Getting started

1. Download the app

Caspian ships as a single desktop app for Windows, macOS, and Linux, no account and no cloud workspace required. Grab the build for your platform from the download page and install it like any other desktop app.

2. Pick a Workbench folder

The first time Caspian opens, it asks you to pick or create a Workbench folder - an ordinary directory on your disk. That's the whole setup: no sign-up, no server to configure. Every note Caspian creates from then on is a plain Markdown file inside that folder, readable in any text editor even without Caspian installed.

Once it's created, Caspian asks how you want to proceed: Full Venture Studio (create a Caspian account, or sign in, to use Pro) or Just Scaffolding, which shows how to point your own AI tools at these docs and your Workbench folder. See Free and Pro.

3. Install or create a workspace

A workspace in Caspian is called a canvas - a tracker, dashboard, map, live feed, or any interface you can describe, with notes pinned to the parts that matter. From Create a new project, describe what you want and Caspian builds it for you with your AI tool, or choose I'll write my own project to install a canvas you built yourself.

User registration, unchecked by default, lets people create an account and sign in to the project, and lets it have pages only signed-in people can open (see below). Leave it off for a personal tool or a prototype. You can change it later in the project's Project Settings tab.

4. Pin your first note

Click (or drop a pin, or draw a region, depending on the canvas) on the part of the workspace your note is about, and start writing in plain Markdown. The note is saved straight to your Workbench folder as you go - there's nothing separate to sync or publish for it to be "saved."

Use the AI tool you already have

Caspian's AI builds and changes run on an AI coding tool already installed and signed in on your computer, on that tool's own login and plan, so there's nothing extra to pay. It works with Claude Code, OpenAI Codex CLI, Gemini CLI, Cursor CLI and Devin CLI.

• Pick it in Copilot: the tools Caspian finds show as tags above Copilot's message box, and on the confirm card before a build or change. Each tool can use its own model. The confirm card shows "On your <tool> plan" instead of a price.
• It only sees what Caspian sends. Each call is one prompt in and one reply out, run from an empty temporary folder with the tool's own file, shell, web and MCP tools switched off.
• Not installed or signed in? Caspian tells you how to install the tool, or the command to sign in (for example claude, codex login or agent login).

With a Pro account, Caspian Pro shows as another tag, and can be picked instead of your own tool.

Tell Copilot about your project

Every project has a Markdown file, Context (context.md), that Copilot reads on every request, whichever AI tool or model is active. Open it from the right sidebar.

It is the project's memory: what it's for, what's been decided, and what's changed. Its sections are Brief (your original description), Decisions and Current state (Copilot keeps these up to date after each change it applies, and you can edit them), Change log (one line per event, written by the app), and Notes. Notes is yours: Copilot never rewrites it and treats it as the final word.

Section headings are locked in the editor, since the app relies on them. You write under them. If context.md is edited outside Caspian and its structure breaks, the Context tab shows a red "!" and the app stops writing to the file until it's fixed. Context is read-only while Copilot is working on the project.

It lives in the project's own versions/ folder, next to its canvas.json - see folder layout. The built-in Image, 3D model, Map, and Webpage projects get their own copy, with a context file, the first time you change them with AI.

User registration

With User registration on, a project can have sign-up and sign-in - ask Copilot for it ("add accounts", "make the dashboard members-only"), or build it into your own canvas. Its pages can be marked as signed-in only, and Caspian itself won't show those pages to anyone who isn't signed in.

If it's off and you ask Copilot for something that needs accounts, Copilot says so on its proposal and offers a Turn on User registration button. Copilot never turns it on by itself: nothing changes until you click it, and you can also proceed without accounts.

• Database tab (in the right sidebar, under Context): the project's accounts - who signed up, when, and what they entered at sign-up; who is signed in right now, with a Sign out button; and Remove for any account. Passwords are only ever stored as hashes.
• Synced with the live site. Accounts you make while trying the project out in Caspian are kept in the project's own database.json. Once the project is published, they stay in two-way sync with the live site's accounts, automatically and with a Sync now button, so the Database tab shows everyone. New accounts on the live site confirm their email with a 6-digit code before they can see anything personal.
• Project Settings turns User registration on or off. Off closes sign-in and the signed-in-only pages, and signs everyone out. Accounts are kept for when you turn it back on.

Free and Pro

Caspian is free to use, with AI that runs on the tool you already have. Pro adds Caspian's own models, and more.

Using Pro's models: sign in with your Pro account and every AI build and change runs on Caspian Pro, with no API key. Before a build or change, the confirm card suggests a model and lets you pick another. Caspian splits each build or change into its real parts, named in the progress checklist, and runs it in one step when it fits the model. If a first build fails, its entry stays in the file explorer: click it to retry or delete it. Token Usage (next to Account in the right sidebar, once you're signed in) shows your usage per model and how much of this month's AI allowance you've used; it resets on the 1st.

Change projects in small steps (beta, off by default) is a switch in Token Usage. With it on, new builds and Copilot changes are made by an agent that reads the project's files and edits them a few lines at a time, then loads each page and checks it for errors before it's done, instead of rewriting whole pages.

On the website, Free is called Just Scaffolding and Pro is called Full Venture Studio. To get it, open Account → Subscription in the app, or email hello@caspian.md.