diff --git a/src/app/api/auth/login/route.ts b/src/app/api/auth/login/route.ts
index 2e8c6b5..3000df2 100644
--- a/src/app/api/auth/login/route.ts
+++ b/src/app/api/auth/login/route.ts
@@ -1,5 +1,8 @@
 import { NextResponse } from "next/server";
 import { AuthServerService } from "@/lib/services/auth-server.service";
+import { ERROR_CODES } from "@/constants/errorCodes";
+import { ERROR_MESSAGES } from "@/constants/errorMessages";
+import { AppError } from "@/utils/errors";
 
 export async function POST(request: Request) {
   try {
@@ -9,14 +12,17 @@ export async function POST(request: Request) {
       const userData = await AuthServerService.loginUser(email, password);
       AuthServerService.setUserCookie(userData);
 
-      return NextResponse.json({ message: "Connexion réussie", user: userData });
+      return NextResponse.json({
+        message: "✅ Connexion réussie",
+        user: userData,
+      });
     } catch (error) {
-      if (error instanceof Error && error.message === "INVALID_CREDENTIALS") {
+      if (error instanceof AppError) {
         return NextResponse.json(
           {
             error: {
-              code: "INVALID_CREDENTIALS",
-              message: "Email ou mot de passe incorrect",
+              code: error.code,
+              message: ERROR_MESSAGES[error.code],
             },
           },
           { status: 401 }
@@ -29,8 +35,8 @@ export async function POST(request: Request) {
     return NextResponse.json(
       {
         error: {
-          code: "SERVER_ERROR",
-          message: "Une erreur est survenue lors de la connexion",
+          code: ERROR_CODES.AUTH.INVALID_CREDENTIALS,
+          message: ERROR_MESSAGES[ERROR_CODES.AUTH.INVALID_CREDENTIALS],
         },
       },
       { status: 500 }
diff --git a/src/app/api/auth/logout/route.ts b/src/app/api/auth/logout/route.ts
index 8eee72d..986dd7a 100644
--- a/src/app/api/auth/logout/route.ts
+++ b/src/app/api/auth/logout/route.ts
@@ -1,9 +1,23 @@
 import { NextResponse } from "next/server";
 import { cookies } from "next/headers";
+import { ERROR_CODES } from "@/constants/errorCodes";
+import { ERROR_MESSAGES } from "@/constants/errorMessages";
 
 export async function POST() {
-  // Supprimer le cookie
-  cookies().delete("stripUser");
-
-  return NextResponse.json({ message: "Déconnexion réussie" });
+  try {
+    // Supprimer le cookie
+    cookies().delete("stripUser");
+    return NextResponse.json({ message: "👋 Déconnexion réussie" });
+  } catch (error) {
+    console.error("Erreur lors de la déconnexion:", error);
+    return NextResponse.json(
+      {
+        error: {
+          code: ERROR_CODES.AUTH.LOGOUT_ERROR,
+          message: ERROR_MESSAGES[ERROR_CODES.AUTH.LOGOUT_ERROR],
+        },
+      },
+      { status: 500 }
+    );
+  }
 }
diff --git a/src/app/api/auth/register/route.ts b/src/app/api/auth/register/route.ts
index 632fe92..52ae88e 100644
--- a/src/app/api/auth/register/route.ts
+++ b/src/app/api/auth/register/route.ts
@@ -1,5 +1,8 @@
 import { NextResponse } from "next/server";
 import { AuthServerService } from "@/lib/services/auth-server.service";
+import { ERROR_CODES } from "@/constants/errorCodes";
+import { ERROR_MESSAGES } from "@/constants/errorMessages";
+import { AppError } from "@/utils/errors";
 
 export async function POST(request: Request) {
   try {
@@ -9,28 +12,25 @@ export async function POST(request: Request) {
       const userData = await AuthServerService.createUser(email, password);
       AuthServerService.setUserCookie(userData);
 
-      return NextResponse.json({ message: "Inscription réussie", user: userData });
+      return NextResponse.json({
+        message: "✅ Inscription réussie",
+        user: userData,
+      });
     } catch (error) {
-      if (error instanceof Error && error.message === "EMAIL_EXISTS") {
+      if (error instanceof AppError) {
+        const status =
+          error.code === ERROR_CODES.AUTH.EMAIL_EXISTS ||
+          error.code === ERROR_CODES.AUTH.PASSWORD_NOT_STRONG
+            ? 400
+            : 500;
         return NextResponse.json(
           {
             error: {
-              code: "EMAIL_EXISTS",
-              message: "Cet email est déjà utilisé",
+              code: error.code,
+              message: ERROR_MESSAGES[error.code],
             },
           },
-          { status: 400 }
-        );
-      }
-      if (error instanceof Error && error.message === "PASSWORD_NOT_STRONG") {
-        return NextResponse.json(
-          {
-            error: {
-              code: "PASSWORD_NOT_STRONG",
-              message: "Le mot de passe est trop faible",
-            },
-          },
-          { status: 400 }
+          { status }
         );
       }
       throw error;
@@ -40,8 +40,8 @@ export async function POST(request: Request) {
     return NextResponse.json(
       {
         error: {
-          code: "SERVER_ERROR",
-          message: "Une erreur est survenue lors de l'inscription",
+          code: ERROR_CODES.AUTH.INVALID_USER_DATA,
+          message: ERROR_MESSAGES[ERROR_CODES.AUTH.INVALID_USER_DATA],
         },
       },
       { status: 500 }
diff --git a/src/app/api/debug/route.ts b/src/app/api/debug/route.ts
index a88daec..e4055e0 100644
--- a/src/app/api/debug/route.ts
+++ b/src/app/api/debug/route.ts
@@ -1,12 +1,35 @@
 import { NextRequest, NextResponse } from "next/server";
 import { DebugService } from "@/lib/services/debug.service";
+import { ERROR_CODES } from "@/constants/errorCodes";
+import { ERROR_MESSAGES } from "@/constants/errorMessages";
+import { AppError } from "@/utils/errors";
 
 export async function GET() {
   try {
     const logs = await DebugService.getRequestLogs();
     return NextResponse.json(logs);
   } catch (error) {
-    return NextResponse.json({ error: "Erreur lors de la récupération des logs" }, { status: 500 });
+    console.error("Erreur lors de la récupération des logs:", error);
+    if (error instanceof AppError) {
+      return NextResponse.json(
+        {
+          error: {
+            code: error.code,
+            message: ERROR_MESSAGES[error.code],
+          },
+        },
+        { status: 500 }
+      );
+    }
+    return NextResponse.json(
+      {
+        error: {
+          code: ERROR_CODES.DEBUG.FETCH_ERROR,
+          message: ERROR_MESSAGES[ERROR_CODES.DEBUG.FETCH_ERROR],
+        },
+      },
+      { status: 500 }
+    );
   }
 }
 
