Not really sure if this is the place to post this, could'nt find a bug thread, but Augustus just offered me a research agreement which i agreed to, only problem is i had 37 gold and even though on the trading table it said 250 gold each, it worked anyway when i accepted.
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Edit, ignore this i think i made a mistake, probably looking at the wrong gold digits, per turn instead of actual amount owned, sorry about that.
did you get negative gold after?
It's been reported AI can go into the negative when they sign.