@article{anundecidabilityprooffortheplanexistence,
  title = {An Undecidability Proof for the Plan Existence Problem},
  author = {Antonis Achilleos},
  year = {2026},
  eprint = {2604.22736},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2604.22736},
}