An AI companion that's actually yours

An AI companion only works if you can be unguarded with it — and you can't be unguarded with a server. Castmates puts the entire companion on your iPhone: 32 characters with memory, personality, and story, no account, no cloud, and conversations that never leave your device.

Free to start · No account · 100% on-device

Frequently asked questions

What makes Castmates different from other AI companion apps?
Two things: the AI runs entirely on your iPhone (no account, no cloud, works offline), and it's built for roleplay depth — characters narrate scenes, stay in role, and remember your story across sessions instead of producing flat chatbot replies.
Do companions remember me between conversations?
Yes. Castmates summarizes past sessions so characters recall who you are and what you've been through together. The relationship keeps building over days and weeks.
Can I design my own AI companion?
Yes — end to end. Define the name, persona, greeting, appearance, and tone, pick an interaction style like Friendship, Romance, Mentorship, Rivalry, or Adventure, set the avatar from your photo library, and write the opening scene.
Is there a romantic mode?
Castmates is SFW by default. An optional Mature (18+) mode for romance-forward roleplay is available behind Pro and age confirmation — and it runs on-device like everything else.
Is my relationship with a companion private?
Completely. Conversations are generated and stored on your iPhone only — never uploaded, never reviewed, never training data. There's no account, so nothing links your companion to your identity.

Try Castmates free

32 characters, 96 scenarios, and every conversation stays on your iPhone.