Why Won't It Spawn

1.0.0 — first release

/whynot structure <id> — stand where a structure should be and be told why it is not.

A mod writing "replace": true on a biome tag deletes every entry the mods below it added. The tag loader wipes them, the game logs nothing, and the structure that depended on one of them simply never appears. By the time the world has loaded, the deleted entries are gone — there is nothing left for you to inspect. This reads the individual packs before they are merged, where the evidence still exists, and names the pack that did it.

Verified against a 40-mod pack. With Towns & Towers, Biomes O Plenty and Terralith installed together, six BOP biomes lose every pillager outpost there is. The command finds it and names the culprit.

What it will not do: it does not call a mod broken for redefining a vanilla list — that is what replace is for, and those losses are reported separately as probably deliberate. And it does not accuse anyone when your biome was simply never in the tag; that is a missing compat patch, not a conflict. Both rules exist because an earlier tool of mine got this wrong and blamed an innocent mod.