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Solana settlement uses program-derived addresses (PDAs) and horizontally packed instructions. No Executor or Fulfillment contract is deployed; resolvers interact directly with the Utexo program.

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Onboarding

A protocol administrator registers each resolver in the ProtocolState PDA with:
  • Executor/admin authority Pubkey
  • Authorized deposit and withdraw addresses

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Accounts

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Unified vault PDA

Pools escrowed tokens of the same mint in one vault. Deposits increase its balance; withdrawals, refunds, and fulfillments decrease it.

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EscrowCheck PDA

Stores order, intent, resolver, deposit authority, user, mint, amount, secret hash, nonce, and deadline.

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FulfilledIntent PDA

Provides replay protection for fulfillment. The PDA is closable after a seven-day grace period to reclaim rent through the single or batch close instructions.

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Cross-chain swap

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Deposit

  • Signers: user + resolver_deposit_address.
  • Uses the accounts and parameters supplied in the co-signed deposit transaction.

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Fulfill

  • Signers: caller_authority + backend_signer.
  • Fulfillment amount must be in [min_amount, min(max_amount, resolver_max_amount)].

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Withdraw

  • Signer: resolver_withdraw_address.
  • Requires the full order and revealed secret. Closes the EscrowCheck PDA on success.

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Horizontal packing with DEX

Solana settlements pack protocol instructions around resolver-supplied DEX instructions inside a single atomic transaction. Ordering is strict.

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Deposit with DEX

Intermediary DEX instructions must not reference the user’s public key.

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Fulfill with DEX

Use fulfill_finish_native when paying out native SOL.

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Single-chain atomic swap

  • Signers: user + resolver_deposit_address + backend_signer.

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DEX path

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Fast refund

Fast refund is co-signed by backend_signer and resolver_deposit_address. The resolver signer must match the resolver_deposit_authority stored in the EscrowCheck PDA.