From 596864ec7cb382b7ea2552eb31316b611614bb3f Mon Sep 17 00:00:00 2001
From: Nick Cooper <nickc@openai.com>
Date: Mon, 19 May 2025 02:09:01 -0700
Subject: [PATCH 1/2] Support injectable httpx client

---
 src/mcp/client/sse.py             |  7 ++++---
 src/mcp/client/streamable_http.py |  5 +++--
 src/mcp/shared/_httpx_utils.py    | 11 ++++++++++-
 3 files changed, 17 insertions(+), 6 deletions(-)

diff --git a/src/mcp/client/sse.py b/src/mcp/client/sse.py
index 29195cbd9..8047a6c67 100644
--- a/src/mcp/client/sse.py
+++ b/src/mcp/client/sse.py
@@ -1,6 +1,6 @@
 import logging
 from contextlib import asynccontextmanager
-from typing import Any
+from typing import Any, Callable
 from urllib.parse import urljoin, urlparse
 
 import anyio
@@ -10,7 +10,7 @@
 from httpx_sse import aconnect_sse
 
 import mcp.types as types
-from mcp.shared._httpx_utils import create_mcp_http_client
+from mcp.shared._httpx_utils import McpHttpClientFactory, create_mcp_http_client
 from mcp.shared.message import SessionMessage
 
 logger = logging.getLogger(__name__)
@@ -26,6 +26,7 @@ async def sse_client(
     headers: dict[str, Any] | None = None,
     timeout: float = 5,
     sse_read_timeout: float = 60 * 5,
+    httpx_client_factory: McpHttpClientFactory = create_mcp_http_client,
 ):
     """
     Client transport for SSE.
@@ -45,7 +46,7 @@ async def sse_client(
     async with anyio.create_task_group() as tg:
         try:
             logger.info(f"Connecting to SSE endpoint: {remove_request_params(url)}")
-            async with create_mcp_http_client(headers=headers) as client:
+            async with httpx_client_factory(headers=headers) as client:
                 async with aconnect_sse(
                     client,
                     "GET",
diff --git a/src/mcp/client/streamable_http.py b/src/mcp/client/streamable_http.py
index 3324dab5a..19ba6c9ba 100644
--- a/src/mcp/client/streamable_http.py
+++ b/src/mcp/client/streamable_http.py
@@ -19,7 +19,7 @@
 from anyio.streams.memory import MemoryObjectReceiveStream, MemoryObjectSendStream
 from httpx_sse import EventSource, ServerSentEvent, aconnect_sse
 
-from mcp.shared._httpx_utils import create_mcp_http_client
+from mcp.shared._httpx_utils import McpHttpClientFactory, create_mcp_http_client
 from mcp.shared.message import ClientMessageMetadata, SessionMessage
 from mcp.types import (
     ErrorData,
@@ -427,6 +427,7 @@ async def streamablehttp_client(
     timeout: timedelta = timedelta(seconds=30),
     sse_read_timeout: timedelta = timedelta(seconds=60 * 5),
     terminate_on_close: bool = True,
+    httpx_client_factory: McpHttpClientFactory = create_mcp_http_client,
 ) -> AsyncGenerator[
     tuple[
         MemoryObjectReceiveStream[SessionMessage | Exception],
@@ -460,7 +461,7 @@ async def streamablehttp_client(
         try:
             logger.info(f"Connecting to StreamableHTTP endpoint: {url}")
 
-            async with create_mcp_http_client(
+            async with httpx_client_factory(
                 headers=transport.request_headers,
                 timeout=httpx.Timeout(
                     transport.timeout.seconds, read=transport.sse_read_timeout.seconds
diff --git a/src/mcp/shared/_httpx_utils.py b/src/mcp/shared/_httpx_utils.py
index 95080bde1..7729fe697 100644
--- a/src/mcp/shared/_httpx_utils.py
+++ b/src/mcp/shared/_httpx_utils.py
@@ -1,12 +1,21 @@
 """Utilities for creating standardized httpx AsyncClient instances."""
 
-from typing import Any
+from typing import Any, Protocol
 
 import httpx
 
 __all__ = ["create_mcp_http_client"]
 
 
+class McpHttpClientFactory(Protocol):
+    def __call__(
+        self,
+        headers: dict[str, str] | None = None,
+        timeout: httpx.Timeout | None = None,
+    ) -> httpx.AsyncClient:
+        ...
+
+
 def create_mcp_http_client(
     headers: dict[str, str] | None = None,
     timeout: httpx.Timeout | None = None,

From 63208fe08186d37327c2be04128f54205749d6a8 Mon Sep 17 00:00:00 2001
From: Nick Cooper <nickc@openai.com>
Date: Mon, 19 May 2025 02:20:20 -0700
Subject: [PATCH 2/2] nits

---
 src/mcp/client/sse.py          | 2 +-
 src/mcp/shared/_httpx_utils.py | 3 +--
 2 files changed, 2 insertions(+), 3 deletions(-)

diff --git a/src/mcp/client/sse.py b/src/mcp/client/sse.py
index 8047a6c67..572360e5c 100644
--- a/src/mcp/client/sse.py
+++ b/src/mcp/client/sse.py
@@ -1,6 +1,6 @@
 import logging
 from contextlib import asynccontextmanager
-from typing import Any, Callable
+from typing import Any
 from urllib.parse import urljoin, urlparse
 
 import anyio
diff --git a/src/mcp/shared/_httpx_utils.py b/src/mcp/shared/_httpx_utils.py
index 7729fe697..277e67d7a 100644
--- a/src/mcp/shared/_httpx_utils.py
+++ b/src/mcp/shared/_httpx_utils.py
@@ -12,8 +12,7 @@ def __call__(
         self,
         headers: dict[str, str] | None = None,
         timeout: httpx.Timeout | None = None,
-    ) -> httpx.AsyncClient:
-        ...
+    ) -> httpx.AsyncClient: ...
 
 
 def create_mcp_http_client(