agent-42: a coding agent in one while loop
The moment I understood agents: the intelligence is in the model, not in the framework. ~70 lines of logic, deliberately exposed.
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btkick: when Bluetooth won't connect, escalate until it does
A Rust CLI + TUI for Linux/BlueZ that automates the whole 'power cycle, re-pair, yank the dongle' dance — down to rebinding the USB device in sysfs.
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ccr: building a Claude coding agent from scratch in Rust
Hand-written SSE client, seven typed tools, a 900-line markdown renderer, and a typestate render pipeline the compiler enforces — 171 tests, 8.2k lines.
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cobogo: the Clay layout algorithm, made Rust-idiomatic
Zero-dependency core, structure-of-arrays internals, a closure-based API — the third chapter of reimplementing the same layout engine across languages.
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Contributing upstream: 12 PRs in NestJS core, 370 tests into sped-nfe
The proof that's hardest to fake — code accepted by the maintainers of projects thousands of teams depend on.
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FinOpenPOS: an open-source POS that speaks Brazilian tax law
81 stars, 54 forks, and a full NF-e/NFC-e fiscal module — the project where my fiscal work was born, running on Next.js 16 with embedded Postgres.
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fiscal-rs: porting Brazil's most-used fiscal library to Rust — and becoming its maintainer
1,834 tests, 11 community PRs merged in one pass, releases on crates.io and npm with signed provenance — and a broken package that taught me why you test instead of infer.
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ijexa: synthesizing a Candomblé rhythm in pure Python
The Ijexá groove as code — five instruments, a 149ms master slot, flam strokes on the lead drum, and a master drum that phrases instead of looping.
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johnenrique.tech: rebuilding this site in the open
From a 2019-looking portfolio with 3MB hero images to a fully static Next 16 site with two client components — the rework you're reading right now.
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maya: I built SolidJS-style reactivity in Go — to prove it shouldn't be built
A complete fine-grained reactive framework compiled to WASM, 149 tests, benchmarks — and the measured conclusion that killed it. The conclusion is the deliverable.
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MemBot: the project that got me hired, refactored to keep its own promise
An AI journaling app whose LinkedIn post landed my current job — and whose 2024 TODO ('Implementation of LangChain') I finally delivered with a LangGraph StateGraph.
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pardal: a Clay-style layout engine that renders PDFs
Flexbox-like constraint solving in TypeScript, in production for real documents — and the rendering bug I caught by looking at the output instead of the exit code.
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perceptrons: neural networks from scratch, one historical era at a time
From Rosenblatt's 1957 perceptron to MLPs with human-in-the-loop feedback — backpropagation in pure numpy, with a React canvas to draw the inputs.
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physics-lab: ray tracing a black hole inside a fragment shader
Nine GPU simulations of modern physics — Schwarzschild geodesics integrated per pixel, Schrödinger via split-step Fourier, a CHSH Bell test.
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rust-agent-sdk: porting Anthropic's agent SDK to Rust, sessions first
793 tests, a pluggable SessionStore with in-memory, Postgres and Redis backends behind one conformance suite — and the discipline of porting a contract 1:1.
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stockprecog: a quant study designed not to fool me
Cross-sectional prediction on Brazilian equities with a López de Prado evaluation ruler — where the honest, partly negative finding is the contribution. Published with a DOI.
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tabletop-p2p: a 3D virtual tabletop with no game server
Rust + Bevy, WebRTC between peers, the GM as the authoritative host — low-poly terrain you can deform, procedural SVG art rasterized at runtime.
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termo.txt: my personal site as a terminal, over-engineered on purpose
An xterm.js terminal emulator serving a PT-BR Wordle, hand-rolled event sourcing in append-only JSONL, and session auth — all for a site nobody asked me to build.
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week-schedule: drag and drop with no library
A weekly scheduling grid — 30-minute slots, collision detection, drag previews — built on raw pointer events to understand what dnd libraries actually do.
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Blog
Notes on software engineering — systems, tooling and lessons from real projects.