Transaction Fields

Every transaction submitted to the Bullet exchange is wrapped in an UnsignedTransaction containing three components: the call message, a uniqueness value, and transaction details. This guide covers the uniqueness and details fields.

Uniqueness

The UniquenessData field prevents transaction replay. Bullet supports two modes:

#![allow(unused)]
fn main() {
enum UniquenessData {
    Nonce(u64) = 0,
    Generation(u64) = 1,
}
}

Generation mode (recommended)

The uniqueness value can be whatever you want — it just needs to be unique per user within a block window (~5-6 seconds). We recommend using microsecond timestamps.

• No need to track or increment a counter
• Multiple transactions can be in-flight concurrently

Best practice: use SystemTime::now() in microseconds. Avoid reusing values — if you submit multiple transactions in a tight loop, ensure each is distinct.

Nonce mode

Use Nonce(u64) for strict sequential ordering. The nonce must be exactly current_nonce + 1 for the credential. This mode is simpler but only allows one in-flight transaction at a time.

TxDetails

#![allow(unused)]
fn main() {
struct TxDetails {
    max_priority_fee_bips: u64,
    max_fee: Amount,
    gas_limit: Option<[u64; 2]>,
    chain_id: u64,
}
}

These fields are required in every transaction. We recommend using the values below.

Gas model

Bullet uses a 2D gas model with separate compute and storage dimensions. The gas_limit field caps how much of each resource a transaction may consume.

Paymaster

Gas fees are covered by a paymaster — users do not pay gas out of pocket. The fields are still required for transaction validity.

Recommended Values

See the default_tx_details helper for a ready-to-use implementation.