> But like, isn't YAML still available for configuring things?

For most, yes. But for some included integrations it's UI-only (all of those I've had to migrate, it's been a single click + comment out lines, and the config has been a breeze (stuff like just an api key/IP address + 1-2 optional params).

Where and how are those configs stored? There has to be a backing representation somewhere, right?

In the Home assistant database (which is SQLite IIRC).

UI-generated configs are not stored in the database, they end up in a collection of JSON files in a .storage directory inside your config directory.

And there is no real API for you to interact with it. I would build my own config system if I could, but they don’t seem interested.

SQLite is highly automatable if you can deal with downtime to do your migrations.

I'm sure there are things they could do to better support the power-user engineer use case, but at the end of the day it's a self-hosted web app written in Python that has strong support for plugins. There should be very few things that an engineer couldn't figure out how to do between writing a plugin, tweaking source code, and just modifying files in place. And in the meantime I'm glad that it exists and apparently has enough traction to pay for itself.

Yes - for now. I think the ultimate end-goal is to get rid of the YAML config files, which, makes sense for the median user, but not for power users.

For example, I have my config on GitHub and share various YAML blueprints with a friend who also has the same Solar+Battery system as I do.

Why do you think they would get rid of YAML files? Is that on the roadmap?

For "integrated" stuff, their stance is "UI Must Work". Tracing down the requirements, here:

    https://design.home-assistant.io/#concepts/home
    https://developers.home-assistant.io/docs/configuration_yaml_index
    https://github.com/home-assistant/architecture/blob/master/adr/0010-integration-configuration.md

...usually there's YAML kicking around the backend, but for normal usage, normal users, the goal is to be able to configure all (most) things via UI.

I've had to drop to YAML to configure (eg) writing stats to indexdb/graphana vs. sqlite (or something), or maybe to drop in or update an API_KEY or non-standard host/port, but 99% of the time the config is baroque, but usable via the web-app.