Is there an explanation why the original code fails for the reported Theia based application but does not fail for the Theia IDE?

From my understanding the existing code should work as for every non-default preference a change event should be sent when the preferences are loaded. This feels like fixing a symptom while missing some underlying root cause.

Edit: Is it possibly a race condition between the preference service loading and the startup of the ai package, i.e. there is no guarantee that we catch all events?

I further investigated this. I think, this happens, because we have a "license check". We overwrite FrontendApplication.start and halt startup until a process that is started by the backend confirmed, that the user has a valid license for our product.
In the mean time, the PreferenceService seems to become ready.

As I understand now, the FrontendApplicationContribution.initialize function are treated really time sensitive, but I'm still not sure, if this guarantees, that PreferenceService does not initialize faster.
I checked different locations, where FrontendContribution.initialize uses preferences:

• MonacoTextMateService both fetches the preference and registers to the PreferenceChangeEvent, as I originally proposed.
• HostedPluginController only registers the command

I still think, when attaching to the PreferenceChangedEvent, the current state should be retrieved as well. But as FrontendApplicationContribution.initialize is time sensitive, we should not wait until the service becomes ready.

We still might need to rethink how to do our license check.

@mvtec-richter thanks for the additional context. I think the suggestion by @msujew is the best of both worlds, so if you adapt the code to:

protected updateEnableValue(enable: boolean): void {
  if(enable !== this.isAiEnabledKey.get()){
        this.isAiEnabledKey.set(enableValue);
        this.onDidChangeAIEnabled.fire(enableValue);
   }
}

initialize(): MaybePromise<void>{

  this.isAiEnabledKey = this.contextKeyService.createKey(ENABLE_AI_CONTEXT_KEY, false);
  // make sure we don't miss once preferences are ready
  this.preferenceService.ready.then(() => {
     const enableValue = this.preferenceService.get<boolean>(PREFERENCE_NAME_ENABLE_AI);
     this.updateEnableValue(enableValue);
  }

  this.preferenceService.onPreferenceChanged(e => {
      if (e.preferenceName === PREFERENCE_NAME_ENABLE_AI) {
          this.updateEnableValue(e.newValue);
      }
  });
}

Then this should improve the current situation without any performance issues. Note that I did just type this here into the GH issue, so there might be some issues with the code when copied as is.