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.