@@ -14,17 +37,61 @@ export async function POST(request: NextRequest) {
   try {
     const timing = await request.json();
     await DebugService.logRequest(timing);
-    return NextResponse.json({ success: true });
+    return NextResponse.json({
+      message: "✅ Log enregistré avec succès",
+    });
   } catch (error) {
-    return NextResponse.json({ error: "Erreur lors de l'enregistrement du log" }, { status: 500 });
+    console.error("Erreur lors de l'enregistrement du log:", error);
+    if (error instanceof AppError) {
+      return NextResponse.json(
+        {
+          error: {
+            code: error.code,
+            message: ERROR_MESSAGES[error.code],
+          },
+        },
+        { status: 500 }
+      );
+    }
+    return NextResponse.json(
+      {
+        error: {
+          code: ERROR_CODES.DEBUG.SAVE_ERROR,
+          message: ERROR_MESSAGES[ERROR_CODES.DEBUG.SAVE_ERROR],
+        },
+      },
+      { status: 500 }
+    );
   }
 }
 
 export async function DELETE() {
   try {
     await DebugService.clearLogs();
-    return NextResponse.json({ success: true });
+    return NextResponse.json({
+      message: "🧹 Logs supprimés avec succès",
+    });
   } catch (error) {
-    return NextResponse.json({ error: "Erreur lors de la suppression des logs" }, { status: 500 });
+    console.error("Erreur lors de la suppression des logs:", error);
+    if (error instanceof AppError) {
+      return NextResponse.json(
+        {
+          error: {
+            code: error.code,
+            message: ERROR_MESSAGES[error.code],
+          },
+        },
+        { status: 500 }
+      );
+    }
+    return NextResponse.json(
+      {
+        error: {
+          code: ERROR_CODES.DEBUG.CLEAR_ERROR,
+          message: ERROR_MESSAGES[ERROR_CODES.DEBUG.CLEAR_ERROR],
+        },
+      },
+      { status: 500 }
+    );
   }
 }
diff --git a/src/app/api/komga/books/[bookId]/pages/[pageNumber]/route.ts b/src/app/api/komga/books/[bookId]/pages/[pageNumber]/route.ts
index 72fdba3..1dfa66b 100644
--- a/src/app/api/komga/books/[bookId]/pages/[pageNumber]/route.ts
+++ b/src/app/api/komga/books/[bookId]/pages/[pageNumber]/route.ts
@@ -1,14 +1,30 @@
-import { NextResponse } from "next/server";
+import { NextRequest, NextResponse } from "next/server";
 import { BookService } from "@/lib/services/book.service";
+import { ERROR_CODES } from "@/constants/errorCodes";
+import { ERROR_MESSAGES } from "@/constants/errorMessages";
+import { AppError } from "@/utils/errors";
 
 export const dynamic = "force-dynamic";
 
 export async function GET(
-  request: Request,
+  request: NextRequest,
   { params }: { params: { bookId: string; pageNumber: string } }
 ) {
   try {
-    const response = await BookService.getPage(params.bookId, parseInt(params.pageNumber));
+    const pageNumber = parseInt(params.pageNumber);
+    if (isNaN(pageNumber) || pageNumber < 0) {
+      return NextResponse.json(
+        {
+          error: {
+            code: ERROR_CODES.IMAGE.FETCH_ERROR,
+            message: ERROR_MESSAGES[ERROR_CODES.IMAGE.FETCH_ERROR],
+          },
+        },
+        { status: 400 }
+      );
+    }
+
+    const response = await BookService.getPage(params.bookId, pageNumber);
     const buffer = await response.arrayBuffer();
     const headers = new Headers();
     headers.set("Content-Type", response.headers.get("Content-Type") || "image/jpeg");
@@ -19,9 +35,25 @@ export async function GET(
       headers,
     });
   } catch (error) {
-    console.error("API Book Page - Erreur:", error);
+    console.error("Erreur lors de la récupération de la page:", error);
+    if (error instanceof AppError) {
+      return NextResponse.json(
+        {
+          error: {
+            code: error.code,
+            message: ERROR_MESSAGES[error.code],
+          },
+        },
+        { status: 500 }
+      );
+    }
     return NextResponse.json(
-      { error: "Erreur lors de la récupération de la page" },
+      {
+        error: {
+          code: ERROR_CODES.IMAGE.FETCH_ERROR,
+          message: ERROR_MESSAGES[ERROR_CODES.IMAGE.FETCH_ERROR],
+        },
+      },
       { status: 500 }
     );
   }
diff --git a/src/app/api/komga/books/[bookId]/read-progress/route.ts b/src/app/api/komga/books/[bookId]/read-progress/route.ts
index bcb7284..4bf71dc 100644
--- a/src/app/api/komga/books/[bookId]/read-progress/route.ts
+++ b/src/app/api/komga/books/[bookId]/read-progress/route.ts
@@ -1,35 +1,76 @@
-import { NextResponse } from "next/server";
+import { NextRequest, NextResponse } from "next/server";
 import { BookService } from "@/lib/services/book.service";
+import { ERROR_CODES } from "@/constants/errorCodes";
+import { ERROR_MESSAGES } from "@/constants/errorMessages";
+import { AppError } from "@/utils/errors";
 
-export async function PATCH(request: Request, { params }: { params: { bookId: string } }) {
+export async function PATCH(request: NextRequest, { params }: { params: { bookId: string } }) {
   try {
     const { page, completed } = await request.json();
 
     if (typeof page !== "number") {
       return NextResponse.json(
-        { error: "Le numéro de page est requis et doit être un nombre" },
+        {
+          error: {
+            code: ERROR_CODES.BOOK.PROGRESS_UPDATE_ERROR,
+            message: ERROR_MESSAGES[ERROR_CODES.BOOK.PROGRESS_UPDATE_ERROR],
+          },
+        },
         { status: 400 }
       );
     }
 
     await BookService.updateReadProgress(params.bookId, page, completed);
-    return NextResponse.json({ message: "Progression mise à jour avec succès" });
+    return NextResponse.json({ message: "📖 Progression mise à jour avec succès" });
   } catch (error) {
-    console.error("API Read Progress - Erreur:", error);
+    console.error("Erreur lors de la mise à jour de la progression:", error);
+    if (error instanceof AppError) {
+      return NextResponse.json(
+        {
+          error: {
+            code: error.code,
+            message: ERROR_MESSAGES[error.code],
+          },
+        },
+        { status: 500 }
+      );
+    }
     return NextResponse.json(
-      { error: "Erreur lors de la mise à jour de la progression" },
+      {
+        error: {
+          code: ERROR_CODES.BOOK.PROGRESS_UPDATE_ERROR,
+          message: ERROR_MESSAGES[ERROR_CODES.BOOK.PROGRESS_UPDATE_ERROR],
+        },
+      },
       { status: 500 }
     );
   }
 }
-export async function DELETE(request: Request, { params }: { params: { bookId: string } }) {
+
+export async function DELETE(request: NextRequest, { params }: { params: { bookId: string } }) {
   try {
     await BookService.deleteReadProgress(params.bookId);
-    return NextResponse.json({ message: "Progression supprimée avec succès" });
+    return NextResponse.json({ message: "🗑️ Progression supprimée avec succès" });
   } catch (error) {
-    console.error("API Delete Read Progress - Erreur:", error);
+    console.error("Erreur lors de la suppression de la progression:", error);
+    if (error instanceof AppError) {
+      return NextResponse.json(
+        {
+          error: {
+            code: error.code,
+            message: ERROR_MESSAGES[error.code],
+          },
+        },
+        { status: 500 }
+      );
+    }
     return NextResponse.json(
-      { error: "Erreur lors de la suppression de la progression" },
+      {
+        error: {
+          code: ERROR_CODES.BOOK.PROGRESS_DELETE_ERROR,
+          message: ERROR_MESSAGES[ERROR_CODES.BOOK.PROGRESS_DELETE_ERROR],
+        },
+      },
       { status: 500 }
     );
   }
diff --git a/src/app/api/komga/books/[bookId]/route.ts b/src/app/api/komga/books/[bookId]/route.ts
index 6df2218..0e4a6a0 100644
--- a/src/app/api/komga/books/[bookId]/route.ts
+++ b/src/app/api/komga/books/[bookId]/route.ts
@@ -1,5 +1,8 @@
 import { NextResponse } from "next/server";
 import { BookService } from "@/lib/services/book.service";
+import { ERROR_CODES } from "@/constants/errorCodes";
+import { ERROR_MESSAGES } from "@/constants/errorMessages";
+import { AppError } from "@/utils/errors";
 
