go-bt

A minimalist behavior-tree library for Go. Designed for background workers, game AI, task automation, and asynchronous logic. Nodes return state instantly (cooperative multitasking) rather than blocking with goroutines or sleeps.

How it works

Every node's Run method returns one of three integers: 1 (success), 0 (running), -1 (failure). A supervisor ticks the tree on a configurable interval, and each tick propagates through the tree without blocking.

The core abstraction is BTContext[T], a generic context that embeds Go's context.Context (for cancellation/timeouts) and carries a typed blackboard — a shared state struct that nodes read from and write to.

Node types:

• Composites — Selector (try children until one succeeds), Sequence (run children until one fails), MemSequence (resume from where it left off)
• Decorators — Inverter, Optional (swallow failures), Timeout, Retry, Repeat
• Leaves — Condition (check blackboard), Action (do work), Sleep (non-blocking wait)

Usage

type WorkerState struct {
    IsConnected  bool
    PendingTasks int
}

tree := composite.NewSelector(
    composite.NewSequence(
        leaf.NewCondition(func(bb *WorkerState) bool {
            return bb.IsConnected
        }),
        leaf.NewAction(func(ctx *core.BTContext[WorkerState]) int {
            ctx.Blackboard.PendingTasks--
            return 1
        }),
    ),
)

supervisor := core.NewSupervisor(tree, 100*time.Millisecond, func(err any) {
    println("recovered:", err)
})
wg := supervisor.Start(btCtx)
wg.Wait()

Testing

The library injects a clock on BTContext, so temporal nodes (Timeout, Sleep) can be tested by advancing time artificially — no real waits needed.

Limitations

Very new (April 2026, ~73 stars). No license declared yet. No parallel node for concurrent child execution. The stateless composite design means MemSequence is the only way to resume mid-sequence across ticks.

For data-oriented entity management to pair with per-entity behavior trees, see Ark — both are minimal Go libraries with similar design philosophy.

https://github.com/rvitorper/go-bt