Same goal, opposite hosting choice
Bruin and Hjarni both treat AI agents as first-class readers and writers of your Markdown notes. The defining difference is where the notes and the MCP server live. Bruin is local-first: a macOS app with its server running on your machine and iCloud-based sync between your own devices. Hjarni is hosted: your notes live on EU servers and the MCP server answers from the internet over OAuth.
That single choice decides most of the rest, starting with which assistants can reach your notes.
Reach: desktop-only versus anywhere
Because Bruin's MCP server is local, it serves desktop MCP clients such as Claude Desktop, Cursor, and Claude Code, the tools running on the same Mac. It cannot serve a remote client: ChatGPT on the web and Claude on your phone have nothing to connect to. Hjarni's hosted endpoint is the opposite: any remote MCP client reads and writes your notes from any device. If "I want ChatGPT in the browser to use my notes" is on your list, that is the deciding line.
Where Bruin is genuinely strong
Bruin is open source and free to run yourself, which some people will always prefer. It keeps your data on your own machine. It ships semantic search with local embeddings, a knowledge graph, and a deliberate draft, review, published workflow so a human approves what an agent writes before it lands. If local-first ownership and an explicit approval gate are non-negotiable, Bruin is built exactly for that.
Where Hjarni is the better fit
Hjarni trades self-hosting for reach and sharing. It runs in any browser plus native iOS and Android apps, every connected assistant on every device reads the same notes, and shared team spaces with folder-level AI instructions let a whole team work from one source of truth. It uses full-text search rather than embeddings, and instead of a publish gate it versions every edit and shows what you or your AI changed.
You give up running the server yourself. In return, your knowledge is reachable from everywhere and by everyone you share it with.
Use Bruin when you want a local-first Mac app you fully control. Use Hjarni when you want hosted notes every assistant and teammate can reach from any device.
Can you use both?
Yes. Most MCP clients let you register more than one server. Some people keep Bruin as a local, Mac-only scratch space with a human review gate, and use Hjarni as the hosted memory their web and mobile assistants, and their teammates, share. The notes are plain Markdown on both sides, so moving between them is just an export and an import.