fix(skills): tolerate null requires/bins/env in skill metadata

tests/agent/test_skills_loader.py

@@ -436,3 +436,45 @@ def test_get_skill_metadata_handles_yaml_types(tmp_path: Path) -> None:
     assert meta.get("always") is True
     # metadata is a parsed dict, not a JSON string
     assert isinstance(meta.get("metadata"), dict)
+
+
+def test_check_requirements_tolerates_null_requires_and_lists(tmp_path: Path) -> None:
+    """Null requires/bins/env must not crash skill listing (JSON/YAML nulls)."""
+    workspace = tmp_path / "ws"
+    ws_skills = workspace / "skills"
+    ws_skills.mkdir(parents=True)
+    _write_skill(
+        ws_skills,
+        "null-requires",
+        metadata_json={"always": True, "requires": None},
+        body="# Null requires",
+    )
+    _write_skill(
+        ws_skills,
+        "null-bins",
+        metadata_json={"always": True, "requires": {"bins": None, "env": None}},
+        body="# Null bins",
+    )
+    _write_skill(
+        ws_skills,
+        "null-elems",
+        metadata_json={"always": True, "requires": {"bins": [None, ""], "env": [None]}},
+        body="# Null elems",
+    )
+    builtin = tmp_path / "builtin"
+    builtin.mkdir()
+    loader = SkillsLoader(workspace, builtin_skills_dir=builtin)
+
+    assert loader._check_requirements(loader._get_skill_meta("null-requires")) is True
+    assert loader._check_requirements(loader._get_skill_meta("null-bins")) is True
+    assert loader._check_requirements(loader._get_skill_meta("null-elems")) is True
+    always = loader.get_always_skills()
+    assert set(always) >= {"null-requires", "null-bins", "null-elems"}
+    listed = {e["name"] for e in loader.list_skills(filter_unavailable=True)}
+    assert {"null-requires", "null-bins", "null-elems"} <= listed
+    assert loader.get_skill_requirements("null-requires") == {
+        "bins": [],
+        "env": [],
+        "missing_bins": [],
+        "missing_env": [],
+    }