CoroUtil and AtlasLib are separate library projects. They may both appear in modded Minecraft searches, but a library is not a generic plug-in slot: dependent mods are built against specific code and dependency identifiers.
Different projects, different contracts
A mod compiled against CoroUtil expects CoroUtil’s classes, versions, and behavior. A different library can provide useful utilities of its own without satisfying that dependency.
That means AtlasLib should not be copied in as a replacement for CoroUtil unless the dependent mod explicitly supports it.
How to read a dependency requirement
Look for the exact required library name, Minecraft version, mod loader, and acceptable version range. Treat those labels as technical compatibility information.
If a modpack contains both libraries, that can be normal when different mods depend on each one. Do not remove one simply because the other is present.
Avoiding library confusion in modpacks
Keep filenames descriptive, remove obsolete duplicates, and document which gameplay mods depend on which libraries.
When updating, change one dependency family at a time and test the copied instance. This prevents an unrelated library update from obscuring the real cause of a crash.
Practical next steps
Keep a written record of the versions that work together, change one dependency group at a time, and preserve a backup before updates. For a broader overview, see the CoroUtil guide library or return to the download section for the project’s specified archive.