perf: optimize Komga caching with unstable_cache for POST requests and reduce API calls

- Fix POST requests (series/list, books/list) not being cached by Next.js fetch cache
  by wrapping them with unstable_cache in the private fetch method
- Wrap getHomeData() entirely with unstable_cache so all 5 home requests are cached
  as a single unit, reducing cold-start cost from 5 parallel calls to 0 on cache hit
- Remove N+1 book count enrichment from getLibraries() (8 extra calls per cold start)
  as LibraryDto does not return booksCount and the value was only used in BackgroundSettings
- Simplify getLibraryById() to reuse cached getLibraries() data instead of making
  separate HTTP calls (saves 2 calls per library page load)
- Fix cache debug logs: replace misleading x-nextjs-cache header check (always UNKNOWN
  on external APIs) with pre-request logs showing the configured cache strategy
- Remove book count display from BackgroundSettings as it is no longer fetched

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/app/actions/config.ts

@@ -38,7 +38,7 @@ export async function testKomgaConnection(
       message: `Connexion réussie ! ${libraries.length} bibliothèque${libraries.length > 1 ? "s" : ""} trouvée${libraries.length > 1 ? "s" : ""}`,
     };
   } catch (error) {
-    if (error instanceof AppError) {
+if (error instanceof AppError) {
       return { success: false, message: error.message };
     }
     return { success: false, message: "Erreur lors de la connexion" };
@@ -59,7 +59,7 @@ export async function saveKomgaConfig(
     revalidatePath("/settings");
     return { success: true, message: "Configuration sauvegardée", data: mongoConfig };
   } catch (error) {
-    if (error instanceof AppError) {
+if (error instanceof AppError) {
       return { success: false, message: error.message };
     }
     return { success: false, message: "Erreur lors de la sauvegarde" };

src/components/settings/BackgroundSettings.tsx

@@ -278,7 +278,7 @@ export function BackgroundSettings({ initialLibraries }: BackgroundSettingsProps
                       htmlFor={`lib-${library.id}`}
                       className="cursor-pointer font-normal text-sm"
                     >
-                      {library.name} ({library.bookCount} livres)
+                      {library.name}
                     </Label>
                   </div>
                 ))}

src/components/settings/KomgaSettings.tsx

@@ -34,14 +34,8 @@ export function KomgaSettings({ initialConfig }: KomgaSettingsProps) {
   const handleTest = async () => {
     setIsLoading(true);
 
-    const form = document.querySelector("form") as HTMLFormElement;
-    const formData = new FormData(form);
-    const serverUrl = formData.get("serverUrl") as string;
-    const username = formData.get("username") as string;
-    const password = formData.get("password") as string;
-
     try {
-      const result = await testKomgaConnection(serverUrl.trim(), username, password || config.password);
+      const result = await testKomgaConnection(config.serverUrl.trim(), config.username, config.password);
 
       if (!result.success) {
         throw new Error(result.message);
@@ -55,8 +49,8 @@ export function KomgaSettings({ initialConfig }: KomgaSettingsProps) {
       logger.error({ err: error }, "Erreur:");
       toast({
         variant: "destructive",
-        title: t("settings.komga.error.title"),
-        description: t("settings.komga.error.message"),
+        title: t("settings.komga.error.connectionTitle"),
+        description: t("settings.komga.error.connectionMessage"),
       });
     } finally {
       setIsLoading(false);

