OpenKnowledge – open source AI-first alternative to Obsidian/Notion
Hi HN, Nick here. We’re launching OpenKnowledge (https://openknowledge.ai/), a “what you see is what you get” markdown editor that has direct integrations with Claude, Codex, and other agents. Available as MacOS app or Web UI+CLI. Fully free/local and OSS. We built this because we wanted a Notion-like experience for writing and sharing markdown files across our team. Obsidian is the best alternative we tried, but found it doesn’t have a true WYSWIG UI and it didn’t integrate well with Claude/Codex outside of community plugins. So we built OpenKnowledge. It takes…
In plain words
OpenKnowledge is a free, open-source markdown editor available as a macOS app or web UI with CLI. It features a true WYSIWYG interface and direct integrations with AI agents like Claude and Codex, allowing users to edit documents side-by-side with AI tools. Built for teams wanting to write and share markdown files with a Notion-like experience, it includes a file navigator, link explorer, and built-in RAG capabilities for LLM workflows.
written from the facts on this page · September 2026
From the sources
In the maker’s words, at launch
Hi HN, Nick here. We’re launching OpenKnowledge (https://openknowledge.ai/), a “what you see is what you get” markdown editor that has direct integrations with Claude, Codex, and other agents. Available as MacOS app or Web UI+CLI. Fully free/local and OSS. We built this because we wanted a Notion-like experience for writing and sharing markdown files across our team. Obsidian is the best alternative we tried, but found it doesn’t have a true WYSWIG UI and it didn’t integrate well with Claude/Codex outside of community plugins. So we built OpenKnowledge. It takes shape as: 1. A MacOS app with a file navigator, the WYSIWYG editor, and link explorer. 2. Integrations with the Claude, Codex, and Cursor desktop apps. The agents can open an OpenKnowledge editor within their embedded web browsers for a side-by-side experience. 3. Built-in mcps, skills, and RAG for LLM-wiki and “AI Second Brain” scenarios + spec writing 4. An embedded terminal and CLI for TUI-first users OSS stack includes: Tiptap/prosemirror, CodeMirror, yjs (CRDT), Electron (MacOS app), Orama, remark/rehype/micromark/mdast, @pierre/trees On the architecture side, the interesting eng. challenges included: 1. A pipeline to convert ProseMirror to markdown in a bidirectional lossless way. ProseMirror uses ASTs, which are not designed to have byte-fidelity. 2. A dual-observer CRDT to keep the ProseMirror and markdown state in-sync. The CRDT + git also power a collaborative experience that shows what Agents are doing in the markdown, have undo/redo, and version history. The “Share” and cloud-sync functionality are geared for team collaboration. They feel “no-code” but leverage git/GitHub under the hood, which also means data stays fully private. In that spirit, we made OpenKnowledge open source for anybody who’s curious or who’d like to contribute. We’re actively thinking about plugins/extensibility and what’s next. If you have suggestions or feedback, would love to hear it.
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