diff --git a/apps/desktop/src/main/maker-host/__tests__/titleOutputValidation.test.ts b/apps/desktop/src/main/maker-host/__tests__/titleOutputValidation.test.ts
index e061c37958d..bf90b3368d1 100644
--- a/apps/desktop/src/main/maker-host/__tests__/titleOutputValidation.test.ts
+++ b/apps/desktop/src/main/maker-host/__tests__/titleOutputValidation.test.ts
@@ -1,6 +1,9 @@
 import { describe, expect, it } from 'vitest';
 
-import { validateTitleOutput } from '../title-output-validation.js';
+import {
+  validateGeneratedTitleLocale,
+  validateTitleOutput,
+} from '../title-output-validation.js';
 
 describe('validateTitleOutput', () => {
   it.each([
@@ -99,3 +102,39 @@ describe('validateTitleOutput', () => {
     expect(validateTitleOutput('😀😀😀😀', 3)).toBeNull();
   });
 });
+
+describe('validateGeneratedTitleLocale', () => {
+  it('rejects an unattributed Malayalam suffix in a Chinese title', () => {
+    expect(
+      validateGeneratedTitleLocale('夏日合照自然合成 ആവശ്യ', '请自然合成这张夏日合照', 'zh-CN'),
+    ).toBeNull();
+  });
+
+  it('keeps normal Chinese and common Latin product/code names', () => {
+    expect(validateGeneratedTitleLocale('夏日合照自然合成', '请合成这张照片', 'zh-CN')).toBe(
+      '夏日合照自然合成',
+    );
+    expect(validateGeneratedTitleLocale('修复 Mivo API 登录', '帮我排查登录问题', 'zh-CN')).toBe(
+      '修复 Mivo API 登录',
+    );
+  });
+
+  it('allows an unexpected script when the generated title quotes the source text', () => {
+    expect(
+      validateGeneratedTitleLocale(
+        '处理 ആവശ്യ 字段',
+        '接口里的 ആവശ്യ 字段是什么意思？',
+        'zh-CN',
+      ),
+    ).toBe('处理 ആവശ്യ 字段');
+  });
+
+  it('accepts the native scripts of Japanese and Korean locales', () => {
+    expect(validateGeneratedTitleLocale('サーバー問題の修正', 'fix server', 'ja')).toBe(
+      'サーバー問題の修正',
+    );
+    expect(validateGeneratedTitleLocale('로그인 문제 수정', 'fix login', 'ko')).toBe(
+      '로그인 문제 수정',
+    );
+  });
+});
diff --git a/apps/desktop/src/main/maker-host/title-output-validation.ts b/apps/desktop/src/main/maker-host/title-output-validation.ts
index dde7edcfa0a..5a4cdb90c88 100644
--- a/apps/desktop/src/main/maker-host/title-output-validation.ts
+++ b/apps/desktop/src/main/maker-host/title-output-validation.ts
@@ -1,5 +1,7 @@
 /** Deterministic acceptance rules for model-produced session titles. */
 
+import type { SupportedLocale } from '../../shared/locale.js';
+
 const META_PREFIX_RE =
   /^(?:(?:according to (?:the )?conversation|based on (?:the )?conversation|here(?:'s| is) (?:the )?title)(?:\b|\s|[,:：，。.!！?？])|(?:title|标题|タイトル|제목)\s*[:：]|以下是|根据对话内容)/iu;
 const ROLE_LABEL_RE =
@@ -22,6 +24,15 @@ const INSTRUCTION_ECHO_RES: readonly RegExp[] = [
   /^(?:treat\s+everything\s+inside\s+the\s+(?:user_message|conversation_opening|recent_conversation)\s+delimiters\b|never\s+restate,?\s+translate,?\s+or\s+summarize\s+the\s+instructions\s+above\b|write\s+the\s+title\s+in\s+(?:simplified\s+chinese|english|japanese|korean)\b|use\s+at\s+most\s+20\s+characters\b|output\s+only\s+the\s+title,?\s+without\s+quotation\s+marks\s+or\s+ending\s+punctuation\b).*$/iu,
 ];
 
