diff --git a/packages/http-routes/src/routes/web/cache.test.ts b/packages/http-routes/src/routes/web/cache.test.ts
index fb8f7160..11cd0e08 100644
--- a/packages/http-routes/src/routes/web/cache.test.ts
+++ b/packages/http-routes/src/routes/web/cache.test.ts
@@ -1,11 +1,14 @@
 import { describe, it } from 'node:test'
 import assert from 'node:assert/strict'
+import fs from 'node:fs'
+import os from 'node:os'
+import path from 'node:path'
 import Fastify from 'fastify'
 import type { PathProvider } from '@openchatlab/core'
 import type { HttpRouteContext } from '../../context'
 import { registerCacheRoutes } from './cache'
 
-function createPathProvider(): PathProvider {
+function createPathProvider(overrides: Partial<PathProvider> = {}): PathProvider {
   return {
     getSystemDir: () => '/tmp/chatlab-test',
     getUserDataDir: () => '/tmp/chatlab-test/data',
@@ -16,9 +19,15 @@ function createPathProvider(): PathProvider {
     getTempDir: () => '/tmp/chatlab-test/temp',
     getLogsDir: () => '/tmp/chatlab-test/logs',
     getDownloadsDir: () => '/tmp/chatlab-test/downloads',
+    ...overrides,
   }
 }
 
+function makeTempDir(): string {
+  const baseDir = fs.existsSync('/private/tmp') ? '/private/tmp' : os.tmpdir()
+  return fs.mkdtempSync(path.join(baseDir, 'chatlab-cache-routes-'))
+}
+
 describe('registerCacheRoutes data directory routes', () => {
   it('returns data directory capability and pending migration', async () => {
     const app = Fastify()
@@ -45,6 +54,7 @@ describe('registerCacheRoutes data directory routes', () => {
       defaultPath: '/tmp/chatlab-test/default-data',
       isCustom: true,
       canSetDataDir: true,
+      hasLegacyDataAtDefaultDir: false,
       pendingMigration: {
         from: '/tmp/chatlab-test/data',
         to: '/tmp/chatlab-test/new-data',
@@ -55,6 +65,42 @@ describe('registerCacheRoutes data directory routes', () => {
     await app.close()
   })
 
+  it('reports legacy data at default directory only when default databases contain db files', async () => {
+    const root = makeTempDir()
+    const currentDir = path.join(root, 'custom-data')
+    const defaultDir = path.join(root, 'default-data')
+    fs.mkdirSync(path.join(defaultDir, 'databases'), { recursive: true })
+    fs.writeFileSync(path.join(defaultDir, '.chatlab'), 'ChatLab Data Directory')
+
+    const appWithoutDb = Fastify()
+    registerCacheRoutes(appWithoutDb, {
+      pathProvider: createPathProvider({ getUserDataDir: () => currentDir }),
+      defaultUserDataDir: defaultDir,
+      isCustomDataDir: true,
+    } as unknown as HttpRouteContext)
+    await appWithoutDb.ready()
+
+    const emptyResponse = await appWithoutDb.inject({ method: 'GET', url: '/_web/cache/data-dir' })
+    assert.equal(emptyResponse.statusCode, 200)
+    assert.equal(emptyResponse.json().hasLegacyDataAtDefaultDir, false)
+    await appWithoutDb.close()
+
+    fs.writeFileSync(path.join(defaultDir, 'databases', 'legacy.db'), 'sqlite')
+
+    const appWithDb = Fastify()
+    registerCacheRoutes(appWithDb, {
+      pathProvider: createPathProvider({ getUserDataDir: () => currentDir }),
+      defaultUserDataDir: defaultDir,
+      isCustomDataDir: true,
+    } as unknown as HttpRouteContext)
+    await appWithDb.ready()
+
+    const response = await appWithDb.inject({ method: 'GET', url: '/_web/cache/data-dir' })
+    assert.equal(response.statusCode, 200)
+    assert.equal(response.json().hasLegacyDataAtDefaultDir, true)
+    await appWithDb.close()
+  })
+
   it('delegates data directory changes to context callback', async () => {
     const app = Fastify()
     const calls: Array<{ path: string | null; migrate?: boolean }> = []
diff --git a/packages/http-routes/src/routes/web/cache.ts b/packages/http-routes/src/routes/web/cache.ts
index 24c62dcc..8d2443f0 100644
--- a/packages/http-routes/src/routes/web/cache.ts
+++ b/packages/http-routes/src/routes/web/cache.ts
@@ -43,6 +43,17 @@ async function getFileCount(dirPath: string): Promise<number> {
   return count
 }
 
