Reactive Agency
Reactive agents operate on a "Condition-Action" basis. When they see stimulus X, they perform action Y. They are extremely fast and efficient but have no internal representation of the past or future. Think of a security agent that blocks an IP address the moment it detects a brute-force attack. It is fast, but it doesn't "know" why it's doing it.
Deliberative Agency
Deliberative agents (like modern LLM agents) use a "Reasoning Model" to decide on actions. They maintain an internal state, plan for the future, and reason about the best path to a goal. They are slower and more computationally expensive but are capable of handling ambiguity and complex goals that reactive agents cannot touch.
Conclusion
The future of agentic AI lies in "Hybrid Architectures"--where reactive modules handle high-speed tactical responses while deliberative modules manage high-level strategy and planning. This provides the best of both worlds: speed and intelligence.