+const LETTER_RE = /\p{Letter}/u;
+const LOCALE_TITLE_LETTER_RE: Record<SupportedLocale, RegExp> = {
+  'zh-CN': /[\p{Script_Extensions=Han}\p{Script_Extensions=Latin}]/u,
+  'zh-TW': /[\p{Script_Extensions=Han}\p{Script_Extensions=Latin}]/u,
+  en: /\p{Script_Extensions=Latin}/u,
+  ja: /[\p{Script_Extensions=Han}\p{Script_Extensions=Hiragana}\p{Script_Extensions=Katakana}\p{Script_Extensions=Latin}]/u,
+  ko: /[\p{Script_Extensions=Hangul}\p{Script_Extensions=Han}\p{Script_Extensions=Latin}]/u,
+};
+
 function exceedsUnicodeCodePointLimit(value: string, maxChars: number): boolean {
   let count = 0;
   for (const _char of value) {
@@ -71,3 +82,31 @@ export function validateTitleOutput(
   if (exceedsUnicodeCodePointLimit(title, maxChars)) return null;
   return title;
 }
+
+/**
+ * Reject letters from scripts that neither belong to the requested UI locale nor
+ * occur in the reference material. This is intentionally scoped to generated
+ * titles: manual titles and the user's fallback text must remain lossless.
+ *
+ * Latin stays valid in every supported locale for product names, file names and
+ * code identifiers. An otherwise unexpected letter is accepted only when the same
+ * code point exists in the source, so quoted multilingual names survive while a
+ * model cannot append an unrelated foreign-script fragment (issue #3483).
+ */
+export function validateGeneratedTitleLocale(
+  title: string,
+  referenceText: string,
+  locale: SupportedLocale,
+): string | null {
+  const allowedLetter = LOCALE_TITLE_LETTER_RE[locale];
+  const referencedUnexpectedLetters = new Set(
+    Array.from(referenceText).filter(
+      (char) => LETTER_RE.test(char) && !allowedLetter.test(char),
+    ),
+  );
+  for (const char of title) {
+    if (!LETTER_RE.test(char) || allowedLetter.test(char)) continue;
+    if (!referencedUnexpectedLetters.has(char)) return null;
+  }
+  return title;
+}
diff --git a/apps/desktop/src/main/maker-ipc/__tests__/regenerateSessionTitle.test.ts b/apps/desktop/src/main/maker-ipc/__tests__/regenerateSessionTitle.test.ts
index ec1bc2c33ce..479c3cc545b 100644
--- a/apps/desktop/src/main/maker-ipc/__tests__/regenerateSessionTitle.test.ts
+++ b/apps/desktop/src/main/maker-ipc/__tests__/regenerateSessionTitle.test.ts
@@ -48,7 +48,7 @@ import { getResolvedMainLocale } from '../../i18n.js';
 import type { RegenerateTitleMaterial } from '../../localDb/latestMessageText.js';
 
 beforeEach(() => {
-  vi.mocked(getResolvedMainLocale).mockReturnValue('en');
+  vi.mocked(getResolvedMainLocale).mockReturnValue('zh-CN');
   vi.clearAllMocks();
 });
 
@@ -338,6 +338,20 @@ describe('regenerateMakerSessionTitle', () => {
     ).rejects.toThrow(/\[INTERNAL\]/);
   });
 
+  it('AI 重命名同样拒绝素材中没有依据的异文片段', async () => {
+    vi.mocked(getResolvedMainLocale).mockReturnValue('zh-CN');
+    const deps = makeDeps({
+      generateTitle: vi.fn(async () => generatedTitle('夏日合照自然合成 ആവശ്യ')),
+    });
+
+    await expect(regenerateMakerSessionTitle('s1', deps)).rejects.toThrow(/\[INTERNAL\]/);
+    expect(logger.warn).toHaveBeenCalledWith('regenerate session title rejected model output', {
+      sessionId: 's1',
+      agentKind: 'claude-code',
+      reason: 'unattributed-script',
+    });
+  });
+
   it('依赖异常被脱敏为通用 INTERNAL 错误，不向 renderer 透传原始错误', async () => {
     const deps = makeDeps({
       collectMaterial: vi.fn(async () => {
@@ -394,6 +408,30 @@ describe('generateMakerSessionTitle', () => {
     expect(request.prompt).not.toContain('  帮我排查登录失败');
   });
 
