Root cause: tests/test_mcp_server.py and tests/test_issue1857_usage_overwrite.py
both leaked module state into the full pytest suite, causing 20+ failures in
unrelated test files when they ran together.
Two distinct bugs:
1. test_issue1857_usage_overwrite.py used mock.patch.dict(sys.modules, {...}).
patch.dict tracks original keys at __enter__ and DELETES any keys added
during the patch on __exit__. That silently evicted lazily-imported
pydantic submodules (e.g. pydantic.root_model), producing
KeyError: 'pydantic.root_model' in test_mcp_server.py downstream.
Fix: manual save/restore of only the three keys we explicitly inject.
2. test_mcp_server.py mutated module-level constants on api.config / api.models /
mcp_server (STATE_DIR, SESSION_DIR, PROJECTS_FILE, …) without restoring,
leaving downstream tests reading deleted tmpdirs. Fix: snapshot original
values on first _reimport_mcp() call and restore in _cleanup_state_dir.
Additionally, test_profiles_match_single_source_of_truth re-imported
api.routes / api.profiles into sys.modules and only restored sys.modules,
not the parent api package's attributes. `import api.routes as r` resolves
via sys.modules['api'].routes (parent attribute), NOT directly via
sys.modules['api.routes']. So fresh modules leaked through despite the
sys.modules restore. Fix: also restore parent-package attributes.
Result: full pytest suite goes from 20 failures + 36 errors back to all green
(4947 passed, 8 skipped). Up from 4898 in v0.51.27, gain of 49 from
PR #1895 (MCP server tests) + #1866 (goal handler tests).
nesquena-hermes