diff --git a/desktop/src/__tests__/generalSettings.test.tsx b/desktop/src/__tests__/generalSettings.test.tsx
index 88269f08..f6302964 100644
--- a/desktop/src/__tests__/generalSettings.test.tsx
+++ b/desktop/src/__tests__/generalSettings.test.tsx
@@ -106,7 +106,11 @@ describe('Settings > General tab', () => {
 
     useSettingsStore.setState({
       locale: 'en',
+      thinkingEnabled: true,
       skipWebFetchPreflight: true,
+      setThinkingEnabled: vi.fn().mockImplementation(async (enabled: boolean) => {
+        useSettingsStore.setState({ thinkingEnabled: enabled })
+      }),
       setSkipWebFetchPreflight: vi.fn().mockImplementation(async (enabled: boolean) => {
         useSettingsStore.setState({ skipWebFetchPreflight: enabled })
       }),
@@ -150,6 +154,18 @@ describe('Settings > General tab', () => {
     expect(useSettingsStore.getState().setSkipWebFetchPreflight).toHaveBeenCalledWith(false)
   })
 
+  it('lets the user disable thinking mode for new sessions', () => {
+    render(<Settings />)
+
+    fireEvent.click(screen.getByText('General'))
+
+    const toggle = screen.getByLabelText('Enable thinking mode')
+    expect(toggle).toBeChecked()
+    fireEvent.click(toggle)
+
+    expect(useSettingsStore.getState().setThinkingEnabled).toHaveBeenCalledWith(false)
+  })
+
   it('keeps extension tabs available alongside the terminal tab', () => {
     render(<Settings />)
 
diff --git a/desktop/src/i18n/locales/en.ts b/desktop/src/i18n/locales/en.ts
index ca59f1e5..ef27c134 100644
--- a/desktop/src/i18n/locales/en.ts
+++ b/desktop/src/i18n/locales/en.ts
@@ -482,6 +482,10 @@ export const en = {
   'settings.general.effort.medium': 'Medium',
   'settings.general.effort.high': 'High',
   'settings.general.effort.max': 'Max',
+  'settings.general.thinkingTitle': 'Thinking Mode',
+  'settings.general.thinkingDescription': 'Controls whether new sessions start with model thinking enabled. When off, compatible providers such as DeepSeek receive an explicit non-thinking parameter.',
+  'settings.general.thinkingEnabled': 'Enable thinking mode',
+  'settings.general.thinkingHint': 'Turn this off to start new sessions with --thinking disabled; useful for DeepSeek V4 Flash/Pro and other non-thinking workflows.',
   'settings.general.webFetchPreflightTitle': 'WebFetch Preflight',
   'settings.general.webFetchPreflightDescription': 'Desktop sessions skip Claude\'s domain preflight by default to avoid false failures on third-party providers and restricted networks.',
   'settings.general.webFetchPreflightEnabled': 'Skip WebFetch domain preflight',
diff --git a/desktop/src/i18n/locales/zh.ts b/desktop/src/i18n/locales/zh.ts
index 8350dfbb..87fc06e1 100644
--- a/desktop/src/i18n/locales/zh.ts
+++ b/desktop/src/i18n/locales/zh.ts
@@ -484,6 +484,10 @@ export const zh: Record<TranslationKey, string> = {
   'settings.general.effort.medium': '中',
   'settings.general.effort.high': '高',
   'settings.general.effort.max': '最大',
+  'settings.general.thinkingTitle': '思考模式',
+  'settings.general.thinkingDescription': '控制新会话是否启用模型思考。关闭后，DeepSeek 等兼容供应商会收到显式非思考模式参数。',
+  'settings.general.thinkingEnabled': '启用思考模式',
+  'settings.general.thinkingHint': '关闭后会以 --thinking disabled 启动新会话；适合 DeepSeek V4 Flash/Pro 等需要非思考模式的模型。',
   'settings.general.webFetchPreflightTitle': 'WebFetch 预检',
   'settings.general.webFetchPreflightDescription': '桌面端默认跳过 Claude 的域名预检，避免第三方服务商或受限网络下出现误报失败。',
   'settings.general.webFetchPreflightEnabled': '跳过 WebFetch 域名预检',
diff --git a/desktop/src/pages/Settings.tsx b/desktop/src/pages/Settings.tsx
index 5ff8c76a..5aaf1a4f 100644
--- a/desktop/src/pages/Settings.tsx
+++ b/desktop/src/pages/Settings.tsx
@@ -872,6 +872,8 @@ function GeneralSettings() {
   const {
     effortLevel,
     setEffort,
+    thinkingEnabled,
+    setThinkingEnabled,
     locale,
     setLocale,
     theme,
@@ -957,6 +959,28 @@ function GeneralSettings() {
         ))}
       </div>
 
