DeepSeek-V4.1-Flash-1017 vs. DeepSeek-V3.1-Terminus

DeepSeek-V4.1-Flash-1017 is an open-weight artificial intelligence model developed by DeepSeek for multimodal understanding, advanced reasoning, autonomous agent workflows, and software engineering. Introduced on October 17, 2026, the release updates DeepSeek-V4.1-Flash with improvements in reasoning accuracy, coding capabilities, agent performance, and computational efficiency. The model builds on DeepSeek's mixture-of-experts architecture and supports native visual understanding alongside natural language processing. Its one-million-token context window enables applications to process extensive documents, large code repositories, and long sequences of interactions. Developers can configure reasoning effort and use the model for tasks involving mathematical reasoning, programming, information analysis, and complex problem-solving. Software engineering capabilities include code generation, debugging, repository analysis, automated testing, and implementation of features across existing projects. DeepSeek also trained the model using reinforcement learning with self-feedback to improve its ability to create complete projects, including web applications, interactive games, and 3D environments. Its agentic capabilities support multi-turn conversations, external tool calling, task planning, and integration with automated development environments. DeepSeek reports improvements over the previous version on benchmarks including Terminal-Bench, DeepSWE, ProgramBench, Automation-Bench, and Agents' Last Exam. The model includes reference prompt encoding tools and supports deployment through Hugging Face Transformers, vLLM, SGLang, and compatible inference infrastructure. DeepSeek-V4.1-Flash-1017 is available through the DeepSeek API under the deepseek-flash model identifier and through downloadable model weights licensed under the MIT License.

DeepSeek has introduced DeepSeek-V3.1-Terminus, an enhanced version of the V3.1 architecture that incorporates user feedback to improve output reliability, uniformity, and overall performance of the agent. This upgrade notably reduces the frequency of mixed Chinese and English text as well as unintended anomalies, resulting in a more polished and cohesive language generation experience. Furthermore, the update overhauls both the code agent and search agent subsystems, yielding better and more consistent performance across a range of benchmarks. DeepSeek-V3.1-Terminus is released as an open-source model, with its weights made available on Hugging Face, thereby facilitating easier access for the community to utilize its functionalities. The model's architecture stays consistent with that of DeepSeek-V3, ensuring compatibility with existing deployment strategies, while updated inference demonstrations are provided for users to investigate its capabilities. Impressively, the model functions at a massive scale of 685 billion parameters and accommodates various tensor formats, such as FP8, BF16, and F32, which enhances its adaptability in diverse environments. This versatility empowers developers to select the most appropriate format tailored to their specific requirements and resource limitations, thereby optimizing performance in their respective applications.