ADT (ABAP Development Tools)ADT
What it is
The Eclipse-based ABAP IDE — 'ABAP in Eclipse'. CDS, RAP, behavior definitions, and the API-state/released-object views only exist in ADT, not in classic SE80.
Why it matters for Clean Core
ADT is mandatory for modern ABAP: you cannot author CDS view entities or RAP objects in SE80, and the 'Released APIs' and 'cloud readiness' affordances live in ADT. The move to Clean Core starts with the move to ADT.
Common pitfall
Trying to stay in SAP GUI / SE80 for new work. Beyond the missing editors, ADT is where you check an object's API release state and navigate the released-API tree — central daily tasks you simply can't do in GUI.