When collateral prices plummet, the theoretical mechanics of liquidation matter far less than whether they work in practice. Aave's governance has grappled with this question repeatedly regarding wrapped staked Ethereum (wstETH), a major collateral on the protocol. Rather than declare victory or sound alarms, the protocol's risk framework has evolved to ask four rigorous, sequential questions that reveal whether liquidations would actually execute during a real crisis.
The first requirement is obvious but often overlooked: can the oracle even report the crash? If price feeds cannot move far enough to trigger liquidations, no amount of liquidity or incentive structure matters. The second challenge is synchronization—how much debt must borrowers repay simultaneously? Liquidating five million dollars differs categorially from liquidating five hundred million. The third is capital availability: does sufficient liquidity exist at the moment liquidators need to post cash? Finally, the bonus—the discount liquidators receive for absorbing bad debt—must be attractive enough to actually incentivize participation. These four filters form a decision tree where failure at any stage breaks the entire mechanism, and where "indeterminate" results are honest admissions that current data cannot answer the question.
Testing wstETH on Ethereum mainnet at block 25,780,402 reveals why this rigor matters. The oracle passes, able to report price movements within tested parameters. Simultaneous repayment obligations at the 99th percentile of stress scenarios remain manageable on paper. The liquidation bonus structure appears adequate for the scale examined. Yet the critical third test—whether actual capital would be available for repayment at the moment of crisis—returns indeterminate. This is not a failing grade; it signals that the evidence simply cannot yet confirm what happens when nested leverage, market dislocations, and capital flight converge. Crucially, the framework identifies who could resolve this gap: market makers, exchange liquidity managers, or those with visibility into true off-chain capital flows.
This methodology prevents the silent drift toward systemic risk that occurs when assumptions become embedded in results. By naming indeterminate outcomes rather than filling blanks with convenient numbers, Aave's stress-testing approach creates accountability for the empirical claims underlying major collateral decisions. The implications extend beyond wstETH—any collateral that fails to fully pass these four questions becomes a candidate for tighter risk parameters or enhanced monitoring, shifting the burden of proof where it belongs.