I haven't done it with Claude Code itself, but I've built a deterministic + inferential engine that works inside a defined discipline with defined purposes. Broad enough to be practical, niche enough for most of the world to look at me funny.
The short version: let logic decide, and if there are multiple solutions let the model reason within a fixed range grounded by GraphRAG. Test every output against the logic, re-parse on contradiction, and emit 'unsure' after a couple of iterations rather than guessing.
It's no use for general knowledge. But where the judgement is largely codifiable it holds up well. There's an edge case out there that'll turn it to custard, I just haven't found it yet.
I've connected Claude Desktop to it over MCP and the results are good, not great. I designed the thing so I'm working in the sweet spot and there's still the occasional WTF.