Smart ContractsRedemptionManager

RedemptionManager

The Redemption Manager maintains a sorted queue of CDP positions ordered by interest rate. It enables moonUSD holders to redeem their tokens for BTC collateral at the current oracle price, providing a hard price floor for moonUSD.

Address (Sepolia): 0x78e7d3ce5f606c66db587a4d38ce808e60973da2a1b61276dfd5bf89f149ffb

How Redemptions Work

  1. Redeemer calls redeem(moonusd_amount, collateral_type)
  2. Manager traverses the sorted queue from head (lowest interest rate first)
  3. For each position: deducts debt, calculates collateral to return
  4. Redeemer receives collateral minus a redemption fee
  5. Affected borrowers keep their remaining collateral as compensation

Why Lowest Rate First?

Borrowers who set lower interest rates accept higher redemption risk. This creates a natural market for interest rates — if you want redemption protection, set a higher rate.

Redemption Fee

The fee uses an exponential decay base rate (inspired by Liquity):

baseRate_new = baseRate_old × e^(-0.5 × dt/hour) + 0.5 × redeemed_fraction
fee = baseRate × collateral_value
  • Base rate increases with each redemption and decays over time
  • Minimum fee: 0.5% (prevents free arbitrage)
  • Maximum fee: 5%

API Reference

redeem

Redeem moonUSD for collateral. Burns the caller’s moonUSD and transfers collateral.

fn redeem(ref self: TContractState, amount: u256, collateral_type: felt252)

Queue Management (CDPManager-only)

// Insert a new position into the sorted queue
fn insert(ref self: TContractState, position_id: u256, rate: u256)
 
// Remove a position from the queue
fn remove(ref self: TContractState, position_id: u256)
 
// Re-insert after rate change (remove + insert at new position)
fn re_insert(ref self: TContractState, position_id: u256, new_rate: u256)

Read Functions

fn get_redemption_fee(self: @TContractState, amount: u256) -> u256
fn get_base_rate(self: @TContractState) -> u256
fn get_sorted_head(self: @TContractState) -> u256        // position_id of lowest rate
fn get_queue_size(self: @TContractState) -> u256

Sorted List Implementation

The queue is a doubly-linked list stored on-chain:

Head (lowest rate) ⟷ ... ⟷ ... ⟷ Tail (highest rate)
  • Insert: O(n) worst case (walks list to find position), O(1) with hint
  • Remove: O(1) (pointer update)
  • Redemption traversal: O(k) where k = number of positions redeemed
StabilityPoolOverview