vue-cli upgrade from v3 to v4 breaks build process with thread-loader error: Cannot read property 'options' of undefined

Question

I just upgraded vue-cli from v3 to v4. Development mode works! But build process errors out with:

 error  in ./src/App/components/AppLayout.vue?vue&type=script&lang=js&

Module build failed (from ./node_modules/thread-loader/dist/cjs.js):
Thread Loader (Worker 0)
Cannot read property 'options' of undefined
    at PoolWorker.fromErrorObj (/home/vsonline/workspace/node_modules/thread-loader/dist/WorkerPool.js:26
2:12)
    at /home/vsonline/workspace/node_modules/thread-loader/dist/WorkerPool.js:204:29
    at mapSeries (/home/vsonline/workspace/node_modules/neo-async/async.js:3625:14)
    at PoolWorker.onWorkerMessage (/home/vsonline/workspace/node_modules/thread-loader/dist/WorkerPool.js
:170:35)
    at /home/vsonline/workspace/node_modules/thread-loader/dist/WorkerPool.js:152:14
    at Socket.onChunk (/home/vsonline/workspace/node_modules/thread-loader/dist/readBuffer.js:36:9)
    at Object.loader (/home/vsonline/workspace/node_modules/vue-inheritance-loader/src/index.js:26:32)

 @ ./src/App/components/AppLayout.vue?vue&type=script&lang=js& 1:0-458 1:474-477 1:479-934 1:479-934
 @ ./src/App/components/AppLayout.vue
 @ ./src/App/router/index.js
 @ ./src/main.ts
 @ multi ./src/main.ts

Answer 1

vue.config.js: parallel: false is working for me.