From 73a8dba82a2e175c9d9886d4aa5ea3a44604cd06 Mon Sep 17 00:00:00 2001
From: Max Ghenis <mghenis@gmail.com>
Date: Fri, 8 May 2026 19:46:53 -0500
Subject: [PATCH] Fall back to Main when sensitivity slice is empty for the
 active country

Binary only on the UK leaderboard rendered an empty list because UK
has zero binary outputs. The leaderboard now falls back to the Main
view (with a notice) for any single-country selection that has no
rows under the active sensitivity slice, mirroring the existing
Global+Binary behaviour. Sensitivity buttons that would yield no
rows for the current selectedView are disabled with a tooltip
explaining which country to switch to.

- Adds viewSupportsSelected(rows, view, selectedView) to lib/sensitivity.
- ModelLeaderboard's fallback flag is now sensitivityUnsupportedForView
  (was globalUnsupportedForView) and applies to US, UK, and Global.
- Disable + tooltip copy now name the missing country instead of
  always referring to "the Global view".
---
 app/src/components/ModelLeaderboard.tsx | 67 ++++++++++++++++---------
 app/src/lib/sensitivity.ts              | 14 ++++++
 2 files changed, 56 insertions(+), 25 deletions(-)

diff --git a/app/src/components/ModelLeaderboard.tsx b/app/src/components/ModelLeaderboard.tsx
index cf3e364..571063a 100644
--- a/app/src/components/ModelLeaderboard.tsx
+++ b/app/src/components/ModelLeaderboard.tsx
@@ -17,7 +17,7 @@ import {
   SENSITIVITY_VIEWS,
   buildAllRows,
   modelScoresForView,
-  viewSupportsGlobal,
+  viewSupportsSelected,
   type SensitivityViewId,
 } from "../lib/sensitivity";
 import {
@@ -122,18 +122,18 @@ export default function ModelLeaderboard({
 
   const allRows = useMemo(() => buildAllRows(dashboard), [dashboard]);
 
-  // Some sensitivity slices have no rows in one country (e.g. "Binary only"
-  // has zero UK rows). In that case the global view cannot be a true
-  // cross-country score; fall back to the canonical Main view so the global
-  // tab still has a defensible ranking and surface a notice on the leaderboard.
-  const globalUnsupportedForView = useMemo(
+  // Some sensitivity slices have no rows in the selected country (e.g.
+  // "Binary only" has zero UK rows; "Binary only" on Global has zero UK
+  // rows so the global view cannot be a true cross-country score). In that
+  // case we fall back to the canonical Main view so the leaderboard still
+  // has a defensible ranking and surface a notice explaining why.
+  const sensitivityUnsupportedForView = useMemo(
     () =>
-      isGlobal &&
       sensitivityView !== "main" &&
-      !viewSupportsGlobal(allRows, sensitivityView),
-    [allRows, isGlobal, sensitivityView],
+      !viewSupportsSelected(allRows, sensitivityView, selectedView),
+    [allRows, selectedView, sensitivityView],
   );
-  const effectiveView: SensitivityViewId = globalUnsupportedForView
+  const effectiveView: SensitivityViewId = sensitivityUnsupportedForView
     ? "main"
     : sensitivityView;
 
@@ -242,27 +242,34 @@ export default function ModelLeaderboard({
         >
           {SENSITIVITY_VIEWS.map((view) => {
             const isActive = sensitivityView === view.id;
-            const disabledForGlobal =
-              isGlobal &&
-              view.id !== "main" &&
-              !viewSupportsGlobal(allRows, view.id);
+            const supported =
+              view.id === "main" ||
+              viewSupportsSelected(allRows, view.id, selectedView);
+            const disabled = !supported;
+            const disabledTitleSuffix = isGlobal
+              ? " (not available for the Global view; switch to US or UK)"
+              : selectedView === "uk"
+                ? " (no UK rows under this slice; switch to US or Global)"
+                : selectedView === "us"
+                  ? " (no US rows under this slice; switch to UK or Global)"
+                  : "";
             return (
               <button
                 key={view.id}
                 type="button"
-                disabled={disabledForGlobal}
+                disabled={disabled}
                 onClick={() => setSensitivityView(view.id)}
-                aria-pressed={isActive && !disabledForGlobal}
+                aria-pressed={isActive && !disabled}
                 className={`rounded-full px-3 py-1 text-[11px] font-medium transition-colors ${
-                  isActive && !disabledForGlobal
+                  isActive && !disabled
                     ? "bg-primary text-void"
-                    : disabledForGlobal
+                    : disabled
                       ? "cursor-not-allowed text-text-muted opacity-60"
                       : "text-text-secondary hover:text-text"
                 }`}
                 title={
-                  disabledForGlobal
-                    ? `${view.description} (not available for the Global view; switch to US or UK)`
+                  disabled
+                    ? `${view.description}${disabledTitleSuffix}`
                     : view.description
                 }
               >
@@ -275,16 +282,26 @@ export default function ModelLeaderboard({
           {activeView.description}
         </span>
       </div>
-      {globalUnsupportedForView && (
+      {sensitivityUnsupportedForView && (
         <p
           role="note"
           className="mt-3 text-[11px] text-text-muted animate-fade-up"
           style={{ animationDelay: "220ms" }}
         >
-          The &ldquo;{activeView.label}&rdquo; slice has no rows in at least
-          one country, so the global ranking falls back to the Main view.
-          Switch to United States or United Kingdom to see this slice on a
-          single country.
+          The &ldquo;{
+            SENSITIVITY_VIEWS.find((v) => v.id === sensitivityView)?.label ??
+              sensitivityView
+          }&rdquo; slice has no rows in {
+            isGlobal
+              ? "at least one country"
+              : selectedView === "uk"
+                ? "the UK"
+                : "the US"
+          }, so the leaderboard falls back to the Main view. {
+            isGlobal
+              ? "Switch to United States or United Kingdom to see this slice on a single country."
+              : "Switch to the other country to see this slice."
+          }
         </p>
       )}
 
diff --git a/app/src/lib/sensitivity.ts b/app/src/lib/sensitivity.ts
index acfac08..2b3a613 100644
--- a/app/src/lib/sensitivity.ts
+++ b/app/src/lib/sensitivity.ts
@@ -187,6 +187,20 @@ export function viewSupportsGlobal(
   return GLOBAL_REQUIRED_COUNTRIES.every((c) => present.has(c));
 }
 
+/** Returns true if the active sensitivity slice has rows under the selected view. */
+export function viewSupportsSelected(
+  rows: ScoreRow[],
+  view: SensitivityViewId,
+  selectedView: ViewKey,
+): boolean {
+  if (selectedView === "global") return viewSupportsGlobal(rows, view);
+  const filtered = filterRows(rows, view);
+  for (const row of filtered) {
+    if (row.country === selectedView) return true;
+  }
+  return false;
+}
+
 export function modelScoresForView(
   rows: ScoreRow[],
   view: SensitivityViewId,