{"abstract":"Viewport stabilization moves logical tree focus produces the wrong hierarchical widget state in a regression fixture.","category":"Tree accessibility","checks":8,"contract":"After branch expansion changes row heights/order, preserve the first visible surviving anchor and its pixel offset. If that row is removed, use the next surviving old row, then previous row. Clamp scroll to content extent, include fractional row offsets, and keep active-row identity independent from viewport anchoring.","evaluation_group":"s3-tree-viewport-anchor","failed_approach":"The partial repair `active=new[0] if new else None` still violates a boundary or preservation case.","family":"s3-tree_accessibility-viewport-anchor-09","id":"FA-39581","implementations":{"attempt":{"sha256":"e438892431698541ee8022e18238565873c70e921ea468cd026e1d7eb6d2c0d5","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(d):\n    old=d['old']; new=d['new']\n    index=old.index(d['anchor']) if d['anchor'] in old else 0\n    candidates=[d['anchor']]+old[index+1:]+list(reversed(old[:index]))\n    anchor=next((x for x in candidates if x in new),(new[0] if new else None))\n    position=sum(d['heights'][x] for x in new[:new.index(anchor)]) if anchor is not None else 0\n    inside=min(d['offset'],d['heights'][anchor]-1) if anchor==d['anchor'] else 0\n    requested=position+max(0,inside)\n    content=sum(d['heights'][x] for x in new)\n    scroll=max(0,min(requested,content-d['viewport']))\n    active=new[0] if new else None\n    return [anchor,scroll,content,active]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncases = {1: [('insert before anchor', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['r', 'x', 'a', 'b', 'c', 'z'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 16, 'c': 11, 'z': 12, 'x': 31, 'q': 5}, 'offset': 3.5, 'viewport': 20, 'active': 'a'}, ['b', 64.5, 100, 'a']), ('deleted anchor', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['r', 'a', 'c', 'z'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 16, 'c': 11, 'z': 12, 'x': 31, 'q': 5}, 'offset': 3.5, 'viewport': 20, 'active': 'a'}, ['c', 30, 53, 'a']), ('previous fallback', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['r', 'a'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 16, 'c': 11, 'z': 12, 'x': 31, 'q': 5}, 'offset': 3.5, 'viewport': 20, 'active': 'a'}, ['a', 10, 30, 'a']), ('new-only tree', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['q'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 16, 'c': 11, 'z': 12, 'x': 31, 'q': 5}, 'offset': 3.5, 'viewport': 20, 'active': 'a'}, ['q', 0, 5, 'a']), ('empty tree', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': [], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 16, 'c': 11, 'z': 12, 'x': 31, 'q': 5}, 'offset': 3.5, 'viewport': 20, 'active': 'a'}, [None, 0, 0, 'a']), ('bottom clamp', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['r', 'x', 'a', 'b', 'c', 'z'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 16, 'c': 11, 'z': 12, 'x': 31, 'q': 5}, 'offset': 3.5, 'viewport': 60, 'active': 'a'}, ['b', 40, 100, 'a']), ('oversized offset', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['r', 'x', 'a', 'b', 'c', 'z'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 16, 'c': 11, 'z': 12, 'x': 31, 'q': 5}, 'offset': 100, 'viewport': 20, 'active': 'a'}, ['b', 76, 100, 'a']), ('reordered', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['z', 'c', 'b', 'a', 'r'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 16, 'c': 11, 'z': 12, 'x': 31, 'q': 5}, 'offset': 3.5, 'viewport': 20, 'active': 'a'}, ['b', 26.5, 69, 'a'])], 2: [('insert before anchor', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['r', 'x', 'a', 'b', 'c', 'z'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 17, 'c': 11, 'z': 12, 'x': 32, 'q': 5}, 'offset': 3.5, 'viewport': 20, 'active': 'a'}, ['b', 65.5, 102, 'a']), ('deleted anchor', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['r', 