State

State is the shared blackboard of the graph: a HashMap<String, serde_json::Value> where each key maps to a Channel. Nodes read from and write to this state; the engine merges updates according to each channel’s strategy.

Nodes receive a snapshot of all channel values when they run. When a node returns NodeOutput::Update, those updates are merged back through each channel’s merge strategy.

Example: reading and writing a counter:

#![allow(unused)]
fn main() {
// Read state
let count = state.get("counter").and_then(|v| v.as_i64()).unwrap_or(0);

// Write back
state.insert("counter".into(), json!(count + 1));
Ok(NodeOutput::Update(state))
}