How to Tell If Caelus API Is Actually Working in Your Modpack

Caelus API is a library, not a content mod. It adds no items, no blocks, and no visible UI. That means you cannot "see" it in your inventory or in the creative menu. What you can do is confirm it is loaded and functioning behind the scenes.

Check That the Mod Loaded

Open your mod list (the mods screen on the title menu, or the in-game mod menu if your loader provides one). Search for Caelus. If it appears and is not marked as disabled or errored, the library is present. If it is missing, any mod that depends on it will usually fail to load or crash on startup, which is your first clue something is wrong.

Confirm the Attribute Exists

Caelus exposes an elytra flight attribute. Mods that grant flight read this attribute to decide whether you are allowed to glide. If you have a mod installed that adds a custom wings item, wing-based armor, or a jetpack-style glider, equip it and try to glide. If gliding works, Caelus is doing its job. If the item does nothing, the problem is almost always the other mod, not Caelus itself.

What You Should Not Expect

Do not look for a config file full of toggles, and do not expect a keybind. Caelus deliberately stays invisible so that other mods can share one consistent flight system.