diff --git a/constraints/py313-mcp.txt b/constraints/py313-mcp.txt
index f605b1a7..5065fcfc 100644
--- a/constraints/py313-mcp.txt
+++ b/constraints/py313-mcp.txt
@@ -3,7 +3,7 @@
 #   python -m pip install --constraint constraints/py313-mcp.txt "ainativelang[mcp]"
 #
 # These pins are validated in CI install smoke/wheel jobs.
-mcp==1.27.0
+mcp==1.27.1
 anyio==4.13.0
 httpx==0.28.1
 httpx-sse==0.4.3