Reverse-engineered Codex background computer-use API released
Developer anupamb has open-sourced a local macOS computer-use API that replicates OpenAI Codex's background computer-use capability, controlling native apps and browser windows without taking over the user's pointer.
Score breakdown
Developers building agentic coding workflows on macOS can use this open-source runtime to add background computer-use capabilities — equivalent to Codex's plugin — without relying on OpenAI's infrastructure or disrupting the user's active desktop session.
- 01Open-source Swift project that reverse-engineers OpenAI Codex's background computer-use plugin for macOS.
- 02Exposes a loopback HTTP API for controlling native apps, browser windows, and multi-window desktop workflows.
- 03Operates without taking over the user's mouse pointer.
The `background-computer-use` repository, published by anupamb, provides a local macOS runtime that claims rough parity with the OpenAI Codex Computer Use plugin. Rather than a cloud-dependent integration, it runs entirely on-device, exposing a loopback HTTP API that agents can call to control native applications, browser windows, and multi-window desktop workflows — crucially, without taking over the user's mouse pointer.
The runtime is built in Swift and relies on three macOS system capabilities: Accessibility APIs, Screen Recording permissions, and native/private window-event APIs.
The runtime is built in Swift and relies on three macOS system capabilities: Accessibility APIs, Screen Recording permissions, and native/private window-event APIs. It supports a range of actions including clicks, scrolling, text entry, key presses, secondary (right-click) actions, and window motion. Because macOS permissions are tied to signed app bundles rather than arbitrary binaries, the project includes a signing script (`script/bootstrap_signing_identity.sh`) that automatically creates a local development code-signing identity in a dedicated keychain if no signing identity is configured. Agents are directed to read the runtime manifest file for the active base URL rather than assuming a fixed port, with the manifest also surfacing permission status and route summaries.
Key facts
- 01Open-source Swift project that reverse-engineers OpenAI Codex's background computer-use plugin for macOS.
- 02Exposes a loopback HTTP API for controlling native apps, browser windows, and multi-window desktop workflows.
- 03Operates without taking over the user's mouse pointer.
- 04Uses macOS Accessibility, Screen Recording, and native/private window-event APIs.
- 05Startup script builds the Swift package, self-signs an `.app` bundle, and installs it to `~/Applications/BackgroundComputerUse.app`.
- 06Runtime manifest is written to `$TMPDIR/background-computer-use/runtime-manifest.json`; agents should read this file rather than assuming a fixed port.
- 07Self-signing is supported via an auto-generated local development keychain if no signing identity is provided.