Hello Michael,

> What you've sent didn't help; the problem is indicated much earlier in
> the debug file. This is why I always insist in sending the whole debug
> information.

I apologize, I thought it was just irrelevant noise until what looped over
and over, but it was indeed crucial.

All your explanations make sense now. But I'm still not sure if it's an
issue with Tramp or Project? Trivially speaking, we could also ask Project
to not look for vc related information over Tramp, but maybe some people
rely on this? After all, I'm the first one to report that bug as far as I
know.

> sudo's session timeout after ca 5 minutes due to inactivity on the
> wire.

This led me to investigate something. I told you it happened when
using Tramp with sudo. But now I tested it WITHOUT sudo and I can
reproduce the same errors. Here are the steps:

1. start an Emacs session with the command below (replace "x" with your own
   server)

--8<---------------cut here---------------start------------->8---
# emacs -Q -l project --eval '(setopt project-vc-extra-root-markers (quote (".project")))' --eval '(setopt project-mode-line t)' '/ssh:x:'
--8<---------------cut here---------------end--------------->8---

2. after successfuly connecting do:
   M-x tramp-cleanup-all-connections

As soon as the connection is closed the same errors happen.

> --8<---------------cut here---------------start------------->8---
> (add-to-list 'tramp-connection-properties (list (regexp-quote "/sudo:root <at> x:") "session-timeout" nil))
> --8<---------------cut here---------------end--------------->8---

> Does this work for you?

I did try it in my init.el, and it cancels the automatic disconnect, but as
soon as I M-x tramp-cleanup-all-connections or simply kill the process,
the errors appear.

I can live without having the project name in the mode line, so I removed
(setopt project-mode-line t)
but kept (setopt project-vc-extra-root-markers (quote (".project")))

It seems the problem doesn't happen anymore (tested with 30.1 and master),
yet I'm almost confident even with that setting only it was crashing
Emacs at some point, I will try in my main config to see if it happens
again later.