Re: [Bug Report] 2.4.3 on macOS: anvil panics at anvil-connection.c:727 on every IMAP client handshake

On 18/04/2026 05:15 EEST I-K-D-T--- via dovecot <dovecot@dovecot.org> wrote:

Hi Dovecot developers, I'm hitting a reproducible anvil panic on macOS when any IMAP client tries to connect. Every client handshake triggers an i_unreached() assertion in anvil-connection.c:727, causing the anvil child to be killed with SIGABRT. Dovecot keeps restarting anvil, but every subsequent connection attempt triggers the same panic, so the service effectively cannot accept logins.

Environment

• Dovecot: 2.4.3 (e278b1e09b), Pigeonhole 2.4.3 (0bf9ee48) -- from Homebrew
• OS: macOS 15.6 (Sequoia, Darwin 24.6.0, arm64/Apple Silicon, APFS)
• Mail client: Mozilla Thunderbird 149.0.2
• Dovecot started via sudo brew services start dovecot (launchd)

Reproducing

1. Fresh macOS install of Dovecot 2.4.3 via Homebrew.
2. Configure a minimal single-user IMAP setup with passdb static / userdb static, SSL on port 993 with a self-signed cert, Maildir storage (config at end of this mail).
3. Start Dovecot as root via launchd (sudo brew services start dovecot).
4. Connect any IMAP client to localhost:993 (I used Thunderbird 149 with a permanent cert exception for the self-signed certificate).
5. The client hangs / reports "server closed the connection" / sees no folders.
6. dovecot.log fills with repeated entries like the following:

anvil: Warning: conn unix:anvil (uid=0): Handshake with duplicate
service=imap-login pid=-1 - replacing the old connection

As workaround, you probably want to disable anvil usage. Your problem seems to be that pids are -1. That sounds like there is some problem with pids, maybe sandbox or some other filter? Did this work with 2.4.2?

Aki