Vaults

ERC-4626 BTC yield strategies with curator-managed deployment

Vaults

Sable offers 6 distinct BTC yield strategies deployed as ERC-4626 tokenized vaults on StarkNet. Users deposit WBTC and receive share tokens representing their proportional claim on the vault’s growing assets.

Vault Catalog

Vault	Strategy	Risk	Description
Sable Sentinel	Pure Lending	1 (Low)	Supply WBTC to Vesu PRIME pool. Simplest, safest strategy.
Sable Citadel	Staked BTC + Lending	2 (Low-Med)	WBTC → Endur xWBTC liquid staking → supply to Vesu for dual yield.
Sable Trident	Recursive Staking	3 (Med)	3x recursive WBTC staking loop on Endur for amplified staking rewards.
Sable Delta Neutral	BTC-USDC Spread	4 (Med-High)	Deposit WBTC as collateral → borrow USDC → deploy USDC to yield → earn spread.
Sable Turbo	USDC Leverage Loop	5 (High)	Leverage-loop WBTC collateral on Vesu: deposit → borrow USDC → swap to WBTC → re-deposit.
Sable Apex	Multi-Strategy Max Yield	5 (High)	40% leverage lending + 35% Ekubo LP + 25% Endur staking. Maximum diversified yield.

ERC-4626 Vault Mechanics

Every Sable vault implements the ERC-4626 tokenized vault standard:

┌──────────────────────────────────────────────────┐
│                  ERC-4626 VAULT                  │
│                                                  │
│  deposit(assets) ──► mint(shares)                │
│  withdraw(assets) ◄── redeem(shares)             │
│                                                  │
│  share_price = total_assets() / total_supply()   │
│                                                  │
│  As strategy earns yield:                        │
│    total_assets ↑  →  share_price ↑              │
│    Each share redeems for more WBTC over time    │
└──────────────────────────────────────────────────┘

Core ERC-4626 Functions

• deposit(assets, receiver) — Deposit WBTC, receive yvBTC shares
• withdraw(assets, receiver, owner) — Burn shares, receive WBTC
• total_assets() — Returns total WBTC managed (deployed + idle)
• convert_to_shares(assets) / convert_to_assets(shares) — Conversion helpers

Deposit Flow

1. Approve WBTC

   User approves the vault contract to spend WBTC tokens.

   WBTC.approve(vault_address, deposit_amount)
   
2. Deposit to Vault

   Call vault.deposit() to mint yvBTC shares.

   vault.deposit(amount, receiver)
   

   Vault mints share tokens to receiver based on current share price.

3. Curator Deploys Idle Funds

   The curator calls deploy_idle() via the /api/curator endpoint to deploy WBTC into the strategy.

   Idle WBTC sitting in the vault does not earn yield until deployed by the curator.

Withdraw Flow

1. Request Withdrawal

   User calls vault.withdraw() specifying the amount of WBTC to receive.

   vault.withdraw(wbtc_amount, receiver, owner)
   
2. Strategy Unwind

   Vault automatically unwinds positions to free up WBTC:

   • Sentinel: Withdraw from Vesu PRIME
   • Citadel: Unstake xWBTC, swap to WBTC
   • Trident: Unwind recursive loop (may use flash loans)
   • Delta Neutral: Repay USDC debt, withdraw collateral
   • Turbo: Unwind leverage loop via flash loan
   • Apex: Exit LP, unstake, repay debt atomically
3. Receive WBTC

   WBTC is transferred to receiver, share tokens are burned.

Curator Pattern

The curator (contract owner) manages strategy execution. Idle WBTC is deployed to yield protocols via:

// API endpoint: /api/curator
POST /api/curator
{
  "vault_id": "sentinel",
  "action": "deploy_idle"
}

Deployment Strategies by Vault

Sentinel

Pure Vesu PRIME Lending

1. Read idle WBTC balance
2. Supply WBTC to Vesu PRIME pool
3. Earn supply APY + BTCFi STRK rewards

Contract: 0x04ec7fdb1679450fb88eae9facc439a46be4ddeba628211e269a7467f6e0971b

Citadel

Staked BTC + Lending

1. Stake WBTC on Endur → receive xWBTC
2. Supply xWBTC to Vesu Re7 xBTC pool
3. Earn staking yield + lending APY + STRK

Contract: 0x077ad8d0fe4b946cedc02eb8eb61a64e85bcde802a83e879e8c68fed8b9b130e

Trident

3x Recursive Staking Loop

1. Stake WBTC → xWBTC on Endur
2. Supply xWBTC as collateral on Vesu Re7
3. Borrow WBTC against xWBTC
4. Re-stake borrowed WBTC (repeat 3x)
5. Amplified staking rewards via leverage

