Open Codex – OpenAI Codex CLI with open-source LLMs
Hey HN, I’ve built Open Codex, a fully local, open-source alternative to OpenAI’s Codex CLI. My initial plan was to fork their project and extend it. I even started doing that. But it turned out their code has several leaky abstractions, which made it hard to override core behavior cleanly. Shortly after, OpenAI introduced breaking changes. Maintaining my customizations on top became increasingly difficult. So I rewrote the whole thing from scratch using Python. My version is designed to support local LLMs. Right now, it only works with phi-4-mini (GGUF) via…
In plain words
Open Codex is a command-line tool that runs locally on users' computers as an open-source alternative to OpenAI's Codex. Built in Python, it uses open-source language models like phi-4-mini to assist with code generation without requiring cloud connectivity or external services. The tool is designed for developers who want code assistance capabilities running entirely on their own hardware, with plans to expand model support and add interactive chat mode and function calling features.
written from the facts on this page · September 2026
From the sources
In the maker’s words, at launch
Hey HN, I’ve built Open Codex, a fully local, open-source alternative to OpenAI’s Codex CLI. My initial plan was to fork their project and extend it. I even started doing that. But it turned out their code has several leaky abstractions, which made it hard to override core behavior cleanly. Shortly after, OpenAI introduced breaking changes. Maintaining my customizations on top became increasingly difficult. So I rewrote the whole thing from scratch using Python. My version is designed to support local LLMs. Right now, it only works with phi-4-mini (GGUF) via lmstudio-community/Phi-4-mini-instruct-GGUF, but I plan to support more models. Everything is structured to be extendable. At the moment I only support single-shot mode, but I intend to add interactive (chat mode), function calling, and more. You can install it using Homebrew: brew tap codingmoh/open-codex brew install open-codex It's also published on PyPI: pip install open-codex Source: https://github.com/codingmoh/open-codex
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