src/i18n/messages/en/common.json

@@ -134,7 +134,9 @@
       },
       "error": {
         "title": "Error saving configuration",
-        "message": "An error occurred while saving the configuration"
+        "message": "An error occurred while saving the configuration",
+        "connectionTitle": "Connection error",
+        "connectionMessage": "Unable to connect to the Komga server. Check the URL and credentials."
       }
     },
     "cache": {
@@ -361,7 +363,6 @@
   "errors": {
     "MONGODB_MISSING_URI": "MongoDB URI missing",
     "MONGODB_CONNECTION_FAILED": "MongoDB connection failed",
-
     "AUTH_UNAUTHENTICATED": "Unauthenticated",
     "AUTH_INVALID_CREDENTIALS": "Invalid credentials",
     "AUTH_PASSWORD_NOT_STRONG": "Password is not strong enough",
@@ -371,7 +372,6 @@
     "AUTH_LOGOUT_ERROR": "Error during logout",
     "AUTH_LOGIN_ERROR": "Error during login",
     "AUTH_REGISTER_ERROR": "Error during registration",
-
     "KOMGA_MISSING_CONFIG": "Komga configuration missing",
     "KOMGA_MISSING_CREDENTIALS": "Komga credentials missing",
     "KOMGA_CONNECTION_ERROR": "Error connecting to Komga server",
@@ -380,25 +380,20 @@
     "STRIPSTREAM_MISSING_CONFIG": "Stripstream Librarian configuration missing",
     "STRIPSTREAM_CONNECTION_ERROR": "Error connecting to Stripstream Librarian",
     "STRIPSTREAM_HTTP_ERROR": "HTTP error while communicating with Stripstream Librarian",
-
     "CONFIG_SAVE_ERROR": "Error saving configuration",
     "CONFIG_FETCH_ERROR": "Error fetching configuration",
     "CONFIG_TTL_SAVE_ERROR": "Error saving TTL configuration",
     "CONFIG_TTL_FETCH_ERROR": "Error fetching TTL configuration",
-
     "LIBRARY_NOT_FOUND": "Library not found",
     "LIBRARY_FETCH_ERROR": "Error fetching library",
     "LIBRARY_SCAN_ERROR": "Error scanning library",
-
     "SERIES_FETCH_ERROR": "Error fetching series",
     "SERIES_NO_BOOKS_FOUND": "No books found in series",
-
     "BOOK_NOT_FOUND": "Book not found",
     "BOOK_PROGRESS_UPDATE_ERROR": "Error updating reading progress",
     "BOOK_PROGRESS_DELETE_ERROR": "Error deleting reading progress",
     "BOOK_PAGES_FETCH_ERROR": "Error fetching book pages",
     "BOOK_DOWNLOAD_CANCELLED": "Book download cancelled",
-
     "FAVORITE_ADD_ERROR": "Error adding to favorites",
     "FAVORITE_DELETE_ERROR": "Error removing from favorites",
     "FAVORITE_FETCH_ERROR": "Error fetching favorites",
@@ -406,26 +401,19 @@
     "FAVORITE_NETWORK_ERROR": "Network error while accessing favorites",
     "FAVORITE_SERVER_ERROR": "Server error while accessing favorites",
     "FAVORITE_STATUS_CHECK_ERROR": "Error checking favorites status",
-
     "PREFERENCES_FETCH_ERROR": "Error fetching preferences",
     "PREFERENCES_UPDATE_ERROR": "Error updating preferences",
     "PREFERENCES_CONTEXT_ERROR": "Preferences context error",
-
     "UI_TABS_TRIGGER_ERROR": "Error triggering tabs",
     "UI_TABS_CONTENT_ERROR": "Error loading tabs content",
-
     "IMAGE_FETCH_ERROR": "Error fetching image",
-
     "HOME_FETCH_ERROR": "Error fetching home page",
-
     "MIDDLEWARE_UNAUTHORIZED": "Unauthorized",
     "MIDDLEWARE_INVALID_TOKEN": "Invalid authentication token",
     "MIDDLEWARE_INVALID_SESSION": "Invalid session",
-
     "CLIENT_FETCH_ERROR": "Error fetching data",
     "CLIENT_NETWORK_ERROR": "Network error",
     "CLIENT_REQUEST_FAILED": "Request failed",
-
     "GENERIC_ERROR": "An error occurred"
   },
   "reader": {

