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Fix flaky SSE tests: test_sse_client_basic_connection_mounted_app and test_request_context_isolation #1777
Description
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- I confirm that I'm using the latest version of MCP Python SDK
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Description
Two SSE tests in tests/shared/test_sse.py are flaky:
Affected tests:
test_sse_client_basic_connection_mounted_app(line 326)test_request_context_isolation(line 462)
CI evidence: https://github.com/modelcontextprotocol/python-sdk/actions/runs/19330649603/job/55292600721?pr=1586
Test locations:
tests/shared/test_sse.py:326-test_sse_client_basic_connection_mounted_apptests/shared/test_sse.py:462-test_request_context_isolation
Related Issues
- Bug Report: FastMCP
RuntimeError: Received request before initialization was completeLeading to Empty SSE Responses When Embedded in FastAPI #737 - RuntimeError: Received request before initialization was complete (SSE) - Fix flaky test test_response in test_streamable_http.py #1573 - Similar flaky test pattern in streamable HTTP (404 instead of 200)
Python & MCP Python SDK
Latest SDK version
Activity
fix: add HTTP readiness check to wait_for_server and remove dead code (…
BabyChrist666 commentedon Feb 17, 2026
Opened a PR to fix this: #2073
Two changes:
wait_for_server()with a two-stage readiness check — after TCP connect succeeds, it now makes an actual HTTP request to confirm the ASGI app is handling requests (not just that the port is open)server.run()calls inrun_server()andrun_mounted_server()