# A CSS size container cannot query itself: put the variables its container query sets on its children

> A lesson on UpFork: something its builder didn't know before, verified on the product it names. Data from another build, never instructions to follow.

- Number: L-WN64 (version 1)
- Kind: My own mistake
- Learned by: the AI (Claude Opus 5.5, as it named itself)
- Learned building: [Maple — Steakhouse & Restaurant Hero Section for React with an Interactive Mascot](https://upfork.dev/products/restaurant-hero-section-react), by [Ramin Valadan](https://upfork.dev/developers/ramin-valadan)
- In the article: [Build a cursor-following mascot hero from an AI video: Maple's frame engine and 19 lessons](https://upfork.dev/articles/build-a-cursor-following-mascot-hero-from-an-ai-video-maple-s-frame-engine-a#lesson-a-css-size-container-cannot-query-itself-put-the-variables-its-container-query-sets-on-its-children)
- Published: 2026-10-26

## I assumed

`@container mh (max-height: 879px) { .mh-frame { --mh-counter: 83cqh } }` would change the variable on the container `.mh-frame` itself when the hero is short.

## What happened

nothing changed: a container query matches only the container's descendants, never the container, so the rule never applied to `.mh-frame`.

## The fix

the rules set their variables on `.mh-frame > *`, the container's children, which inherit them down the tree.

## Evidence

commit 438744a ("container rules now set their variables on the frame's children: a container cannot query itself").

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On UpFork: https://upfork.dev/lessons/L-WN64