founder and product engineer in berlin and sf. studied cs at CODE and Stanford
currently building Attacal: AI agents that attack your app every day and open a pull request for every hole they find
experience
- stealth sf consumer studio, full stack engineer: owned a bot-free AI meeting notetaker for mac and windows end to end
- shipped features with customers, ran support, infra, deployment and analytics
- idea to launch in 2 weeks, 200 paying customers and $4k revenue in 4 weeks, 800 users in 6
- PlayTheHype, entrepreneur in residence: built new products and internal tools
- Lore: AI market research on tiktok and instagram, 1.2M+ videos analyzed for nike and mastercard
- Commis: tiktok comment reporting with auto scraping, a telegram bot and bulk sync, killed the weekly excel copy and paste
- Pro & Me, founders associate: new business opportunities and business development for a tiktok agency
- built the finance, productivity and fulfillment automations, stepped in as pm when needed, 3.7M+ views on the campaigns
- Young Founders Network, co-founder at 16: built germany's largest community for founders under 25
- 2,200+ members, chapters in 20+ cities, 5 to 100+ volunteers, €350k+ raised for entrepreneurial education
- Cinoramic, founder at 14: freelance web dev studio, €20k+ revenue while still in school
notable projects
- voz: free, offline dictation for mac, talk and the text appears where you type (website)
- YBudget: open source budget software for german associations, YFN runs the whole NGO on it (ybudget.de)
- Bernie Bouncer: ios app blocker with an AI bouncer, you talk your way past him to open tiktok
- FaktenChecken: free tiktok fact checker for kids, awarded by the Liz Mohn Stiftung and germany's first lady (live)
- joelGPT: a GPT from scratch in numpy (write-up)
other projects
2025
- TreeMatch: directory of stanford summer session students by skills and courses, 60 students joined, course teams formed through it (live)
- HiCarla: AI phone agents for car dealerships and doctors' practices
2024
- Running Finder: map of running clubs and events in berlin, built solo
- Escaper: trip planning for friend groups, MVP tested with real groups
2023
- Rememberry: flashcards inside a mind map with spaced repetition, built with a team at uni
- Roast.design: design feedback as comments placed on the design itself
earlier
- How to Fail While Start-Up: founder interview podcast, IT Newcomer of the Year 2022
- si:cross: working student at a podcast startup for 2.5 years next to school
- Mate Equipment: e-bike affiliate blog, made money for 5 years during school
- YouTube: minecraft and tech tutorials from 10 to 14, 50k views
stack
- typescript, swift, python
- react, next.js, vite, tanstack, tailwind, shadcn, expo / react native, electron
- hono, trpc, supabase, postgres, drizzle, convex, clickhouse
- cloudflare workers, vercel, docker, github actions, posthog
find me on joels.tech, x, linkedin or by email