A bug that seems to vanish when you observe or debug it—often timing, concurrency, or observer-effect issues; AI-assisted debugging still needs reproduction discipline.
The name is a play on Heisenberg’s uncertainty idea: observation changes state. Heisenbugs appear in races, GC pauses, cache coherency, and flaky networks. LLMs may suggest plausible causes—treat them as hypotheses validated with distributed tracing, logging, and chaos engineering.
Common misspelling
Teams sometimes write “Heisenburg”; the correct term is Heisenbug.