cross-chain MEV

Maximal extractable value is the profit a block producer (or a searcher paying one) can capture by choosing how to order, include, or censor transactions. Cross-chain MEV — also called cross-domain MEV — is the same idea stretched across two or more chains at once: value that exists only because of price differences, timing gaps, or dependencies that span multiple ledgers, capturable by someone who can coordinate actions on each.

The clearest example is arbitrage. If ETH trades cheaper on one chain's DEX than on another's, a searcher buys on the cheap chain and sells on the expensive one, pocketing the spread. Unlike same-chain arbitrage, this trade is not atomic: the two legs live on different chains with their own block times and finality, so there is bridging latency and inventory risk between them. Searchers manage this by pre-positioning capital on both chains (so they trade locally and rebalance later) rather than literally bridging mid-trade, which would be far too slow.

Cross-chain MEV matters because it ties the economic security and ordering of otherwise-independent chains together, and it sharpens the centralizing pressure of MEV. An actor who is the builder or sequencer on several domains at once can coordinate orderings to extract value no single-chain participant could, which is a worrying force toward a few dominant cross-domain operators. Shared sequencing, where one sequencer orders blocks for many rollups, is partly a response — it could enable atomic cross-rollup transactions but also concentrates exactly this cross-domain extraction power.