In #273 the DisclosureTriangleRole model was adjusted and constraints/attributes were added. If I'm understanding this correctly, that means that a <summary> tag now either needs a open or aria-expanded attribute, but both these AFAIK should be on the parent <details> tag instead. So if I'm understanding this correctly, the DisclosureTriangleRole model should instead be reduced to

const DisclosureTriangleRole: AXObjectModelDefinition = {
  relatedConcepts: [
    {
      module: 'HTML',
      concept: {
        constraints: [
          'scoped to a details element',
        ],
        name: 'summary',
      },
    },
  ],
  type: 'widget',
};

It could also very well be that I'm understanding the semantic meaning of attributes incorrectly, in which case could you briefly explain what it means?