I don’t have move suggestions, but some SDK maths (though I’m not too confident about my numbers): After the B7 variation white has 13 points on the left, black gains 8 in the corner. After black loses the B8 ko, white has 25 points, black gains none. So black loses 25 - 13 + 8 = 20 points, if black goes for B8 instead of B7 and loses the ko.
So black would need ko threats that are worth 20 points or more?
Suggestions, questions and answers… I didn’t want to be restrictive ofc.
Can we have an ‘I don’t know’ option next time?
Again, is peep at J11 a thing or K10?
I think that’s about right. And I think white needs ~60 point ko threats or internal threats.
White doesn’t have 60+ points threats I think, but white has some internal threats and white will capture the ko first.
So the question is if black has more 20+ point threats than white has internal threats.
Those ideas are similar to the variation in the diagram above from move 7 (strengthening the center for black).
Except that the peep at J11 allows white to defend with perfect shape (solid connection), and black doesn’t get any other forcing moves around K10. So the J11 peep seems less effective than the J12 wedge in that variation.
The 2-space jump to K10 instead, expands the center a bit, but it is not a direct threat to white’s stones around J12, so white will probably ignore it and play elsewhere. So K10 feels a bit slow to me / too small to give up sente.
.
Be nice to Kitty, she is new to the forum 
For simplicity-sake, what is the basic framework white would expect if black can push the boundary all the way at the 11th line? Let’s say white can live on the LR with S9, and black doesn’t get to reduce the left side and keep it as it is.
That must be pretty rare in any game, right? Especially when the word “threats” is in plural form? 
Anything that big are usually just local threats.
Now you understand why I preferred O5 N7 than any defense move like D18 (or even F12 K17). Any moves threatening to break in the lower side black moyo, or take out the LR black stones are really big ko threats.
I can see A5 and then D6 for white (black can back off after those moves, but then B7 would have been better). Black has F12 (and F14 if white connects at E13) and probably K17 and something that kills the lower right if unanswered (maybe O7 followed up by S6). That would be just enough for black, as white takes first.
If white answer F12 with E13 connect, D15 can also be a ko threat for black. Not to mention all the follow-up after K17 or M17, which would make black live inside white’s moyo or break through the moyo, they are all threats that are big enough I think (depends on how white answers, or hard to compare), but more likely white would run out valid ko threats quick (2 locally and maybe one in the LR) and has to take the ko and keep the left side or risk losing more.
Thank you Claire. The judgement is beyond me, but your made the evaluation easy for me to follow.
Anything more to add to the discussion ?
I don’t think that white O5 or N7 or any other white move in the lower right is a 60+ point ko threat.
And if white gets in O5 before the ko starts (hoping to create aji and/or large ko threats), black could refuse to cooperate and just respond solidly at N4 (at least I would always do that with black to keep the shape thick and avoid bad aji). Then white still doesn’t seem to have any 60+ point ko threat in the lower side / lower right area.
So I think white has this option to strengthen their lower right group whenever they have sente again (but it would probably cost them their sente):
In that vote, defending the lower right with N7 lost to creating a large moyo on the upper side with K12).
Who said white has to back off to play N7 if black back off to N4 in respond to O5? The corner 4 black stones are not alive.
Now white has the ko as well, if black tried to start a ko, white can refuse to play the ko and choose to take the LR corner in exchange for the top white group of the left side.
If 3 is played as an attempt for a 60+ point ko threat and black resolves the ko (killing lower left) to cash-in 60 points, then black could respond differently with 5 and save the corner with P2 (at that point black can afford to lose 30-ish points on the lower side and still end up winning).
So yes, white may be able to create 30-ish point ko threats, but those are too small to win the ko in the lower left.
If black start the ko at the moment after move 3? Then white doesn’t have to follow through the ko, just take the ko where black has to deal with both the lower left 4 stones is ko to live and the lower side black moyo is breaking through the bottom.
When there is no large ko active, white O4 is just a forcing move (black responds at O3).
Why would black ignore white O4 to create the ko for the lower left?
I think black would only ignore O4 if the 60 point ko is already on the board and white plays O4 as a ko threat to recapture the ko.
So white only gets O4 and N3 in your sequence when black gets to capture the whole lower left unconditionally in return, i.e. in this kind of situation:
That also goes for any other forcing moves by white. When the ko is not active yet, black just responds. Black is not so deparate to create the ko that he ignores any white forcing move before the ko fight even started.
Before the ko started, white could try to make some exchanges to prepare a very big ko threat at A like this:
But when white makes that kind of exchanges in advance, black is happy to get extra profit and extra weaknesses in white’s lower right group, so black may not even create the ko in the lower left anymore.
So I don’t think white can get the timing right to make O4 an effective ko threat.
Also, I think that cutting at N3 to prepare a large ko threat is refuted by the wedge at P6:
But anyway, white played D18 instead and it is black’s turn now.
