YemenOpenSource · pull · Aug 11, 2026 · Aug 10, 2026
diff --git a/app/api/compare/route.ts b/app/api/compare/route.ts
@@ -77,12 +77,12 @@ function calculateWinner(users: ComparedUserResult[]): {
   winner?: {
     username: string;
     finalScoreDifference: number;
-    percentageDifference: number;
+    percentageDifference: number | null;
   };
   languageWinner?: {
     username: string;
     finalScoreDifference: number;
-    percentageDifference: number;
+    percentageDifference: number | null;
     selectedLanguages: string[];
   };
 } {
@@ -95,28 +95,29 @@ function calculateWinner(users: ComparedUserResult[]): {
   const overallLoser =
     overallWinner.username === userA.username ? userB : userA;
   const overallDifference = Math.abs(userA.finalScore - userB.finalScore);
-  const overallPercentage =
-    overallLoser.finalScore > 0
-      ? (overallDifference / overallLoser.finalScore) * 100
-      : 0;
+  const overallPercentage = calculatePercentageDifference(
+    overallDifference,
+    overallLoser.finalScore,
+  );
 
   const result: {
     winner: {
       username: string;
       finalScoreDifference: number;
-      percentageDifference: number;
+      percentageDifference: number | null;
     };
     languageWinner?: {
       username: string;
       finalScoreDifference: number;
-      percentageDifference: number;
+      percentageDifference: number | null;
       selectedLanguages: string[];
     };
   } = {
     winner: {
       username: overallWinner.username,
       finalScoreDifference: Math.round(overallDifference),
-      percentageDifference: Math.round(overallPercentage),
+      percentageDifference:
+        overallPercentage === null ? null : Math.round(overallPercentage),
     },
   };
 
@@ -132,22 +133,34 @@ function calculateWinner(users: ComparedUserResult[]): {
     const languageDifference = Math.abs(
       winnerLanguageScores.finalScore - loserLanguageScores.finalScore,
     );
-    const languagePercentage =
-      loserLanguageScores.finalScore > 0
-        ? (languageDifference / loserLanguageScores.finalScore) * 100
-        : 0;
+    const languagePercentage = calculatePercentageDifference(
+      languageDifference,
+      loserLanguageScores.finalScore,
+    );
 
     result.languageWinner = {
       username: languageWinner.username,
       finalScoreDifference: Math.round(languageDifference),
-      percentageDifference: Math.round(languagePercentage),
+      percentageDifference:
+        languagePercentage === null ? null : Math.round(languagePercentage),
       selectedLanguages: winnerLanguageScores.selectedLanguages,
     };
   }
 
   return result;
 }
 
+function calculatePercentageDifference(
+  difference: number,
+  baseline: number,
+): number | null {
+  if (baseline <= 0) {
+    return difference > 0 ? null : 0;
+  }
+
+  return (difference / baseline) * 100;
+}
+
 function createComparisonInsights(
   users: ComparedUserResult[],
   locale: Locale,

diff --git a/components/home-page-client.tsx b/components/home-page-client.tsx
@@ -26,7 +26,7 @@ type ComparisonData = {
   languageWinner?: {
     username: string;
     finalScoreDifference: number;
-    percentageDifference: number;
+    percentageDifference: number | null;
     selectedLanguages: string[];
   };
   insights?: CompareInsights;

diff --git a/components/result-dashboard.tsx b/components/result-dashboard.tsx
@@ -21,7 +21,7 @@ type Props = {
   languageWinner?: {
     username: string;
     finalScoreDifference: number;
-    percentageDifference: number;
+    percentageDifference: number | null;
     selectedLanguages: string[];
   };
   insights?: CompareInsights;
@@ -42,6 +42,17 @@ function getGithubProfileUrl(username: string): string {
   return `https://github.com/${username}`;
 }
 
