HMR doesn't work with `"aot": false`

[anhallbe]

Command

serve

Is this a regression?

• Yes, this behavior used to work in the previous version

The previous version in which this bug was not present was

No response

Description

When angular.json is configured with "aot": false, HMR doesn't work at all.

Minimal Reproduction

1. Create a project with ng new
2. In angular.json, add "aot": false to the build options (i.e projects > project > architect > build > options
3. Run ng serve
4. In the browser, open the dev tools & network tab
5. Make a change in any file, e.g the component HTML, TS, or CSS
6. Notice that the browser does a full refresh

Exception or Error

Your Environment

_                      _                 ____ _     ___
    / \   _ __   __ _ _   _| | __ _ _ __     / ___| |   |_ _|
   / △ \ | '_ \ / _` | | | | |/ _` | '__|   | |   | |    | |
  / ___ \| | | | (_| | |_| | | (_| | |      | |___| |___ | |
 /_/   \_\_| |_|\__, |\__,_|_|\__,_|_|       \____|_____|___|
                |___/
    

Angular CLI: 19.2.12
Node: 22.15.1
Package Manager: npm 11.4.0
OS: darwin arm64

Angular: 19.2.11
... common, compiler, compiler-cli, core, forms
... platform-browser, platform-browser-dynamic, router

Package                         Version
---------------------------------------------------------
@angular-devkit/architect       0.1902.12
@angular-devkit/build-angular   19.2.12
@angular-devkit/core            19.2.12
@angular-devkit/schematics      19.2.12
@angular/cli                    19.2.12
@schematics/angular             19.2.12
rxjs                            7.8.2
typescript                      5.7.3
zone.js                         0.15.0

Anything else relevant?

Issue can be reproduced regardless of browser and OS.

[clydin]

This is expected behavior. The build system requires knowledge of the Angular components within the application to be able to send partial updates of individual components. With JIT mode, Angular components are compiled in the browser and the build system only sees TypeScript code.

JIT mode is typically not recommended outside of testing scenarios.

[anhallbe]

That's what I feared, although I was hoping the answer would be something different since we're stuck with JIT for the foreseeable future... 😅

Thanks for the explanation.

On a related note: A warning message or some kind of log would probably help others in a similar situation. The only HMR-related message we're seeing is the one saying that it's enabled:

Component HMR has been enabled.
If you encounter application reload issues, you can manually reload the page to bypass HMR and/or disable this feature with the `--no-hmr` command line option.
Please consider reporting any issues you encounter here: https://github.com/angular/angular-cli/issues

[alan-agius4]

Closed via #30362