A two-stage epigenome-wide study in aneurysmal subarachnoid hemorrhage patients evaluates whether an ANGPT1 methylation signal predicts stroke risk after aneurysm rupture. The signal reportedly flipped direction upon replication, underscoring both the promise and the reproducibility challenges of epigenetic biomarkers for delayed cerebral ischemia. The work highlights why biomarker discovery pipelines in epigenomics must include robust replication and pre-specified directionality expectations. For clinical development groups, it signals that even biologically plausible methylation markers can be unstable across cohorts and analytical pipelines. Taken together, the findings stress that epigenetic risk tools may need deeper mechanistic alignment and tighter control of confounders before clinical utility can be claimed.