[cloudsmith-iduffy]

Description

Sentry CLOUDSMITH-CLI-20 is a BrokenPipeError from cloudsmith mcp start on 1.30.0 (Homebrew). The MCP client closed its end of stdout while the server was writing a reply.

The mcp library writes stdio replies in an anyio task group. The task group wraps the BrokenPipeError in an ExceptionGroup. The error left DynamicMCPServer.run(), and AliasGroup.main reported it to Sentry and exited with status 1.

run() now catches the closed pipe with except* BrokenPipeError and returns. A client that goes away is a normal end of the session. Any other error in the group is still raised.

Linear: ENG-15479. Fixes CLOUDSMITH-CLI-20

Type of Change

• Bug fix

Additional Notes

The patch in ENG-15479 does not fix this. It catches a plain BrokenPipeError, but mcp 2.3.0 raises ExceptionGroup(BrokenPipeError), and its test mocked the plain error. To see the real error, run the stdio server with stdout on a closed pipe:

echo '<initialize request>' | python -c '<MCPServer("t").run(transport="stdio")>' | true
# ExceptionGroup: unhandled errors in a TaskGroup (1 sub-exception) -> BrokenPipeError

The new test does this in a subprocess with the real library. It fails on master with exit status 1 and the ExceptionGroup traceback.

After the fix, Python still prints Exception ignored while finalizing file <_io.BufferedWriter name=8> to stderr. That writer is a private copy of fd 1 that mcp opens, and the CLI cannot reach it. The message does not change the exit status. Sentry does not see it, because the SDK runs with default_integrations=False.

🤖 Generated with Claude Code

[Copilot]

🟢 Approval recommended

No active review issues remain for the change that treats a client closing stdout as a normal MCP session end.

No open issues 🎉

What changed in this PR

Updates cloudsmith mcp start to treat a client closing stdout as a normal session end rather than an error.

Changes:

• Handles BrokenPipeError inside exception groups while allowing unrelated errors to propagate.
• Adds a subprocess regression test using the real MCP transport and a closed stdout pipe.
• Documents the corrected exit behavior in the changelog.

File	Description
cloudsmith_cli/​core/​mcp/​server.py	Suppresses grouped broken-pipe errors during stdio operation.
cloudsmith_cli/​cli/​tests/​commands/​test_mcp.py	Verifies successful exit when the client closes stdout.
CHANGELOG.md	Records the MCP disconnect fix.

_{Review effort: Balanced}

[Copilot]

🟢 Approval recommended

No active review issues are reported for the change treating closed MCP client connections as normal shutdowns.

No open issues 🎉

_{Review effort: Balanced}