smolagents timeout defeated by single big-int expression holding the GIL

Short summary

A single LLM-generated expression like 10 ** 10 ** 8 can permanently freeze a smolagents sandbox because CPython's big-int exponentiation holds the GIL in one uninterruptible C call, preventing the thread-based timeout from ever firing. The author built an external watchdog process that kills frozen workers and reports to Sentry, where Seer's root-cause analysis independently confirmed the GIL issue. The fix requires predicting expensive operations before execution since mid-flight interruption is impossible from Python.

• •10 ** 10 ** 8 holds the GIL in a single C call, defeating smolagents' thread-based timeout entirely
• •An external watchdog process is needed for freeze-class bugs since the SDK can't flush events mid-freeze
• •Sentry's Seer independently confirmed the root cause: signal-based interruption cannot fire during uninterruptible C-level operations

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