Calling 'subscribe' in "reactive" methods

Reports subscribe() calls in "reactive" methods.

Methods returning a Publisher type (including Flux and Mono) should not call the subscribe() method directly because it can break the reactive call chain.

Instead of using subscribe(), consider using composition operators like flatMap(), zip(), then(), and so on.

Example:

  Flux<String> stringFlux(){
    Flux<String> flux = Flux.just("abc");
    flux.subscribe(); // <- blocking 'subscribe' call in non-blocking context
    return flux;
  }

Locating this inspection

By ID

Can be used to locate inspection in e.g. Qodana configuration files, where you can quickly enable or disable it, or adjust its settings.

CallingSubscribeInNonBlockingScope

Via Settings dialog

Path to the inspection settings via IntelliJ Platform IDE Settings dialog, when you need to adjust inspection settings directly from your IDE.

Settings or Preferences | Editor | Inspections | Reactive Streams | Reactor

Suppressing Inspection

You can suppress this inspection by placing the following comment marker before the code fragment where you no longer want messages from this inspection to appear:

//noinspection CallingSubscribeInNonBlockingScope

More detailed instructions as well as other ways and options that you have can be found in the product documentation:

IntelliJ IDEA 2025.2

Inspection Details
By default bundled with:	IntelliJ IDEA 2025.2, Qodana for JVM 2025.2,

Last modified: 18 September 2025