diff --git a/tests/test_litellm/proxy/_experimental/mcp_server/conftest.py b/tests/test_litellm/proxy/_experimental/mcp_server/conftest.py
new file mode 100644
index 00000000000..b477bf3f406
--- /dev/null
+++ b/tests/test_litellm/proxy/_experimental/mcp_server/conftest.py
@@ -0,0 +1,22 @@
+import os
+
+import pytest
+
+
+@pytest.fixture(autouse=True)
+def _hermetic_server_root_path():
+    """Isolate MCP discovery tests from a leaked ``SERVER_ROOT_PATH``.
+
+    ``tests/test_litellm/proxy/test_custom_proxy.py`` sets ``SERVER_ROOT_PATH`` at import time
+    (its app mounts under a custom path) and never restores it, so in a shared shard the value
+    leaks into this process. The discovery routes and the 401 challenges read it, so a leaked
+    value would silently rewrite every ``resource_metadata`` URL and make these tests depend on
+    shard ordering. Clearing it here pins the default (root-mounted) deployment; a test that
+    exercises a sub-path deployment sets the value explicitly within its own body.
+    """
+    saved = os.environ.pop("SERVER_ROOT_PATH", None)
+    try:
+        yield
+    finally:
+        if saved is not None:
+            os.environ["SERVER_ROOT_PATH"] = saved