# `preview_sync`

Use before any synchronization. It locally serializes the exact bounded,
source-free payload and returns destination, repository identity, sections,
counts, byte size, body hash, and a short-lived confirmation token. It makes no
network request.

Inputs: optional `payload_version` 2 or 3 (default 3), plus optional
`output_format`.

```json
{"payload_version":3,"output_format":"json"}
```

Show the exact preview for approval. Any graph, destination, repository,
payload-version, or expiry change invalidates that approval.