Claude isn't a chat app anymore. It's a runtime. The interface is still text, but the architecture underneath is execution: load context, pick tools, call APIs, write files, schedule work. Most people are still typing at it like ChatGPT in 2023 and wondering why their workflow hasn't changed. The shift happened quietly, across four primitives. Each one shipped without much fanfare. Together they're what "advanced" means in 2026: not a longer prompt, but a better-wired one. This piece is the primer. The four things to understand before you can use Claude well. The mental model The outdated framing: Claude is good at writing, explaining, coding. The 2026 framing: Claude is a runtime that loads skills, scopes memory in projects, calls external systems through MCP, and executes multi-step work in Cowork. Same model file, completely different surface. The question used to be "what can Claude do?" The question now is "what can I wire into Claude?" That reframe is the whole article.…