Record local agent reasoning and tool activity

apps/device-host-agent/host_agent/conversation_log.py

@@ -0,0 +1,29 @@
+from __future__ import annotations
+
+import json
+from datetime import UTC, datetime
+from pathlib import Path
+from threading import Lock
+from typing import Any
+
+
+class ConversationLogStore:
+    """Append-only local audit log for chat and tool activity."""
+
+    def __init__(self, path: str | Path) -> None:
+        self.path = Path(path)
+        self._lock = Lock()
+
+    def append(self, event: dict[str, Any]) -> None:
+        record = {"timestamp": datetime.now(UTC).isoformat(), **_safe(event)}
+        self.path.parent.mkdir(parents=True, exist_ok=True)
+        with self._lock, self.path.open("a", encoding="utf-8") as stream:
+            stream.write(json.dumps(record, ensure_ascii=True, default=str) + "\n")
+
+
+def _safe(value: Any) -> Any:
+    if isinstance(value, dict):
+        return {str(k): _safe(v) for k, v in value.items()}
+    if isinstance(value, list):
+        return [_safe(v) for v in value]
+    return value if isinstance(value, (str, int, float, bool)) or value is None else str(value)