'a', 'c', 'z'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 17, 'c': 11, 'z': 12, 'x': 32, 'q': 5}, 'offset': 3.5, 'viewport': 20, 'active': 'a'}, ['c', 30, 53, 'a']), ('previous fallback', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['r', 'a'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 17, 'c': 11, 'z': 12, 'x': 32, 'q': 5}, 'offset': 3.5, 'viewport': 20, 'active': 'a'}, ['a', 10, 30, 'a']), ('new-only tree', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['q'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 17, 'c': 11, 'z': 12, 'x': 32, 'q': 5}, 'offset': 3.5, 'viewport': 20, 'active': 'a'}, ['q', 0, 5, 'a']), ('empty tree', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': [], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 17, 'c': 11, 'z': 12, 'x': 32, 'q': 5}, 'offset': 3.5, 'viewport': 20, 'active': 'a'}, [None, 0, 0, 'a']), ('bottom clamp', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['r', 'x', 'a', 'b', 'c', 'z'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 17, 'c': 11, 'z': 12, 'x': 32, 'q': 5}, 'offset': 3.5, 'viewport': 60, 'active': 'a'}, ['b', 42, 102, 'a']), ('oversized offset', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['r', 'x', 'a', 'b', 'c', 'z'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 17, 'c': 11, 'z': 12, 'x': 32, 'q': 5}, 'offset': 100, 'viewport': 20, 'active': 'a'}, ['b', 78, 102, 'a']), ('reordered', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['z', 'c', 'b', 'a', 'r'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 17, 'c': 11, 'z': 12, 'x': 32, 'q': 5}, 'offset': 3.5, 'viewport': 20, 'active': 'a'}, ['b', 26.5, 70, 'a'])], 3: [('insert before anchor', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['r', 'x', 'a', 'b', 'c', 'z'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 18, 'c': 11, 'z': 12, 'x': 33, 'q': 5}, 'offset': 3.5, 'viewport': 20, 'active': 'a'}, ['b', 66.5, 104, 'a']), ('deleted anchor', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['r', 'a', 'c', 'z'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 18, 'c': 11, 'z': 12, 'x': 33, 'q': 5}, 'offset': 3.5, 'viewport': 20, 'active': 'a'}, ['c', 30, 53, 'a']), ('previous fallback', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['r', 'a'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 18, 'c': 11, 'z': 12, 'x': 33, 'q': 5}, 'offset': 3.5, 'viewport': 20, 'active': 'a'}, ['a', 10, 30, 'a']), ('new-only tree', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['q'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 18, 'c': 11, 'z': 12, 'x': 33, 'q': 5}, 'offset': 3.5, 'viewport': 20, 'active': 'a'}, ['q', 0, 5, 'a']), ('empty tree', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': [], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 18, 'c': 11, 'z': 12, 'x': 33, 'q': 5}, 'offset': 3.5, 'viewport': 20, 'active': 'a'}, [None, 0, 0, 'a']), ('bottom clamp', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['r', 'x', 'a', 'b', 'c', 'z'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 18, 'c': 11, 'z': 12, 'x': 33, 'q': 5}, 'offset': 3.5, 'viewport': 60, 'active': 'a'}, ['b', 44, 104, 'a']), ('oversized offset', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['r', 'x', 'a', 'b', 'c', 'z'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 18, 'c': 11, 'z': 12, 'x': 33, 'q': 5}, 'offset': 100, 'viewport': 20, 'active': 'a'}, ['b', 80, 104, 'a']), ('reordered', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['z', 'c', 'b', 'a', 'r'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 18, 'c': 11, 'z': 12, 'x': 33, 'q': 5}, 'offset': 3.5, 'viewport': 20, 'active': 'a'}, ['b', 26.5, 71, 'a'])], 4: [('insert before anchor', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['r', 'x', 'a', 'b', 'c', 'z'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 19, 'c': 11, 'z': 12, 'x': 34, 'q': 5}, 'offset': 3.5, 'viewport': 20, 'active': 