Contract: 0x058aadc9db62700de03d89a7c8f2952851d94e75f854cc6a340ef92d00cd3fb8

Delta Neutral

BTC-USDC Yield Spread

1. Supply WBTC as collateral on Vesu Re7
2. Borrow USDC at 50% LTV
3. Deploy USDC to Vesu Prime USDC pool
4. Earn spread (USDC yield > borrow cost)

Contract: 0x06c8779ee7ed14b35ac5c6eae5dc721cc3e8104a65ffef4b5252babc407a1012

Turbo

USDC Leverage Loop

1. Supply WBTC to Vesu
2. Borrow USDC
3. Swap USDC → WBTC via AVNU
4. Re-supply WBTC (repeat 3x)
5. Leveraged BTC exposure + amplified yield

Contract: 0x05f3d02005027296ccfb90574544b941d9ddc55c673e6fe0e92cb6f07e68d1f7

Apex

Multi-Strategy Maximum Yield

1. Split deposit 3 ways:
   • 40% → Vesu leveraged lending (3x loop)
   • 35% → Ekubo WBTC/ETH concentrated LP
   • 25% → Endur BTC staking
2. Auto-unwind on withdraw via flash loan

Contract: 0x071eb7fc3a912c0ee85b1dc795e29fd77ff4203a33384a1171dd4fcb7c7b3df9

Income Streams

Source	Vaults Using It	Description
Vesu Lending APY	Sentinel, Citadel, Trident, Turbo, Apex	Interest from borrowers on Vesu
Endur xWBTC Staking	Citadel, Trident, Apex	Liquid staking yield on BTC
BTCFi Season STRK	All	100M STRK incentive program rewards
Ekubo LP Fees	Apex	Concentrated liquidity market making fees
Borrowing Spread	Delta Neutral, Turbo	Earn more on deployed capital than borrowing cost
Leverage Amplification	Trident, Turbo	Multiply base yield via recursive positions

Share Price Growth

The share price increases as yield accrues:

Example: Sentinel Vault
  Initial deposit: 1.0 WBTC → 1.0 yvBTC (share price = 1.0)
  
  After 30 days at 8% APY:
  Total assets: 1.00657 WBTC
  Share price: 1.00657 WBTC per yvBTC
  
  Redeem 1.0 yvBTC → receive 1.00657 WBTC
  Profit: 0.00657 WBTC

Vault Contracts

Sentinel

Pure WBTC lending on Vesu PRIME. Lowest risk, steady yield.

Citadel

Staked BTC + lending. Dual yield from Endur staking and Vesu.

Trident

3x recursive staking loop. Amplified staking rewards.

Delta Neutral

BTC-USDC spread strategy. Earn yield delta between USDC and borrowing.

Turbo

USDC leverage loop. High risk, maximum leverage.

Apex

Multi-strategy diversification. 3-way split for maximum yield.

Flash Loan Unwind

Complex strategies (Turbo, Trident, Apex) may require flash loans for withdrawal:

Withdrawal Flow with Flash Loan:
  1. Borrow WBTC via flash loan
  2. Repay all debt positions
  3. Withdraw collateral from protocols
  4. Repay flash loan
  5. Return remaining WBTC to user
  
  ✓ Atomic — no partial state
  ✓ No user funds at risk

Flash loan withdrawals may fail in extreme market conditions (low DEX liquidity, high borrow rates). Always monitor your position health.

Risk Levels

Conservative (1-2)

Vaults: Sentinel, Citadel

• No leverage or low leverage
• Simple, battle-tested strategies
• Lower APY, higher safety
• Recommended for risk-averse users

Moderate (3-4)

Vaults: Trident, Delta Neutral

• Moderate leverage (2-3x)
• Multiple protocol dependencies
• Balanced risk/reward
• Requires monitoring

Aggressive (5)

Vaults: Turbo, Apex

• High leverage (3-4x)
• Complex multi-step strategies
• Maximum APY potential
• High liquidation risk

Next Steps

Deposit into a Vault

Step-by-step guide to your first vault deposit

Understanding APY

Learn how vault APY is calculated

Vault Contracts

Technical documentation for each vault

Risk Management

Best practices for vault safety