Agent Arnold – Gym tracker 100% vibe-coded from my phone between sets

Agent Arnold is a gym tracker with a built-in AI coach. Here's how I use it:

- "this exercise hurts my shoulder at the end of the movement, remind me proper form and cues"

- "how should I modify my workout today based off last week's reps and weights"

- `/generate` a bouldering-focused workout routine

The app is free, your data is fully exportable (no walled-gardens), and there's an anonymous global leaderboard for motivation, including a "Dishonored" shameboard for anyone caught faking their numbers.

I decided to 100% vibe-code this project, a part of it is halluci-coded. I purposely haven't touched a single line of code, though I've reviewed most of it. The project started as just my own workout split, but friends wanted to try it so I added routines, then feature requests started coming in and I basically just forwarded them to my CLI agents.

Vibe-coding is far from perfect, but since I'm a daily user of my own app I catch bugs immediately, sometimes literally in the gym while SSHing from my phone between sets.

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Tech stack: - FastAPI + SQLite on a Linux box - React PWA (works offline) - AI coach powered by Claude via Anthropic API - Telegram OAuth + Resend magic-link auth - Sentry for error tracking, Foursquare Places for gym location

The whole thing was built with Claude Code. Vibe-coded with Claude, and the AI coach is also Claude. It's Claude all the way down.

https://agent-arnold.app/

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What do you hate about your current fitness tracker? I might fix that.