Postman for AI – a tool that has been missing for a while

Everyone’s building AI agents nowadays. I have also been building AI agents for several years now. At some point, I got tired of the same friction: vendor playgrounds that don’t support variables or multi-provider comparisons, cloud SaaS tools that are great at one thing (logging, evals, tracing) but force you to stitch four of them together, and all of it routing your prompts and API keys through someone else’s servers. So I (with the help of AI and other humans) built Reticle — a local desktop app for designing, running, and evaluating LLM scenarios and agents. Yes, you could do all of this with code. Just like you can test APIs with curl. But Postman exists for a reason — the right GUI collapses the feedback loop, makes iteration faster, and catches issues you'd only find after shipping. That's what Reticle is trying to be for AI development. Here’s how I built it, and the key decisions behind each part. The stack: Tauri + React + Rust + SQLite Reticle is a Tauri app — a React front