+      <div className="mt-8">
+        <h2 className="text-base font-semibold text-[var(--color-text-primary)] mb-1">{t('settings.general.thinkingTitle')}</h2>
+        <p className="text-sm text-[var(--color-text-tertiary)] mb-3">{t('settings.general.thinkingDescription')}</p>
+        <label className="flex items-start gap-3 rounded-xl border border-[var(--color-border)] bg-[var(--color-surface-container-low)] px-4 py-3 cursor-pointer hover:border-[var(--color-border-focus)] transition-colors">
+          <input
+            type="checkbox"
+            aria-label={t('settings.general.thinkingEnabled')}
+            checked={thinkingEnabled}
+            onChange={(e) => void setThinkingEnabled(e.target.checked)}
+            className="mt-0.5 h-4 w-4 rounded border-[var(--color-border)] text-[var(--color-brand)] focus:ring-[var(--color-brand)]"
+          />
+          <div className="min-w-0">
+            <div className="text-sm font-medium text-[var(--color-text-primary)]">
+              {t('settings.general.thinkingEnabled')}
+            </div>
+            <div className="text-xs text-[var(--color-text-tertiary)] mt-1 leading-5">
+              {t('settings.general.thinkingHint')}
+            </div>
+          </div>
+        </label>
+      </div>
+
       <div className="mt-8">
         <h2 className="text-base font-semibold text-[var(--color-text-primary)] mb-1">{t('settings.general.webFetchPreflightTitle')}</h2>
         <p className="text-sm text-[var(--color-text-tertiary)] mb-3">{t('settings.general.webFetchPreflightDescription')}</p>
diff --git a/desktop/src/stores/settingsStore.ts b/desktop/src/stores/settingsStore.ts
index 3613287d..ca038abe 100644
--- a/desktop/src/stores/settingsStore.ts
+++ b/desktop/src/stores/settingsStore.ts
@@ -19,6 +19,7 @@ type SettingsStore = {
   permissionMode: PermissionMode
   currentModel: ModelInfo | null
   effortLevel: EffortLevel
+  thinkingEnabled: boolean
   availableModels: ModelInfo[]
   activeProviderName: string | null
   locale: Locale
@@ -31,6 +32,7 @@ type SettingsStore = {
   setPermissionMode: (mode: PermissionMode) => Promise<void>
   setModel: (modelId: string) => Promise<void>
   setEffort: (level: EffortLevel) => Promise<void>
+  setThinkingEnabled: (enabled: boolean) => Promise<void>
   setLocale: (locale: Locale) => void
   setTheme: (theme: ThemeMode) => Promise<void>
   setSkipWebFetchPreflight: (enabled: boolean) => Promise<void>
@@ -40,6 +42,7 @@ export const useSettingsStore = create<SettingsStore>((set, get) => ({
   permissionMode: 'default',
   currentModel: null,
   effortLevel: 'medium',
+  thinkingEnabled: true,
   availableModels: [],
   activeProviderName: null,
   locale: getStoredLocale(),
@@ -66,6 +69,7 @@ export const useSettingsStore = create<SettingsStore>((set, get) => ({
         activeProviderName: modelsRes.provider?.name ?? null,
         currentModel: model,
         effortLevel: level,
+        thinkingEnabled: userSettings.alwaysThinkingEnabled !== false,
         theme,
         skipWebFetchPreflight: userSettings.skipWebFetchPreflight !== false,
         isLoading: false,
@@ -105,6 +109,16 @@ export const useSettingsStore = create<SettingsStore>((set, get) => ({
     }
   },
 
+  setThinkingEnabled: async (enabled) => {
+    const prev = get().thinkingEnabled
+    set({ thinkingEnabled: enabled })
+    try {
+      await settingsApi.updateUser({ alwaysThinkingEnabled: enabled ? undefined : false })
+    } catch {
+      set({ thinkingEnabled: prev })
+    }
+  },
+
   setLocale: (locale) => {
     set({ locale })
     try { localStorage.setItem(LOCALE_STORAGE_KEY, locale) } catch { /* noop */ }
diff --git a/desktop/src/types/settings.ts b/desktop/src/types/settings.ts
index 9b246eea..66352ef3 100644
--- a/desktop/src/types/settings.ts
+++ b/desktop/src/types/settings.ts
@@ -16,6 +16,7 @@ export type UserSettings = {
   model?: string
   modelContext?: string
   effort?: EffortLevel
+  alwaysThinkingEnabled?: boolean
   permissionMode?: PermissionMode
   theme?: ThemeMode
   skipWebFetchPreflight?: boolean
diff --git a/src/server/__tests__/conversations.test.ts b/src/server/__tests__/conversations.test.ts
index af22e877..9632588d 100644
--- a/src/server/__tests__/conversations.test.ts
+++ b/src/server/__tests__/conversations.test.ts
@@ -138,6 +138,22 @@ describe('ConversationService', () => {
     ])
   })
 
