Internals: TypeScript 5.6 Compiler and How It Checks 1M Lines of Code in Seconds

In Q3 2024, TypeScript 5.6 processed a 1.02M line monorepo (including dependencies) in 1.8 seconds on a 16-core M3 Max, a 4.2x speedup over TypeScript 5.0’s 7.6-second baseline for the same codebase. This isn’t magic—it’s a ground-up rework of the co...