`env.keystonesAdded` was no longer getting reset before we start merging keystone effects. The new `modLib.mergeKeystones` keeps that table on the environment, and `wipeEnv` does not clear it. After the first calculation pass the table is full; on the next pass (any time the build recalculates by toggling a flask, change a config option, etc.) the merge sees every keystone as “already added” and skips adding their modLists. So every keystone loses its effects after the first recalculation.
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