cypress-io/cypress · error · TypeScriptNotFoundError

No typescript installable was found. ts-loader needs a versi

Error message

No typescript installable was found. ts-loader needs a version of typescript to work properly. Please install typescript in your project's package.json.

What it means

Thrown as TypeScriptNotFoundError by @cypress/webpack-batteries-included-preprocessor when require.resolve('typescript', { paths: [configFileDirectory] }) fails. ts-loader needs the `typescript` package present to type-check and emit; the preprocessor tries to resolve typescript from the user's tsconfig directory (when options.typescript === true) or from the explicit path (options.typescript as string), and throws if neither resolves.

Source

Thrown at npm/webpack-batteries-included-preprocessor/index.ts:112

  let typeScriptPath: string | boolean | undefined | null = null

  try {
    if (options.typescript === true) {
      const configFileDirectory = path.dirname(configFile?.path ?? '')

      // attempt to resolve typescript from the user's tsconfig.json file / project directory
      typeScriptPath = require.resolve('typescript', { paths: [configFileDirectory] })
      options.typescript = typeScriptPath
    } else {
      typeScriptPath = options.typescript
    }

    debug(`using typescript found at ${typeScriptPath}`)
  } catch {
    debug('no user typescript found. Throwing TypeScriptNotFoundError')

    throw new TypeScriptNotFoundError()
  }
  // shortcut if we know we've already added typescript support
  // @ts-expect-error - not typed intentionally
  if (options.__typescriptSupportAdded) return options

  const webpackOptions = options.webpackOptions
  const rules = webpackOptions.module && webpackOptions.module.rules

  // if there are no rules defined or it's not an array, we can't add to them
  if (!rules || !Array.isArray(rules)) return options

  // if we find ts-loader configured, don't add it again
  if (hasTsLoader(rules)) {
    debug('ts-loader already configured, not adding again')

    return options
  }

View on GitHub (pinned to 0d85fdc912)

Solutions

Install TypeScript in the project: `npm install -D typescript`.
If using a monorepo, ensure typescript is resolvable from the directory of your tsconfig.json (hoist it or add to that workspace).
If options.typescript is set to a path, verify the path exists and points at a valid typescript module.
Reinstall dependencies if you recently changed Node majors (native modules / hoisting shifts).

Example fix

// before: tsconfig.json present but typescript not installed
// after
npm install -D typescript@5

Defensive patterns

Strategy: validation

Validate before calling

import { createRequire } from 'module'
function ensureTypescriptResolvable(dir: string) {
  try { createRequire(import.meta.url).resolve('typescript', { paths: [dir] }) }
  catch { throw new Error('Install typescript: npm i -D typescript') }
}

Type guard

const isTypescriptResolvable = (dir: string): boolean => { try { createRequire(import.meta.url).resolve('typescript', { paths: [dir] }); return true } catch { return false } }

Try / catch

try { addTypeScriptConfig(file, options) } catch (e) { if (e.name === 'TypeScriptNotFoundError') { /* npm i -D typescript, retry */ } else throw e }

Prevention

List typescript in devDependencies of the project that runs Cypress.
In monorepos, ensure typescript resolves from the tsconfig.json directory.
Validate options.typescript path strings before passing to the preprocessor.

When it happens

Trigger: addTypeScriptConfig reaches the require.resolve('typescript', ...) branch (because options.typescript is true or a path string) and Node throws MODULE_NOT_FOUND. Occurs when TypeScript is not installed in the project, is installed only as a transitive dep not resolvable from the tsconfig dir, or options.typescript points at a nonexistent path.

Common situations: A TS Cypress project where `typescript` was never added to package.json devDependencies, a monorepo where typescript lives in the root but the spec's tsconfig dir cannot resolve it, or a stale npm install.

Related errors

AI-assisted analysis of cypress-io/cypress@0d85fdc912 (2026-08-12). Data as JSON: /api/errors/1d8399359c37619c. Report an issue: GitHub.