Andrew Cordivari

Learning & Projects

Personal projects I've worked on over the last few years.

Things I've built

Most recent

x401 + x402 — Open Source Identity-backed Agentic Payments

Two open-source protocols that let AI agents safely act on a person’s behalf — first proving who they are, then paying within limits that person set. x401 handles the proof: before granting access, a service can require an agent to verify something real about itself (personhood, residency, membership). x402 handles the money: the agent pays with USDC, settled on-chain. A mandate layer ties it together, enforcing which human approved the spend and how much. First live on-chain payment landed June 2026.

  • TypeScript
  • x401
  • x402 v2
  • W3C Digital Credentials API
  • OpenID4VP
  • OAuth 2.0
  • Coinbase CDP Wallet
  • viem
  • EIP-3009
  • Base Sepolia
  • USDC
  • Zod
Source → Read the x401 spec
Recent work

Ling — Reading a Whale-Song Model

Project CETI has trained a neural network on the patterned clicks sperm whales use to address one another — a machine that has read a great deal of whale data and can imitate it convincingly. These clicks can register over 230 decibels. A fighter jet at takeoff usually peaks around 150db. There are a few great documentarys on Youtube if you are curious to learn more. This project probes the model to explore if has it learned the grammar, or only the accent? The method is comparative — compare whale codas beside human click languages, drum rhythms, and other animal sounds, then note which resemblances hold and which the model has invented. This a browser tool that runs entirely on a local machine, no weights and no network, measuring rhythm and timbre in the open beside a glossary of 75 terms each defined twice, once formally and once for the uninitiated. I do have the weights downloaded on my computer for other testing purposes and these are available from Hugging Face. Controls and predictions are written down before every run, on the sound suspicion that any ordering of distances can be rationalised after the fact — and null results are recorded as results.

  • Vanilla JS
  • Web Audio API
  • DSP
  • DTW
  • Python 3.9
  • VampNet
  • madmom
  • ffmpeg
Source →
Recent work

Fender '67 Tube Amp Emulator

A C++ Audio Unit plugin that models a late 60s-era Fender tube amplifier circa 1967 — I am trying to make a DAW plugin (currently testing this in Garage Band) that sounds better than the stock plug ins. ‘Better’ meaning, it hits that ‘if you know you know’ midrange that a good bluesy solo conveys so well through the right instruments. The sound parameters are calculated mathematically based on some of the original formulas published in the 60s, 70s, and 80s.

  • C++
  • JUCE
  • CMake
  • Audio Unit
  • macOS
  • DSP
  • Convolution
Source →
Recent work

Sound Design Lab

A hands-on learning tool for live sound engineers. Place real speakers and amplifiers around a Denver venue and get instant feedback on whether the setup is safe and sound — flagging mismatched power or wiring, predicting how the sound covers the room, and letting you hear what a fault would sound like. Guided missions grade your work as you go.

  • FastAPI
  • SQLAlchemy
  • React 18
  • Vite
  • Zustand
  • Tailwind
  • Web Audio API
View live → Source
Earlier work

Tatu Artists Around the World

A searchable directory of blackwork tattoo artists from around the world — rebuilt from the ground up off an old 2016 project. It pulls artists automatically from Instagram, stores their work directly rather than hotlinking it, and figures out where each artist is based by reading their bio and cross-checking real shop locations. You can search, filter by country and region, and see everyone on an interactive map. Around 1,650 artists indexed so far.

  • Rails 8
  • Ruby 3.3
  • PostgreSQL
  • Active Storage
  • React 19
  • TypeScript
  • Vite
  • React Query
  • MapLibre GL
  • Apify
View live → Source

IP Tracker

A dependency-free rewrite of an old AngularJS app — looks up your public IP and renders its geolocation (city, region, coordinates, ISP) client-side, with a fallback between providers for reliability.

  • Vanilla JS
  • Vite
  • Geolocation API
  • GitHub Actions

Freelance CRM

A rewrite of a 2017 Angular 2 + Rails-microservices app — lets freelance designers draft, organize, and email client proposals from a live-updating dashboard, now on Angular 20 standalone components talking JSON to a single Rails 8 API.

  • Angular 20
  • TypeScript
  • Rails 8 API
  • PostgreSQL
  • Bootstrap 5

UTravel

A ground-up rewrite of an old Rails 5 app — members write travel journals about cities and discuss them in comments, rebuilt as a server-rendered Hotwire monolith with Active Storage image uploads and server-side authorization.

  • Rails 8
  • Ruby 3.3
  • Hotwire
  • Tailwind CSS
  • PostgreSQL

Learning