What changed in 7.5

Version 7.5.0 added a planned road system and an inter-city highway network. Both are on by default. A setup that worked on 7.4.12 generates different cities after the upgrade, with no change to your config and no change to your datapack. code review

This page documents 7.5.1 for Minecraft 1.20.1, read from that jar. The same system is in 8.4.1, 9.5.1 and 10.0.1, where it is identical. See The NeoForge line. code review

Your datapack still means the same thing

The claim-test pack written for 7.4.12 runs unchanged on 7.5.1 and gives the same 28 results. Palette merge order, the 128-slot rule, loot and mob resolving through a Condition, range counting storeys, stair shape recalculation, the torch gate, tag, character truncation and the belowpart bug all behave identically.

7.5 changed where cities put things, not what a datapack means. Everything on this page is about placement. Nothing on the reference pages changes. game test

The one measurable side effect on an unchanged pack: doorways move. The mod cuts a doorway toward an adjacent city chunk, and the road planner changes which neighbours those are, so wall counts shift by multiples of 16 even with buildings pinned to identical coordinates. game test

buildingchance no longer fills every eligible chunk

The mod refuses a building in any chunk the road planner has claimed, and it refuses it before it rolls buildingchance. Setting buildingchance to 1.0 therefore no longer puts a building in every city chunk. To restore the 7.4.12 behaviour, set streetGenerationMode to LEGACY.

A broken refpalette now fails the building

On 7.4.12 a building whose refpalette did not resolve still generated, as long as every one of its parts carried a working refpalette of its own. The building's palette was never needed, so the broken name was never dereferenced. game test

From 7.5 that palette is resolved regardless, and the building fails instead. Measured on the same pack across five versions: game test game test

Version	The building	Chunks failing on that palette game test game test game test
6.0.3	absent, and the server does not survive it	generation stops
7.4.12	generates, 512 blocks	2, neither of them the building's
7.5.1	absent	8, including the building's own
8.2.2	generates, 768 blocks	2, the same two 7.4.12 fails
9.5.1	absent	8, including the building's own

Tolerance is a window rather than a direction. 6.0.3 already resolved the palette regardless, 7.4.12 and 8.2.2 do not, and 7.5.1 and later do again. 8.2.2 is 7.4-era code on a 1.21 loader, which is why it sits with 7.4.12 here. See Traps specific to one version. game test

The newer behaviour is the better one, because the mistake becomes visible. It is listed here because a pack that appeared correct on 7.4.12 for this reason loses that building on 7.5, with no key having changed. game test

The three keys that decide everything

These three cover most authoring needs. All three defaults were read from the field assignments in LostCityProfile, not from the list of accepted values. code review

Key	Values	Default	Meaning code review
streetGenerationMode	LEGACY, HIERARCHICAL_GRID_V1	HIERARCHICAL_GRID_V1	LEGACY generates streets as 7.4.12 does, from the city shape alone. HIERARCHICAL_GRID_V1 plans a road grid first, then fits buildings into what is left.
highwayGenerationMode	LEGACY, INTERCITY_NETWORK_V1	INTERCITY_NETWORK_V1	LEGACY generates highways on fixed intervals as 7.4.12 does. INTERCITY_NETWORK_V1 places hubs near likely cities and routes highways between them.
multiBuildingStreetConflict	BLOCK_ALL, OVERRIDE_MINOR, OVERRIDE_ALL	OVERRIDE_MINOR	Decides which planned roads stop a multi-building. See the table below.

Restoring 7.4.12 behaviour

Set both modes to LEGACY in config/lostcities/common.toml: code review

streetGenerationMode = "LEGACY"
highwayGenerationMode = "LEGACY"

multiBuildingStreetConflict then has no effect, because there are no planned roads for a multi-building to conflict with. code review

How multiBuildingStreetConflict resolves

The mod asks the value whether a given planned road type blocks the multi-building. The answer is exact: code review

Value	Blocks on PRIMARY	Blocks on SECONDARY	Blocks on TERTIARY	Blocks on NONE code review
BLOCK_ALL	Yes	Yes	Yes	No
OVERRIDE_MINOR	Yes	No	No	No
OVERRIDE_ALL	No	No	No	No

With the default OVERRIDE_MINOR, a multi-building cuts through secondary and tertiary roads, and a primary road still stops it. code review

An unrecognised value throws IllegalArgumentException. The mod uppercases the string first, so override_minor is accepted. code review

The mode is stored per world, not per config

The two mode keys set what a new world gets. The mod writes the chosen mode into the world's saved data and reads it back on every later load. code review

Situation	Result code review
New world	Takes the mode from the config key.
Existing world	Keeps the mode it was created with. Changing the config key does nothing.
Saved mode is not a recognised name	Falls back to LEGACY and logs Unknown persisted street mode '<name>' for <dimension>; using LEGACY.

