tsconfig.json

{
  "compilerOptions": {
    /* Apps Script runs on V8, which supports ES2019 features. */
    "target": "ES2019",
    "lib": ["ES2019"],

    /* Use ESNext modules so Rollup can tree-shake and bundle them. */
    "module": "ESNext",
    "moduleResolution": "Bundler",

    /* Output directory — Rollup handles this, but tsc needs it for type checking. */
    "outDir": "./dist",
    "rootDir": "./src",

    /* Strict type checking. */
    "strict": true,
    "noImplicitAny": true,
    "noUnusedLocals": true,
    "noUnusedParameters": true,
    "noImplicitReturns": true,

    /* Interop helpers. */
    "esModuleInterop": true,
    "forceConsistentCasingInFileNames": true,
    "skipLibCheck": true,
    "resolveJsonModule": true,

    /* Only auto-include these @types packages — prevents @types/jsdom from
       bleeding in via jest-environment-jsdom and colliding with the GAS MimeType global. */
    "types": ["google-apps-script", "jest"],

    /* Emit declarations alongside JS for IDE support. */
    "declaration": true,
    "declarationDir": "./dist/types",
    "sourceMap": true
  },
  "include": ["src/**/*.ts"],
  "exclude": ["node_modules", "dist", "__tests__", "src/client"]
}