Unexpected delay on folder load after scanning messages about neomutt HOT 5 OPEN

What's in your index_format? Does it happen with a minimal one such as %s?

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What's in your index_format? Does it happen with a minimal one such as %s?

Exactly the same problem. I've also disabled all hooks.

For the record, this is what I have:

index-format-hook  date  "~d<1d"    "%{%H:%M%Z}"
index-format-hook  date  "~A"       "%d"
index_format="%4C %Z %-10@date@ %-15.15F %4c%?M?/[%M]? %?H?[%H] ?%s"

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Can you run with -d10 and see if something happens in the logs? I think it would be in ~/.neomuttdebug0

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Actually, it's not unreasonable to me that sorting / threading 419009 messages takes a couple of seconds. Does it go away if you set use_threads=flat?

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No sizeable difference with flat threads. With debug output, I found that while it's delaying the folder load, it outputs these two lines presumably for every message in the folder, and there are about half a million in that folder where I feel the pain the most:

[2024-06-19 14:03:55]<2> maildir_move_to_mailbox() Considering·
[2024-06-19 14:03:55]<2> maildir_move_to_mailbox() Adding header structure. Flags: OR
[…]
[2024-06-19 14:04:01]<2> maildir_move_to_mailbox() Considering·
[2024-06-19 14:04:01]<2> maildir_move_to_mailbox() Adding header structure. Flags: OR
[2024-06-19 14:04:02]<M> mutt_sort_headers() Sorting mailbox...

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