BehaviorTree.CPP

C++ behavior tree library for robot task planning, powering Nav2 and ROS 2 systems

License

MIT

Overview

BehaviorTree.CPP is a C++ library for creating and executing behavior trees for robot task planning. Trees are defined in XML and built from Action, Condition, Control and Decorator nodes that share data through a blackboard, with logging and replay for debugging. It is the foundation of the behavior-based navigation in Nav2 for ROS 2.

BehaviorTree.CPP is a high-performance C++ library for creating behavior trees, widely used in robotics for task planning and execution. It's the foundation for Nav2's behavior-based navigation system.

Key features include: - XML-based tree definition - Custom node types (Action, Condition, Control, Decorator) - Blackboard for data sharing - Logging and replay for debugging - Real-time capable execution - Groot graphical editor - ROS 2 integration - Extensive documentation and tutorials

The library is used in production by many robotics companies for complex task execution, from manipulation sequences to multi-robot coordination.

Why it matters

BehaviorTree.CPP is the standard framework for robot task planning in ROS 2. It provides the structured way to compose complex robot behaviors that Nav2 and many other ROS 2 packages rely on — making it foundational infrastructure for autonomous robots.

Problem it solves

Complex robot behaviors (navigate, pick up, inspect, recover from errors) are hard to express as finite state machines. Behavior trees provide a modular, hierarchical alternative that is easier to design, debug, and modify.

Key takeaways

• Industry-standard C++ library for behavior tree execution
• Foundation of Nav2 navigation and many ROS 2 autonomy packages
• Graphical editor (Groot2) for visual behavior tree design
• Supports async actions, subtrees, and runtime tree modification
• Reactive and modular architecture for complex robot behaviors

Who it is for

• ROS 2 developers building autonomous robot behaviors
• Robotics engineers designing task planning systems
• Teams using Nav2 who need custom navigation behaviors
• Game developers applying behavior trees to robot AI

Limitations

• C++ library requires C++ knowledge for custom nodes
• Behavior tree design patterns have a learning curve
• Groot2 graphical editor is commercial for advanced features
• Debugging complex trees requires understanding of tick propagation