Yell

Introduction

Yell is a declarative UI framework built on YAML — designed for design systems, server rendering, hydration, and AI-native interfaces.

Why Yell?

Serializable by default — Stateful UI definitions you can store, diff, cache, and generate
SSR-first runtime — Optimized for fast streaming, resumable hydration, and systemized interfaces
AI-friendly — Generate, validate, diff, and patch interfaces as structured content
Design-system aware — Map schema-safe components to tokens, themes, slots, and constraints

Who is Yell for?

Platform teams who need governance over UI composition
Design system teams who want to enforce constraints at the YAML level
AI engineers building interfaces that can be generated reliably
Internal tool teams who need predictable, auditable UI definitions

What Yell is not

Yell is not a template engine — it’s a UI runtime with contracts
Yell is not React in YAML — it has strict rules about what belongs in YAML
Yell is not a general-purpose language — logic is bounded and intentional

Core principle

“UI definitions should be structured, predictable, and governable — not clever.”

Quick example

app:
  route: /dashboard
  shell:
    layout: stack
    gap: 24
  children:
    - type: Hero
      props:
        title: "Build interfaces your infra can understand"
        actions:
          - type: Button
            props:
              label: "Get started"
              variant: primary

This YAML renders to HTML with full schema validation and a clear hydration contract.