Delegation — a call tree that is one process's state

How it works

A tool run is a process that yields its own trace node. An agent is a tool whose run spawns more runs, one per tool call, and folds their streams into its node's children. So the root's state is the whole tree, and the graph is a view of that one value.

const runs = calls.map((c) => spawn(c.use.run, c.run, { initial: c.node }))
for await (const [i, child] of merge(runs, self.signal)) {
  n = { ...n, children: n.children.with(at + i, child) }
  yield n
}

Parallel tool calls are just several spawns merged. The runs belong to the agent that spawned them, so stop disposes the root and every model call and search under it aborts through self.signal.

The tests (delegation.test.ts) iterate the root run with no DOM and check the tree, the parallelism at both levels, and that disposal reaches every leaf.