Fix auto-detection of HTTP proxy settings (#2917)

Signed-off-by: maxnilz <[email protected]>
Co-authored-by: Douwe Maan <[email protected]>

Author: maxnilz

pydantic_ai_slim/pydantic_ai/models/__init__.py

@@ -783,6 +783,8 @@ def cached_async_http_client(*, provider: str | None = None, timeout: int = 600,
     The client is cached based on the provider parameter. If provider is None, it's used for non-provider specific
     requests (like downloading images). Multiple agents and calls can share the same client when they use the same provider.
 
+    Each client will get its own transport with its own connection pool. The default pool size is defined by `httpx.DEFAULT_LIMITS`.
+
     There are good reasons why in production you should use a `httpx.AsyncClient` as an async context manager as
     described in [encode/httpx#2026](https://github.com/encode/httpx/pull/2026), but when experimenting or showing
     examples, it's very useful not to.
@@ -793,6 +795,8 @@ def cached_async_http_client(*, provider: str | None = None, timeout: int = 600,
     client = _cached_async_http_client(provider=provider, timeout=timeout, connect=connect)
     if client.is_closed:
         # This happens if the context manager is used, so we need to create a new client.
+        # Since there is no API from `functools.cache` to clear the cache for a specific
+        #  key, clear the entire cache here as a workaround.
         _cached_async_http_client.cache_clear()
         client = _cached_async_http_client(provider=provider, timeout=timeout, connect=connect)
     return client
@@ -801,17 +805,11 @@ def cached_async_http_client(*, provider: str | None = None, timeout: int = 600,
 @cache
 def _cached_async_http_client(provider: str | None, timeout: int = 600, connect: int = 5) -> httpx.AsyncClient:
     return httpx.AsyncClient(
-        transport=_cached_async_http_transport(),
         timeout=httpx.Timeout(timeout=timeout, connect=connect),
         headers={'User-Agent': get_user_agent()},
     )
 
 
-@cache
-def _cached_async_http_transport() -> httpx.AsyncHTTPTransport:
-    return httpx.AsyncHTTPTransport()
-
-
 DataT = TypeVar('DataT', str, bytes)