How I Built a Claude Code Plugin That Intercepts Grep and Replaces It With Semantic Search

Claude Code plugins shipped a few months ago and the ecosystem is exploding. But most tutorials stop at "here's a slash command that prints hello world." This post walks through building a real, production plugin from scratch: one that indexes your codebase with embeddings, does hybrid semantic search, and automatically intercepts grep calls to give Claude better results. By the end you'll understand every piece of the Claude Code plugin system: hooks, commands, skills, agents, and how they wire together. The plugin we're building is Beacon, which I open sourced at github.com/sagarmk/beacon-plugin . The Problem Claude Code uses grep and ripgrep to find code. This works fine for small projects, but falls apart on larger codebases: Searching "authentication flow" won't find login_handler , verify_token , or session_middleware Claude burns context window reading dozens of irrelevant files trying to find the right code New sessions on a 100k line codebase can eat 50k+ tokens just on explor