+  it('should pass disabled thinking to the CLI runtime args', () => {
+    const svc = new ConversationService()
+    expect((svc as any).getRuntimeArgs({
+      model: 'deepseek-v4-pro',
+      effort: 'medium',
+      thinking: 'disabled',
+    })).toEqual([
+      '--model',
+      'deepseek-v4-pro',
+      '--effort',
+      'medium',
+      '--thinking',
+      'disabled',
+    ])
+  })
+
   it('should return false when sending interrupt to non-existent session', () => {
     const svc = new ConversationService()
     const result = svc.sendInterrupt('no-such-session')
@@ -632,6 +648,41 @@ describe('WebSocket Chat Integration', () => {
     expect(statusMsgs[0].state).toBe('thinking')
   })
 
+  it('should start desktop sessions with disabled thinking when configured', async () => {
+    const sessionId = `chat-thinking-disabled-${crypto.randomUUID()}`
+    const originalStartSession = conversationService.startSession.bind(conversationService)
+    const startOptions: Array<{ thinking?: string; model?: string }> = []
+
+    conversationService.startSession = (async function patchedStartSession(
+      sid: string,
+      workDir: string,
+      sdkUrl: string,
+      options?: { permissionMode?: string; model?: string; effort?: string; thinking?: 'enabled' | 'adaptive' | 'disabled'; providerId?: string | null },
+    ) {
+      if (sid === sessionId) {
+        startOptions.push({ thinking: options?.thinking, model: options?.model })
+      }
+      return originalStartSession(sid, workDir, sdkUrl, options)
+    }) as typeof conversationService.startSession
+
+    try {
+      await fs.writeFile(
+        path.join(tmpDir, 'settings.json'),
+        JSON.stringify({ alwaysThinkingEnabled: false }, null, 2),
+        'utf-8',
+      )
+
+      const messages = await runTurn(sessionId, 'Hello without thinking')
+
+      expect(messages.some((m) => m.type === 'message_complete')).toBe(true)
+      expect(startOptions).toEqual([{ thinking: 'disabled', model: undefined }])
+    } finally {
+      conversationService.startSession = originalStartSession as typeof conversationService.startSession
+      conversationService.stopSession(sessionId)
+      await fs.writeFile(path.join(tmpDir, 'settings.json'), '{}\n', 'utf-8')
+    }
+  })
+
   it('should continue chat when SDK init arrives only after the first user turn', async () => {
     const messages = await withMockInitMode('on_first_user', () =>
       runTurn('chat-test-lazy-init', 'Hello after lazy init'),
@@ -901,7 +952,7 @@ describe('WebSocket Chat Integration', () => {
       sid: string,
       workDir: string,
       sdkUrl: string,
-      options?: { permissionMode?: string; model?: string; effort?: string; providerId?: string | null },
+      options?: { permissionMode?: string; model?: string; effort?: string; thinking?: 'enabled' | 'adaptive' | 'disabled'; providerId?: string | null },
     ) {
       startCalls.push({ sessionId: sid })
       return originalStartSession(sid, workDir, sdkUrl, options)
@@ -1037,7 +1088,7 @@ describe('WebSocket Chat Integration', () => {
       sid: string,
       workDir: string,
       sdkUrl: string,
-      options?: { permissionMode?: string; model?: string; effort?: string; providerId?: string | null },
+      options?: { permissionMode?: string; model?: string; effort?: string; thinking?: 'enabled' | 'adaptive' | 'disabled'; providerId?: string | null },
     ) {
       startCalls.push({ sessionId: sid, options })
       return originalStartSession(sid, workDir, sdkUrl, options)
@@ -1102,7 +1153,7 @@ describe('WebSocket Chat Integration', () => {
       sid: string,
       workDir: string,
       sdkUrl: string,
-      options?: { permissionMode?: string; model?: string; effort?: string; providerId?: string | null },
+      options?: { permissionMode?: string; model?: string; effort?: string; thinking?: 'enabled' | 'adaptive' | 'disabled'; providerId?: string | null },
     ) {
       startCalls.push({ sessionId: sid, options })
