A Three-Part Field Manual on What Actually Determines Production Outcome QualityThis is the introduction to a three-part series. It frames the conviction, names the production failure modes that motivated the series, and previews the three parts that defend the argument with engineering specifics.The BackdropAfter eighteen months of hands-on designing agentic systems in production — multi-agent platforms in regulated industries where context-window collapse means a compliance violation, not a UX bug — I have stopped paying attention to which model the team picked. In production, model choice does not predict success. Three other things do, and the field is underinvesting in all three.