emit a custom event when the player enters a trigger

To make one entity react when another is triggered, WIRE them with a custom event instead of reaching across entities directly. The sensor's trigger handler emits a named event (ctx.events.emit or the emitCustomEvent op); the responder declares a matching onCustomEvent handler with createCustomEventHandler and does its work there. Events are room-scoped so any subscriber reacts, and the two scripts stay decoupled.

make one entity react when another entity is triggered

To make one entity react when another is triggered, WIRE them with a custom event instead of reaching across entities directly. The sensor's trigger handler emits a named event (ctx.events.emit or the emitCustomEvent op); the responder declares a matching onCustomEvent handler with createCustomEventHandler and does its work there. Events are room-scoped so any subscriber reacts, and the two scripts stay decoupled.

broadcast a signal from a trigger to a remote object

To make one entity react when another is triggered, WIRE them with a custom event instead of reaching across entities directly. The sensor's trigger handler emits a named event (ctx.events.emit or the emitCustomEvent op); the responder declares a matching onCustomEvent handler with createCustomEventHandler and does its work there. Events are room-scoped so any subscriber reacts, and the two scripts stay decoupled.

custom event wiring between two entities

To make one entity react when another is triggered, WIRE them with a custom event instead of reaching across entities directly. The sensor's trigger handler emits a named event (ctx.events.emit or the emitCustomEvent op); the responder declares a matching onCustomEvent handler with createCustomEventHandler and does its work there. Events are room-scoped so any subscriber reacts, and the two scripts stay decoupled.

Event wiring one trigger emits another responder reacts

The recipe

Author both scripts with project_apply_script_semantic_patch using the ai_safe op pack.

Sensor side: give the trigger object a trigger ColliderComponent (collision:"trigger") via project_add_component, then addTriggerHandler ({ "handlerKey":"onSignal" }). In the whole-body GessaScript (replaceScriptFromGessaScript) emit the event: ctx.events.emit("door_opened", { open: true }). The emitCustomEvent op is the declarative equivalent when you want the event declared in the script's event set.
Responder side: on the door (or lamp, or gate) entity declare the matching handler with createCustomEventHandler ({ "eventKey":"door_opened" }), which creates a guarded onCustomEvent handler for that semantic key. patchComponent acts on the entity the handler lives on, so its body does the reaction directly, e.g. ctx.entity.patchComponent("TransformComponent", { position: {...open} }).
Idempotency: guard the responder with setBooleanState ({ "field":"opened", "value": true }) and check it first, so a second emit does not re-run the open.
Payload: pass ids or values in the emit payload ({ source, amount }) and read them in the handler; do not encode data in the event NAME.
Fan-out is free: any number of responders that declare the same onCustomEvent key all react to one emit. Use distinct event names per wire (gate_north_open, lamp_hall_on) so unrelated responders stay silent.

Pitfalls

ctx.events.emit is ROOM-scoped (audience room), so EVERY subscriber of that name reacts. Name events per wire, not generically, or a far responder fires unexpectedly.
Do not make the trigger reach across and mutate the other entity directly by guessing its id; the event wire is what keeps the sensor and responder decoupled and reorderable.
The responder needs its OWN script carrying the onCustomEvent handler; an emit with no declared subscriber is silently dropped.
An event is ephemeral: a responder spawned AFTER the emit never sees it. Drive persistent open/closed truth through setBooleanState, and read that on spawn.

Verify

simulation_run (qa.run.start) tripping the sensor trigger and asserting the remote responder reached its reacted state.
project_get_graph_snapshot to confirm the trigger handler on the sensor and the onCustomEvent handler on the responder both landed.

The recipe

Pitfalls

Verify

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