[amaliaa]

Is it my idea or anybody else ?: robot almost never lead in partner's suite: some time this
may be right, but how can be right never to lead partner's suite?

Let me know please what do you think...

[Antrax]

This is a well-known issue (for example: http://www.bridgebas...suit-oercalled/, http://www4.bridgeba...8891-gib-leads/). Basically GIB has no rule that tells it "you should lead partner's suit", "you should return partner's lead" or "you should lead your strongest suit", all three typically used by typical humans. The reason is deep-rooted in the way GIB works (explained well in those two threads, as well as others). On the plus side, in a theoretical sense, its leads are better than what you would get from those rules - you just need to learn to adapt and not assume it operates by those principles.

[johnu]

I recently played a hand where I bid 2 suits, the opponents ended up playing the contract in a third suit, and my GIB partner led the 4th suit, underleading an ace to do so I think even GIB was surprised that was not the winning lead

[barmar]

I suggest anyone interested in understanding how GIB leads read the books "Winning Notrump Leads" and "Winning Suit Leads" by David Bird and Taf Anthius. They use computer simulations to determine the best leads with various holdings after particular auctions, which is very similar to how GIB defends (although GIB doesn't simulate as many hands as they did, because it has to play in reasonable tempo). I've found that GIB's leads frequently match what they recommend. That often means making passive leads in many more situations than conventional wisdom suggests; as a result, returning the suit is usually not the best defense.

GIB has no way of knowing if your lead was passive or attacking.