Released APIC1
What it is
An SAP object (CDS view, class, interface, function, table type…) that SAP has formally released for use in cloud development with a stability contract — the C1 release contract. In ADT its API state shows 'Released'. Only released APIs are callable from ABAP Cloud code.
Why it matters for Clean Core
Released APIs are the only dependencies SAP guarantees not to break. Build on them and your extension is upgrade-stable; build on unreleased internals and you've signed up for unannounced breakage.
Common pitfall
Assuming a familiar table or function still exists because it always has. MARA, BAPIs and most function modules are NOT released for ABAP Cloud — you must find the released CDS view or API (e.g. I_Product) successor.