--extra-index-url only ADDS an index; pip then picks the highest version across
all of them, and PyPI's default torch is built for CUDA 13. So the pin never
applied: every capability image shipped a CUDA-13 torch and failed on any
machine with an older driver — 'The NVIDIA driver on your system is too old
(found version 12080)'. RunPod's fleet is mixed, so the same GPU model passed or
failed depending on which machine the pod landed on, which is exactly why this
looked like flakiness for so long.

torch, torchvision and torchaudio now install from the CUDA index alone, via
--index-url, before anything else; installed later from PyPI they would pull a
matching CUDA-13 torch back in. cu128 resolves to torch 2.11 — the version the
local install already runs — and runs on the driver that failed.

Both Dockerfiles print the resolved torch build at each layer, so a silent
substitution cannot happen again.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0182DhR1eFNPQyGmDrpHbedY