Today’s paper introduces Step 3.5 Flash, a large language model designed to bridge the gap between high-level reasoning capabilities and the computational efficiency required for real-world applications. While open-source models have improved significantly, they often struggle to match closed-source systems in complex agentic tasks or become too slow and costly when processing long contexts. This paper addresses these challenges by proposing a model that achieves frontier-level intelligence while maintaining low latency, making it particularly suitable for deploying sophisticated AI agents.