 export async function GET(request: Request, { params }: { params: { bookId: string } }) {
   try {
@@ -7,6 +10,25 @@ export async function GET(request: Request, { params }: { params: { bookId: stri
     return NextResponse.json(data);
   } catch (error) {
     console.error("API Books - Erreur:", error);
-    return NextResponse.json({ error: "Erreur lors de la récupération du tome" }, { status: 500 });
+    if (error instanceof AppError) {
+      return NextResponse.json(
+        {
+          error: {
+            code: error.code,
+            message: ERROR_MESSAGES[error.code],
+          },
+        },
+        { status: 500 }
+      );
+    }
+    return NextResponse.json(
+      {
+        error: {
+          code: ERROR_CODES.BOOK.NOT_FOUND,
+          message: ERROR_MESSAGES[ERROR_CODES.BOOK.NOT_FOUND],
+        },
+      },
+      { status: 500 }
+    );
   }
 }
diff --git a/src/app/api/komga/cache/clear/route.ts b/src/app/api/komga/cache/clear/route.ts
index 5bdbcec..f58c9b1 100644
--- a/src/app/api/komga/cache/clear/route.ts
+++ b/src/app/api/komga/cache/clear/route.ts
@@ -1,8 +1,23 @@
 import { NextResponse } from "next/server";
 import { getServerCacheService } from "@/lib/services/server-cache.service";
+import { ERROR_CODES } from "@/constants/errorCodes";
+import { ERROR_MESSAGES } from "@/constants/errorMessages";
 
 export async function POST() {
-  const cacheService = await getServerCacheService();
-  cacheService.clear();
-  return NextResponse.json({ message: "Cache cleared" });
+  try {
+    const cacheService = await getServerCacheService();
+    cacheService.clear();
+    return NextResponse.json({ message: "🧹 Cache vidé avec succès" });
+  } catch (error) {
+    console.error("Erreur lors de la suppression du cache:", error);
+    return NextResponse.json(
+      {
+        error: {
+          code: ERROR_CODES.CACHE.CLEAR_ERROR,
+          message: ERROR_MESSAGES[ERROR_CODES.CACHE.CLEAR_ERROR],
+        },
+      },
+      { status: 500 }
+    );
+  }
 }
diff --git a/src/app/api/komga/cache/mode/route.ts b/src/app/api/komga/cache/mode/route.ts
index affb6d7..3738e50 100644
--- a/src/app/api/komga/cache/mode/route.ts
+++ b/src/app/api/komga/cache/mode/route.ts
@@ -1,9 +1,24 @@
 import { NextResponse } from "next/server";
 import { getServerCacheService } from "@/lib/services/server-cache.service";
+import { ERROR_CODES } from "@/constants/errorCodes";
+import { ERROR_MESSAGES } from "@/constants/errorMessages";
 
 export async function GET() {
-  const cacheService = await getServerCacheService();
-  return NextResponse.json({ mode: cacheService.getCacheMode() });
+  try {
+    const cacheService = await getServerCacheService();
+    return NextResponse.json({ mode: cacheService.getCacheMode() });
+  } catch (error) {
+    console.error("Erreur lors de la récupération du mode de cache:", error);
+    return NextResponse.json(
+      {
+        error: {
+          code: ERROR_CODES.CACHE.MODE_FETCH_ERROR,
+          message: ERROR_MESSAGES[ERROR_CODES.CACHE.MODE_FETCH_ERROR],
+        },
+      },
+      { status: 500 }
+    );
+  }
 }
 
 export async function POST(request: Request) {
@@ -11,7 +26,12 @@ export async function POST(request: Request) {
     const { mode } = await request.json();
     if (mode !== "file" && mode !== "memory") {
       return NextResponse.json(
-        { error: "Invalid mode. Must be 'file' or 'memory'" },
+        {
+          error: {
+            code: ERROR_CODES.CACHE.INVALID_MODE,
+            message: ERROR_MESSAGES[ERROR_CODES.CACHE.INVALID_MODE],
+          },
+        },
         { status: 400 }
       );
     }
@@ -21,6 +41,14 @@ export async function POST(request: Request) {
     return NextResponse.json({ mode: cacheService.getCacheMode() });
   } catch (error) {
     console.error("Erreur lors de la mise à jour du mode de cache:", error);
-    return NextResponse.json({ error: "Invalid request" }, { status: 400 });
+    return NextResponse.json(
+      {
+        error: {
+          code: ERROR_CODES.CACHE.MODE_UPDATE_ERROR,
+          message: ERROR_MESSAGES[ERROR_CODES.CACHE.MODE_UPDATE_ERROR],
+        },
+      },
+      { status: 500 }
+    );
   }
 }
diff --git a/src/app/api/komga/config/route.ts b/src/app/api/komga/config/route.ts
index 003e47b..826eb54 100644
--- a/src/app/api/komga/config/route.ts
+++ b/src/app/api/komga/config/route.ts
@@ -1,5 +1,7 @@
 import { NextResponse } from "next/server";
 import { ConfigDBService } from "@/lib/services/config-db.service";
+import { ERROR_CODES } from "@/constants/errorCodes";
+import { ERROR_MESSAGES } from "@/constants/errorMessages";
 
 export const dynamic = "force-dynamic";
 
@@ -15,16 +17,29 @@ export async function POST(request: Request) {
       userId: mongoConfig.userId,
     };
     return NextResponse.json(
-      { message: "Configuration sauvegardée avec succès", config },
+      { message: "⚙️ Configuration sauvegardée avec succès", config },
       { status: 200 }
     );
   } catch (error) {
     console.error("Erreur lors de la sauvegarde de la configuration:", error);
     if (error instanceof Error && error.message === "Utilisateur non authentifié") {
-      return NextResponse.json({ error: "Non autorisé" }, { status: 401 });
+      return NextResponse.json(
+        {
+          error: {
+            code: ERROR_CODES.MIDDLEWARE.UNAUTHORIZED,
+            message: ERROR_MESSAGES[ERROR_CODES.MIDDLEWARE.UNAUTHORIZED],
+          },
+        },
+        { status: 401 }
+      );
     }
     return NextResponse.json(
-      { error: "Erreur lors de la sauvegarde de la configuration" },
+      {
+        error: {
+          code: ERROR_CODES.CONFIG.SAVE_ERROR,
+          message: ERROR_MESSAGES[ERROR_CODES.CONFIG.SAVE_ERROR],
+        },
+      },
       { status: 500 }
     );
   }
@@ -45,14 +60,35 @@ export async function GET() {
     console.error("Erreur lors de la récupération de la configuration:", error);
     if (error instanceof Error) {
       if (error.message === "Utilisateur non authentifié") {
-        return NextResponse.json({ error: "Non autorisé" }, { status: 401 });
+        return NextResponse.json(
+          {
+            error: {
+              code: ERROR_CODES.MIDDLEWARE.UNAUTHORIZED,
+              message: ERROR_MESSAGES[ERROR_CODES.MIDDLEWARE.UNAUTHORIZED],
+            },
+          },
+          { status: 401 }
+        );
       }
       if (error.message === "Configuration non trouvée") {
-        return NextResponse.json({ error: "Configuration non trouvée" }, { status: 404 });
+        return NextResponse.json(
+          {
+            error: {
+              code: ERROR_CODES.KOMGA.MISSING_CONFIG,
+              message: ERROR_MESSAGES[ERROR_CODES.KOMGA.MISSING_CONFIG],
+            },
+          },
+          { status: 404 }
+        );
       }
     }
     return NextResponse.json(
-      { error: "Erreur lors de la récupération de la configuration" },
+      {
+        error: {
+          code: ERROR_CODES.CONFIG.FETCH_ERROR,
+          message: ERROR_MESSAGES[ERROR_CODES.CONFIG.FETCH_ERROR],
+        },
+      },
       { status: 500 }
     );
   }
diff --git a/src/app/api/komga/favorites/route.ts b/src/app/api/komga/favorites/route.ts
index 6299109..40e8dab 100644
--- a/src/app/api/komga/favorites/route.ts
+++ b/src/app/api/komga/favorites/route.ts
@@ -1,5 +1,8 @@
 import { NextResponse } from "next/server";
 import { FavoriteService } from "@/lib/services/favorite.service";
+import { ERROR_CODES } from "@/constants/errorCodes";
+import { ERROR_MESSAGES } from "@/constants/errorMessages";
+import { AppError } from "@/utils/errors";
 
