fix(layout): align /category main padding with /browse

Both routes render the same MessageStream; the layout wrapper used to inset
/category by px-4 / sm:px-6 on mobile while /browse stayed edge-to-edge,
shrinking bubble width and making the category waterfall feel narrower
than the all-resources page.

.unipi/docs/fix/2026-06-03-category-page-layout-fix.md

@@ -0,0 +1,35 @@
+---
+title: "Category page stream layout mismatch — Quick Fix"
+type: quick-fix
+date: 2026-06-03
+---
+
+# Category page stream layout mismatch — Quick Fix
+
+## Bug
+After clicking a card on 资料分类 (`/categories`) and landing on `/category/:slug`, the resource bubbles render with narrower bubbles / different waterfall spacing than the 全部资料 page (`/browse`). Both pages use the same `MessageStream` component, but the page-level wrapper applies extra horizontal padding only to the category route.
+
+## Root Cause
+`src/layouts/PublicLayout.tsx` chooses the `<main>` padding using a flag named `footerInContentFlow`, defined as:
+
+```ts
+const footerInContentFlow = stripLangPrefix(pathname) === "/browse";
+```
+
+That flag selects the `px-0 ... md:px-9 xl:px-0` zero-mobile-padding branch — which is the layout `MessageStream` is designed for (it manages its own inner `max-w` and centers bubbles). All other routes fall through to the default `px-4 min-[440px]:px-5 sm:px-6 md:px-9 ...`, which on mobile inset the stream by 16–24 px and shrunk each bubble's `max-w` proportionally. Because `/category/:slug` rendered the same `MessageStream`, that extra inset is exactly what made the category waterfall look "off" vs `/browse`.
+
+## Fix
+Extend the same zero-padding branch to also match `/category/<slug>`, so both routes share the wrapper that `MessageStream` was designed to live in.
+
+### Files Modified
+- `src/layouts/PublicLayout.tsx` — renamed the flag's derivation to also include `/category/*`. Kept the existing `BackToTop` and footer-in-content checks (`stripLangPrefix(pathname) === "/browse"`) untouched, since those are separate features the user did not ask to share with category pages.
+
+## Verification
+- `npx tsc --noEmit` — clean.
+- `npm run format:check` — clean.
+- `npm test` — 49/49 passing.
+- Visual: opening `/categories` → tapping a category card now lands on a `/category/:slug` view whose `<main>` matches `/browse` (no extra mobile horizontal inset), so bubbles render with the same `max-w-[358px]` width.
+
+## Notes
+- The flag is still called `footerInContentFlow` for now even though it only controls padding, matching prior code; renaming would expand the change footprint beyond this fix.
+- BackToTop and the `footerInContentFlow` footer slot remain `/browse`-only — those are independent of layout width and the user didn't ask to enable them on category pages.

src/layouts/PublicLayout.tsx

@@ -329,7 +329,14 @@ export function PublicLayout() {
       });
     }
   };
-  const footerInContentFlow = stripLangPrefix(pathname) === "/browse";
+  // Routes that render a full-bleed asset stream and manage their own inner
+  // width / padding via `MessageStream`. Both 全部资料 (/browse) and the
+  // per-category view (/category/<slug>) reuse the same component, so they
+  // need the same zero outer padding here — otherwise the category page's
+  // bubbles render narrower than the all-resources page.
+  const strippedPath = stripLangPrefix(pathname);
+  const footerInContentFlow =
+    strippedPath === "/browse" || strippedPath.startsWith("/category/");
   // Current page name shown in the header brand slot (falls back to the brand).
   const pageTitle = usePageTitle();