EventManager

The EventManager handles event subscriptions and dispatching within a AppSession. It provides methods for subscribing to various event types from the MentraOS platform. You access the EventManager through the events property of a AppSession instance:

const eventManager = appSession.events

Event Handler Methods

onTranscription()

Registers a handler for real-time speech transcription events.

onTranscription(handler: (data: TranscriptionData) => void): () => void

Parameters:

handler: Callback function that receives TranscriptionData objects

Returns: An unsubscribe function to remove the handler Example:

const unsubscribe = appSession.events.onTranscription(data => {
  console.log(`Transcription: ${data.text}, Final: ${data.isFinal}`)
  if (data.isFinal) {
    // Process the final transcription
  }
})

// Later, to stop receiving events:
unsubscribe()

onHeadPosition()

Registers a handler for head position change events.

onHeadPosition(handler: (data: HeadPosition) => void): () => void

Parameters:

handler: Callback function that receives HeadPosition objects

Returns: An unsubscribe function to remove the handler Example:

appSession.events.onHeadPosition(data => {
  if (data.position === "up") {
    console.log("User looked up")
  } else if (data.position === "down") {
    console.log("User looked down")
  }
})

onButtonPress()

Registers a handler for hardware button press events on the glasses.

onButtonPress(handler: (data: ButtonPress) => void): () => void

Parameters:

handler: Callback function that receives ButtonPress objects

Returns: An unsubscribe function to remove the handler Example:

appSession.events.onButtonPress(data => {
  console.log(`Button ${data.buttonId} was ${data.pressType} pressed`)
})

onPhoneNotifications()

Registers a handler for notifications received from the connected phone.

onPhoneNotifications(handler: (data: PhoneNotification) => void): () => void

Parameters:

handler: Callback function that receives PhoneNotification objects

Returns: An unsubscribe function to remove the handler Example:

appSession.events.onPhoneNotifications(data => {
  console.log(`Notification from ${data.app}: ${data.title} - ${data.content}`)
})

onGlassesBattery()

Registers a handler for glasses battery update events.

onGlassesBattery(handler: (data: GlassesBatteryUpdate) => void): () => void

Parameters:

handler: Callback function that receives GlassesBatteryUpdate objects

Returns: An unsubscribe function to remove the handler Example:

appSession.events.onGlassesBattery(data => {
  console.log(`Glasses battery: ${data.level}%, Charging: ${data.charging}`)
})

onPhoneBattery()

Registers a handler for phone battery update events.

onPhoneBattery(handler: (data: PhoneBatteryUpdate) => void): () => void

Parameters:

handler: Callback function that receives PhoneBatteryUpdate objects

Returns: An unsubscribe function to remove the handler

onVoiceActivity()

Registers a handler for Voice Activity Detection (VAD) events.

onVoiceActivity(handler: (data: Vad) => void): () => void

Parameters:

handler: Callback function that receives Vad objects

Returns: An unsubscribe function to remove the handler Example:

appSession.events.onVoiceActivity(data => {
  if (data.status === true || data.status === "true") {
    console.log("User is speaking")
  } else {
    console.log("User stopped speaking")
  }
})

onLocation()

An event handler for raw location updates. Use the LocationManager to access location data, as it provides a simple interface for both streaming and polling.

onLocation(handler: (data: LocationUpdate) => void): () => void

Parameters:

handler: Callback function that receives LocationUpdate objects

Returns: An unsubscribe function to remove the handler

onCalendarEvent()

Registers a handler for calendar event notifications.

onCalendarEvent(handler: (data: CalendarEvent) => void): () => void

Parameters:

handler: Callback function that receives CalendarEvent objects

Returns: An unsubscribe function to remove the handler

onAudioChunk()

Registers a handler for raw audio data chunks. Requires explicit subscription.

onAudioChunk(handler: (data: AudioChunk) => void): () => void

Parameters:

handler: Callback function that receives AudioChunk objects

Returns: An unsubscribe function to remove the handler Note: Audio chunks require an explicit subscription using appSession.subscribe(StreamType.AUDIO_CHUNK).

