How to Fix GeckoLib Mob Animations Breaking When You Enable Shader Shadows

Confirm the Conflict First

Before changing anything, verify that the problem is actually the shader shadow interaction and not a broken model file. Load your world with shaders off and watch a GeckoLib mob (a modded creature that uses skeletal/keyframe animation) walk, attack, or idle. If it animates smoothly without shaders, then enable your shaderpack and watch the same mob again. The classic symptom of this conflict is limbs snapping to a rest pose, jittering, or freezing mid-animation only when entity shadows are turned on in the shader settings.

Apply the Fix

1. Make sure the compat mod is present alongside both Iris (or Oculus) and GeckoLib. It must load after GeckoLib to patch the animation pipeline.

2. Open your shaderpack's settings in-game and find the entity shadow option. Toggle it off, then back on, and re-watch the mob. The compat layer should now keep the shadow pass from corrupting the animation state.

3. If animations still stutter, lower the shadow resolution or shadow distance in the shader options — the conflict is worst when the shadow pass runs at high cost.

4. Reload resources with F3+T after changing shader settings so GeckoLib re-registers its renderers.

If It Still Fails

Test a different shaderpack. Some packs hook entity rendering in ways the compat mod cannot intercept. If one pack works and another does not, report it to the shaderpack author rather than assuming the compat mod is broken.