The "AI will accept" indicator seems to be broken.

[jjjdddsss]

I noticed a few times that if you get a peace deal or trade to get exactly 0 it changes to a tick as if they will accept but they don't actually accept until you get to at least 1. I assume this isn't intended and I'm guessing someone either added or missed an "=".

 

[TehJumpingJawa]

I've had +1 deals rejected.
So yeah, there's definitely something off there.

Perhaps it was change of circumstances between the deal being created, and the recipient receiving it.....
Though formulating an identical deal straight afterwards causes the same sequence of events, so it seems more likely a rounding inconsistency between the UI & the diplomacy AI.