# Transaction Builders

Transaction builders provide a fluent API for constructing `TransactionV1` (Casper 2.x) transactions.

## Available Builders

| Builder | Use Case |
|---|---|
| [`NativeTransferBuilder`](/builders/NativeTransferBuilder) | Send CSPR to another account |
| [`NativeDelegateBuilder`](/builders/NativeDelegateBuilder) | Stake CSPR with a validator |
| [`NativeUndelegateBuilder`](/builders/NativeUndelegateBuilder) | Unstake CSPR from a validator |
| [`NativeRedelegateBuilder`](/builders/NativeRedelegateBuilder) | Move stake to a different validator |
| [`ContractCallBuilder`](/builders/ContractCallBuilder) | Call a smart contract entry point |
| [`SessionBuilder`](/builders/SessionBuilder) | Deploy and run WASM session code |

## General Pattern

All builders follow the same pattern:

```ts
const transaction = new SomeBuilder()
  .from(senderPublicKey)    // required: who is sending
  ./* ...chain options... */
  .chainName('casper')      // required: network name
  .payment(100_000_000)     // optional: gas payment in motes
  .ttl('30m')               // optional: time to live
  .timestamp(Date.now())    // optional: creation time
  .build();                 // returns Transaction

transaction.sign(privateKey);  // sign before submitting

const result = await rpcClient.putTransaction(transaction);
```

## Common Builder Options

| Method | Type | Default | Description |
|---|---|---|---|
| `.from(key)` | `PublicKey` | required | Transaction initiator |
| `.chainName(name)` | `string` | required | `'casper'` or `'casper-test'` |
| `.payment(motes)` | `number` | varies | Gas payment in motes |
| `.ttl(duration)` | `string` | `'30m'` | Time-to-live (e.g. `'1h'`, `'2m'`) |
| `.timestamp(ms)` | `number` | `Date.now()` | Creation timestamp |

## Signing

```ts
// Single signer
transaction.sign(privateKey);

// Multi-sig: add additional approvals
transaction.sign(cosignerPrivateKey);

// External signer (hardware wallet)
const hashBytes = transaction.getTransactionV1()!.hash.toBytes();
const signature = await hardwareWallet.sign(hashBytes);
transaction.setSignature(signature, signerPublicKey);
```

## Submitting

```ts
const result = await rpcClient.putTransaction(transaction);
console.log('Hash:', result.transactionHash);
```