The package's vitest base configs were outside every gate — no tsconfig and no typecheck script meant tsc never saw them. Add a tsconfig with allowImportingTsExtensions (vitest.base.jsdom imports ./vitest.base.node.ts by extension) and an explicit include of the base configs + vitest config, plus the typescript/@types/node devDeps to run it. (S6) Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>