DeepSeek-V3.1 is positioned as DeepSeek's first step toward an agent-focused era, built as a hybrid inference system that runs the same weights in two modes: a "thinking" mode for deeper multi-step reasoning and a "non-thinking" mode for fast conversational replies. Internally, the V3.1 base was produced through 840B tokens of continued pretraining on top of the V3 lineage to extend long-context behavior, with additional post-training aimed at stronger tool calling and multi-step agent workflows. Compared with the prior DeepSeek-R1-0528 reasoning release, DeepSeek describes V3.1-Think as reaching answers in less time, and highlights gains on SWE and Terminal-Bench style coding/agent evaluations, alongside improved complex search reasoning.
In practical deployment, the model is exposed through DeepSeek's own API under the deepseek-chat and deepseek-reasoner aliases, both served with a 128K context window, Anthropic-format compatibility, and a beta strict function calling mode that suits structured tool pipelines. Through third-party hosts such as SiliconFlow and Together AI, teams can route agent workloads, code assistance, and search-heavy reasoning tasks to either the fast or deliberative mode without swapping models, making it a flexible backbone for applications that mix latency-sensitive chat with step-by-step problem solving.
