In the Bitcoin ecosystem, on-chain arbitrage competition is intensifying, but a counterintuitive phenomenon is emerging: the highest bidder is not necessarily guaranteed to win the opportunity. Behind this lies a private ordering mechanism employed by mining pools (often termed 'dark pools'), which creates information asymmetry and grants certain traders preferential treatment, distorting the traditional 'highest fee wins' logic.
Currently, mining pools may deviate from public fee-based transaction ordering when constructing blocks, colluding with specific traders or miners to insert or delay transactions. This forms an over-the-counter environment akin to traditional finance's dark pools. This mechanism not only affects arbitrageurs' profit distribution but also raises concerns about Bitcoin's degree of decentralization and fairness. This article aims to outline the current state of on-chain arbitrage competition and uncover the information asymmetry caused by miners' private ordering.