fix: Handle empty store similarity (numpy) (#2602)

libs/checkpoint/langgraph/store/memory/__init__.py

@@ -413,6 +413,8 @@ def _cosine_similarity(X: list[float], Y: list[list[float]]) -> list[float]:
     Compute cosine similarity between a vector X and a matrix Y.
     Lazy import numpy for efficiency.
     """
+    if not Y:
+        return []
     if _check_numpy():
         import numpy as np  # type: ignore
 

libs/checkpoint/pyproject.toml

@@ -1,6 +1,6 @@
 [tool.poetry]
 name = "langgraph-checkpoint"
-version = "2.0.7"
+version = "2.0.8"
 description = "Library with base interfaces for LangGraph checkpoint savers."
 authors = []
 license = "MIT"