Quick answer: Unreal Niagara data channel buffer empty on first frame of new emitter? Channel is late-bound - write during emitter spawn and read on the next tick, not same-tick.
Bullet impact emitter spawns and tries to read hit-point data from a channel. First frame: empty. Second frame: works.
Pre-write the channel
Write the impact data before spawning the emitter. The channel is read at the start of the emitter's tick; same-tick writes haven't propagated.
Use System Parameters
For small payloads (position, normal, energy), pass via system parameters instead of a data channel. They're available immediately on spawn.
Debug with the Niagara debugger
fx.Niagara.Debug.Visualize 1. The data channel visualizer shows writes and reads on the timeline; the empty-first-frame is visible at a glance.
“Data channels are inter-tick. Same-tick payload delivery is a different feature.”
For one-shot effects, parameters beat channels. Channels earn their keep when many emitters read the same shared state.