src/i18n/messages/fr/common.json

@@ -134,7 +134,9 @@
       },
       "error": {
         "title": "Erreur lors de la sauvegarde de la configuration",
-        "message": "Une erreur est survenue lors de la sauvegarde de la configuration"
+        "message": "Une erreur est survenue lors de la sauvegarde de la configuration",
+        "connectionTitle": "Erreur de connexion",
+        "connectionMessage": "Impossible de se connecter au serveur Komga. Vérifiez l'URL et les identifiants."
       }
     },
     "cache": {
@@ -359,7 +361,6 @@
   "errors": {
     "MONGODB_MISSING_URI": "URI MongoDB manquante",
     "MONGODB_CONNECTION_FAILED": "Erreur lors de la connexion à MongoDB",
-
     "AUTH_UNAUTHENTICATED": "Non authentifié",
     "AUTH_INVALID_CREDENTIALS": "Identifiants invalides",
     "AUTH_PASSWORD_NOT_STRONG": "Le mot de passe n'est pas assez fort",
@@ -369,7 +370,6 @@
     "AUTH_LOGOUT_ERROR": "Erreur lors de la déconnexion",
     "AUTH_LOGIN_ERROR": "Erreur lors de la connexion",
     "AUTH_REGISTER_ERROR": "Erreur lors de l'inscription",
-
     "KOMGA_MISSING_CONFIG": "Configuration Komga manquante",
     "KOMGA_MISSING_CREDENTIALS": "Identifiants Komga manquants",
     "KOMGA_CONNECTION_ERROR": "Erreur de connexion au serveur Komga",
@@ -378,25 +378,20 @@
     "STRIPSTREAM_MISSING_CONFIG": "Configuration Stripstream Librarian manquante",
     "STRIPSTREAM_CONNECTION_ERROR": "Erreur de connexion à Stripstream Librarian",
     "STRIPSTREAM_HTTP_ERROR": "Erreur HTTP lors de la communication avec Stripstream Librarian",
-
     "CONFIG_SAVE_ERROR": "Erreur lors de la sauvegarde de la configuration",
     "CONFIG_FETCH_ERROR": "Erreur lors de la récupération de la configuration",
     "CONFIG_TTL_SAVE_ERROR": "Erreur lors de la sauvegarde des TTL",
     "CONFIG_TTL_FETCH_ERROR": "Erreur lors de la récupération des TTL",
-
     "LIBRARY_NOT_FOUND": "Bibliothèque introuvable",
     "LIBRARY_FETCH_ERROR": "Erreur lors de la récupération de la bibliothèque",
     "LIBRARY_SCAN_ERROR": "Erreur lors de l'analyse de la bibliothèque",
-
     "SERIES_FETCH_ERROR": "Erreur lors de la récupération des séries",
     "SERIES_NO_BOOKS_FOUND": "Aucun livre trouvé dans la série",
-
     "BOOK_NOT_FOUND": "Livre introuvable",
     "BOOK_PROGRESS_UPDATE_ERROR": "Erreur lors de la mise à jour de la progression",
     "BOOK_PROGRESS_DELETE_ERROR": "Erreur lors de la suppression de la progression",
     "BOOK_PAGES_FETCH_ERROR": "Erreur lors de la récupération des pages du livre",
     "BOOK_DOWNLOAD_CANCELLED": "Téléchargement du livre annulé",
-
     "FAVORITE_ADD_ERROR": "Erreur lors de l'ajout aux favoris",
     "FAVORITE_DELETE_ERROR": "Erreur lors de la suppression des favoris",
     "FAVORITE_FETCH_ERROR": "Erreur lors de la récupération des favoris",
@@ -404,26 +399,19 @@
     "FAVORITE_NETWORK_ERROR": "Erreur réseau lors de l'accès aux favoris",
     "FAVORITE_SERVER_ERROR": "Erreur serveur lors de l'accès aux favoris",
     "FAVORITE_STATUS_CHECK_ERROR": "Erreur lors de la vérification du statut des favoris",
-
     "PREFERENCES_FETCH_ERROR": "Erreur lors de la récupération des préférences",
     "PREFERENCES_UPDATE_ERROR": "Erreur lors de la mise à jour des préférences",
     "PREFERENCES_CONTEXT_ERROR": "Erreur de contexte des préférences",
-
     "UI_TABS_TRIGGER_ERROR": "Erreur lors du déclenchement des onglets",
     "UI_TABS_CONTENT_ERROR": "Erreur lors du chargement du contenu des onglets",
-
     "IMAGE_FETCH_ERROR": "Erreur lors de la récupération de l'image",
-
     "HOME_FETCH_ERROR": "Erreur lors de la récupération de l'accueil",
-
     "MIDDLEWARE_UNAUTHORIZED": "Non autorisé",
     "MIDDLEWARE_INVALID_TOKEN": "Jeton d'authentification invalide",
     "MIDDLEWARE_INVALID_SESSION": "Session invalide",
-
     "CLIENT_FETCH_ERROR": "Erreur lors de la récupération des données",
     "CLIENT_NETWORK_ERROR": "Erreur réseau",
     "CLIENT_REQUEST_FAILED": "La requête a échoué",
-
     "GENERIC_ERROR": "Une erreur est survenue"
   },
   "reader": {

src/lib/providers/komga/komga.provider.ts

@@ -17,6 +17,7 @@ import type { LibraryResponse } from "@/types/library";
 import type { AuthConfig } from "@/types/auth";
 import logger from "@/lib/logger";
 import { HOME_CACHE_TAG, LIBRARY_SERIES_CACHE_TAG, SERIES_BOOKS_CACHE_TAG } from "@/constants/cacheConstants";
+import { unstable_cache } from "next/cache";
 
 type KomgaCondition = Record<string, unknown>;
 
