SumizAI vs Tangent Notes

What Tangent Notes is

What Tangent Notes is

Tangent Notes is a notebook designed to let you write the way you actually think — instead of forcing a linear document structure, it lets you link to existing notes and create new ones with ease, right at the moment a thought veers off from the main thread. The app is fully open source under the Apache-2.0 license, meaning full code transparency and the ability for anyone to independently audit exactly how it works.

Key features

Flexible note linking lets you create a link to a new or existing note anywhere in the text with a single gesture, without breaking your writing flow to switch windows or hunt for the right document. A structure that mirrors associative thinking rather than rigid folder hierarchy lets you build a network of connected thoughts the way they actually form in your head — nonlinearly, with digressions and returns to earlier threads. Open source code under the Apache-2.0 license means the developer community can submit fixes, fork the project, and have full confidence the app isn't doing anything hidden with user data.

Who it's for

Tangent Notes appeals to people whose thinking naturally jumps between topics and who get frustrated trying to force that process into the rigid, linear structure of a classic notebook. Writers developing several plot threads at once, researchers tracking connections across different sources, and developers who value open code and the ability to inspect how a tool they use daily actually works all find a natural home here.

Use cases

In practice, Tangent Notes works well for brainstorming, where one thought leads to the next and the user wants to immediately capture every digression as a separate, connected note instead of losing it while trying to cram it into a single document. A researcher reading a paper can create linked notes for each new concept on the fly, building a network of connected definitions and arguments over time. A novelist planning a book uses linking to track relationships between characters and plot threads, returning to them from anywhere in their notes.

Pricing and business model

Tangent Notes is completely free and open source under the Apache-2.0 license. No fees and no subscription model mean the developers aren't dependent on monetizing user data or ads — the project is sustained by its community and, potentially, voluntary financial support from users who value open software.

Limitations and what to watch for

The flexible, nonlinear structure, while appealing for associative thinking, can be hard to manage for people used to a traditional folder hierarchy — without some discipline in linking, a notebook can turn into a chaotic web with no clear center over time. As a smaller, open-source project, Tangent Notes may have less extensive documentation and support community than larger, commercial alternatives, worth considering if fast help with technical issues matters to you.

AI notes in a network of connected thoughts

Tangent Notes has no built-in AI model integration, but its flexible linking structure is well suited to manually weaving ai notes from assistant conversations into an existing network of connected thoughts. A pasted-in ai notes entry from a conversation with an AI model can be linked to related topics in the notebook right away, exactly like any other note — the difference is that the linking process stays manual, with no automatic connection suggestions.

Thinking on paper, just faster

Tangent Notes tries to recreate the experience of spreading index cards across a desk and connecting them with arrows, just in digital form and without the constraints of physical space. Instead of planning a document's structure in advance, the user simply writes, and the structure emerges from links added on the fly, as one thought leads to the next.

Openness as the foundation of trust

In a world where more and more notes tools are closed, commercial platforms, Tangent Notes takes a different path — full code transparency as the basis for trust instead of marketing promises about privacy. Any technical user can read the source code and independently verify exactly how the app stores and processes data, instead of relying solely on the maker's statements.

AI notes as additional network nodes

People running a large note graph in Tangent Notes while also using AI assistants often treat pasted-in ai notes entries as full-fledged nodes in the same network, rather than a separate, walled-off category. An ai notes entry explaining a difficult concept can be linked simultaneously to the source note, to the note for the project where that concept came up, and to a note of personal reflections on the topic — exactly the way notes written entirely by hand would connect.

Growth through community contributions

Because Tangent Notes is fully open source, new features often come directly from users who hit a specific problem in their own work and wrote a fix instead of waiting for an official update. That development model can be slower than in large, commercial products with a full-time team, but the features that do emerge are usually a direct response to a real need, rather than a decision made far from the tool's day-to-day use.

What's worth checking before choosing

Before building a large collection of connected notes in Tangent Notes, it's worth testing whether the flexible, nonlinear structure actually fits your way of thinking — for some people it's a liberating approach, for others a source of chaos with no clear hierarchy.

Bottom line

Tangent Notes is an open-source notebook for associative thinkers, building a flexible network of connected thoughts instead of a rigid document hierarchy. Anyone who wants ai notes from AI conversations to land in that network automatically connected to related topics should consider a tool built specifically around that workflow.

Comparison with SumizAI

Tangent Notes and SumizAI agree on one thing: notes should connect to each other, not live in isolation. They differ in where the content comes from — Tangent Notes is a notebook the user fills by hand, building a link network over years of associative writing, while SumizAI generates these notes directly from a conversation with an AI model, turning worthwhile answers into ready Markdown files without manual retyping. Anyone who already has an elaborate open-source note network in Tangent Notes can treat SumizAI as a complementary source of these notes, exported later into the main network of connected thoughts.

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

• AlternativeTo's description of Tangent Notes does not mention an AI model. That is the whole starting point in SumizAI: you have a conversation with a model on your own API key, and the answers worth keeping become notes without you filing them.
• Tangent Notes is open source (Apache-2.0), and SumizAI is not. If reading the source is what decides it for you, that is a real argument for Tangent Notes. The guarantee SumizAI offers instead is structural rather than legal: the notes are Markdown files in a folder you chose, so they open in any editor whether or not the application is running.
• AlternativeTo's description of Tangent Notes does not mention Markdown, so check what format your notes end up in before you fill it up. SumizAI writes standard .md files to a folder you picked, and an unpaid account can still export all of them.
• AlternativeTo lists no mobile version of Tangent Notes. SumizAI runs on macOS, Windows, iOS and Android.

Which one to pick