Story

Hi HN,

A couple of months ago I posted an early version of this Chrome extension. Since then I’ve refined it, fixed a bunch of stability issues, and it was recently featured on the Chrome Web Store’s “Featured” section, which was a nice surprise.

What the extension does: – Detects the active tweet or thread directly in the browser – Collects relevant context (parent tweet, author info, thread shape) – Formats a prompt and sends it to the OpenAI API – Inserts the generated reply straight into Twitter’s native reply box

All of this happens inside the X.com DOM, without storing any user data.

Technical bits: – Uses MutationObserver to track X.com’s constantly changing DOM – Handles dynamically inserted tweet nodes, shadow DOM, and thread expansions – Debounces context extraction to avoid unnecessary re-runs – Simulates native input events to inject the reply so it feels built-in – Avoids backend state; everything is read client-side except the final API call

Challenges: – X.com changes UI structure often, so selectors break unpredictably – Preventing duplicate injections when the DOM re-renders – Keeping prompt size small enough for fast generation – Reducing overhead so the extension doesn’t slow down the page

Recent improvements: – More stable tweet/thread detection – Better context selection logic – Cleaner UI in the reply popup – Small performance fixes and race-condition fixes

Chrome Store page: https://chromewebstore.google.com/detail/xinsightai-ai-reply...

Would appreciate feedback from people who’ve built browser extensions or dealt with X.com’s DOM patterns. Happy to discuss any details.