fix(gateway): tighten httpx keepalive and close whatsapp typing-response leak (#18451)

Two mitigations for the CLOSE_WAIT accumulation reported against QQ Bot
+ Feishu on macOS behind Cloudflare Warp.

1. Shared httpx.Limits helper (gateway/platforms/_http_client_limits.py).
   Every long-lived platform adapter now constructs httpx.AsyncClient
   with max_keepalive_connections=10 and keepalive_expiry=2.0, vs httpx's
   default of unbounded keepalive pool and 5.0s expiry. On macOS/Warp the
   default 5s window let idle keepalive sockets sit in CLOSE_WAIT long
   enough for seven persistent adapters (QQ Bot, WeCom, DingTalk, Signal,
   BlueBubbles, WeCom-callback, plus the transient Feishu helper) to
   compound to the 256-fd ulimit. Tunable via
   HERMES_GATEWAY_HTTPX_KEEPALIVE_EXPIRY and
   HERMES_GATEWAY_HTTPX_MAX_KEEPALIVE env vars.

2. whatsapp.send_typing aiohttp leak. The call was
   'await self._http_session.post(...)' with no 'async with' and no
   variable capture — the ClientResponse went out of scope unclosed,
   holding its TCP socket in CLOSE_WAIT until GC. Fixed by wrapping in
   'async with'. This was the only bare-await aiohttp leak in the
   gateway/tools/plugins tree per audit; all other aiohttp sites use
   the context-manager pattern correctly.

The underlying reporter also saw Feishu SDK (lark-oapi) connections in
CLOSE_WAIT — those are inside the SDK and out of our direct control, but
tightening httpx keepalive across adapters reduces the aggregate pool
pressure regardless of which individual adapter leaks.

gateway/platforms/_http_client_limits.py

@@ -0,0 +1,84 @@
+"""Shared HTTP client factory for long-lived platform adapters.
+
+Gateway messaging platforms (QQ Bot, Feishu, WeCom, DingTalk, Signal,
+BlueBubbles, WeCom-callback) keep a persistent ``httpx.AsyncClient``
+alive for the adapter's lifetime.  That amortises TLS/connection setup
+across many API calls, but it also means the process's file-descriptor
+pressure is sensitive to how aggressively the pool recycles idle keep-
+alive connections.
+
+httpx's default ``keepalive_expiry`` is 5 seconds.  On macOS behind
+Cloudflare Warp (and other transparent proxies), peer-initiated FIN can
+sit in ``CLOSE_WAIT`` longer than that before the local socket actually
+drains — which, multiplied across 7 long-lived adapters plus the LLM
+client and MCP clients, walks straight into the default 256 fd limit.
+See #18451.
+
+``platform_httpx_limits()`` returns a tighter ``httpx.Limits`` the
+adapter factories use instead of the httpx default.  The values chosen:
+
+* ``max_keepalive_connections=10`` — plenty for any single adapter;
+  platform APIs rarely parallelise beyond this.
+* ``keepalive_expiry=2.0`` — close idle sockets aggressively so a
+  proxy's lingering CLOSE_WAIT window can't starve the process.
+
+Override via ``HERMES_GATEWAY_HTTPX_KEEPALIVE_EXPIRY`` /
+``HERMES_GATEWAY_HTTPX_MAX_KEEPALIVE`` env vars when tuning under load.
+"""
+
+from __future__ import annotations
+
+import os
+
+try:
+    import httpx
+except ImportError:  # pragma: no cover — optional dep
+    httpx = None  # type: ignore[assignment]
+
+
+_DEFAULT_KEEPALIVE_EXPIRY_S = 2.0
+_DEFAULT_MAX_KEEPALIVE = 10
+
+
+def platform_httpx_limits() -> "httpx.Limits | None":
+    """Return ``httpx.Limits`` tuned for persistent platform-adapter clients.
+
+    Returns ``None`` when httpx isn't importable, so callers can fall
+    back to httpx's built-in default without a hard dependency on this
+    helper being reachable.
+    """
+    if httpx is None:
+        return None
+
+    def _env_float(name: str, default: float) -> float:
+        raw = os.environ.get(name, "").strip()
+        if not raw:
+            return default
+        try:
+            val = float(raw)
+        except (TypeError, ValueError):
+            return default
+        return val if val > 0 else default
+
+    def _env_int(name: str, default: int) -> int:
+        raw = os.environ.get(name, "").strip()
+        if not raw:
+            return default
+        try:
+            val = int(raw)
+        except (TypeError, ValueError):
+            return default
+        return val if val > 0 else default
+
+    keepalive_expiry = _env_float(
+        "HERMES_GATEWAY_HTTPX_KEEPALIVE_EXPIRY", _DEFAULT_KEEPALIVE_EXPIRY_S
+    )
+    max_keepalive = _env_int(
+        "HERMES_GATEWAY_HTTPX_MAX_KEEPALIVE", _DEFAULT_MAX_KEEPALIVE
+    )
+
+    return httpx.Limits(
+        max_keepalive_connections=max_keepalive,
+        # Leave max_connections at httpx default (100) — plenty of headroom.
+        keepalive_expiry=keepalive_expiry,
+    )

gateway/platforms/bluebubbles.py

@@ -162,7 +162,9 @@ class BlueBubblesAdapter(BasePlatformAdapter):
             return False
         from aiohttp import web
 
