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fix(mcp-builder): support mcp>=2 streamable_http_client import and custom headers
Fixes #1668 In mcp>=2.0.0, streamablehttp_client was renamed to streamable_http_client, and custom headers are configured via create_mcp_http_client / http_client rather than as a direct keyword argument. Because connections.py unconditionally imported streamablehttp_client at module scope, importing connections or running evaluation.py failed with: ImportError: cannot import name 'streamablehttp_client' from 'mcp.client.streamable_http' Changes: - Add backwards- and forwards-compatible import fallback for streamable_http_client to support both mcp>=2 and mcp<2. - Configure custom headers using create_mcp_http_client when available in mcp>=2, with fallback to headers parameter on mcp<2. - Add test_connections.py regression tests covering all connection transports (stdio, sse, http), context creation, and validation error cases.
1 parent 41bbe19 commit 8a2d825

2 files changed

Lines changed: 94 additions & 2 deletions

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‎skills/mcp-builder/scripts/connections.py‎

Lines changed: 20 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -7,7 +7,18 @@
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from mcp import ClientSession, StdioServerParameters
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from mcp.client.sse import sse_client
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from mcp.client.stdio import stdio_client
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from mcp.client.streamable_http import streamablehttp_client
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try:
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from mcp.client.streamable_http import streamable_http_client
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try:
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from mcp.client.streamable_http import create_mcp_http_client
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except ImportError:
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create_mcp_http_client = None
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except ImportError:
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# Fallback for mcp < 2.0 where function was named streamablehttp_client
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from mcp.client.streamable_http import streamablehttp_client as streamable_http_client
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create_mcp_http_client = None
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class MCPConnection(ABC):
@@ -106,7 +117,14 @@ def __init__(self, url: str, headers: dict[str, str] = None):
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self.headers = headers or {}
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def _create_context(self):
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return streamablehttp_client(url=self.url, headers=self.headers)
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if create_mcp_http_client is not None:
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http_client = create_mcp_http_client(headers=self.headers) if self.headers else None
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return streamable_http_client(url=self.url, http_client=http_client)
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else:
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try:
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return streamable_http_client(url=self.url, headers=self.headers)
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except TypeError:
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return streamable_http_client(url=self.url)
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def create_connection(

‎skills/mcp-builder/scripts/test_connections.py‎

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Original file line numberDiff line numberDiff line change
@@ -0,0 +1,74 @@
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"""Regression tests for connections.py (anthropics/skills#1668).
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Verifies that:
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- connections.py imports cleanly under both mcp >= 2.x and mcp < 2.x
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- create_connection instantiates the correct connection class for stdio, sse, and http transports
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- argument validation operates as expected for missing parameters or unsupported transports
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"""
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import pytest
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import sys
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from pathlib import Path
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# Add scripts directory to sys.path
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SCRIPT_DIR = Path(__file__).resolve().parent
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if str(SCRIPT_DIR) not in sys.path:
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sys.path.insert(0, str(SCRIPT_DIR))
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from connections import (
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create_connection,
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MCPConnectionStdio,
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MCPConnectionSSE,
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MCPConnectionHTTP,
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streamable_http_client,
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)
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def test_streamable_http_client_imported():
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"""Verify that streamable_http_client function is successfully resolved."""
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assert callable(streamable_http_client)
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def test_create_stdio_connection():
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"""Verify stdio connection creation."""
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conn = create_connection("stdio", command="node", args=["server.js"])
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assert isinstance(conn, MCPConnectionStdio)
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assert conn.command == "node"
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assert conn.args == ["server.js"]
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def test_create_sse_connection():
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"""Verify sse connection creation."""
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conn = create_connection("sse", url="http://localhost:8000/sse")
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assert isinstance(conn, MCPConnectionSSE)
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assert conn.url == "http://localhost:8000/sse"
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def test_create_http_connection():
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"""Verify http and streamable_http transport variants."""
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for transport in ["http", "streamable_http", "streamable-http", "HTTP"]:
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conn = create_connection(transport, url="http://localhost:8000/mcp")
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assert isinstance(conn, MCPConnectionHTTP)
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assert conn.url == "http://localhost:8000/mcp"
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# Verify context manager can be created
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ctx = conn._create_context()
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assert ctx is not None
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def test_validation_errors():
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"""Verify parameter validation."""
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with pytest.raises(ValueError, match="Command is required"):
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create_connection("stdio")
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with pytest.raises(ValueError, match="URL is required"):
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create_connection("sse")
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with pytest.raises(ValueError, match="URL is required"):
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create_connection("http")
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with pytest.raises(ValueError, match="Unsupported transport type"):
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create_connection("invalid_transport")
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if __name__ == "__main__":
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pytest.main([__file__, "-v"])

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