diff --git a/desktop/src/__tests__/generalSettings.test.tsx b/desktop/src/__tests__/generalSettings.test.tsx
index 977ba0bc..19601308 100644
--- a/desktop/src/__tests__/generalSettings.test.tsx
+++ b/desktop/src/__tests__/generalSettings.test.tsx
@@ -878,6 +878,10 @@ describe('Settings > Providers tab', () => {
     MOCK_DELETE_PROVIDER.mockReset()
     MOCK_GET_SETTINGS.mockResolvedValue({})
     MOCK_UPDATE_SETTINGS.mockResolvedValue({})
+    useSettingsStore.setState({
+      locale: 'en',
+      fetchAll: vi.fn().mockResolvedValue(undefined),
+    })
     providerStoreState.providers = [
       {
         id: 'provider-1',
@@ -972,6 +976,58 @@ describe('Settings > Providers tab', () => {
     expect(within(dialog).getByText('Requests will be translated via the local proxy')).toBeInTheDocument()
   })
 
+  it('normalizes blank model mappings to the main model when saving a provider', async () => {
+    providerStoreState.createProvider = vi.fn().mockResolvedValue({
+      id: 'provider-new',
+      presetId: 'custom',
+      name: 'Custom',
+      apiKey: 'sk-test',
+      baseUrl: 'https://api.example.com/anthropic',
+      apiFormat: 'anthropic',
+      models: {
+        main: 'gpt-5.5',
+        haiku: 'gpt-5.5',
+        sonnet: 'gpt-5.5',
+        opus: 'gpt-5.5',
+      },
+    })
+    providerStoreState.presets = [
+      {
+        id: 'custom',
+        name: 'Custom',
+        baseUrl: 'https://api.example.com/anthropic',
+        apiFormat: 'anthropic',
+        defaultModels: {
+          main: '',
+          haiku: '',
+          sonnet: '',
+          opus: '',
+        },
+        needsApiKey: true,
+        websiteUrl: '',
+      },
+    ]
+
+    render(<Settings />)
+
+    fireEvent.click(screen.getByRole('button', { name: /Add Provider|添加服务商/i }))
+    const dialog = screen.getByRole('dialog')
+    fireEvent.change(within(dialog).getByPlaceholderText('sk-...'), { target: { value: 'sk-test' } })
+    fireEvent.change(within(dialog).getByLabelText(/Main Model|主模型/i), { target: { value: 'gpt-5.5' } })
+    fireEvent.click(within(dialog).getByRole('button', { name: /Save|Add|保存|添加/i }))
+
+    await waitFor(() => {
+      expect(providerStoreState.createProvider).toHaveBeenCalledWith(expect.objectContaining({
+        models: {
+          main: 'gpt-5.5',
+          haiku: 'gpt-5.5',
+          sonnet: 'gpt-5.5',
+          opus: 'gpt-5.5',
+        },
+      }))
+    })
+  })
+
   it('hides the API key by default and reveals it from the eye button', () => {
     providerStoreState.presets = [
       {
diff --git a/desktop/src/pages/Settings.tsx b/desktop/src/pages/Settings.tsx
index db7d2c93..3aee9958 100644
--- a/desktop/src/pages/Settings.tsx
+++ b/desktop/src/pages/Settings.tsx
@@ -513,6 +513,16 @@ function buildModelContextWindows(
   return windows
 }
 
