From a01b36afe80983ca878b2c4dcdc25f8559a25308 Mon Sep 17 00:00:00 2001
From: Classic298 <27028174+Classic298@users.noreply.github.com>
Date: Sun, 25 Oct 2026 05:59:39 +0100
Subject: [PATCH] fix: file reading tools skip text when paging with line
 numbers on (#33155)

When a model reads a file or knowledge-base file in pages with line numbers turned on, the position it was told to continue from pointed past the end of the previous page, so a chunk of text between pages was silently skipped and never returned. The gap grew with every page, dropping a few percent of a large file. Reading now continues from the right place and returns every character exactly once; paging with line numbers off is unchanged.

Fixes #33099
---
 backend/open_webui/tools/builtin.py | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/backend/open_webui/tools/builtin.py b/backend/open_webui/tools/builtin.py
index 2b28f46846..29000b5d30 100644
--- a/backend/open_webui/tools/builtin.py
+++ b/backend/open_webui/tools/builtin.py
@@ -2909,7 +2909,8 @@ async def view_file(
             return JSONCodec.dumps(result, ensure_ascii=False)
 
         sliced = content[offset : offset + max_chars]
-        is_truncated = (offset + len(sliced)) < total_chars
+        returned_chars = len(sliced)
+        is_truncated = (offset + returned_chars) < total_chars
 
         if line_numbers:
             start_ln = content[:offset].count('\n') + 1
@@ -2927,10 +2928,10 @@ async def view_file(
         if is_truncated or offset > 0:
             result['truncated'] = is_truncated
             result['total_chars'] = total_chars
-            result['returned_chars'] = len(sliced)
+            result['returned_chars'] = returned_chars
             result['offset'] = offset
             if is_truncated:
-                result['next_offset'] = offset + len(sliced)
+                result['next_offset'] = offset + returned_chars
 
         return JSONCodec.dumps(result, ensure_ascii=False)
     except Exception as e:
@@ -3052,7 +3053,8 @@ async def view_knowledge_file(
             return JSONCodec.dumps(result, ensure_ascii=False)
 
         sliced = content[offset : offset + max_chars]
-        is_truncated = (offset + len(sliced)) < total_chars
+        returned_chars = len(sliced)
+        is_truncated = (offset + returned_chars) < total_chars
 
         if line_numbers:
             start_ln = content[:offset].count('\n') + 1
@@ -3073,10 +3075,10 @@ async def view_knowledge_file(
         if is_truncated or offset > 0:
             result['truncated'] = is_truncated
             result['total_chars'] = total_chars
-            result['returned_chars'] = len(sliced)
+            result['returned_chars'] = returned_chars
             result['offset'] = offset
             if is_truncated:
-                result['next_offset'] = offset + len(sliced)
+                result['next_offset'] = offset + returned_chars
 
         return JSONCodec.dumps(result, ensure_ascii=False)
     except Exception as e: