Error while triggering listener${plural} for event: "${messa

Error message

Error while triggering listener${plural} for event: "${message.event}".

What it means

The bridge's #triggerMessageEvent invokes each registered listener for an incoming bex message event. If any listener callback throws (synchronously or via a rejected Promise), the bridge catches it and warns with this message, embedding the offending event name, the message payload and the failing listener, then continues dispatching.

Source

Thrown at app-vite/exports/bex/private/bex-bridge.js:589

      }
    )

    let responsePayload
    // oxlint-disable-next-line unicorn/no-useless-spread
    for (const { type, callback } of [...list]) {
      if (type === 'once') {
        this.off(message.event, callback)
      }

      try {
        if (responsePayload === void 0) {
          const value = callback(message)
          responsePayload = value instanceof Promise ? await value : value
        } else {
          callback(message)
        }
      } catch (err) {
        this.warn(
          `Error while triggering listener${plural} for event: "${message.event}".`,
          {
            error: err,
            message,
            listener: { type, callback }
          }
        )

        throw err
      }
    }

    return responsePayload
  }

  /**
   * @param {string} portName
   */

View on GitHub (pinned to 4841521b5f)

Solutions

Inspect the `error` field in the details object logged alongside the warning to find the actual exception
Add your own try/catch or .catch() inside the failing listener registered with bridge.on()
Validate the message payload shape in the listener before using it
Verify the event name and listener type matches what the other side actually sends

Example fix

// before
bridge.on('my.event', async payload => {
  const data = await fetch('/api', { body: JSON.stringify(payload) }).then(r => r.json())
  return data.value
})
// after
bridge.on('my.event', async payload => {
  try {
    const res = await fetch('/api', { body: JSON.stringify(payload) })
    const data = await res.json()
    return data.value
  } catch (err) {
    console.error('my.event handler failed', err)
    return null
  }
})

Defensive patterns

Strategy: try-catch

Validate before calling

// validate payload before registering/handling
function isValidMessage(msg) {
  return msg && typeof msg.event === 'string' && msg.payload !== undefined
}

Type guard

function isBridgeMessage(msg) {
  return (
    typeof msg === 'object' && msg !== null &&
    typeof msg.event === 'string' &&
    'payload' in msg
  )
}

Try / catch

bridge.on('my.event', async payload => {
  try {
    if (!isBridgeMessage(payload)) throw new TypeError('bad payload')
    return await handleMessage(payload)
  } catch (err) {
    console.error(`Listener for "my.event" failed`, err)
    return null // don't let the rejection bubble into the bridge
  }
})

Prevention

Wrap every bridge.on() listener body in its own try/catch or .catch()
Validate message payload shape before dereferencing fields
Keep listeners pure of thrown errors; return explicit error values instead
Test listeners with malformed payloads to confirm graceful failure

When it happens

Trigger: A callback registered via bridge.on('<event>', fn) throws or returns a rejected promise while handling an incoming message; also when multiple listeners exist and one of them fails.

Common situations: A listener dereferences undefined message payload fields, JSON-shaped data doesn't match expectations after a payload change, async listener hits a network error, or a bug introduced in an app-level listener during refactoring.

Related errors

AI-assisted analysis of quasarframework/quasar@4841521b5f (2026-08-30). Data as JSON: /api/errors/d218e39de2bb8c92. Report an issue: GitHub.