diff --git a/docker-compose.yml b/docker-compose.yml
index ebcdfa1..46d108f 100644
--- a/docker-compose.yml
+++ b/docker-compose.yml
@@ -49,6 +49,15 @@ services:
       PUID: 1000
       PGID: 1000
 
+      # ========================================================================
+      # OPTIONAL: File Permission Mask
+      # ========================================================================
+      # Set a umask to control default file permissions for all files created
+      # by the application. Common values:
+      # - 002: Group-writable (files: 664, dirs: 775) - recommended for shared access
+      # - 022: Group-readable only (files: 644, dirs: 755) - more restrictive
+      # UMASK: "002"
+
       # ========================================================================
       # OPTIONAL: Secrets (auto-generated on first run if not provided)
       # ========================================================================
diff --git a/docker/unified/app-start.sh b/docker/unified/app-start.sh
index ebf9b74..e3ffcc4 100644
--- a/docker/unified/app-start.sh
+++ b/docker/unified/app-start.sh
@@ -22,6 +22,12 @@ PGID=${PGID:-$(id -g node)}
 echo "[App] Starting Next.js server..."
 echo "[App] Process will run as UID:GID = $PUID:$PGID"
 
+# Apply UMASK if set (controls default file permissions)
+if [ -n "$UMASK" ]; then
+    echo "[App] Applying umask: $UMASK"
+    umask "$UMASK"
+fi
+
 cd /app
 
 # =============================================================================
diff --git a/docker/unified/entrypoint.sh b/docker/unified/entrypoint.sh
index 76fb8c2..7bd08fe 100644
--- a/docker/unified/entrypoint.sh
+++ b/docker/unified/entrypoint.sh
@@ -387,6 +387,7 @@ PORT=$PORT
 HOSTNAME=$HOSTNAME
 PUID=${PUID:-}
 PGID=${PGID:-}
+UMASK=${UMASK:-}
 ROOTLESS_CONTAINER=${ROOTLESS_CONTAINER:-}
 EOF
 
diff --git a/src/app/admin/settings/lib/types.ts b/src/app/admin/settings/lib/types.ts
index bbb4070..264c374 100644
--- a/src/app/admin/settings/lib/types.ts
+++ b/src/app/admin/settings/lib/types.ts
@@ -102,6 +102,8 @@ export interface PathsSettings {
   chapterMergingEnabled: boolean;
   fileRenameEnabled: boolean;
   fileRenameTemplate?: string;
+  fileChmod?: string;
+  dirChmod?: string;
 }
 
 /**
diff --git a/src/app/admin/settings/tabs/PathsTab/PathsTab.tsx b/src/app/admin/settings/tabs/PathsTab/PathsTab.tsx
index d1f3646..a1000f9 100644
--- a/src/app/admin/settings/tabs/PathsTab/PathsTab.tsx
+++ b/src/app/admin/settings/tabs/PathsTab/PathsTab.tsx
@@ -439,6 +439,54 @@ export function PathsTab({ paths, onChange, onValidationChange }: PathsTabProps)
         </div>
       </div>
 