'a'}, ['b', 67.5, 106, 'a']), ('deleted anchor', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['r', 'a', 'c', 'z'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 19, 'c': 11, 'z': 12, 'x': 34, 'q': 5}, 'offset': 3.5, 'viewport': 20, 'active': 'a'}, ['c', 30, 53, 'a']), ('previous fallback', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['r', 'a'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 19, 'c': 11, 'z': 12, 'x': 34, 'q': 5}, 'offset': 3.5, 'viewport': 20, 'active': 'a'}, ['a', 10, 30, 'a']), ('new-only tree', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['q'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 19, 'c': 11, 'z': 12, 'x': 34, 'q': 5}, 'offset': 3.5, 'viewport': 20, 'active': 'a'}, ['q', 0, 5, 'a']), ('empty tree', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': [], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 19, 'c': 11, 'z': 12, 'x': 34, 'q': 5}, 'offset': 3.5, 'viewport': 20, 'active': 'a'}, [None, 0, 0, 'a']), ('bottom clamp', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['r', 'x', 'a', 'b', 'c', 'z'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 19, 'c': 11, 'z': 12, 'x': 34, 'q': 5}, 'offset': 3.5, 'viewport': 60, 'active': 'a'}, ['b', 46, 106, 'a']), ('oversized offset', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['r', 'x', 'a', 'b', 'c', 'z'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 19, 'c': 11, 'z': 12, 'x': 34, 'q': 5}, 'offset': 100, 'viewport': 20, 'active': 'a'}, ['b', 82, 106, 'a']), ('reordered', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['z', 'c', 'b', 'a', 'r'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 19, 'c': 11, 'z': 12, 'x': 34, 'q': 5}, 'offset': 3.5, 'viewport': 20, 'active': 'a'}, ['b', 26.5, 72, 'a'])], 5: [('insert before anchor', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['r', 'x', 'a', 'b', 'c', 'z'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 20, 'c': 11, 'z': 12, 'x': 35, 'q': 5}, 'offset': 3.5, 'viewport': 20, 'active': 'a'}, ['b', 68.5, 108, 'a']), ('deleted anchor', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['r', 'a', 'c', 'z'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 20, 'c': 11, 'z': 12, 'x': 35, 'q': 5}, 'offset': 3.5, 'viewport': 20, 'active': 'a'}, ['c', 30, 53, 'a']), ('previous fallback', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['r', 'a'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 20, 'c': 11, 'z': 12, 'x': 35, 'q': 5}, 'offset': 3.5, 'viewport': 20, 'active': 'a'}, ['a', 10, 30, 'a']), ('new-only tree', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['q'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 20, 'c': 11, 'z': 12, 'x': 35, 'q': 5}, 'offset': 3.5, 'viewport': 20, 'active': 'a'}, ['q', 0, 5, 'a']), ('empty tree', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': [], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 20, 'c': 11, 'z': 12, 'x': 35, 'q': 5}, 'offset': 3.5, 'viewport': 20, 'active': 'a'}, [None, 0, 0, 'a']), ('bottom clamp', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['r', 'x', 'a', 'b', 'c', 'z'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 20, 'c': 11, 'z': 12, 'x': 35, 'q': 5}, 'offset': 3.5, 'viewport': 60, 'active': 'a'}, ['b', 48, 108, 'a']), ('oversized offset', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['r', 'x', 'a', 'b', 'c', 'z'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 20, 'c': 11, 'z': 12, 'x': 35, 'q': 5}, 'offset': 100, 'viewport': 20, 'active': 'a'}, ['b', 84, 108, 'a']), ('reordered', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['z', 'c', 'b', 'a', 'r'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 20, 'c': 11, 'z': 12, 'x': 35, 'q': 5}, 'offset': 3.5, 'viewport': 20, 'active': 'a'}, ['b', 26.5, 73, 'a'])]}\nfor label, data, expected in cases[N]:\n    check(label, solve(data), expected)\nprint(json.dumps({\"observations\": observations, \"passed\": all(x[\"passed\"] for