Originally published at parvejshah.com/blog/building-manifest-v3-ai-chrome-extensions by Parvej Shah.
When we started building Leadswave — a LinkedIn brand assistant Chrome extension — the plan seemed straightforward. Detect LinkedIn post elements in the feed, attach a small AI companion button to each one, let users generate engagement responses without leaving the page. A week's work, maybe two.
Three weeks later we were still fighting style collisions, service worker lifecycle bugs, and a Manifest V3 API constraint we hadn't anticipated. This is what we learned.
Why Injecting into a Third-Party Page Is Complicated
When your content script injects HTML into LinkedIn's document, you're working inside a page you don't control, with styles you didn't write, against a DOM structure that changes in LinkedIn's deployments without your knowledge.
