha/i)
+    await clickByRole(/provider-main/i)
 
     const dropdown = screen.getByTestId('model-selector-dropdown')
     expect(dropdown.textContent).not.toContain('Claude Official')

desktop/src/components/controls/ModelSelector.tsx

@@ -146,15 +146,17 @@ function resolveDefaultRuntimeSelection(
   providers: SavedProvider[],
   currentModelId: string | undefined,
 ): RuntimeSelection {
-  const inferredProviderId = activeId ?? (
-    activeProviderName
-      ? providers.find((provider) => provider.name === activeProviderName)?.id ?? null
-      : null
-  )
+  const activeProvider = activeId
+    ? providers.find((provider) => provider.id === activeId)
+    : activeProviderName
+      ? providers.find((provider) => provider.name === activeProviderName)
+      : undefined
+  const inferredProviderId = activeId ?? activeProvider?.id ?? null
+  const providerMainModelId = activeProvider?.models.main.trim()
 
   return {
     providerId: inferredProviderId,
-    modelId: currentModelId ?? (
+    modelId: providerMainModelId || currentModelId || (
       inferredProviderId === OPENAI_OFFICIAL_PROVIDER_ID
         ? OPENAI_OFFICIAL_DEFAULT_MODEL_ID
         : OFFICIAL_DEFAULT_MODEL_ID

desktop/src/stores/providerStore.test.ts

@@ -115,6 +115,7 @@ describe('providerStore runtime refresh', () => {
       providerId: provider.id,
       modelId: 'model-main',
     })
+    expect(settingsSetModelMock).not.toHaveBeenCalled()
   })
 
   it('keeps an explicit provider model selection when the model still exists', async () => {
@@ -181,6 +182,21 @@ describe('providerStore runtime refresh', () => {
     expect(settingsSetModelMock).toHaveBeenCalledWith('model-main')
     expect(settingsFetchAllMock).toHaveBeenCalled()
   })
+
+  it('sets the provider main model when updating the active saved provider', async () => {
+    const provider = makeProvider({ models: { main: 'model-flash', haiku: 'model-flash', sonnet: 'model-pro', opus: 'model-pro' } })
+    providersApiMock.update.mockResolvedValue({ provider })
+    providersApiMock.list.mockResolvedValue({
+      providers: [provider],
+      activeId: provider.id,
+    })
+
+    const { useProviderStore } = await import('./providerStore')
+    await useProviderStore.getState().updateProvider(provider.id, { models: provider.models })
+
+    expect(settingsSetModelMock).toHaveBeenCalledWith('model-flash')
+    expect(settingsFetchAllMock).toHaveBeenCalled()
+  })
 })
 
 describe('providerStore reorderProviders', () => {

desktop/src/stores/providerStore.ts

@@ -203,7 +203,16 @@ export const useProviderStore = create<ProviderStore>((set, get) => ({
   updateProvider: async (id, input) => {
     const { provider } = await providersApi.update(id, input)
     await get().fetchProviders()
-    refreshConnectedSessionsForProvider(provider, get().activeId)
+    const activeId = get().activeId
+    if (activeId === provider.id && input.models !== undefined) {
+      const mainModelId = provider.models.main.trim()
+      if (mainModelId) {
+        const settings = useSettingsStore.getState()
+        await settings.setModel(mainModelId)
+        await settings.fetchAll()
+      }
+    }
+    refreshConnectedSessionsForProvider(provider, activeId)
     return provider
   },