+      {/* File Permissions */}
+      <div className="bg-gray-50 dark:bg-gray-800 rounded-lg p-4 border border-gray-200 dark:border-gray-700">
+        <h3 className="text-sm font-semibold text-gray-900 dark:text-gray-100 mb-3">
+          File Permissions
+        </h3>
+        <p className="text-sm text-gray-600 dark:text-gray-400 mb-4">
+          Octal permissions applied when organizing files into the media library. These may be further restricted by the container&apos;s UMASK setting.
+        </p>
+        <div className="grid grid-cols-1 sm:grid-cols-2 gap-4">
+          <div>
+            <label className="block text-sm font-medium text-gray-700 dark:text-gray-300 mb-2">
+              File Permissions
+            </label>
+            <Input
+              type="text"
+              value={paths.fileChmod || '664'}
+              onChange={(e) => updatePath('fileChmod', e.target.value)}
+              placeholder="664"
+              className={`font-mono max-w-32 ${paths.fileChmod && !/^[0-7]{3,4}$/.test(paths.fileChmod) ? 'border-red-500 dark:border-red-500' : ''}`}
+            />
+            {paths.fileChmod && !/^[0-7]{3,4}$/.test(paths.fileChmod) && (
+              <p className="text-xs text-red-600 dark:text-red-400 mt-1">Must be 3-4 octal digits (0-7)</p>
+            )}
+            <p className="text-xs text-gray-500 dark:text-gray-400 mt-1">
+              e.g. 664 = owner/group read-write, others read
+            </p>
+          </div>
+          <div>
+            <label className="block text-sm font-medium text-gray-700 dark:text-gray-300 mb-2">
+              Directory Permissions
+            </label>
+            <Input
+              type="text"
+              value={paths.dirChmod || '775'}
+              onChange={(e) => updatePath('dirChmod', e.target.value)}
+              placeholder="775"
+              className={`font-mono max-w-32 ${paths.dirChmod && !/^[0-7]{3,4}$/.test(paths.dirChmod) ? 'border-red-500 dark:border-red-500' : ''}`}
+            />
+            {paths.dirChmod && !/^[0-7]{3,4}$/.test(paths.dirChmod) && (
+              <p className="text-xs text-red-600 dark:text-red-400 mt-1">Must be 3-4 octal digits (0-7)</p>
+            )}
+            <p className="text-xs text-gray-500 dark:text-gray-400 mt-1">
+              e.g. 775 = owner/group full access, others read-execute
+            </p>
+          </div>
+        </div>
+      </div>
+
       {/* Test Paths Button */}
       <div className="border-t border-gray-200 dark:border-gray-700 pt-6">
         <Button
diff --git a/src/app/api/admin/settings/paths/route.ts b/src/app/api/admin/settings/paths/route.ts
index b7e4337..9683702 100644
--- a/src/app/api/admin/settings/paths/route.ts
+++ b/src/app/api/admin/settings/paths/route.ts
@@ -15,7 +15,7 @@ export async function PUT(request: NextRequest) {
   return requireAuth(request, async (req: AuthenticatedRequest) => {
     return requireAdmin(req, async () => {
       try {
-        const { downloadDir, mediaDir, audiobookPathTemplate, ebookPathTemplate, metadataTaggingEnabled, chapterMergingEnabled, fileRenameEnabled, fileRenameTemplate } = await request.json();
+        const { downloadDir, mediaDir, audiobookPathTemplate, ebookPathTemplate, metadataTaggingEnabled, chapterMergingEnabled, fileRenameEnabled, fileRenameTemplate, fileChmod, dirChmod } = await request.json();
 
         if (!downloadDir || !mediaDir) {
           return NextResponse.json(
@@ -32,6 +32,21 @@ export async function PUT(request: NextRequest) {
           );
         }
 
+        // Validate octal permission strings (3-4 digits, each 0-7)
+        const octalRegex = /^[0-7]{3,4}$/;
+        if (fileChmod !== undefined && !octalRegex.test(fileChmod)) {
+          return NextResponse.json(
+            { error: 'File permissions must be 3-4 octal digits (0-7), e.g. 664' },
+            { status: 400 }
+          );
+        }
+        if (dirChmod !== undefined && !octalRegex.test(dirChmod)) {
+          return NextResponse.json(
+            { error: 'Directory permissions must be 3-4 octal digits (0-7), e.g. 775' },
+            { status: 400 }
+          );
+        }
+
         // Update configuration
         await prisma.configuration.upsert({
           where: { key: 'download_dir' },
@@ -123,6 +138,34 @@ export async function PUT(request: NextRequest) {
           });
         }
 
