Apple New Added 9 October 2026

macOS: zsh: killed ./app (Killed: 9) on Apple silicon

On Apple silicon every arm64 executable must carry a valid code signature, even if only an ad hoc one, and the kernel kills it at launch if the signature no longer matches the file. The program is usually fine: something changed it after linking, such as install_name_tool, strip or a patch script, or it was copied over the top of an existing file. There is no Gatekeeper dialog, so it looks like an instant crash.

Quick fix

Read the commands before running them. Anything that restarts a service, deletes data or changes permissions should be tried on a non-production system first.

Quick fix

# Is the signature intact?
codesign --verify --verbose ./app
codesign -dv ./app 2>&1 | grep -E 'Signature|flags'

# The kernel log confirms it
log show --last 5m --predicate 'eventMessage CONTAINS "CODE SIGNING"' | tail

# Re-sign ad hoc after editing the binary
codesign --force --sign - ./app

# Replacing an installed binary: delete it first, then copy,
# so the kernel does not reuse the cached signature of the old file
rm /usr/local/bin/app && cp build/app /usr/local/bin/app

How to diagnose Apple errors

macOS developer errors concentrate around three subsystems: the command line tools (xcrun and the active developer directory), the dynamic linker (dyld, library paths, and code signing), and Gatekeeper / notarisation. Apple Silicon added a fourth axis: architecture mismatches between arm64 and x86_64 binaries, which usually surface as confusing "library not loaded" or "bad CPU type" messages rather than as an explicit architecture error.

If the quick fix above does not resolve it, work through these steps. They apply to this whole class of error, not just to this one message, which is usually what saves the time.

Check the active developer directory first with xcode-select -p. After every macOS or Xcode update this can point at a path that no longer exists, breaking git, compilers and package managers all at once.
For dyld errors, run otool -L /path/to/binary to list what it actually wants, then verify each path exists. DYLD_PRINT_LIBRARIES=1 shows the resolution order at runtime.
Confirm architecture with file /path/to/binary and uname -m. On Apple Silicon, a Rosetta shell reports x86_64 and will silently install the wrong Homebrew prefix.
Homebrew lives at /opt/homebrew on Apple Silicon and /usr/local on Intel. Permission errors under /usr/local on an M-series Mac almost always mean a Rosetta/native mix-up.
For Gatekeeper and notarisation, use spctl -a -vvv to assess a bundle and xcrun notarytool log to get the actual rejection reason. The submission status alone tells you nothing useful.

Tools worth reaching for

xcode-select -p
otool -L
codesign -dv --verbose=4
spctl -a -vvv
xcrun notarytool log

Authoritative references

Primary documentation for this error, worth reading before applying any fix in production.

developer.apple.com developer.apple.com

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