An app is a saved set of instructions that shapes how CruxAI behaves while it is active — a reusable persona for work you do repeatedly. Open Apps from the sidebar and select New App.
The basics
- Name — required, up to 100 characters.
- Category — General, Coding, Writing, Creative, Business, Education, Productivity, Entertainment, Roleplay, or Analysis.
- Icon — an emoji, or upload your own PNG, JPEG, WebP, or GIF.
- Description — up to 500 characters, shown to anyone browsing your app.
The system prompt
This is the part that matters. Up to 4,000 characters defining how the app should respond, what it should know, and where its boundaries are. Be concrete:
- State the role and the audience, not just the topic.
- Describe the output shape you want — length, format, whether to show working.
- Say what the app should refuse or redirect, not only what it should do.
- Give one short example of a good response if the format is unusual.
Let CruxAI write it
The AI App Builder panel at the top of the editor is a chat assistant for the app you are building. Describe your idea and it drafts the fields for you; ask for changes and it revises them. It is usually faster than writing a system prompt from a blank box.
Declared capabilities
Three toggles state what your app can do: Web Search, Vision / Image Analysis, and Memory. Anyone considering your app sees these before using it, so declare them honestly — this is the transparency contract that makes public apps trustworthy.
Visibility
- Draft — a work in progress, not usable yet.
- Private — only you can use it. This is the default.
- Public — submitted to the App Library, subject to review before it appears.
Your work is autosaved as you edit, and you can move an app between these states at any time.
Custom apps always run in Fast mode, and CruxAI's core safety guidelines stay active regardless of what a system prompt says.