What problem does it solve? Unit tests and successful compilation prove UI logic works, but they cannot prove a screen actually renders correctly — clipped containers, overflowing text, and invisible controls slip through green test suites. This Skill closes that gap when building a UI block in the mismAgent build flow. ## Core Features & Use Cases - Presenter/view split: Separates every UI decision into a plain, unit-testable state-holder/presenter while the view only renders observable state and forwards events. - Mandatory render-check: Requires either an automated smoke/screenshot test from the side's profile gate or a recorded run-the-app check via the run-app-smoke skill, with evidence stored in render-proof/<block-id>/. - Render checklist: Enforces explicit sizing, intentional overflow handling, contrast/visibility, empty/error/loading state rendering, and observable-state recomposition. - Use Case: When the mismAgent worker loads a block with type = ui, this Skill guides TDD on the presenter from tests_nl, then verifies the screen renders correctly before reporting PUBLIC_API and the render-check result back to the worker. ## Quick Start Ask the worker to realize the ui block defined in the building-block manifest, splitting it into a tested presenter and thin view with a recorded render check.
