[Atp] Re: ATP records from arbitrary JSON

[Ryan Barrett <[e-mail]>]

This is a good one! And the good news here is, ATProto largely already
supports arbitrary JSON-shaped data in records. It's not encouraged, for a
number of reasons, but it is explicitly provided for. The lexicon spec includes
an unknown field type <https://atproto.com/specs/lexicon#unknown> that
designers can use to indicate that they expect arbitrary data, but you can
also put arbitrary data (of any type, including objects) into fields that
*aren't* defined in a lexicon. PDSes and other consuming services are
explicitly required to allow all this
<https://atproto.com/specs/lexicon#authority-and-control>, for a few
reasons, eg changing lexicons (backward compatibly) over time.

(...subject to some caveats, like you mention, eg floats and some $...
names!)

On Fri, Jul 24, 2026 at 5:04 AM Volker Mische <[e-mail]>
wrote:

> Hi all,
>
> over the past few weeks I realized that I started the whole floats
> discussion from within too deep into the rabbit hole. I want to start
> again from a higher level, hence a separate thread: Do we want ATP
> records to be able to support arbitrary JSON?
>
> I think the answer is: yes, as much as we can.
>
> In order to reduce the edge cases, let's assume for this thread that the
> "arbitrary JSON" is valid I-JSON [1].
>
> Of course fully arbitrary isn't possible, which is true for all JSON
> based systems that need to signal custom things. In Apache CouchDB it is
> top-level fields starting with an underscore which are reserved, hence
> cannot be used in your arbitrary JSON input. For ATProto it is all
> fields starting with a dollar sign.
>
> So if your data doesn't contain any key starting with a dollar sign,
> then I think it should be possible to store it as an ATP record without
> any further limitations.
>
> I hope we can find agreement that this is a goal to pursue and we can
> then take the next step and discuss on how to get there.
>
> [1]: https://www.rfc-editor.org/info/rfc7493/
>
> Cheers,
>    Volker
>
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