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Breeds

A breed is a constrained slice of the gene pool plus the metadata the spawn and breeding systems need. Wild herds are rolled from a breed so that a paddock of horses reads as a population rather than 47 unrelated animals; a lone wild horse, a /summon or a spawn-egg horse is the Feral Mixed breed and rolls every gene unconstrained — the pre-breeds behaviour. This page is the readable version of the breed files; the numbers in them are a first pass.

A breed is a JSON file. Every breed here lives in common/src/main/resources/horsegenetics/breeds/, one file each, and a breed you write yourself goes in .minecraft/phc/breeds/ and needs nothing but the jar - the folder is made on first launch, and the Breeds tab of the H menu opens it. The breed designer writes them and the breed file format documents them. Java breeds are still possible for one that needs behaviour rather than numbers, and Feral Mixed is the only one shipping that way.

Herd or loner

BreedSpawnHandler (a one-line FinalizeSpawnEvent hook) does nothing but tag a NATURAL / CHUNK_GENERATION / SPAWNER horse with a wild_spawn NBT flag. It does not touch the pack SpawnGroupData: Horse.finalizeSpawn replaces any custom pack data with its own Horse.HorseGroupData between every pack member, so that route can carry nothing (the earlier BandData attempt silently made every horse its own herd of one — "herds are all mixed breeds", "groups of four solo Feral Mixed").

HerdManager.assignFounder forms the herd by proximity, one tick later (deferred from onHorseJoin's server.execute, so nothing heavy runs inside the chunk system). A freshly-spawned wild horse looks at the untamed wild horses within HERD_RADIUS (32) blocks:

• if one is already in a wild herd → join it: its breed, its band, its lead, and a sex that fits the band (traditional joiner = mare, bachelor joiner = stallion);
• else if one is also a fresh natural spawn (a pack-mate still waiting its turn) → found a herd: this horse is the lead stallion, the breed is pickHerdBreed (weighted by commonness, Feral Mixed only if the biome has no breeds), the band is a 70/30 coin;
• else it is genuinely alone → a lone Feral Mixed, no herd.

So every clump of wild horses is one herd of one breed, and only a solitary horse is Feral Mixed — and because a lone horse near an existing herd joins it, you never see a knot of unrelated solo horses. A spawn-egg horse (record pre-set) or a /summon has no flag and stays Feral Mixed; breeding overrides that with the parents’ cross.

Which biomes spawn horses at all is data/horsegenetics/neoforge/biome_modifier/add_horse_herds.json, a horsegenetics:breed_herds modifier (BreedHerdsBiomeModifier): herd-sized (weight 10, 3–6) horse spawns in the biomes it lists and in every biome any wild breed names - once each, never twice. The second half is what makes a drop-in breed spawn: a breed living in a dark forest or a modded biome gets herds there on the next start, with nothing edited but its own file. add_horse_loners.json adds a thin weight-1 1–1 trickle to every overworld surface biome (a strong bias to packs). So horses appear in taiga, jungle, badlands, swamp, the snowy biomes and mushroom fields, none of which spawn them in vanilla. A horse still needs grass and light to spawn, so a breed that names a desert or the Nether will rarely or never be seen wild.

Day and night. A breed's spawn_time (any, day or night) is checked when a herd is founded: outside its hours the breed is not a candidate, and the biome's other breeds share the draw (HerdManager.pickHerdBreed). Vanilla will not spawn an animal in the dark on a chunk near a player, so a night breed's herds mostly come from chunks generated after dark.

Traditional bands and bachelor bands

A wild pack is one of two shapes (BandType), chosen ~70/30 by the first member spawned:

• Traditional — one stallion (the herd lead), his harem of mares, and the occasional foal. Foal rate is vanilla's ~5% per pack member for now — the pack AgeableMobGroupData can no longer be overridden, so the intended "up to 3 foals" is a follow-up.
• Bachelor — a band of 3–5 stallions, no mares, no foals. The first one spawned is the lead.

Every member of the herd shares the lead's breed and band. WildHerdGoal (a follow goal on every untamed horse) keeps non-leads within a few blocks of the lead, re-pathing every ~15 ticks, so a spawned pack stays clumped and wanders together. If the lead dies or unloads for 10 s, the first member to notice promotes itself. HorseCareHandler's together-timer herd formation now skips any horse already in one of these natural herds.

