failing unit test

langchain_mcp_adapters/sessions.py

@@ -140,10 +140,10 @@ class StreamableHttpConnection(TypedDict):
     headers: NotRequired[dict[str, Any] | None]
     """HTTP headers to send to the endpoint."""
 
-    timeout: NotRequired[timedelta]
+    timeout: NotRequired[float | timedelta]
     """HTTP timeout."""
 
-    sse_read_timeout: NotRequired[timedelta]
+    sse_read_timeout: NotRequired[float | timedelta]
     """How long (in seconds) the client will wait for a new event before disconnecting.
     All other HTTP operations are controlled by `timeout`."""
 

pyproject.toml

@@ -15,7 +15,7 @@ readme = "README.md"
 requires-python = ">=3.10"
 dependencies = [
     "langchain-core>=0.3.36,<0.4",
-    "mcp>=1.9.2",
+    "mcp==1.9.2",
     "typing-extensions>=4.14.0",
 ]
 

tests/test_tools.py

@@ -1,10 +1,12 @@
 from typing import Annotated
 from unittest.mock import AsyncMock, MagicMock
 
+import httpx
 import pytest
 from langchain_core.callbacks import CallbackManagerForToolRun
 from langchain_core.messages import ToolMessage
 from langchain_core.tools import BaseTool, InjectedToolArg, ToolException, tool
+from mcp.server import FastMCP
 from mcp.types import (
     CallToolResult,
     EmbeddedResource,
@@ -368,10 +370,8 @@ def get_status() -> str:
 
 
 # Tests for httpx_client_factory functionality
-@pytest.mark.asyncio
 async def test_load_mcp_tools_with_custom_httpx_client_factory(socket_enabled) -> None:
     """Test load mcp tools with custom httpx client factory."""
-    import httpx
 
     # Custom httpx client factory
     def custom_httpx_client_factory(
@@ -423,7 +423,17 @@ def get_info() -> str:
     return server
 
 
-@pytest.mark.asyncio
+def _create_failing_server() -> FastMCP:
+    server = FastMCP(port=8184)
+
+    @server.tool()
+    def failing_tool(message: str) -> str:
+        """A tool that always fails with an exception"""
+        raise ValueError(f"Tool failed: {message}")
+
+    return server
+
+
 async def test_load_mcp_tools_with_custom_httpx_client_factory_sse(
     socket_enabled,
 ) -> None:
@@ -468,3 +478,28 @@ def custom_httpx_client_factory(
             # Expected to fail since server doesn't have SSE endpoint,
             # but the important thing is that httpx_client_factory was passed correctly
             pass
+
+
+async def test_mcp_tool_exception_handling(socket_enabled) -> None:
+    """Test that exceptions from MCP tools are properly handled on the client side."""
+    with run_streamable_http(_create_failing_server, 8184):
+        # Initialize client
+        client = MultiServerMCPClient(
+            {
+                "failing": {
+                    "url": "http://localhost:8184/mcp/",
+                    "transport": "streamable_http",
+                    "timeout": 5,
+                    "sse_read_timeout": 2,
+                }
+            },
+        )
+
+        # Get the failing tool
+        tools = await client.get_tools()
+        assert len(tools) == 1
+        tool = tools[0]
+        assert tool.name == "failing_tool"
+        await tool.ainvoke(
+            {"args": {"message": "test error"}, "id": "1", "type": "tool_call"}
+        )