Why does my AI character behave differently when instantiated at runtime versus placed in the editor?

[Alex_Thunder]

I’m running into a weird issue with my AI character setup. When I drag the AI prefab directly into the scene through the Unity editor, everything works perfectly fine. The character moves around properly and all animations play correctly.

But when I try to instantiate the exact same prefab during gameplay using code, something goes wrong with the AI behavior. The character gets stuck playing the idle animation and won’t transition to walking.

I tracked down the issue to the ground detection system in my character controller script. There’s a function called VerifyGroundContact() that’s failing, specifically this line:

animatorComponent.applyRootMotion = false;

When this happens, my character just slides across the ground instead of playing the proper walk animation. It seems like the ground detection isn’t working when the prefab is spawned at runtime.

I can’t figure out what’s different between placing the prefab in the editor versus spawning it with code. Has anyone else run into this kind of problem before?

[John_Clever]

It seems you might be experiencing a timing issue with component initialization. When the AI character is instantiated at runtime, the physics system might not have fully processed the character’s collision state before your ground detection runs. I’ve encountered similar scenarios where ground checks fail immediately after instantiation because the character hasn’t settled into the physics environment. Consider adding a slight delay or utilize WaitForFixedUpdate() before executing your ground detection function. Additionally, you could force a physics update with Physics.SyncTransforms() right after instantiation. Also, ensure that the instantiated prefab is spawning at the same Y position as it does in the editor, as even minor height differences can disrupt ground detection raycasts.