+function normalizeModelMapping(models: ModelMapping): ModelMapping {
+  const main = models.main.trim()
+  return {
+    main,
+    haiku: models.haiku.trim() || main,
+    sonnet: models.sonnet.trim() || main,
+    opus: models.opus.trim() || main,
+  }
+}
+
 function updateSettingsJsonAutoCompactWindow(raw: string, value: string): string {
   try {
     const parsed = JSON.parse(raw || '{}') as { env?: Record<string, unknown> }
@@ -685,6 +695,7 @@ function ProviderFormModal({ open, onClose, mode, provider, presets }: ProviderF
         const needsProxy = apiFormat !== 'anthropic'
         const autoCompactWindowEnv = autoCompactWindow.trim()
         const modelContextWindows = buildModelContextWindows(models, modelContextInputs)
+        const normalizedModels = normalizeModelMapping(models)
         const existingEnv = (settings.env as Record<string, string>) || {}
         const cleanedEnv = stripProviderSettingsJsonEnv(existingEnv, presetDefaultEnvKeys)
         const merged = {
@@ -699,10 +710,10 @@ function ProviderFormModal({ open, onClose, mode, provider, presets }: ProviderF
               : {}),
             ANTHROPIC_BASE_URL: needsProxy ? 'http://127.0.0.1:3456/proxy' : baseUrl,
             ...buildSettingsJsonAuthEnv(apiFormat, authStrategy, apiKey, selectedPreset),
-            ANTHROPIC_MODEL: models.main,
-            ANTHROPIC_DEFAULT_HAIKU_MODEL: models.haiku,
-            ANTHROPIC_DEFAULT_SONNET_MODEL: models.sonnet,
-            ANTHROPIC_DEFAULT_OPUS_MODEL: models.opus,
+            ANTHROPIC_MODEL: normalizedModels.main,
+            ANTHROPIC_DEFAULT_HAIKU_MODEL: normalizedModels.haiku,
+            ANTHROPIC_DEFAULT_SONNET_MODEL: normalizedModels.sonnet,
+            ANTHROPIC_DEFAULT_OPUS_MODEL: normalizedModels.opus,
           },
         }
         setSettingsJson(JSON.stringify(merged, null, 2))
@@ -830,7 +841,7 @@ function ProviderFormModal({ open, onClose, mode, provider, presets }: ProviderF
     setModels(nextModels)
     setModelContextInputs(nextInputs)
     setSettingsJson((current) => updateSettingsJsonModelContextWindows(
-      updateSettingsJsonModels(current, nextModels),
+      updateSettingsJsonModels(current, normalizeModelMapping(nextModels)),
       buildModelContextWindows(nextModels, nextInputs),
     ))
   }
@@ -858,6 +869,7 @@ function ProviderFormModal({ open, onClose, mode, provider, presets }: ProviderF
 
   const handleSubmit = async () => {
     if (!canSubmit) return
+    const normalizedModels = normalizeModelMapping(models)
     const parsedAutoCompactWindow = parseAutoCompactWindowInput(autoCompactWindow)
     const parsedModelContextWindows = buildModelContextWindows(models, modelContextInputs)
     setIsSubmitting(true)
@@ -882,7 +894,7 @@ function ProviderFormModal({ open, onClose, mode, provider, presets }: ProviderF
           authStrategy,
           baseUrl: baseUrl.trim(),
           apiFormat,
-          models,
+          models: normalizedModels,
           ...(parsedAutoCompactWindow !== undefined && { autoCompactWindow: parsedAutoCompactWindow }),
           ...(Object.keys(parsedModelContextWindows).length > 0 && { modelContextWindows: parsedModelContextWindows }),
           notes: notes.trim() || undefined,
@@ -893,7 +905,7 @@ function ProviderFormModal({ open, onClose, mode, provider, presets }: ProviderF
           baseUrl: baseUrl.trim(),
           authStrategy,
           apiFormat,
-          models,
+          models: normalizedModels,
           autoCompactWindow: parsedAutoCompactWindow ?? null,
           modelContextWindows: Object.keys(parsedModelContextWindows).length > 0
             ? parsedModelContextWindows
diff --git a/src/server/__tests__/conversation-service.test.ts b/src/server/__tests__/conversation-service.test.ts
index 10dcf615..0f4eefe3 100644
--- a/src/server/__tests__/conversation-service.test.ts
+++ b/src/server/__tests__/conversation-service.test.ts
@@ -276,6 +276,9 @@ describe('ConversationService', () => {
     expect(env.ANTHROPIC_BASE_URL).toBe(`http://127.0.0.1:3456/proxy/providers/${provider.id}`)
     expect(env.ANTHROPIC_API_KEY).toBe('proxy-managed')
     expect(env.ANTHROPIC_MODEL).toBe('kimi-k2.6')
+    expect(env.ANTHROPIC_DEFAULT_HAIKU_MODEL).toBe('kimi-k2.6')
+    expect(env.ANTHROPIC_DEFAULT_SONNET_MODEL).toBe('kimi-k2.6')
+    expect(env.ANTHROPIC_DEFAULT_OPUS_MODEL).toBe('kimi-k2.6')
     expect(env.CLAUDE_CODE_PROVIDER_MANAGED_BY_HOST).toBe('1')
     expect(env.CLAUDE_CODE_ENTRYPOINT).toBeUndefined()
   })
diff --git a/src/server/__tests__/providers.test.ts b/src/server/__tests__/providers.test.ts
index b08e561c..40754b85 100644
--- a/src/server/__tests__/providers.test.ts
+++ b/src/server/__tests__/providers.test.ts
@@ -153,6 +153,28 @@ describe('ProviderService', () => {
       expect(provider.models.main).toBe('model-main')
     })
 
