> ## 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.

# Paymasters (Legacy Chain)

> Gas sponsorship in Sophon v1

<Warning>
  This page describes paymasters in the legacy Sophon v1 chain. Do not begin a new
  production deployment on Sophon; see the [migration guide](/migration) for current
  actions.
</Warning>

Paymasters were ZK Stack smart contracts that could pay or customize gas fees for a
Sophon transaction. Applications used them to sponsor user activity, set allowance
rules, grant NFT-based fee benefits, or accept an ERC-20 token in place of SOPH.

The implementation guide is retained for teams maintaining a legacy deployment
during the wind-down: [Setting Up Paymasters](/build/setting-up-paymasters).