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In more detail: Contexts and apis are thread-safe. Regarding whether APIs are singleton or not, the api objects (all apis have just one impl which is the proxy that generates the http requests) are generated here. That provider class is declared to be a singleton, but that applies only to the provider itself; not to the result produced by its get() method. The provider and the api class are bound to the Guice context here and here, and as you can see those bindings are not using .in(Scopes.SINGLETON), so every time the provider is called (an injection is requested or an instance is directly requested to the Guice injector) a new api proxy will be created.
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