数据存储（核心承诺）
您导入的学习资料——包括书籍/资料、章节、AI 生成的题目、练习记录、错题本与掌握度——
仅保存在您的设备本地。我们的服务器不会存储这些内容。
- 我们的服务器只保存：您的账号登录信息，以及匿名的功能使用统计（绝不包含您的资料正文）。
- 更换设备时，请使用「设备间直接传输」（扫码 + 同一局域网）自行将资料从旧手机迁移到新手机。
由于资料只在本地，若设备丢失或被清除且未提前迁移，该资料将无法找回——我们的服务器没有副本可供恢复。
- 一个账号同一时间只能在一台设备登录；在新设备登录后，旧设备会自动退出登录。
关于 AI
使用内置 AI 生成题目时，仅本次生成所必需的文本会临时发送至我们的服务器用于调用模型，处理后即丢弃、不作保存。
使用您自己添加的模型时，请求与密钥直接从您的设备发送至您选择的服务商，我们不经手、不留存您的密钥或内容。
Data Storage (core promise)
The study materials you import — books/sources, chapters, AI-generated questions, practice records,
mistake book, and mastery — are stored only on your device. Our servers do not store this content.
- Our servers keep only: your account login, and anonymous feature-usage analytics (never the text of your materials).
- To change devices, use device-to-device transfer (QR + same local network) to move your data
yourself. Because the data lives only on your device, if a device is lost or wiped before you transfer,
that data cannot be recovered — our servers hold no copy.
- An account may be signed in on only one device at a time; signing in on a new device automatically signs out the old one.
About AI
When you use the built-in AI to generate questions, only the text needed for that
generation is sent transiently to our server to call the model, and is then discarded — not stored.
When you use your own added model, the request and key go directly from your device to
the provider you chose; we never handle or retain your key or content.