Expose the httpx client factory as public API in mcp.client.streamable_http

Customizing the streamable-HTTP client's headers/auth/timeout requires
building an httpx2.AsyncClient, but the standardized factory
(create_mcp_http_client), the McpHttpClientFactory protocol, and the
default timeout constants only lived in the private
mcp.shared._httpx_utils module. Re-export them from the public
mcp.client.streamable_http module — where streamable_http_client itself
lives — so building a custom client does not require importing a private
module.

Add a regression test asserting the public names resolve to the same
objects as the private ones, and point the migration guide at the public
import path.

Refs #3238

Author: ProgrammerPlus1998

docs/migration.md

@@ -2109,6 +2109,18 @@ v1's internal client set `follow_redirects=True`; set it explicitly when supplyi
 - `httpx_client_factory`: gone with no replacement — call your factory yourself and pass the result as `http_client`.
 - `terminate_on_close`: unchanged (default `True`).
 
+If you'd rather not hand-build the `httpx2.AsyncClient`, the standardized factory and its defaults are re-exported from the public `mcp.client.streamable_http` module, so you don't need to touch the private `mcp.shared._httpx_utils`:
+
+```python
+from mcp.client.streamable_http import create_mcp_http_client, streamable_http_client
+
+async with create_mcp_http_client(headers={"Authorization": "Bearer token"}) as http_client:
+    async with streamable_http_client(url="http://localhost:8000/mcp", http_client=http_client) as (read_stream, write_stream):
+        ...
+```
+
+`create_mcp_http_client(headers=..., timeout=..., auth=...)` applies the MCP defaults (`follow_redirects=True` and `Timeout(30, read=300)`) for you; the `McpHttpClientFactory` protocol and the `MCP_DEFAULT_TIMEOUT` / `MCP_DEFAULT_SSE_READ_TIMEOUT` constants are available from the same module.
+
 Client-side stream resumption is also unchanged: the transport reconnects a dropped GET stream with `Last-Event-ID` on its own, and `session.send_request(..., metadata=ClientMessageMetadata(resumption_token=..., on_resumption_token_update=...))` (from `mcp.shared.message`) works as in v1.
 
 ### `get_session_id` callback removed from `streamable_http_client`

src/mcp/client/streamable_http.py

@@ -33,11 +33,33 @@
 from mcp.client._transport import TransportStreams
 from mcp.shared._compat import resync_tracer
 from mcp.shared._context_streams import ContextReceiveStream, ContextSendStream, create_context_streams
-from mcp.shared._httpx_utils import create_mcp_http_client
+from mcp.shared._httpx_utils import (
+    MCP_DEFAULT_SSE_READ_TIMEOUT,
+    MCP_DEFAULT_TIMEOUT,
+    McpHttpClientFactory,
+    create_mcp_http_client,
+)
 from mcp.shared.inbound import MCP_PROTOCOL_VERSION_HEADER
 from mcp.shared.jsonrpc_dispatcher import cancelled_request_id_from_params
 from mcp.shared.message import ClientMessageMetadata, SessionMessage
 
+__all__ = [
+    "LAST_EVENT_ID",
+    "MAX_RECONNECTION_ATTEMPTS",
+    "MCP_DEFAULT_SSE_READ_TIMEOUT",
+    "MCP_DEFAULT_TIMEOUT",
+    "MCP_SESSION_ID",
+    "McpHttpClientFactory",
+    "RequestContext",
+    "ResumptionError",
+    "StreamReader",
+    "StreamWriter",
+    "StreamableHTTPError",
+    "StreamableHTTPTransport",
+    "create_mcp_http_client",
+    "streamable_http_client",
+]
+
 logger = logging.getLogger(__name__)
 
 

tests/shared/test_httpx_utils.py

@@ -22,3 +22,16 @@ def test_custom_parameters():
 
     assert client.headers["Authorization"] == "Bearer token"
     assert client.timeout.connect == 60.0
+
+
+def test_public_reexport_from_streamable_http():
+    """The factory, protocol, and timeout defaults are importable from the
+    public ``mcp.client.streamable_http`` module, not only the private
+    ``mcp.shared._httpx_utils``."""
+    import mcp.shared._httpx_utils as private_module
+    from mcp.client import streamable_http
+
+    assert streamable_http.create_mcp_http_client is private_module.create_mcp_http_client
+    assert streamable_http.McpHttpClientFactory is private_module.McpHttpClientFactory
+    assert streamable_http.MCP_DEFAULT_TIMEOUT == private_module.MCP_DEFAULT_TIMEOUT
+    assert streamable_http.MCP_DEFAULT_SSE_READ_TIMEOUT == private_module.MCP_DEFAULT_SSE_READ_TIMEOUT