The growing complexity of cyber-physical attack surfaces in advanced manufacturing has made cyber threat intelligence analysis increasingly difficult. Although large language models and retrieval-augmented generation have improved CTI workflows, text-based approaches remain vulnerable to hallucinations and provide limited support for structured reasoning over interconnected threats. Graph-based RAG reduces some of these limitations, but existing approaches often lack ontology-consistent multi-hop reasoning and transparent evidence tracing across heterogeneous cybersecurity data. This paper proposes a graph-grounded neuro-symbolic framework that integrates ontology-aware symbolic query generation, knowledge graph retrieval, and neural language generation to support accurate and explainable threat analysis across information technology and operational technology environments. The framework adopts a dual-large language model architecture: the first model translates natural-language questions into executable Cypher queries for symbolic graph retrieval, while the second generates answers strictly from the retrieved graph evidence. Experimental evaluation using publicly available cyber threat intelligence benchmarks shows consistent improvements over the published baseline in reasoning accuracy, while also reducing hallucinations, strengthening multi-hop reasoning, and improving robustness to adversarial perturbations. Runtime and explainability analyses further demonstrate that the framework maintains interactive inference performance and exposes graph-grounded reasoning artifacts that allow analysts to inspect and verify each stage of the analysis. Overall, the results highlight the potential of graph-grounded neuro-symbolic reasoning as a scalable, interpretable, and reliable approach to cyber threat intelligence for next-generation Industry 5.0 environments.

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