You can stick with Claude Code if you're already using it. DeepSeek has an Anthropic-compatible endpoint, so you just need to set ANTHROPIC_BASE_URL=https://api.deepseek.com/anthropic and ANTHROPIC_AUTH_TOKEN to your DeepSeek API key.

DeepSeek Harness works very well, also used Codewhale which is not too shabby

Pi is very good with open weight models (proprietary ones too)

Pi if you're a minimalist

OpenCode if you want a good, opinionated setup