I open-sourced alternative to ReplyGuy — AI replies on Reddit, Twitter/X & HN for $50/month

I built MentionMaster as a paid SaaS, ran it for a year, and today I'm open-sourcing the full backend. Here's what it does, how it works, and how to run 600 AI-powered mentions/month for ~$50. 🎬 Demo The Problem If you're a founder or indie hacker, you know this loop: Someone on Reddit asks "what tool helps with X?" — your product is the perfect answer You never see it A competitor replies, gets the customer Manual monitoring doesn't scale. Paid tools like ReplyGuy charge $49–$299/month. So I built my own and now I'm giving it away. What It Does MentionMaster monitors Reddit, Twitter/X, Hacker News, YouTube, and TikTok for posts matching your product keywords. When it finds a relevant post, it: Scores it for relevance (saves OpenAI API costs — no point replying to irrelevant posts) Generates a context-aware reply using GPT-4o-mini Queues it for your review Publishes on approval, with auto-translation if your product targets non-English markets Tech Stack Layer Tech API FastAPI Backgro