{
  // The build-tool configs run in Node, not the browser: they need node types and must NOT be
  // checked against the app's DOM lib. Split out because tsconfig.json's `include` is ["src"],
  // so until now nothing type-checked these files at all. `npm run typecheck`
  // runs this project alongside src and e2e.
  "compilerOptions": {
    // composite: required to be the target of tsconfig.json's `references` (which is what makes
    // editors check these files under THIS config instead of an inferred one). A composite project
    // may not disable emit (TS6310), so it emits declarations only, into node_modules — nothing
    // lands in the repo and nothing reaches the bundle. Hence `tsc -p` without --noEmit below.
    "composite": true,
    "declaration": true,
    "emitDeclarationOnly": true,
    "outDir": "./node_modules/.tmp/tsconfig-node",
    "tsBuildInfoFile": "./node_modules/.tmp/tsconfig-node/.tsbuildinfo",
    "target": "ES2022",
    "module": "ESNext",
    "moduleResolution": "bundler",
    "lib": ["ES2022"],
    "types": ["node"],
    "strict": true,
    "skipLibCheck": true,
    "noUnusedLocals": true,
    "noUnusedParameters": true,
    "noFallthroughCasesInSwitch": true,
    // An index read is `T | undefined` here, as it really is (0 errors when switched on).
    "noUncheckedIndexedAccess": true,
    "resolveJsonModule": true,
    // The build-tool configs include a hand-written .js file (postcss; tailwind 4 needs no config
    // file, and the stale `tailwind.config.js` entry pointed at nothing). checkJs runs
    // the type checker over it via its `@type` JSDoc, so a bad option is caught by the gate instead
    // of silently mis-building CSS. Was the last unchecked file.
    "allowJs": true,
    "checkJs": true
  },
  // reactPlugin.ts is the ONE React transform both configs import — it is build tooling,
  // not app source, so it belongs here and not under tsconfig.json's ["src"]. A file imported by a
  // listed one but absent from `include` is TS6307, not a silent pass. playwright.config.ts is
  // here as well as in e2e/tsconfig.json because eslint's typed rules find a file's project
  // through tsconfig.json's `references`, which name this project and not the e2e one.
  "include": [
    "vite.config.ts",
    "vitest.config.ts",
    "reactPlugin.ts",
    "devOnlyGuard.ts",
    "playwright.config.ts",
    "postcss.config.js"
  ]
}