ng build command generating index.csr.html instead of index.html

I used to run ng build to produce a build for my Angular 18 application. It always worked fine, generating an index.html file. However, today it suddenly started generating an index.csr.html file instead, and I can't figure out why.

I use Firebase Hosting and a GitHub Action to automatically deploy the build. Since it is not generating an index.html, the deployment fails. Everything was running fine until yesterday.

To work around this issue, I have to manually rename index.csr.html to index.html, and then the deployment works fine.

Following is the output to the ng build command.

Application bundle generation complete. [15.184 seconds]

▲ [WARNING] Module 'undici' used by 'node_modules/@firebase/auth-compat/dist/esm/index.node.esm.js' is not ESM

  CommonJS or AMD dependencies can cause optimization bailouts.
  For more information see: https://angular.dev/tools/cli/build#configuring-commonjs-dependencies


▲ [WARNING] Module 'undici' used by 'node_modules/@firebase/auth/dist/node-esm/internal.js' is not ESM

  CommonJS or AMD dependencies can cause optimization bailouts.
  For more information see: https://angular.dev/tools/cli/build#configuring-commonjs-dependencies


▲ [WARNING] Module 'faye-websocket' used by 'node_modules/@firebase/database/dist/node-esm/index.node.esm.js' is not ESM

  CommonJS or AMD dependencies can cause optimization bailouts.
  For more information see: https://angular.dev/tools/cli/build#configuring-commonjs-dependencies

Solution

I encountered a similar problem. I realized that to generate a simple index.html you need to turn off the SSR. I changed two fields in angular.json

     "prerender": false,
     "ssr": false