Bub

Bub is a small, open source Python runtime for building AI agents that work in shared environments. It began in group chats, where several humans and agents had to share one conversation, so it avoids hidden state and opaque memory. It builds on the agents.md convention and Agent Skills, and starts as a working agent that can be customised in how it thinks, remembers and connects. The runtime is aimed at developers who want full control over an agent's behaviour without forking a framework. Every stage of a turn, from resolving the session and loading state through building the prompt, calling the model, rendering and saving, to dispatching the reply, is a pluggy hook. The built in behaviour is itself just a plugin, and later registered plugins override earlier ones, so any stage can be replaced, including swapping in any model client or API. Context is rebuilt from append only tape records rather than accumulated session state, which makes runs easy to inspect, replay and hand off. The same inbound pipeline drives the command line, Telegram and custom channels, and humans and agents share one operator model with the same boundaries and evidence trail. It installs with a one line script on macOS, Linux or Windows and offers interactive chat, one shot tasks and a gateway mode that listens on channels. Bub is free and released under the Apache 2.0 licence. The site publishes no pricing, and there is no paid tier or hosted service. A separate plugin hub lists community plugins, and documentation is available in English and Chinese.