+function hasChatLabDatabases(dirPath: string): boolean {
+  try {
+    const markerPath = path.join(dirPath, '.chatlab')
+    const dbDir = path.join(dirPath, 'databases')
+    if (!fs.existsSync(markerPath) || !fs.existsSync(dbDir)) return false
+    return fs.readdirSync(dbDir).some((file) => file.endsWith('.db'))
+  } catch {
+    return false
+  }
+}
+
 export function registerCacheRoutes(server: FastifyInstance, ctx: HttpRouteContext): void {
   const pp = ctx.pathProvider
   const downloadsDir = ctx.downloadsDir ?? pp.getDownloadsDir()
@@ -128,6 +139,10 @@ export function registerCacheRoutes(server: FastifyInstance, ctx: HttpRouteConte
       defaultPath: ctx.defaultUserDataDir,
       isCustom: ctx.isCustomDataDir ?? false,
       canSetDataDir: ctx.canSetDataDir ?? Boolean(ctx.setDataDir),
+      hasLegacyDataAtDefaultDir:
+        Boolean(ctx.defaultUserDataDir) &&
+        path.resolve(pp.getUserDataDir()) !== path.resolve(ctx.defaultUserDataDir ?? '') &&
+        hasChatLabDatabases(ctx.defaultUserDataDir ?? ''),
       pendingMigration: pending
         ? {
             from: pending.from,
diff --git a/src/components/common/Settings/DataStorage/StorageManageSection.vue b/src/components/common/Settings/DataStorage/StorageManageSection.vue
index f4988ae4..2f87abeb 100644
--- a/src/components/common/Settings/DataStorage/StorageManageSection.vue
+++ b/src/components/common/Settings/DataStorage/StorageManageSection.vue
@@ -20,6 +20,7 @@ const clearingId = ref<string | null>(null)
 const dataDir = ref('')
 const dataDirInput = ref('')
 const defaultDataDir = ref('')
+const hasLegacyDataAtDefaultDir = ref(false)
 const isCustomDataDir = ref(false)
 const canSetDataDir = ref(false)
 const isUpdatingDataDir = ref(false)
@@ -72,6 +73,7 @@ const canMigrateToDefault = computed(() => {
     dataDir.value &&
     defaultDataDir.value &&
     dataDir.value !== defaultDataDir.value &&
+    hasLegacyDataAtDefaultDir.value &&
     !isMigrateHintIgnored.value
   )
 })
@@ -95,6 +97,7 @@ async function loadDataDir() {
     dataDir.value = info.path
     dataDirInput.value = info.pendingMigration?.to || info.path
     defaultDataDir.value = info.defaultPath || ''
+    hasLegacyDataAtDefaultDir.value = Boolean(info.hasLegacyDataAtDefaultDir)
     isCustomDataDir.value = info.isCustom
     canSetDataDir.value = IS_ELECTRON || Boolean(info.canSetDataDir)
     updateMigrateHintIgnored()
diff --git a/src/services/cache/types.ts b/src/services/cache/types.ts
index c0d52544..a008c5d6 100644
--- a/src/services/cache/types.ts
+++ b/src/services/cache/types.ts
@@ -21,6 +21,7 @@ export interface DataDirInfo {
   defaultPath?: string
   isCustom: boolean
   canSetDataDir?: boolean
+  hasLegacyDataAtDefaultDir?: boolean
   pendingMigration?: {
     from: string
     to: string