DeepSeek has introduced Harness v0.1, an open-source development environment for AI agents, and released the final version of its V4 Pro model.
Harness is designed as an open alternative to Claude Code. The framework is distributed under the MIT license and is available in a preliminary iteration for developers on GitHub. It operates as a layer on top of a LLM, providing the agent with tools to work with codebases, terminals, and external tools.
Simultaneously, the company released the final version of DeepSeek V4 Pro, enhancing its agent capabilities and adding support for the OpenAI Responses API.
Open Competitor to Claude Code
Harness is aimed at scenarios where the model not only generates code on demand but also autonomously performs a sequence of actions in a working environment.
DeepSeek positions it as a minimalist agent framework that can be used with proprietary models and customized for specific tasks.
According to the company, Harness was used to test the agent capabilities of V4 Pro on several public benchmarks.
DeepSeek is focusing not only on the framework itself but also on the combination of the model and the agent shell: Harness is intended to help V4 Pro use tools more effectively and perform long sequences of actions.
V4 Pro Gains New Agent Capabilities
The final V4 Pro is available in the app, web version, and API. DeepSeek reports a significant increase in performance for agent tasks. The model now has native support for the Responses API and integration with Codex, with reasoning levels selectable from three modes—low, high, and max.
In tests published by the company, V4 Pro scored 87.9 in Terminal Bench 2.1, 62.7 in DeepSWE, and 74.1 in Toolathlon-Verified.
API Pricing to Increase
With the full release, DeepSeek is changing its pricing model. The company is introducing a dynamic model with peak and off-peak hours, offering prices reduced by half during off-peak times.
So basically a 2x price increase
Still absurdly cheap for what you’re getting though. pic.twitter.com/N6qt4HLpAn
— red 📌 (@redkendl) August 13, 2026
The new rates will take effect on August 16.
Earlier, it was reported that DeepSeek formed a team to develop Harness in May.
