It's probably easier to look at the source code than try to decompile it: https://github.com/anthropics/claude-code

You'll get blocked real quick. I once noticed it was thinking in a different language than the one we were communicating in, when I asked about it the conversation was immediately blocked.

For Codex there is no need to decompile because unlike Claude Code, Codex is open source [1] and written in Rust.

There are lot of other amazing open source agent harnesses like OpenCode [2] and Pi [3].

[1] https://github.com/openai/codex

[2] https://github.com/anomalyco/opencode

[3] https://github.com/earendil-works/pi