We Got Runners!
This mod brings a zombie apocalypse atmosphere to the game by drastically changing zombies' AI to make them behave like in famous post-apocalyptic games. At the same time, no new entities are added to the game - all changes apply to existing mobs.

Main Changes
The mod completely reworks the behavior of all zombie types: regular zombies, swamp drowneds, zombie villagers, and husks. Each type receives unique behavioral features.
Zombie Types by AI
Runners - exceptionally fast zombies that constantly run without stopping. Appear exclusively in groups. Interestingly, baby zombies cannot get speed boosts. In the latest versions, these zombies even wander around when there's no target.
Grounders - perform powerful charges at targets, stunning and weakening victims. Especially dangerous to iron golems, dealing increased damage to them. By blocking attacks with a shield, you can knock them back a long distance.
Walkers (regular zombies) - suddenly perform sprinting dashes toward targets, making their behavior unpredictable.
Special Zombie States
Burning Zombies - when ignited, become even faster and more chaotic in movements.
Swampy Zombies - when wet, get a chance to inflict slowness on victims.
Marauders - zombies equipped with swords or axes can pursue targets longer and more aggressively.
Rider Zombies (with Zombie Horse Spawn mod installed) - gain speed and defense boosts when riding mounts. Can strengthen other zombies within radius by applying speed or damage resistance effects.
Golem Enhancements
In response to zombie enhancements, golems also receive improvements:
Iron Golems now deal area damage, push groups of enemies away, have resistance to weakness effects, and increased armor against physical damage.
Snow Golems also deal area damage, slow enemies, and can throw snow bombs that freeze opponents over a large territory. When attacked by allies, they can restore health. Snowballs now only damage selected enemies.
How It Works
During spawning, zombies randomly receive different AI types. Runners appear only in groups and can convert regular zombies within a 5-block radius into similar types - the larger the group, the higher the chance. Walkers and Grounders appear in the usual way.
Special zombies appear almost as often as regular ones, with zombie villagers having increased chances of becoming special types. Some zombies demonstrate strange movement patterns.
Compatibility
The mod works perfectly with any mods that change mob AI. Since no new entities are added, any mods editing zombies are fully compatible. New rider zombie types only appear with the Zombie Horse Spawn mod installed.