Citation

Adadurov, A., Barseghyan, S., Chtepine, A., Eloranta, A., Sebyakin, A., Valitov, A. (nuconstruct). “Imperfect Commitment in Maximal Extractable Value Auctions.” arXiv:2605.22667v2 [cs.GT] (26 May 2026). Same team / dataset as Paper: Open vs. Sealed — Auction Format Choice for MEV.

Core Question

Builders run sealed auctions among searchers, but nothing in the protocol forces a builder to honor the auction outcome after seeing the submitted bundles. Having observed every bundle’s payload, a builder can replicate the winning searcher’s strategy, replace their tx, and capture the MEV directly. This is the commitment problem — distinct from (and orthogonal to) the auction-format question of the prior paper.

Model

  • Builder defects with probability δ ∈ [0,1]; on defection, replicates a type-specific fraction γ(type) of the winning opportunity, types ∈ {sandwich, naked arb, liquidation, backrun}.
  • δ=0 fully committed (winner pays own bid); δ=1 always defects (replicates whenever γ·v exceeds the winning bid). Standard revert protection means the searcher’s tx doesn’t execute and no payment is collected on defection.
  • Anticipating this, searchers choose between a risky first-price bid and a safe deterrence bid b = γ(type)·v that makes defection unprofitable → piecewise equilibrium: below a type-specific cutoff bid as in standard FPSB; above it, bid enough to deter the builder.
  • Maps to the corrupt-auctioneer literature: the builder’s information advantage becomes a manipulation lever, not just a price-discovery tool.

Empirical Findings (libmev dataset)

  • γ̂(type) estimated from right-tail bribe plateaus; observed auction revenue decomposed against the surplus a defecting builder could capture.
  • Sharp heterogeneity by MEV type:
    • Sandwiches — already highly competitive; bribes near full extracted value → little extra for a defecting builder (and mechanically the most replicable).
    • Naked arbitrage & liquidations — large gaps between observed bids and replication value → most exposed to builder defection (reproducible only in part, but under-bid).
  • A complementary channel: builders integrated with a searcher turn defection into selective disclosure to a favored bidder (noted as an extension).

Key Takeaway

A credible MEV auction is not primarily a question of auction format — it requires constraints on the builder’s ability to use observed bid/payload information ex post.

Connection to Wiki

See Also