Dungeon World explicitly assumes the existence of a party: bonds simply don't function without other PCs to play off of. But can DW be played as a duet?
Stipulate that I'm already experienced running duets in D&D-like systems; I'm not looking for system-agnostic duet advice. [How] Can DW be run as a duet?
But you will need house rules and it might not work that well
In a video (around 27:45min) on his YouTube-Channel, Adam Koebel himself mentions that
Dungeon World as written does not work for 2 players, like, flatout doesn't. You'd have to change bonds
In the comments on the video he confirms that by "2 players" he refers to 1 GM and 1 Player.
This should be easy to answer: Bonds refer to other player characters. Of which there are none. But how would we change bonds, then?
One idea would be to allow bonds with locations - But as stated in the answer to that question, there would be no real way to trigger
Take +1 ongoing to aid or interfere with the target of the bond.
This might be a big problem. My Advise: instead, allow bonds with NPCs that are important in the game.
Please note that this is the way I would do it, after playing with two players only for two or three sessions, ignoring bonds completely. See below for more information on my personal experience
Why do we need bonds? They are a great way to a) interact with the world around the players and even tell stuff about them (I once ran a con with Boromeo, the Warrior is a great example of that) and b) to gain experience. Both of those work very well with NPCs, too.
The GM-Move I just mentioned in combination with the general problem of having only one PC in your game might be a big problem. The solutions to a problem will not be all that different and thus might either get boring for both the player and the GM, or they might lead to the GM trying to "mix things up" and resulting in the player beeing unable to use his character's abilities to their full extent. As a GM, you have to be aware of that!
If I were to think about it, you could certainly try to a) encourage the player to dabble in the multiclassing-possibilities that DW offers, or even give him one or two additional stat increases and/or moves. I have not done that myself, though, just as a fair warning.
I have tried Dungeon World One-on-One for a few sessions, with different characters (but always me as the GM and the same player) - and I was not really happy. First of all, we chose to just ignore bonds, which was a big mistake for the reasons I outlined above. The second problem was that we just would not run into that many interesting situations. Either the player steamrolled through challenges and situations, or he was totally lost with no possibility other than fail. It is really hard to find a middle ground on that (see the "provide an opportunity"-Point I made earlier)
A quick look around on the internet shows me that you are not the first person to look for help on this topic. And most people seem to say the same: It's not really the perfect game and it will be hard to do this.
You could try, though. Test it out for one or two sessions, think about a way to change the bonds (see my untested suggestions for inspiration) and choose a class that can do more than one thing. I found the ranger to be pretty good at that, if you want to run a wilderness-adventure. The companion is a great thing to have when there is no party. Also, think about Hirelings for the player. You will quickly see if you like it or not. The first one or two sessions should already be a good indication.
I play DW with my wife, where we each both play and GM at the same time. (It's not the only game we have running, but for some reason it's the funniest one.) Basically:
We come up with situation together.
When one person (as a player) makes a move, the other one (as a GM) tells the result.
If we need to make something up on the spot, either one of us has a good idea immediately, or we come up with two outcomes and choose the one that sounds better.
And of course you have to have a clear idea on metagaming, since nothing is hidden from you.
The Discern Realities podcast has a segment where the two hosts run a one player (and one character) Dungeon World adventure. The first few sessions really highlight some of the difficulties in adapting the system. Play gets a bit more fluid by episode 21 (where I am currently). You might want to give it a listen.
Spoilers:
One of the problems that made the game brittle was a series of bad rolls by the player. Basically three or four bad rolls in a row is a "Total Party (of one) Kill." I also think the GM made the snake and the situation a bit too deadly for one thief to deal with. 1d10+2 damage is a lot when you don't have the ability to get away or share the damage around. So unless you want to chew up characters you might have to dial back the hard moves if you are used to a multi-player game that's somewhat deadly.
If I were to do it I would consider giving the player two or more characters and/or hirelings with skills different from the player characters. Maybe do something like funnel-world where the player has a collection of PC's that they won't be super attached to.
In place of bonds you could consider adjusting the XP to Level requirements down to reflect a loss of an XP source.
