AI python coder in Claude

We are building a trading app, divided into 10 modules, each with 3-5 python scripts. We've been primarily using Claude to help us write the code, but it's been hallucinating and producing code that we didn't specify. We have detailed dev specs, anti-drift instructions and guardrails, yet we're still having this problem. We need someone who can show us a process for using Claude to efficiently deliver accurate code without the drift, hallucination and constant rewrites.