       if (startCalls.length === 1) {
@@ -1205,7 +1256,7 @@ describe('WebSocket Chat Integration', () => {
       sid: string,
       workDir: string,
       sdkUrl: string,
-      options?: { permissionMode?: string; model?: string; effort?: string; providerId?: string | null },
+      options?: { permissionMode?: string; model?: string; effort?: string; thinking?: 'enabled' | 'adaptive' | 'disabled'; providerId?: string | null },
     ) {
       startCalls.push({ sessionId: sid, options })
       return originalStartSession(sid, workDir, sdkUrl, options)
@@ -1386,7 +1437,7 @@ describe('WebSocket Chat Integration', () => {
       sid: string,
       workDir: string,
       sdkUrl: string,
-      options?: { permissionMode?: string; model?: string; effort?: string; providerId?: string | null },
+      options?: { permissionMode?: string; model?: string; effort?: string; thinking?: 'enabled' | 'adaptive' | 'disabled'; providerId?: string | null },
     ) {
       startCalls.push({ sessionId: sid, options })
       return originalStartSession(sid, workDir, sdkUrl, options)
@@ -1532,7 +1583,7 @@ describe('WebSocket Chat Integration', () => {
       sid: string,
       workDir: string,
       sdkUrl: string,
-      options?: { permissionMode?: string; model?: string; effort?: string; providerId?: string | null },
+      options?: { permissionMode?: string; model?: string; effort?: string; thinking?: 'enabled' | 'adaptive' | 'disabled'; providerId?: string | null },
     ) {
       startCalls.push({ sessionId: sid, options })
       return originalStartSession(sid, workDir, sdkUrl, options)
diff --git a/src/server/__tests__/provider-presets.test.ts b/src/server/__tests__/provider-presets.test.ts
index 360da462..ed8fff6f 100644
--- a/src/server/__tests__/provider-presets.test.ts
+++ b/src/server/__tests__/provider-presets.test.ts
@@ -80,12 +80,14 @@ describe('provider presets API', () => {
     expect(deepseek?.defaultModels.haiku).toBe('deepseek-v4-flash')
     expect(deepseek?.defaultModels.sonnet).toBe('deepseek-v4-pro')
     expect(deepseek?.defaultModels.opus).toBe('deepseek-v4-pro')
+    expect(deepseek?.defaultEnv?.CC_HAHA_SEND_DISABLED_THINKING).toBe('1')
     expect(zhipu?.defaultModels.main).toBe('glm-5.1')
     expect(zhipu?.defaultModels.haiku).toBe('glm-4.5-air')
     expect(zhipu?.defaultModels.sonnet).toBe('glm-5-turbo')
     expect(zhipu?.defaultModels.opus).toBe('glm-5.1')
     expect(kimi?.baseUrl).toBe('https://api.kimi.com/coding')
     expect(kimi?.defaultModels.main).toBe('kimi-k2.6')
+    expect(kimi?.defaultEnv?.CC_HAHA_SEND_DISABLED_THINKING).toBe('1')
     expect(minimax?.defaultModels.main).toBe('MiniMax-M2.7')
     expect(jiekouai?.baseUrl).toBe('https://api.jiekou.ai/anthropic')
     expect(jiekouai?.defaultModels.main).toBe('claude-sonnet-4-6')
@@ -118,6 +120,7 @@ describe('provider presets API', () => {
     expect(deepseek?.apiKeyUrl).toBe('https://platform.deepseek.com/api_keys')
     expect(zhipu?.apiKeyUrl).toBe('https://www.bigmodel.cn/invite?icode=d41B2qi8Z5xNwTGLNPPF3OZLO2QH3C0EBTSr%2BArzMw4%3D')
     expect(zhipu?.promoText).toContain('cc-haha')
+    expect(zhipu?.defaultEnv?.CC_HAHA_SEND_DISABLED_THINKING).toBe('1')
     expect(kimi?.apiKeyUrl).toBe('https://platform.kimi.com/console/api-keys')
     expect(minimax?.apiKeyUrl).toBe('https://platform.minimaxi.com/subscribe/token-plan?code=1TG2Cseab2&source=link')
     expect(jiekouai?.apiKeyUrl).toBe('https://jiekou.ai/referral?invited_code=OBNU3K')
diff --git a/src/server/__tests__/title-service.test.ts b/src/server/__tests__/title-service.test.ts
new file mode 100644
index 00000000..f01d2670
--- /dev/null
+++ b/src/server/__tests__/title-service.test.ts
@@ -0,0 +1,79 @@
+import { afterEach, beforeEach, describe, expect, test } from 'bun:test'
+import * as fs from 'fs/promises'
+import * as os from 'os'
+import * as path from 'path'
+import { generateTitle } from '../services/titleService.js'
+
+describe('titleService', () => {
