tl;dr: Apache Burr (Incubating) is a pure-Python framework for building stateful AI applications like chatbots and multi-agent systems, modeling them as actions and state transitions without DSLs or YAML. It includes built-in observability via a UI, state persistence, human-in-the-loop pauses, parallelism/branching, and replay-based testing. It's designed to integrate with existing stacks rather than wrap or lock users into specific tools.