feat(mcp): add SSE transport support for MCP client (salvage #19135)#21227
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Add support for MCP servers using the SSE transport protocol
(SseServerTransport) alongside the existing Streamable HTTP and stdio
transports. Many MCP servers use SSE (GET /sse + POST /messages/)
which was previously unsupported -- the client silently fell back to
Streamable HTTP, causing 10s connection timeouts.
Changes:
- Import mcp.client.sse.sse_client with graceful fallback
- Check config.get('transport') == 'sse' in _run_http() to select
the SSE transport path with proper timeout handling
- Read transport type from config in get_mcp_status() instead of
hardcoding 'http' for URL-based servers
- Update docstring, example config, and feature list
Contributor
🔎 Lint report:
|
| Rule | Count |
|---|---|
unresolved-import |
1 |
First entries
tools/mcp_tool.py:201: [unresolved-import] unresolved-import: Cannot resolve imported module `mcp.client.sse`
✅ Fixed issues (1):
| Rule | Count |
|---|---|
invalid-assignment |
1 |
First entries
tools/mcp_tool.py:2978: [invalid-assignment] invalid-assignment: Invalid subscript assignment with key of type `Literal["sampling"]` and value of type `dict[str, int]` on object of type `dict[str, str | int]`
Unchanged: 3941 pre-existing issues carried over.
Diagnostics are surfaced as warnings — this check never fails the build.
alt-glitch
added
type/feature
1 task
5 tasks
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Closes #19135 via salvage.
Summary
_run_http()previously forcedStreamableHTTPTransportfor all URL-based MCP servers; servers using SSE transport (GET /sse+POST /messages/) hung forconnect_timeout. Addstransport: sseopt-in inmcp_servers:config, importsmcp.client.sse.sse_clientwith graceful fallback if the installedmcppackage is too old.get_mcp_status()also now reports the actual transport instead of hardcodinghttp.Validation
scripts/run_tests.sh tests/tools/test_mcp_tool.py→ 182 passed.Verified
mcp.client.sse.sse_clientimports in the current venv.Original author: @andrewhosf.