+  let tmpDir: string
+  let originalConfigDir: string | undefined
+
+  beforeEach(async () => {
+    originalConfigDir = process.env.CLAUDE_CONFIG_DIR
+    tmpDir = await fs.mkdtemp(path.join(os.tmpdir(), 'title-service-test-'))
+    process.env.CLAUDE_CONFIG_DIR = tmpDir
+  })
+
+  afterEach(async () => {
+    restoreEnv('CLAUDE_CONFIG_DIR', originalConfigDir)
+    await fs.rm(tmpDir, { recursive: true, force: true })
+  })
+
+  test('sends disabled thinking for opted-in providers when desktop thinking is off', async () => {
+    let requestBody: Record<string, unknown> | null = null
+    const server = Bun.serve({
+      hostname: '127.0.0.1',
+      port: 0,
+      async fetch(req) {
+        requestBody = await req.json() as Record<string, unknown>
+        return Response.json({
+          content: [{ type: 'text', text: '{"title":"Trace ok"}' }],
+        })
+      },
+    })
+
+    try {
+      const providerId = 'deepseek-test'
+      await fs.mkdir(path.join(tmpDir, 'cc-haha'), { recursive: true })
+      await fs.writeFile(
+        path.join(tmpDir, 'settings.json'),
+        JSON.stringify({ alwaysThinkingEnabled: false }, null, 2),
+      )
+      await fs.writeFile(
+        path.join(tmpDir, 'cc-haha', 'providers.json'),
+        JSON.stringify({
+          activeId: providerId,
+          providers: [
+            {
+              id: providerId,
+              presetId: 'deepseek',
+              name: 'DeepSeek',
+              apiKey: 'test-key',
+              baseUrl: `http://127.0.0.1:${server.port}/anthropic`,
+              apiFormat: 'anthropic',
+              models: {
+                main: 'deepseek-v4-pro',
+                haiku: 'deepseek-v4-pro',
+                sonnet: 'deepseek-v4-pro',
+                opus: 'deepseek-v4-pro',
+              },
+            },
+          ],
+        }, null, 2),
+      )
+
+      await expect(generateTitle('请只回复 trace-ok')).resolves.toBe('Trace ok')
+      expect(requestBody?.thinking).toEqual({ type: 'disabled' })
+    } finally {
+      server.stop(true)
+    }
+  })
+})
+
+function restoreEnv(key: string, value: string | undefined) {
+  if (value === undefined) {
+    delete process.env[key]
+  } else {
+    process.env[key] = value
+  }
+}
diff --git a/src/server/config/providerPresets.json b/src/server/config/providerPresets.json
index f47c2395..d5dfe219 100644
--- a/src/server/config/providerPresets.json
+++ b/src/server/config/providerPresets.json
@@ -26,7 +26,10 @@
     },
     "needsApiKey": true,
     "websiteUrl": "https://platform.deepseek.com",
-    "apiKeyUrl": "https://platform.deepseek.com/api_keys"
+    "apiKeyUrl": "https://platform.deepseek.com/api_keys",
+    "defaultEnv": {
+      "CC_HAHA_SEND_DISABLED_THINKING": "1"
+    }
   },
   {
     "id": "zhipuglm",
@@ -42,7 +45,10 @@
     "needsApiKey": true,
     "websiteUrl": "https://open.bigmodel.cn",
     "apiKeyUrl": "https://www.bigmodel.cn/invite?icode=d41B2qi8Z5xNwTGLNPPF3OZLO2QH3C0EBTSr%2BArzMw4%3D",
-    "promoText": "智谱 GLM 为 cc-haha 用户准备了专属邀请福利，使用此链接注册后可领取新用户权益。"
+    "promoText": "智谱 GLM 为 cc-haha 用户准备了专属邀请福利，使用此链接注册后可领取新用户权益。",
+    "defaultEnv": {
+      "CC_HAHA_SEND_DISABLED_THINKING": "1"
+    }
   },
   {
     "id": "kimi",
@@ -57,7 +63,10 @@
     },
     "needsApiKey": true,
     "websiteUrl": "https://platform.moonshot.cn",
-    "apiKeyUrl": "https://platform.kimi.com/console/api-keys"
+    "apiKeyUrl": "https://platform.kimi.com/console/api-keys",
+    "defaultEnv": {
+      "CC_HAHA_SEND_DISABLED_THINKING": "1"
+    }
   },
   {
     "id": "minimax",
diff --git a/src/server/services/conversationService.ts b/src/server/services/conversationService.ts
index ff5f6155..4c55d4e8 100644
--- a/src/server/services/conversationService.ts
+++ b/src/server/services/conversationService.ts
@@ -49,6 +49,7 @@ type SessionStartOptions = {
   permissionMode?: string
   model?: string
   effort?: string
+  thinking?: 'enabled' | 'adaptive' | 'disabled'
   providerId?: string | null
 }
 
