A stdio MCP server that completes the initialize + tools/list handshake and then exits cleanly will fire `transport.onClose` on every clean exit, and the old `MCPManager.reconnectServer` path spawned again unconditionally. A misconfigured PHP-shebang MCP (e.g. Laravel Boost in a non-Laravel project) hit this loop and forked 66 487 `php84` processes parented directly to the agent's `bun` PID until macOS force-rebooted.
Add a per-server sliding-window circuit breaker: at most 5 reconnect attempts per 30 s window. The transport `onClose` callback and the per-tool-call retry in `tool-bridge` are subject to the breaker; `/mcp reconnect` passes `{ manual: true }` to reset the window so users can recover after fixing the underlying misconfiguration. Stale `onClose` is detached when the breaker trips so a late EOF event cannot re-arm the loop.
Defended by `mcp-reconnect-storm.test.ts`: a Bun stdio fixture answers the handshake and exits, then asserts the spawn count stays at ≤ 10 (was 127 without the fix).
Fixes#1592
roboomp
230514d937