diff --git a/src/app/api/account/delete/route.ts b/src/app/api/account/delete/route.ts
index 87ee48a..7b5af66 100644
--- a/src/app/api/account/delete/route.ts
+++ b/src/app/api/account/delete/route.ts
@@ -29,7 +29,7 @@ export async function DELETE() {
       try {
         await deleteUserStorageData(session.user.id, testNamespace);
       } catch (error) {
-        serverLogger.error({ err: error }, '[account-delete] Failed to clean up namespaced user storage before deletion:');
+        serverLogger.warn({ err: error }, '[account-delete] Failed to clean up namespaced user storage before deletion:');
       }
     }
 
diff --git a/src/app/api/audiobook/chapter/route.ts b/src/app/api/audiobook/chapter/route.ts
index cb25256..a979971 100644
--- a/src/app/api/audiobook/chapter/route.ts
+++ b/src/app/api/audiobook/chapter/route.ts
@@ -186,7 +186,7 @@ async function runFFmpeg(args: string[], signal?: AbortSignal): Promise<void> {
     }
 
     ffmpeg.stderr.on('data', (data) => {
-      serverLogger.error(`ffmpeg stderr: ${data}`);
+      serverLogger.warn(`ffmpeg stderr: ${data}`);
     });
 
     ffmpeg.on('close', (code) => {
diff --git a/src/app/api/audiobook/route.ts b/src/app/api/audiobook/route.ts
index 511029e..6694bba 100644
--- a/src/app/api/audiobook/route.ts
+++ b/src/app/api/audiobook/route.ts
@@ -116,7 +116,7 @@ async function runFFmpeg(args: string[], signal?: AbortSignal): Promise<void> {
     }
 
     ffmpeg.stderr.on('data', (data) => {
-      serverLogger.error(`ffmpeg stderr: ${data}`);
+      serverLogger.warn(`ffmpeg stderr: ${data}`);
     });
 
     ffmpeg.on('close', (code) => {
diff --git a/src/app/api/documents/docx-to-pdf/upload/route.ts b/src/app/api/documents/docx-to-pdf/upload/route.ts
index 666596e..5ed9eb2 100644
--- a/src/app/api/documents/docx-to-pdf/upload/route.ts
+++ b/src/app/api/documents/docx-to-pdf/upload/route.ts
@@ -163,7 +163,7 @@ export async function POST(req: NextRequest) {
         },
         testNamespace,
       ).catch((error) => {
-        serverLogger.error({ err: error }, `Failed to enqueue preview for converted DOCX ${id}:`);
+        serverLogger.warn({ err: error }, `Failed to enqueue preview for converted DOCX ${id}:`);
       });
 
       enqueueParsePdfJob({
diff --git a/src/app/api/documents/route.ts b/src/app/api/documents/route.ts
index aee4780..ed613ca 100644
--- a/src/app/api/documents/route.ts
+++ b/src/app/api/documents/route.ts
@@ -173,7 +173,7 @@ export async function POST(req: NextRequest) {
         },
         testNamespace,
       ).catch((error) => {
-        serverLogger.error({ err: error }, `Failed to enqueue preview for document ${doc.id}:`);
+        serverLogger.warn({ err: error }, `Failed to enqueue preview for document ${doc.id}:`);
       });
 
       if (doc.type === 'pdf') {
@@ -343,15 +343,15 @@ export async function DELETE(req: NextRequest) {
         await deleteDocumentBlob(id, testNamespace);
       } catch (error) {
         if (!isMissingBlobError(error)) {
-          serverLogger.error({ err: error }, `[best-effort] Failed to delete blob for document ${id}, orphaned blob may need manual cleanup:`);
+          serverLogger.warn({ err: error }, `[best-effort] Failed to delete blob for document ${id}, orphaned blob may need manual cleanup:`);
         }
       }
 
       await cleanupDocumentPreviewArtifacts(id, testNamespace).catch((error) => {
-        serverLogger.error({ err: error }, `Failed to cleanup preview artifacts for document ${id}:`);
+        serverLogger.warn({ err: error }, `Failed to cleanup preview artifacts for document ${id}:`);
       });
       await deleteDocumentPreviewRows(id, testNamespace).catch((error) => {
-        serverLogger.error({ err: error }, `Failed to cleanup preview rows for document ${id}:`);
+        serverLogger.warn({ err: error }, `Failed to cleanup preview rows for document ${id}:`);
       });
     }
 
diff --git a/src/app/api/user/export/route.ts b/src/app/api/user/export/route.ts
index 2499c79..a74ea48 100644
--- a/src/app/api/user/export/route.ts
+++ b/src/app/api/user/export/route.ts
@@ -78,7 +78,7 @@ export async function GET(req: NextRequest) {
 
   archive.on('warning', (warning) => {
     if ((warning as NodeJS.ErrnoException).code !== 'ENOENT') {
-      serverLogger.error({ err: warning }, 'User export warning:');
+      serverLogger.warn({ err: warning }, 'User export warning:');
     }
   });
 