System Event Handlers

onConnected()

Registers a handler for when the WebSocket connection is successfully established and authenticated.

onConnected(handler: (data: AppSettings | undefined) => void): () => void

Parameters:

handler: Callback function that receives optional AppSettings upon connection

Returns: An unsubscribe function to remove the handler Example:

appSession.events.onConnected(settings => {
  console.log("Connected to MentraOS Cloud")
  if (settings) {
    console.log("Initial settings received:", settings)
  }
})

onDisconnected()

Registers a handler for when the WebSocket connection is closed or lost.

onDisconnected(handler: (reason: string) => void): () => void

Parameters:

handler: Callback function that receives a reason string

Returns: An unsubscribe function to remove the handler Example:

appSession.events.onDisconnected(reason => {
  console.log(`Disconnected from MentraOS Cloud. Reason: ${reason}`)
})

onError()

Registers a handler for WebSocket or SDK-level errors.

onError(handler: (error: WebSocketError | Error) => void): () => void

Parameters:

handler: Callback function that receives a WebSocketError or standard Error object

Returns: An unsubscribe function to remove the handler Example:

appSession.events.onError(error => {
  console.error("Error in App session:", error)
})

onSettingsUpdate()

Registers a handler for when the application settings are updated by the user via MentraOS Cloud.

onSettingsUpdate(handler: (settings: AppSettings) => void): () => void

Parameters:

handler: Callback function that receives the complete updated AppSettings array

Returns: An unsubscribe function to remove the handler Example:

appSession.events.onSettingsUpdate(settings => {
  console.log("Settings updated:", settings)
})

onSettingChange()

Registers a handler that triggers only when a specific setting’s value changes.

onSettingChange<T>(
  key: string,
  handler: (value: T, previousValue: T | undefined) => void
): () => void

Parameters:

key: The key of the setting to monitor
handler: Callback function that receives the new value and the previous value (or undefined initially)

Returns: An unsubscribe function to remove the handler Example:

appSession.events.onSettingChange<boolean>("enableNotifications", (newValue, oldValue) => {
  console.log(`enableNotifications changed from ${oldValue} to ${newValue}`)
  if (newValue) {
    // Enable notification features
  } else {
    // Disable notification features
  }
})

Generic Event Handler

on()

Generic event handler for any StreamType. Use specific methods above where possible.

on<T extends StreamType>(
  type: T,
  handler: (data: StreamDataTypes[T]) => void
): () => void

Parameters:

type: The StreamType to listen for
handler: Callback function that receives data of the appropriate type for the specified StreamType

Returns: An unsubscribe function to remove the handler Example:

import {StreamType} from "@mentra/sdk"

// Subscribe to a specific stream type
appSession.events.on(StreamType.LOCATION_UPDATE, data => {
  console.log(`Location update: ${data.lat}, ${data.lng}`)
})

// Using a language-specific stream
const transcriptionStream = createTranscriptionStream("en-US")
appSession.events.on(transcriptionStream, data => {
  console.log(`English transcription: ${data.text}`)
})

Getting Started

Core Concepts

SDK Reference

EventManager

EventManager

Event Handler Methods

onTranscription()

onHeadPosition()

onButtonPress()

onPhoneNotifications()

onGlassesBattery()

onPhoneBattery()

onVoiceActivity()

onLocation()

onCalendarEvent()

onAudioChunk()

System Event Handlers

onConnected()

onDisconnected()

onError()

onSettingsUpdate()

onSettingChange()

Generic Event Handler

on()

​EventManager

​Event Handler Methods

​onTranscription()

​onHeadPosition()

​onButtonPress()

​onPhoneNotifications()

​onGlassesBattery()

​onPhoneBattery()

​onVoiceActivity()

​onLocation()

​onCalendarEvent()

​onAudioChunk()

​System Event Handlers

​onConnected()

​onDisconnected()

​onError()

​onSettingsUpdate()

​onSettingChange()

​Generic Event Handler

​on()

EventManager

Event Handler Methods

onTranscription()

onHeadPosition()

onButtonPress()

onPhoneNotifications()

onGlassesBattery()

onPhoneBattery()

onVoiceActivity()

onLocation()

onCalendarEvent()

onAudioChunk()

System Event Handlers

onConnected()

onDisconnected()

onError()

onSettingsUpdate()

onSettingChange()

Generic Event Handler

on()