USDC and USDT are the dominant stablecoins pegged to \$1 with a total market capitalization of over \$300B and rising. Stablecoins make dollar value globally accessible with secure transfer and settlement. Yet in practice, these stablecoins experience periods of stress and de-pegging from their \$1 target, posing significant systemic risks. The behavior of market participants during these stress events and the collective actions that either restore or break the peg are not well understood. This paper addresses the question: who restores the peg?. We develop a dynamic, agent-based mean-field game framework for fiat-collateralized stablecoins, in which a large population of arbitrageurs and retail traders strategically interact across primary and secondary markets during a de-peg episode. The key advantage of this equilibrium formulation is that it endogenously maps market frictions into a market-clearing price path and implied net order flows, allowing us to attribute peg-reverting pressure by channel and to stress-test when a given infrastructure becomes insufficient for recovery. Using three historical de-peg events, we show that the calibrated equilibrium reproduces observed recovery half-lives and yields an order flow decomposition in which system-wide stress is predominantly stabilized by primary-market arbitrage. Finally, a quantitative sensitivity analysis identifies a non-linear breakdown threshold, beyond which a de-peg becomes markedly slower to reverse.

翻译：USDC和USDT是锚定1美元的主要稳定币，总市值超过3000亿美元且仍在增长。稳定币通过安全转账和结算，使美元价值在全球范围内可获取。然而在实践中，这些稳定币会经历压力期并偏离1美元目标，构成重大系统性风险。市场参与者在这些压力事件中的行为，以及恢复或打破锚定的集体行动尚不明确。本文探讨的问题是：谁在恢复锚定？我们为法币抵押型稳定币开发了一个基于主体的动态平均场博弈框架，在该框架中，大量套利者和零售交易者在脱锚事件期间，在初级市场和二级市场上进行策略性互动。该均衡公式的关键优势在于，它内生地将市场摩擦映射为市场出清价格路径和隐含的净订单流，使我们能够将锚定恢复压力按渠道归因，并测试在特定基础设施不足时恢复失效的临界条件。利用三个历史脱锚事件，我们证明标定后的均衡能重现观察到的恢复半衰期，并生成一种订单流分解，其中系统性压力主要由初级市场套利稳定。最后，定量敏感性分析识别出一个非线性崩溃阈值，超过该阈值后，脱锚反转将显著变慢。