@@ -64,7 +65,6 @@ export class KomgaProvider implements IMediaProvider {
 
     const isDebug = process.env.KOMGA_DEBUG === "true";
     const isCacheDebug = process.env.CACHE_DEBUG === "true";
-    const startTime = isDebug ? Date.now() : 0;
 
     if (isDebug) {
       logger.info(
@@ -72,8 +72,14 @@ export class KomgaProvider implements IMediaProvider {
         "🔵 Komga Request"
       );
     }
-    if (isCacheDebug && options.revalidate) {
-      logger.info({ url, cache: "enabled", ttl: options.revalidate }, "💾 Cache enabled");
+    if (isCacheDebug) {
+      if (options.tags) {
+        logger.info({ url, cache: "tags", tags: options.tags }, "💾 Cache tags");
+      } else if (options.revalidate !== undefined) {
+        logger.info({ url, cache: "revalidate", ttl: options.revalidate }, "💾 Cache revalidate");
+      } else {
+        logger.info({ url, cache: "none" }, "💾 Cache none");
+      }
     }
 
     const nextOptions = options.tags
@@ -88,6 +94,19 @@ export class KomgaProvider implements IMediaProvider {
       next: nextOptions,
     };
 
+    // Next.js does not cache POST fetch requests — use unstable_cache to cache results instead
+    if (options.method === "POST" && nextOptions) {
+      const cacheKey = ["komga", this.config.authHeader, url, String(options.body ?? "")];
+      return unstable_cache(() => this.executeRequest<T>(url, fetchOptions), cacheKey, nextOptions)();
+    }
+
+    return this.executeRequest<T>(url, fetchOptions);
+  }
+
+  private async executeRequest<T>(url: string, fetchOptions: RequestInit): Promise<T> {
+    const isDebug = process.env.KOMGA_DEBUG === "true";
+    const startTime = isDebug ? Date.now() : 0;
+
     const controller = new AbortController();
     const timeoutId = setTimeout(() => controller.abort(), TIMEOUT_MS);
 
@@ -124,10 +143,6 @@ export class KomgaProvider implements IMediaProvider {
           "🟢 Komga Response"
         );
       }
-      if (isCacheDebug && options.revalidate) {
-        const cacheStatus = response.headers.get("x-nextjs-cache") ?? "UNKNOWN";
-        logger.info({ url, cacheStatus }, `💾 Cache ${cacheStatus}`);
-      }
 
       if (!response.ok) {
         if (isDebug) {
@@ -163,25 +178,7 @@ export class KomgaProvider implements IMediaProvider {
     const raw = await this.fetch<KomgaLibrary[]>("libraries", undefined, {
       revalidate: CACHE_TTL_LONG,
     });
-    // Enrich with book counts
-    const enriched = await Promise.all(
-      raw.map(async (lib) => {
-        try {
-          const resp = await this.fetch<{ totalElements: number }>(
-            "books",
-            {
-              library_id: lib.id,
-              size: "0",
-            },
-            { revalidate: CACHE_TTL_LONG }
-          );
-          return { ...lib, booksCount: resp.totalElements, booksReadCount: 0 } as KomgaLibrary;
-        } catch {
-          return { ...lib, booksCount: 0, booksReadCount: 0 } as KomgaLibrary;
-        }
-      })
-    );
-    return enriched.map(KomgaAdapter.toNormalizedLibrary);
+    return raw.map(KomgaAdapter.toNormalizedLibrary);
   }
 
   async getSeries(libraryId: string, cursor?: string, limit = 20, unreadOnly = false, search?: string): Promise<NormalizedSeriesPage> {
@@ -356,30 +353,8 @@ export class KomgaProvider implements IMediaProvider {
   }
 
   async getLibraryById(libraryId: string): Promise<NormalizedLibrary | null> {
-    try {
-      const lib = await this.fetch<KomgaLibrary>(`libraries/${libraryId}`, undefined, {
-        revalidate: CACHE_TTL_LONG,
-      });
-      try {
-        const resp = await this.fetch<{ totalElements: number }>(
-          "books",
-          {
-            library_id: lib.id,
-            size: "0",
-          },
-          { revalidate: CACHE_TTL_LONG }
-        );
-        return KomgaAdapter.toNormalizedLibrary({
-          ...lib,
-          booksCount: resp.totalElements,
-          booksReadCount: 0,
-        });
-      } catch {
-        return KomgaAdapter.toNormalizedLibrary({ ...lib, booksCount: 0, booksReadCount: 0 });
-      }
-    } catch {
-      return null;
-    }
+    const libraries = await this.getLibraries();
+    return libraries.find((lib) => lib.id === libraryId) ?? null;
   }
 
