fix: guard isatty() against ValueError on MCP stdio shutdown

When the MCP server runs over stdio transport, stdin/stdout are closed
before the call_on_close promo callback fires. sys.stdin.isatty() then
raises ValueError: I/O operation on closed file.

Wrap the isatty() calls in a try/except ValueError in
_is_interactive_session() so the promo is silently skipped rather than
crashing the shutdown path.

Fixes #607

Co-authored-by: bm-clawd <bm-clawd@users.noreply.github.com>
Signed-off-by: claude[bot] <41898282+claude[bot]@users.noreply.github.com>

src/basic_memory/cli/promo.py

@@ -24,7 +24,14 @@ def _promos_disabled_by_env() -> bool:
 
 def _is_interactive_session() -> bool:
     """Return whether stdin/stdout are interactive terminals."""
-    return sys.stdin.isatty() and sys.stdout.isatty()
+    try:
+        return sys.stdin.isatty() and sys.stdout.isatty()
+    except ValueError:
+        # Trigger: stdin/stdout already closed (e.g., MCP stdio transport shutdown).
+        # Why: isatty() raises ValueError on closed file objects; treat as non-interactive
+        # so the promo is suppressed rather than crashing the shutdown path.
+        # Outcome: promo skipped for this invocation.
+        return False
 
 
 def _build_cloud_promo_message() -> str:

tests/cli/test_cloud_promo.py

@@ -20,6 +20,43 @@ def _capture_console() -> tuple[Console, StringIO]:
     return Console(file=buf, force_terminal=True), buf
 
 
+# --- _is_interactive_session tests ---
+
+
+def test_is_interactive_session_returns_false_on_closed_stdin(monkeypatch):
+    """isatty() raises ValueError when stdio is closed (e.g., MCP shutdown)."""
+    import sys
+
+    from basic_memory.cli.promo import _is_interactive_session
+
+    class _ClosedStdin:
+        def isatty(self):
+            raise ValueError("I/O operation on closed file")
+
+    monkeypatch.setattr(sys, "stdin", _ClosedStdin())
+    assert _is_interactive_session() is False
+
+
+def test_is_interactive_session_returns_false_on_closed_stdout(monkeypatch):
+    """isatty() raises ValueError on closed stdout (e.g., MCP shutdown)."""
+    import sys
+
+    from basic_memory.cli.promo import _is_interactive_session
+
+    class _ClosedStdout:
+        def isatty(self):
+            raise ValueError("I/O operation on closed file")
+
+    # stdin reports interactive, but stdout is closed
+    class _InteractiveStdin:
+        def isatty(self):
+            return True
+
+    monkeypatch.setattr(sys, "stdin", _InteractiveStdin())
+    monkeypatch.setattr(sys, "stdout", _ClosedStdout())
+    assert _is_interactive_session() is False
+
+
 # --- maybe_show_init_line tests ---