 export async function GET() {
   try {
@@ -7,8 +10,24 @@ export async function GET() {
     return NextResponse.json(favoriteIds);
   } catch (error) {
     console.error("Erreur lors de la récupération des favoris:", error);
+    if (error instanceof AppError) {
+      return NextResponse.json(
+        {
+          error: {
+            code: error.code,
+            message: ERROR_MESSAGES[error.code],
+          },
+        },
+        { status: 500 }
+      );
+    }
     return NextResponse.json(
-      { error: "Erreur lors de la récupération des favoris" },
+      {
+        error: {
+          code: ERROR_CODES.FAVORITE.FETCH_ERROR,
+          message: ERROR_MESSAGES[ERROR_CODES.FAVORITE.FETCH_ERROR],
+        },
+      },
       { status: 500 }
     );
   }
@@ -18,10 +37,29 @@ export async function POST(request: Request) {
   try {
     const { seriesId } = await request.json();
     await FavoriteService.addToFavorites(seriesId);
-    return NextResponse.json({ message: "Favori ajouté avec succès" });
+    return NextResponse.json({ message: "⭐️ Série ajoutée aux favoris" });
   } catch (error) {
     console.error("Erreur lors de l'ajout du favori:", error);
-    return NextResponse.json({ error: "Erreur lors de l'ajout du favori" }, { status: 500 });
+    if (error instanceof AppError) {
+      return NextResponse.json(
+        {
+          error: {
+            code: error.code,
+            message: ERROR_MESSAGES[error.code],
+          },
+        },
+        { status: 500 }
+      );
+    }
+    return NextResponse.json(
+      {
+        error: {
+          code: ERROR_CODES.FAVORITE.ADD_ERROR,
+          message: ERROR_MESSAGES[ERROR_CODES.FAVORITE.ADD_ERROR],
+        },
+      },
+      { status: 500 }
+    );
   }
 }
 
@@ -29,9 +67,28 @@ export async function DELETE(request: Request) {
   try {
     const { seriesId } = await request.json();
     await FavoriteService.removeFromFavorites(seriesId);
-    return NextResponse.json({ message: "Favori supprimé avec succès" });
+    return NextResponse.json({ message: "💔 Série retirée des favoris" });
   } catch (error) {
     console.error("Erreur lors de la suppression du favori:", error);
-    return NextResponse.json({ error: "Erreur lors de la suppression du favori" }, { status: 500 });
+    if (error instanceof AppError) {
+      return NextResponse.json(
+        {
+          error: {
+            code: error.code,
+            message: ERROR_MESSAGES[error.code],
+          },
+        },
+        { status: 500 }
+      );
+    }
+    return NextResponse.json(
+      {
+        error: {
+          code: ERROR_CODES.FAVORITE.DELETE_ERROR,
+          message: ERROR_MESSAGES[ERROR_CODES.FAVORITE.DELETE_ERROR],
+        },
+      },
+      { status: 500 }
+    );
   }
 }
diff --git a/src/app/api/komga/images/books/[bookId]/pages/[pageNumber]/route.ts b/src/app/api/komga/images/books/[bookId]/pages/[pageNumber]/route.ts
index dacb942..a266567 100644
--- a/src/app/api/komga/images/books/[bookId]/pages/[pageNumber]/route.ts
+++ b/src/app/api/komga/images/books/[bookId]/pages/[pageNumber]/route.ts
@@ -1,5 +1,8 @@
 import { NextRequest, NextResponse } from "next/server";
 import { BookService } from "@/lib/services/book.service";
+import { ERROR_CODES } from "@/constants/errorCodes";
+import { ERROR_MESSAGES } from "@/constants/errorMessages";
+import { AppError } from "@/utils/errors";
 
 export const dynamic = "force-dynamic";
 
@@ -12,6 +15,25 @@ export async function GET(
     return response;
   } catch (error) {
     console.error("Erreur lors de la récupération de la page du livre:", error);
-    return new NextResponse("Erreur lors de la récupération de la page", { status: 500 });
+    if (error instanceof AppError) {
+      return NextResponse.json(
+        {
+          error: {
+            code: error.code,
+            message: ERROR_MESSAGES[error.code],
+          },
+        },
+        { status: 500 }
+      );
+    }
+    return NextResponse.json(
+      {
+        error: {
+          code: ERROR_CODES.IMAGE.FETCH_ERROR,
+          message: ERROR_MESSAGES[ERROR_CODES.IMAGE.FETCH_ERROR],
+        },
+      },
+      { status: 500 }
+    );
   }
 }
diff --git a/src/app/api/komga/images/books/[bookId]/pages/[pageNumber]/thumbnail/route.ts b/src/app/api/komga/images/books/[bookId]/pages/[pageNumber]/thumbnail/route.ts
index 851d3e2..9616e42 100644
--- a/src/app/api/komga/images/books/[bookId]/pages/[pageNumber]/thumbnail/route.ts
+++ b/src/app/api/komga/images/books/[bookId]/pages/[pageNumber]/thumbnail/route.ts
@@ -1,28 +1,52 @@
-import { NextResponse } from "next/server";
+import { NextRequest, NextResponse } from "next/server";
 import { BookService } from "@/lib/services/book.service";
+import { ERROR_CODES } from "@/constants/errorCodes";
+import { ERROR_MESSAGES } from "@/constants/errorMessages";
+import { AppError } from "@/utils/errors";
 
 export const dynamic = "force-dynamic";
 
 export async function GET(
-  request: Request,
+  request: NextRequest,
   { params }: { params: { bookId: string; pageNumber: string } }
 ) {
   try {
     // Convertir le numéro de page en nombre
     const pageNumber = parseInt(params.pageNumber);
     if (isNaN(pageNumber) || pageNumber < 0) {
-      return NextResponse.json({ error: "Numéro de page invalide" }, { status: 400 });
+      return NextResponse.json(
+        {
+          error: {
+            code: ERROR_CODES.BOOK.PAGES_FETCH_ERROR,
+            message: ERROR_MESSAGES[ERROR_CODES.BOOK.PAGES_FETCH_ERROR],
+          },
+        },
+        { status: 400 }
+      );
     }
 
