This record contains the code, derived data tables, site registry, coordinate-cell alignment repair registry, sample input data, figure outputs and provenance files supporting the Nature Water Analysis manuscript “Decision-window stress characterises flood-warning timing constraints in a 120-site river-basin sample”. The analysis uses daily GloFAS/Open-Meteo discharge to evaluate whether retrospective Q90-to-Q95 high-flow transition events preserve enough usable time under specified action-lag and institutional-delay scenarios. The central scenario uses 120 hydrologically screened river sites, 5,992 events from 1997-01-01 to 2022-07-31, L=1 day and D=3 days. The archive includes smoke-tested scripts for event detection, site-cluster bootstrap/sensitivity analysis and targeted observed-gauge plausibility checks. The analysis is a retrospective discharge-transition diagnostic, not a forecast-skill assessment or observed measure of institutional delay.