diff --git a/api/controllers/common/helpers.py b/api/controllers/common/helpers.py
index ef89e66980..84903733b5 100644
--- a/api/controllers/common/helpers.py
+++ b/api/controllers/common/helpers.py
@@ -41,7 +41,8 @@ def guess_file_info_from_response(response: httpx.Response):
     # Try to extract filename from URL
     parsed_url = urllib.parse.urlparse(url)
     url_path = parsed_url.path
-    filename = os.path.basename(url_path)
+    # Decode percent-encoded characters in the path segment
+    filename = urllib.parse.unquote(os.path.basename(url_path))
 
     # If filename couldn't be extracted, use Content-Disposition header
     if not filename:
diff --git a/api/factories/file_factory/remote.py b/api/factories/file_factory/remote.py
index e5a7186007..9b8f94b1f3 100644
--- a/api/factories/file_factory/remote.py
+++ b/api/factories/file_factory/remote.py
@@ -19,8 +19,13 @@ from werkzeug.http import parse_options_header
 from core.helper import ssrf_proxy
 
 
-def extract_filename(url_path: str, content_disposition: str | None) -> str | None:
-    """Extract a safe filename from Content-Disposition or the request URL path."""
+def extract_filename(url_or_path: str, content_disposition: str | None) -> str | None:
+    """Extract a safe filename from Content-Disposition or the request URL path.
+
+    Handles full URLs, paths with query strings, hash fragments, and percent-encoded segments.
+    Query strings and hash fragments are stripped from the URL before extracting the basename.
+    Percent-encoded characters in the path are decoded safely.
+    """
     filename: str | None = None
     if content_disposition:
         filename_star_match = re.search(r"filename\*=([^;]+)", content_disposition)
@@ -47,8 +52,13 @@ def extract_filename(url_path: str, content_disposition: str | None) -> str | No
                 filename = urllib.parse.unquote(raw)
 
     if not filename:
-        candidate = os.path.basename(url_path)
-        filename = urllib.parse.unquote(candidate) if candidate else None
+        # Parse the URL to extract just the path, stripping query strings and fragments
+        # This handles both full URLs and bare paths
+        parsed = urllib.parse.urlparse(url_or_path)
+        path = parsed.path
+        candidate = os.path.basename(path)
+        # Decode percent-encoded characters, with safe fallback for malformed input
+        filename = urllib.parse.unquote(candidate, errors="replace") if candidate else None
 
     if filename:
         filename = os.path.basename(filename)
diff --git a/api/tests/unit_tests/factories/test_file_factory.py b/api/tests/unit_tests/factories/test_file_factory.py
index 5b105d6084..c2835c4124 100644
--- a/api/tests/unit_tests/factories/test_file_factory.py
+++ b/api/tests/unit_tests/factories/test_file_factory.py
@@ -230,3 +230,64 @@ class TestExtractFilename:
             "http://example.com/", 'attachment; filename="file%20with%20quotes%20%26%20encoding.txt"'
         )
         assert result == "file with quotes & encoding.txt"
+
+    def test_url_with_query_string(self):
+        """Test that query strings are stripped from URL basename."""
+        result = extract_filename("http://example.com/path/file.txt?signature=abc123&expires=12345", None)
+        assert result == "file.txt"
+
+    def test_url_with_hash_fragment(self):
+        """Test that hash fragments are stripped from URL basename."""
+        result = extract_filename("http://example.com/path/file.txt#section", None)
+        assert result == "file.txt"
+
+    def test_url_with_query_and_fragment(self):
+        """Test that both query strings and hash fragments are stripped."""
+        result = extract_filename("http://example.com/path/file.txt?token=xyz#section", None)
+        assert result == "file.txt"
+
+    def test_signed_url_preserves_filename(self):
+        """Test that signed URL parameters don't affect filename extraction."""
+        result = extract_filename(
+            "http://storage.example.com/bucket/documents/report.pdf?AWSAccessKeyId=xxx&Signature=yyy&Expires=12345",
+            None,
+        )
+        assert result == "report.pdf"
+
+    def test_percent_encoded_filename_with_query_string(self):
+        """Test percent-encoded filename with query string is decoded correctly."""
+        result = extract_filename("http://example.com/path/my%20file.txt?download=true", None)
+        assert result == "my file.txt"
+
+    def test_percent_encoded_filename_with_fragment(self):
+        """Test percent-encoded filename with fragment is decoded correctly."""
+        result = extract_filename("http://example.com/path/my%20file.txt#page=1", None)
+        assert result == "my file.txt"
+
+    def test_complex_percent_encoding_with_query(self):
+        """Test complex percent-encoded filename with query parameters."""
+        result = extract_filename("http://example.com/docs/%E4%B8%AD%E6%96%87%E6%96%87%E4%BB%B6.pdf?v=1", None)
+        assert result == "中文文件.pdf"
+
+    def test_url_with_special_chars_in_query(self):
+        """Test that special characters in query string don't affect filename."""
+        result = extract_filename("http://example.com/file.bin?name=test&path=/some/path", None)
+        assert result == "file.bin"
+
+    def test_malformed_percent_encoding_safe_fallback(self):
+        """Test that malformed percent-encoding is handled safely."""
+        result = extract_filename("http://example.com/path/file%20name%GG.txt?x=1", None)
+        # %GG is invalid, should be replaced with replacement character
+
+        assert "file" in result
+        assert ".txt" in result
+
+    def test_empty_path_with_query_returns_none(self):
+        """Test that empty path with query string returns None."""
+        result = extract_filename("http://example.com/?query=value", None)
+        assert result is None
+
+    def test_path_only_with_query_string(self):
+        """Test bare path (not full URL) with query string."""
+        result = extract_filename("/path/to/file.txt?extra=params", None)
+        assert result == "file.txt"