SLASettle

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Economic Model ​

All value accounting in SLASettle smart contracts is handled using exact 128-bit signed integers (i128) denominated in the token's smallest divisible unit. For Stellar Lumens (XLM) via the Stellar Asset Contract (SAC), amounts are denominated in stroops:

$$1\text{ XLM} = 10{,}000{,}000\text{ stroops}$$

The contracts execute zero floating-point operations, preventing rounding drift or precision loss.

Agreement Parameters ​

When invoking create_sla, the service provider configures four economic parameters:

rust
pub fn create_sla(
    env: Env,
    provider: Address,
    token: Address,
    bond_amount: i128,
    uptime_target_bps: u32,
    quorum_threshold: u32,
    penalty_per_breach: i128,
    beneficiary: Address,
) -> Result<u64, Error>
  1. bond_amount (i128):
    • Total initial collateral escrowed by the provider.
    • Must be strictly positive (bond_amount > 0).
    • Transferred from provider to the sla_vault contract during agreement creation.
  2. penalty_per_breach (i128):
    • Fixed compensation transferred to the beneficiary for each settled downtime round.
    • Must satisfy 0 < penalty_per_breach <= bond_amount. (Rejects InvalidAmount if penalty exceeds bond).
  3. quorum_threshold (u32):
    • Number of verified DOWN checks required to trigger settlement.
    • Must be strictly positive (quorum_threshold > 0).
  4. uptime_target_bps (u32):
    • Contractually recorded target in basis points (e.g., 9990 represents 99.90%).
    • Stored on-chain for verification and UI presentation. Settlement evaluation occurs per round.

Settlement Payout Mechanics ​

When trigger_settlement is executed for a round that meets quorum:

rust
let balance_key = DataKey::BondBalance(sla_id);
let balance: i128 = env.storage().persistent().get(&balance_key).unwrap_or(0);

let payout = if config.penalty_per_breach < balance {
    config.penalty_per_breach
} else {
    balance
};

if payout <= 0 {
    return Err(Error::BondExhausted);
}

token_client.transfer(&env.current_contract_address(), &config.beneficiary, &payout);
env.storage().persistent().set(&balance_key, &(balance - payout));

Full vs. Partial Settlements ​

  • Standard Settlement: If current_balance >= penalty_per_breach, the contract transfers exactly penalty_per_breach to the beneficiary.
  • Partial Settlement (Exhaustion): If multiple breaches have depleted the bond such that $0 < \text{current_balance} < \text{penalty_per_breach}$, the contract transfers all remaining funds (balance) to the beneficiary.
  • Depleted Bond: If current_balance == 0, settlement fails with Error::BondExhausted. The provider must top up the bond to restore settlement coverage.

Live Testnet Evidence ​

Current Testnet SLA #2 (Verified Live 2026-10-07) ​

During the Phase 7 live verification on the Protocol 28 Testnet deployment:

  • Contract: sla_vault (CDBFPYHJNYSIFXSMXF3BBDWPKHRS7SJFFEKMQ5WJXYTBMD4LFAG2CHLN)
  • Initial Bond: 10,000,000 stroops (1.0 XLM)
  • Penalty Per Breach: 1,000,000 stroops (0.1 XLM)
  • Quorum Threshold: 3 watchers
  • Top-Up Executed: 5,000,000 stroops (0.5 XLM) via Freighter, increasing balance to 15,000,000 stroops.
  • Cancellation & Withdrawal: SLA #2 was cancelled and all 15,000,000 stroops were returned to the provider's wallet.

Collateral Management ​

Topping Up Collateral ​

  • Function: top_up_bond(caller, sla_id, amount)
  • Authorization: Restricted strictly to the original provider (config.provider == caller).
  • Timing: Can be called at any time to maintain sufficient coverage against future breaches.
  • Invariance: Can top up any valid SLA.

Reclaiming Collateral ​

  • Function: cancel_sla(caller, sla_id) followed by withdraw_remaining_bond(caller, sla_id)
  • Authorization: Restricted strictly to the original provider.
  • Security Control: Providers cannot withdraw collateral while an SLA is Active. The agreement must first transition to Cancelled, signaling to the beneficiary and watchers that the agreement is concluded.
  • Zero-Balance Protection: If remaining balance is zero, withdraw_remaining_bond rejects with Error::InvalidAmount.

Protocol Fee Policy ​

  • Zero Protocol Tax: Neither sla_vault nor watcher_registry levies protocol fees, transaction taxes, or admin cuts.
  • 100% of escrowed collateral is disbursed either to the beneficiary (as penalties) or returned to the provider (upon withdrawal).