I’m thinking of blades in the dark. I think there is a true negotiation process imbedded in there. But yea, it’s a stretch to call most d&d play a negotiation IMO. The whole idea that it’s a negotiation just because you can back out of an agreement at any time would make basically everything a negotiation - which to me deprives the concept of negotiation of real meaning. But all this is semantics. If what they mean by negotiation is simply not withdrawing consent I can understand what they are saying, even if I think it’s a really strange way to say it. Most of Bakers concepts seem to go this direction. I think I’m just going to start calling it ‘Bakerian language’.
All that said
@clearstream referred to some rare edge cases where what I’d call negotiation may occur in d&d. I think I agree that it can happen - specifically if the agreement is revealed to not be as clear as initially believed. A more common occurrence of this is the DM springing a detail on the player that his PC probably should have noticed or at least had a chance to notice, but doing so after the action declaration. I think I would call what’s happening negotiation.
Here is one simple and in my view reasonably typical example from D&D play:
The GM tells the players that their PCs arrive at a town. One of the PCs says "I want to go and see a metal-worker, to see if I can buy a silver dagger or some silver-tipped arrows to deal with that werewolf that's been tracking us." The GM considers this action declaration, consults their notes which mention "a typical town" but say nothing about the availability of silvered weapons, decides there's a 50-50 chance, makes a roll, which comes up negative, and then tells the player "You find your way to a weaponsmith, but they don't have any silver or silvered weapons on hand." Then the player says, "We've got that sack of silver pieces, right?" and another player nods, and the first player says "Can the weaponsmith do it if I supply the silver", and the GM thinks about this . . .
Here's another:
The PCs are exploring a dungeon. The GM tells them that suddenly, around the corner in front of them, comes a group of 3 ogres. The PCs are surprised! Then one of the players says "Hey, did you take it account of <this alertness-type feature that I got as a result of levelling up last session>?" The GM replies "Oops, I forgot about that. OK, so the ogres come around the corner but you're not surprised - you hear them coming and have time to ready your weapons and roll for initiative!"
There are endless variations on the above in D&D, because of all its intricate little components: did you remember my protection effect, my combat buff, the fact that I'm doing fire damage, etc, etc.
Here's another:
The GM tells the players, based on extrapolation from whatever has happened so far, "OK, it's dark and you're all starting to get cold." One of the players says "We light a fire." The GM replies "OK, tell me how. Does anyone have a tinderbox? What are you using for fuel?"
The GM seeking more information from the players before assenting to their suggestion that a certain sort of craft-y or creation-y outcome is part of the fiction is very, very common in D&D play.
Here's another:
A player says, "My magic-user wants to research a spell that will let us track the location of the <whatever>." And so the GM pulls out the rules chapter on spell research, and the player and GM start to work out what the PC has to do to research this spell.
Here's another:
The group are resolving a combat. A player says "I attack the Hobgoblin!" The GM replies "How do you do that? You've just finished killing the Bugbear, and the Hobgoblin is on the other side of the room from where the two of you were fighting?" "OK, I move across the room first. Can I do that without being attacked by the giant ape on the way?"
And another:
The GM tells the players that their PCs come to a dead-end room, with a ceiling about 20' high. The player of the Half-Orc barbarian says "The Halfling gets up on my shoulders and starts tapping the walls as high up as she can to see if they're hollow." The GM asks, "OK, what's your DEX? Is either of you trained in Acrobatics?" And the player responds, "Redgar" - the human fighter with 18 STR and 16 DEX - "joins us, so that Redgar and I are really stable with arms around one another's shoulders and the Halfling stands on both of us." And so the conversation goes on . . .
That last one is inspired by Gygax's example of play in his DMG.
As these examples illustrate, and as I hope is reinforced by the myriad other possible examples that they bring to mind, coming to agreement on what is happening in the fiction is at the core of D&D game play.