fix: dict anomaly access, configurable fail mode, exception type logging

- Add get_anomaly_attr() helper that handles both dict and object
  anomalies. The SDK's send_message() returns dicts, so getattr()
  was silently returning defaults -- critical blocking never triggered.
- Fix field name: "detail" -> "details" (matches SDK schema).
- Make fail-open/fail-closed configurable via INSAITS_FAIL_MODE env var
  (defaults to "open" for backward compatibility).
- Include exception type name in fail-open log for diagnostics.
- Normalize severity comparison with .upper() for case-insensitive matching.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

scripts/hooks/insaits-security-monitor.py

@@ -40,6 +40,8 @@ Environment variables:
   INSAITS_DEV_MODE   Set to "true" to enable dev mode (no API key needed).
                      Defaults to "false" (strict mode).
   INSAITS_MODEL      LLM model identifier for fingerprinting. Default: claude-opus.
+  INSAITS_FAIL_MODE  "open" (default) = continue on SDK errors.
+                     "closed" = block tool execution on SDK errors.
   INSAITS_VERBOSE    Set to any value to enable debug logging.
 
 Detections include:
@@ -141,6 +143,18 @@ def write_audit(event: Dict[str, Any]) -> None:
         log.warning("Failed to write audit log %s: %s", AUDIT_FILE, exc)
 
 
+def get_anomaly_attr(anomaly: Any, key: str, default: str = "") -> str:
+    """Get a field from an anomaly that may be a dict or an object.
+
+    The SDK's ``send_message()`` returns anomalies as dicts, while
+    other code paths may return dataclass/object instances.  This
+    helper handles both transparently.
+    """
+    if isinstance(anomaly, dict):
+        return str(anomaly.get(key, default))
+    return str(getattr(anomaly, key, default))
+
+
 def format_feedback(anomalies: List[Any]) -> str:
     """Format detected anomalies as feedback for Claude Code.
 
@@ -152,9 +166,9 @@ def format_feedback(anomalies: List[Any]) -> str:
         "",
     ]
     for i, a in enumerate(anomalies, 1):
-        sev: str = getattr(a, "severity", "MEDIUM")
-        atype: str = getattr(a, "type", "UNKNOWN")
-        detail: str = getattr(a, "detail", "")
+        sev: str = get_anomaly_attr(a, "severity", "MEDIUM")
+        atype: str = get_anomaly_attr(a, "type", "UNKNOWN")
+        detail: str = get_anomaly_attr(a, "details", "")
         lines.extend([
             f"{i}. [{sev}] {atype}",
             f"   {detail[:120]}",
@@ -203,7 +217,17 @@ def main() -> None:
             llm_id=os.environ.get("INSAITS_MODEL", DEFAULT_MODEL),
         )
     except Exception as exc:
-        log.warning("SDK error, skipping security scan: %s", exc)
+        fail_mode: str = os.environ.get("INSAITS_FAIL_MODE", "open").lower()
+        if fail_mode == "closed":
+            sys.stdout.write(
+                f"InsAIts SDK error ({type(exc).__name__}); "
+                "blocking execution to avoid unscanned input.\n"
+            )
+            sys.exit(2)
+        log.warning(
+            "SDK error (%s), skipping security scan: %s",
+            type(exc).__name__, exc,
+        )
         sys.exit(0)
 
     anomalies: List[Any] = result.get("anomalies", [])
@@ -213,7 +237,7 @@ def main() -> None:
         "tool": data.get("tool_name", "unknown"),
         "context": context,
         "anomaly_count": len(anomalies),
-        "anomaly_types": [getattr(a, "type", "") for a in anomalies],
+        "anomaly_types": [get_anomaly_attr(a, "type") for a in anomalies],
         "text_length": len(text),
     })
 
@@ -223,7 +247,7 @@ def main() -> None:
 
     # Determine maximum severity
     has_critical: bool = any(
-        getattr(a, "severity", "") in ("CRITICAL", "critical") for a in anomalies
+        get_anomaly_attr(a, "severity").upper() in ("CRITICAL",) for a in anomalies
     )
 
     feedback: str = format_feedback(anomalies)