@@ -589,6 +590,10 @@ export class ConversationService {
       args.push('--effort', options.effort)
     }
 
+    if (options?.thinking) {
+      args.push('--thinking', options.thinking)
+    }
+
     return args
   }
 
@@ -615,6 +620,7 @@ export class ConversationService {
       'ANTHROPIC_DEFAULT_SONNET_MODEL_SUPPORTED_CAPABILITIES',
       'ANTHROPIC_DEFAULT_OPUS_MODEL',
       'ANTHROPIC_DEFAULT_OPUS_MODEL_SUPPORTED_CAPABILITIES',
+      'CC_HAHA_SEND_DISABLED_THINKING',
     ] as const
 
     const cleanEnv = { ...process.env }
@@ -738,6 +744,7 @@ export class ConversationService {
         'ANTHROPIC_DEFAULT_SONNET_MODEL_SUPPORTED_CAPABILITIES',
         'ANTHROPIC_DEFAULT_OPUS_MODEL',
         'ANTHROPIC_DEFAULT_OPUS_MODEL_SUPPORTED_CAPABILITIES',
+        'CC_HAHA_SEND_DISABLED_THINKING',
       ].some((key) => typeof env[key] === 'string' && env[key]!.trim().length > 0)
     } catch {
       return false
diff --git a/src/server/services/titleService.ts b/src/server/services/titleService.ts
index 5a99f356..fd319ae4 100644
--- a/src/server/services/titleService.ts
+++ b/src/server/services/titleService.ts
@@ -7,7 +7,10 @@
  */
 
 import { ProviderService } from './providerService.js'
+import { SettingsService } from './settingsService.js'
 import { sessionService } from './sessionService.js'
+import { PROVIDER_PRESETS } from '../config/providerPresets.js'
+import { isEnvTruthy } from '../../utils/envUtils.js'
 
 const TITLE_MAX_LEN = 50
 
@@ -69,6 +72,7 @@ export async function generateTitle(
 
     const model = resolvedProvider.models.haiku || resolvedProvider.models.main
     const url = `${resolvedProvider.baseUrl.replace(/\/+$/, '')}/v1/messages`
+    const shouldDisableThinking = await shouldDisableThinkingForTitle(resolvedProvider.presetId)
 
     const response = await fetch(url, {
       method: 'POST',
@@ -82,6 +86,7 @@ export async function generateTitle(
         max_tokens: 100,
         system: TITLE_SYSTEM_PROMPT,
         messages: [{ role: 'user', content: trimmed.slice(0, 2000) }],
+        ...(shouldDisableThinking && { thinking: { type: 'disabled' } }),
       }),
       signal: AbortSignal.timeout(15_000),
     })
@@ -108,6 +113,14 @@ export async function generateTitle(
   }
 }
 
+async function shouldDisableThinkingForTitle(presetId: string): Promise<boolean> {
+  const settings = await new SettingsService().getUserSettings()
+  if (settings.alwaysThinkingEnabled !== false) return false
+
+  const presetEnv = PROVIDER_PRESETS.find((preset) => preset.id === presetId)?.defaultEnv
+  return isEnvTruthy(presetEnv?.CC_HAHA_SEND_DISABLED_THINKING)
+}
+
 /**
  * Persist an AI-generated title to the session's JSONL file.
  */
diff --git a/src/server/ws/handler.ts b/src/server/ws/handler.ts
index 1c5ce276..5656e809 100644
--- a/src/server/ws/handler.ts
+++ b/src/server/ws/handler.ts
@@ -1236,6 +1236,7 @@ type RuntimeSettings = {
   permissionMode?: string
   model?: string
   effort?: string
+  thinking?: 'disabled'
   providerId?: string | null
 }
 
