i always thought that Upgrades.ini is simply a list of upgrades that differ in price, build time and Global or Object target = so any can be piked to use it simply as a trigger for smt to change in unit, but now i got stuck cause can't figure out what is missing.

the logic should be:
one must buy Global Player Upgrade > changes CommandSet of unit with CommandSetUpgrade(this works) > new CommandSet contains a button for Object upgrade(Type = OBJECT) > that ought to change WeaponSet with WeaponSetUpgrade(this doesn't work, upgrade button is greyed out).

i thought i could pick any in-game object upgrade to use it per-unit, like say upgrades of Overlord, but... what am i doing wrong?

Does the unit have a productionupdate module?

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that solved everything, thank you! didn't know ProductionUpdate is so important for this as it never was "connected" to upgrades by tags. thought this module is for production of units, my bad.