+function getPercentageDifference(
+  winnerScore: number,
+  loserScore: number,
+): number | null {
+  if (loserScore <= 0) {
+    return winnerScore > loserScore ? null : 0;
+  }
+
+  return Math.round(((winnerScore - loserScore) / loserScore) * 100);
+}
+
 export function ResultDashboard({
   user1,
   user2,
@@ -88,13 +99,20 @@ export function ResultDashboard({
         : winnerFromScores;
   const loserUser =
     overallWinnerUser === user1 ? user2 : overallWinnerUser === user2 ? user1 : null;
-  const winnerDiffPct =
-    overallWinnerUser && loserUser && loserUser.finalScore > 0
-      ? Math.round(
-          ((overallWinnerUser.finalScore - loserUser.finalScore) / loserUser.finalScore) *
-            100,
-        )
+  const winnerDiffPct = winner
+    ? winner.percentageDifference
+    : overallWinnerUser && loserUser
+      ? getPercentageDifference(overallWinnerUser.finalScore, loserUser.finalScore)
       : 0;
+  const winnerDiffPoints =
+    winner?.finalScoreDifference ??
+    (overallWinnerUser && loserUser
+      ? Math.round(Math.abs(overallWinnerUser.finalScore - loserUser.finalScore))
+      : 0);
+  const winnerLeadValue =
+    winnerDiffPct === null
+      ? t("results.pointsLead", { points: winnerDiffPoints })
+      : `${winnerDiffPct}%`;
 
   const handleCopy = async () => {
     try {
@@ -210,7 +228,7 @@ export function ResultDashboard({
     );
   };
 
-  const renderSignalStats = (user: UserResult) => {
+  const renderSignalStats = (user: UserResult, idx: number) => {
     if (!user.signals) return null;
 
     const signalEntries: Array<{ label: string; value: string | number }> = [
@@ -258,7 +276,7 @@ export function ResultDashboard({
     ];
 
     return (
-      <Card key={`signal-${user.username}`}>
+      <Card key={`signal-${user.username}-${idx}`}>
         <CardHeader className="pb-3">
           <CardTitle className="flex items-center gap-2 text-base">
             <Avatar
@@ -320,7 +338,7 @@ export function ResultDashboard({
                 </div>
                 <div className="text-right">
                   <p className="text-sm text-muted-foreground">{t("banner.leadby")}</p>
-                  <p className="text-2xl font-bold text-primary">{winnerDiffPct}%</p>
+                  <p className="text-2xl font-bold text-primary">{winnerLeadValue}</p>
                 </div>
               </>
             ) : (
@@ -377,7 +395,12 @@ export function ResultDashboard({
               {t("language.focus")}: {languageWinner.selectedLanguages.join(", ")}
             </p>
             <p className="mt-1 text-xs text-muted-foreground">
-              {t("banner.leadby")} {languageWinner.percentageDifference}%
+              {t("banner.leadby")}{" "}
+              {languageWinner.percentageDifference === null
+                ? t("results.pointsLead", {
+                    points: languageWinner.finalScoreDifference,
+                  })
+                : `${languageWinner.percentageDifference}%`}
             </p>
             <p className="mt-2 text-xs text-muted-foreground">{t("language.winnerNote")}</p>
           </CardContent>
@@ -449,8 +472,8 @@ export function ResultDashboard({
           {t("signals.title")}
         </summary>
         <div className="mt-4 grid gap-4 lg:grid-cols-2">
-          {renderSignalStats(user1)}
-          {renderSignalStats(user2)}
+          {renderSignalStats(user1, 1)}
+          {renderSignalStats(user2, 2)}
         </div>
       </details>
 

diff --git a/components/top-list.tsx b/components/top-list.tsx
@@ -206,8 +206,8 @@ export function TopList({ userResults, selectedLanguages = [] }: Props) {
 
   return (
     <div className="grid gap-6 md:grid-cols-2">
-      {userResults.map((user) => (
-        <Card key={`top-${user.username}`}>
+      {userResults.map((user, idx) => (
+        <Card key={`top-${user.username}-${idx}`}>
           <CardHeader>
             <CardTitle className="text-lg">
               {t("topwork.titleForUser", { username: user.name || user.username })}

diff --git a/locales/ar.json b/locales/ar.json
@@ -170,6 +170,7 @@
   "results.copied": "تم النسخ!",
   "results.copy": "نسخ النتيجة",
   "results.copyAria": "نسخ نتائج المقارنة إلى الحافظة",
+  "results.pointsLead": "+{points} نقطة",
   "score.rawLabel": "الدرجة الخام: {value}",
   "results.scoreVersion": "إصدار التقييم",
   "section.language": "النتيجة اللغوية",

diff --git a/locales/en.json b/locales/en.json
@@ -170,6 +170,7 @@
   "results.copied": "Copied!",
   "results.copy": "Copy Result",
   "results.copyAria": "Copy comparison results to clipboard",
+  "results.pointsLead": "+{points} points",
   "score.rawLabel": "Raw: {value}",
   "results.scoreVersion": "Score version",
   "section.language": "Language-focused Score",

diff --git a/test/api/compare.route.test.ts b/test/api/compare.route.test.ts
@@ -51,7 +51,26 @@ function makeUser(login: string, name: string) {
   };
 }
 
