TypeScript 7.0 Project Corsa: Go Rewrite Migration Guide

TypeScript 7.0 (Project Corsa) rewrites the compiler in Go, delivering roughly 10x faster type-checking and 3x lower memory usage. Real-world benchmarks show VS Code's 1.5M-line codebase dropping from 89s to 8.7s. The native binary (`tsgo`) is already available as `@typescript/native-preview` on npm. Key breaking changes include strict mode on by default, removal of ES5 target, removal of `baseUrl`, removal of legacy `node10` module resolution, and removal of AMD/UMD/SystemJS output. TypeScript 6.0 (released March 2026) serves as a migration bridge, surfacing deprecation warnings for everything 7.0 will enforce. The recommended migration path is: upgrade to 6.0 and fix all deprecation warnings, test with the preview compiler, then upgrade to 7.0 when it ships (mid-to-late 2026). The TypeScript language itself, tsconfig format, and type semantics remain unchanged.