macOS sandbox blocks hw.optional.neon sysctl, causing Qt arm64 builds to fail with “Incompatible processor” inside Codex

What version of Codex is running?

codex-cli 0.61.0

What subscription do you have?

Pro

Which model were you using?

5.1

What platform is your computer?

Darwin 24.6.0 arm64 arm

What issue are you seeing?

On Apple Silicon (macOS arm64), Codex’s macOS sandbox mode appears to block access to certain hardware-related sysctl keys, specifically hw.optional.neon. Qt uses these sysctls at startup to detect the CPU features available on the host machine.

When running Qt-based test binaries (or qmake) inside Codex (in default sandbox mode), Qt’s SIMD feature detection fails, and Qt aborts with the following fatal error:

Incompatible processor. This Qt build requires the following features:
    neon

Outside of Codex — in a normal terminal session, or when bypassing the sandbox — the exact same binary runs correctly, as expected. Apple Silicon always supports NEON for arm64, so this failure indicates that the sandbox interferes with runtime feature probing rather than the CPU lacking support.

What steps can reproduce the bug?

Run qmake from macos
codex sandbox macos --full-auto /Users/cave/Qt/6.8.3/macos/bin/qmake
Incompatible processor. This Qt build requires the following features:
neon

What is the expected behavior?

qmake should be able to run.

Additional information

_No response_