fix: catch BaseException in MCP shutdown guards to suppress double-Ctrl+C traceback

[teknium1]

Summary

A second Ctrl+C during MCP shutdown now exits cleanly instead of printing a KeyboardInterrupt traceback.

The CLI's _signal_handler_q raises KeyboardInterrupt (a BaseException, not Exception). The two best-effort teardown guards on the shutdown path caught only Exception, so a second interrupt during the up-to-15s future.result(timeout=15) wait escaped cleanup and surfaced as an unhandled traceback.

Salvage of #39453 by @HeLLGURD onto current main (the original branch was stale — its diff also showed a _branched_from block already present on main; that phantom chunk drops out on cherry-pick). Closes #39367.

Changes

• cli.py _run_cleanup(): except Exception → except BaseException
• tools/mcp_tool.py shutdown_mcp_servers(): except Exception → except BaseException

Both guards are pure best-effort teardown (pass / log-and-continue), so the wider catch only lets cleanup finish and the process exit without a traceback.

Validation

E2E (real source from worktree):

	except Exception (old)	except BaseException (new)
2nd Ctrl+C → KeyboardInterrupt	escapes guard → traceback	swallowed → clean exit

Both files compile clean.

Credit: @HeLLGURD (commits cherry-picked with authorship preserved).

Infographic

[github-actions]

🔎 Lint report: hermes/hermes-ba721783 vs origin/main

ruff

Total: 0 on HEAD, 0 on base (➖ 0)

🆕 New issues: none

✅ Fixed issues: none

Unchanged: 0 pre-existing issues carried over.

ty (type checker)

Total: 9850 on HEAD, 9850 on base (➖ 0)

🆕 New issues: none

✅ Fixed issues: none

Unchanged: 5107 pre-existing issues carried over.

Diagnostics are surfaced as warnings — this check never fails the build.

[tonydwb]

Code Review Summary

Verdict: Approved

Small but effective shutdown robustness fix. Replacing Exception with BaseException is the right move here: cleanup paths should not let KeyboardInterrupt/SystemExit break shutdown.

✅ Looks Good

• Change is surgical and fully aligned with intended behavior.
• Scope is limited to MCP shutdown + CLI cleanup.
• No observable side effects on normal execution paths.

💡 Suggestions

• Consider documenting this non-obvious choice inline (one comment) so future readers don’t revert it back to Exception during cleanup refactors.

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Reviewed by Hermes Agent