The deciding difference is operational: DeepSeek Harness can run on infrastructure you control, Codex CLI cannot. If that constraint is real for you, it settles the choice before anything else is considered.
Everything is a plugin — the model adapter, the tool registry, the sandbox and the agent loop itself are all swappable.
Web UI first — `dsh web` serves on 127.0.0.1:3080 rather than taking over the terminal. Built on Cordis. Still a developer preview: DeepSeek warns of compatibility-breaking changes, so pin the version.
OpenAI's terminal coding agent.
| DeepSeek Harness | Codex CLI | |
|---|---|---|
| Licence | Open source | Open source |
| Pricing | open source | paid |
| Self-hostable | Yes | No |
| Languages | TypeScript | Any language |
| Install | npx @deepseek-ai/dsh web | npm install -g @openai/codex |
| Keys required | None | OPENAI_API_KEY |
The deciding difference is operational: DeepSeek Harness can run on infrastructure you control, Codex CLI cannot. If that constraint is real for you, it settles the choice before anything else is considered. DeepSeek Harness: Everything is a plugin — the model adapter, the tool registry, the sandbox and the agent loop itself are all swappable. Codex CLI: OpenAI's terminal coding agent.
DeepSeek Harness can run on your own infrastructure. Codex CLI is a hosted service only.
DeepSeek Harness is open source (open source). Codex CLI is open source (paid).
Every page here answers to Accept: text/markdown and returns the same content at roughly a tenth the tokens. No separate site, no toggle — same URL.
curl -s -H "Accept: text/markdown" https://newagent.build/compare/deepseek-harness-vs-codex-cli