Three reading surfaces, one substrate. A revolution in reading.
Folio is the reading engine at the heart of kaOS. It renders any book from anywhere — EPUB, PDF, MOBI, MDX — in 31 languages, with typographic craft the web has never managed. Beneath it, the MDX Folio makes books intelligence-first: typed content streams an agent can read, multimedia that is native to the page, and every book its own reader. This is the forty-year craft of reading systems, shown.
THREE SURFACES · ONE SUBSTRATE · FREE TO READ
The heart of any reading system is its renderer.
Most reading apps hand the book to a web view and hope. kaOS does not. The kaOS EPUB renderer is a real layout engine — measurement, line-breaking, pagination, and typography all owned by us, all deterministic, all language-agnostic. It renders EPUB 2, EPUB 3, KF8, PDF, and plain text through one pipeline. It serves 31 languages, including bidirectional and vertical scripts. It justifies with Knuth-Plass. It measures with Pretext. This is what a reading system looks like when someone cared.
A paginated two-column spread in the kaOS Folio reader. Knuth-Plass justification, real drop caps, footnotes at the foot of the page.
A reading system for the intelligence-first age.
The EPUB renderer is the craft. The MDX Folio is the future. Beneath the rendered page, every Folio book is a stream of typed content descriptors — paragraph, heading, footnote, figure, audio, ai-script — that an agent can read as structure. The book becomes addressable. A passage can be cited by its descriptor ID. A chapter can carry its own reading instructions. Multimedia is native, not bolted on. Every book generates its own reader. This is what books become when the reading system was designed for intelligence to read them too.
<ai-script kind="summarise" target="self"> When the reader asks for a summary of this passage, return the three-sentence gist and cite the paragraph by its descriptor ID. Do not paraphrase the citation. </ai-script> <paragraph id="p-0421"> The whole earth is a living icon of the face of God. ... </paragraph>
The book tells the agent how it wants to be read. The agent never guesses. The reader sees the same page a human would — the ai-script is invisible unless asked for.
The powerful one. Canvas2D. Pretext. 31 descriptors.
Sovereign Folio is the substrate the other surfaces stand on. It renders to a 2D canvas — not to the DOM — so the page on the screen is bit-identical to the page in the export. No browser reflow, no font-substitution drift, no “close enough.” It measures every glyph before layout, so line breaks are deterministic. It speaks 31 content descriptor kinds, so every piece of a book has a type an agent can address. And it runs on your machine, local-first, sovereign. Your library is yours.
Canvas2D rendering. Real facing pages, gutter, running heads, drop cap sinking into the text block. Bit-identical to the export.
A multimedia book is not a website with a reader bolted on.
Because a Folio book is a typed content stream, the renderer for that book is generated from the stream itself. A book with audio narration gets a play-bar bound to paragraph positions. A book with video gets inline figures that honor the page. A book with interactive 3D models gets a canvas reader. A book with ai-script blocks gets an agent reader. No two books need look the same — and every one of them is still, recognisably, a book.
Audio narration bound to paragraphs. Inline video as a figure. The book is the reader — no widget layer.
One substrate, three doors.
The same reading engine reaches you three ways. Pick the door that fits the moment — the book is the same, the page is the same, your place is the same.