ABAP Cloud
What it is
SAP's restricted ABAP programming model and language scope for building upgrade-stable, cloud-ready apps. You may use only released APIs and the ABAP-for-Cloud language version; the compiler enforces it. It runs on the ABAP Environment (BTP), in S/4HANA Cloud, and on-stack in S/4HANA via developer extensibility.
Why it matters for Clean Core
ABAP Cloud is Clean Core made enforceable: the language version + released-API allow-list mean you literally can't write the upgrade-unsafe patterns. It's the target runtime for all new on-stack ABAP.
Common pitfall
Thinking 'ABAP Cloud' means 'ABAP in the public cloud'. It's a development model and language scope — you write ABAP Cloud on-premise too (developer extensibility). The constraint is the language version, not the data centre.