diff --git a/py/src/braintrust/logger.py b/py/src/braintrust/logger.py
index 9a65dee3..3b2532d5 100644
--- a/py/src/braintrust/logger.py
+++ b/py/src/braintrust/logger.py
@@ -382,6 +382,18 @@ def __exit__(
 NOOP_SPAN: Span = _NoopSpan()
 NOOP_SPAN_PERMALINK = "https://www.braintrust.dev/noop-span"
 
+_V1_PROXY_SUFFIX = "/v1/proxy"
+
+
+def _normalize_proxy_conn_url(proxy_url: str) -> str:
+    # proxy_url may point at the universal proxy (`{api_url}/v1/proxy`) for
+    # EU/self-hosted orgs, but proxy_conn only targets Braintrust API endpoints
+    # (e.g. function/invoke, function/sandbox-list) served at the API host root.
+    # Drop the suffix so these requests resolve on all data planes.
+    if proxy_url.endswith(_V1_PROXY_SUFFIX):
+        return proxy_url[: -len(_V1_PROXY_SUFFIX)]
+    return proxy_url
+
 
 class BraintrustState:
     def __init__(self):
@@ -609,7 +621,7 @@ def proxy_conn(self):
         if not self._proxy_conn:
             if not self.proxy_url:
                 raise RuntimeError("Must initialize proxy_url before requesting proxy_conn")
-            self._proxy_conn = HTTPConnection(self.proxy_url, adapter=_http_adapter)
+            self._proxy_conn = HTTPConnection(_normalize_proxy_conn_url(self.proxy_url), adapter=_http_adapter)
         return self._proxy_conn
 
     def user_info(self) -> Mapping[str, Any]:
diff --git a/py/src/braintrust/test_logger.py b/py/src/braintrust/test_logger.py
index 3fc5c833..459f4b06 100644
--- a/py/src/braintrust/test_logger.py
+++ b/py/src/braintrust/test_logger.py
@@ -3868,6 +3868,20 @@ def test_check_org_info_with_git_metadata_uses_server_settings():
     assert set(state.git_metadata_settings.fields) == {"commit", "branch"}
 
 
+def test_proxy_conn_strips_v1_proxy_suffix():
+    """EU/self-hosted proxy_url ends in /v1/proxy; proxy_conn must target the API host root."""
+    state = BraintrustState()
+    state.proxy_url = "https://api-eu.braintrust.dev/v1/proxy"
+    assert state.proxy_conn().base_url == "https://api-eu.braintrust.dev"
+
+
+def test_proxy_conn_leaves_bare_host_unchanged():
+    """A bare proxy host (US default) is used as-is."""
+    state = BraintrustState()
+    state.proxy_url = "https://api.braintrust.dev"
+    assert state.proxy_conn().base_url == "https://api.braintrust.dev"
+
+
 def test_get_repo_info_without_settings_returns_none():
     """Direct call to get_repo_info with settings=None should return None."""
     assert get_repo_info(None) is None