I use Julia at work, which benefits from long-running sessions, because it compiles functions the first time they run. So I wrote a very simple MCP that lets Claude Code send code to a persistent Julia kernel using Jupyter.
It had a much bigger impact than I expected – not only does test code run much faster (and not time out), but Claude seems to be much more willing to just run functions from our codebase rather than do a bunch of bespoke bash stuff to try and make something work. It's anecdotal, but CCUsage says my token usage has dropped nearly 50% since I wrote the server.
Of course, it didn't have to be MCP – I could have used some other method to get Claude to run code from my codebase more frequently. The broader point is that it's much easier to just add a useful function to my codebase than it is to write something bespoke for Claude.
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