Glad you like it Polycrates!
I added "stealth bomber bug" on my todo list after you pointed it out, thank you for mentioning it. I'm done updating forum threads so I'll take a look into it right now.
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Just looking through some things... here's one difference in their Units table entries:
Bomber:
<Special>SPECIALUNIT_FIGHTER
Stealth Bomber:
<Special>SPECIALUNIT_STEALTH
This <Special> attribute is used by four things: great people, fighters, bombers, and missiles. I suspect it's a way of dealing with special AI code.
However, both units have:
<CombatClass>UNITCOMBAT_BOMBER
In the UnitPromotions file, the
UnitPromotions_UnitCombats table lists the UNITCOMBAT_BOMBER class as capable of receiving the various promotions. This CombatClass is typically what controls which promotions a unit can get.
For example, the reason subs can get the land-bombardment promotion is because they're the same combat class as other naval units (even though that promotion is useless for them and their combat class
should be different).
Since their combat class is the same between the Bomber and Stealth Bomber, and I don't see any other major differences, my likeliest conclusion is it's some internal, hardcoded bug with the 'special' attribute. I'm not really sure what negative effects changing that attribute might have for the stealth bomber, and I suspect it'd just replace one problem with another.
The other possible, though less likely conclusion is it's a bug with the free promotions the two units get. The stealth bomber starts with evasion and air recon promotions the bomber does not have. It's very unlikely this is causing a problem, though theoretically possible. I looked at both promotions' entries in the UnitPromotions file and didn't see anything that might indicate the issue.
In summary, everything in the XML files indicates the stealth bomber
should be able to get promotions. It's most definitely a bug, but likely an internal issue, possibly with handling of SPECIALUNIT_STEALTH.