Codex reimplemented in 8k lines of C++, <1MB binary

Paolo Anzini released MicroCodex, an ultra-lightweight coding agent written in C++23 that runs locally in the terminal, with a binary under 1MB and the codebase comprising 8,000 lines. The tool supports one-shot prompts, an interactive terminal UI, local coding tools, durable conversations, and automatic context compaction, and is available for macOS and Linux via GitHub releases or an install script. MicroCodex is not sandboxed, so model-requested commands run with the user's permissions, and it currently lacks MCP support and safe-command gating.

MicroCodex is an ultra-lightweight coding agent that runs locally in your terminal. MicroCodex is written in C++23 and provides one-shot prompts, an interactive terminal UI, local coding tools, durable conversations, and automatic context compaction. Run the following on Mac or Linux to install MicroCodex: curl -fsSL https://github.com/paoloanzn/microcodex/releases/latest/download/install.sh | sh Then simply run microcodex login to sign in, followed by microcodex to get started. You can also go to the latest GitHub Release https://github.com/paoloanzn/microcodex/releases/latest and download the appropriate binary for your platform. Each GitHub Release contains these executables: - macOS - Apple Silicon/arm64: microcodex-aarch64-apple-darwin.tar.gz - x86 64: microcodex-x86 64-apple-darwin.tar.gz - Apple Silicon/arm64: - Linux - x86 64: microcodex-x86 64-unknown-linux-gnu.tar.gz - arm64: microcodex-aarch64-unknown-linux-gnu.tar.gz - x86 64: Each archive contains a single entry with the platform baked into the name for example, microcodex-aarch64-apple-darwin , so you likely want to rename it to microcodex after extracting it. The installer selects the native build for the current architecture. Linux requires the libcurl and OpenSSL runtime libraries. To install a specific release, set MICROCODEX RELEASE : curl -fsSL https://github.com/paoloanzn/microcodex/releases/latest/download/install.sh | MICROCODEX RELEASE=v0.1.0 sh Run microcodex login and open the displayed URL in your browser. MicroCodex stores the resulting OAuth credentials under $CODEX HOME , or ~/.codex when CODEX HOME is unset. You can then start an interactive session or pass a one-shot prompt: microcodex microcodex "Find the failing test, fix it, and run the relevant test suite" Warning MicroCodex is not a sandbox. Model-requested commands and file operations run with the same permissions as the MicroCodex process. MicroCodex discovers the same filesystem skills installed for Codex under $CODEX HOME/skills , or ~/.codex/skills when CODEX HOME is unset. Each skill must have a SKILL.md with YAML frontmatter containing a name and description . Skill metadata is added to the agent instructions at session startup; the complete skill is read only when its name or description matches the task. Building requires a C++23 compiler, make , libcurl development files, and OpenSSL development files on Linux. git clone --recurse-submodules https://github.com/paoloanzn/microcodex.git cd microcodex make The executable is written to build/microcodex . Run the test suite with make test . - MCP support is not implemented yet. - Text cannot currently be copied from the terminal while using MicroCodex. - Dangerous shell commands are not yet gated by a safe-command policy. This repository is licensed under the Apache-2.0 License /paoloanzn/microcodex/blob/main/LICENSE .