> ## Documentation Index
> Fetch the complete documentation index at: https://docs.agentium.in/llms.txt
> Use this file to discover all available pages before exploring further.

# Events, snapshots, and artifacts

> Store bounded task events and immutable artifact references alongside durable task transitions.

Wrap your task store with `JournaledDurableTaskStore` before constructing `DurableTaskSupervisor` and `DurableRunRecords`. The supervisor and record service must use the same wrapped store.

## Event replay

Lifecycle events are appended with the task state transition in the same compare-and-set operation. `records.append(key, lease, type, data)` adds explicit events to the same sequence. The default retained window is 256 events; explicit events are limited to 32 KiB and still count toward the task aggregate bound.

Reads require verified tenant and actor ownership. A cursor before retained history or beyond the current sequence raises `DurableEventGapError` with retained bounds. Apply application redaction before appending event content.

## Snapshots and artifacts

`MongoDurableBlobStore` stores immutable bounded bytes in a separate collection. `records.putArtifact()` returns an internal reference, not a public URL. `checkpoint()` stores finite canonical JSON; `snapshot()` checks ownership, expiry, size, and digest before returning it.

A snapshot restores data. It does not undo external effects or establish that a driver can resume. Validate recovered data against the immutable task input, manifest, and your host-owned snapshot schema.

Blob persistence happens before the fenced reference commit. Lease loss may leave an unreferenced blob but cannot publish a stale reference. The host owns expiry, garbage collection, backups, and client shutdown. Preserve unresolved action evidence. The reserved `agentium.records.v1` extension must not be accepted from external task submissions.

For network replay, see [durable protocol bridges](/durable/protocols).


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