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Overview

Endur is a liquid BTC staking protocol on StarkNet that allows users to stake WBTC and receive xWBTC, a liquid staking token that accrues staking rewards while remaining transferable and usable as collateral.
Endur powers 3 out of 6 Sable vaults with liquid BTC staking yield.

What is Endur?

Endur enables liquid staking for Bitcoin on StarkNet:
  • Stake WBTC → receive xWBTC (liquid staking token)
  • xWBTC automatically accrues staking rewards
  • xWBTC is fully composable — use it in DeFi while earning rewards
  • Unstake anytime — redeem xWBTC for WBTC + accrued rewards

Key Features

  • Liquid Staking Token (xWBTC): Freely transferable, usable as collateral
  • Auto-compounding: Staking rewards automatically accrue to xWBTC holders
  • No lock-up period: Unstake whenever you want
  • BTCFi incentives: Eligible for StarkNet’s 100M STRK BTCFi Season rewards

How Sable Integrates with Endur

Sable leverages Endur’s liquid staking to generate amplified BTC yield across multiple vault strategies.

Citadel Vault

Strategy: Staked BTC + Lending
Citadel Flow:
  1. User deposits WBTC
  2. Vault stakes WBTC on Endur → receives xWBTC
  3. Vault supplies xWBTC to Vesu Re7 xBTC pool
  4. Dual yield:
     ├── Endur staking rewards (xWBTC appreciation)
     └── Vesu lending APY + BTCFi STRK rewards
Yield Sources:
  • Endur xWBTC staking: ~3-5% APY
  • Vesu Re7 xBTC lending: ~4-6% APY
  • BTCFi STRK incentives: ~8-12% APR
  • Total: ~15-23% APY
Risk Level: 2 (Low-Medium)

Trident Vault

Strategy: Recursive Staking (3x Loop)
Trident Flow:
  1. User deposits WBTC
  2. Loop 1: Stake WBTC → xWBTC
  3. Loop 2: Stake xWBTC → xWBTC (recursive)
  4. Loop 3: Stake xWBTC → xWBTC (recursive)
  5. Result: 3x amplified staking yield
How Recursive Staking Works:
Base staking:     100 WBTC @ 4% APY = 4 WBTC/year
Recursive staking: 100 WBTC @ 4% × 3 loops = 12 WBTC/year
By recursively staking xWBTC (which itself accrues rewards), Trident amplifies the base staking yield. Risk Level: 3 (Medium)
Trident’s recursive loop is implemented on-chain via the vault’s deploy_idle() function, which executes 3 staking iterations.

Apex Vault

Strategy: Multi-Strategy Max Yield (25% Endur Allocation)
Apex Allocation:
  ├── 40% Vesu leverage lending
  ├── 35% Ekubo LP (WBTC-ETH or WBTC-USDC)
  └── 25% Endur staking
Apex allocates 25% of deposits to Endur staking for diversified yield. Risk Level: 5 (High)

xWBTC Token Mechanics

xWBTC is a rebasing liquid staking token.

How It Works

  1. Stake WBTC:
    User deposits 1 WBTC → Receives ~1 xWBTC
    
  2. Accrue Rewards:
    xWBTC balance grows over time as staking rewards accrue
    
  3. Unstake:
    User redeems 1.05 xWBTC → Receives 1.05 WBTC
    (Original 1 WBTC + 0.05 WBTC staking rewards)
    

Composability

xWBTC can be used in DeFi protocols:
  • Collateral: Supply to Vesu for lending (Citadel strategy)
  • LP: Provide liquidity in AMMs
  • Transfers: Send to other addresses
  • All while earning staking rewards

Contract Addresses

Endur contract addresses are not publicly listed in the source code. Refer to Endur’s official documentation for current contract addresses.

Integration Pattern

Sable vaults interact with Endur via standard staking functions.

