SumizAI vs Lumen AI

What Lumen AI is

What Lumen AI is

Lumen is a minimalist macOS productivity app combining notes, tasks, and an AI assistant in one Markdown-based workspace. The app doesn't lock users into a platform — data is kept as plain Markdown files in a local vault the user picks themselves, with no account registration required.

Key features

A full Markdown editor supports links between notes and backlinks, and a meeting-audio capture feature automatically generates notes and extracts concrete action items from them. You can also paste content from any app straight into the AI chat for summarization and build a custom prompt library with personal context.

Who it's for

Lumen appeals to macOS users who value the GTD methodology and the Markdown format, who want to combine notes, tasks, and an AI assistant in one place without being locked into a proprietary data format.

Use cases

In practice, Lumen works well for automatically turning meetings into notes with concrete action items, organizing an inbox of thoughts and ideas according to your own GTD structure, and quickly summarizing pasted content from other apps through the built-in AI chat.

Pricing and business model

Lumen offers a free version. Optional AI features require your own API keys for OpenAI and a speech-to-text service — similar to SumizAI, the app doesn't resell access to the model, it passes it through directly via the user's own key.

Limitations and what to watch for

The app is available exclusively on macOS, with no Windows, Linux, or mobile version, ruling out users on other platforms. Setting up your own API keys for AI features requires an extra step you wouldn't need in tools with built-in, paid model access — only after that step does the first ai notes entry land in the local vault.

AI notes pasted from any app

Thanks to the ability to paste content from any app directly into the AI chat, saving a fragment of a conversation with the assistant as an ai notes entry in Lumen is quick — it lands straight in the local Markdown vault, with links to related notes already in the system.

Your own API key as common ground with the BYOK approach

Lumen's decision to require your own API keys instead of built-in, paid model access is the same "bring your own key" approach SumizAI also takes — the user pays the model provider directly, and the app remains just the interface.

What's worth checking before choosing

Before choosing Lumen, check whether you already have your own API key for OpenAI and a speech-to-text service, since without them the app's AI features remain unavailable.

Bottom line

Lumen is a minimalist notebook and task manager for macOS with optional AI on your own key, at the cost of being limited to one platform. Anyone who wants ai notes from AI conversations to land automatically in a vault regardless of platform will find a better-fitting tool in SumizAI.

Comparison with SumizAI

Lumen and SumizAI share a philosophy of your own API key and Markdown files with no platform lock-in, but differ in scope and availability. Lumen combines notes, tasks, and AI exclusively on macOS. SumizAI focuses on the conversation with an AI model itself as the note source — question, answer, Markdown file in the vault with an automatic title and table of contents — available on macOS, Windows, iOS, and Android. Anyone who wants to combine GTD-style tasks with notes exclusively on a Mac will pick Lumen; anyone who wants these notes from AI conversations to be created automatically on any platform will find SumizAI the better-fitting tool.

What SumizAI is

A note-taking application built around a conversation with an AI model. You ask a question, the answer streams back, and the answers worth keeping become Markdown notes — filed into a vault that is a folder on your own disk.

A vault is a directory holding base.md, a generated table of contents up to six levels deep, and a notes/ folder with one .md file per note. Before a note is written it is checked against the ones already there, so the fourth note about the same idea gets merged instead of added. Links between notes are ordinary Markdown links to files that exist.

The model is never ours: you bring your own API key to one of seven providers — Anthropic, OpenAI, Gemini, Groq, OpenRouter, a local Ollama or your own server — and pay that provider directly. A question sends the table of contents plus at most five relevant notes within a 24,000-character budget, and the app shows you which five it used.

Every answer kept this way becomes one of these ai notes, ready to search again months later without hunting back through old chats.

Side by side

Where they differ

• Both mention AI. The difference is whose key it runs on: SumizAI never resells inference — you connect one of seven providers (Anthropic, OpenAI, Gemini, Groq, OpenRouter, a local Ollama or your own server) with your own API key and pay that provider directly. Check what Lumen AI does with the model bill before comparing prices.
• Lumen AI is free and SumizAI costs a dollar a month after a seven-day trial that takes no card. A dollar is what it costs to run accounts and licences without reselling the model; if free is the requirement, Lumen AI wins that row outright.
• Both keep Markdown, which makes moving between them mostly a matter of copying files. In SumizAI a vault is a directory holding base.md — a generated table of contents — and a notes/ folder with one .md file per note.
• Lumen AI is described in terms of linking notes together. SumizAI links them too, but deliberately without a syntax of its own: a link is an ordinary Markdown link, [Title](file-name.md), and the model may only point at a file that actually exists. There are no wiki-style [[…]] links to lose on export.
• Lumen AI also does tasks. SumizAI does not — no boards, no due dates, no projects. It files knowledge, not work.
• AlternativeTo lists no mobile version of Lumen AI. SumizAI runs on macOS, Windows, iOS and Android.

Which one to pick