feat(ui): add codemirror json editor

server/src/agent_control_server/endpoints/controls.py

@@ -212,7 +212,25 @@ async def _validate_control_definition(
 
         evaluator_cls = available_evaluators.get(parsed.name)
         if evaluator_cls is None:
-            continue
+            available = list(available_evaluators.keys())
+            raise APIValidationError(
+                error_code=ErrorCode.EVALUATOR_NOT_FOUND,
+                detail=f"Evaluator '{parsed.name}' is not registered",
+                resource="Evaluator",
+                hint=(
+                    f"Check evaluator '{evaluator_ref}'. "
+                    f"Available evaluators: {available or 'none'}."
+                ),
+                errors=[
+                    ValidationErrorItem(
+                        resource="Control",
+                        field=f"{field_prefix}.evaluator.name",
+                        code="evaluator_not_found",
+                        message=f"Evaluator '{parsed.name}' not found",
+                        value=evaluator_ref,
+                    )
+                ],
+            )
 
         try:
             evaluator_cls.config_model(**evaluator_spec.config)

server/tests/test_controls_validation.py

@@ -318,3 +318,33 @@ def test_validation_nested_agent_scoped_evaluator_error_uses_bracketed_field_pat
         and err.get("code") == "evaluator_not_found"
         for err in body.get("errors", [])
     )
+
+
+def test_validation_standalone_evaluator_error_uses_bracketed_field_path(
+    client: TestClient,
+):
+    """Standalone evaluator failures should identify the exact nested leaf path."""
+    control_id = create_control(client)
+    payload = deepcopy(VALID_CONTROL_PAYLOAD)
+    payload["condition"] = {
+        "or": [
+            {
+                "selector": {"path": "input"},
+                "evaluator": {
+                    "name": "missing-evaluator",
+                    "config": {},
+                },
+            }
+        ]
+    }
+
+    resp = client.put(f"/api/v1/controls/{control_id}/data", json={"data": payload})
+
+    assert resp.status_code == 422
+    body = resp.json()
+    assert body["error_code"] == "EVALUATOR_NOT_FOUND"
+    assert any(
+        err.get("field") == "data.condition.or[0].evaluator.name"
+        and err.get("code") == "evaluator_not_found"
+        for err in body.get("errors", [])
+    )

ui/package.json

@@ -39,7 +39,14 @@
     "prettify:check": "Check formatting with Prettier without changing files"
   },
   "dependencies": {
+    "@codemirror/autocomplete": "^6.20.1",
+    "@codemirror/lang-json": "^6.0.2",
+    "@codemirror/language": "^6.12.3",
+    "@codemirror/lint": "^6.9.5",
+    "@codemirror/state": "^6.6.0",
+    "@codemirror/view": "^6.40.0",
     "@emotion/is-prop-valid": "^1.4.0",
+    "@lezer/highlight": "^1.2.3",
     "@mantine/charts": "^7.17.8",
     "@mantine/code-highlight": "7.17.5",
     "@mantine/core": "7.17.5",
@@ -56,6 +63,10 @@
     "@tanstack/react-query": "5.74.4",
     "@tanstack/react-query-devtools": "5.72.2",
     "@tanstack/react-table": "8.20.5",
+    "@uiw/codemirror-extensions-basic-setup": "^4.25.9",
+    "@uiw/codemirror-themes": "^4.25.9",
+    "@uiw/codemirror-themes-all": "4.25.9",
+    "@uiw/react-codemirror": "^4.25.9",
     "axios": "1.12.0",
     "classix": "2.2.0",
     "date-fns": "4.1.0",