Bug: ValueError on MCP server shutdown from promo.py isatty() call

[bm-clawd]

Description

When the BM MCP server shuts down (e.g., after a benchmark run or when an MCP client disconnects), a ValueError: I/O operation on closed file traceback is thrown from the cloud promo system.

Stack trace

basic_memory/cli/app.py:58 in <lambda>
  ctx.call_on_close(lambda: maybe_show_cloud_promo(ctx.invoked_subcommand))

basic_memory/cli/promo.py:85 in maybe_show_cloud_promo
  interactive = _is_interactive_session() if is_interactive is None

basic_memory/cli/promo.py:27 in _is_interactive_session
  return sys.stdin.isatty() and sys.stdout.isatty()

ValueError: I/O operation on closed file

Cause

maybe_show_cloud_promo is registered as a call_on_close callback. When the MCP server runs over stdio, stdin/stdout are closed by the time the callback fires. sys.stdin.isatty() then raises ValueError.

Suggested fix

Guard the isatty check:

def _is_interactive_session() -> bool:
    try:
        return sys.stdin.isatty() and sys.stdout.isatty()
    except ValueError:
        return False

Or skip the promo callback entirely when the invoked subcommand is mcp.

Reproduction

# Any MCP client that connects and disconnects will trigger this
echo '{"jsonrpc":"2.0","id":1,"method":"initialize","params":{"capabilities":{},"clientInfo":{"name":"test","version":"1.0"},"protocolVersion":"2024-11-05"}}' | bm mcp --transport stdio
# Ctrl-C or close stdin → traceback appears

Environment

• basic-memory: installed from main via uv
• Python 3.13.12
• FastMCP 3.0.2
• macOS (x86_64)

[claude]

Claude finished @bm-clawd's task in 2m 15s —— View job • claude/issue-607-20260225-1754 • Create PR ➔

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Analysis & Triage

Classification: Bug | Priority: Medium | Component: CLI | Complexity: Simple

Root cause confirmed: _is_interactive_session() calls sys.stdin.isatty() before the "mcp" subcommand guard runs. When the MCP stdio transport closes stdin/stdout on shutdown, isatty() raises ValueError: I/O operation on closed file.

Fix applied in src/basic_memory/cli/promo.py: wrapped the isatty() calls in a try/except ValueError — closed streams are treated as non-interactive, so the promo is silently skipped.

Two new tests added in tests/cli/test_cloud_promo.py:

• test_is_interactive_session_returns_false_on_closed_stdin

• test_is_interactive_session_returns_false_on_closed_stdout

• Read relevant source files

• Classify and triage the issue

• Add labels (bug)

• Implement the fix in promo.py

• Add tests for closed-file scenario

• Commit and push

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