AF13

The Zod v3 adapter reached the backstop it keeps for a schema kind its blank walker has no case for, and defaulted that field to null.

In development this reads:

attaform zod-v3 adapter: unsupported schema kind '<kind>' on form '<form key>'. Defaulting the field to null. Use a supported zod kind (object/array/record/string/number/etc.) at this path.

The production message carries the same two values after the code. There is no concrete kind to show in their place, for the reason below.

What happened

Nothing you did, and nothing your schema did. This is a backstop, and no Zod v3 schema reaches it.

Every kind the v3 adapter recognizes has its own case in the walker that derives blank values, and a typeName the adapter does not recognize reads as unknown, which has a case of its own: no blank is derived and the slot stays absent until something writes to it. That is the opaque carry AF03 describes, and it is what leaves this backstop with nothing to catch. The Zod v4 adapter wires the same hook to a silent fallback for the same reason.

The advice in the message is older than the behaviour around it. It dates from the era when Attaform kept a list of supported kinds and refused the rest, which is exactly what AF02 and AF03 were retired for. Every Zod kind is welcome. The only rule left is that the schema root must hold keys, which is AF15.

What to do

Treat a real sighting the way you would AF11 or AF12: an Attaform invariant broke, rather than a schema needing a reshape. Open an issue with the reported kind and the schema at that path, and leave the field exactly as you wrote it.

The schema contract lists the blank Attaform derives for every kind.