Four fixes for MCP server stability issues reported by community member
(terminal lockup, zombie processes, escape sequence pollution, startup hang):
1. MCP reload timeout guard (cli.py): _check_config_mcp_changes now runs
_reload_mcp in a separate daemon thread with a 30s hard timeout. Previously,
a hung MCP server could block the process_loop thread indefinitely, freezing
the entire TUI (user can type but nothing happens, only Ctrl+D/Ctrl+\ work).
2. MCP stdio subprocess PID tracking (mcp_tool.py): Tracks child PIDs spawned
by stdio_client via before/after snapshots of /proc children. On shutdown,
_stop_mcp_loop force-kills any tracked PIDs that survived the SDK's graceful
SIGTERM→SIGKILL cleanup. Prevents zombie MCP server processes from
accumulating across sessions.
3. MCP event loop exception handler (mcp_tool.py): Installs
_mcp_loop_exception_handler on the MCP background event loop — same pattern
as the existing _suppress_closed_loop_errors on prompt_toolkit's loop.
Suppresses benign 'Event loop is closed' RuntimeError from httpx transport
__del__ during MCP shutdown. Salvaged from PR #2538 (acsezen).
4. MCP OAuth non-blocking (mcp_oauth.py): Replaces blocking input() call in
_wait_for_callback with OAuthNonInteractiveError raise. Adds _is_interactive()
TTY detection. In non-interactive environments, build_oauth_auth() still
returns a provider (cached tokens + refresh work), but the callback handler
raises immediately instead of blocking the MCP event loop for 120s. Re-raises
OAuth setup failures in _run_http so failed servers are reported cleanly
without blocking others. Salvaged from PRs #4521 (voidborne-d) and #4465
(heathley).
Closes#2537, closes#4462
Related: #4128, #3436
cc54818d26