Test Failure Analysis

Summary: The static analysis (prek) failed because ruff format would reformat 2 files in this PR — the code was not run through the formatter before pushing.

Root Cause: The PR modifies src/fastmcp/client/client.py and tests/client/test_roots.py, but neither was formatted with ruff format. The CI log confirms: 2 files reformatted, 716 files left unchanged. The author noted in the checklist that their local environment was missing loq, so prek wasn't fully verified locally.

Suggested Solution: Run ruff format on the two changed files (or all files) and push:

uv run ruff format src/fastmcp/client/client.py tests/client/test_roots.py

Or run the full prek suite:

uv run prek run --all-files

The most likely formatting issues are:

• tests/client/test_roots.py: missing blank line between test_set_roots_updates_connected_session and the next @pytest.mark.parametrize block
• src/fastmcp/client/client.py: a long line that needs wrapping (the if hasattr(...) condition)

ruff format...............................................................[FAILED]
  2 files reformatted, 716 files left unchanged

            assert result2.data == ["file://b/", "file://c/"]
    @pytest.mark.parametrize("roots", [["x"], ["x", "y"]])  # ← needs blank line before this

        if hasattr(self, "_session_state") and getattr(self._session_state, "session", None) is not None:

🤖 Triage analysis by marvin

Thanks for investigating this. The bug is real, but I'm not comfortable reaching into session._list_roots_callback (a private SDK attribute) to work around the lack of a public API. That kind of coupling tends to break silently on SDK upgrades, and the MCP SDK v2 is on the horizon, which will likely change session internals significantly.

Going to close this for now. If the SDK adds a public way to update callbacks on a live session, this becomes straightforward to implement on the FastMCP side.