Hidden bug let minority nodes fake consensus by mixing voting algorithms

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A developer discovered a six-week-old defect in a distributed consensus tool where omitting an algorithm flag allowed two of five nodes to falsely declare a 100% confident consensus result. The bug stemmed from the tool silently switching between Multi-Paxos and BFT fault models across rounds on shared state, causing split-brain: the same file simultaneously recorded two conflicting consensus values. Because the two algorithms operate under incompatible fault assumptions, alternating between them on a single topic meant neither guarantee held, enabling a single unknown node to elect itself leader and overwrite an established consensus. The fix binds each topic's state file to the algorithm that first wrote it, and any mismatched round now exits with an error rather than producing a silent, invalid result.

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