DeepSeek open-sources a Claude Code rival

DeepSeek released Harness on August 13, the same day it took V4-Pro to general availability, an MIT-licensed agent runtime built to run its V4 model family as autonomous coding agents that can plan multi-step work and call tools on their own. The repository picked up over 100,000 GitHub stars within days of release. It’s built around an “everything is a plugin” architecture: models, tools, skills, sessions, sandboxes, filesystems, and even the orchestration loop and UI are each implemented as swappable plugins rather than fixed parts of the framework.

The obvious point of comparison is Anthropic’s Claude Code, the tool developers have made their default for letting an agent browse a codebase and run terminal commands unsupervised, and DeepSeek is clearly building toward that same job. The project is a Node.js codebase currently labeled a developer preview, meaning DeepSeek is still iterating on the interface and warns of compatibility-breaking changes ahead.

What it means for you

An MIT license means you can fork, modify, and ship Harness commercially without asking DeepSeek, which matters if you’ve been locked into a single vendor’s agentic coding tool and want an open alternative to build on. But “developer preview” is doing real work in that description: the plugin interfaces are still moving, so treat this as something to prototype against, not something to depend on in production yet. It lands in the same week Cognition’s Devin business reportedly hit a $1B revenue run rate, coding agents, open and closed, are the category everyone in AI is racing to own right now.