Persona

Persona lets you build an agent with the personality you want, then tune it and share it as a file. You answer five questions about how you like to be talked to. About a minute later you have a persona with a name, a portrait, and its own voice. Sliders set how strongly each trait shows. It works by steering the model, not by prompting it. Persona vectors (Chen et al., 2025) show that traits like sarcasm or warmth are linear directions in a model's activations. Persona finds those directions inside Muse Glimmer 30B and adds them to layer 31 while the model writes. The persona never touches the prompt, so your own instructions still work on top of it. The problem: today, changing an agent's personality means prompt hacks that drift, or a fine-tune that weighs hundreds of MB. A Persona persona is one .persona file of about 230 KB. You can AirDrop it, and it runs fully local on a Mac.