+    test('should normalize empty model mappings to the main model when adding a provider', async () => {
+      const svc = new ProviderService()
+      const provider = await svc.addProvider(sampleInput({
+        models: {
+          main: 'gpt-5.5',
+          haiku: '',
+          sonnet: '   ',
+          opus: '',
+        },
+      }))
+
+      expect(provider.models).toEqual({
+        main: 'gpt-5.5',
+        haiku: 'gpt-5.5',
+        sonnet: 'gpt-5.5',
+        opus: 'gpt-5.5',
+      })
+
+      const config = await readProvidersConfig()
+      expect((config.providers as Array<{ models: unknown }>)[0]?.models).toEqual(provider.models)
+    })
+
     test('new providers should not be auto-activated', async () => {
       const svc = new ProviderService()
       const provider = await svc.addProvider(sampleInput())
@@ -361,6 +383,27 @@ describe('ProviderService', () => {
       expect(env.CLAUDE_CODE_AUTO_COMPACT_WINDOW).toBeUndefined()
     })
 
+    test('should normalize empty model mappings before syncing settings', async () => {
+      const svc = new ProviderService()
+      const provider = await svc.addProvider(sampleInput({
+        models: {
+          main: 'gpt-5.5',
+          haiku: '',
+          sonnet: '',
+          opus: '',
+        },
+      }))
+
+      await svc.activateProvider(provider.id)
+
+      const settings = await readSettings()
+      const env = settings.env as Record<string, string>
+      expect(env.ANTHROPIC_MODEL).toBe('gpt-5.5')
+      expect(env.ANTHROPIC_DEFAULT_HAIKU_MODEL).toBe('gpt-5.5')
+      expect(env.ANTHROPIC_DEFAULT_SONNET_MODEL).toBe('gpt-5.5')
+      expect(env.ANTHROPIC_DEFAULT_OPUS_MODEL).toBe('gpt-5.5')
+    })
+
     test('updating active provider should override and clear model context windows', async () => {
       const svc = new ProviderService()
       const added = await svc.addProvider(sampleInput({
diff --git a/src/server/services/providerService.ts b/src/server/services/providerService.ts
index 2d4202f0..22ef7f80 100644
--- a/src/server/services/providerService.ts
+++ b/src/server/services/providerService.ts
@@ -85,6 +85,16 @@ function isSavedProvider(value: unknown): value is SavedProvider {
   )
 }
 
+function normalizeModelMapping(models: SavedProvider['models']): SavedProvider['models'] {
+  const main = models.main.trim()
+  return {
+    main,
+    haiku: models.haiku.trim() || main,
+    sonnet: models.sonnet.trim() || main,
+    opus: models.opus.trim() || main,
+  }
+}
+
 function normalizeProvidersIndex(value: unknown): ProvidersIndex | null {
   if (!isRecord(value) || !Array.isArray(value.providers)) {
     return null
@@ -258,7 +268,7 @@ export class ProviderService {
       ...(input.authStrategy !== undefined && { authStrategy: input.authStrategy }),
       baseUrl: input.baseUrl,
       apiFormat: input.apiFormat ?? 'anthropic',
-      models: input.models,
+      models: normalizeModelMapping(input.models),
       ...(input.autoCompactWindow !== undefined && { autoCompactWindow: input.autoCompactWindow }),
       ...(input.modelContextWindows !== undefined && { modelContextWindows: input.modelContextWindows }),
       ...(input.notes !== undefined && { notes: input.notes }),
@@ -282,7 +292,7 @@ export class ProviderService {
       ...(input.authStrategy !== undefined && { authStrategy: input.authStrategy }),
       ...(input.baseUrl !== undefined && { baseUrl: input.baseUrl }),
       ...(input.apiFormat !== undefined && { apiFormat: input.apiFormat }),
-      ...(input.models !== undefined && { models: input.models }),
+      ...(input.models !== undefined && { models: normalizeModelMapping(input.models) }),
       ...(typeof input.autoCompactWindow === 'number' && { autoCompactWindow: input.autoCompactWindow }),
       ...(input.modelContextWindows !== undefined && input.modelContextWindows !== null && { modelContextWindows: input.modelContextWindows }),
       ...(input.notes !== undefined && { notes: input.notes }),