Why does the Codex sandbox stop execution early even when my script is within time limits?

[O1Legend]

When running Python scripts in the Codex sandbox, I sometimes see “Execution stopped” even though the script should easily finish under 3 seconds. The script mainly performs NumPy operations.

I’ve confirmed that:

• No infinite loops
• No excessive recursion
• No huge I/O
• No sleeps or waiting

Why does the sandbox kill execution early, and is there a recommended workaround?

[abhishekprajapatt]

The sandbox enforces additional safety rules beyond execution time:

• Memory limits (often < 256–512 MB)
• Process output limits
• Hidden per-operation timeout for CPU-bound loops
• Protection against runaway NumPy broadcasting

Large NumPy operations can trigger a “soft timeout,” even within total time limits.

Workarounds:

• Break large ops into smaller batches
• Avoid giant temporary arrays
• Prefer vectorized operations over Python loops
• Disable debug prints (stdout flood triggers soft-kill)