Wall Street and global financial regulators, trying to squash the lingering perception that banks remain “too big to fail,” are looking to an obscure change in derivatives contracts to solve the problem, Bloomberg News reported yesterday. The main industry group for the $700 trillion global swaps market is rewriting international protocols to impose a “stay” or pause designed to prevent trading partners from calling in collateral all at once when a bank nears failure. U.S. and international banking regulators are considering making use of the new protocols mandatory. The International Swaps and Derivatives Association is aiming to release the revised contract guidelines by November. The change is designed to prevent a recurrence of one of the most vexing problems revealed by the 2008 financial crisis: When Lehman Brothers Holdings Inc. failed, counterparties trying to unwind derivatives contracts touched off a panic that triggered a worldwide credit crisis.