Sorry, I won't be able to offer much debug info, but the current stock
cworth/master segfaulted for me with only the "tag:inbox" search.

Output:
/home/spaetz/mail/INBOX/new/...2c57e:2,: No such file or directory
Segmentation fault (core dumped)

A "notmuch new" fixed the segfault, something is not as robust as it
should be (or used to be), it seems. I'll dig deeper if it occurs again.

Sebastian