Patreon's engineering team just published a deep dive on their seven-year TypeScript migration. The part that stuck with me: the typed foundation had to come first, or none of the tooling could be trusted. Wrote up a how-to on that infrastructure-first approach, including an interactive diagram showing how a small number of core files can do most of the type coverage work across an entire codebase: https://rachel.fyi/posts/gravity-centers-typescript-migration