     const response = await BookService.getPageThumbnail(params.bookId, pageNumber);
     return response;
   } catch (error) {
-    console.error("API Book Page Thumbnail - Erreur:", error);
-    if (error instanceof Error) {
-      return NextResponse.json({ error: error.message }, { status: 500 });
+    console.error("Erreur lors de la récupération de la miniature de la page:", error);
+    if (error instanceof AppError) {
+      return NextResponse.json(
+        {
+          error: {
+            code: error.code,
+            message: ERROR_MESSAGES[error.code],
+          },
+        },
+        { status: 500 }
+      );
     }
     return NextResponse.json(
-      { error: "Une erreur est survenue lors de la récupération de la miniature" },
+      {
+        error: {
+          code: ERROR_CODES.IMAGE.FETCH_ERROR,
+          message: ERROR_MESSAGES[ERROR_CODES.IMAGE.FETCH_ERROR],
+        },
+      },
       { status: 500 }
     );
   }
diff --git a/src/app/api/komga/images/books/[bookId]/thumbnail/route.ts b/src/app/api/komga/images/books/[bookId]/thumbnail/route.ts
index ef228fe..d514f17 100644
--- a/src/app/api/komga/images/books/[bookId]/thumbnail/route.ts
+++ b/src/app/api/komga/images/books/[bookId]/thumbnail/route.ts
@@ -1,5 +1,8 @@
 import { NextRequest, NextResponse } from "next/server";
 import { BookService } from "@/lib/services/book.service";
+import { ERROR_CODES } from "@/constants/errorCodes";
+import { ERROR_MESSAGES } from "@/constants/errorMessages";
+import { AppError } from "@/utils/errors";
 
 export async function GET(request: NextRequest, { params }: { params: { bookId: string } }) {
   try {
@@ -7,6 +10,25 @@ export async function GET(request: NextRequest, { params }: { params: { bookId:
     return response;
   } catch (error) {
     console.error("Erreur lors de la récupération de la miniature du livre:", error);
-    return new NextResponse("Erreur lors de la récupération de la miniature", { status: 500 });
+    if (error instanceof AppError) {
+      return NextResponse.json(
+        {
+          error: {
+            code: error.code,
+            message: ERROR_MESSAGES[error.code],
+          },
+        },
+        { status: 500 }
+      );
+    }
+    return NextResponse.json(
+      {
+        error: {
+          code: ERROR_CODES.IMAGE.FETCH_ERROR,
+          message: ERROR_MESSAGES[ERROR_CODES.IMAGE.FETCH_ERROR],
+        },
+      },
+      { status: 500 }
+    );
   }
 }
diff --git a/src/app/api/komga/images/series/[seriesId]/first-page/route.ts b/src/app/api/komga/images/series/[seriesId]/first-page/route.ts
index a8b62fc..82329dc 100644
--- a/src/app/api/komga/images/series/[seriesId]/first-page/route.ts
+++ b/src/app/api/komga/images/series/[seriesId]/first-page/route.ts
@@ -1,5 +1,8 @@
 import { NextRequest, NextResponse } from "next/server";
 import { SeriesService } from "@/lib/services/series.service";
+import { ERROR_CODES } from "@/constants/errorCodes";
+import { ERROR_MESSAGES } from "@/constants/errorMessages";
+import { AppError } from "@/utils/errors";
 
 export const dynamic = "force-dynamic";
 
@@ -9,6 +12,25 @@ export async function GET(request: NextRequest, { params }: { params: { seriesId
     return response;
   } catch (error) {
     console.error("Erreur lors de la récupération de la couverture de la série:", error);
-    return new NextResponse("Erreur lors de la récupération de la couverture", { status: 500 });
+    if (error instanceof AppError) {
+      return NextResponse.json(
+        {
+          error: {
+            code: error.code,
+            message: ERROR_MESSAGES[error.code],
+          },
+        },
+        { status: 500 }
+      );
+    }
+    return NextResponse.json(
+      {
+        error: {
+          code: ERROR_CODES.IMAGE.FETCH_ERROR,
+          message: ERROR_MESSAGES[ERROR_CODES.IMAGE.FETCH_ERROR],
+        },
+      },
+      { status: 500 }
+    );
   }
 }
diff --git a/src/app/api/komga/images/series/[seriesId]/thumbnail/route.ts b/src/app/api/komga/images/series/[seriesId]/thumbnail/route.ts
index 23472d9..584b926 100644
--- a/src/app/api/komga/images/series/[seriesId]/thumbnail/route.ts
+++ b/src/app/api/komga/images/series/[seriesId]/thumbnail/route.ts
@@ -1,5 +1,8 @@
 import { NextRequest, NextResponse } from "next/server";
 import { SeriesService } from "@/lib/services/series.service";
+import { ERROR_CODES } from "@/constants/errorCodes";
+import { ERROR_MESSAGES } from "@/constants/errorMessages";
+import { AppError } from "@/utils/errors";
 
 export async function GET(request: NextRequest, { params }: { params: { seriesId: string } }) {
   try {
@@ -7,6 +10,25 @@ export async function GET(request: NextRequest, { params }: { params: { seriesId
     return response;
   } catch (error) {
     console.error("Erreur lors de la récupération de la miniature de la série:", error);
-    return new NextResponse("Erreur lors de la récupération de la miniature", { status: 500 });
+    if (error instanceof AppError) {
+      return NextResponse.json(
+        {
+          error: {
+            code: error.code,
+            message: ERROR_MESSAGES[error.code],
+          },
+        },
+        { status: 500 }
+      );
+    }
+    return NextResponse.json(
+      {
+        error: {
+          code: ERROR_CODES.IMAGE.FETCH_ERROR,
+          message: ERROR_MESSAGES[ERROR_CODES.IMAGE.FETCH_ERROR],
+        },
+      },
+      { status: 500 }
+    );
   }
 }
diff --git a/src/app/api/komga/libraries/route.ts b/src/app/api/komga/libraries/route.ts
index c8648f1..8a6422f 100644
--- a/src/app/api/komga/libraries/route.ts
+++ b/src/app/api/komga/libraries/route.ts
@@ -1,5 +1,8 @@
 import { NextResponse } from "next/server";
 import { LibraryService } from "@/lib/services/library.service";
+import { ERROR_CODES } from "@/constants/errorCodes";
+import { ERROR_MESSAGES } from "@/constants/errorMessages";
+import { AppError } from "@/utils/errors";
 
 export const dynamic = "force-dynamic";
 
@@ -9,6 +12,25 @@ export async function GET() {
     return NextResponse.json(libraries);
   } catch (error) {
     console.error("API Libraries - Erreur:", error);
-    return NextResponse.json({ error: "Erreur serveur" }, { status: 500 });
+    if (error instanceof AppError) {
+      return NextResponse.json(
+        {
+          error: {
+            code: error.code,
+            message: ERROR_MESSAGES[error.code],
+          },
+        },
+        { status: 500 }
+      );
+    }
+    return NextResponse.json(
+      {
+        error: {
+          code: ERROR_CODES.LIBRARY.FETCH_ERROR,
+          message: ERROR_MESSAGES[ERROR_CODES.LIBRARY.FETCH_ERROR],
+        },
+      },
+      { status: 500 }
+    );
   }
 }
diff --git a/src/app/api/komga/series/[seriesId]/route.ts b/src/app/api/komga/series/[seriesId]/route.ts
index 5a6d502..34815ae 100644
--- a/src/app/api/komga/series/[seriesId]/route.ts
+++ b/src/app/api/komga/series/[seriesId]/route.ts
@@ -1,5 +1,8 @@
 import { NextResponse } from "next/server";
 import { SeriesService } from "@/lib/services/series.service";
+import { ERROR_CODES } from "@/constants/errorCodes";
+import { ERROR_MESSAGES } from "@/constants/errorMessages";
+import { AppError } from "@/utils/errors";
 
 export const dynamic = "force-dynamic";
 
