Summary

Fixes #40383. The Yuanbao adapter consistently added a fixed ~5s delay to gateway shutdown even when idle. This bounds the WS close handshake so a non-responsive server can no longer stall teardown.

Root cause

ConnectionManager._cleanup_ws() (gateway/platforms/yuanbao.py) awaited ws.close() unbounded. The connection is opened with close_timeout=5, so the websockets close handshake blocks up to 5s waiting for the server's close-frame echo. On an idle shutdown the server never replies, so teardown always waited the full ~5s — matching the reporter's ✓ yuanbao disconnected (5.01s) log.

Call path: gateway.run times adapter.disconnect() → ConnectionManager.close() (cancels heartbeat/recv tasks — fast) → await self._cleanup_ws() → await ws.close() ← the entire ~5s lives here.

Fix

Bound the close await with asyncio.wait_for(ws.close(), timeout=WS_CLOSE_TIMEOUT_S) (1.0s, new module constant near the other WS timeouts). A responsive server completes the handshake in well under a second, so this only caps the pathological hang; the graceful close is still attempted on the fast path. The reconnect paths that reuse _cleanup_ws() benefit too. asyncio.TimeoutError is swallowed alongside the pre-existing except Exception (it is a subclass), dropping a dead connection rather than stalling.

Tests

New tests/test_yuanbao_shutdown.py (3 cases):

• hung server (close never echoes) — teardown stays bounded (~1.0s, was ~5.0s)
• responsive server — fast path returns immediately
• close() raises — ws reference still cleared

scripts/run_tests.sh over all 6 Yuanbao test files: 220 passed. The new file alone went 5.13s → 1.2s once bounded. ruff + scripts/check-windows-footguns.py clean on both changed files.

Scope

Deliberately unchanged: the close_timeout=5 on the two websockets.connect() sites (it governs the library's own handshake cap and is now superseded by the shorter outer bound during teardown); the heartbeat/recv-task cancellation in ConnectionManager.close() (already fast). No behavior change for a server that closes promptly.