How DeftBrain is built

TL;DR

A React single-page app with an Express/Node backend, hosted on Railway. Each of 120+ tools sends input to Claude and the response streams back in parts as they are ready. Everything is checked after it's on screen. The site runs in 13 languages, and every page is prebuilt as static HTML.

Stack

React + Tailwind · Node / Express · Claude via the Anthropic SDK (mostly Sonnet; Haiku and Opus for particular steps) · Server-Sent Events · Railway. Share images are drawn from code with satori and resvg.

Under the hood

• Output in parts. Long answers are split into several simultaneous requests, each writing its own section. First output usually shows within seconds; the rest stream to the page as they finish.
• Decide first, then write. Where parts must agree — a verdict or a list of findings, for example — one brief step decides it and the other requests are informed, so sections do not contradict each other. Shared checks run once all output is delivered.
• Grounded where it matters. Tools that deal with rules, prices, venues and the like perform web lookups and cite their sources.
• 13 languages. Answers are available in 13 languages, with local currencies and customs.
• Prebuilt pages. Every tool and guide is prebuilt as a static page for search engines and AI assistants.
• Strict gates before every push. Zero lint warnings, catalog-wide audits and translation completeness are confirmed before anything ships.
• Private by design. No accounts. Nothing you type is stored on our servers; tool history remains in your browser. (See the privacy policy.)
• Built by “Bruce”, working primarily with Claude, with assistance from Gemini and ChatGPT.

Contact

Questions, comments or suggestions: email Bruce@DeftBrain.com.