Wild horses aggro like wolves

HorseAggroHandler. Hitting an untamed horse turns it and every herd-mate within 24 blocks on the attacker — a horse will path to and kick anything it is angry at, for 4 damage (vanilla horses have no ATTACK_DAMAGE; this handler adds it via EntityAttributeModificationEvent). Break line of sight for 3 seconds and the horse clears its target and goes back to neutral (WildHorseForgetTargetGoal). Tamed horses are never affected, and debug-dimension horses take no damage so they never aggro.

What a breed pins

Epigenetic bands: “deeply black”, not merely “black”

A pool says which allele; a band says how much. Each gene declares named numbers on every allele copy, and a breed may pin any of them to a closed range — the general form of what the stat bands already did for the four body axes. Each founder gets a point inside the band on both copies, drawn separately so its two gametes are not interchangeable.

Three things a band will not do, each warned about at load rather than silently ignored: it cannot touch the four body-stat genes (those belong to the breed’s stat scores), it cannot band a seed or a category (neither has a “slightly more”), and a value the gene does not declare is dropped the way an unknown gene is. See the format page.

Stats: the score → multiplier curve

The sheet scores speed, jump and heartiness 1–10. Score 5 is the value the vanilla-calibrated baseline already produces — multiplier ×1.0. Score 10 is the sheet’s stated ceiling, and the curve is linear to it:

Size is not scored; a breed writes it as a multiple of an ordinary horse, "size": [lo, hi], and the range is the band. A Quarter Horse runs about ×0.92–1.05, a Percheron ×0.98–1.38 (taller than the player at the top end), a Shire or Clydesdale ×1.14–1.43, a Falabella ×0.38–0.51. The files were written in hands until 2026-09-10 and were converted through the old curve - hands over 15.75, with the part above 1.0 tripled (BreedStatCurve.sizeForHands) - so no breed changed size. Hands are still how a horse's size reads: the info screen and the Breeds tab turn a scale back into them (handsFor).

Size decides the genes, founder by founder. A founder's size is drawn inside the range first. Between 0.7x and 1.3x it carries one copy of the size allele and the wild type, with the whole distance on that copy; outside it, two, sharing it. So a miniature or a draught horse breeds true for size, and a breed of ordinary-sized horses throws some variety among its foals - which is how most size variation is carried. A range across 1.3 (a Clydesdale's) produces both.

Each axis becomes a target band (BreedStatCurve). Every founder of the breed is given the pushing allele (both copies, bar the size rule above), and BreedFounder then picks a point inside the band and writes it onto that founder’s two allele copies as ordinary epigenetic numbers. So a Thoroughbred reliably resolves near ×2 speed even though two Swift copies on the ordinary Gaussian would only reach ×1.2. A band that would straddle 1.0 (a near-baseline breed) is dropped and the locus is left wild, so the horse sits exactly on the baseline.

The two copies split the target unevenly, on purpose. Two identical copies would make a founder’s gametes interchangeable, and half the interest in breeding from a good stallion is that his foals differ depending on which copy they drew.

A breed shapes its founders and then lets go

A breed label is therefore cosmetic. It decides what a wild horse of that breed is born as and what a herd spawns, and after that it is lineage bookkeeping for the family tree and the naming. A “Percheron” bred tiny for fifty generations is tiny, and still labelled Percheron. Keeping a line to a standard is the player’s job, not the game’s.

Where magic comes from

A breed's founders carry exactly the magic the breed names. A zombie breed is a set of genes that make it look rotted, a temper and a slow speed score, and every founder is that; it never throws a galaxy coat or a healer because a dice roll said so. Magic in a breed is a design decision, made in the breed designer or the file.

Random magic still exists, in one place: Feral Mixed, the unbred population a vanilla horse spawn and a breedless custom egg belong to. It rolls every gene from that gene's own founder table, magical ones included, so a feral horse is where a stray magical trait turns up — and breeding it into a line is how a player gets magic a breed was not designed with. (Generated stables still add their own extra magic on top of the breeds they place — see stables.)

Where a breed may come from

A breed names any subset of four sources, and naming none means all four. They are a checklist rather than a mode because they are genuinely independent — “a breed the cowboy has heard of but that no longer runs wild” is a real thing to want to say, and so is “a collector’s breed that only exists as an egg”.

Feral Mixed names no source at all, which is the honest answer: it is the absence of a breed, so it never spawns as itself and never has an egg.