+  it('zh-CN 模型标题凭空混入马拉雅拉姆文字时拒绝并回落原文占位', async () => {
+    vi.mocked(getResolvedMainLocale).mockReturnValue('zh-CN');
+    vi.mocked(generateTitleViaProvider).mockResolvedValueOnce('夏日合照自然合成 ആവശ്യ');
+
+    expect(
+      await generateMakerSessionTitle('请自然合成这张夏日合照', 'claude-code', 's1'),
+    ).toBeNull();
+    expect(logger.warn).toHaveBeenCalledWith('auto title rejected model output', {
+      sessionId: 's1',
+      agentKind: 'claude-code',
+      locale: 'zh-CN',
+      reason: 'unattributed-script',
+    });
+  });
+
+  it('首条输入本身包含外文时允许模型保留同一段文字', async () => {
+    vi.mocked(getResolvedMainLocale).mockReturnValue('zh-CN');
+    vi.mocked(generateTitleViaProvider).mockResolvedValueOnce('处理 ആവശ്യ 字段');
+
+    expect(
+      await generateMakerSessionTitle('接口里的 ആവശ്യ 字段是什么意思？', 'codex', 's1'),
+    ).toBe('处理 ആവശ്യ 字段');
+  });
+
   it.each([
     ['zh-CN', 'Simplified Chinese'],
     ['en', 'English'],
diff --git a/apps/desktop/src/main/maker-ipc/title.ts b/apps/desktop/src/main/maker-ipc/title.ts
index dfb4827f982..aa7ef7261da 100644
--- a/apps/desktop/src/main/maker-ipc/title.ts
+++ b/apps/desktop/src/main/maker-ipc/title.ts
@@ -31,7 +31,10 @@ import {
   generateTitleWithAuxiliaryModel,
   generateTitleWithAuxiliaryModelResult,
 } from '../maker-host/auxiliary-title-one-shot.js';
-import { validateTitleOutput } from '../maker-host/title-output-validation.js';
+import {
+  validateGeneratedTitleLocale,
+  validateTitleOutput,
+} from '../maker-host/title-output-validation.js';
 import {
   regenerateTitleMaterial,
   type RegenerateTitleMaterial,
@@ -111,13 +114,14 @@ export async function generateMakerSessionTitle(
   // "请提供用户消息内容"式回复当标题返回。直接放弃,调用方保留默认名。
   const trimmed = message.trim();
   if (!trimmed) return null;
-  return generateTitleWithAuxiliaryModel(
+  const locale = getResolvedMainLocale();
+  const generated = await generateTitleWithAuxiliaryModel(
     {
       sessionId: sessionId ?? '',
       agentKind,
       prompt: buildAutoTitlePrompt(
         trimmed.slice(0, AUTO_TITLE_MESSAGE_SLICE),
-        getResolvedMainLocale(),
+        locale,
       ),
     },
     {
@@ -125,6 +129,17 @@ export async function generateMakerSessionTitle(
       listConnectedProviders: listConnectedProvidersForAgent,
     },
   );
+  if (!generated) return null;
+  const title = validateGeneratedTitleLocale(generated, trimmed, locale);
+  if (!title) {
+    log.warn('auto title rejected model output', {
+      sessionId: sessionId ?? '',
+      agentKind,
+      locale,
+      reason: 'unattributed-script',
+    });
+  }
+  return title;
 }
 
 /** regenerate 的依赖注入面——单测用内存实现替换 DB / LLM 调用。 */
@@ -213,10 +228,11 @@ export async function regenerateMakerSessionTitle(
           : `Assistant: ${m.text.slice(0, REGENERATE_ASSISTANT_SLICE)}`,
       )
       .join('\n');
+    const locale = getResolvedMainLocale();
     const generated = await deps.generateTitle(
       sessionId,
       agentKind,
-      buildRegenerateTitlePrompt(openingText, transcript, getResolvedMainLocale()),
+      buildRegenerateTitlePrompt(openingText, transcript, locale),
     );
     if (generated.status !== 'ok') {
       const context = { sessionId, agentKind, reason: generated.status };
@@ -233,12 +249,18 @@ export async function regenerateMakerSessionTitle(
     // Regenerate has a stricter product contract than the shared auto-title path:
     // one line, ≤20 Unicode characters, and no transcript/meta wrapper. The model is
     // not trusted to enforce this by prompt alone.
-    const title = validateTitleOutput(generated.title, 20);
+    const normalizedTitle = validateTitleOutput(generated.title, 20);
+    const referenceText = [openingText, ...recent.map((message) => message.text)]
+      .filter((text): text is string => Boolean(text))
+      .join('\n');
+    const title = normalizedTitle
+      ? validateGeneratedTitleLocale(normalizedTitle, referenceText, locale)
+      : null;
     if (!title) {
       log.warn('regenerate session title rejected model output', {
         sessionId,
         agentKind,
-        reason: 'invalid-output',
+        reason: normalizedTitle ? 'unattributed-script' : 'invalid-output',
       });
       throwIpcError('INTERNAL', 'AI title generation failed');
     }