fix: is_public_blocked_tool crashes on a truthy non-string tool name (#1620)

* fix: is_public_blocked_tool crashes on a truthy non-string tool name

* fix: is_public_blocked_tool fails closed (blocks) on a malformed non-string tool name

tests/test_public_blocked_tool_nonstring.py

@@ -0,0 +1,25 @@
+"""Regression: is_public_blocked_tool must fail CLOSED on a non-string tool name.
+
+The `if not tool_name` guard only handled falsy values; a truthy non-string
+(e.g. 5 or a list) reached `tool_name.startswith("mcp__")` and raised
+AttributeError/TypeError. Because this is a public-execution security gate, a
+malformed (non-string) identifier must be treated as BLOCKED, not silently
+allowed. None/empty mean there is no tool to gate.
+"""
+from src.tool_security import is_public_blocked_tool
+
+
+def test_malformed_non_string_name_is_blocked():
+    # Fail closed: a non-string identifier cannot be validated, so block it.
+    assert is_public_blocked_tool(5) is True
+    assert is_public_blocked_tool(["bash"]) is True
+    assert is_public_blocked_tool({"x": 1}) is True
+
+
+def test_none_or_empty_is_not_gated():
+    assert is_public_blocked_tool(None) is False
+    assert is_public_blocked_tool("") is False
+
+
+def test_real_tool_names_still_classified():
+    assert is_public_blocked_tool("mcp__whatever") is True