  This volume contains
  * The post-proceedings of the Eighteenth Logical and Semantic Frameworks with
Applications (LSFA 2023). The meeting was held on July 1-2, 2023, organised by
the Sapienza Universit\`a di Roma, Italy. LSFA aims to bring researchers and
students interested in theoretical and practical aspects of logical and
semantic frameworks and their applications. The covered topics include proof
theory, type theory and rewriting theory, specification and deduction
languages, and formal semantics of languages and systems.
  * The post-proceedings of the Tenth Workshop on Horn clauses for Verification
and Synthesis (HCVS 2023). The meeting was held on April 23, 2023 at the
Institut Henri Poincar\'e in Paris. HCVS aims to bring together researchers
working in the two communities of constraint/ logic programming (e.g., ICLP and
CP), program verification (e.g., CAV, TACAS, and VMCAI), and automated
deduction (e.g., CADE, IJCAR), on the topics of Horn clause based analysis,
verification, and synthesis.