-        self.client = httpx.AsyncClient(timeout=30.0)
+        # Tighter keepalive so idle CLOSE_WAIT drains promptly (#18451).
+        from gateway.platforms._http_client_limits import platform_httpx_limits
+        self.client = httpx.AsyncClient(timeout=30.0, limits=platform_httpx_limits())
         try:
             await self._api_get("/api/v1/ping")
             info = await self._api_get("/api/v1/server/info")

gateway/platforms/dingtalk.py

@@ -228,7 +228,11 @@ class DingTalkAdapter(BasePlatformAdapter):
             return False
 
         try:
-            self._http_client = httpx.AsyncClient(timeout=30.0)
+            # Tighter keepalive so idle CLOSE_WAIT drains promptly (#18451).
+            from gateway.platforms._http_client_limits import platform_httpx_limits
+            self._http_client = httpx.AsyncClient(
+                timeout=30.0, limits=platform_httpx_limits(),
+            )
 
             credential = dingtalk_stream.Credential(
                 self._client_id, self._client_secret

gateway/platforms/qqbot/adapter.py

@@ -243,10 +243,14 @@ class QQAdapter(BasePlatformAdapter):
             return False
 
         try:
+            # Tighter keepalive pool so idle CLOSE_WAIT sockets drain
+            # faster behind proxies like Cloudflare Warp (#18451).
+            from gateway.platforms._http_client_limits import platform_httpx_limits
             self._http_client = httpx.AsyncClient(
                 timeout=30.0,
                 follow_redirects=True,
                 event_hooks={"response": [_ssrf_redirect_guard]},
+                limits=platform_httpx_limits(),
             )
 
             # 1. Get access token

gateway/platforms/signal.py

@@ -248,7 +248,9 @@ class SignalAdapter(BasePlatformAdapter):
         except Exception as e:
             logger.warning("Signal: Could not acquire phone lock (non-fatal): %s", e)
 
-        self.client = httpx.AsyncClient(timeout=30.0)
+        # Tighter keepalive so idle CLOSE_WAIT drains promptly (#18451).
+        from gateway.platforms._http_client_limits import platform_httpx_limits
+        self.client = httpx.AsyncClient(timeout=30.0, limits=platform_httpx_limits())
         try:
             # Health check — verify signal-cli daemon is reachable
             try:

gateway/platforms/wecom.py

@@ -206,7 +206,11 @@ class WeComAdapter(BasePlatformAdapter):
             return False
 
         try:
-            self._http_client = httpx.AsyncClient(timeout=30.0, follow_redirects=True)
+            # Tighter keepalive so idle CLOSE_WAIT drains promptly (#18451).
+            from gateway.platforms._http_client_limits import platform_httpx_limits
+            self._http_client = httpx.AsyncClient(
+                timeout=30.0, follow_redirects=True, limits=platform_httpx_limits(),
+            )
             await self._open_connection()
             self._mark_connected()
             self._listen_task = asyncio.create_task(self._listen_loop())

gateway/platforms/wecom_callback.py

@@ -119,7 +119,9 @@ class WecomCallbackAdapter(BasePlatformAdapter):
             pass
 
         try:
-            self._http_client = httpx.AsyncClient(timeout=20.0)
+            # Tighter keepalive so idle CLOSE_WAIT drains promptly (#18451).
+            from gateway.platforms._http_client_limits import platform_httpx_limits
+            self._http_client = httpx.AsyncClient(timeout=20.0, limits=platform_httpx_limits())
             self._app = web.Application()
             self._app.router.add_get("/health", self._handle_health)
             self._app.router.add_get(self._path, self._handle_verify)

gateway/platforms/whatsapp.py

@@ -902,11 +902,15 @@ class WhatsAppAdapter(BasePlatformAdapter):
         try:
             import aiohttp
 
-            await self._http_session.post(
+            # Must wrap in `async with` — a bare `await session.post(...)`
+            # leaves the response object alive until GC, holding its TCP
+            # socket in CLOSE_WAIT. See #18451.
+            async with self._http_session.post(
                 f"http://127.0.0.1:{self._bridge_port}/typing",
                 json={"chatId": chat_id},
                 timeout=aiohttp.ClientTimeout(total=5)
-            )
+            ):
+                pass
         except Exception:
             pass  # Ignore typing indicator failures