What exactly do you pin to make an ML training run bit-for-bit reproducible?

'Just set a seed' is the wrong answer. Reproducibility means pinning the environment, the data, the code, and the hardware-level nondeterminism, all at once. Here is the full checklist and where it leaks.

Updated Aug 2026 · Grounded in real Applied AI Engineer interview loops and written to a senior-engineer editorial bar.