fix(desktop): preserve local model provider endpoint

apps/desktop/src/app/settings/model-settings.test.tsx

@@ -212,6 +212,53 @@ describe('ModelSettings', () => {
     expect(screen.queryByRole('button', { name: 'Set up provider' })).toBeNull()
   })
 
+  it('preserves a user-defined provider endpoint when applying the main model', async () => {
+    getGlobalModelOptions.mockResolvedValueOnce({
+      providers: [
+        {
+          name: 'Nous',
+          slug: 'nous',
+          models: ['hermes-4'],
+          authenticated: true
+        },
+        {
+          name: 'Ollama',
+          slug: 'local-ollama',
+          models: ['qwen3:latest'],
+          authenticated: true,
+          is_user_defined: true,
+          api_url: 'http://localhost:11434/v1'
+        }
+      ]
+    })
+    setModelAssignment.mockResolvedValueOnce({
+      provider: 'local-ollama',
+      model: 'qwen3:latest',
+      gateway_tools: []
+    })
+
+    await renderModelSettings()
+
+    const providerSelect = (await screen.findAllByRole('combobox'))[0]
+    fireEvent.click(providerSelect)
+    fireEvent.click(await screen.findByRole('option', { name: 'Ollama' }))
+
+    const modelSelect = (await screen.findAllByRole('combobox'))[1]
+    fireEvent.click(modelSelect)
+    fireEvent.click(await screen.findByRole('option', { name: 'qwen3:latest' }))
+
+    fireEvent.click(await screen.findByRole('button', { name: 'Apply' }))
+
+    await waitFor(() =>
+      expect(setModelAssignment).toHaveBeenCalledWith({
+        model: 'qwen3:latest',
+        provider: 'local-ollama',
+        scope: 'main',
+        base_url: 'http://localhost:11434/v1'
+      })
+    )
+  })
+
   it('writes the profile default speed (service_tier) when the fast switch is toggled', async () => {
     await renderModelSettings()
     await waitFor(() => expect(getHermesConfigRecord).toHaveBeenCalled())

apps/desktop/src/app/settings/model-settings.tsx

@@ -619,7 +619,12 @@ export function ModelSettings({ onMainModelChanged }: ModelSettingsProps) {
     setError('')
 
     try {
-      const result = await setModelAssignment({ model: selectedModel, provider: selectedProvider, scope: 'main' })
+      const result = await setModelAssignment({
+        model: selectedModel,
+        provider: selectedProvider,
+        scope: 'main',
+        ...(selectedProviderRow?.api_url ? { base_url: selectedProviderRow.api_url } : {})
+      })
 
       if (profileEpoch.current !== epoch) {
         return
@@ -636,7 +641,7 @@ export function ModelSettings({ onMainModelChanged }: ModelSettingsProps) {
     } finally {
       setApplying(false)
     }
-  }, [onMainModelChanged, refresh, selectedModel, selectedProvider])
+  }, [onMainModelChanged, refresh, selectedModel, selectedProvider, selectedProviderRow])
 
   const setAuxiliaryToMain = useCallback(
     async (task: string) => {

apps/desktop/src/types/hermes.ts

@@ -386,6 +386,10 @@ export interface ModelOptionProvider {
   key_env?: string
   /** True for providers defined via the user's `providers:` config block. */
   is_user_defined?: boolean
+  /** OpenAI-compatible endpoint for a user-defined provider. The backend
+   *  exposes this as `api_url`; model assignments send it back as `base_url`
+   *  so switching providers does not discard the selected local endpoint. */
+  api_url?: string
   /** Per-model pricing keyed by model id (present when the picker requested
    *  pricing and the provider supports live pricing). */
   pricing?: Record<string, ModelPricing>