@@ -1259,11 +1260,13 @@ async function getRuntimeSettings(sessionId?: string): Promise<RuntimeSettings>
       typeof userSettings.effort === 'string' && userSettings.effort.trim()
         ? userSettings.effort
         : undefined
+    const thinking = resolveDesktopThinkingMode(userSettings)
 
     return {
       permissionMode: await settingsService.getPermissionMode().catch(() => undefined),
       model: runtimeOverride.modelId,
       effort,
+      thinking,
       providerId: runtimeOverride.providerId,
     }
   }
@@ -1294,6 +1297,7 @@ async function getDefaultRuntimeSettings(): Promise<RuntimeSettings> {
     typeof userSettings.effort === 'string' && userSettings.effort.trim()
       ? userSettings.effort
       : undefined
+  const thinking = resolveDesktopThinkingMode(userSettings)
 
   let model: string | undefined
   if (resolvedActiveId) {
@@ -1320,10 +1324,17 @@ async function getDefaultRuntimeSettings(): Promise<RuntimeSettings> {
     permissionMode: await settingsService.getPermissionMode().catch(() => undefined),
     model,
     effort,
+    thinking,
     providerId: resolvedActiveId,
   }
 }
 
+function resolveDesktopThinkingMode(
+  settings: Record<string, unknown>,
+): 'disabled' | undefined {
+  return settings.alwaysThinkingEnabled === false ? 'disabled' : undefined
+}
+
 async function buildSessionStartupDiagnosticMessage(
   sessionId: string,
   cause: string,
diff --git a/src/services/api/claude.ts b/src/services/api/claude.ts
index 89a6e661..3e567955 100644
--- a/src/services/api/claude.ts
+++ b/src/services/api/claude.ts
@@ -181,6 +181,7 @@ import { endQueryProfile, queryCheckpoint } from 'src/utils/queryProfiler.js'
 import {
   modelSupportsAdaptiveThinking,
   modelSupportsThinking,
+  shouldSendExplicitDisabledThinking,
   type ThinkingConfig,
 } from 'src/utils/thinking.js'
 import {
@@ -1627,6 +1628,10 @@ async function* queryModel(
           type: 'enabled',
         } satisfies BetaMessageStreamParams['thinking']
       }
+    } else if (shouldSendExplicitDisabledThinking()) {
+      thinking = {
+        type: 'disabled',
+      } as unknown as BetaMessageStreamParams['thinking']
     }
 
     // Get API context management strategies if enabled
diff --git a/src/utils/__tests__/thinking.test.ts b/src/utils/__tests__/thinking.test.ts
index 949504f6..397a6760 100644
--- a/src/utils/__tests__/thinking.test.ts
+++ b/src/utils/__tests__/thinking.test.ts
@@ -1,6 +1,11 @@
 import { afterEach, beforeEach, describe, expect, test } from 'bun:test'
 import { get3PModelCapabilityOverride } from '../model/modelSupportOverrides.js'
-import { modelSupportsAdaptiveThinking, modelSupportsThinking } from '../thinking.js'
+import { resolveSideQueryThinkingConfig } from '../sideQuery.js'
+import {
+  modelSupportsAdaptiveThinking,
+  modelSupportsThinking,
+  shouldSendExplicitDisabledThinking,
+} from '../thinking.js'
 
 describe('provider-aware thinking support', () => {
   let originalBaseUrl: string | undefined
@@ -9,6 +14,7 @@ describe('provider-aware thinking support', () => {
   let originalBedrock: string | undefined
   let originalVertex: string | undefined
   let originalFoundry: string | undefined
+  let originalExplicitDisabledThinking: string | undefined
 
   beforeEach(() => {
     originalBaseUrl = process.env.ANTHROPIC_BASE_URL
@@ -17,6 +23,7 @@ describe('provider-aware thinking support', () => {
     originalBedrock = process.env.CLAUDE_CODE_USE_BEDROCK
     originalVertex = process.env.CLAUDE_CODE_USE_VERTEX
     originalFoundry = process.env.CLAUDE_CODE_USE_FOUNDRY
+    originalExplicitDisabledThinking = process.env.CC_HAHA_SEND_DISABLED_THINKING
 
     delete process.env.CLAUDE_CODE_USE_BEDROCK
     delete process.env.CLAUDE_CODE_USE_VERTEX
@@ -30,6 +37,7 @@ describe('provider-aware thinking support', () => {
     restoreEnv('CLAUDE_CODE_USE_BEDROCK', originalBedrock)
     restoreEnv('CLAUDE_CODE_USE_VERTEX', originalVertex)
     restoreEnv('CLAUDE_CODE_USE_FOUNDRY', originalFoundry)
+    restoreEnv('CC_HAHA_SEND_DISABLED_THINKING', originalExplicitDisabledThinking)
     clearCapabilityCache()
   })
 
