diff --git a/litellm/constants.py b/litellm/constants.py
index 88c57d3ce4c..6f11462cf5c 100644
--- a/litellm/constants.py
+++ b/litellm/constants.py
@@ -105,6 +105,11 @@ MCP_OAUTH2_TOKEN_CACHE_MIN_TTL = int(
     os.getenv("MCP_OAUTH2_TOKEN_CACHE_MIN_TTL", "10")
 )
 
+# MCP OAuth2 Token Exchange (OBO) Defaults
+MCP_TOKEN_EXCHANGE_CACHE_MAX_SIZE = int(
+    os.getenv("MCP_TOKEN_EXCHANGE_CACHE_MAX_SIZE", "500")
+)
+
 LITELLM_UI_ALLOW_HEADERS = [
     "x-litellm-semantic-filter",
     "x-litellm-semantic-filter-tools",