The Bug That Only Appears When Nobody Is Watching (opens in new tab)

In 2011, a team at a mid-sized financial services company spent six weeks hunting a bug that would have been unremarkable except for one property: it disappeared whenever they tried to observe it. The application, a high-throughput order-processing system, would occasionally drop transactions. Not crash. Not log an error. Just quietly lose work, the way a conversation gets interrupted and both people politely pretend the sentence was finished. The bug was intermittent, customer-reported, and ...