A world's own ecology: breed-spawning.toml

A player's breeds are their own files; the breeds the mod ships are inside the jar. .minecraft/phc/breed-spawning.toml is how a world changes the shipped ones without unpacking it — and how it switches them off entirely, so that the only horses in it are the ones its owner designed. It is written on first launch, generated from the registry: one section per shipped breed, each defaulting to what that breed’s own file says, so what you edit is a number you can see.

A wild horse with nothing to be does not spawn. A natural spawn, chunk-generation spawn or spawner spawn is refused outright (BreedSpawnHandler, Breeds.anythingMaySpawn) when no breed of its biome may head a herd at that hour and Feral Mixed is not allowed there. What gets past that — a horse that turns out to be alone where Feral Mixed is off — is discarded by HerdManager a second later, before any record or coat is made for it. /summon and a vanilla spawn egg are a player asking for a horse, and always make a Feral Mixed.

Everything that spawns a horse asks the same registry, so nothing else knows the file exists: Breeds.applySpawnSettings keeps each breed as its file says and publishes a copy with the world's settings applied. Edits are re-read while the game runs and reach herds, the cowboy, stables and eggs at once; which biomes get extra herd spawns is decided by the biome modifier at world start, so moving a breed to a new biome wants a restart.

Breeding: crosses and mixes

A foal’s breed label (BreedLineage.combine, applied in HorseBreedingHandler.applyBredFoal):

Spliced lines

A gene splice carrot whose allele actually reaches the foal marks it Spliced (its breed), and the mark never washes out. It is not a new rule: splice is a reserved lineage component, so a spliced Friesian is the pair {friesian, splice} and every row of the table above applies to it unchanged.

“Actually reaches the foal” is decided by SpliceOutcome.spliceReached, and it asks a question about the foal rather than about the carrot: at a locus a carrot substituted, does the foal carry an allele neither parent had? A mare fed a splice for a gene the stallion already carries has added nothing, and correctly does not mark the foal. Feeding a splice is a gamble and the carrot is spent either way.

This is what makes an ordinary purebred worth more than a spectacular spliced one. Anybody can splice a Friesian into something remarkable; only a breeder can get there without, and the label is the difference.

The label is stored on the HorseRecord (breed, an optional string token) and surfaced in three places: the mounted-horse info panel (under the sex / generation line), the right-click-with-paper dump (breed: line), and the dev-build [coat] chat line (a [Breed Name] tag). The stallion seed jar carries the donor’s breed token in its StoredGenome so a seed-jar foal crosses correctly.

The custom spawn egg “Breed:” preset

CustomHorseSpawnScreen has a Breed: cycle button. Landing on a real breed calls BreedFounder.roll and loads a fresh wild individual of it — genotype, epigenome and sex — straight into the editor; you can then hand-edit any locus. The selected breed token rides along in SpawnCustomHorsePayload and is stamped on the spawned horse (record.withBreed) — but the label alone changes no number, so a horse whose genome you then hand-edited is whatever you edited it into. The first entry, Feral Mixed, is no preset: it leaves the current genome alone and spawns an unbred horse. Drop-in breeds from .minecraft/phc/breeds/ are in the list with the rest.

Not modelled (yet)

The sheet asks for genes and features this mod does not have. None were built in this pass; each is recorded in the breed’s notes() and collected in the roadmap:

• Leopard complex (Lp + PATN1) — built 2026-09-06 as three loci. Appaloosa / Knabstrupper roll it heavily, Kiger / Mustang / Shetland lightly. Striped hooves and white sclera are drawn; mottled skin is not (no skin layer).
• HYPP — Quarter Horse / Paint. Built as SCN4A: one copy is a survivable heart-and-speed cost, two are lethal at birth, and it is dominant — so a wild-caught Quarter Horse really can be an affected one. PSSM1 and HERDA shipped with it.
• Pangare / mealy — built as its own three-allele locus. Exmoor and Fjord carry it near-fixed.
• Early-lethal foal disorders named on the sheet — SCID, CA, LFS, GBED, CVM, megaesophagus all built on the recessive-disorder pattern (PRKDC, TOE1, MYO5A, GBE1, CVM, megaesophagus). NNF is the one still without a locus.
• Mane shape — the baroque flowing manes (Andalusian, Friesian, Gypsy), Przewalski’s upright mane with no forelock. Roadmap render item. The Fjord’s two-tone mane is colour, not shape, and dun draws it.
• Lower-leg feathering — Clydesdale, Shire, Friesian, Gypsy Vanner, Dales, Dartmoor. Roadmap render layer.
• Flaxen — built as a three-allele dosage locus. Haflinger and Belgian Draft carry it heavily.
• Gait (DMRT3) — the gaited breeds (Paso Fino, Tennessee Walking, Standardbred, Icelandic tölt, Hackney action). Needs animation work.
• Won’t model — the Akhal-Teke / Karabakh metallic sheen (a shader), the Marwari’s inward-curving ear tips (a mesh change), and dished / convex / Roman head profiles (Arabian, Lusitano, Percheron, Lipizzan, Shire).

