Does skipLibCheck cut TypeScript build cost at the risk of hidden dependency type errors?

For a low-traffic TypeScript workload, such as a small internal service that is built and deployed only occasionally, the dominant cost of a clean build is type checking, and the large set of third-party declaration files under node_modules contributes a significant share of that work.

TypeScript's documented skipLibCheck compiler option skips type checking of all .d.ts files, which can materially reduce compiler work. The trade-off is unresolved: errors that originate in a third-party declaration file are no longer caught during compilation and may only surface at runtime or in a later CI stage. The option is often paired with incremental, which caches build state in a .tsbuildinfo file; as of recent TypeScript 5.x releases this is documented behavior, but the build-info format is version-sensitive and can change between major versions.

The open decision is whether the compile-time savings justify weaker guarantees about third-party types, and what policy should define acceptable risk.

• Does enabling skipLibCheck meaningfully reduce clean-build type-checking cost for a dependency-heavy project, and which classes of declaration-file errors does it leave undetected?
• How should a team decide between skipLibCheck and full declaration checking, and what measurement can quantify the difference on a given codebase?