arXiv:2610.20970v1 Announce Type: new Abstract: A wind-derived heading can guide a robot towards an odour source even after the wind reverses, but its reliability depends on the plume's transport history. On a quadruped initially facing the source, holding the initial heading reached it in every reversing-wind trial, whereas comparison controllers never settled there. An exact geometric condition links heading correctness to net odour transport, and simulations separate sensing error from departures from nominal flow. Where the alternating wind directions are too close for reversal alone to produce wrong-side headings, the wrong-side rate rises from 1.0% under uniform transport to 4.7% in a stochastic flow. Re-acquiring headings from new odour contact improves simulated search when contact is intermittent. These results identify distinct requirements for wind-guided search: a heading supported by the transport geometry and sufficient intermittent contact to replace it.