hide_gpus() in CUDAWrapper makes get_gpu_count() answer 0 without calling
cudaGetDeviceCount, so every GPU decision in the process (indexer Auto ->
FFTW, preprocessing/spot finding/decode, pre-scan, scaling engine, model
validation, MR) takes the path it takes on a machine without a GPU, and no
CUDA context is created. rugnux reads --no-gpu in main, ahead of the parser,
because set_gpu_blocking_sync() already asks CUDA for the devices. The
banner says 'CPU only (--no-gpu)'. The 'run it on the CPU' advice in the
out-of-GPU-memory messages and in the install docs now names --no-gpu
instead of CUDA_VISIBLE_DEVICES=.
Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>