diff --git a/.github/scripts/check_diff.py b/.github/scripts/check_diff.py
new file mode 100644
index 00000000..8823260f
--- /dev/null
+++ b/.github/scripts/check_diff.py
@@ -0,0 +1,35 @@
+import json
+import sys
+import os
+
+LANGCHAIN_DIRS = {
+    "libs/genai",
+    "libs/vertexai",
+}
+
+if __name__ == "__main__":
+    files = sys.argv[1:]
+    dirs_to_run = set()
+
+    if len(files) == 300:
+        # max diff length is 300 files - there are likely files missing
+        raise ValueError("Max diff reached. Please manually run CI on changed libs.")
+
+    for file in files:
+        if any(
+            file.startswith(dir_)
+            for dir_ in (
+                ".github/workflows",
+                ".github/tools",
+                ".github/actions",
+                "libs/core",
+                ".github/scripts/check_diff.py",
+            )
+        ):
+            dirs_to_run.update(LANGCHAIN_DIRS)
+        elif file.startswith("libs/"):
+            dirs_to_run.update(LANGCHAIN_DIRS)
+        else:
+            pass
+    json_output = json.dumps(list(dirs_to_run))
+    print(f"dirs-to-run={json_output}")