Over the last couple of days, while working on other things, I worked with Claude Code to write a Mermaid diagram editor with live edit in the browser, vim bindings, and live chart updates. It has an MCP server and a CLI tool that can also talk to the API, so I can use it in writing plans with Claude. Claude can live update the drawing and pull in edits that I made, or make changes based on stuff I tell it. VERY nice iteration on my workflow.