After several months of tinkering, I've found that you can get really far with today's models if you embrace core context engineering principles.
We've gotten claude code to handle 300k LOC Rust codebases, ship a week's worth of work in a day, and maintain code quality that passes expert review. We use a family of techniques I call "frequent intentional compaction" - deliberately structuring how you feed context to the AI throughout the development process.