diff --git a/prisma/migrations/20251213133000_add_github_username/migration.sql b/prisma/migrations/20251213133000_add_github_username/migration.sql
new file mode 100644
index 00000000..e69de29b
diff --git a/prisma/schema.prisma b/prisma/schema.prisma
index f741ce08..3b7c53b1 100644
--- a/prisma/schema.prisma
+++ b/prisma/schema.prisma
@@ -20,18 +20,19 @@ enum UserRole {
 }
 
 model User {
-  id            String    @id @default(cuid())
-  email         String    @unique
-  username      String    @unique
-  name          String?
-  password      String?   // For credentials auth
-  avatar        String?
-  role          UserRole  @default(USER)
-  locale        String    @default("en")
-  verified      Boolean   @default(false)
-  emailVerified DateTime?
-  createdAt     DateTime  @default(now())
-  updatedAt     DateTime  @updatedAt
+  id             String    @id @default(cuid())
+  email          String    @unique
+  username       String    @unique
+  name           String?
+  password       String?   // For credentials auth
+  avatar         String?
+  role           UserRole  @default(USER)
+  locale         String    @default("en")
+  verified       Boolean   @default(false)
+  emailVerified  DateTime?
+  githubUsername String?   // Immutable GitHub username for contributor attribution
+  createdAt      DateTime  @default(now())
+  updatedAt      DateTime  @updatedAt
 
   // Relations
   prompts        Prompt[]         @relation("PromptAuthor")
diff --git a/src/app/prompts.csv/route.ts b/src/app/prompts.csv/route.ts
index fba0dadc..dcfdfdb9 100644
--- a/src/app/prompts.csv/route.ts
+++ b/src/app/prompts.csv/route.ts
@@ -29,7 +29,8 @@ export async function GET() {
         },
         author: {
           select: {
-            username: true,
+            email: true,
+            githubUsername: true,
           },
         },
       },
@@ -42,7 +43,9 @@ export async function GET() {
       const promptContent = escapeCSVField(prompt.content);
       const forDevs = prompt.category?.slug === "coding" ? "TRUE" : "FALSE";
       const type = prompt.type;
-      const contributor = escapeCSVField(prompt.author.username);
+      // Use githubUsername for GitHub users, email for others (Google, credentials)
+      // This prevents impersonation since these identifiers are immutable
+      const contributor = escapeCSVField(prompt.author.githubUsername || prompt.author.email);
       
       return [act, promptContent, forDevs, type, contributor].join(",");
     });
diff --git a/src/lib/auth/index.ts b/src/lib/auth/index.ts
index c6dc4b47..94ca4788 100644
--- a/src/lib/auth/index.ts
+++ b/src/lib/auth/index.ts
@@ -41,9 +41,11 @@ function CustomPrismaAdapter(): Adapter {
   
   return {
     ...prismaAdapter,
-    async createUser(data: AdapterUser & { username?: string }) {
+    async createUser(data: AdapterUser & { username?: string; githubUsername?: string }) {
       // Use GitHub username if provided, otherwise generate one
       let username = (data as any).username;
+      const githubUsername = (data as any).githubUsername; // Immutable GitHub username
+      
       if (!username) {
         username = await generateUsername(data.email, data.name);
       } else {
@@ -64,6 +66,7 @@ function CustomPrismaAdapter(): Adapter {
               email: data.email,
               avatar: data.image,
               emailVerified: data.emailVerified,
+              githubUsername: githubUsername || undefined, // Store immutable GitHub username
             },
           });
           
@@ -91,6 +94,7 @@ function CustomPrismaAdapter(): Adapter {
           avatar: data.image,
           emailVerified: data.emailVerified,
           username,
+          githubUsername: githubUsername || undefined, // Store immutable GitHub username
         },
       });
       
diff --git a/src/lib/plugins/auth/github.ts b/src/lib/plugins/auth/github.ts
index c209e206..ed8bb4d0 100644
--- a/src/lib/plugins/auth/github.ts
+++ b/src/lib/plugins/auth/github.ts
@@ -14,7 +14,8 @@ export const githubPlugin: AuthPlugin = {
           name: profile.name || profile.login,
           email: profile.email,
           image: profile.avatar_url,
-          username: profile.login, // GitHub username
+          username: profile.login, // GitHub username (used as display username)
+          githubUsername: profile.login, // Immutable GitHub username for contributor attribution
         };
       },
     }),