[Antrax]

I was dealt a good 31-count. In GIB's system, the way to bid strong balanced hands seems to be:
2NT: 20-21
2♣ then 2NT:22-24
3NT: 25-27
2♣ then 3NT:28-29
2♣ then 4NT: 30-31
2♣ then 5NT: 32+

At least, that's what the bid descriptions say. However, when I upgraded by 31-count and the auction went
2♣-2♦
5NT

GIB responded 6♦ saying "declined, no ♦K or Q". In other words, it treated 5NT as GSF for ♦. It had no extra diamond length, so it's not a case of it pulling to a 6♦ slam with a wrong explanation - rather it took 5NT different than what the bid description promised.

It's a rare sequence, yet this is the third time I remember 5NT popping up as a problem bid, so it might be worth it to just correct the explanation.

[georgi]

Thanks for reporting.

2♣ followons are main point for next version, but meanwhile this is fixed.

5NT crossed cases where it was used as GF as something like-> Grand slam force (D trump) -- 2+ D; 31+ total points

So here as fit is not established 5NT would be treated as just balanced huge HCPs hand ( same explanation as described above ), but GIB will not bid automatically 6♦.

Maybe also 5NT needs limit as practically it's 31-32. With 33 6NT would be bid directly, although very rare hand but still.