Custom Ordering Rules

Fairseq defaults to FIFO ordering, but you can define custom policies that better match your protocol. All rules must be deterministic and auditable.

Built-in rules

FIFO (default)

let config = Config {
    ordering_rule: OrderingRule::Fifo,
    ..Default::default()
};

Priority fee

let config = Config {
    ordering_rule: OrderingRule::PriorityFee,
    ..Default::default()
};

Custom rule example

let config = Config {
    ordering_rule: OrderingRule::Custom(Box::new(|a, b| {
        // Example: prioritize highest fee, then fallback to timestamp.
        a.fee.cmp(&b.fee).then(a.timestamp.cmp(&b.timestamp))
    })),
    ..Default::default()
};

Best practices

• Version your rules and store a policy ID in proof metadata.
• Keep rule inputs minimal to simplify audits.
• Reuse the same ordering implementation across prover/verifier environments.

Common pitfalls

• Non-deterministic inputs (wall clock variance, randomness).
• Hidden tie-breakers that are not captured in metadata.