Events

Every APIExpose event is a JSON envelope pushed over WebSocket:

{
  "Type": "ui.game.started",
  "Ts": "2026-07-08T13:05:12.412Z",
  "NodeId": "cab-01",
  "CorrelationId": "6f0c…",
  "Payload": { }
}

The SDK normalizes it before your handlers run:

client.on('game.changed', (event) => {
  event.type;      // normalized name that matched your subscription
  event.rawType;   // original APIExpose Type, e.g. "ui.game.started"
  event.timestamp; // ISO string
  event.nodeId;    // "cab-01"
  event.payload;   // Payload, camelCase and PascalCase both accepted
});

The raw type is always re-emitted as-is alongside any alias — nothing is hidden. The JSON Schema of the envelope lives in schemas/event.schema.json.

Normalized aliases

Alias	Raw prefix / type	Fires when
`game.changed`	`ui.game.selected*` (deduplicated per system+rom)	a different game is selected or started
`game.selected`	`ui.game.selected*`	every selection event
`system.changed`	`ui.system.selected*`	the ES system changes
`score.changed`	`score.live.*`	the live score changes in-game
`timer.changed`	`timer.live.*`	the live timer ticks
`hiscore.changed`	`hiscore.*`	hiscore data is refreshed
`achievement.unlocked`	`retroachievements.achievement.unlock*`	a RetroAchievements cheevo pops
`arcade.output.changed`	`mame.output.changed`, `arcade.output*`	MAME/FBNeo lamps & outputs
`media.changed`	`media.*`	media/scraping activity
`panel.changed`	`panel.state`	the control-panel layout changes
`connection.lost` / `connection.restored`	(SDK-internal)	WebSocket connectivity

Wildcards

client.on('retroachievements.*', handler); // any raw type with that prefix
client.on('*', handler);                   // everything (used by the debug monitor)

Real event types, observed live

Captured on APIExpose 1.1.1 while launching Sonic The Hedgehog (Megadrive, RetroArch):

ui.game.started.raw / ui.game.started
retroarch.wrapper.connected
retroarch.memory.changed
retroachievements.session.login.detected
retroachievements.session.started
retroachievements.session.updated
retroachievements.catalog.updated
retroachievements.achievementsets.loaded
retroachievements.proxy.requested / retroachievements.proxy.response
panel.state
cpo.panel.config.selected
marquee.snapshot / marquee.snapshot.updated
topper.snapshot
instruction-card.snapshot
screen.snapshot

During gameplay (including ES demo mode) score.live.changed and timer.live.changed flow for systems with score support.

Payload shapes vary

Payloads are event-specific and may evolve with APIExpose. Treat unknown fields as optional — the Event Debug Monitor is the quickest way to inspect the exact payloads your installation produces.