For those experiencing java.lang.NoClassDefFoundError: net/minecraftforge/fml/client/GuiIngameModOptions on the latest versions of Forge, change the following section of the config:

tweaks {
    # Replace the FML test config GUI with a working GUI.
    B:replaceInGameConfig=true
}

to

tweaks {
    # Replace the FML test config GUI with a working GUI.
    B:replaceInGameConfig=false
}

Yes! I see in other post. Thanks for all! :D

2015-11-26 18:04 GMT+01:00 Jadran Kotnik [email protected]:

For those wondering, change the following section of the config:

tweaks {
# Replace the FML test config GUI with a working GUI.
B:replaceInGameConfig=true
}

to

tweaks {
# Replace the FML test config GUI with a working GUI.
B:replaceInGameConfig=false
}

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