Hey @ringohoffman - I took a cursory look at upgrading to pydantic v2, it wasn't just a straight upgrade (I had some trouble with the nested configuration models for default configuration) but definitely something that's high on the list!

Re upgrade: I noticed the following:
After pydantic/pydantic#6722 I realised tomlkit parsed into its own types rather than builtin Python types, and Pydantic V2 isn't coercing them like v1 so it "looks like" valid TOML is invalid according to the Config model.

I tried swapping tomlkit for tomli and tomli-w, as tomli does parse TOML into builtin Python types - however, tomli_w reformatted the TOML file when it was written out. Maybe not the worst crime but I was reluctant to just throw that in. I didn't really want to use two TOML parsing libraries (especially as there's also a builtin one in 3.11+), so need to figure a way out to make all these things work together - hoping there's a "coerce" setting for pydantic v2 models that I've missed