# OP-Stack

## OpPreconf

Preconfirmation structure containing a sequencer-signed execution payload. Preconfirmations are OP-Stack sequencer commitments that provide early block availability.

The Type is defined in [src/chains/op/ssz/op\_proof\_types.h](https://github.com/corpus-core/colibri-stateless/blob/v1.1.26/src/chains/op/ssz/op_proof_types.h#L48).

```python
class OpPreconf(Container):
    payload   : Union [         # the execution payload (compressed or uncompressed)
        Bytes[1073741824],      # ZSTD-compressed execution payload (domain + payload)
        Bytes[1073741824]]      # uncompressed execution payload (domain + payload)
    signature : ByteVector [65] # the sequencer signature (65 bytes: r, s, v)
```


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