Caelus API FAQ

It turns vanilla's hardcoded elytra flight into a generic attribute called CaelusAPI.ELYTRA_FLIGHT that any mod can read or grant. The vanilla elytra itself now uses this attribute, so its behavior is unchanged.

Give the item or armor a modifier that adds points to the CaelusAPI.ELYTRA_FLIGHT attribute. Any value of 1 or higher enables flight, while the default of 0 keeps it disabled.

Check that the attribute value actually reaches 1 or more while the item is equipped, and that you're testing with the item worn rather than just in your inventory. If the value stays at 0, flight stays off.

No, it's a utility/library mod with no content of its own. It only provides the flight attribute and rewires the vanilla elytra to use it.

Yes, install it on both sides. The attribute and the mods that depend on it need to be present on the server and every client for flight to work correctly.

No. The vanilla elytra was changed to read the new attribute, but its behavior is kept the same as normal, so existing elytra flight is unaffected.

You can install it alone, but on its own it won't change anything you can see, since it only exposes the attribute for other mods to use. It's meant to be a dependency.

The mod that adds the backpack or armor has to apply the CaelusAPI.ELYTRA_FLIGHT attribute to it. Caelus API itself doesn't add flight to arbitrary items; it just provides the mechanic the other mod hooks into.

It's a small utility mod, so its own overhead is minimal. Any performance impact you notice is more likely coming from the mods that use the attribute.

Make sure Caelus API is installed on both client and server and that the other mod is actually applying the attribute to the item you're using. If the attribute value never reaches 1, flight won't trigger.

It doesn't add anything you can craft or see on its own; it's a library that lets other mods grant elytra-style flight through an attribute instead of forcing every flying item to be a vanilla elytra. If a modpack includes it, it's almost always because another mod depends on it.

No. On its own it changes nothing noticeable in your world, so only keep it if another mod in your pack lists it as a dependency. Removing it while a dependent mod is installed will usually crash the game on startup.

Check that the game launches without a missing-dependency error and that any mod using it (custom wings, gliders, jetpacks) actually lets you fly. If those items behave like normal armor instead of gliding, the attribute isn't being applied.

It was pulled in automatically as a dependency by another mod, usually a wings, glider, or flight mod. It's normal to see it there even though you never downloaded it directly.

This usually means a mod is overwriting the elytra flight attribute or a conflicting flight mod is fighting for control. Try removing other flight/elytra mods one at a time to find the conflict, and make sure the vanilla elytra still works on its own.

Only if you're a mod developer or datapack author; the flight is controlled by an attribute that defaults to disabled. You need to set that attribute on the player (or item) to enable flight, otherwise the wings are just cosmetic.

Yes, it's published for both loaders, but you must grab the build matching your loader and game version. Mixing a Forge build into a NeoForge instance (or vice versa) will fail to load.

No, it's a tiny utility mod that only exposes an attribute and doesn't run heavy per-tick logic. Any lag you see is coming from the mods that use it, not from Caelus itself.

Only if nothing depends on it. Check your pack for mods that require it (wings, gliders, flight overhauls); if any are present, removing Caelus will break them or crash the game.

No, the vanilla elytra was rewritten to use the same attribute, so its behavior stays identical to normal. You won't notice any difference in how elytra fly, boost, or take durability damage.