Telemetry

Each frame the UI polls a telemetry snapshot from the simulation. The shape of that snapshot is a contract shared between Rust (which produces it) and TypeScript (which consumes it), and it is locked by a Vitest test.

The snapshot contract

The TypeScript type is the source of truth for the shape:

src/sim/types.ts

export interface TelemetrySnapshot {
  activeSignals: number
  firedThisFrame: number
  releasedSignalsThisFrame: number
  signalVelocityMean: number
  corticalResponseIndex: number
  onsetResponse: number
  sustainedActivation: number
  focusDrift: number
  regionActivity: Record<RegionKey, number>
  rolling: {
    oneSec: RollingWindow
    threeSec: RollingWindow
    fifteenSec: RollingWindow
  }
}

export interface RollingWindow {
  activeSignalsAvg: number
  firedNeurons: number
  releasedSignals: number
  signalVelocityMean: number
  regionActivity: Record<RegionKey, number>
}

The Rust telemetry_snapshot() serializes a matching structure with serde-wasm-bindgen, so the JavaScript side receives a plain object that satisfies TelemetrySnapshot:

src/brain.ts

getTelemetrySnapshot(): TelemetrySnapshot {
  return this.world.telemetry_snapshot() as TelemetrySnapshot
}

Contract test

src/__tests__/telemetry-contract.test.ts asserts the snapshot shape. If the Rust serialization and the TypeScript type drift apart, pnpm test fails. Keep both in sync when adding a field.

Fields

Instantaneous (this frame):

Field	Meaning
activeSignals	Currently live signals.
firedThisFrame	Neurons that fired this frame.
releasedSignalsThisFrame	Signals released this frame.
signalVelocityMean	Mean travel speed of live signals.
regionActivity	Per-region activity counts.

Derived response metrics:

Field	Meaning
corticalResponseIndex	Headline "responsiveness" score.
onsetResponse	Sharpness of response right after a stimulus.
sustainedActivation	Activity held over time.
focusDrift	How much the dominant region wanders.

Rolling windows

Three rolling windows: oneSec, threeSec, fifteenSec: accumulate averages over their respective time spans. Each RollingWindow carries an average active signal count, fired-neuron and released-signal counts, mean velocity, and per-region activity. The UI uses these to draw the activity-window bars.

Active load and the response index

The response index is built partly from "active load": how full the pool is relative to the live cap:

rust/brain_sim/src/lib.rs

let active_load =
    (self.pool.active_count() as f32
        / self.settings.current_max_signals.max(1) as f32) * 100.0;

Because this normalizes against current_max_signals (default 16_000), the load percentage moves as you change the max-signals setting. The UI's activity bars normalize against the configured cap as well, so they read as a fraction of capacity rather than an absolute count.