diff --git a/services/web-ui/src/css/components/field-group.css b/services/web-ui/src/css/components/field-group.css
new file mode 100644
index 0000000..5d4443b
--- /dev/null
+++ b/services/web-ui/src/css/components/field-group.css
@@ -0,0 +1,53 @@
+/* field-group.css ─ titled section with optional inner tabs.
+ * Generalized from the codec-block pattern in recorders.html. */
+
+.wd-field-group {
+  border: 1px solid var(--border-faint);
+  border-radius: 6px;
+  background: var(--bg-panel);
+  overflow: hidden;
+}
+
+.wd-field-group-header {
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+  height: 36px;
+  padding: 0 14px;
+  background: var(--bg-surface);
+  border-bottom: 1px solid var(--border-faint);
+}
+.wd-field-group-title {
+  font: 600 11px/1 var(--font);
+  letter-spacing: 0.14em;
+  text-transform: uppercase;
+  color: var(--text-secondary);
+}
+
+.wd-tabs {
+  display: flex;
+  height: 32px;
+  background: var(--bg-deep);
+  border-bottom: 1px solid var(--border-faint);
+}
+.wd-tab {
+  flex: 1;
+  background: transparent;
+  border: 0;
+  border-bottom: 2px solid transparent;
+  font: 500 11px/1 var(--font);
+  letter-spacing: 0.08em;
+  text-transform: uppercase;
+  color: var(--text-tertiary);
+  cursor: pointer;
+  transition: color 120ms cubic-bezier(0.25, 1, 0.5, 1),
+              border-color 120ms cubic-bezier(0.25, 1, 0.5, 1);
+}
+.wd-tab:hover { color: var(--text-secondary); }
+.wd-tab.is-active {
+  color: var(--accent);
+  border-bottom-color: var(--accent);
+}
+
+.wd-tab-panel { display: none; padding: 14px; }
+.wd-tab-panel.is-active { display: block; }