SIGKILL (Signal 9): Meaning, Exit Code 137 & Fix

SIGKILL is Unix signal 9. A process terminated by it reports exit code 137 (128 + 9).

SIGKILL forcibly terminates a process and cannot be caught, blocked, or ignored. When it kills a process, the shell reports exit code 137 - the 128 + signal-number convention.

What it means

On memory-limited CI runners, SIGKILL is overwhelmingly the out-of-memory killer reclaiming memory.

When it happens in CI

The cgroup out-of-memory killer terminated the heaviest process.
An external watchdog or kill -9.
timeout --signal=KILL fired.

How to handle it

Give the job more memory or reduce peak usage (lower parallelism, cap language heaps). This class self-heals on Latchkey - it is detected and retried with the right resources.

Related guides

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