you replace in the MethodDictionary, the original CompiledMethod with a proxy

Yes - OBBreakpoint uses this "object as methods trick" in its #install method. But what if already a proxy is installed (one for breakpoint) and you want to have another proxy ... BTW: Attached is a short MCZ to add an own OB command. Note that there is an extension to OBCommandBrowser to get it to work. You should see a 'Toggle ToDo' after installing it and opening a new browser in Pharo 1.3. This can help you to get started. bye T. -- Empfehlen Sie GMX DSL Ihren Freunden und Bekannten und wir belohnen Sie mit bis zu 50,- Euro! https://freundschaftswerbung.gmx.de