Two issues:

If l edit on this in-game config. For some reason l did not work, mobs are not auto targeting, and l restart minecraft while edited in-game target config has present, it did not saved on target config

l edit on config txt file and save, minecraft on startup crashed

ai {
    # List for of pairs containing which mobs auto target others. Syntax is [mob id e.g. minecraft:skeleton]-[mob id or class name e.g. EntityZombie] where the class name is the target [default: ]
    S:"Auto Target List" <
        minecraft:wolf
     >

crashed file - https://pastebin.com/vr6c8Crj

Affected Versions:

Minecraft: 1.12.2
Forge: 14.23.5.2847
TenshiLib: 1.2.1
Improved Mobs: 1.5.2

no other mods did this

its a pair. you only specified one entity. you need to also add the other.
its [mob]-[mob]

darn, you right. sorry about the issue, my bad. thanks!