Large Language Models (LLMs) have become foundational components in modern artificial intelligence applications, enabling advanced capabilities in natural language understanding, automated reasoning, content generation, and enterprise decision support. However, the increasing deployment of LLM-based systems has introduced significant security vulnerabilities, particularly prompt injection attacks that manipulate model behavior by embedding adversarial instructions into user inputs, external data sources, or integrated application workflows. This research presents an adaptive defense framework designed to mitigate prompt injection risks through a layered security architecture combining input analysis, contextual validation, dynamic instruction monitoring, and automated response regulation. The study develops a conceptual model for improving LLM reliability by integrating principles from prompt engineering, cloud execution security, artificial intelligence governance, and adaptive system management. Existing research on generative AI frameworks, cloud orchestration, automated workflows, and secure execution environments provides the foundation for analyzing effective defense mechanisms. The proposed framework emphasizes continuous threat identification, intelligent prompt classification, and adaptive policy enforcement to reduce unauthorized behavioral manipulation of LLM systems. Findings indicate that effective LLM security requires a transition from static filtering approaches toward dynamic defense architectures capable of responding to evolving attack strategies. The research contributes an integrated perspective for improving trustworthy generative AI deployment across financial, cloud, enterprise, and intelligent automation environments.