-function makeScore(finalScore: number) {
+function makeLanguageScores(finalScore: number) {
+  return {
+    selectedLanguages: ["TypeScript"],
+    repoScore: 0,
+    prScore: 0,
+    contributionScore: 0,
+    finalScore,
+    normalizedRepoScore: 0,
+    normalizedPRScore: 0,
+    normalizedContributionScore: 0,
+    normalizedFinalScore: 0,
+    topRepos: [],
+    topPullRequests: [],
+  };
+}
+
+function makeScore(
+  finalScore: number,
+  languageScores?: ReturnType<typeof makeLanguageScores>,
+) {
   return {
     repoScore: 10,
     prScore: 20,
@@ -64,7 +83,7 @@ function makeScore(finalScore: number) {
     topRepos: [],
     topPullRequests: [],
     topCommunityContributions: [],
-    languageScores: undefined,
+    languageScores,
     signals: {
       reposAnalyzed: 1,
       pullRequestsAnalyzed: 1,
@@ -188,6 +207,77 @@ describe("GET /api/compare", () => {
     expect(body.winner?.username).toBe("user-a");
   });
 
+  test("returns null percentage when the losing final score is zero", async () => {
+    mocks.getUserData.mockResolvedValueOnce({
+      data: makeUser("user-a", "User A"),
+      metrics: { duration: 0, errors: [] },
+    });
+    mocks.getUserData.mockResolvedValueOnce({
+      data: makeUser("user-b", "User B"),
+      metrics: { duration: 0, errors: [] },
+    });
+
+    mocks.calculateUserScore.mockReturnValueOnce(makeScore(20));
+    mocks.calculateUserScore.mockReturnValueOnce(makeScore(0));
+
+    const response = await GET(
+      makeRequest({
+        username: ["user-a", "user-b"],
+      }),
+    );
+    const body = (await response.json()) as {
+      winner?: {
+        username: string;
+        finalScoreDifference: number;
+        percentageDifference: number | null;
+      };
+    };
+
+    expect(response.status).toBe(200);
+    expect(body.winner).toEqual({
+      username: "user-a",
+      finalScoreDifference: 20,
+      percentageDifference: null,
+    });
+  });
+
+  test("returns null language winner percentage when language loser score is zero", async () => {
+    mocks.getUserData.mockResolvedValueOnce({
+      data: makeUser("user-a", "User A"),
+      metrics: { duration: 0, errors: [] },
+    });
+    mocks.getUserData.mockResolvedValueOnce({
+      data: makeUser("user-b", "User B"),
+      metrics: { duration: 0, errors: [] },
+    });
+
+    mocks.calculateUserScore.mockReturnValueOnce(makeScore(20, makeLanguageScores(12)));
+    mocks.calculateUserScore.mockReturnValueOnce(makeScore(10, makeLanguageScores(0)));
+
+    const response = await GET(
+      makeRequest({
+        username: ["user-a", "user-b"],
+        selectedLanguage: "TypeScript",
+      }),
+    );
+    const body = (await response.json()) as {
+      languageWinner?: {
+        username: string;
+        finalScoreDifference: number;
+        percentageDifference: number | null;
+        selectedLanguages: string[];
+      };
+    };
+
+    expect(response.status).toBe(200);
+    expect(body.languageWinner).toEqual({
+      username: "user-a",
+      finalScoreDifference: 12,
+      percentageDifference: null,
+      selectedLanguages: ["TypeScript"],
+    });
+  });
+
   test("returns targeted username for not-found errors", async () => {
     mocks.getUserData.mockRejectedValueOnce(new Error("User not found"));
 

diff --git a/types/api-response.ts b/types/api-response.ts
@@ -3,7 +3,7 @@ import { UserResult } from "./user-result";
 export type CompareWinner = {
   username: string;
   finalScoreDifference: number;
-  percentageDifference: number;
+  percentageDifference: number | null;
 };
 
 export type SafeApiError = {
@@ -48,7 +48,7 @@ export type ApiResponse = {
   languageWinner?: {
     username: string;
     finalScoreDifference: number;
-    percentageDifference: number;
+    percentageDifference: number | null;
     selectedLanguages: string[];
   };
   insights?: CompareInsights;