Selective state space modeling is a deep learning sequence modeling framework that dynamically adapts the parameters of a state space model based on the input data, allowing the system to selectively propagate, compress, or filter information across sequential steps. Unlike traditional linear time-invariant state space models that apply fixed transition dynamics regardless of content, selective models make state transitions and projection matrices input-dependent, enabling content-based reasoning. This architecture provides the selective context-tracking capabilities of self-attention mechanisms while preserving the linear computational complexity and constant-memory inference characteristic of recurrent and state space formulations.