XCO Library
What it is
The eXtension Components library — a released, fluent ABAP API for things classic code did with unreleased helpers: string/JSON/CSV handling, time/UUID generation, metadata reads, and more. The go-to replacement when a classic utility isn't released.
Why it matters for Clean Core
Half of custom-code migration is finding the released successor to a utility you used to call directly. XCO is where many of those successors live, so knowing it well shortens a lot of migrations.
Common pitfall
Reaching for a familiar function module (e.g. for GUID or JSON) and hitting an 'unreleased' wall. Check XCO first — `xco_cp` and friends usually have the released equivalent you need.