diff --git a/src/lib/server/auth/auth.ts b/src/lib/server/auth/auth.ts
index 29b3606..d9d28ae 100644
--- a/src/lib/server/auth/auth.ts
+++ b/src/lib/server/auth/auth.ts
@@ -91,7 +91,7 @@ const createAuth = () => betterAuth({
           const { deleteUserStorageData } = await import('@/lib/server/user/data-cleanup');
           await deleteUserStorageData(user.id, null);
         } catch (error) {
-          serverLogger.error({ err: error }, '[auth] Failed to clean up user storage before deletion:');
+          serverLogger.warn({ err: error }, '[auth] Failed to clean up user storage before deletion:');
           // Don't throw – allow the user deletion to proceed even if S3 cleanup fails.
           // Orphaned blobs are preferable to a blocked account deletion.
         }
@@ -163,7 +163,7 @@ const createAuth = () => betterAuth({
                 await rateLimiter.transferAnonymousUsage(anonymousUser.user.id, newUser.user.id);
                 serverLogger.info(`Successfully transferred rate limit data from anonymous user ${anonymousUser.user.id} to user ${newUser.user.id}`);
               } catch (error) {
-                serverLogger.error({ err: error }, "Error transferring rate limit data during account linking:");
+                serverLogger.warn({ err: error }, "Error transferring rate limit data during account linking:");
                 // Don't throw here to prevent blocking the account linking process
               }
 
@@ -174,7 +174,7 @@ const createAuth = () => betterAuth({
                   serverLogger.info(`Successfully transferred ${transferred} audiobook(s) from anonymous user ${anonymousUser.user.id} to user ${newUser.user.id}`);
                 }
               } catch (error) {
-                serverLogger.error({ err: error }, "Error transferring audiobooks during account linking:");
+                serverLogger.warn({ err: error }, "Error transferring audiobooks during account linking:");
                 // Don't throw here to prevent blocking the account linking process
               }
 
@@ -185,7 +185,7 @@ const createAuth = () => betterAuth({
                   serverLogger.info(`Successfully transferred ${transferred} document(s) from anonymous user ${anonymousUser.user.id} to user ${newUser.user.id}`);
                 }
               } catch (error) {
-                serverLogger.error({ err: error }, "Error transferring documents during account linking:");
+                serverLogger.warn({ err: error }, "Error transferring documents during account linking:");
                 // Don't throw here to prevent blocking the account linking process
               }
 
@@ -196,7 +196,7 @@ const createAuth = () => betterAuth({
                   serverLogger.info(`Successfully transferred preferences from anonymous user ${anonymousUser.user.id} to user ${newUser.user.id}`);
                 }
               } catch (error) {
-                serverLogger.error({ err: error }, "Error transferring preferences during account linking:");
+                serverLogger.warn({ err: error }, "Error transferring preferences during account linking:");
                 // Don't throw here to prevent blocking the account linking process
               }
 
@@ -207,7 +207,7 @@ const createAuth = () => betterAuth({
                   serverLogger.info(`Successfully transferred ${transferred} progress row(s) from anonymous user ${anonymousUser.user.id} to user ${newUser.user.id}`);
                 }
               } catch (error) {
-                serverLogger.error({ err: error }, "Error transferring reading progress during account linking:");
+                serverLogger.warn({ err: error }, "Error transferring reading progress during account linking:");
                 // Don't throw here to prevent blocking the account linking process
               }
             } catch (error) {
diff --git a/src/lib/server/user/data-cleanup.ts b/src/lib/server/user/data-cleanup.ts
index c17c66c..88d3dae 100644
--- a/src/lib/server/user/data-cleanup.ts
+++ b/src/lib/server/user/data-cleanup.ts
@@ -50,13 +50,13 @@ export async function deleteUserStorageData(
         await deleteDocumentBlob(doc.id, namespace);
         docsDeleted++;
       } catch (error) {
-        serverLogger.error({ err: error }, `[user-data-cleanup] Failed to delete document blob ${doc.id}:`);
+        serverLogger.warn({ err: error }, `[user-data-cleanup] Failed to delete document blob ${doc.id}:`);
       }
 
       try {
         await deleteDocumentPreviewArtifacts(doc.id, namespace);
       } catch (error) {
-        serverLogger.error({ err: error }, `[user-data-cleanup] Failed to delete preview for ${doc.id}:`);
+        serverLogger.warn({ err: error }, `[user-data-cleanup] Failed to delete preview for ${doc.id}:`);
       }
     }
 
@@ -64,7 +64,7 @@ export async function deleteUserStorageData(
     try {
       await deleteDocumentPreviewRows(doc.id, namespace);
     } catch (error) {
-      serverLogger.error({ err: error }, `[user-data-cleanup] Failed to delete preview rows for ${doc.id}:`);
+      serverLogger.warn({ err: error }, `[user-data-cleanup] Failed to delete preview rows for ${doc.id}:`);
     }
   }
 
@@ -83,7 +83,7 @@ export async function deleteUserStorageData(
       await deleteAudiobookPrefix(prefix);
       booksDeleted++;
     } catch (error) {
-      serverLogger.error({ err: error }, `[user-data-cleanup] Failed to delete audiobook blobs ${book.id}:`);
+      serverLogger.warn({ err: error }, `[user-data-cleanup] Failed to delete audiobook blobs ${book.id}:`);
     }
   }
 
@@ -98,7 +98,7 @@ export async function deleteUserStorageData(
       segmentsDeleted += await deleteTtsSegmentPrefix(ttsPrefixV1);
       segmentsDeleted += await deleteTtsSegmentPrefix(ttsPrefixV2);
     } catch (error) {
-      serverLogger.error({ err: error }, `[user-data-cleanup] Failed to delete TTS segment blobs for user ${userId}:`);
+      serverLogger.warn({ err: error }, `[user-data-cleanup] Failed to delete TTS segment blobs for user ${userId}:`);
     }
   }