Transitioning enterprise SAP landscapes to modern S/4HANA Cloud and adopting SAP Business AI requires a fundamental shift in architectural mindset. The era of treating extensibility as merely "writing custom code in Eclipse ADT" is over.

In production environments, the challenge is rarely just syntax—it is architectural governance under Clean Core:

When does a requirement belong on Client 100 (Key-User Extensibility) versus Client 080 (Developer Extensibility)?

How do you orchestrate LLMs via SAP Generative AI Hub while guaranteeing Zero Data Retention?

How do you semantically ground enterprise prompts using SAP HANA Cloud Vector Engine without leaking cross-tenant or unauthorized business data?

As a practicing SAP Solution Architect (10× SAP Certified, actively delivering modern S/4HANA Cloud and BTP architectures), I put together this field guide to bridge the gap between official, high-level documentation and the concrete architectural patterns required to deliver upgrade-stable cloud…