+        // Update file permissions (octal chmod)
+        if (fileChmod !== undefined) {
+          await prisma.configuration.upsert({
+            where: { key: 'file_chmod' },
+            update: { value: fileChmod },
+            create: {
+              key: 'file_chmod',
+              value: fileChmod,
+              category: 'automation',
+              description: 'Octal permissions applied to organized files',
+            },
+          });
+        }
+
+        // Update directory permissions (octal chmod)
+        if (dirChmod !== undefined) {
+          await prisma.configuration.upsert({
+            where: { key: 'dir_chmod' },
+            update: { value: dirChmod },
+            create: {
+              key: 'dir_chmod',
+              value: dirChmod,
+              category: 'automation',
+              description: 'Octal permissions applied to created directories',
+            },
+          });
+        }
+
         logger.info('Paths settings updated');
 
         // Clear config cache for all updated keys so services get fresh values
@@ -135,6 +178,8 @@ export async function PUT(request: NextRequest) {
         configService.clearCache('chapter_merging_enabled');
         configService.clearCache('file_rename_enabled');
         configService.clearCache('file_rename_template');
+        configService.clearCache('file_chmod');
+        configService.clearCache('dir_chmod');
 
         // Invalidate all download client singletons to force reload of download_dir
         const { invalidateDownloadClientManager } = await import('@/lib/services/download-client-manager.service');
diff --git a/src/app/api/admin/settings/route.ts b/src/app/api/admin/settings/route.ts
index 550caed..3298e1e 100644
--- a/src/app/api/admin/settings/route.ts
+++ b/src/app/api/admin/settings/route.ts
@@ -130,6 +130,8 @@ export async function GET(request: NextRequest) {
         chapterMergingEnabled: configMap.get('chapter_merging_enabled') === 'true',
         fileRenameEnabled: configMap.get('file_rename_enabled') === 'true',
         fileRenameTemplate: configMap.get('file_rename_template') || '{title}',
+        fileChmod: configMap.get('file_chmod') || '664',
+        dirChmod: configMap.get('dir_chmod') || '775',
       },
       ebook: {
         // New granular source toggles (with migration from legacy ebook_sidecar_enabled)
diff --git a/src/lib/processors/direct-download.processor.ts b/src/lib/processors/direct-download.processor.ts
index d8296d2..f6ab7bf 100644
--- a/src/lib/processors/direct-download.processor.ts
+++ b/src/lib/processors/direct-download.processor.ts
@@ -289,8 +289,11 @@ async function downloadFileWithProgress(
   logger: RMABLogger
 ): Promise<boolean> {
   try {
-    // Ensure target directory exists
-    await fs.mkdir(path.dirname(targetPath), { recursive: true });
+    // Ensure target directory exists with configured permissions
+    const configService = getConfigService();
+    const dirChmodStr = await configService.get('dir_chmod') || '775';
+    const dirMode = parseInt(dirChmodStr, 8);
+    await fs.mkdir(path.dirname(targetPath), { recursive: true, mode: dirMode });
 
     // Start download with axios streaming
     const response = await axios({
diff --git a/src/lib/utils/chapter-merger.ts b/src/lib/utils/chapter-merger.ts
index c422977..c3b9fbe 100644
--- a/src/lib/utils/chapter-merger.ts
+++ b/src/lib/utils/chapter-merger.ts
@@ -62,6 +62,7 @@ export interface MergeOptions {
   year?: number;
   asin?: string;
   outputPath: string;
+  dirMode?: number;
 }
 
 export interface MergeResult {
@@ -616,7 +617,7 @@ export async function mergeChapters(
     await logger?.info(`✓ All ${chapters.length} source files validated`);
 
     // Ensure temp directory exists
-    await fs.mkdir(tempDir, { recursive: true });
+    await fs.mkdir(tempDir, { recursive: true, ...(options.dirMode !== undefined && { mode: options.dirMode }) });
 
