Content-Length: 5145 | pFad | http://github.com/modelcontextprotocol/python-sdk/pull/2383.patch

thub.com From 17249c3f0d5cdbcf100ad2996bb8a73cceacb308 Mon Sep 17 00:00:00 2001 From: Alberto Farah Date: Tue, 31 Mar 2026 21:07:51 +0000 Subject: [PATCH] fix(streamable_http): allow Content-Type header override Allow StreamableHTTPTransport and streamable_http_client to accept a custom content_type parameter instead of hardcoding 'application/json'. This enables clients to override the Content-Type header to include custom charsets (e.g. 'application/json; charset=utf-8') or other attributes required by specific server implementations. Fixes: modelcontextprotocol/python-sdk#2375 --- src/mcp/client/streamable_http.py | 14 ++++++++--- tests/client/test_http_content_type.py | 35 ++++++++++++++++++++++++++ 2 files changed, 46 insertions(+), 3 deletions(-) create mode 100644 tests/client/test_http_content_type.py diff --git a/src/mcp/client/streamable_http.py b/src/mcp/client/streamable_http.py index 9f3dd5e0b..884b90e22 100644 --- a/src/mcp/client/streamable_http.py +++ b/src/mcp/client/streamable_http.py @@ -72,13 +72,17 @@ class RequestContext: class StreamableHTTPTransport: """StreamableHTTP client transport implementation.""" - def __init__(self, url: str) -> None: + def __init__(self, url: str, content_type: str = "application/json") -> None: """Initialize the StreamableHTTP transport. Args: url: The endpoint URL. + content_type: The Content-Type header value for POST requests. + Defaults to "application/json". Can be overridden to include + custom charsets (e.g. "application/json; charset=utf-8"). """ self.url = url + self.content_type = content_type self.session_id: str | None = None self.protocol_version: str | None = None @@ -90,7 +94,7 @@ def _prepare_headers(self) -> dict[str, str]: """ headers: dict[str, str] = { "accept": "application/json, text/event-stream", - "content-type": "application/json", + "content-type": self.content_type, } # Add session headers if available if self.session_id: @@ -515,6 +519,7 @@ async def streamable_http_client( *, http_client: httpx.AsyncClient | None = None, terminate_on_close: bool = True, + content_type: str = "application/json", ) -> AsyncGenerator[TransportStreams, None]: """Client transport for StreamableHTTP. @@ -524,6 +529,9 @@ async def streamable_http_client( client with recommended MCP timeouts will be created. To configure headers, authentication, or other HTTP settings, create an httpx.AsyncClient and pass it here. terminate_on_close: If True, send a DELETE request to terminate the session when the context exits. + content_type: The Content-Type header value for POST requests. + Defaults to "application/json". Can be overridden to include custom charsets + (e.g. "application/json; charset=utf-8"). Yields: Tuple containing: @@ -544,7 +552,7 @@ async def streamable_http_client( # Create default client with recommended MCP timeouts client = create_mcp_http_client() - transport = StreamableHTTPTransport(url) + transport = StreamableHTTPTransport(url, content_type=content_type) async with anyio.create_task_group() as tg: try: diff --git a/tests/client/test_http_content_type.py b/tests/client/test_http_content_type.py new file mode 100644 index 000000000..cecf2645f --- /dev/null +++ b/tests/client/test_http_content_type.py @@ -0,0 +1,35 @@ +"""Tests for Content-Type override in streamable HTTP transport. + +Verifies that the content_type parameter allows overriding the Content-Type header +to include custom charsets or other attributes. +""" + +import pytest +from mcp.client.streamable_http import StreamableHTTPTransport + + +def test_streamable_http_transport_default_content_type() -> None: + """Test that the default Content-Type is 'application/json'.""" + transport = StreamableHTTPTransport("http://example.com/mcp") + headers = transport._prepare_headers() + assert headers["content-type"] == "application/json" + + +def test_streamable_http_transport_custom_content_type() -> None: + """Test that a custom Content-Type with charset can be specified.""" + transport = StreamableHTTPTransport( + "http://example.com/mcp", + content_type="application/json; charset=utf-8", + ) + headers = transport._prepare_headers() + assert headers["content-type"] == "application/json; charset=utf-8" + + +def test_streamable_http_transport_content_type_preserved_in_headers() -> None: + """Test that Content-Type is correctly placed in prepared headers.""" + custom_type = "application/json; charset=utf-8; boundary=npm" + transport = StreamableHTTPTransport("http://example.com/mcp", content_type=custom_type) + headers = transport._prepare_headers() + # The accept header should also be present + assert "accept" in headers + assert headers["content-type"] == custom_type

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