The AI-native knowledge base for Cursor

Cursor knows your code. Hjarni gives it everything that is not in the repo: architecture notes, decisions, runbooks, and conventions.

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What this unlocks

Workflows that actually use your context

Get the why for any architectural choice

Ask Cursor why the auth layer uses a custom middleware. It searches your Hjarni decision log, finds the ADR, and answers from the actual reasoning instead of guessing.

Reuse a debugging session

The same Sidekiq retry bug, six months later. Cursor finds your runbook in Hjarni, walks through what you tried, and skips the dead ends.

Onboard a new repo without re-explaining

Point Cursor at the Hjarni folder for that project. Conventions, deploy steps, gotchas. It reads them before suggesting any code, so the first PR fits the codebase.

Capture the lesson before you forget it

After a tricky refactor, tell Cursor to write a Hjarni note describing the new pattern, tag it for the team, and link it from the relevant ADR. Next week's Cursor reads it back.

One source of truth alongside .cursor/rules

Keep repo-specific rules in .cursor/rules where they belong. Keep cross-project conventions, decisions, and runbooks in Hjarni. Cursor reads both, so neither place gets bloated.

Setup

Connect Cursor in about two minutes

1
Sign up for Hjarni and create a folder for the project Cursor will work on.
2
Open ~/.cursor/mcp.json (or .cursor/mcp.json inside the repo for per-project scope).
3
Add the Hjarni entry above to the mcpServers object. Restart Cursor.
4
Cursor opens a browser window for the Hjarni OAuth flow. Sign in and authorize.
5
Open the Cursor agent and ask it to search Hjarni for one of your notes. The tools should appear.

~/.cursor/mcp.json or .cursor/mcp.json per project

{
  "mcpServers": {
    "hjarni": {
      "url": "https://hjarni.com/mcp"
    }
  }
}

The Hjarni MCP endpoint is https://hjarni.com/mcp. The connection uses OAuth, so you sign in with your Hjarni account when prompted. No API key files to manage.

Why Hjarni alongside .cursor/rules and AGENTS.md

READMEs, AGENTS.md, and files in .cursor/rules belong in the repo. They are good for in-repo conventions. They are not the place for cross-project decisions, runbooks, or context that is awkward to commit. Hjarni is account-scoped, so the same notes follow you between projects and across machines, alongside whatever rules already live in each repo.

Cursor's agent is great when it has facts to work with. Without them, it falls back to common patterns and guesses at your codebase. Hjarni gives it your actual decisions, runbooks, and trade-offs through MCP, so suggestions match how the codebase already works.

Embedding your wiki into a vector database is real engineering: an indexer, a search server, an embedding pipeline to keep current. Hjarni is the notes and the MCP server in one product. There is nothing to operate.

Common questions

Questions before you connect Cursor

Where does the Cursor MCP config file live?

Globally at ~/.cursor/mcp.json, or per-project at .cursor/mcp.json. Cursor reads both. Project-level wins for that project.

Why use Hjarni in Cursor instead of just opening files?

Cursor sees your repository. Hjarni stores everything that is not in the repo: architecture decisions, debugging notes, deploy steps, past incidents, customer feedback. Hjarni gives Cursor that context on demand.

Does Hjarni work with Cursor's agent mode?

Yes. Cursor's agent treats MCP tools as first-class. It can search Hjarni, read notes, create new ones, and link them, the same way it uses any other tool.

Is Hjarni listed in Cursor's plugin marketplace?

A Cursor marketplace plugin is in the works. Until then, add the URL directly to your mcp.json. The setup is two lines of JSON.

Can I scope Hjarni to one repository?

Yes. Put .cursor/mcp.json in the repo and commit it. Hjarni is only loaded inside that project. Use the global config for personal notes.

Give Cursor a memory

Write notes once. Cursor reads them across every conversation.

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Write once. You both remember.

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Give your AI a memory

Works with Claude and ChatGPT today. Gemini coming soon.