DeepSeek V3.1 is positioned as the family’s first step into the agent era, built around a hybrid inference design that lets a single model switch between a deliberate thinking mode and a faster non-thinking mode. Rather than forcing users to pick a separate chat or reasoner model, the DeepThink toggle exposes both behaviors behind one interface, with the thinking variant aimed at producing answers in less time than the earlier R1-0528 release. The same dual-mode design is mirrored in the API surface, where one endpoint handles plain chat and another handles explicit reasoning, both sharing a 128K context window and an Anthropic-compatible calling format. The base architecture underlying this release is a 671B-parameter Mixture-of-Experts model with 37B active parameters per forward pass, trained on 14.8T tokens in FP8 mixed precision to balance scale with training efficiency, and extended with an additional 840B tokens of continued pretraining on top of V3 to lengthen context and tighten the foundation for downstream agent behavior.

Post-training is where V3.1 leans hardest into its agent identity, with targeted improvements to tool calling, strict function calling in beta, and multi-step reasoning for complex search and software tasks. The release notes highlight measurable gains on SWE-bench and Terminal-Bench, plus a clear push toward thinking efficiency so the reasoning mode reaches conclusions faster without losing depth. Public benchmarks reinforce the practical bent: the model posts 49.8% on AIME 2025 and 74.9% on GPQA Diamond, placing it in the same general range as other general-purpose reasoners while keeping an open-weight profile that makes it attractive for self-hosted agent stacks. With deepseek-chat and deepseek-reasoner endpoints, 128K context, JSON-style function calling, and a permissive deployment path, V3.1 is well suited for teams wiring models into coding assistants, retrieval pipelines, and multi-step workflows that need a single engine to flex between quick answers and more careful deliberation.