A valid unknown content block can own a __proto__ JSON field. Zod object reconstruction silently drops that key when Team events are projected and when checkpoints are admitted, even though the original Session log still contains it. Validate the unknown block tag without reconstructing its decoded JSON fields. Keep the current V4 local validators and the rejection of retired tool-result content. Bump only the Team projection cache stateVersion from 3 to 4 so old lossy checkpoints are rebuilt from the unchanged log; this is not a Session format or schema change. Cover direct and nested opaque JSON fields inside accepted native V4 content, plus public registry restoration from an older lossy checkpoint. Historical tool-result conversion remains owned by the Session migration and is not restored in the Team parser. Update the README and existing Team decision rationale together. Adapted from the Team JSON preservation work in b8f1da92599123e5d5bae6c174f73b5b778f3554 by Tianyi Cui. Co-authored-by: Tianyi Cui <[email protected]>
DeepSeek Harness
English | 中文
DeepSeek Harness (dsh) is an open-source agent harness developed by DeepSeek AI.
It is built on an everything-is-a-plugin architecture and powered by Cordis, whose design is described in A Programming Paradigm for Spatiotemporal Composability.
Documentation: https://deepseek-harness.github.io/deepseek-harness/
Developer preview
DeepSeek Harness is in developer preview and iterating rapidly. THERE WILL BE COMPATIBILITY-BREAKING CHANGES.
Review the safety notice before running the project.
Run
Run from npm
Install Node.js, then run:
npx @deepseek-ai/dsh web
The command starts the Web UI at http://127.0.0.1:3080 by default and opens it in the default browser for a local launch. An SSH launch only prints the host URL because the SSH client or editor owns the local forwarded address. Pass --no-open to run the server without opening a browser. See Web UI guide.
Run from source
To run from a repository checkout:
git clone https://github.com/deepseek-ai/deepseek-harness.git
cd deepseek-harness
pnpm install
pnpm run build
pnpm dsh web
pnpm run build prepares the repository artifacts. pnpm dsh web uses those built artifacts without rebuilding.
Community and support
- Submit feedback or bug reports through GitHub Discussions.
- Add the
dsh-plugintopic to your plugin repository for discoverability. - Join DeepSeek Harness Discord community.
Contributing
See CONTRIBUTING.md.
Development
Start with the development guide and architecture documentation.
For agents, follow AGENTS.md.
Citation
@misc{deepseek-harness2026,
title={DeepSeek Harness: Everything is a Plugin},
author={DeepSeek-AI},
year={2026},
publisher={GitHub},
howpublished={\url{https://github.com/deepseek-ai/deepseek-harness}},
}
License
Third-party dependencies and their licenses are disclosed in THIRD_PARTY_NOTICES.md.