     // Create concat file
     const concatContent = chapters
diff --git a/src/lib/utils/epub-fixer.ts b/src/lib/utils/epub-fixer.ts
index fafe2cd..c66567b 100644
--- a/src/lib/utils/epub-fixer.ts
+++ b/src/lib/utils/epub-fixer.ts
@@ -17,6 +17,7 @@ import * as cheerio from 'cheerio';
 import path from 'path';
 import fs from 'fs/promises';
 import { RMABLogger } from './logger';
+import { getConfigService } from '../services/config.service';
 
 const moduleLogger = RMABLogger.create('EpubFixer');
 
@@ -204,7 +205,10 @@ export async function fixEpubForKindle(
     // Create unique temp subdirectory to avoid filename conflicts
     // This preserves the original filename for the final organized file
     const uniqueDir = path.join(tempDir, `kindle-fix-${Date.now()}`);
-    await fs.mkdir(uniqueDir, { recursive: true });
+    const configService = getConfigService();
+    const dirChmodStr = await configService.get('dir_chmod') || '775';
+    const dirMode = parseInt(dirChmodStr, 8);
+    await fs.mkdir(uniqueDir, { recursive: true, mode: dirMode });
 
     // Keep original filename
     const sourceFilename = path.basename(sourcePath);
diff --git a/src/lib/utils/file-organizer.ts b/src/lib/utils/file-organizer.ts
index aa0f2c0..25bc3d8 100644
--- a/src/lib/utils/file-organizer.ts
+++ b/src/lib/utils/file-organizer.ts
@@ -64,10 +64,14 @@ export interface LoggerConfig {
 export class FileOrganizer {
   private mediaDir: string;
   private tempDir: string;
+  private fileMode: number;
+  private dirMode: number;
 
-  constructor(mediaDir: string = '/media/audiobooks', tempDir: string = '/tmp/readmeabook') {
+  constructor(mediaDir: string = '/media/audiobooks', tempDir: string = '/tmp/readmeabook', fileMode: number = 0o664, dirMode: number = 0o775) {
     this.mediaDir = mediaDir;
     this.tempDir = tempDir;
+    this.fileMode = fileMode;
+    this.dirMode = dirMode;
   }
 
   /**
@@ -166,6 +170,7 @@ export class FileOrganizer {
                       year: audiobook.year,
                       asin: audiobook.asin,
                       outputPath,
+                      dirMode: this.dirMode,
                     },
                     logger ?? undefined
                   );
@@ -293,7 +298,7 @@ export class FileOrganizer {
       await logger?.info(`Target path: ${targetPath}`);
 
       // Create target directory
-      await fs.mkdir(targetPath, { recursive: true });
+      await fs.mkdir(targetPath, { recursive: true, mode: this.dirMode });
 
       // Determine if file renaming should be applied
       const shouldRename = renameConfig?.enabled && renameConfig.template;
@@ -386,7 +391,7 @@ export class FileOrganizer {
           // Copy file via streams (avoids copy_file_range EPERM on NFS/FUSE)
           await copyFile(sourcePath, targetFilePath);
           // Set explicit permissions after copy
-          await fs.chmod(targetFilePath, 0o644);
+          await fs.chmod(targetFilePath, this.fileMode);
 
           result.audioFiles.push(targetFilePath);
           result.filesMovedCount++;
@@ -422,7 +427,7 @@ export class FileOrganizer {
             try {
               await fs.access(originalSourcePath, fs.constants.R_OK);
               await copyFile(originalSourcePath, targetFilePath);
-              await fs.chmod(targetFilePath, 0o644);
+              await fs.chmod(targetFilePath, this.fileMode);
               result.audioFiles.push(targetFilePath);
               result.filesMovedCount++;
               await logger?.info(`Fallback copy succeeded (without metadata tags): ${filename}`);
@@ -457,7 +462,7 @@ export class FileOrganizer {
         try {
           // Copy cover art (do NOT delete original)
           await copyFile(sourcePath, targetCoverPath);
-          await fs.chmod(targetCoverPath, 0o644);
+          await fs.chmod(targetCoverPath, this.fileMode);
           result.coverArtFile = targetCoverPath;
           result.filesMovedCount++;
           await logger?.info(`Copied cover art`);
@@ -718,7 +723,7 @@ export class FileOrganizer {
 
