A workspace for ideas worth developing

Think it through. Make it a book.

Write, research, and learn with AI beside your work. Turn questions into clear chapters, interactive explanations, and scientific papers — all in one workspace.

For independent learners, researchers, and people with something to explain.

Open the app Explore the workspace ↓

Start free — every account begins with 500 free AI credits, no card required. Reading and writing never cost anything.

Inside Cothyra · interactive example

src/07-quadric-surfaces.md

Transcript of the demonstration

Reader: Contours don't do it for me. Can you put an actual 3D surface here — one I can turn with the mouse?
read src/07-quadric-surfaces.md
Assistant: Yes — a js-render block. Plain canvas rather than a plotting library, so the chapter stays light.
edit src/07-quadric-surfaces.md — adds an interactive 3D figure — a js-render canvas block the reader can drag to turn
Assistant: It's in the chapter now — drag left and right to spin it, up and down to tilt. Say the word and I'll put a slider on the coefficient.

The saddle point

At the origin the surface $z = x^{2} - y^{2}$ is neither a maximum nor a minimum: it curves up along the $x$ axis and down along the $y$ axis, so every neighbourhood of the origin holds points both higher and lower than it.

Contour lines turn that into a family of hyperbolas. The shape is easier to believe when you can turn it over.

.cdemo__panes, .cdemo__player { display: none; } .cdemo__replay { display: none; } .cdemo__transcript { position: static; width: auto; height: auto; overflow: visible; clip-path: none; white-space: normal; padding: 1.25rem 1.5rem; } /* Without a script the phone is an empty prop, and it has no transcript of its own to fall back to. */ .cdemo-frame--phone { display: none; }

Illustrative demo: ask for a 3D surface and the assistant adds an interactive figure to the chapter. Drag the surface to explore it.

From the first question to work you can keep

01
Start with a question
Open a chapter or a LaTeX project. Give your ideas a place to grow.
02
Work it through with AI
Ask for an explanation, investigate a source, or refine a passage in context.
03
Keep what you build
Review the changes, return to your work, and export when you are ready.

For researchers, scientists, and technical writers

Your LaTeX workflow. With AI beside it.

Write papers, theses, and technical reports in a dedicated LaTeX workspace. Keep your source, compiled PDF, and assistant together as you develop the argument.

Bring your project
Start from a template, import a ZIP from Overleaf, or import a Git repository.
Write, compile, refine
Edit TeX with completions, preview the compiled PDF, and jump between source and output with SyncTeX. Build errors link back to the source.
Keep control of the result
Choose XeLaTeX, pdfLaTeX, or LuaLaTeX. Download the project source and PDF to continue your publishing workflow.

Start a LaTeX project → User Guide →

LaTeX workspace · illustrated workflow

main.tex · TeX source

\section{Diffusion}
\begin{equation}
  \frac{\partial u}{\partial t}
  = \alpha \nabla^2 u
\end{equation}

Compiled PDF

Diffusion on a bounded domain

A model for how heat spreads over time.

∂u / ∂t = α ∇²u

Already writing a book? Render equations and citations as you write, then export to LaTeX.

The difference is what you keep

Chatting with an AI

You ask, it answers, you close the tab.
Useful explanations are scattered across separate threads.
Turning answers into a manuscript takes another step.
The conversation grows longer; the draft waits elsewhere.

Working here

The chat is attached to a page you own.
Every good answer lands in the text, where it belongs.
Come back in a month and read what you built.
It compounds. Each session starts from the last one.

Self-teaching is slow because understanding evaporates faster than you can collect it. An assistant that writes into your pages instead of past them is the whole idea.

What you get

An interactive AI book

Math, tables, diagrams, code and citations render as you type. Ask the AI for a change and it lands in the chapter as a reviewable diff — one you can undo like your own typing. The editor is free, always: credits are only for AI.

src/07-quadric-surfaces.md

Transcript of the demonstration

Reader: Contours don't do it for me. Can you put an actual 3D surface here — one I can turn with the mouse?
read src/07-quadric-surfaces.md
Assistant: Yes — a js-render block. Plain canvas rather than a plotting library, so the chapter stays light.
edit src/07-quadric-surfaces.md — adds an interactive 3D figure — a js-render canvas block the reader can drag to turn
Assistant: It's in the chapter now — drag left and right to spin it, up and down to tilt. Say the word and I'll put a slider on the coefficient.

The saddle point

Contour lines turn that into a family of hyperbolas. The shape is easier to believe when you can turn it over.