The same applies to highwayGenerationMode, with the message Unknown persisted highway mode '<name>' for <dimension>; using LEGACY. code review

Changing the config key does not convert an existing world

The mod reads the persisted mode, not the config key, for any world that already exists. To change the road system of a world you already generated, you must start a new world.

The road hierarchy

HIERARCHICAL_GRID_V1 classifies every city chunk as one of four planned road types. The type decides whether a building may stand there. code review

Type	What it is	Building allowed code review
PRIMARY	The main corridors. Spacing is set by primaryRoadSpacingX and primaryRoadSpacingZ.	No
SECONDARY	Roads inside a primary block. Count is set by secondaryRoadMinCountX, secondaryRoadMaxCountX and the matching Z pair.	No
TERTIARY	Short access roads into a subdivided block.	No
NONE	Not a planned road.	Yes, subject to buildingchance

The order the mod decides in

For each city chunk, checkBuildingPossibility runs these tests in this order and returns at the first one that matches: code review

1. A predefined building is at this chunk. Building.
2. A predefined street is at this chunk. No building.
3. The chunk is part of a multi-building. Building.
4. The planned road type is not NONE. No building.
5. The buildingchance roll fails. No building.
6. Highway and level tests follow. code review

Step 4 sits above step 5. That is the whole reason buildingchance stopped behaving as it did in 7.4.12. code review

Step 3 sits above step 4. A multi-building that survived the multiBuildingStreetConflict test wins against a planned road. code review

New profile keys

Version 7.5.1 adds 29 profile keys and removes none. The 3 above are covered already. The remaining 26 tune the two planners. code review

Defaults and ranges are read from the registration calls. The meanings below are traced to the code that reads each key, not copied from the mod's own comments. code review

Primary roads

A chunk column is a candidate corridor when floorMod(chunkX - offset, primaryRoadSpacingX) is 0. code review

The offset is derived from the world seed and from a hash of the dimension name, and it lands between 0 and the spacing. The grid therefore does not align to chunk 0, and 2 dimensions in the same world get different offsets. code review

A candidate becomes an actual road in one of 2 ways. It is forced when floorMod(candidateIndex, primaryRoadForceEvery) is 0. Otherwise a deterministic hash decides, against primaryRoadOptionalChance. code review

Key	Default	Range	Meaning code review
primaryRoadSpacingX	8	8 to 128	Chunks between candidate corridors along the X axis, which run north to south. A candidate is not necessarily a road.
primaryRoadSpacingZ	8	8 to 128	The same along the Z axis, for corridors running east to west.
primaryRoadForceEvery	4	1 to 16	Every Nth candidate becomes a road with no roll. At 1 every candidate is forced, and primaryRoadOptionalChance then has no effect. This value times the spacing is the largest possible gap between primary roads, so 32 chunks at the defaults.
primaryRoadOptionalChance	0.45	0.0 to 1.0	The chance that a candidate which was not forced becomes a road. At 0.0 only the forced corridors exist. At 1.0 every candidate becomes a road.

Secondary roads

Inside a block bounded by primary roads, the planner picks a count, then picks positions for that many roads. code review

The count is not uniform across the range. It is 75 percent driven by a local density value and 25 percent by a hash. code review

Positions are drawn from minimumRoadEdgeDistance to blockSize - minimumRoadEdgeDistance, shuffled deterministically, then accepted one at a time only when far enough from every road already accepted. code review

Key	Default	Range	Meaning code review
secondaryRoadMinCountX	0	0 to 128	The fewest north/south secondary roads a block may get.
secondaryRoadMaxCountX	2	0 to 128	The most it may get. When the minimum equals the maximum, that exact count is used with no roll.
secondaryRoadMinCountZ	0	0 to 128	The same for east/west roads.
secondaryRoadMaxCountZ	2	0 to 128	The same for east/west roads.
minimumRoadSeparation	4	2 to 32	Chunks required between 2 parallel secondary roads. A position closer than this to an accepted road is rejected.
minimumRoadEdgeDistance	3	2 to 32	Chunks kept clear at each edge of the block. If twice this value leaves no room inside the block, the block gets no secondary roads at all.

