We've been running Cursor Ultra ($200/month) in Auto Mode for extended sessions — sometimes 8+ hours of autonomous development. This repository is the result: 170k+ lines of Zig, a complete RISC-V64 operating system.

*The Cursor Ultra Experience:*

Auto Mode changes everything. Instead of prompting line-by-line, we describe high-level goals: - "Fix all compilation errors in the JIT compiler" - "Add TCP socket support with proper error handling" - "Refactor this function to be under 64 lines"

The AI then works autonomously: reading files, understanding context, making coordinated changes across the codebase, writing tests, updating documentation. It's pair programming where your partner has read every file and never gets tired.

*What makes the code different:*

1. *AI-friendly style guide* – We created "Grain Style" specifically for AI-assisted development: - 64-line function maximum (2^6) - 128-character line maximum (2^7) - No recursion - 2+ assertions per function - Explicit types (u32/u64 never usize) - Every comment explains "why"

   The AI follows these rules more consistently than humans would. 48 of 56 kernel files are fully compliant.

2. *Pure Zig* – No C dependencies except libc for host tools. Zig's comptime features let us do things that would require macros or code generation in C.

3. *JIT Compiler* – Working x86_64 JIT that translates RISC-V instructions to native code. Near-native speed on x86 hosts.

4. *249 Tests* – Essential for AI-written code. The AI writes the tests too.

*Technical highlights:*

- Kernel boots on QEMU RISC-V64 with virt machine - 60+ syscalls (process, memory, IPC, network, audio, filesystem) - TCP/UDP networking with socket abstraction - Grainscript: a minimal scripting language with lexer, parser, interpreter - Process scheduler with priority queues - ELF loader supporting RISC-V64 binaries - Framebuffer graphics with dirty region tracking

*The economics:*

$200/month for Cursor Ultra. This codebase would have taken a small team several months at $15-20k+ in developer costs. We built it in weeks.

The catch: you still need to know what you're building. AI amplifies capability, it doesn't replace vision.

*Roadmap to Alpha:*

Bottleneck: Basin kernel → Vantage VM → Framework x86_64. Target application: *first-responder dispatch software*.

Contributors needed for ARM aarch64 (Apple Silicon) — Zig → C → Swift macOS app. Also designing Aurora (open-source iOS Cursor alternative) with two inference backends: - [Cursor CLI Ultra](https://cursor.com) ($200/month) - [Cerebras WSE](https://cerebras.ai) — spatial RAM, single-threaded bounded compute, deterministic latency

*Current status:*

Kernel boots, REPL works, Grainscript executes.

Built with Zig 0.15.2. Follows [Grain Style](docs/grain_style.md). MIT/Apache-2.0/BSD-3-Clause licensed.

Submissions

Show HN: Teamlibra/ry: a Zig framework for Cursor that makes prompting better