   async getNextBook(bookId: string): Promise<NormalizedBook | null> {
@@ -398,7 +373,14 @@ export class KomgaProvider implements IMediaProvider {
   }
 
   async getHomeData(): Promise<HomeData> {
-    const homeOpts = { revalidate: CACHE_TTL_MED, tags: [HOME_CACHE_TAG] };
+    return unstable_cache(
+      () => this.fetchHomeData(),
+      ["komga-home", this.config.authHeader],
+      { revalidate: CACHE_TTL_MED, tags: [HOME_CACHE_TAG] }
+    )();
+  }
+
+  private async fetchHomeData(): Promise<HomeData> {
     const [ongoing, ongoingBooks, recentlyRead, onDeck, latestSeries] = await Promise.all([
       this.fetch<LibraryResponse<KomgaSeries>>(
         "series/list",
@@ -408,7 +390,6 @@ export class KomgaProvider implements IMediaProvider {
           body: JSON.stringify({
             condition: { readStatus: { operator: "is", value: "IN_PROGRESS" } },
           }),
-          ...homeOpts,
         }
       ).catch(() => ({ content: [] as KomgaSeries[] })),
       this.fetch<LibraryResponse<KomgaBook>>(
@@ -419,23 +400,19 @@ export class KomgaProvider implements IMediaProvider {
           body: JSON.stringify({
             condition: { readStatus: { operator: "is", value: "IN_PROGRESS" } },
           }),
-          ...homeOpts,
         }
       ).catch(() => ({ content: [] as KomgaBook[] })),
       this.fetch<LibraryResponse<KomgaBook>>(
         "books/latest",
-        { page: "0", size: "10", media_status: "READY" },
-        { ...homeOpts }
+        { page: "0", size: "10", media_status: "READY" }
       ).catch(() => ({ content: [] as KomgaBook[] })),
       this.fetch<LibraryResponse<KomgaBook>>(
         "books/ondeck",
-        { page: "0", size: "10", media_status: "READY" },
-        { ...homeOpts }
+        { page: "0", size: "10", media_status: "READY" }
       ).catch(() => ({ content: [] as KomgaBook[] })),
       this.fetch<LibraryResponse<KomgaSeries>>(
         "series/latest",
-        { page: "0", size: "10", media_status: "READY" },
-        { ...homeOpts }
+        { page: "0", size: "10", media_status: "READY" }
       ).catch(() => ({ content: [] as KomgaSeries[] })),
     ]);
     return {

src/lib/providers/stripstream/stripstream.client.ts

@@ -59,8 +59,14 @@ export class StripstreamClient {
         "🔵 Stripstream Request"
       );
     }
-    if (isCacheDebug && options.revalidate) {
-      logger.info({ url, cache: "enabled", ttl: options.revalidate }, "💾 Cache enabled");
+    if (isCacheDebug) {
+      if (options.tags) {
+        logger.info({ url, cache: "tags", tags: options.tags }, "💾 Cache tags");
+      } else if (options.revalidate !== undefined) {
+        logger.info({ url, cache: "revalidate", ttl: options.revalidate }, "💾 Cache revalidate");
+      } else {
+        logger.info({ url, cache: "none" }, "💾 Cache none");
+      }
     }
 
     const nextOptions = options.tags
@@ -106,10 +112,6 @@ export class StripstreamClient {
           "🟢 Stripstream Response"
         );
       }
-      if (isCacheDebug && options.revalidate) {
-        const cacheStatus = response.headers.get("x-nextjs-cache") ?? "UNKNOWN";
-        logger.info({ url, cacheStatus }, `💾 Cache ${cacheStatus}`);
-      }
 
       if (!response.ok) {
         if (isDebug) {

src/lib/services/config-db.service.ts

@@ -39,7 +39,7 @@ export class ConfigDBService {
 
       return config as KomgaConfig;
     } catch (error) {
-      if (error instanceof AppError) {
+if (error instanceof AppError) {
         throw error;
       }
       throw new AppError(ERROR_CODES.CONFIG.SAVE_ERROR, {}, error);