> ## Documentation Index
> Fetch the complete documentation index at: https://docs.utexo.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Solana Settlement

> Settle Utexo swaps on Solana using unified vault PDAs, packed DEX instructions, and co-signed deposit, fulfill, and withdraw transactions.

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.

## Onboarding

A protocol administrator registers each resolver in the `ProtocolState` PDA with:

* Executor/admin authority `Pubkey`
* Authorized deposit and withdraw addresses

## Accounts

### Unified vault PDA

```text theme={null}
seeds = ["vault", token_mint]
```

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

### `EscrowCheck` PDA

```text theme={null}
seeds = ["escrow", order_hash]
```

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

### `FulfilledIntent` PDA

```text theme={null}
seeds = ["fulfilled", intent_id]
```

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.

## Cross-chain swap

### Deposit

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

### Fulfill

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

### Withdraw

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

## Horizontal packing with DEX

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

### Deposit with DEX

```text theme={null}
deposit_dex_start
  -> resolver DEX instructions
deposit_dex_finish
```

<Warning>
  Intermediary DEX instructions must not reference the user's public key.
</Warning>

### Fulfill with DEX

```text theme={null}
fulfill_start
  -> resolver instructions
fulfill_finish        // or fulfill_finish_native for native SOL
```

Use `fulfill_finish_native` when paying out native SOL.

## Single-chain atomic swap

* **Signers:** user + `resolver_deposit_address` + `backend_signer`.

### DEX path

```text theme={null}
swap_start
  -> resolver instructions
swap_finish           // or swap_finish_native for native SOL
```

## 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.