Illustrative demo: ask for a 3D surface and the assistant adds an interactive figure to the chapter. Drag the surface to explore it.

Listen to your work, or talk it through, any time

Any chapter reads itself aloud, with formulas spoken the way a lecturer says them. Ask a question by voice while you listen, and the answer is read back. It all works on a phone — the same editor and chat, not a stripped-down reader.

src/03-heat-equation.md

Transcript of the demonstration

Separation of variables.
We look for solutions of the heat equation — u sub t equals alpha u sub x x — that split into a part depending only on position and a part depending only on time: u of x and t equals X of x times T of t.
Substituting, and dividing by alpha X T, gives:
T prime over alpha T equals X double prime over X equals minus lambda.
The left side depends only on t, the right only on x — so both are the same constant.

Separation of variables

We look for solutions of the heat equation $u_{t} = α u_{xx}$ that split into a part depending only on position and a part depending only on time, $u (x, t) = X (x) T (t)$ .

Substituting and dividing by $α X T$ gives

\frac{T ^{'}}{α T} = \frac{X ^{''}}{X} = - λ

The left side depends only on $t$ , the right only on $x$ , so both are the same constant.

Silent narration demo: follow the highlighted passage and see how mathematical notation becomes spoken language.

Research that cites its sources

Built-in research and fact-checking search arXiv, OpenAlex, Crossref and Wikipedia, then write cited notes and verification reports into your book — with the sources cached alongside.

The AI edits the book with you

Ask for a change and it lands in the chapter as a reviewable diff. Your keystrokes and its edits share one undo history — Ctrl+Z walks back both, even after a reload.

Chat with several models at once

Each session pins its own model — Claude, GPT, Gemini, Grok, DeepSeek and more — and keeps streaming while you read elsewhere. One turn can even fan out parallel sub-agents, each on a different model.

Made for real books

Math, diagrams, code and citations render as you type. Sandboxed Python computes and plots straight into the chapter. Export to PDF, Word or LaTeX when it's done.

See what the AI sees

Every message shows the context it carries — chapter, section, visible lines, your selection — as chips you can remove before sending. Past messages keep theirs, so you always know what was asked.

Every book is a Git repository

Commit, branch, diff and roll back — the AI works the repo with you, and every write asks first. Push to a GitHub repo under your own account; it can even create one for you.

All the features, in the User Guide →

On a phone, it is the same app

Read a chapter, ask a question, or keep writing from your phone. Switch between your document and the assistant, and pick up your work across devices.

Quadric Surfaces

Start free. Pay as you go beyond that.

Every account starts with 500 free AI credits — no subscription, no card. When you need more, buy a credit pack and spend it on AI calls. Your library, your reading, and your writing are always free.

Free to start

500 credits

one-time signup grant · no card required

Chat, edit, research and listen — your signup credits work with nearly every model and feature. Only a handful of premium frontier models require purchased credits.

Starter

$10 USD

1,000 credits

$10 of credits. Try it out.

Regular

Best value

$20 USD

2,200 credits

$20 of credits + $2 bonus. The everyday pack.

Power

$50 USD

5,750 credits

$50 of credits + $7.50 bonus. For heavy editing weeks.

Get started

Pay only for what you use — no subscription, no minimums.

A few things to know

What can I do for free?

Reading and writing are free. New accounts receive 500 one-time AI credits with no card required. AI usage consumes credits; a few premium models require purchased credits.

Can I choose the AI model?

Yes. Choose a model for each conversation and use different models across sessions. Usage is charged at the selected model’s rates.

Can I take my work with me?

Export books to PDF, Word, or LaTeX. For LaTeX projects, download the source project and compiled PDF. You can also download your account data.

Think it through. Make it a book.

Transcript of the demonstration

The saddle point

From the first question to work you can keep

Start with a question

Work it through with AI

Keep what you build

Your LaTeX workflow. With AI beside it.

Bring your project

Write, compile, refine

Keep control of the result

Diffusion on a bounded domain

The difference is what you keep

Chatting with an AI

Working here

What you get

An interactive AI book

Transcript of the demonstration

The saddle point

Listen to your work, or talk it through, any time

Transcript of the demonstration

Separation of variables

Research that cites its sources

The AI edits the book with you

Chat with several models at once

Made for real books

See what the AI sees

Every book is a Git repository

On a phone, it is the same app

Start free. Pay as you go beyond that.

Free to start

Starter

Regular

Power

A few things to know