Synapse
Think wider, then reach a conclusion you can defend.
Direct download, Developer ID notarized · What is new · Privacy
Overview
Synapse is a native macOS brainstorming app built on a smooth mind-map canvas: paper cards on a dot grid, with pan, zoom, and branch edges. The structure of the map is always yours. The AI never builds it for you, and it never turns your nodes into a chat thread. And the map is alive: branches rest as dim embers while quick signals travel them, each pulse carrying a node's belief in its color, the way signals move through real neurons.
Instead, the AI acts only on a node you point it at, through eight thinking verbs: Ask, Challenge, Find the gap, Find evidence, Verify, Elaborate, Expand, and Distill. Whatever it produces lands as a typed card on the canvas. Every node sits on a belief line, false, doubt, open, hunch, fact, or verified, shown as its color, so the map reflects how sure you are, not just what you thought. When the thinking is done, 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 exactly what the conclusion rests on.
Synapse 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 on your Mac with import and export, and a Converge result exports as a Markdown or PDF brief.
Features
From scattered thoughts to a conclusion you can defend.
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Neural signals
The map speaks while you think. Color is a belief speaking and white is the app at work: judged ideas report up their branch, open questions receive slow pale nudges, a changed mind fires twice with the old color trailing the new, and standing conflicts collide head-on in both sides' colors. An activity slider sets how alive the canvas feels, from still to electric.
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Converge
The headline action reads the whole map and produces a structured result: ranked options, a written verdict set in a serif face, and a this-rests-on block. It never returns a bare conclusion without its reasoning.
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The eight thinking verbs
Act on a selected node with Ask, Challenge, Find the gap, Find evidence, Verify, Elaborate, Expand, or Distill. Each verb already knows the branch it lives in, and each result lands as a typed card, never as a chat thread. Verify checks a claim against the web and offers a corrected version when it finds a real error.
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The belief line
Every node is false, doubt, open, hunch, fact, or verified, shown as its color. A "How sure are you" control recolors the node live, and the signals carry that color along the branches.
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Tension edges
Dashed contradiction edges you create by hand or accept from an on-demand scan. Never created automatically.
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Bring your own key
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 and attaches real source titles and URLs to the card.
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Local-first storage and export
Maps are plain JSON files with rolling backups and atomic writes, plus import and export. A Converge result exports as a Markdown or PDF brief.
Version history
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1.0.028 June 2026
First release. A living mind-map canvas where neural signals carry each idea's belief along the branches, with activity and speed controls. Belief line colors on every node, eight thinking verbs including Verify with real web checking, 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
Synapse keeps everything on your Mac. 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 go to the provider you chose, using your own key. 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 →