Agentic AI for Inter-Operator Composability explores how communications service providers can dynamically coordinate and share network resources, infrastructure, and operational capabilities across organisational boundaries. Building on the foundations established through the OmniBOSS Catalyst programme, the project addresses emerging industry needs for secure, standards-based collaboration between operators in scenarios such as capacity sharing, network resilience, emergency response, and security incident management. As networks become increasingly distributed and complex, traditional approaches to coordination are no longer sufficient to deliver the speed, agility, and efficiency required. The Catalyst introduces an innovative agentic AI framework designed to enable intelligent inter-operator composability. By combining AI-driven decision-making with TM Forum standards, trust frameworks, and reusable industry assets, the solution aims to automate and optimise how operators interact, exchange information, and orchestrate services across their networks. This represents a significant step forward for the industry, moving beyond manual coordination processes towards autonomous, trusted collaboration at scale. From a business perspective, the project has the potential to unlock substantial operational and commercial value. Dynamic resource sharing can improve infrastructure utilisation, reduce unnecessary network build costs, and enable faster service restoration during outages or high-demand events. By allowing operators to collaborate more effectively, the solution supports improved customer experiences, greater network resilience, and more efficient capital investment strategies as the industry prepares for next-generation network evolution, including 6G. Success will be measured by demonstrating real-world production feasibility and quantifiable operational improvements. Key indicators include reduced time to restoration, faster fault repair, and enhanced network build-out efficiency. By proving that AI-enabled inter-operator composability can be implemented in a trusted and scalable way, the Catalyst will provide a foundation for future industry adoption and help accelerate the transformation towards more intelligent, collaborative telecommunications ecosystems.