@misc{Armstrong2026sift,
  author = {Armstrong, Joss},
  title = {Source Identification Is Not Fitness Testing: Measuring the Limits of Synthetic-Data Attribution},
  year = {2026},
  eprint = {2610.00417},
  archivePrefix = {arXiv},
  primaryClass = {cs.LG},
  doi = {10.48550/arXiv.2610.00417},
  url = {https://arxiv.org/abs/2610.00417},
  note = {Version 1, submitted 2026-09-30}
}