Smart ContractsStabilityPool

StabilityPool

The Stability Pool is the first line of defense for liquidations. Users deposit moonUSD to earn interest yield and receive collateral from liquidated positions at a discount.

Address (Sepolia): 0x5622000f5e62e1a09fe586b5d41c2c1c2b6cd0701eae9ed85118658ff67e3d4

How It Works

The pool uses a Liquity-style O(1) accounting system with two running variables:

  • P (product factor): Tracks moonUSD loss from liquidations. Each absorption multiplies P by (1 - absorbed/total).
  • S (sum factor per collateral): Tracks collateral gains. Each absorption adds collateral / total_deposits to S.

This means deposit balances and gains update in O(1) time regardless of how many liquidations occur.

Deposit Accounting

compounded_deposit = initial_deposit × (P_current / P_at_deposit)
collateral_gain    = initial_deposit × (S_current - S_at_deposit)

When P drops below a threshold (1e-9), an epoch reset occurs to prevent underflow.

User Functions

deposit

Deposit moonUSD into the Stability Pool.

fn deposit(ref self: TContractState, amount: u256)

withdraw

Withdraw moonUSD from the pool (compounded balance).

fn withdraw(ref self: TContractState, amount: u256)

claim_collateral_gains

Claim accumulated collateral from liquidations.

fn claim_collateral_gains(ref self: TContractState, collateral_type: felt252)

claim_interest_yield

Claim accumulated interest distributions.

fn claim_interest_yield(ref self: TContractState)

CDPManager-Only Functions

absorb_liquidation

Called by CDPManager during liquidation. Burns moonUSD from the pool and records collateral gain.

fn absorb_liquidation(
    ref self: TContractState,
    collateral_type: felt252,
    debt_to_absorb: u256,
    collateral_to_receive: u256,
)

distribute_interest

Distributes interest payments from CDPManager to depositors.

fn distribute_interest(ref self: TContractState, amount: u256)

Read Functions

fn get_total_deposits(self: @TContractState) -> u256
fn get_depositor_balance(self: @TContractState, depositor: ContractAddress) -> u256
fn get_depositor_collateral_gain(
    self: @TContractState, depositor: ContractAddress, collateral_type: felt252
) -> u256
fn get_compounded_deposit(self: @TContractState, depositor: ContractAddress) -> u256

Yield Sources

  1. Interest distributions — 75% of CDP interest payments flow to SP depositors
  2. Liquidation collateral — BTC collateral received at ~110% of debt value (10% bonus)
  3. Borrow fees — 75% of upfront borrow fees

Risk

  • Deposited moonUSD is partially consumed during liquidations (replaced by collateral)
  • If BTC drops rapidly, collateral received may be worth less than moonUSD burned
  • Smart contract risk (mitigated by ReentrancyGuard + Pausable)
PriceOracleRedemptionManager