On the eve of a planned $6 billion bond buyback, the U.S. Treasury found itself in the uncomfortable position of having its reassurance read as alarm. Markets, which often judge not just the action but the proportion of the action, sent yields climbing on September 9th — a quiet verdict that the government's remedy did not match the scale of the ailment. It is an old tension in public finance: the moment an institution signals it is trying to hold a line, markets begin to test whether that line can actually hold.