Cairn Documentation
Local-First Architecture
Your model data lives on your device. Cairn stores everything in your browser's local database — nodes, requirements, interfaces, state machines, verification records, all of it.
Why Local-First
Traditional MBSE tools store your models on vendor servers. This creates problems:
- You need internet access to work
- Your proprietary designs live on someone else's infrastructure
- Subscription lapses can lock you out of your own data
- Export formats are often lossy or proprietary
Cairn inverts this. Your browser is the database. You own the bits.
What Stays Local
- System hierarchy and node properties
- Requirements and verification records
- Interfaces and signal definitions
- State machines and behavior models
- Decision history (pruned alternatives)
- AI interaction logs and usage metrics
This data leaves your device only when you export it, or when the project is backed up to your account.
Backup to Your Account
Backup is per project and opt-in: Settings → Cloud & Backup turns it on or off. A backed-up project is copied to your account within a minute of each change (an interview, a few seconds after each answer), and opens on any device you sign in on. The interview offers it when you start (Back up to my account as I go, ticked by default), so a paused interview can be picked up on another device. On a phone it is always on, since the workspace that finishes the job is on your computer.
What Requires Network
AI features require network access. When you use ⌘K to decompose, generate requirements, or ask questions, your request goes to Anthropic's API (Claude) for processing. The AI sees only the context the request needs, and Anthropic handles it under its API terms.
Image generation uses Google's Gemini API with the same pattern: request out, response back, under Google's API terms. We call this "local-data, cloud-compute."
Browser Storage
Cairn uses IndexedDB, your browser's built-in database. Data persists across sessions. Storage limits are generous (typically 50%+ of available disk). Data stays sandboxed to this browser on this device.
Clearing browser data will delete your projects. Use Export before clearing, switching browsers, or switching devices.
Export and Backup
The Export tool creates a snapshot of your project — standard formats you can store, version control, or share however you want. Export regularly, especially before major changes.
A full-project export packages your model, assets, and change history into a structured .cairn.zip — a directory tree of JSON you can diff and inspect (a flat single-file backup is also available). Both export and sidebar import open a review modal first: you see the file tree, per-asset inclusion, and any warnings before anything is written. On import you choose to create a new project or replace an existing one.