diff --git a/backend/open_webui/config.py b/backend/open_webui/config.py
index 2d9cb5de8b..a277510454 100644
--- a/backend/open_webui/config.py
+++ b/backend/open_webui/config.py
@@ -916,6 +916,8 @@ RAG_FILE_MAX_COUNT = int(os.getenv('RAG_FILE_MAX_COUNT')) if os.getenv('RAG_FILE
 
 RAG_FILE_MAX_SIZE = int(os.getenv('RAG_FILE_MAX_SIZE')) if os.getenv('RAG_FILE_MAX_SIZE') else None
 
+RAG_FILE_CONTENT_SEARCH_MAX_CHARS = int(os.getenv('RAG_FILE_CONTENT_SEARCH_MAX_CHARS', str(64 * 1024 * 1024)))
+
 FILE_IMAGE_COMPRESSION_WIDTH = int(os.getenv('FILE_IMAGE_COMPRESSION_WIDTH')) if os.getenv('FILE_IMAGE_COMPRESSION_WIDTH') else None
 
 FILE_IMAGE_COMPRESSION_HEIGHT = int(os.getenv('FILE_IMAGE_COMPRESSION_HEIGHT')) if os.getenv('FILE_IMAGE_COMPRESSION_HEIGHT') else None
diff --git a/backend/open_webui/models/knowledge.py b/backend/open_webui/models/knowledge.py
index 9d49aa7cbf..f6650e2258 100644
--- a/backend/open_webui/models/knowledge.py
+++ b/backend/open_webui/models/knowledge.py
@@ -4,6 +4,7 @@ import time
 import uuid
 from typing import Optional
 
+from open_webui.config import RAG_FILE_CONTENT_SEARCH_MAX_CHARS
 from open_webui.internal.db import Base, JSONField, get_async_db_context
 from open_webui.models.access_grants import AccessGrantModel, AccessGrants
 from open_webui.models.files import (
@@ -381,6 +382,7 @@ class KnowledgeTable:
                             # to avoid PostgreSQL "invalid memory alloc request
                             # size" on large extracted-content rows (#24670).
                             content_text = File.data['content'].as_string()
+                            content_text = func.substr(content_text, 1, RAG_FILE_CONTENT_SEARCH_MAX_CHARS)
                             search_filter = or_(
                                 File.filename.ilike(f'%{q}%'),
                                 content_text.ilike(f'%{q}%'),
@@ -573,6 +575,7 @@ class KnowledgeTable:
                             # to avoid PostgreSQL memory allocation failures on
                             # large content (#24670).
                             content_text = File.data['content'].as_string()
+                            content_text = func.substr(content_text, 1, RAG_FILE_CONTENT_SEARCH_MAX_CHARS)
                             stmt = stmt.filter(
                                 or_(
                                     File.filename.ilike(f'%{query_key}%'),