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KeyStone supports settlement where the two legs live on different chains. The bond can be on Ethereum while the USDC payment is on Avalanche. Assets never bridge - they stay on their native chain, with LayerZero messaging coordinating between escrow contracts.

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How it works

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Key properties

  • Assets never bridge. The bond stays on Ethereum. The USDC stays on Avalanche. No wrapping, no synthetic representations.
  • Both legs settle or neither does. The atomicity gate on the coordinator chain verifies all locks before dispatching any releases.
  • Independent deposits. Neither party locks first. Both deposit independently to their local escrow. This eliminates the “who goes first” problem.
  • Permissionless timeout. If either deposit fails or the deadline passes, anyone can trigger timeout. Deposits are returned on all chains.

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Settlement flow

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1. Bilateral instruction submission

Both parties submit instructions as normal. The chain_id field in each party’s details and legs indicates which chain their assets are on: 
# Seller (bond on Ethereum, chain_id: 1)
curl -X POST https://api.keystoneos.xyz/v1/instructions \
  -H "Authorization: Bearer $SELLER_TOKEN" \
  -d '{
    "template_slug": "cross-chain-dvp",
    "role": "seller",
    "party": {
      "wallet_address": "0xSellerOnEthereum...",
      "chain_id": 1
    },
    "legs": [
      {
        "instrument_id": "0xBondTokenAddress",
        "quantity": "100",
        "direction": "deliver",
        "chain_id": 1
      },
      {
        "instrument_id": "0xUSDCOnAvalanche",
        "quantity": "50000",
        "direction": "receive",
        "chain_id": 43114
      }
    ]
  }'

# Buyer (USDC on Avalanche, chain_id: 43114)
curl -X POST https://api.keystoneos.xyz/v1/instructions \
  -H "Authorization: Bearer $BUYER_TOKEN" \
  -d '{
    "trade_reference": "KS-abc123...",
    "template_slug": "cross-chain-dvp",
    "role": "buyer",
    "party": {
      "wallet_address": "0xBuyerOnAvalanche...",
      "chain_id": 43114
    },
    "legs": [
      {
        "instrument_id": "0xBondTokenAddress",
        "quantity": "100",
        "direction": "receive",
        "chain_id": 1
      },
      {
        "instrument_id": "0xUSDCOnAvalanche",
        "quantity": "50000",
        "direction": "deliver",
        "chain_id": 43114
      }
    ]
  }'

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2. Settlement created across chains

After matching, the settlement is registered on the SettlementCoordinator (coordinator chain). The escrow contracts on each chain are informed of the expected deposits.

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3. Parties deposit to their local escrow

Each party deposits to the escrow contract on their own chain. The seller deposits bond tokens to the Ethereum escrow. The buyer deposits USDC to the Avalanche escrow.

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4. LayerZero messaging

Each escrow contract sends a lock confirmation to the SettlementCoordinator via LayerZero. The coordinator collects confirmations from all chains.

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5. Atomicity gate

The coordinator checks allLegsDeposited(). This only returns true when ALL legs on ALL chains have confirmed deposits. No releases happen until this condition is met.

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6. Release

The coordinator dispatches release instructions to all escrow contracts via LayerZero. Each escrow releases deposits to the intended recipients:
  • Bond tokens on Ethereum go to the buyer’s Ethereum address
  • USDC on Avalanche goes to the seller’s Avalanche address

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Timeout and rollback

If any deposit is missing when the deadline arrives: Timeout is permissionless. Any party can trigger it after the deadline, ensuring funds are never locked indefinitely regardless of KeyStone’s availability.

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Supported chains

Cross-chain settlement is a Phase 2 feature. Phase 1 operates on a single chain (Sepolia testnet, then L2 mainnet). The architecture supports any EVM-compatible chain with LayerZero integration. The coordinator chain can be any EVM chain - it is not tied to a specific blockchain.
Cross-chain settlement requires LayerZero messaging, which adds approximately 100,000 gas per message (4 messages for a 2-chain settlement: 2 lock confirmations + 2 release dispatches).