The count is a maximum, not a guarantee

Positions are accepted greedily against minimumRoadSeparation, and the planner stops when it runs out of candidates. A block that cannot fit the chosen number of roads gets fewer, silently. Raising secondaryRoadMaxCountX without lowering minimumRoadSeparation therefore changes nothing once the block is full.

Tertiary roads

A subdivided block gets at most 1 tertiary road. The planner rolls the chance, then picks a direction, then picks a length. code review

Key	Default	Range	Meaning code review
tertiaryRoadChance	0.4	0.0 to 1.0	The chance that a block gets its 1 tertiary road. At 0.0 none are generated.
tertiaryRoadMinLength	2	1 to 16	The shortest acceptable road, in chunks. If the space available is below this after the maximum is applied, the block gets no tertiary road even though the chance roll succeeded.
tertiaryRoadMaxLength	5	1 to 32	The longest road, in chunks. Available space is capped to this value before the minimum is tested.

Bridges over water

Key	Default	Range	Meaning code review
plannedPrimaryBridgeChance	1.0	0.0 to 1.0	The chance that an eligible water crossing becomes a bridge. The roll is made once for the whole crossing, not per chunk, so a crossing is either entirely a bridge or entirely not. At 0.0 no planned bridges are generated.
plannedPrimaryBridgeMaxLength	12	1 to 64	The furthest, in chunks, that the planner searches for the far bank. A water gap wider than this produces no bridge.

Open lots

Key	Default	Range	Meaning code review
openLotParkChance	0.8	0.0 to 1.0	The chance that an open lot receives a park part. A city style may override this through profile_overrides, which is the only key that object accepts.

Highway hubs

The world is divided into square planning cells. Each cell holds at most 1 hub. The planner tests candidate positions inside the cell, scores each one by city potential, keeps the best, and then discards it if the score is too low. code review

The score is the city potential clamped to 0 to 1 and scaled to an integer, and the threshold is highwayHubMinimumPotential scaled the same way, so the key reads as a direct 0 to 1 cutoff. code review

Key	Default	Range	Meaning code review
highwayPlanningCellSize	128	32 to 512	The side of one planning cell, in chunks. A larger cell means fewer hubs, and so fewer highways.
highwayHubSampleSpacing	16	1 to 512	Chunks between the candidate hub positions tested inside a cell. A smaller value tests more positions and finds better sites. It may not exceed the cell size.
highwayHubMinimumPotential	0.2	0.0 to 1.0	The city-potential score a cell's best candidate must reach. Below it the cell produces no hub. Raising this gives fewer hubs.
highwayHubSearchRadiusCells	2	0 to 8	How many cells outward a hub looks when searching for neighbours to connect to. At 0 a hub sees no neighbours, so no routes are formed.

Highway routes

Key	Default	Range	Meaning code review
highwayMinimumHubDistance	64	0 to 4096	Hubs closer together than this, in chunks, are not connected to each other.
highwayMaximumHubDistance	320	0 to 4096	Hubs further apart than this are not connected.
highwayMaximumConnectionsPerHub	2	1 to 8	The most connections accepted at a single hub. A denser network needs a higher value here as well as a wider search radius.
highwayMinimumRouteLength	40	0 to 4096	A candidate route shorter than this many chunks is discarded.
highwayRouteCityPenalty	1.0	0.0 to 1000.0	The weight given to city potential when the planner chooses where an L-shaped route bends.
highwayNetworkLevel	0	0 to 32	The fixed level used for every highway when highwayLevelFromCities is 4. It is ignored for every other value of that key.

