أَنَا كَفَيْتُ مُهِمَّتَكَ
I was the one who took care of your important matter.
If the listener attributes the work to someone else, initial “I” can reverse that belief. If the listener is undecided between two people, it identifies the agent. If the agent is already known, the fronting can primarily reinforce the assertion.
Thus fronting should not be mechanically equated with one absolute exclusivity claim. Its precise force depends on the belief under correction and the conversational setting.