UPDATE 2026-09-18 - Script connect_refusal_check_v2.cr replaces earlier version below, adding a test without O_NONBLOCK, which turned out to be OK (whew!) Hola folks, I’m looking for folks who are running macOS and have, or are about to, update to macOS 26.7 (still Tahoe) to run a test. Here’s w…

Some results from running your test program on a mac mini M1. Before upgrading. % crystal run test_socket.cr == Environment macOS 26.6.2 (25G83) kernel Darwin 25.6.0 arch arm64 crystal 1.21.0 evloop Crystal::EventLoop::Kqueue == Check 1: Socket#connect to a closed 127.…

Could you test the raw libc behaviour without O_NONBLOCK to get a full picture? Also I understand the behaviour with kqueue event loop (default) and libevent are identical (works before 26.7, broken after). Is that correct?

Here’s the console transcript for 27.0 with O_NONBLOCK removed. ld: warning: object file (/Users/peterj/.cache/crystal/Volumes-TOSHIBA EXT-work-play-crystal-test-socket-test_socket_2.cr/L-ibG-C-5858S-tackB-ase.o0.o) was built for newer 'macOS' version (28.0) than being linked (27.0) ld: warning: ob…

Thank you. Looks like it’s not me or my colleagues with this issue (since we share a lot of common compliance-related tools on our Macs).

Done, I’ve updated the topic post with v2 of script. Good news with that: == Verdict FAIL closed port raises FAIL localhost falls back FAIL 2nd connect reports refusal ok blocking connect reports refusal AFFECTED: Crystal does not report refused connections on this system. Correc…

2026-09-18 - Results so far. Tables produced by AI and verified by human (moi :grin:). Analysis A, machine by version band (empty cells are untested): Machine ≤ 26.6.2 ≥ 26.7 Yours (arm64) Affected Colleague (arm64) Not affected (15) Affected (26.7) e4pjacob (arm64) Not affected (26…

Can you check if Fix: Socket#connect on macOS 26.7 by ysbaddaden · Pull Request #17436 · crystal-lang/crystal · GitHub fixes the issue? That’s basically your monkey-patch, applied to the evloops and limited to macOS.

Oh, @straight-shoota realized that the nonblocking loop was just wrong. I updated the PR with the corrected loop. Hopefully it works on macOS 26.7 @noggingly ?

Thanks for submitting PR for the socket connection issue that I ran into. :folded_hands: I built Crystal from source from your branch and ran it against the v2 script. == Environment macOS 26.7 (25G229) kernel Darwin 25.6.0 arch arm64 crystal 1.22.0-dev evloop Crystal::E…

Socket connection error after macOS 26.7 update

Help & Support

nogginly September 27, 2026, 5:49pm 11

Thanks @ysbaddaden and @straight-shoota for hearing me out and getting a fix put through.

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Socket connection error after macOS 26.7 update

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