How a Laptop Sleep Cycle Exposed a Critical Python Timeout Clock Bug

A software developer spent 48 hours debugging a worker process that appeared idle while its job deadline silently expired. The root cause was the use of Python's time.time() function to calculate timeout budgets, which relies on wall-clock time that can jump forward or backward — for example, when a laptop wakes from sleep. This caused one job to return immediately after a sleep event and another to run far beyond its intended time limit, while unit tests passed normally since they never triggered clock changes. A log entry showing a remaining budget of -1842.7 seconds was an early clue, but was initially dismissed as a formatting error rather than a clock anomaly. The fix involves replacing time.time() with time.monotonic(), which uses a forward-only clock suitable for measuring elapsed durations.