[BUG] v2.1.257 aborts at launch on macOS 12 (dyld: _DNSServiceGetAddrInfoEx) — auto-updater installs it and leaves the install unable to start

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

Auto-update moved me to 2.1.257 on macOS 12 (Monterey), and Claude Code now aborts before any app code runs. Every invocation dies the same way, including claude --version:

dyld[51991]: Symbol not found: (_DNSServiceGetAddrInfoEx)
  Referenced from: '~/.local/share/claude/versions/2.1.257'
  Expected in: '/usr/lib/libSystem.B.dylib'
zsh: abort      claude

DNSServiceGetAddrInfoEx doesn't exist in macOS 12's libSystem. A symbol probe confirms it: the older DNSServiceGetAddrInfo resolves fine, the Ex variant doesn't, so dyld kills the process (SIGABRT, exit 134).

I know macOS 12 is below the documented minimum (macOS 13.0+ per the setup docs), so this is not a request to support Monterey. The bug is in how the floor lands:

1. The background auto-updater installed 2.1.257 and repointed ~/.local/bin/claude at it on a host it can't run on. It did this on two user accounts on this machine. Nothing checks the OS floor before the switch, and nothing rolls back when the new binary can't execute, so the install is simply dead until you manually reinstall an older version.
2. There's no minimum-OS message anywhere in the failure. A raw dyld abort reads like a corrupted install, not "your macOS is too old."
3. The 2.1.257 changelog doesn't mention the change that made the floor real.

What Should Happen?

Any one of these would have avoided a bricked install:

• The updater compares the host OS against the new binary's declared minimum (it's right in the Mach-O header, LC_BUILD_VERSION minos=13.0) before switching the launcher, and skips the update with a notice on hosts below it.
• Failing that, a rollback: the previous working version is still sitting in ~/.local/share/claude/versions/, so when the freshly installed binary can't even start, the launcher could fall back to it.
• At minimum, a clear message: "macOS 12.7 is below the minimum supported version (13.0)" instead of a dyld abort.

And a secondary ask, freely ignorable: if this really comes down to the one hard reference, weak-linking DNSServiceGetAddrInfoEx with a runtime fallback to plain DNSServiceGetAddrInfo would keep macOS 12 running as best-effort. This machine can't go past Monterey, so 2.1.252 is where it ends otherwise. Happy to test a build. The three items above are the real ask though.

Error Messages/Logs

$ claude --version
dyld[59079]: Symbol not found: (_DNSServiceGetAddrInfoEx)
  Referenced from: '~/.local/share/claude/versions/2.1.257'
  Expected in: '/usr/lib/libSystem.B.dylib'
zsh: abort      claude --version
$ echo $?
134

Steps to Reproduce

1. Intel Mac on macOS 12.x with a working native install of 2.1.252
2. Let the background auto-update run (or install 2.1.257 directly)
3. Run any command, e.g. claude --version
4. Immediate dyld abort, exit code 134

Claude Model

None

Is this a regression?

Yes, this worked in a previous version

Last Working Version

2.1.252

Claude Code Version

2.1.257 (Claude Code)

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

Details that may save you the bisect:

• 2.1.252 launches and works; 2.1.257 aborts. 2.1.253 through 2.1.256 were never published (their release manifests at downloads.claude.ai/claude-code-releases/<v>/manifest.json return 404 while 2.1.252 and 2.1.257 return 200), so these are consecutive releases and the break is exactly at 2.1.257.
• 2.1.251, 2.1.252, and 2.1.257 all already declare LC_BUILD_VERSION minos=13.0.0. Older builds ran on macOS 12 anyway because dyld only fails on a missing symbol; 2.1.257 is the first release that actually references a 13.0+-only symbol.
• This is a repeat of a known pattern: #50383 (v2.1.113 vs macOS 11, _ubrk_clone) was the same dyld failure class, and #50456 reported the same silent auto-update-into-a-broken-build behavior on macOS 11 back in April. Both went stale-closed.

Workaround for anyone stuck on macOS 12:

curl -fsSL https://claude.ai/install.sh | bash -s 2.1.252

then add "DISABLE_AUTOUPDATER": "1" to the env block of ~/.claude/settings.json, otherwise the next background update quietly reinstalls the broken build. You lose Fable 5.1 (it needs the newer CLI), but the install works.

Environment: macOS 12.7.4 Monterey (21H1123), Intel x64 (2015 MacBook Air), native installer, zsh.

dyld: Symbol not found: (_DNSServiceGetAddrInfoEx)
Referenced from: '/Users/.../.local/share/claude/versions/2.1.257'
Expected in: '/usr/lib/libSystem.B.dylib'

$ claude --version
2.1.258 (Claude Code)