From c8bbe18866ff1ae6c7ee9195cc2349764734c7f9 Mon Sep 17 00:00:00 2001
From: mukunda katta <mukunda.vjcs6@gmail.com>
Date: Fri, 15 May 2026 13:05:49 -0700
Subject: [PATCH] fix: avoid duplicate interactions user-agent headers

---
 google/genai/_api_client.py                   | 22 +++++++++++++------
 .../genai/tests/client/test_http_options.py   | 20 ++++++++++++++++-
 google/genai/tests/interactions/test_auth.py  | 11 ++++++++++
 3 files changed, 45 insertions(+), 8 deletions(-)

diff --git a/google/genai/_api_client.py b/google/genai/_api_client.py
index e6202815e..a6523e921 100644
--- a/google/genai/_api_client.py
+++ b/google/genai/_api_client.py
@@ -123,15 +123,23 @@ def append_library_version_headers(headers: dict[str, str]) -> None:
   library_label = f'google-genai-sdk/{version.__version__}'
   language_label = 'gl-python/' + sys.version.split()[0]
   version_header_value = f'{library_label} {language_label}'
+  user_agent = None
+  for header_name in list(headers):
+    if header_name.lower() == 'user-agent':
+      value = headers.pop(header_name)
+      if user_agent is None or header_name == 'User-Agent':
+        user_agent = value
   if (
-      'user-agent' in headers
-      and library_label not in headers['user-agent']
+      user_agent is not None
+      and library_label not in user_agent
   ):
-    headers['user-agent'] = f'{version_header_value} ' + headers['user-agent']
-  elif 'user-agent' in headers and language_label not in headers['user-agent']:
-    headers['user-agent'] = f'{headers["user-agent"]} {language_label}'
-  elif 'user-agent' not in headers:
-    headers['user-agent'] = version_header_value
+    headers['User-Agent'] = f'{version_header_value} {user_agent}'
+  elif user_agent is not None and language_label not in user_agent:
+    headers['User-Agent'] = f'{user_agent} {language_label}'
+  elif user_agent is None:
+    headers['User-Agent'] = version_header_value
+  else:
+    headers['User-Agent'] = user_agent
   if (
       'x-goog-api-client' in headers
       and library_label not in headers['x-goog-api-client']
diff --git a/google/genai/tests/client/test_http_options.py b/google/genai/tests/client/test_http_options.py
index e27808142..dba5bc22d 100644
--- a/google/genai/tests/client/test_http_options.py
+++ b/google/genai/tests/client/test_http_options.py
@@ -92,10 +92,28 @@ def test_patch_http_options_appends_version_headers():
       timeout=10000,
   )
   patched = _api_client.patch_http_options(original_options, patch_options)
-  assert 'user-agent' in patched.headers
+  assert 'User-Agent' in patched.headers
   assert 'x-goog-api-client' in patched.headers
 
 
+def test_patch_http_options_canonicalizes_user_agent_header():
+  original_options = types.HttpOptions(
+      headers={
+          'user-agent': 'lower-agent',
+          'User-Agent': 'custom-agent',
+      }
+  )
+  patched = _api_client.patch_http_options(
+      original_options,
+      types.HttpOptions(),
+  )
+
+  assert 'User-Agent' in patched.headers
+  assert 'user-agent' not in patched.headers
+  assert patched.headers['User-Agent'].endswith('custom-agent')
+  assert 'lower-agent' not in patched.headers['User-Agent']
+
+
 def test_setting_timeout_populates_server_timeout_header():
   api_client = _api_client.BaseApiClient(
       vertexai=False,
diff --git a/google/genai/tests/interactions/test_auth.py b/google/genai/tests/interactions/test_auth.py
index 5c92a225e..11f741e13 100644
--- a/google/genai/tests/interactions/test_auth.py
+++ b/google/genai/tests/interactions/test_auth.py
@@ -20,6 +20,7 @@
 from ... import _base_url
 from unittest import mock
 import pytest
+import httpx
 from httpx import Request, Response
 from ..._api_client import AsyncHttpxClient, BaseApiClient
 from httpx import Client as HTTPClient
@@ -54,6 +55,16 @@ def test_interactions_gemini_url(monkeypatch):
         assert request.headers['x-goog-api-key'] == 'test-api-key'
 
 
+def test_interactions_default_headers_have_single_user_agent(monkeypatch):
+    monkeypatch.setenv('GOOGLE_API_KEY', 'test-api-key')
+    client = Client()
+
+    headers = httpx.Headers(client.aio.interactions._client.default_headers)
+
+    assert len(headers.get_list('user-agent')) == 1
+    assert 'google-genai-sdk/' in headers['user-agent']
+
+
 def test_interactions_gemini_no_vertex_auth(monkeypatch):
     monkeypatch.setenv('GOOGLE_API_KEY', 'test-api-key')
     client = Client()