fix: handle corrupted unrendered template data gracefully

- Wrap UnrenderedTemplateControl.model_validate in _parse_stored_control_data
  with proper error handling (returns 422 CORRUPTED_DATA instead of 500)
- Wrap unrendered parse in list_controls_for_agent with try/except to skip
  corrupted rows instead of crashing the entire listing
- Remove redundant unused-parameter check in render_template_control_input
  (already caught by validate_template_structure called at the top)

Author: lan17

server/src/agent_control_server/endpoints/controls.py

@@ -109,7 +109,24 @@ def _parse_stored_control_data(
 ) -> ControlDefinition | UnrenderedTemplateControl:
     """Parse stored JSONB into the appropriate model type."""
     if _is_unrendered_template(data):
-        return UnrenderedTemplateControl.model_validate(data)
+        try:
+            return UnrenderedTemplateControl.model_validate(data)
+        except ValidationError:
+            raise APIValidationError(
+                error_code=ErrorCode.CORRUPTED_DATA,
+                detail=f"Control '{control_name}' has corrupted unrendered template data",
+                resource="Control",
+                resource_id=str(control_id),
+                hint=f"Update the control data using PUT /api/v1/controls/{control_id}/data.",
+                errors=[
+                    ValidationErrorItem(
+                        resource="Control",
+                        field="data",
+                        code="corrupted_data",
+                        message="Stored unrendered template data is invalid.",
+                    )
+                ],
+            )
 
     return parse_control_definition_or_api_error(
         data,

server/src/agent_control_server/services/control_templates.py

@@ -759,25 +759,9 @@ def render_template_control_input(
         template=template,
     )
 
-    unused_parameters = sorted(set(template.parameters) - referenced_parameters)
-    if unused_parameters:
-        raise APIValidationError(
-            error_code=ErrorCode.TEMPLATE_RENDER_ERROR,
-            detail="Template defines parameters that are never referenced",
-            resource="Control",
-            hint="Remove unused parameters or reference them in definition_template.",
-            errors=[
-                ValidationErrorItem(
-                    resource="Control",
-                    field=f"template.parameters.{parameter_name}",
-                    code="unused_template_parameter",
-                    message=f"Template parameter '{parameter_name}' is never referenced.",
-                    parameter=parameter_name,
-                    parameter_label=template.parameters[parameter_name].label,
-                )
-                for parameter_name in unused_parameters
-            ],
-        )
+    # Note: unused-parameter detection is handled by validate_template_structure
+    # (called above).  The referenced_parameters set is still tracked here for
+    # the reverse path map used in error remapping.
 
     try:
         rendered_control = ControlDefinition.model_validate(rendered_payload)

server/src/agent_control_server/services/controls.py

@@ -8,12 +8,15 @@
 from sqlalchemy import select, union
 from sqlalchemy.ext.asyncio import AsyncSession
 
+from ..logging_utils import get_logger
 from ..models import Control, agent_controls, agent_policies, policy_controls
 from .control_definitions import (
     parse_control_definition_or_api_error,
     parse_runtime_control_definition_or_api_error,
 )
 
+_logger = get_logger(__name__)
+
 
 @dataclass(frozen=True)
 class RuntimeControl:
@@ -89,7 +92,16 @@ async def list_controls_for_agent(
             and c.data.get("template") is not None
             and c.data.get("condition") is None
         ):
-            unrendered = UnrenderedTemplateControl.model_validate(c.data)
+            try:
+                unrendered = UnrenderedTemplateControl.model_validate(c.data)
+            except Exception:
+                _logger.warning(
+                    "Skipping control '%s' (id=%s): corrupted unrendered template data",
+                    c.name,
+                    c.id,
+                    exc_info=True,
+                )
+                continue
             api_controls.append(APIControl(id=c.id, name=c.name, control=unrendered))
             continue