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Condition is designed to check the current value when a consumer wakes up. That's fine when state only moves forward, but it falls apart when transitions are fast. When the setter changes state, it calls notify_all(), which schedules wakeups for every waiting consumer. But in a single-threaded event loop, no consumer actually runs until the current coroutine yields. If the value changes again before that happens, consumers wake up and re-evaluate their predicate against the current value, not the value that triggered the notification. The predicate fails and the consumer goes back to sleep, potentially forever.
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