FastWAM upstream, SBInt openarm 873-ep dataset, deltaq arm: chunk-wise masked delta (same as delta arm) + q01/q99 quantile normalization to [-1,1] (GWP-0.5-aligned), stats computed post-transform in delta domain. 50k A/B run, step-10000 weights ckpt.

Files: step_010000.pt, config.yaml, dataset_stats.json. Inference: normalizer.backward then MaskedDeltaJointTransform.backward with window first-frame raw state.

Upstream repo: https://github.com/zhujohn9604/FastWAM — see handoff/SBINT_AB_DELTA.md (design) and handoff/ENV_SETUP.md (reproduction).