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Fix httpstreamable errorcode #1194

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Fix httpstreamable errorcode #1194

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2f365d8
fix: ensures MCP client can handle 4xx error codes
CriticalGameEror Jul 23, 2025
c143464
refactor: added a custom error message
CriticalGameEror Jul 23, 2025
3a45353
refactor: minor linting adjustments
CriticalGameEror Jul 23, 2025
ee78ac1
Merge branch 'main' into fix-httpstreamable-errorcode
CriticalGameEror Jul 27, 2025
c9c3cdb
refactor: Changed bad request to invalid request
CriticalGameEror Aug 5, 2025
cb58ee1
refactor: minor linting improvements
CriticalGameEror Aug 5, 2025
5badab6
Merge branch 'main' into fix-httpstreamable-errorcode
CriticalGameEror Aug 5, 2025
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23 changes: 23 additions & 0 deletions src/mcp/client/streamable_http.py
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Original file line number Diff line number Diff line change
Expand Up @@ -21,6 +21,7 @@
from mcp.shared._httpx_utils import McpHttpClientFactory, create_mcp_http_client
from mcp.shared.message import ClientMessageMetadata, SessionMessage
from mcp.types import (
INVALID_REQUEST,
ErrorData,
InitializeResult,
JSONRPCError,
Expand Down Expand Up @@ -266,6 +267,14 @@ async def _handle_post_request(self, ctx: RequestContext) -> None:
logger.debug("Received 202 Accepted")
return

if response.status_code == 400:
if isinstance(message.root, JSONRPCRequest):
await self._send_invalid_request_error(
ctx.read_stream_writer,
message.root.id,
)
return

if response.status_code == 404:
if isinstance(message.root, JSONRPCRequest):
await self._send_session_terminated_error(
Expand Down Expand Up @@ -359,6 +368,20 @@ async def _send_session_terminated_error(
session_message = SessionMessage(JSONRPCMessage(jsonrpc_error))
await read_stream_writer.send(session_message)

async def _send_invalid_request_error(
self,
read_stream_writer: StreamWriter,
request_id: RequestId,
) -> None:
"""Send an invalid request error response."""
jsonrpc_error = JSONRPCError(
jsonrpc="2.0",
id=request_id,
error=ErrorData(code=INVALID_REQUEST, message="Invalid request"),
)
session_message = SessionMessage(JSONRPCMessage(jsonrpc_error))
await read_stream_writer.send(session_message)

async def post_writer(
self,
client: httpx.AsyncClient,
Expand Down
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