# Convergence Principle

> The Convergence Principle of the ZIC standard holds that AI agents and screen readers are functionally equivalent at the structural level of a document.

**Real.** This entry is about something real, written from outside the CharliVerse.

The **Convergence Principle** of the [Zero Information Casualty](https://charli.info/charlipedia/zero-information-casualty/) standard holds that agents and screen readers are functionally equivalent at the structural level. Both navigate by landmarks, headings and links; both need link text that describes its destination, heading hierarchy that reflects content, and reading order that matches the page; and neither can interpret meaning carried only by colour or position.

The convergence is not incidental. Information held only in the visual layer is hidden from a large and growing share of all information consumers, and as agents become primary readers alongside people, "the case for visual-only encoding collapses entirely." It is the web-page form of the convergence the [Tyrer Framework](https://charli.info/charlipedia/tyrer-framework/) describes under [generative accessibility](https://charli.info/charlipedia/generative-accessibility/).

## Where it stops

"The equivalence is real, and it is local." ZIC's requirements are the union of two overlapping sets, neither inside the other. A sent agent needs delivery, admission, a certificate that validates and a robots policy that doesn't fail closed, all invisible to a screen reader user, who arrives inside the building. A human reader needs visible focus, keyboard operation, skip links, text scaling and contrast, which no agent has ever needed. The overlap is big enough that a publisher building for machines removes most barriers facing blind people, "and it needs no apology." But "neither reader sees all of the terrain."

## Behind the scenes

A real idea, from [Zero Information Casualty v1.7](https://carrados.com/papers/zic-design-standard/), the design standard by Charli-Jo Tyrer and Claude, §1.3 and §1.13. This entry summarises it; the standard is the authority.