The 49 breeds

Every one of them also has an entry in the breed book — what the breed is, what it was made for, and how it came to be running loose here. This table is the machinery; that page is the reason the machinery has these particular numbers in it.

Height is the stable-notation range from the sheet (baseline 15.75 hh = ×1.0 scale). S / J / H are the 1–10 speed / jump / heartiness scores. Rarity sets the herd-roll weight (Extremely common 48 → Very rare 0.75, doubling per step).

Feral Mixed is absorbing

A horse with no herd identity — a lone wild spawn, a /summon, a spawn-egg horse — is Feral Mixed, and every cross involving one produces a plain Mixed foal. Feral × Feral included, so there is no back door to a “pure feral” line.

It used to be called Unknown and combined like an ordinary distinct breed, so a Friesian bred to a wild loner produced a “Friesian × Unknown cross”. That forced the model to answer a question it has no good answer to: is Unknown a breed? Does it have a stat band, a gene pool, a purity? Can a line be bred back to pure Unknown? Making it absorbing deletes the question instead of answering it, and says the true thing — a horse of unrecorded ancestry contributes unrecorded ancestry, and what comes out is a horse of mixed breeding.

The serialised token is feral_mixed. Like every other format change in this mod there is no back-compatibility: a horse saved as unknown reads as Feral Mixed anyway, since an unrecognised token has always fallen through to it.

Code map

• common/breed/Breed — the record: id, name, natural/magical, biomes, spawn weight, source checklist, per-gene pools (as allele tokens), stat scores, epigenetic bands, price, notes. A fluent Builder, used by the parser and by the Java escape hatch.
• common/breed/Breeds — the registry: the shipped files, the drop-in folder, FERAL_MIXED; forBiome, from, get, displayName, registerJava. The count is Breeds.all().size().
• common/breed/BreedSource — the four-way source checklist.
• common/breed/BreedBands — the epigenetic bands a breed pins.
• common/breed/spec/ — BreedSpecParser, BreedSpecWriter, BreedSpecLoader, BreedFileTool: the file format, both ways round.
• neoforge/ModBreedSpecs — loads .minecraft/phc/breeds/, after the drop-in genes; folder() is what the Breeds tab's button opens.
• neoforge/world/BreedHerdsBiomeModifier — herd spawns in every biome a wild breed names.
• common/breed/Commonness — the rarity → weight ladder.
• common/breed/BreedStatCurve — score / hands → TargetBand.
• common/breed/BreedFounder — rolls a founder Genome for a breed (start from Genotype.random, override the constrained / coat / body-stat / magical genes).
• common/breed/BreedLineage — the label value object: pure / cross / spliced / mixed / feral, combine, displayName, token round-trip.
• common/genetics/SpliceOutcome — did the splice carrot’s allele actually reach the foal.
• common/trait/{StatAxis,TargetBand,BreedStatTargets} — the band types; HorseTraits.resolve takes a BreedStatTargets, and the four magical body-stat genes read it through TraitBuilder.breedBand.
• neoforge/server/BreedSpawnHandler — a one-line FinalizeSpawnEvent hook that flags natural spawns.
• neoforge/server/HerdManager — the deferred genome / record / proximity herd formation.
• neoforge/server/DebugHighlightHandler — the F8 glow toggle.
• neoforge/server/WildHerdGoal — a herd member trails its lead.
• neoforge/server/HorseAggroHandler — wolf-style herd aggro + the horse ATTACK_DAMAGE attribute.
• common/breed/BandType — TRADITIONAL / BACHELOR.
• neoforge/…/data/horsegenetics/neoforge/biome_modifier/ — which biomes spawn horses.