How to use Claude to build a compiler and OS
Using Claude Code, the author built an xc compiler, extended FreeRTOS into XTOS and integrated an Atari emulator. They report a Linux-built signed iPhone binary, fast OS startup and a passing Acid 800 emulation test.
news.ycombinator.com
Prompt to try
Editorial adaptation, not the source author’s exact prompt. Replace bracketed inputs and review tool permissions first.
Help develop [systems project] with [language and platform requirements]. Begin with [compiler foundation], extend [OS base] with [required services], then integrate [emulator] and validate it with [conformance suite]. Track working capabilities separately from planned features and provide evidence for each result.
Reach people exploring AI agents
See placements →What happened
The author reports a cross-platform compiler, an XTOS desktop booting in a couple of seconds and an integrated Atari emulator that passes Acid 800.
Reported by spacedcowboy on Hacker NewsHow the agent did it
- Built the xc compiler for multiple host and target platforms.
- Extended FreeRTOS into XTOS with processes, linking, networking and a graphical desktop.
- Built an Atari emulator and integrated it into XTOS for launching games.
Where a person stepped in
The post reports an Acid 800 emulator test and working binaries, but does not describe a code review process.
A person approved each step before the agent continued.
The author attributes a collection of projects built over about six months to Claude Code. The foundation is xc, a language similar to Objective-C, with a compiler that runs on Windows, Mac, Linux and Zynq and produces code for additional targets including WASM, iOS and older processors. The author reports a signed iPhone binary written and signed entirely on Linux.
They also describe building a cross-platform UI framework, with a visual interface-building application identified as a next step. For XTOS, they started with FreeRTOS and added loadable processes, dynamic linking, shared memory, paging, networking and a GEM-based graphical interface. The resulting system runs on a Z-turn board and reportedly reaches its desktop in a couple of seconds.
An Atari emulator was integrated into XTOS so desktop icons can launch games. The author says it passes the Acid 800 emulation torture test and runs named games. Other work includes an xc-based website and a circuit editor and simulator. These are reported capabilities rather than independently verified results, and the post gives no detailed agent prompts or review process. Who it's for: experienced systems programmers exploring agent-assisted development across compilers, operating systems and emulation.
Prompt
Suggested prompt (written by Agents In Use, not the author's)
Source: Hacker News · spacedcowboy
Frequently asked questions
What did the compiler support?
The author says xc runs on Windows, Mac, Linux and Zynq and can target those platforms plus WASM, iOS, Android, m68k and 6502.
What testing was reported for the emulator?
The author says the Atari emulator passes the Acid 800 emulation torture test and can run Ballblazer, Elektraglide and Despatch Rider.
More details
About this account
The author attributes the listed implementation projects to Claude Code, without detailing how individual coding sessions were delegated.
Platform: Hacker News. Attribution: https://news.ycombinator.com/item?id=49775766. Prompt: Suggested (written by Agents In Use, not the author's). Sourced by the Agents In Use pipeline.
Credit: spacedcowboy on Hacker News
Source published 20 Sept 2026
Source checked 14 Oct 2026
Tools and topics
Claude Code · xc · FreeRTOS · XTOS · Acid 800
compilers · operating systems · emulation
Editorial completeness: 100/100. Measures documented fields, not agent performance or verified outcomes.