Per-folder instructions for Claude and ChatGPT

Custom AI instructions,
per folder.

Different folders, different rules. Claude and ChatGPT read your folder-level instructions every time they touch a note. Tell them your conventions once. Stop re-explaining yourself.

Start writing the rules Read the docs

Free to start. No credit card required.

The problem with one global setting

One AI. Many kinds of work.

ChatGPT's Custom Instructions are one global box. Claude's system prompt is one global box. Both treat your whole life as a single project.

But you don't work that way. Your runbooks need step-by-step format. Your customer interviews need the quote up front. Your recipes need metric units. Cramming all of that into one prompt makes none of it work well.

Hjarni puts the rules where the content is. Each folder has its own.

Inheritance, in pictures

Rules stack on the way down.

Open a note deep in the tree. Claude and ChatGPT read every rule on the way to it.

The AI Instructions panel inside a Personal > Projects > React > Bugs folder in Hjarni, listing four stacked rules: Personal Root 'Prefer bullets. Lowercase titles.', Projects 'Tag with project name. Link related notes.', React 'TypeScript code blocks. Cite the React docs.', and the current folder 'Always include reproduction steps and severity.' — The four layers of rules that apply inside Projects > React > Bugs. Hjarni hands all of them to whichever AI opens a note here.

The AI Instructions panel on the Edit Bugs folder page, showing Personal Root, Projects, and React rules already applied, with a textarea below for writing the rule that applies to Bugs. — Writing the rule for Bugs. The three layers from above are visible; your textarea adds the fourth.

Works with both

Claude and ChatGPT. Same rules.

Hjarni's MCP server hands your folder instructions to whichever AI is reading the note. No vendor lock-in. No copy-paste between tools.

Claude

Connect via MCP. Two minutes.

Set up Claude

ChatGPT

Connect via MCP. Two minutes.

Set up ChatGPT

What it isn't

Not the same as Custom Instructions or Projects.

ChatGPT Custom Instructions

One global box. ChatGPT only. Same rules whether you're writing recipes or shipping production code.

Claude Projects

One system prompt per project. Flat. No folder hierarchy. No inheritance. Claude only. Your ChatGPT doesn't see it. Compare Hjarni vs Claude Projects.

Notion AI / Obsidian Copilot

Bolted-on AI. No instruction system. No way to tell the AI how to behave inside a specific folder.

Hjarni

Instructions at every folder, with inheritance. Team-wide rules for shared conventions. Same rules apply whether you're in Claude, ChatGPT, or any other MCP client.

From a consultant

I wanted a cloud knowledge base I could use as memory for my AI, in plain Markdown, with read and write access. Nothing else fit. Hjarni did. What sold me was how light and well defined the MCP is. My AI used to choke when I pasted Markdown and config files into a chat. It reads them perfectly from Hjarni. The folder-level AI instructions and the knowledge graph are the parts I did not know I needed.

Jack, GTM Strategy Consultant

Tell your AI your rules. Once.

Set up your first folder instructions in two minutes. Free to start.