# Cua — Inside macOS window internals: how SkyLight enables multi-cursor background agents

- Company: Cua (cua.ai)
- Announced: 2026-04-23
- Category: not stated
- Coverage: not counted
- Announcement: no
- Group: routine
- Source: https://cua.ai/blog/inside-macos-window-internals
- Record: https://forck.live/items/16822-inside-macos-window-internals-how-skylight-enables-multi-cursor-background
- Subject: Cua Driver / Lume / Cua Bench / Cua Fleets

Published on April 23, 2026 by Francesco Bonacci TL;DR: cua-driver is an open-source macOS driver that lets any agent (Claude Code, Codex, your own harness) drive any Mac app in the background. The user's cursor doesn't move, focus doesn't change, and macOS doesn't drag them across Spaces - this is called background computer-use . Built on SkyLight's SLEventPostToPid , a private AX SPI for sparse accessibility trees, and yabai's focus-without-raise pattern. Source: github.com/trycua/cua . Following OpenAI's Codex Computer-Use announcement and the great work of the Sky team, we've been down a rabbit hole reverse-engineering macOS window management internals. I want to tell you what we found, and where I think we're headed next. Let me back up. Since 2024 I've watched a lot of GUI agents-based products ship and fail, mostly because of the embedded nature of desktop inputs being synchronous: one cursor and one keyboard for one focused window. …

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Record: https://forck.live/items/16822-inside-macos-window-internals-how-skylight-enables-multi-cursor-background
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