@@ -9,8 +12,24 @@ export async function GET(request: Request, { params }: { params: { seriesId: st
     return NextResponse.json(series);
   } catch (error) {
     console.error("API Series - Erreur:", error);
+    if (error instanceof AppError) {
+      return NextResponse.json(
+        {
+          error: {
+            code: error.code,
+            message: ERROR_MESSAGES[error.code],
+          },
+        },
+        { status: 500 }
+      );
+    }
     return NextResponse.json(
-      { error: "Erreur lors de la récupération de la série" },
+      {
+        error: {
+          code: ERROR_CODES.SERIES.FETCH_ERROR,
+          message: ERROR_MESSAGES[ERROR_CODES.SERIES.FETCH_ERROR],
+        },
+      },
       { status: 500 }
     );
   }
diff --git a/src/app/api/komga/test/route.ts b/src/app/api/komga/test/route.ts
index 85540c2..595e1f5 100644
--- a/src/app/api/komga/test/route.ts
+++ b/src/app/api/komga/test/route.ts
@@ -1,5 +1,7 @@
 import { NextResponse } from "next/server";
 import { TestService } from "@/lib/services/test.service";
+import { ERROR_CODES } from "@/constants/errorCodes";
+import { ERROR_MESSAGES } from "@/constants/errorMessages";
 
 export async function POST(request: Request) {
   try {
@@ -12,14 +14,18 @@ export async function POST(request: Request) {
     });
 
     return NextResponse.json({
-      message: "Connexion réussie",
-      librariesCount: libraries.length,
+      message: `✅ Connexion réussie ! ${libraries.length} bibliothèque${
+        libraries.length > 1 ? "s" : ""
+      } trouvée${libraries.length > 1 ? "s" : ""}`,
     });
   } catch (error) {
     console.error("Erreur lors du test de connexion:", error);
     return NextResponse.json(
       {
-        error: error instanceof Error ? error.message : "Erreur inconnue",
+        error: {
+          code: ERROR_CODES.KOMGA.CONNECTION_ERROR,
+          message: ERROR_MESSAGES[ERROR_CODES.KOMGA.CONNECTION_ERROR],
+        },
       },
       { status: 400 }
     );
diff --git a/src/app/api/komga/ttl-config/route.ts b/src/app/api/komga/ttl-config/route.ts
index 2b0923d..57a2bf9 100644
--- a/src/app/api/komga/ttl-config/route.ts
+++ b/src/app/api/komga/ttl-config/route.ts
@@ -1,5 +1,7 @@
 import { NextResponse } from "next/server";
 import { ConfigDBService } from "@/lib/services/config-db.service";
+import { ERROR_CODES } from "@/constants/errorCodes";
+import { ERROR_MESSAGES } from "@/constants/errorMessages";
 
 export async function GET() {
   try {
@@ -9,11 +11,24 @@ export async function GET() {
     console.error("Erreur lors de la récupération de la configuration TTL:", error);
     if (error instanceof Error) {
       if (error.message === "Utilisateur non authentifié") {
-        return NextResponse.json({ error: "Non autorisé" }, { status: 401 });
+        return NextResponse.json(
+          {
+            error: {
+              code: ERROR_CODES.MIDDLEWARE.UNAUTHORIZED,
+              message: ERROR_MESSAGES[ERROR_CODES.MIDDLEWARE.UNAUTHORIZED],
+            },
+          },
+          { status: 401 }
+        );
       }
     }
     return NextResponse.json(
-      { error: "Erreur lors de la récupération de la configuration TTL" },
+      {
+        error: {
+          code: ERROR_CODES.CONFIG.TTL_FETCH_ERROR,
+          message: ERROR_MESSAGES[ERROR_CODES.CONFIG.TTL_FETCH_ERROR],
+        },
+      },
       { status: 500 }
     );
   }
@@ -24,7 +39,7 @@ export async function POST(request: Request) {
     const data = await request.json();
     const config = await ConfigDBService.saveTTLConfig(data);
     return NextResponse.json({
-      message: "Configuration TTL sauvegardée avec succès",
+      message: "⏱️ Configuration TTL sauvegardée avec succès",
       config: {
         defaultTTL: config.defaultTTL,
         homeTTL: config.homeTTL,
@@ -37,10 +52,23 @@ export async function POST(request: Request) {
   } catch (error) {
     console.error("Erreur lors de la sauvegarde de la configuration TTL:", error);
     if (error instanceof Error && error.message === "Utilisateur non authentifié") {
-      return NextResponse.json({ error: "Non autorisé" }, { status: 401 });
+      return NextResponse.json(
+        {
+          error: {
+            code: ERROR_CODES.MIDDLEWARE.UNAUTHORIZED,
+            message: ERROR_MESSAGES[ERROR_CODES.MIDDLEWARE.UNAUTHORIZED],
+          },
+        },
+        { status: 401 }
+      );
     }
     return NextResponse.json(
-      { error: "Erreur lors de la sauvegarde de la configuration TTL" },
+      {
+        error: {
+          code: ERROR_CODES.CONFIG.TTL_SAVE_ERROR,
+          message: ERROR_MESSAGES[ERROR_CODES.CONFIG.TTL_SAVE_ERROR],
+        },
+      },
       { status: 500 }
     );
   }
diff --git a/src/app/api/preferences/route.ts b/src/app/api/preferences/route.ts
index 9d656de..fafebc1 100644
--- a/src/app/api/preferences/route.ts
+++ b/src/app/api/preferences/route.ts
@@ -1,5 +1,8 @@
 import { NextRequest, NextResponse } from "next/server";
 import { PreferencesService } from "@/lib/services/preferences.service";
+import { ERROR_CODES } from "@/constants/errorCodes";
+import { ERROR_MESSAGES } from "@/constants/errorMessages";
+import { AppError } from "@/utils/errors";
 
 export async function GET() {
   try {
@@ -7,7 +10,26 @@ export async function GET() {
     return NextResponse.json(preferences);
   } catch (error) {
     console.error("Erreur lors de la récupération des préférences:", error);
-    return new NextResponse("Erreur lors de la récupération des préférences", { status: 500 });
+    if (error instanceof AppError) {
+      return NextResponse.json(
+        {
+          error: {
+            code: error.code,
+            message: ERROR_MESSAGES[error.code],
+          },
+        },
+        { status: 500 }
+      );
+    }
+    return NextResponse.json(
+      {
+        error: {
+          code: ERROR_CODES.PREFERENCES.FETCH_ERROR,
+          message: ERROR_MESSAGES[ERROR_CODES.PREFERENCES.FETCH_ERROR],
+        },
+      },
+      { status: 500 }
+    );
   }
 }
 
