Cairn
Think wider, reach a defensible conclusion
Overview
Cairn is a native macOS brainstorming tool built on a smooth mind-map canvas of paper cards on a dark dot grid, with pan, zoom, and branch edges. A disciplined AI layer sits on top: it never builds the map for you and never turns nodes into a chat thread. It only acts on a node you point it at, through six thinking verbs (Ask, Challenge, Gap, Evidence, Expand, Distill), and whatever it produces lands as a typed card on the canvas. Every node carries an epistemic state, none, hunch, fact, verified, or contradicted, shown as its color, so the map reflects how sure you are, not just what you thought. The headline action, Converge, reads the whole map and collapses it into a ranked set of options with a written verdict and a block that shows what the conclusion rests on.
Tension edges mark contradictions you create by hand or accept from an on-demand scan. Cairn is bring-your-own-key: it works with Anthropic, OpenAI, Google Gemini, a custom OpenAI-compatible endpoint, or a local model, and your keys live only in the macOS Keychain. There is no account, no sign-in, and no hosted inference. Maps are plain JSON files under Application Support with import and export, and a Converge result exports as a Markdown or PDF brief.
Features
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Mind-map canvas
Paper cards on a dark dot grid with branch edges, pan, and zoom. The structure of the map is always yours; the AI never builds it for you.
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The six thinking verbs
Act on a selected node with Ask, Challenge, Gap, Evidence, Expand, or Distill (keys A, C, G, E, X, D). Each result lands as a typed card, never as a chat thread.
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Epistemic confidence colors
Every node is none, hunch, fact, verified, or contradicted, shown as its color. A How sure are you control recolors the node live, so the map shows how sure you are.
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Converge
The headline action reads the whole map and produces a structured result: ranked options, a written verdict in a serif face, and a this rests on block. It never returns a bare conclusion without its reasoning.
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Tension edges
Red dashed contradiction edges created by hand or by an on-demand scan you accept or dismiss. Never created automatically.
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Lineage-aware context
A verb on a deep node already knows the branch it lives in, ancestors plus siblings, assembled server side before the call.
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Bring your own key
Works with Anthropic, OpenAI, Google Gemini, a custom OpenAI-compatible endpoint, or a local model. Keys live only in the macOS Keychain. No account, no sign-in, no hosted inference.
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Streaming responses
Prose verbs stream tokens onto the card as they arrive, with a Stop button that cleanly drops the in-flight response.
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Evidence with real citations
The Evidence verb uses each provider's native web search (Anthropic web_search, OpenAI web_search_options, Gemini google_search grounding) and attaches real source titles and URLs.
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Local-first storage and export
Maps are plain JSON files under Application Support with rolling backups, atomic writes, and import and export. A Converge result exports as a Markdown or PDF brief.
Screenshots
Version history
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1.0.028 June 2026
First release. Mind-map canvas with epistemic confidence colors, the six thinking verbs, Converge with ranked options and a this-rests-on block, tension edges, streaming responses, and bring-your-own-key support for Anthropic, OpenAI, Gemini, custom, and local models with keys in the macOS Keychain. Local-first JSON storage with import, export, and Markdown or PDF briefs. Developer ID signed and notarized DMG.
Privacy
Your data stays on your device
Cairn keeps everything on your Mac. Your maps are local JSON files and your API keys live in the macOS Keychain. There is no account, no sign-in, no analytics, and no telemetry. The app only reaches the network when you take an explicit AI action, and only your selected node and its branch context are sent to the AI provider you chose, using your own key. Nothing else leaves your Mac. When you use the Evidence verb, that provider runs its own web search to gather citations. AI output can be wrong and should be checked before you rely on it.
Read the full privacy policy →