Provider-first, reviewed fallback
WallCab first asks an external provider for the day’s word or concept. It validates candidates independently for length, language, duplication risk, source availability, and composition fit. The accepted result and its provenance are cached for one UTC day. A 240-item reviewed catalog exists only so a provider outage never leaves the Shortcut without a safe image.
The configurator and `/api/wallpaper/status` identify the resolved category and show whether today’s content is external or fallback. The image API provides the same information in `X-WallCab-Content-Mode` and `X-WallCab-Content-Provider`.
Image selection
The five daily photography themes use Openverse searches restricted to CC0 and public-domain material with mature content disabled. WallCab verifies the final image host, media type, dimensions, byte size, and attribution metadata before rendering. A bundled procedural composition is the last resort for each photo theme.
AMOLED, Minimal, Abstract, Gradient, Black & White, and Grid are fixed SVG compositions made by WallCab and released under CC0 1.0. Their background art remains constant while the lesson changes each UTC day. Every generated image identifies the selected study in its footer credit.
Licensing boundary
WallCab source code is available under the MIT License. Lesson text, quotations, photographs, provider data, typefaces, and other third-party material retain their original licenses. The repository’s license does not relicense those works.
A user-supplied background is not part of WallCab’s source catalog and is not relicensed. Uploaders must own the image or have permission to use it. WallCab labels the generated wallpaper as “User upload” without claiming a third-party license.