Reject non-mapping agent registry entries

adapter/matrix/agent_registry.py

@@ -1,6 +1,7 @@
 from __future__ import annotations
 
 from dataclasses import dataclass
+from collections.abc import Mapping
 from pathlib import Path
 
 import yaml
@@ -37,6 +38,8 @@ def load_agent_registry(path: str | Path) -> AgentRegistry:
     agents: list[AgentDefinition] = []
     seen: set[str] = set()
     for entry in entries:
+        if not isinstance(entry, Mapping):
+            raise AgentRegistryError("each agent entry requires id and label")
         agent_id = str(entry.get("id", "")).strip()
         label = str(entry.get("label", "")).strip()
         if not agent_id or not label:

tests/adapter/matrix/test_agent_registry.py

@@ -35,3 +35,15 @@ def test_load_agent_registry_rejects_duplicate_ids(tmp_path: Path):
 
     with pytest.raises(AgentRegistryError, match="duplicate agent id"):
         load_agent_registry(path)
+
+
+def test_load_agent_registry_rejects_non_mapping_entries(tmp_path: Path):
+    path = tmp_path / "agents.yaml"
+    path.write_text(
+        "agents:\n"
+        "  - agent-1\n",
+        encoding="utf-8",
+    )
+
+    with pytest.raises(AgentRegistryError, match="each agent entry requires id and label"):
+        load_agent_registry(path)