Existing keys that changed

Three keys that already existed behave differently in 7.5.1. No key was removed. code review

highwayLevelFromCities changed its default

	7.4.12	7.5.1 code review
Range	0 to 3	0 to 4
Default	0	3

Two separate changes, and the default is the one that affects you. On 7.4.12 a highway took its height from one endpoint city. On 7.5.1 it takes the average height of both, unless you set the key back to 0. code review

The new value 4 makes the mod use the fixed highwayNetworkLevel instead of deriving the level from the endpoint cities. code review

The description of value 0 also changed, from "take height from top-left city" to "take height from the first endpoint city". code review

The spawn search changed

Neither key changed its default or its range. What the numbers mean changed. code review

Key	7.4.12	7.5.1 code review
spawnCheckAttempts	A count of attempts.	A count of chunks to check.
spawnCheckRadius	The start radius. The mod widened it by a fixed 100 on failure.	The start radius. The mod spirals outward from the world centre and widens by spawnRadiusIncrease.

If you raised spawnCheckAttempts on 7.4.12 to work around a spawn failure, the same number now means a different amount of searching.

These ranges are enforced

Unlike the building keys, these are validated. The mod rejects combinations that cannot work, with messages such as: code review

• Secondary road minimum counts cannot exceed maximum counts
• highwayMinimumHubDistance cannot exceed highwayMaximumHubDistance
• highwayHubSampleSpacing cannot exceed highwayPlanningCellSize
• tertiaryRoadMinLength cannot exceed tertiaryRoadMaxLength
• Primary road candidate spacing must be between 8 and 128 chunks
• Road separation and edge distance must be between 2 and 32 chunks
• Secondary road counts must be between 0 and 128 code review

New datapack keys

Version 7.5.1 adds 15 datapack keys, removes none, and changes no key from optional to required or back. Every 7.4.12 datapack still loads. code review

Asset	Key	Notes code review
City style	profile_overrides	An object holding per-city-style profile values.
City style, inside profile_overrides	openLotParkChance	The only key the object accepts in 7.5.1.
Selectors	largebridges	Selector list, alongside the existing bridge selectors.
Street settings	largeparts	Part names for the wider planned roads.
Street settings	tertiaryparts	Part names for tertiary access roads.
Street parts	connector	The shape where a wide road meets a narrower one.
Street parts	stair	The shape where a road changes city level.
Highway parts	open_bend, open_t	Bend and T shapes for an open highway.
Highway parts	bridge_bend, bridge_t	The same two for a bridge section.
Highway parts	tunnel_bend, tunnel_t	The same two for a tunnel section.
Scattered building	supportpart	Part name used underneath a scattered building.
Scattered building	clearhighwayrailing	Whether the scattered building clears highway railings.

This table said 7 keys until the extraction was rebuilt

The eight highway and street shapes were missing from it. All eight belong to HighwayParts and StreetParts, two of the three codec types that register their fields through a helper rather than through fieldOf, so an extraction reading only fieldOf walked straight past them. testrig/extract-keys.py reads all three, and the counts on this page and on Key Availability come from it. code review

Why the six highway shapes matter. Before 7.5 a highway could only run straight or cross another at the same level, so open, bridge, tunnel and their _bi partners covered every case. The planned road network turns corners and branches, which needs a bend and a T for each of the three section kinds. A pack that overrides highway parts on 7.4.12 and moves to 7.5 will keep its straight sections and get the mod's own parts at every corner until it names the new six. code review

What profile_overrides actually adds

profile_overrides holds exactly one key, openLotParkChance. That is its whole contents in 7.5.1. code review

It is not a general override mechanism, and a city style could already override profile values before 7.5.1. What 7.5.1 adds is a single resolution point, EffectiveCitySettings, which reads 14 values from the city style and falls back to the profile for each one it does not find: code review

buildingchance, minFloorCount, maxFloorCount, minCellarCount, maxCellarCount, parkchance, openLotParkChance, fountainchance, frontchance, corridorchance, avoidfoliage, parkborder, parkelevation, parkstreetthreshold. code review

Thirteen of those already resolved this way in 7.4.12, through the city style's existing buildingsettings, parksettings, streetsettings and corridorsettings. Only openLotParkChance is new, and it needed a new home because no existing settings object covered open lots. code review

What is new inside the mod

For orientation only. 7.5.1 adds 67 classes over 7.4.12 and removes one. code review

Package	Classes	Purpose code review
worldgen.highway	24	Hub placement, route planning, persistence of the hub graph.
worldgen.street	12	The planned road grid, bridge planning, road types.
worldgen.gen	12 to 22	Grew, including scattered-building placement.

The only removal is LostCityTerrainFeature$AvoidChunk. code review