frxUSD Redemption & Minting Integration Request

Technical
1

Title

Integration of frxUSD ↔ USDC and USTB Redemption & Minting via ERC‑4626‑Compatible Custodian and RWA Redemption Paths on the Ethereum chain.

Author

Frax team
Contact via telegram: @denett4

Simple Summary

This proposal details integration with Frax’s on‑chain flow that enables direct swaps between frxUSD ↔ USDC and redemption of frxUSD via USTB → USDC. It leverages ERC‑4626 compatible custodian contracts (USDC and USTB) and the RWARedemptionCoordinator for seamless settlement.

Motivation

  • Unique Value: On‑chain, permissionless swaps between frxUSD and USDC; plus real‑world collateral (USTB) redemption support.

  • Settlement Quality: Efficient redemption paths with real‑time quoting via preview functions; fallbacks via RWA coordinator.

  • Supported Pairs: frxUSD/USDC native; frxUSD → USTB → USDC via coordinator.

  • Liquidity & Volume: The USDC Custodian has $10M in mint and up to $500k in redeem liquidity. The USTB path has $10M in redeem liquidity. Volume has been $600k in the last 24h.

Technical Specification

Price Discovery

  • On‑chain quoting:

    • previewDeposit(amount), previewMint(amount): estimate frxUSD out from USDC input

    • previewRedeem(amount), previewWithdraw(amount): estimate USDC out from frxUSD input

    • These calls provide deterministic price quotes per the ERC‑4626 custodian logic.

Settlement Interface

Custodian Contracts (Ethereum Mainnet)

  • USDC custodian (“frxUSD‑USDC Custodian Proxy”)

    • Address: 0x4f95c5ba0c7c69fb2f9340e190ccee890b3bd87c

    • ERC‑4626 compatibility: deposit/mint for minting frxUSD with USDC; redeem/withdraw for burning frxUSD to receive USDC; preview functions for quoting.

  • USTB custodian (“frxUSD‑USTB Custodian Proxy”)

    • Address: 0x5fbaa3a3b489199338fbd85f7e3d444dc0504f33

    • Same ERC‑4626 interface; requires Whitelist via Superstate to use.

RWA Redemption Coordinator

  • RWARedemptionCoordinator Proxy

    • Address: 0x19D7Df1387e7722FcCcE2aab4B7FfC72e6592934

    • Provides redeemRWA(frxUSD_amount): atomically swaps frxUSD → USTB → USDC (handling USTB custodian redemption under the hood), bypassing whitelist restrictions because coordinator is whitelisted.

Example transactions:

Additional Information

  • Limitations:

    • Mint and redemption caps per custodian apply.

    • USTB redeems are limited by USTB in custodian and Superstate liquidity pool found here: 0x4c21b7577c8fe8b0b0669165ee7c8f67fa1454cf

Contact Information

  • Technical Support via telegram: @denett4

  • Expected Response: 24h on technical queries

2

Hi, thanks for the information here. I’m not sure about the efficacy of advertising these routes / integration here, but they are certainly good to be somewhere other than nowhere. There are alternatively discord channels (a dedicated solvers channel) where you can raise solver related issues that may get escalated via the team to solvers, though for route integration, this is less common a thoroughfare for these kinds of things.

3

I’ve asked to post here so it doesn’t sit on silo’d groups.
Would def be open to suggestions for how to make this info most visible and accessible to solvers.

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