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

# Validium Architecture (Legacy)

> How Sophon v1 used offchain data availability

<Warning>
  This page documents the legacy Sophon v1 chain architecture. The Sophon Chain is
  being wound down; see the [migration guide](/migration) for current actions.
</Warning>

Sophon v1 was implemented as a Validium built with the ZK Stack. A Validium keeps
transaction data outside Ethereum while publishing validity proofs to Ethereum,
reducing data costs while retaining proof-based verification of chain state.

Sophon used [Avail](https://www.availproject.org/) as its external data-availability
layer. Avail stored the data needed to reconstruct state, while Ethereum verified
the validity proofs associated with transaction batches.

This architecture is retained as historical context only; it is not a roadmap for a
new Sophon chain deployment.