diff --git a/backend/src/main/resources/content/platform/frontend-template/rules.md b/backend/src/main/resources/content/platform/frontend-template/rules.md
index bd08a19..948abda 100644
--- a/backend/src/main/resources/content/platform/frontend-template/rules.md
+++ b/backend/src/main/resources/content/platform/frontend-template/rules.md
@@ -74,3 +74,10 @@ content frame, never in `.header`. Add/Edit forms are **slide-in panels**, not c
 Locked structure: `.filter-sidebar` · `.content-frame` · `.table-card` border · active-filter chips ·
 `Pagination` at top-of-table. New page → **copy** TablePage/TemplatePage first; existing page → verify
 it conforms before building on it (many drifted).
+
+**The Filters sidebar header does NOT recolor when filters are active.** The active state is signalled
+by the count pill and the removable active-filter chips above the table — not by tinting the header
+bar blue. (The `bar-filters-active` class binding is kept for structural parity but its CSS is a
+no-op.) Every real SPA already avoids the tint — devices/fleet never bound the class, incident neutralised
+its CSS (set it to the same `#eef2f7` as the default bar). The blue-header (`#dbeafe`) lived **only**
+in the template. Do not re-add the header tint when copying a page.