# Limits and runtime faults

| Limit | Value | When it is exceeded |
|---|---|---|
| Events emitted by one action | 1,000, and as many for each item's action of a batch | Defect: the action fails and rolls back |
| Size of one event | 64 KB | Defect: the action fails and rolls back |
| Events causing events, from one request | 16 deep | The delivery fails with `event_chain_limit`, stopping loops; paging uses batches, not chains |
| One run of a subscriber or schedule | The time limit of the route or integration it calls, at most 15 minutes and what is left of its invocation's budget ([Running background work](where-events-travel.md#running-background-work)) | Treated as a timeout: retried if nothing outside was called, otherwise `outcome_unknown` |
| Changing calls in one action | 8, on its longest path, package actions' calls included | Compile error |
| One batch of a batch run | 1,000 items or 4 MiB of file, whichever comes first | The batch ends and the next begins |

These limits may change once they have been measured on real runs.