Latest writings
Runs in Production, Crashes Locally — Six Lessons a Rust Project Taught Me
Six problems encountered building LOL-AI-Intelligence: async/blocking boundaries, debug assertion traps, UI architecture refactors, error handling, i18n, and line endings. Each one cost me hours.
eFootball Scraper Tech Deep Dive: From JA3 to the Cookie Hack
How my eFootball player data scraper went from 38,000 requests to 1,177 — TLS fingerprint spoofing, Perlin noise rate limiting, circuit breaker backoff, and the cookie discovery that saved the day.
eFootball Player.bin Reverse Engineering Notes: What Four Screw-Ups Taught Me
From FF mode losing skills, an editor that couldn't find players, to CSV validation false alarms — four pitfalls in eFootball player data reverse engineering and the lessons behind them.
From Blocked to Blazing Fast: A Scraping Showdown, Live
Goal: scrape all 37,650 player card records from pesdb.net. From TLS fingerprint exposure, multi-threaded crashes, to discovering a single Cookie that saves 97% of requests — a complete record of an anti-anti-scraping battle.
Can AI Be Objective? Come On — It Didn't Even Choose What It Gets to See
Many people think of AI as perfectly rational — more neutral than humans, free of emotion. But here's the problem: AI never learned from the real world. It learned from the world humans allowed it to see.
A Case Sensitivity Issue That Made Me Debug for an Entire Afternoon
Built a LoL desktop assistant with Tauri + Rust. All skill values were showing 0. Checked the data layer, frontend, backend — finally found the bug hiding in a HashMap key.
Selected projects
eFootball Research Platform
Reverse-engineered a 14.7MB binary. Cracked 26 abilities, 63 skill bits, 6 AI styles, Form/Injury. Python GUI editor + scraper extracting 37,650+ player records.
PESDB Large-Scale Scraper
TLS impersonation scraping with curl_cffi Chrome fingerprinting, Perlin-noise rate limiting, and cookie injection — 97% request reduction.
League of Legends Desktop Assistant
CS2 Tournament Database
Hey, I'm Jiahao Ren.
I'm a Computer Science student at the University of Waikato. I enjoy figuring out how systems work — recently, that has meant reverse engineering eFootball player data, building AI-powered tools, and turning failed experiments into blog posts.
I don't just list technologies — I build complete pipelines: reverse engineering binary formats, scraping 37K+ records with anti-detection tooling, modeling tournament databases, and shipping desktop apps to real users. When something breaks, I write about it.
Skills & Tools
Get in touch
Feel free to reach out about projects, tech stacks, or dev workflows.