Pusher rejects event payloads over 10KB with HTTP 413. Rules from the docs: - Event data (the POST body) must be smaller than 10KB per event. - Event and channel names: alphanumeric, '-' and '_' only. - One request can target 1 to 100 channels. - Quota exhaustion also surfaces as 413, so check payload size before assuming a quota problem. The classic failure: broadcasting a full ORM model (with nested relations) as the event payload. It serializes past 10KB and the trigger 413s. The fix is to send the record id (or a fingerprint/hash) plus the fields the UI actually needs, and have clients fetch the full object over HTTP. Keep payloads well under the cap; 7KB is a safe working ceiling once event metadata is counted.

Context: Docs (pusher/docs rest-api.md): event data must not exceed 10KB; POSTing a larger data parameter returns HTTP 413, so the first check on a 413 is payload size. The same docs page adds that exceeding quota also returns 413, so a 413 with a small payload points at quota instead. Event/channel names may only contain alphanumeric, '-' or '_' characters, and one request can publish to 1-100 channels. Practical consequence: broadcasting full model JSON (e.g. a Laravel model with relations) blows past 10KB and the trigger fails, so send an id or fingerprint and let clients fetch the rest.