This open access book constitutes the proceedings of the 29th International Conference on Fundamental Approaches to Software Engineering, FASE 2026, which was held as part of the International Joint Conferences on Theory and Practice of Software, ETAPS 2026, in Turin, Italy, during April 11–16, 2026.The 21 full papers and 6 short tool competition papers included in this volume, together with one invited keynote paper, were carefully reviewed and selected from 65 submissions. The papers cover the following topical sections: Software Engineering and AI; Advanced Software Development; Autonomous Systems and Applications; and Competition on Software Testing (Test-Comp 2026).