fix(agent): do not persist runtime context metadata in session history

nanobot/agent/loop.py

@@ -467,6 +467,14 @@ class AgentLoop:
                 content = entry["content"]
                 if len(content) > self._TOOL_RESULT_MAX_CHARS:
                     entry["content"] = content[:self._TOOL_RESULT_MAX_CHARS] + "\n... (truncated)"
+            if (
+                entry.get("role") == "user"
+                and isinstance(entry.get("content"), str)
+                and entry["content"].startswith(ContextBuilder._RUNTIME_CONTEXT_TAG)
+            ):
+                # Runtime metadata is injected per-turn for model context only; do not persist it
+                # into long-lived session history to avoid semantic drift and repetitive replies.
+                continue
             if entry.get("role") == "user" and isinstance(entry.get("content"), list):
                 entry["content"] = [
                     {"type": "text", "text": "[image]"} if (