refactor(mcp): make trust_env configurable (default True) instead of hardcoded

Author: adrienduchemin

src/mistralai/extra/mcp/streamable_http.py

@@ -22,6 +22,11 @@ class StreamableHTTPServerParams(BaseModel):
     url: str
     headers: dict[str, Any] | None = None
     timeout: float = 30
+    # Whether the httpx client trusts the ambient environment (HTTP(S)_PROXY,
+    # SSL_CERT_FILE/DIR, .netrc). Defaults to httpx's default (True). Set False to
+    # reach the endpoint directly without an ambient egress proxy, e.g. for an
+    # in-cluster URL on a host whose external egress is proxied.
+    trust_env: bool = True
 
 
 class MCPClientStreamableHTTP(MCPClientBase):
@@ -50,15 +55,16 @@ async def _get_transport(
         MemoryObjectReceiveStream[SessionMessage | Exception],
         MemoryObjectSendStream[SessionMessage],
     ]:
-        # trust_env=False so the client does not inherit an ambient HTTP(S)_PROXY:
-        # the MCP endpoint is reached directly, and routing it through an egress
-        # proxy meant for external traffic can make the connection hang.
+        # trust_env controls whether the client inherits the ambient
+        # HTTP(S)_PROXY / cert / netrc env. Set it False (see params) to reach an
+        # in-cluster endpoint directly, bypassing a proxy meant for external
+        # traffic that would make the connection hang.
         http_client = await exit_stack.enter_async_context(
             httpx.AsyncClient(
                 headers=self._params.headers,
                 timeout=self._params.timeout,
                 follow_redirects=True,
-                trust_env=False,
+                trust_env=self._params.trust_env,
             )
         )
         read_stream, write_stream, _ = await exit_stack.enter_async_context(