We report on an industrial use case of static callgraph reachability analysis to improve WhatsApp Android app health. We collaborated with engineers dedicated to app health to annotate/specify source code. We leveraged the Infer static analyzer to prevent regressions during code changes and to periodically find pre-existing issues on the latest revision. Within three months, the analysis prevented almost a hundred regressions to be introduced and resulted in fixes for a handful of pre-existing issues, including examples with end-user measurable impact.