Guardian pipeline behaviour versions

A behaviour drift on medication ingestion signals was detected on 28 August 2026, during a manual consistency check. What happened: the previous day (27 August), the pipeline responded to a medication ingestion signal with a deterministic safety directive (SAMU orientation, 15). Overnight from the 27th to the 28th, the response became an exploratory question — without the code SHA changing, and without any monitoring tool available at that time raising an alert. An integrator could have operated for days believing they were protected. What this means: a pipeline's behaviour can change without the code changing. Possible causes: modification of an underlying model, context drift, inference parameter change. Monitoring by code SHA alone is insufficient. What was done: manual consistency check resumed. Work opened on the Core side to produce a behaviour fingerprint (SHA-256 of observed behaviour, not of the code), a startup lock, and a continuous probe. Why publish this episode: denying or minimising it would undermine credibility. Publishing it with full context demonstrates that the detection mechanism works — however imperfectly — and that transparency commitments are honoured.