Do Private Transaction Relays Guarantee Zero Front-Running Risk?

No, private transaction relays significantly reduce, but do not guarantee, zero front-running risk. While they prevent general mempool bots from seeing the transaction, the validator or block builder who receives the private transaction still has knowledge of the pending order.

This means the validator itself could potentially front-run the transaction, a practice known as 'validator front-running' or 'miner extracted value' (MEV). Solutions like Proposer-Builder Separation (PBS) and encryption aim to mitigate this residual risk.