@@ -18,6 +40,25 @@ export async function PUT(request: NextRequest) {
     return NextResponse.json(updatedPreferences);
   } catch (error) {
     console.error("Erreur lors de la mise à jour des préférences:", error);
-    return new NextResponse("Erreur lors de la mise à jour des préférences", { status: 500 });
+    if (error instanceof AppError) {
+      return NextResponse.json(
+        {
+          error: {
+            code: error.code,
+            message: ERROR_MESSAGES[error.code],
+          },
+        },
+        { status: 500 }
+      );
+    }
+    return NextResponse.json(
+      {
+        error: {
+          code: ERROR_CODES.PREFERENCES.UPDATE_ERROR,
+          message: ERROR_MESSAGES[ERROR_CODES.PREFERENCES.UPDATE_ERROR],
+        },
+      },
+      { status: 500 }
+    );
   }
 }
diff --git a/src/components/auth/RegisterForm.tsx b/src/components/auth/RegisterForm.tsx
index c5c4e43..b85ed2a 100644
--- a/src/components/auth/RegisterForm.tsx
+++ b/src/components/auth/RegisterForm.tsx
@@ -4,6 +4,8 @@ import { useState } from "react";
 import { useRouter } from "next/navigation";
 import { authService } from "@/lib/services/auth.service";
 import { AuthError } from "@/types/auth";
+import { ERROR_CODES } from "@/constants/errorCodes";
+import { ERROR_MESSAGES } from "@/constants/errorMessages";
 
 interface RegisterFormProps {
   from?: string;
@@ -26,8 +28,8 @@ export function RegisterForm({ from }: RegisterFormProps) {
 
     if (password !== confirmPassword) {
       setError({
-        code: "SERVER_ERROR",
-        message: "Les mots de passe ne correspondent pas",
+        code: ERROR_CODES.AUTH.PASSWORD_MISMATCH,
+        message: ERROR_MESSAGES[ERROR_CODES.AUTH.PASSWORD_MISMATCH],
       });
       setIsLoading(false);
       return;
diff --git a/src/constants/errorCodes.ts b/src/constants/errorCodes.ts
index d50d557..b045e7f 100644
--- a/src/constants/errorCodes.ts
+++ b/src/constants/errorCodes.ts
@@ -7,8 +7,10 @@ export const ERROR_CODES = {
     UNAUTHENTICATED: "AUTH_UNAUTHENTICATED",
     INVALID_CREDENTIALS: "AUTH_INVALID_CREDENTIALS",
     PASSWORD_NOT_STRONG: "AUTH_PASSWORD_NOT_STRONG",
+    PASSWORD_MISMATCH: "AUTH_PASSWORD_MISMATCH",
     EMAIL_EXISTS: "AUTH_EMAIL_EXISTS",
     INVALID_USER_DATA: "AUTH_INVALID_USER_DATA",
+    LOGOUT_ERROR: "AUTH_LOGOUT_ERROR",
   },
   KOMGA: {
     MISSING_CONFIG: "KOMGA_MISSING_CONFIG",
@@ -54,6 +56,9 @@ export const ERROR_CODES = {
     SAVE_ERROR: "CACHE_SAVE_ERROR",
     LOAD_ERROR: "CACHE_LOAD_ERROR",
     CLEAR_ERROR: "CACHE_CLEAR_ERROR",
+    MODE_FETCH_ERROR: "CACHE_MODE_FETCH_ERROR",
+    MODE_UPDATE_ERROR: "CACHE_MODE_UPDATE_ERROR",
+    INVALID_MODE: "CACHE_INVALID_MODE",
   },
   UI: {
     TABS_TRIGGER_ERROR: "UI_TABS_TRIGGER_ERROR",
@@ -65,6 +70,16 @@ export const ERROR_CODES = {
   HOME: {
     FETCH_ERROR: "HOME_FETCH_ERROR",
   },
+  MIDDLEWARE: {
+    UNAUTHORIZED: "MIDDLEWARE_UNAUTHORIZED",
+    INVALID_TOKEN: "MIDDLEWARE_INVALID_TOKEN",
+    INVALID_SESSION: "MIDDLEWARE_INVALID_SESSION",
+  },
+  DEBUG: {
+    FETCH_ERROR: "DEBUG_FETCH_ERROR",
+    SAVE_ERROR: "DEBUG_SAVE_ERROR",
+    CLEAR_ERROR: "DEBUG_CLEAR_ERROR",
+  },
 } as const;
 
 type ValueOf<T> = T[keyof T];
diff --git a/src/constants/errorMessages.ts b/src/constants/errorMessages.ts
index a6230d0..7b78930 100644
--- a/src/constants/errorMessages.ts
+++ b/src/constants/errorMessages.ts
@@ -1,6 +1,11 @@
 import { ERROR_CODES } from "./errorCodes";
 
 export const ERROR_MESSAGES: Record<string, string> = {
+  // Middleware
+  [ERROR_CODES.MIDDLEWARE.UNAUTHORIZED]: "🚫 Accès non autorisé",
+  [ERROR_CODES.MIDDLEWARE.INVALID_TOKEN]: "🔐 Session invalide ou expirée",
+  [ERROR_CODES.MIDDLEWARE.INVALID_SESSION]: "⚠️ Données de session invalides",
+
   // MongoDB
   [ERROR_CODES.MONGODB.MISSING_URI]:
     "🔧 Veuillez définir la variable d'environnement MONGODB_URI dans votre fichier .env",
@@ -10,8 +15,10 @@ export const ERROR_MESSAGES: Record<string, string> = {
   [ERROR_CODES.AUTH.UNAUTHENTICATED]: "🔒 Utilisateur non authentifié",
   [ERROR_CODES.AUTH.INVALID_CREDENTIALS]: "⛔️ Identifiants invalides",
   [ERROR_CODES.AUTH.PASSWORD_NOT_STRONG]: "💪 Le mot de passe n'est pas assez fort",
+  [ERROR_CODES.AUTH.PASSWORD_MISMATCH]: "❌ Les mots de passe ne correspondent pas",
   [ERROR_CODES.AUTH.EMAIL_EXISTS]: "📧 Cette adresse email est déjà utilisée",
   [ERROR_CODES.AUTH.INVALID_USER_DATA]: "👤 Données utilisateur invalides",
+  [ERROR_CODES.AUTH.LOGOUT_ERROR]: "🚪 Erreur lors de la déconnexion",
 
   // Komga
   [ERROR_CODES.KOMGA.MISSING_CONFIG]: "⚙️ Configuration Komga non trouvée",
@@ -53,6 +60,9 @@ export const ERROR_MESSAGES: Record<string, string> = {
   [ERROR_CODES.CACHE.SAVE_ERROR]: "💾 Erreur lors de la sauvegarde dans le cache",
   [ERROR_CODES.CACHE.LOAD_ERROR]: "📂 Erreur lors du chargement du cache",
   [ERROR_CODES.CACHE.CLEAR_ERROR]: "🧹 Erreur lors de la suppression complète du cache",
+  [ERROR_CODES.CACHE.MODE_FETCH_ERROR]: "⚙️ Erreur lors de la récupération du mode de cache",
+  [ERROR_CODES.CACHE.MODE_UPDATE_ERROR]: "⚙️ Erreur lors de la mise à jour du mode de cache",
+  [ERROR_CODES.CACHE.INVALID_MODE]: "⚠️ Mode de cache invalide. Doit être 'file' ou 'memory'",
 
