DeepSeek releases DeepSeek-V4.1-Flash-1017 with MIT-licensed open weights

DeepSeek announced DeepSeek-V4.1-Flash-1017 on X at 14:05 IST on 17 October 2026, as a minor update to DeepSeek-V4.1-Flash, which came out on 10 September. It is live on DeepSeek’s website, app and API, and its weights are on Hugging Face and ModelScope under the MIT licence, which allows commercial use, modification and redistribution.

DeepSeek says it trained the update to build complete projects by learning from feedback on its own attempts, and its examples include a 3D model of the Forbidden City and a Portal 2 recreation in the Godot engine. In DeepSeek’s own table, it leads four of eleven tests, including DeepSWE v1.1 for software engineering, while Claude Opus 5 leads six.

DeepSeek’s cost chart for DeepSWE v1.1 shows it scoring highest at one of the lowest costs per task.

The checkpoint has 763B parameters on Hugging Face, the same as DeepSeek-V4.1-Flash, whose model card describes a mixture-of-experts design, which uses only part of the network for each token: 16B parameters when generating.

In the API

Developers call it as deepseek-flash. The older names deepseek-v4-flash and deepseek-v4-flash-vision-exp still work, but their models are retired and their requests now go to the new model, billed at the Flash price. It offers thinking and non-thinking modes, tool calls and image input. DeepSeek optimised it for DeepSeek Harness, Tencent CodeBuddy and WorkBuddy, and recommends DeepSeek Harness v0.2.1-rc.1 or later.

Key numbers

• Input: $0.15 per million tokens off-peak and $0.30 at peak, or $0.003 and $0.006 for cached input
• Output: $0.60 per million tokens off-peak and $1.20 at peak
• Context: 1M tokens, with up to 384k tokens of output
• Search and Fetch: $0.75 per 1,000 calls each

Peak hours are 06:30 to 09:30 and 11:30 to 15:30 IST on weekdays, outside Chinese public holidays. DeepSeek also opened to everyone its Search API, which finds web pages with its own search engine, and its Fetch API, which returns a page as Markdown. Search and Fetch calls through server-side tools in DeepSeek Harness, Claude Code and Codex stay free for DeepSeek API users until 21:30 IST on 31 October 2026.