jestjs/jest · error · Error

Jest: Failed to parse the TypeScript config file

Error message

Jest: Failed to parse the TypeScript config file ${configPath}
  ${error}

What it means

A wrapper error thrown in the outer catch of readConfigFileAndSetRootDir when the config file is TypeScript (.ts/.mts/.cts) and loading failed for any reason. The original error is attached as {cause} and its message is inlined, so the message may itself contain nested error text (including the combined 'both with native and configured loaders' preamble from the inner throw).

Solutions

Read the inlined inner error and {cause} to identify the real failure (syntax, missing module, version)
If native TS failed, ensure Node 22.18+/23.6+ or add a @jest-config-loader pragma with an installed loader
Run npx tsc --noEmit jest.config.ts to surface type errors independently
Temporarily move logic to a jest.config.js to isolate whether the failure is TS-specific

Example fix

// before: jest.config.ts references uninstalled preset
export default { preset: 'nonexistent-preset' };

// after
export default { preset: 'ts-jest' };  // ensure it is installed

Defensive patterns

Strategy: try-catch

Try / catch

try {
  const config = await readConfigFileAndSetRootDir(configPath);
} catch (err) {
  // err.cause holds the underlying load error
  console.error('Config load failed:', err instanceof Error ? err.message : err);
  if (err instanceof Error && err.cause instanceof Error) {
    console.error('Underlying cause:', err.cause.message);
  }
  throw err;
}

Prevention

Type-check jest.config.ts independently with tsc --noEmit before running Jest
Keep config files small and side-effect-free to reduce parse-time failures
Ensure all imports inside the config resolve (run the file directly with node/tsc)

When it happens

Trigger: Any uncaught error while loading a .ts/.mts/.cts config: syntax errors, invalid TypeScript, failed imports inside the config, missing native TS support combined with missing ts-node, or runtime exceptions thrown by the config function.

Common situations: Type errors in jest.config.ts that the IDE didn't flag; config importing a module that isn't installed; referencing <rootDir> in TS before normalization; or a combination of old Node + missing ts-node.

Understand the failure class

Parsing and encoding errors: unexpected token, malformed input — why parsers reject input and how to find the real culprit.

Related errors

AI-assisted analysis of jestjs/jest@8e6d128e4a (2026-08-10). Data as JSON: /api/errors/34c2a70c650f9f77. Report an issue: GitHub.

Appendix: source

Thrown at packages/jest-config/src/readConfigFileAndSetRootDir.ts:97

              '  both with the native node TypeScript support and configured TypeScript loaders.\n' +
              '    Errors were:\n' +
              `    - ${requireOrImportModuleError}\n` +
              `    - ${loadTSConfigFileError}`
            );
          }
        }
      } else {
        configObject = await loadTSConfigFile(configPath);
      }
    } else if (isJSON) {
      const fileContent = fs.readFileSync(configPath, 'utf8');
      configObject = parseJson(stripJsonComments(fileContent), configPath);
    } else {
      configObject = await requireOrImportModule<any>(configPath);
    }
  } catch (error) {
    if (isTS) {
      throw new Error(
        `Jest: Failed to parse the TypeScript config file ${configPath}\n` +
          `  ${error}`,
        {cause: error},
      );
    }

    throw error;
  }

  if (configPath.endsWith(PACKAGE_JSON)) {
    // Event if there's no "jest" property in package.json we will still use
    // an empty object.
    configObject = configObject.jest || {};
  }

  if (typeof configObject === 'function') {
    configObject = await configObject();
  }

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