mamoe/mirai

mirai is an open source library, written mainly in Kotlin, for building bots that talk to QQ, the very popular Chinese chat service. The README describes it as a high-efficiency bot library that runs across platforms and implements the QQ Android client protocol, which means a program using mirai can sign in as a QQ user and read or send messages the way the mobile app does. The project name is a reference to characters from Japanese anime and music, and the logo art was contributed by a community artist. The README opens with a strong statement of intent. The project is free, fully open source, maintained by the community, and meant for learning and entertainment only. The authors say it must not be used for illegal purposes, and they also say it should not be used commercially. The license is AGPLv3, and the README warns that any project that talks to mirai, even through an HTTP API or cross-process bridge, must also be open source under AGPLv3. A collapsible section lists what the library can do. On the messaging side it supports text, native and shop emoji, the nudge action, images and custom stickers, rich XML and JSON messages, long messages of up to 5000 characters with 50 images, quote replies, forwarded message bundles, message recall, mentions of one or all group members, voice, and flash photos. For group management it handles member lists, permissions, mutes, announcements, group settings, and join requests. For friends it handles the full friend list and friend requests. The README also lists what mirai will not implement: anything money related, sensitive actions like sending friend requests on its own, and account security operations like extracting login tokens.