二値イベント契約で標準的な無期限先物の仕組みが機能しない理由

# 2605.10400


# Resolution-Aware Perpetual Futures on Binary Prediction Markets: Failure Modes and Mechanical Stress Tests Using Polymarket Data









We study whether crypto-style perpetual-futures mechanics can be applied to a binary event claim that ultimately pays 0 or 1. A synthetic long entered at price p0 with collateral xp0/L has terminal equity -xp0(1-1/L) when the claim pays 0, if the position survives to resolution without a top-up, close, or conversion. Thus any L > 1 creates an adverse-outcome account shortfall under these conditions, independent of the pre-resolution mark. We also derive a funding trilemma: basis-only funding loses relative force near a boundary, while uniform relative-basis correction requires unbounded transfers and conflicts with payer solvency or participation. We then apply a mechanical stress test to observed Polymarket paths from 21-27 April 2026. Of 61,087 enriched candidate markets, 13,298 pass the stated adequacy gates. Two structural diagnostics pass, but three of five pre-specified materiality tests fail. Dynamic margin and leverage compression pre-empt more observed paths than the static baseline, pooled drawdown falls by only 5.1 percent, and a staged halt reduces final-hour liquidations mechanically while leaving terminal shortfall incidence slightly worse. The contribution is a corrected non-portability analysis, a reusable observed-path replay design, and negative design lessons; the results do not establish equilibrium performance or deployment safety.