Testing & Debugging Commands¶

TL;DR

/lostcities <command> (alias /lost). Six commands here are useful for checking your custom city actually works.

Command	Needs op? code review
`debug`, `map`, `stats`, `saveprofile`	No, permission level 0
`locate`, `createbuilding`	Yes, permission level 1

The in-game editor has its own page

The mod also ships six commands for live in-world editing: createpart, editpart, resumeedit, exportpart, listparts and locatepart. All six need permission level 1. They also need a world created with editMode: true, and they have some sharp edges, so Editing and Tooling covers them instead.

There is one more, testfill, which drops a 5×5×5 blob of random block states around you. It is a developer scratch command with no authoring use. code review

Seeing your changes¶

There is no regenerate command. Lost Cities ships nothing that rebuilds an existing chunk, and it registers no datapack reload listener, so: code review

What you do	Does it pick up edited assets? code review
`/reload`	No. These registries are read once at world load, and 7.4.12 registers no reload listener. Vanilla does not reload them either.
Leave the world, rejoin (single player)	Yes. Logging out clears the mod's asset cache, so the next world load re-reads every file.
Restart the dedicated server	Yes.
Fly back to an already-generated chunk	No, ever. That chunk is saved to disk. Nothing regenerates it.

So the loop is: edit files, quit to title, rejoin, travel somewhere new (or delete the region files, or start a fresh world). Testing in a throwaway world is usually faster than trying to invalidate an existing one.

Use createbuilding to skip the loop for a single building

/lostcities createbuilding places a building on the spot without waiting for city generation to roll it. It still reads the assets loaded at world load, so rejoin first. It removes the need to search for a chunk that happens to pick the building.

Getting a real profile template¶

/lostcities saveprofile <name>

Writes one of the mod's built-in presets (not your world's active profile) to <name>.json in the server's working directory, fully populated with every key at its default value. No op requirement. This is the fastest way to get a complete, valid starting point instead of typing a Profile from scratch, copy the keys you actually want to change into your own file. code review

Finding out why a chunk looks the way it does¶

/lostcities debug

Run standing in the chunk you want to inspect. Dumps everything the generator decided for that chunk, profile name, building type, floor/cellar count, city level, city style, street type, ruin height, highway levels, rail info, city-sphere data, explosion count, whether it is ocean, straight to the server console, not chat. On a dedicated server you need console/log access to see it; in singleplayer it still only goes to the game log, not the in-game chat overlay. This is the single richest diagnostic available, worth checking first for "why did not my city style/building apply here." code review

/lostcities map

Also console-only. Prints a 41×41-chunk ASCII map centered on you: B = city chunk with a building, + = city chunk without one (street/plaza), . = highway, blank = neither. Good for a quick sanity check that cities and highways are actually generating at the density you expect, without flying around. code review

Reading the answer in chat, and asking about one file¶

/lostcities debug is the richest diagnostic the mod ships, and it writes to the server console only. The Lost Cities - DevTool, a companion mod, answers the same questions in chat and adds the two the mod does not expose: which part was chosen on each level, and what a character resolves to after the palette merge. The DevTool Commands documents all of them. code review

/lcdev report

Profile, world style, city style, building, floor and cellar counts, and the part used on each level, including the parts2 overlay where one applies. That per-level listing is the direct answer to "why did this condition not fire", which otherwise takes a rebuild to find out. code review

/lcdev char G
/lcdev char U+0047
/lcdev block minecraft:gold_block

Forwards and in reverse. char reports what the character became in this chunk and in every palette, part and building that defines it. block reports which characters produce that block. The U+XXXX form exists because palette characters are routinely symbols a chat box will not accept. code review

/lcdev in mypack:mystyle char G

Asks one named file rather than the chunk underfoot, with tab completion over everything that carries a palette. This works outside a city, and in a dimension with no Lost Cities profile at all, which is the situation you are in while editing a file rather than standing in the result. code review

Note

The DevTool is not required by Lost Cities and changes no generation on its own. It is listed here because these are debugging commands and the console-only limitation above is a real obstacle on a dedicated server.

Checking generation is not lagging the server¶

/lostcities stats

Reports average/min/max city-chunk generation time in milliseconds, to chat this time. If a custom city style or a heavy palette is causing noticeable lag, this is the first thing to check. code review

Finding a specific building¶

/lostcities locate <buildingName>

Spirals outward from you, up to 30 chunks, and reports the first 6 matches to chat with coordinates. Useful for confirming a rare/special building you added actually generates somewhere nearby, without a full manual search. Building names are tab-completed live from your loaded registries, so custom buildings autocomplete correctly. code review

Placing a specific building on demand¶

/lostcities createbuilding <name> <floors> <cellars> <pos>

Force-places a registered Building at an exact position, bypassing normal city-generation selection entirely, useful for previewing a building you are actively authoring without waiting for city generation to roll it naturally. Floors accepts 1 to 20, cellars 0 to 10, independent of whatever min/max the building or city style define. code review

Crashes loudly on a bad palette reference

If any part the building references points at a palette character that does not resolve, this command throws a server-side error visible to whoever ran it, rather than a clean chat message. If you see a crash instead of a placed building, check your palette references first.