Ok, I have a short update - if I remove the annotations completely, property injection works again. So the problem seems to be the @ApplicationScoped annotation.

I'm doing nothing special with beans.xml, it's a file that is basically empty:

<?xml version="1.0" encoding="UTF-8"?>
<beans>
</beans>

And here is one of the beans that causes this problem:

@ApplicationScoped
public class TextProvider
{
    private final Logger logger = LoggerFactory.getLogger(getClass());

    private ResourceBundle resourceBundle;

    @Inject
    @ConfigProperty(name="i18n.language")
    private String language;

    @PostConstruct
    void setupResourceBundle()
    {
        logger.info("language = {}", language);

        resourceBundle = ResourceBundle.getBundle(Messages.class.getName(), new Locale(language));
    }

    public String getText(String key)
    {
        return resourceBundle.getString(key);
    }

}

In the case shown above, language will always be null. If I remove @ApplicationScoped (and thus make the bean a dependent bean), the property gets injected. If I apply @Singleton (and thus "promote" the bean to an EJB), the property also gets injected.

Ok, I solved the riddle why things are happening. I am basically hit by this problem: http://rmannibucau.wordpress.com/2012/12/11/ensure-some-applicationscoped-beans-are-eagerly-initialized-with-javaee/

In short: my Camel Routes are triggered using a Thread ContextClassLoader (TCCL) from bundle A, the beans that serve as the processors inside the route are (partially) from bundle B. Due to the "lazy" initialisation of my processors the resolution of the properties uses the TCCL from A when it tries to initialise the processors from B. That's why they cannot be found, because the property file from A does (obviously) not contain the properties for bundle B.

In the dependent pseudo-scope case the component that triggered an "eager" initialization was a bean that was annotated @Singleton @Startup. Likewise, promoting the beans to an EJB also triggered an eager init.

I now have to find a way to either eagerly initialize my CDI beans or I have to "promote" all of them to EJBs :/