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Forester

Forester is a domain-specific language (DSL) and high-performance Rust runtime designed for building, testing, and executing behavior trees.

It is specifically engineered for two core domains:

  • 🧠 AI Agents: Orchestrating LLM-based tools, state management, and fallback loops without unmaintainable Python code or DAG spaghettification.
  • 🤖 Robotics & Industrial Systems: Managing deterministic, reactive hardware control loops, with built-in export to ROS Nav2 and simulation support for Webots.

Why Forester?

As systems grow in complexity, state machines and Directed Acyclic Graphs (DAGs) break down when handling fallbacks, retries, and dynamic error recovery. Forester separates decision logic (tree orchestration) from execution logic (actions), enabling modular, maintainable control flow.

Key Differentiators

  • Dedicated Orchestration DSL: Write tree logic once in a strongly-typed, functional language featuring higher-order trees, lambdas, and live Blackboard pointers.
  • Sync & Async Execution: Non-blocking async execution for I/O and remote calls, alongside predictable sync execution for tight control loops.
  • Local & Remote Action Clients: Execute actions natively in Rust (forester-rs) or remotely via lightweight clients (such as Python’s forester-http-ra-py for LangChain/LlamaIndex tools).
  • Rich Analysis & Simulation: Inspect execution traces, visualize trees, and test orchestration in simulation before deploying to physical hardware or production agents.
  • ROS Nav2 & Webots Integration: Export Forester trees directly into ROS Nav2 XML or run against Webots simulation environments.
  • Static Validations & Optimizations: Catch tree errors, numeric overflows, and structural flaws at compile time rather than runtime.

Why Behavior Trees?

Behavior trees provide a clean, mathematical abstraction over decision logic:

  • Modularity: Small, independent nodes (sequences, fallbacks, decorators) can be composed into deep hierarchical behaviors.
  • Reactivity: Ticks evaluate preconditions dynamically, allowing real-time preemptions and fallbacks when environment state changes.
  • Separation of Concerns: Tree nodes decide what to do next; external action handlers perform how it gets done.

Learn More About Behavior Trees

  • BehaviorTree.CPP — C++ behavior tree framework widely used in ROS2.
  • Beehave — Behavior tree AI library for the Godot Engine.
  • Bonsai — Pure Rust behavior tree implementation.