fix: fail-closed on non-object JSON and surface HOL Guard denial in result

- Return False for non-dict verdicts (e.g. [], "allow", null) to avoid
  AttributeError and preserve fail-closed behavior (CodeRabbit)
- Set ToolResponse.result to the denial message since the agent tool
  executor returns result and discards error, so denials reach the model
  instead of a null result (Greptile)
- Add non-object JSON regression test; update block test assertion

Co-authored-by: Mervin Praison <[email protected]>

examples/middleware/hol_guard_tool_policy.py

@@ -65,6 +65,9 @@ def _inspect_with_hol_guard(command: str) -> bool:
     except (json.JSONDecodeError, ValueError):
         return False
 
+    if not isinstance(verdict, dict):
+        return False
+
     decision = str(verdict.get("decision", "")).lower()
     return decision in ("allow", "benign")
 
@@ -80,10 +83,15 @@ def hol_guard_tool_policy(request: ToolRequest, call_next):
     if _inspect_with_hol_guard(command):
         return call_next(request)
 
+    blocked_message = "Blocked by HOL Guard: command was not explicitly allowed."
+    # Surface the denial in `result` too: the agent tool executor returns
+    # `ToolResponse.result` to the model and discards `error`, so a denial with
+    # only `error` set would reach the model as a null result. Keeping `error`
+    # populated preserves the signal for after_tool hooks and logging.
     return ToolResponse(
         tool_name=request.tool_name,
-        result=None,
-        error="Blocked by HOL Guard: command was not explicitly allowed.",
+        result=blocked_message,
+        error=blocked_message,
         context=request.context,
     )
 

src/praisonai-agents/tests/unit/hooks/test_hol_guard_tool_policy.py

@@ -84,7 +84,9 @@ def test_block_verdict_does_not_execute():
 
     assert executed == []
     assert result.error is not None
-    assert result.result is None
+    # The denial message is surfaced in `result` too, because the agent tool
+    # executor returns `ToolResponse.result` to the model and discards `error`.
+    assert result.result == result.error
 
 
 def test_missing_cli_fails_closed():
@@ -122,6 +124,27 @@ def test_malformed_json_fails_closed():
     assert result.error is not None
 
 
+def test_non_object_json_fails_closed():
+    module = _load_example()
+    executed = []
+
+    def call_next(req):
+        executed.append(req)
+        return "ran"
+
+    for payload in ("[]", '"allow"', "null"):
+        with patch.object(module.shutil, "which", return_value="/usr/bin/hol-guard"), \
+             patch.object(
+                 module.subprocess,
+                 "run",
+                 return_value=_FakeCompleted(0, payload),
+             ):
+            result = module.hol_guard_tool_policy(_make_request(), call_next)
+
+        assert executed == []
+        assert result.error is not None
+
+
 def test_nonzero_exit_fails_closed():
     module = _load_example()
     executed = []