   // UI
   [ERROR_CODES.UI.TABS_TRIGGER_ERROR]: "🔄 TabsTrigger doit être utilisé dans un composant Tabs",
@@ -70,4 +80,9 @@ export const ERROR_MESSAGES: Record<string, string> = {
   [ERROR_CODES.CONFIG.FETCH_ERROR]: "⚙️ Erreur lors de la récupération de la configuration",
   [ERROR_CODES.CONFIG.TTL_SAVE_ERROR]: "⏱️ Erreur lors de la sauvegarde de la configuration TTL",
   [ERROR_CODES.CONFIG.TTL_FETCH_ERROR]: "⏱️ Erreur lors de la récupération de la configuration TTL",
+
+  // Debug
+  [ERROR_CODES.DEBUG.FETCH_ERROR]: "🔍 Erreur lors de la récupération des logs",
+  [ERROR_CODES.DEBUG.SAVE_ERROR]: "💾 Erreur lors de l'enregistrement du log",
+  [ERROR_CODES.DEBUG.CLEAR_ERROR]: "🧹 Erreur lors de la suppression des logs",
 } as const;
diff --git a/src/contexts/PreferencesContext.tsx b/src/contexts/PreferencesContext.tsx
index 4b2b378..6dc3620 100644
--- a/src/contexts/PreferencesContext.tsx
+++ b/src/contexts/PreferencesContext.tsx
@@ -1,6 +1,8 @@
 "use client";
 
 import React, { createContext, useContext, useEffect, useState } from "react";
+import { ERROR_CODES } from "../constants/errorCodes";
+import { AppError } from "../utils/errors";
 
 export interface UserPreferences {
   showThumbnails: boolean;
@@ -31,7 +33,9 @@ export function PreferencesProvider({ children }: { children: React.ReactNode })
   const fetchPreferences = async () => {
     try {
       const response = await fetch("/api/preferences");
-      if (!response.ok) throw new Error("Erreur lors de la récupération des préférences");
+      if (!response.ok) {
+        throw new AppError(ERROR_CODES.PREFERENCES.FETCH_ERROR);
+      }
       const data = await response.json();
       setPreferences({
         ...defaultPreferences,
@@ -60,7 +64,9 @@ export function PreferencesProvider({ children }: { children: React.ReactNode })
         body: JSON.stringify(newPreferences),
       });
 
-      if (!response.ok) throw new Error("Erreur lors de la mise à jour des préférences");
+      if (!response.ok) {
+        throw new AppError(ERROR_CODES.PREFERENCES.UPDATE_ERROR);
+      }
 
       const updatedPreferences = await response.json();
 
@@ -89,7 +95,7 @@ export function PreferencesProvider({ children }: { children: React.ReactNode })
 export function usePreferences() {
   const context = useContext(PreferencesContext);
   if (context === undefined) {
-    throw new Error("usePreferences must be used within a PreferencesProvider");
+    throw new AppError(ERROR_CODES.PREFERENCES.CONTEXT_ERROR);
   }
   return context;
 }
diff --git a/src/lib/registerSW.ts b/src/lib/registerSW.ts
index 34b7cec..3dee270 100644
--- a/src/lib/registerSW.ts
+++ b/src/lib/registerSW.ts
@@ -4,8 +4,8 @@ export const registerServiceWorker = async () => {
   }
 
   try {
-    const registration = await navigator.serviceWorker.register("/sw.js");
-    console.log("Service Worker registered with scope:", registration.scope);
+    await navigator.serviceWorker.register("/sw.js");
+    // console.log("Service Worker registered with scope:", registration.scope);
   } catch (error) {
     console.error("Service Worker registration failed:", error);
   }
diff --git a/src/lib/services/auth.service.ts b/src/lib/services/auth.service.ts
index d1b7f96..549b617 100644
--- a/src/lib/services/auth.service.ts
+++ b/src/lib/services/auth.service.ts
@@ -1,6 +1,8 @@
 "use client";
 
 import { AuthError } from "@/types/auth";
+import { ERROR_CODES } from "@/constants/errorCodes";
+import { ERROR_MESSAGES } from "@/constants/errorMessages";
 
 class AuthService {
   private static instance: AuthService;
@@ -39,8 +41,8 @@ class AuthService {
         throw error;
       }
       throw {
-        code: "SERVER_ERROR",
-        message: "Une erreur est survenue lors de la connexion",
+        code: ERROR_CODES.AUTH.INVALID_CREDENTIALS,
+        message: ERROR_MESSAGES[ERROR_CODES.AUTH.INVALID_CREDENTIALS],
       } as AuthError;
     }
   }
@@ -67,8 +69,8 @@ class AuthService {
         throw error;
       }
       throw {
-        code: "SERVER_ERROR",
-        message: "Une erreur est survenue lors de l'inscription",
+        code: ERROR_CODES.AUTH.INVALID_USER_DATA,
+        message: ERROR_MESSAGES[ERROR_CODES.AUTH.INVALID_USER_DATA],
       } as AuthError;
     }
   }
@@ -77,9 +79,24 @@ class AuthService {
    * Déconnecte l'utilisateur
    */
   async logout(): Promise<void> {
-    await fetch("/api/auth/logout", {
-      method: "POST",
-    });
+    try {
+      const response = await fetch("/api/auth/logout", {
+        method: "POST",
+      });
+
+      if (!response.ok) {
+        const data = await response.json();
+        throw data.error;
+      }
+    } catch (error) {
+      if ((error as AuthError).code) {
+        throw error;
+      }
+      throw {
+        code: ERROR_CODES.AUTH.LOGOUT_ERROR,
+        message: ERROR_MESSAGES[ERROR_CODES.AUTH.LOGOUT_ERROR],
+      } as AuthError;
+    }
   }
 }
 
diff --git a/src/middleware.ts b/src/middleware.ts
index af8f6af..9a4029f 100644
--- a/src/middleware.ts
+++ b/src/middleware.ts
@@ -1,5 +1,7 @@
 import { NextResponse } from "next/server";
 import type { NextRequest } from "next/server";
+import { ERROR_CODES } from "./constants/errorCodes";
+import { ERROR_MESSAGES } from "./constants/errorMessages";
 
 // Routes qui ne nécessitent pas d'authentification
 const publicRoutes = ["/login", "/register", "/images"];
@@ -30,7 +32,10 @@ export function middleware(request: NextRequest) {
   // Pour toutes les routes protégées, vérifier la présence de l'utilisateur
   if (!user || !user.value) {
     if (pathname.startsWith("/api/")) {
-      return NextResponse.json({ error: "Non autorisé" }, { status: 401 });
+      return NextResponse.json(
+        { error: ERROR_MESSAGES[ERROR_CODES.MIDDLEWARE.UNAUTHORIZED] },
+        { status: 401 }
+      );
     }
     const loginUrl = new URL("/login", request.url);
     loginUrl.searchParams.set("from", pathname);
@@ -40,12 +45,15 @@ export function middleware(request: NextRequest) {
   try {
     const userData = JSON.parse(atob(user.value));
     if (!userData || !userData.authenticated || !userData.id || !userData.email) {
-      throw new Error("Invalid user data");
+      throw new Error(ERROR_MESSAGES[ERROR_CODES.MIDDLEWARE.INVALID_SESSION]);
     }
   } catch (error) {
     console.error("Erreur de validation du cookie:", error);
     if (pathname.startsWith("/api/")) {
-      return NextResponse.json({ error: "Non autorisé" }, { status: 401 });
+      return NextResponse.json(
+        { error: ERROR_MESSAGES[ERROR_CODES.MIDDLEWARE.INVALID_TOKEN] },
+        { status: 401 }
+      );
     }
     const loginUrl = new URL("/login", request.url);
     loginUrl.searchParams.set("from", pathname);
diff --git a/src/types/auth.ts b/src/types/auth.ts
index ae98dfd..2df8363 100644
--- a/src/types/auth.ts
+++ b/src/types/auth.ts
@@ -1,4 +1,5 @@
 import { KomgaUser } from "./komga";
+import { ErrorCode } from "@/constants/errorCodes";
 
 export interface AuthConfig {
   serverUrl: string;
@@ -12,8 +13,9 @@ export interface AuthState {
 }
 
 export interface AuthError {
-  code: AuthErrorCode;
+  code: ErrorCode;
   message: string;
 }
 
-export type AuthErrorCode = "INVALID_CREDENTIALS" | "SERVER_ERROR" | "EMAIL_EXISTS";
+// Deprecated - Use ErrorCode from @/constants/errorCodes instead
+export type AuthErrorCode = ErrorCode;