Mountain Protocol

Rebase mechanics & the wUSDM wrapper

USDM distributes yield by adjusting a global reward multiplier rather than minting per-holder, using a share-based accounting model similar to Lido's stETH.

• balanceOf(account) = shares[account] × rewardMultiplier; shares are fixed at deposit.
• rewardMultiplier increases daily (~12:00 UTC) via addRewardMultiplier — e.g. 1.000 → 1.038 after a year at 3.8% APY, turning 100 USDM into 103.8 USDM.
• Rebasing breaks naive DeFi integrations that cache balances, so wUSDM wraps USDM in an ERC-4626 vault.
• wUSDM keeps a static balance while the share-to-asset exchange rate climbs — the standard non-rebasing pattern protocols expect.

Reserves & Bermuda regulation

USDM was a regulated, fully-reserved instrument rather than a DeFi-native synthetic — its credibility rested on the SPV structure and BMA oversight.

• Issued under Bermuda's Digital Asset Business Act (DABA) + Single-Currency Pegged Stablecoin (SCPS) guidance; BMA license #202302512.
• Reserves in USDM Reserves Ltd, a bankruptcy-remote SPV, segregated from operating funds and managed by EQ Capital.
• Composition: short-duration US T-bills (~60-day avg maturity), money-market funds, Treasury ETFs, repos, plus an over-collateralization buffer.
• AML/CFT monitoring, OFAC/sanctions screening, and monthly third-party reserve attestations.

Composability & multi-chain footprint

Mountain optimized for being an 'ingredient' dollar that other protocols and neo-banks embed.

• Deployed on Ethereum, Base, Polygon, Arbitrum and Optimism — same USDM and wUSDM addresses across chains.
• USDM usable as a plain rebasing ERC-20; wUSDM as a non-rebasing ERC-4626 share for AMMs, lending and yield markets.
• Open-source token contracts on GitHub (mountainprotocol/tokens).
• Series A thesis (Multicoin, 2024) was to extend USDM to Solana and real-world businesses — superseded by the Anchorage acquisition.

Acquisition & wind-down risk

Anchorage Digital announced the acquisition on May 12, 2025, absorbing Mountain's team, technology and BMA license to bolster institutional stablecoin offerings — and Mountain simultaneously began an orderly wind-down of USDM.

• Phase 1 (May 12 – Jun 11, 2025): minting disabled, rewards still active.
• Phase 2 (Jun 12 – Jul 11, 2025): reward rate reduced to 0%.
• Phase 3 (from Aug 22, 2025): reserves migrated to a Uniswap v4 concentrated-liquidity wUSDM:USDC pool on Ethereum; holders redeem exclusively via Uniswap — no platform custody.
• Residual risk: secondary-market peg now depends on Uniswap liquidity rather than 1:1 primary redemption; BMA coordination continues through the transition.

Architecture

USDM is a share-based rebasing ERC-20: the contract stores per-account shares and a global rewardMultiplier, deriving balanceOf as shares × rewardMultiplier. wUSDM is an OpenZeppelin ERC-4626 vault wrapping USDM into a non-rebasing, value-accruing share. Both are deployed at identical addresses on Ethereum, Base, Polygon, Arbitrum and Optimism. Mint/redeem against fiat/USDC was gated behind a KYC'd primary-market account (web portal or API); on-chain, USDM and wUSDM behave like ordinary tokens, so most integrators just consumed them as ERC-20 / ERC-4626.

Integration shape

Three integration shapes: (1) hold/transfer USDM as a rebasing ERC-20 and let balances grow; (2) wrap to wUSDM via the ERC-4626 deposit/withdraw interface to get a static, composable balance for AMMs and lending; (3) for primary mint/redeem, onboard as a KYC'd institution and call the mint/redeem platform API. [verify current API surface — the platform is in wind-down and redemption has moved to a Uniswap v4 wUSDM:USDC pool].

API surface

balanceOf / sharesOf

USDM balance = shares × rewardMultiplier; sharesOf returns the fixed underlying share count.

rewardMultiplier()

Global accrual factor, bumped daily (~12:00 UTC) via addRewardMultiplier (privileged).

deposit / mint (ERC-4626)

wUSDM: deposit USDM → receive non-rebasing wUSDM shares.

redeem / withdraw (ERC-4626)

wUSDM: burn shares → receive USDM (convertToAssets for quoting).

Primary mint/redeem API

KYC-gated: buy USDM with USDC/fiat wire and redeem 1:1, with weekly limits. [verify — wind-down]

Minimal integration

Wrap rebasing USDM into non-rebasing wUSDM (ERC-4626) for DeFi composability.

import { createWalletClient, http, parseUnits, getContract } from 'viem';
import { mainnet } from 'viem/chains';

const USDM  = '0x59D9356E565Ab3A36dD77763Fc0d87fEaf85508C';
const WUSDM = '0x57F5E098CaD7A3D1Eed53991D4d66C45C9AF7812';

const client = createWalletClient({ chain: mainnet, transport: http() });

// 1) approve wUSDM to pull USDM
await client.writeContract({
  address: USDM, abi: erc20Abi, functionName: 'approve',
  args: [WUSDM, parseUnits('1000', 18)],
});

// 2) deposit USDM -> receive value-accruing wUSDM shares (ERC-4626)
await client.writeContract({
  address: WUSDM, abi: erc4626Abi, functionName: 'deposit',
  args: [parseUnits('1000', 18), myAddress],
});
// wUSDM balance stays flat; convertToAssets(shares) rises as yield accrues.

Build notes

• Never cache USDM balances — they rebase daily; read balanceOf fresh, or hold wUSDM and use convertToAssets for valuation.
• USDM/wUSDM share the same address on all five chains, simplifying multi-chain integrations.
• USDM is restricted from US persons and primary mint/redeem requires KYC; secondary holders are DEX-only.
• [verify] Project is in wind-down — redemption now flows through a Uniswap v4 wUSDM:USDC pool rather than the issuer; treat the platform API as deprecated.