Updated 15 Oct 2026
Best AI stack for an AI chatbot app
An AI assistant that answers questions about your documents, products or knowledge base.
| Role | Tool & why | Price |
|---|---|---|
| Builder | Lovable Builds the chat UI and wires an AI model through its backend. | Free (5 build credits/day, up to 30/mo); Pro from $25/mo (100 credits), $21/mo billed annually |
| Builder (some code) | Replit Agent Agent builds and hosts backend logic and API calls in one place. | Free Starter; Core $20/mo ($18/mo billed annually); Pro $100/mo |
| Database | Supabase Stores chats and documents; pgvector for search over your docs. | Free (500 MB DB, 2 projects, pauses after 1 week idle, 50k MAU); Pro from $25/mo |
| Login | Supabase Auth Limit usage per user. | Included with Supabase: 50,000 MAU free; 100,000 on Pro |
| Payments | Lemon Squeezy If you charge a subscription, it handles global tax. | No monthly fee; 5% + 50c per transaction (merchant of record) |
| Analytics | PostHog See which questions people ask. | Free 1M analytics events + 5K session replays per month, forever |
Estimated cost at launch
~$26/mo + AI model usage (~$5–20/mo at launch)
Copy-paste starter prompt
Build an AI chatbot that answers questions about the PDFs I upload. Users sign in, upload PDFs, and chat with them; answers cite the page they came from. Store documents and chat history in Supabase (use pgvector for search). Limit free users to 20 messages a day.
Personalise this for my idea →
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Prices checked on official pricing pages on 15 Oct 2026; confirm before buying. Some links may be affiliate links.