XIP-57: Messaging fee collection

fbac · February 26, 2025, 5:49pm

XIPs/xip-57-messaging-fee-collection.md

main

---
xip: 57
title: Messaging fee collection
description: The system for collecting fees from Payers and metering their spend across offchain message sending
author: Borja Aranda (@fbac), Nick Molnar (@neekolas)
status: Final
type: Standards
category: Network
created: 2025-02-19
---

## Abstract

This XIP describes how the decentralized XMTP network intends to meter Payer usage and allow Payers to purchase capacity for more usage.

- The Payer Registry smart contract is the canonical source for the confirmed balances of each user of the network (typically applications paying on behalf of many users).
- The Payer Reports contract is an onchain mechanism for reaching consensus on changes to those balances.

XMTP Nodes interact with these two smart contracts to keep track of payer balances and update them as messages are stored. This system is designed to handle total network throughput of tens of thousands of messages per second and makes some trade-offs to reach that kind of capacity.

This file has been truncated. show original

Javier_SL · August 26, 2025, 6:19pm

As the 2025 roadmap sets this XIP for summer, I can’t really tell how far this XIP is in the development process, since it’s still tagged as XIP Stage 1: Drafts in community forums. Still, I’d like to ask: Why was this approach preferred to a subscription-based model?

nick · August 26, 2025, 8:26pm

You’re right that we should update the status. This has been implemented and is in recent releases of xmtpd.

There’s two reasons we prefer “pre-fund your account” to subscriptions

Allows for “pay for what you use” pricing, which is the fairest and hardest to game. You get exactly what you pay for, with no extra costs for unused credits. You can withdraw any excess funds at any time.
Smart contracts still aren’t great for implementing pull based subscription models.