How it works

Your AI companion, entirely on your phone

PlusOne is a conversational AI app built around a single idea: your words never leave your device. No account to create, no server processing your messages, no one on the other end reading what you said. Here's exactly how that works.

Getting started

Download PlusOne from the App Store

The app itself is small. Install it like any other app — no account, no email, no sign-up flow.

Download a model (one-time, ~1.5–2 GB)

The first time you open PlusOne, it downloads an open-source language model to your phone over Wi-Fi. This is a one-time download. Once it's on your device, the app works completely offline — forever. No subscription required just to chat.

Start talking

Type your message and get a response. That's it. Your conversation history is stored locally in the app's private storage — only visible to you, never synced to a cloud server.

What PlusOne is good for

PlusOne fills the gaps in your day when you want to think out loud, kill some time, or just have someone to bounce things off — without the overhead of texting a real person at 11pm about whether you should reorganize your schedule.

VentingSomething frustrating happened and you want to say it out loud to something that will actually respond.

Planning out loudWalk through your week, your to-do list, your options for a decision — it helps to verbalize.

Casual banterDumb jokes, random trivia, "would you rather" questions. Low stakes conversation for its own sake.

Creative playStory prompts, character ideas, brainstorming concepts, writing feedback on a rough draft.

Thinking through problemsExplain something you're working through. The act of articulating it often helps, even if the response isn't perfect.

Commute or downtimeSomething to do that's more engaging than doomscrolling but lower commitment than a podcast.

How the on-device model actually works

No network calls during conversations

After the initial model download, PlusOne makes zero network requests when you send a message. Your text goes from your keyboard directly into the model running in your phone's RAM. The response is generated on your device's processor (Apple Silicon, specifically the Neural Engine) and displayed on screen. Nothing touches a server.

This is fundamentally different from cloud AI like ChatGPT or Claude, where your message is encrypted and sent to a remote server, processed, and sent back. Those services are faster and use more capable models — but your words leave your device every time.

Where your data lives

Conversations are stored in the app's private local storage on your iPhone — the same sandboxed storage that only PlusOne can access. They're not uploaded to iCloud (unless you've enabled general iCloud device backup in your iOS settings). They're not sent to any server we operate.

If you delete the app, all conversations are deleted. There's no account to log back into, no server-side backup. Gone is gone.

The tradeoffs

On-device models are smaller than the models powering ChatGPT or Claude. They're capable of good conversation, but they may occasionally give vague answers, lose track of context in very long chats, or produce responses that feel less polished. That's the tradeoff for running entirely offline, on a phone, with no data leaving your hands.

For casual conversation — which is what PlusOne is designed for — these models work well. They're not writing academic papers; they're having a chat.

Optional: on-device image generation

Ask PlusOne for a picture — "draw me a rainy city at night" or "make a cartoon of a tired programmer" — and it generates one using a Stable Diffusion model running directly on your device. Same deal as the chat model: the image request never leaves your phone. The output is generated in your phone's RAM and displayed in the conversation. No image prompt is sent to a server.

Image generation requires a separate one-time model download and works best on recent iPhone hardware (iPhone 15 Pro and later). It's optional — you can use PlusOne for chat without ever downloading the image model.

Important: what PlusOne is not

PlusOne is not therapy. It's not a mental health tool, not a clinical intervention, and not a substitute for professional support. The AI is not trained as a therapist, cannot diagnose anything, and should not be used for crisis support.

PlusOne is not medical advice. Don't ask it about symptoms, dosages, or treatment decisions. Consult an actual doctor.

PlusOne is not a substitute for real relationships. It can be a useful conversational outlet, but it's a tool, not a person. If you're feeling isolated or struggling, please reach out to someone in your life or a professional.

If you're in crisis: call 988 (Suicide & Crisis Lifeline, US), text HOME to 741741 (Crisis Text Line), or call your local emergency number.