I reverse-engineered Claude Code and rebuilt the entire SDK in 4 languages. Single file. Zero dependencies and open-source. Uses your existing Pro/Max subscription.
Why: Claude Code is a 190MB Bun bundle. I wanted to use its capabilities (streaming, tool calling, multi-turn agent loop) inside my own projects without depending on a massive binary or npm. One file I can copy into any repo was the goal.
What I found: The subscription auth protocol requires four things at once — an OAuth token from macOS keychain, specific beta headers, a billing header hidden inside the system prompt, and a browser access header. None of this is publicly documented.
The SDKs:
- Node.js (claude-native.mjs) — 0 deps
- Python (claude-native.py) — 0 deps
- Go (claude-native.go) — 0 deps
- Rust (rust-sdk/) — serde + reqwest
Each one gives you:
- OAuth or API key auth
- Full agent loop with streaming + tool use
- Built-in tools (bash, read, write, glob, grep)
- NDJSON bridge for automation (spawn as subprocess, JSON on stdin/stdout)
- Interactive REPL
- MCP server support
Usage is dead simple: cp claude-native.py your-project/ → python3 claude-native.py -p "explain this code". That's it.
MIT licensed. Feedback and PRs welcome :)
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