Stake WBTC

// Simplified Cairo pseudocode

#[external(v0)]
fn stake_on_endur(amount: u256) {
    // Approve WBTC to Endur staking contract
    wbtc.approve(endur_staking, amount);
    
    // Stake WBTC → receive xWBTC
    let xwbtc_received = endur_staking.stake(amount);
    
    // xWBTC now accrues staking rewards automatically
}

Unstake xWBTC

#[external(v0)]
fn unstake_from_endur(xwbtc_amount: u256) {
    // Redeem xWBTC for WBTC + rewards
    let wbtc_received = endur_staking.unstake(xwbtc_amount);
    
    // wbtc_received includes original stake + accrued rewards
}

Recursive Staking (Trident)

// Trident vault's 3x recursive staking loop

#[external(v0)]
fn deploy_idle() {
    let idle_wbtc = wbtc.balance_of(self);
    
    // Loop 1: Stake WBTC → xWBTC
    wbtc.approve(endur, idle_wbtc);
    let xwbtc_1 = endur.stake(idle_wbtc);
    
    // Loop 2: Stake xWBTC → xWBTC (recursive)
    xwbtc.approve(endur, xwbtc_1);
    let xwbtc_2 = endur.stake(xwbtc_1);
    
    // Loop 3: Stake xWBTC → xWBTC (recursive)
    xwbtc.approve(endur, xwbtc_2);
    let xwbtc_3 = endur.stake(xwbtc_2);
    
    // Final xWBTC balance earns 3x amplified rewards
}

Which Sable Features Use Endur?

Citadel Vault

Dual Yield StrategyStake WBTC → xWBTC, then supply xWBTC to Vesu for lending yield.
  • Risk: 2/5
  • Yield: Staking + Lending + STRK

Trident Vault

3x Recursive StakingTriple-stack staking via recursive loops to amplify base staking APY.
  • Risk: 3/5
  • Yield: 3x Staking rewards

Apex Vault

25% Endur AllocationPart of diversified max-yield strategy.
  • Risk: 5/5
  • Yield: Blended with lending + LP

Yield Amplification Math

Standard Staking (Baseline)

Deposit:  100 WBTC
APY:      4%
Yield:    4 WBTC/year

Citadel (Staking + Lending)

Deposit:  100 WBTC
Staking:  4% APY (xWBTC appreciation)
Lending:  5% APY (Vesu Re7 xBTC)
BTCFi:    10% APR (STRK rewards)
Total:    ~19% APY
Yield:    19 WBTC/year

Trident (3x Recursive)

Deposit:  100 WBTC
Loop 1:   4% APY
Loop 2:   4% APY on xWBTC (recursive)
Loop 3:   4% APY on xWBTC (recursive)
Total:    ~12% APY (3x amplification)
Yield:    12 WBTC/year
Actual APYs vary based on Endur staking utilization, Vesu pool rates, and BTCFi STRK incentive distributions.

Frontend Integration

Sable’s vault pages display Endur staking yield as part of the APY breakdown.
// From: ~/workspace/source/src/lib/api/vaults.ts

import { fetchVesuXwbtcBtcFi } from "@/lib/api/vesu";

const RE7_XBTC_POOL = "0x03a8416bf20d036df5b1cf3447630a2e1cb04685f6b0c3a70ed7fb1473548ecf";

// Fetch Endur staking yield (embedded in Vesu Re7 xBTC pool)
const xwbtcBtcFi = await fetchVesuXwbtcBtcFi(RE7_XBTC_POOL);

// Citadel APY breakdown:
const citadelApy = {
  endurStaking: 4.0,        // Endur xWBTC staking
  vesuLending: 5.2,         // Vesu Re7 xBTC lending
  btcFiStrk: xwbtcBtcFi,    // BTCFi STRK rewards
  total: 4.0 + 5.2 + xwbtcBtcFi,
};

Risk Considerations

Citadel (Low-Medium Risk)

  • Smart contract risk: Endur + Vesu
  • xWBTC depeg risk: Minimal (backed 1:1 by WBTC)
  • Liquidation risk: None (no borrowing)

Trident (Medium Risk)

  • Smart contract risk: Endur recursive loops
  • Complexity risk: Multi-level staking increases attack surface
  • Liquidation risk: None (no borrowing)

Apex (High Risk)

  • Smart contract risk: Endur + Vesu + Ekubo
  • Leverage risk: 40% allocation uses leverage
  • IL risk: 35% allocation exposed to impermanent loss
  • Liquidation risk: Moderate (leveraged position)

External Resources

Endur Documentation

Official Endur protocol documentation

Endur App

Endur liquid staking interface

Integration Source Code:
  • Citadel: ~/workspace/source/contracts/src/citadel.cairo
  • Trident: ~/workspace/source/contracts/src/trident.cairo
  • Apex: ~/workspace/source/contracts/src/apex.cairo

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