We generalize an efficient automata-based approach to string constraint solving, the stabilization-based method behind the solver Z3-Noodler, to support relational constraints represented by finite-state transducers (useful, for example, for modeling replaceAll constraints). We focus on an efficient treatment of length constraints by reducing the need for expensive concatenation elimination, which is a major bottleneck in automata-based string solving. We also propose powerful heuristics that significantly improve performance in practice. Implemented on top of Z3-Noodler, our method vastly outperforms existing solvers on benchmarks with relational constraints. It solves more instances and runs orders of magnitude faster.
@article{arxiv.2605.14872,
title = {String Solving with Stabilization and Transducers (Technical Report)},
author = {David Chocholatý and Vojtěch Havlena and Lukáš Holík and Juraj Síč and Michal Šedý},
journal= {arXiv preprint arXiv:2605.14872},
year = {2026}
}