Preston Brown

Projects

Main work

  • Peko

    A toolchain for shipping one app to macOS, Windows, Linux, iOS, and Android, built around Pekoscript, a statically typed language I designed and wrote the LLVM compiler for.

    On holdRust / LLVM 18 / C / Objective-C / Java
    DetailsSourcepekoui.com
    Peko Studio, a code editor, showing main.peko and App.tsx open with a Problems panel listing Pekoscript type errors
    Peko Studio, the IDE I built as a Peko app. Pekoscript type errors show up next to TypeScript ones.

  • ProxOS

    A bytecode VM, an assembler for its own assembly language, and the start of a kernel, written in C and C++ without AI.

    In progressC / C++ / CMake
    DetailsSource
    $ prox asm demo.prasm
$ prox vm out.prx
PROX
5 4 3 2 1
42
Hi!
    Assembling and running examples/demo.prasm: a banner, a countdown loop, a subroutine call, and a heap round trip.

Smaller and team projects

  • Kyro

    A JavaScript and TypeScript engine in Rust with a bytecode interpreter and an LLVM ahead-of-time compiler, meant to run inside Peko apps.

    I wrote the architecture and spec. Claude wrote the implementation.

    PostponedRust / LLVM 18
    Source

  • Lark

    A systems language that extends C11 with garbage collection, interfaces, generics, and modules, and compiles to C.

    I designed the language. Most of the implementation was AI-written.

    v0.1.0Rust / C
    Source
    export managed struct Person {
    gc char* name;
    int age;
}

export struct Data<T> {
    T* data_point;
}

export iface Greet {
    void say_hi(Self this);
    // ...
}
    A managed struct, a generic, and an interface, from examples/tour.lark.

  • Collet

    An experiment on whether AI coding agents edit Rust better through structured tools (rust-analyzer, tree-sitter, and cargo behind MCP) than through plain file edits.

    I designed the experiment. Claude wrote most of the code.

    Early resultsRust / Python / MCP
    Arm        Semantic  Text  Shell
C1              26%   57%    17%
C2              33%   50%    17%
C2-forced        6%   65%    30%
    Share of tool calls across 11 runs. Even with semantic tools available, the model mostly read and edited text, and never once called the tool that bundles a symbol’s full context.

  • Peko policy checker

    Checks an iOS or Android project against App Store and Google Play policy. The lint runs locally, from a CLI, a GitHub Action, or a Claude Code plugin.

    Rust
    Source

  • Sidecar

    A Mac app I built for my own customer interviews: tracks hypotheses and evidence, manages outreach, and transcribes calls live.

    Built with AI coding tools.

    Python / Svelte / Tauri
    Source

  • Ritnag

    A desktop companion that listens while you work, recognizes repeated questions, and answers them out loud. Built with a team at Cal Hacks 13.0.

    Much of the code was AI-assisted.

    TypeScript
    Source
    Ritnag's cover: a cartoon red devil next to the line 'You answer once. It handles the next interruption.'

  • Loan processing research

    Interviews with independent mortgage processors in 2026, and a prototype desktop tool for reconciling loan fees across documents, tested only on synthetic data.

    Past researchTypeScript / Electron
    A loan fees table beside a side panel listing approved updates and fields to fill from reviewed documents
    The prototype on a synthetic practice loan.