Time travel debugging AI for more reliable vibe coding
Hi HN, I'm the CEO at https://replay.io. We've been building a time travel debugger for web apps for several years now (previous HN post: https://news.ycombinator.com/item?id=28539247) and are combining our tech with AI to automate the debugging process. AIs are really good at writing code but really bad at debugging -- it's amazing to use Claude to prompt an app into existence, and pretty frustrating when that app doesn't work right and Claude is all thumbs fixing the problem. The basic reason for this is a lack of context. People can use devtools to understand…
In plain words
Replay.io combines time travel debugging technology with AI to help automate the debugging process for web applications. The platform records app behavior and provides AI systems with tools to explore and understand what happened during execution, addressing the gap where AI excels at code generation but struggles with problem-solving. It is designed for developers who use AI to build applications and need better debugging capabilities when things go wrong.
written from the facts on this page · September 2026
From the sources
In the maker’s words, at launch
Hi HN, I'm the CEO at https://replay.io. We've been building a time travel debugger for web apps for several years now (previous HN post: https://news.ycombinator.com/item?id=28539247) and are combining our tech with AI to automate the debugging process. AIs are really good at writing code but really bad at debugging -- it's amazing to use Claude to prompt an app into existence, and pretty frustrating when that app doesn't work right and Claude is all thumbs fixing the problem. The basic reason for this is a lack of context. People can use devtools to understand what's going on in the app, but AIs struggle here. With a recording of the app its behavior becomes a giant database for querying using RAG. We've been giving Claude tools to explore and understand what happens in a Replay recording, from basic stuff like seeing console messages to more advanced analysis of React, control dependencies, and dataflow. For now this is behind a chat API (https://blog.replay.io/the-nut-api). We recently launched Nut (https://nut.new) as an open source project which uses this tech for building apps through prompting (vibe coding), similar to e.g. https://bolt.new and https://v0.dev. We want Nut to fix bugs effectively (cracking nuts, so to speak) and are working to make it a reliable tool for building complete production grade apps. It's been pretty neat to see Nut fixing bugs that totally stump the AI otherwise. Each of the problems below has a short video but you can also load the associated project and try it yourself. - Exception thrown from a catch block unmounts the entire app: https://nut.new/problem/57a0b3d7-42ed-4db0-bc7d-9dfec8e3b3a5 - A settings button doesn't work because its modal component isn't always created: https://nut.new/problem/bae8c208-31a1-4ec1-960f-3afa18514674 - An icon is really tiny due to sizing constraints imposed by other elements: https://nut.new/problem/9bb4e5f6-ea21-4b4c-b969-9e7ff4f00f5b - Loading doesn't finish due to a problem initializing responsive UI state: https://nut.new/problem/486bc534-0c0e-4b2a-bb64-bfe985e623f4 - Infinite rendering loop caused by a missing useCallback: https://nut.new/problem/496f6944-419d-4f38-91b4-20d2aa698a5e Nut is completely free. You get some free uses or can add an API key, and we're also offering unlimited free access for folks who can give us feedback we'll use to improve Nut. Email me at [email protected] if you're interested. For now Nut is best suited for building frontends but we'll be rolling out more full stack features in the next few weeks. I'd love to know what you think!
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