How TypeScript 5.7's --module nodenext Changes Are Breaking Legacy Express Apps (and How to Fix Them)
Most Express app TypeScript failures after upgrading to 5.7 stem from three enforcement changes in --module nodenext that break previously tolerated patterns. Teams discover this when builds that passed in 5.6 suddenly throw module resolution errors with no obvious code changes.
The breaking point arrived when TypeScript 5.7 tightened nodenext mode to match Node.js's actual ESM/CommonJS behavior. Apps that mixed module systems or imported JSON without explicit configuration now fail at compile time. This distinction is critical: the errors surface before runtime, but only after you upgrade.
Understanding the --module nodenext Mode and What Changed in 5.7
TypeScript's nodenext module mode tells the compiler to follow Node.js's native module resolution rules exactly. Before 5.7, the compiler permitted several patterns that Node.js would reject at runtime. The 5.7 release closed those gaps.
