Constant MAX_EVENT_DATA_LEN 

pub const MAX_EVENT_DATA_LEN: usize = _; // 65_536usize

Maximum event data length in bytes (64 KiB).

Payloads that exceed this limit are rejected by publish_event with NodeAppError::EventFailed. For larger artifacts, store them (e.g. via core.storage.insert) and emit an event referencing the storage key instead.