This directory: /usr/local/src/reticulum/LXMF
contains my GitHub fork (https://github.com/jlpoolen/LXMF) of Mark Qvist's: https://github.com/markqvist/LXMF which, incidentally, is a public mirror of some git server served up through Reticulum -- the source is not provided.

I created an empty project in my Forgejo server: LXMF-specification at  https://salemdata.net/repo/jlpoole/LMXF-specification
and I added my Forgejo instance as a remote repository identified by "forgejo".

I added some files based on a ChatGPT chat, see ChatGPT_1.md.
So, for your first task:  Using the lxmf-update skill, inspect upstream LXMF and determine the exact serialized structure of an LXMessage. Do not edit SPEC.md. Produce a report listing every field, its source-code origin, and whether its behavior is confirmed by a test vector.