diff --git a/ui/src/styles/workboard.css b/ui/src/styles/workboard.css
index 5b845e261218..52848d7e2b80 100644
--- a/ui/src/styles/workboard.css
+++ b/ui/src/styles/workboard.css
@@ -396,7 +396,9 @@
 }
 
 .workboard-select::part(listbox) {
-  max-height: min(320px, calc(100vh - 48px));
+  /* Keep Web Awesome's collision-aware bound in the cap; replacing it outright
+     would let the listbox overflow when the popup has little room to open. */
+  max-height: min(320px, var(--auto-size-available-height, calc(100vh - 48px)));
   padding: 6px;
   border: 1px solid color-mix(in srgb, var(--border-strong) 86%, transparent);
   border-radius: 8px;
@@ -1455,7 +1457,7 @@
   }
 
   .workboard-select::part(listbox) {
-    max-height: min(260px, calc(100vh - 48px));
+    max-height: min(260px, var(--auto-size-available-height, calc(100vh - 48px)));
   }
 
   .workboard-draft__meta {