hermes - 💡(How to fix) Fix concurrency: TOCTOU race in get_async_client() leaks orphaned async HTTP client

Summary

tools/openrouter_client.py:get_async_client() has a time-of-check/time-of-use (TOCTOU) race that can create multiple orphaned async HTTP clients, causing resource leaks and potential process-exit hangs.

Root Cause

_client = None

def get_async_client():
    global _client
    if _client is None:                              # ← both threads pass
        client, _model = resolve_provider_client(...)  # ← both create client
        _client = client                             # ← second write wins
    return _client

Two threads calling get_async_client() concurrently can both observe _client is None, both call resolve_provider_client("openrouter", async_mode=True), and race to write _client. The loser's async client is never returned or closed, leaving an orphaned httpx.AsyncClient with an open connection pool.

Impact

• Resource leak: orphaned async client holds OS file descriptors for the HTTP connection pool
• Process-exit hang / ResourceWarning: httpx.AsyncClient and AsyncHttpxClientWrapper emit warnings (or block) when their pools are garbage-collected after the event loop is closed — this is the root of the AsyncHttpxClientWrapper.__del__ noise that agent/auxiliary_client.py already documents and workarounds

Expected Fix

Double-checked locking, consistent with the pattern used in agent/auxiliary_client.py (which already has _client_cache_lock):

import threading

_client = None
_client_lock = threading.Lock()

def get_async_client():
    global _client
    if _client is None:
        with _client_lock:
            if _client is None:
                client, _model = resolve_provider_client("openrouter", async_mode=True)
                if client is None:
                    raise ValueError("OPENROUTER_API_KEY environment variable not set")
                _client = client
    return _client