Post release of 0.5.3: the Sample Ratio Mismatch check in Tester.run is now opt-in — it no longer runs by default, so existing pipelines get no new warnings and no extra Spark jobs. Enable it with check_srm=True (equal expected sizes) or by providing srm_expected_ratios={"A": 0.9, "B": 0.1} (supplying ratios opts in automatically; an explicit check_srm=False always wins). The standalone ambrosia.tools.srm.check_srm is unchanged.
No other changes relative to 0.5.3 — see its notes and the CHANGELOG for the full release content.