fix: keep run_mcp.py stderr to the JSON error contract under fastmcp 3#37
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The SDK 1.3.0 re-lock floated fastmcp from 2.x to 3.2.3 (constraint had no upper bound), and fastmcp 3 logs tool-call exceptions to stderr as Rich tracebacks. The monorepo surface harness json.loads()'s stderr on non-zero exit, so every parsed error payload silently degraded to a raw string and test_get_nonexistent failed with AttributeError. - run_mcp.py: disable all library logging before the server import — the harness owns the "error JSON on stderr, nothing else" contract - pyproject: pin fastmcp>=3.2.3,<4 so a major can't float in on an unrelated re-lock again Co-authored-by: Cursor <cursoragent@cursor.com>
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Summary
fastmcp2.x → 3.2.3 because the constraint (>=2.0.0) had no upper bound. fastmcp 3 logs tool-call exceptions to stderr as Rich tracebacks, polluting the test harness's "error JSON on stderr" contract — the monorepo surface testsjson.loads()stderr on non-zero exit, so error payloads degraded to raw strings (test_get_nonexistentfailed withAttributeError: 'str' object has no attribute 'get').tests/run_mcp.py:logging.disable(logging.CRITICAL)before the server import; the harness now enforces its stderr contract regardless of library logging behavior.pyproject.toml: pinfastmcp>=3.2.3,<4so the next major can't slide in on an unrelated re-lock.run_mcp.pyis a repo-only harness file (not in the published package), so merging this fixes the monorepo surface-integration + nightly flows immediately — no release needed.Test plan
{"error": "ApiError (...)", ...}), no tracebacksurfaces/mcp_server/test_status_pages.pyagainst the mono test stack: 25/25 pass, includingtest_get_nonexistentMade with Cursor