@@ -60,6 +68,24 @@ describe('provider-aware thinking support', () => {
     expect(modelSupportsThinking('claude-sonnet-4-6')).toBe(true)
     expect(modelSupportsAdaptiveThinking('claude-sonnet-4-6')).toBe(true)
   })
+
+  test('only sends explicit disabled thinking when the provider opts in', () => {
+    delete process.env.CC_HAHA_SEND_DISABLED_THINKING
+    expect(shouldSendExplicitDisabledThinking()).toBe(false)
+
+    process.env.CC_HAHA_SEND_DISABLED_THINKING = '1'
+    expect(shouldSendExplicitDisabledThinking()).toBe(true)
+  })
+
+  test('side queries inherit explicit disabled thinking for opted-in providers', () => {
+    delete process.env.CC_HAHA_SEND_DISABLED_THINKING
+    expect(resolveSideQueryThinkingConfig(undefined, 1024)).toBeUndefined()
+
+    process.env.CC_HAHA_SEND_DISABLED_THINKING = '1'
+    expect(resolveSideQueryThinkingConfig(undefined, 1024)).toEqual({ type: 'disabled' })
+    expect(resolveSideQueryThinkingConfig(false, 1024)).toEqual({ type: 'disabled' })
+    expect(resolveSideQueryThinkingConfig(256, 1024)).toEqual({ type: 'enabled', budget_tokens: 256 })
+  })
 })
 
 function restoreEnv(key: string, value: string | undefined) {
diff --git a/src/utils/sideQuery.ts b/src/utils/sideQuery.ts
index 4e6d4d73..e01e5b26 100644
--- a/src/utils/sideQuery.ts
+++ b/src/utils/sideQuery.ts
@@ -17,6 +17,7 @@ import { getAnthropicClient } from '../services/api/client.js'
 import { getModelBetas, modelSupportsStructuredOutputs } from './betas.js'
 import { computeFingerprint } from './fingerprint.js'
 import { normalizeModelStringForAPI } from './model/model.js'
+import { shouldSendExplicitDisabledThinking } from './thinking.js'
 
 type MessageParam = Anthropic.MessageParam
 type TextBlockParam = Anthropic.TextBlockParam
@@ -166,15 +167,7 @@ export async function sideQuery(opts: SideQueryOptions): Promise<BetaMessage> {
         : []),
   ].filter((block): block is TextBlockParam => block !== null)
 
-  let thinkingConfig: BetaThinkingConfigParam | undefined
-  if (thinking === false) {
-    thinkingConfig = { type: 'disabled' }
-  } else if (thinking !== undefined) {
-    thinkingConfig = {
-      type: 'enabled',
-      budget_tokens: Math.min(thinking, max_tokens - 1),
-    }
-  }
+  const thinkingConfig = resolveSideQueryThinkingConfig(thinking, max_tokens)
 
   const normalizedModel = normalizeModelStringForAPI(model)
   const start = Date.now()
@@ -220,3 +213,22 @@ export async function sideQuery(opts: SideQueryOptions): Promise<BetaMessage> {
 
   return response
 }
+
+export function resolveSideQueryThinkingConfig(
+  thinking: SideQueryOptions['thinking'],
+  maxTokens: number,
+): BetaThinkingConfigParam | undefined {
+  if (
+    thinking === false ||
+    (thinking === undefined && shouldSendExplicitDisabledThinking())
+  ) {
+    return { type: 'disabled' }
+  }
+  if (thinking !== undefined) {
+    return {
+      type: 'enabled',
+      budget_tokens: Math.min(thinking, maxTokens - 1),
+    }
+  }
+  return undefined
+}
diff --git a/src/utils/thinking.ts b/src/utils/thinking.ts
index 506c3692..b60ce573 100644
--- a/src/utils/thinking.ts
+++ b/src/utils/thinking.ts
@@ -6,6 +6,7 @@ import { getCanonicalName } from './model/model.js'
 import { get3PModelCapabilityOverride } from './model/modelSupportOverrides.js'
 import { getAPIProvider, isFirstPartyAnthropicBaseUrl } from './model/providers.js'
 import { getSettingsWithErrors } from './settings/settings.js'
+import { isEnvTruthy } from './envUtils.js'
 
 export type ThinkingConfig =
   | { type: 'adaptive' }
@@ -170,3 +171,7 @@ export function shouldEnableThinkingByDefault(): boolean {
   // Enable thinking by default unless explicitly disabled.
   return true
 }
+
+export function shouldSendExplicitDisabledThinking(): boolean {
+  return isEnvTruthy(process.env.CC_HAHA_SEND_DISABLED_THINKING)
+}