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I actually only used an XState state machine with JSON configuration and used that data as part of the prompt. It worked surprisingly well.

Since it has an okay grasp on how finite state machines and XState work, it seems to do a good job of navigating the tree properly and reliably. It essentially does so by outputting information it thinks the state machine should use as a transition in a JSON object which gets parsed and passed to a transition function. This would fail occasionally so there was a recursive “what’s wrong with this JSON?” prompt to get it to fix its own malformed JSON, haha. That was meant to be a temporary hack but it worked well, so it stayed. There were a few similar tools for trying to correct errors. That might be one of the strangest developments in programming for me… Deploying non-deterministic logic to fix itself in production. It feels wrong, but it works remarkably well. You just need sane fallbacks and recovery tactics.

It was a proprietary project so I can’t share the source, but I think reading up on XState JSON configuration might explain most of it. You can describe most of your machine in a serializable format.

You can actually store a lot of useful data in state names, context, meta, and effect/action names to aid with the prompting and weaving state flows together in a language-friendly way. I also liked that the prompt would be updated by information that went along with the source code, so a deployment would reliably carry the correct information.

The LLM essentially hid a decision tree from the user and smoothed over the experience of navigating it through adaptive and hopefully intuitive language. I’d personally prefer to provide more deterministic flows that users can engage with on their own, but one really handy feature of this was the ability to jump out of child states into parent states without needing to say, list links to these options in the UI. The LLM was good at knowing when to jump from leaves of the tree back up to relevant branches. That’s not always an easy UI problem to solve without an AI to handle it for you.

edit: Something I forgot to add is that the client wanted to be able to modify these trees themselves, so the whole machine configuration was generated by a graph in a database that could be edited. That part was powered by Strapi. There was structured data in there and you could define a state, list which transitions it can make, which actions should be triggered and when, etc. The client did the editing directly in Strapi with no special UI on top.

Their objective is surveying people in a more engaging and personable way. They really wanted surveys which adapt to users rather than piping people through static flows or exposing them to redundant or irrelevant questions. Initially this was done with XState and no LLM (it required some non-ideal UI and configuration under the hood to make those jumps to parent states I mentioned, but it worked), and I can't say how effective it is but they really like it. The AI hype was very very strong on that team.