Chrome 126+ Broke My WXT Extension Dev Setup — Here's What Changed and How to Fix It

I spent a weekend debugging a Chrome extension dev environment that stopped working after a Chrome update. No error messages. The extension loaded — I could open its options page — but content scripts never ran, service workers never started, and the UI stayed unchanged.

This post is about three separate failure modes I hit, why each happens, and the minimal fix for each.

The Setup

The project uses WXT (a Chrome extension framework built on Vite) with a custom dev.sh script that:

Starts the WXT dev server for hot reload