         // Copy from local cache instead of downloading
         await copyFile(cachedPath, targetPath);
-        await fs.chmod(targetPath, 0o644);
+        await fs.chmod(targetPath, this.fileMode);
         moduleLogger.debug(`Copied cover art from cache: ${filename}`);
       } else {
         // Download from external URL (e.g., Audible CDN)
@@ -846,7 +851,7 @@ export class FileOrganizer {
       await logger?.info(`Target directory: ${targetDir}`);
 
       // Create target directory
-      await fs.mkdir(targetDir, { recursive: true });
+      await fs.mkdir(targetDir, { recursive: true, mode: this.dirMode });
 
       // Build target filename (apply rename template if enabled, otherwise sanitize source filename)
       const sourceFilename = path.basename(ebookFile);
@@ -882,7 +887,7 @@ export class FileOrganizer {
 
       // Copy ebook file (do NOT delete original - may need for seeding or retry)
       await copyFile(sourceFilePath, targetPath);
-      await fs.chmod(targetPath, 0o644);
+      await fs.chmod(targetPath, this.fileMode);
 
       await logger?.info(`Copied ebook: ${targetFilename}`);
 
@@ -968,7 +973,7 @@ export class FileOrganizer {
 
 /**
  * Get FileOrganizer instance configured from database settings
- * Reads media_dir from database configuration, falls back to /media/audiobooks if not configured
+ * Reads media_dir, file_chmod, dir_chmod from database configuration
  */
 export async function getFileOrganizer(): Promise<FileOrganizer> {
   // Read media_dir from database config
@@ -979,7 +984,15 @@ export async function getFileOrganizer(): Promise<FileOrganizer> {
   const mediaDir = config?.value || process.env.MEDIA_DIR || '/media/audiobooks';
   const tempDir = process.env.TEMP_DIR || '/tmp/readmeabook';
 
-  return new FileOrganizer(mediaDir, tempDir);
+  // Read file/directory permission settings
+  const { getConfigService } = await import('../services/config.service');
+  const configService = getConfigService();
+  const fileChmodStr = await configService.get('file_chmod') || '664';
+  const dirChmodStr = await configService.get('dir_chmod') || '775';
+  const fileMode = parseInt(fileChmodStr, 8);
+  const dirMode = parseInt(dirChmodStr, 8);
+
+  return new FileOrganizer(mediaDir, tempDir, fileMode, dirMode);
 }
 
 /**
diff --git a/tests/processors/download-torrent.processor.test.ts b/tests/processors/download-torrent.processor.test.ts
index f6415c6..179b5f2 100644
--- a/tests/processors/download-torrent.processor.test.ts
+++ b/tests/processors/download-torrent.processor.test.ts
@@ -8,7 +8,10 @@ import { createPrismaMock } from '../helpers/prisma';
 import { createJobQueueMock } from '../helpers/job-queue';
 
 const prismaMock = createPrismaMock();
-const configMock = vi.hoisted(() => ({ get: vi.fn() }));
+const configMock = vi.hoisted(() => ({
+  get: vi.fn(),
+  getMany: vi.fn().mockResolvedValue({ prowlarr_api_key: null }),
+}));
 const jobQueueMock = createJobQueueMock();
 const qbtMock = vi.hoisted(() => ({ addTorrent: vi.fn() }));
 const sabMock = vi.hoisted(() => ({ addNZB: vi.fn() }));
@@ -54,6 +57,8 @@ vi.mock('@/lib/integrations/prowlarr.service', () => ({
 describe('processDownloadTorrent', () => {
   beforeEach(() => {
     vi.clearAllMocks();
+    // Restore default implementations cleared by clearAllMocks
+    configMock.getMany.mockResolvedValue({ prowlarr_api_key: null });
   });
 
   const torrentPayload = {