x in observations)}, ensure_ascii=False))\nraise SystemExit(0 if all(x[\"passed\"] for x in observations) else 1)\n"},"broken":{"sha256":"46f66ebd4ef668c6a0701b6377390aebe9e1830977958a173d355d2d7eaeabdd","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(d):\n    old=d['old']; new=d['new']\n    index=old.index(d['anchor']) if d['anchor'] in old else 0\n    candidates=[d['anchor']]+old[index+1:]+list(reversed(old[:index]))\n    anchor=next((x for x in candidates if x in new),(new[0] if new else None))\n    position=sum(d['heights'][x] for x in new[:new.index(anchor)]) if anchor is not None else 0\n    inside=min(d['offset'],d['heights'][anchor]-1) if anchor==d['anchor'] else 0\n    requested=position+max(0,inside)\n    content=sum(d['heights'][x] for x in new)\n    scroll=max(0,min(requested,content-d['viewport']))\n    active=anchor\n    return [anchor,scroll,content,active]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncases = {1: [('insert before anchor', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['r', 'x', 'a', 'b', 'c', 'z'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 16, 'c': 11, 'z': 12, 'x': 31, 'q': 5}, 'offset': 3.5, 'viewport': 20, 'active': 'a'}, ['b', 64.5, 100, 'a']), ('deleted anchor', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['r', 'a', 'c', 'z'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 16, 'c': 11, 'z': 12, 'x': 31, 'q': 5}, 'offset': 3.5, 'viewport': 20, 'active': 'a'}, ['c', 30, 53, 'a']), ('previous fallback', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['r', 'a'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 16, 'c': 11, 'z': 12, 'x': 31, 'q': 5}, 'offset': 3.5, 'viewport': 20, 'active': 'a'}, ['a', 10, 30, 'a']), ('new-only tree', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['q'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 16, 'c': 11, 'z': 12, 'x': 31, 'q': 5}, 'offset': 3.5, 'viewport': 20, 'active': 'a'}, ['q', 0, 5, 'a']), ('empty tree', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': [], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 16, 'c': 11, 'z': 12, 'x': 31, 'q': 5}, 'offset': 3.5, 'viewport': 20, 'active': 'a'}, [None, 0, 0, 'a']), ('bottom clamp', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['r', 'x', 'a', 'b', 'c', 'z'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 16, 'c': 11, 'z': 12, 'x': 31, 'q': 5}, 'offset': 3.5, 'viewport': 60, 'active': 'a'}, ['b', 40, 100, 'a']), ('oversized offset', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['r', 'x', 'a', 'b', 'c', 'z'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 16, 'c': 11, 'z': 12, 'x': 31, 'q': 5}, 'offset': 100, 'viewport': 20, 'active': 'a'}, ['b', 76, 100, 'a']), ('reordered', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['z', 'c', 'b', 'a', 'r'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 16, 'c': 11, 'z': 12, 'x': 31, 'q': 5}, 'offset': 3.5, 'viewport': 20, 'active': 'a'}, ['b', 26.5, 69, 'a'])], 2: [('insert before anchor', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['r', 'x', 'a', 'b', 'c', 'z'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 17, 'c': 11, 'z': 12, 'x': 32, 'q': 5}, 'offset': 3.5, 'viewport': 20, 'active': 'a'}, ['b', 65.5, 102, 'a']), ('deleted anchor', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['r', 'a', 'c', 'z'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 17, 'c': 11, 'z': 12, 'x': 32, 'q': 5}, 'offset': 3.5, 'viewport': 20, 'active': 'a'}, ['c', 30, 53, 'a']), ('previous fallback', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['r', 'a'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 17, 'c': 11, 'z': 12, 'x': 32, 'q': 5}, 'offset': 3.5, 'viewport': 20, 'active': 'a'}, ['a', 10, 30, 'a']), ('new-only tree', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['q'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 17, 'c': 11, 'z': 12, 'x': 32, 'q': 5}, 'offset': 3.5, 'viewport': 20, 'active': 'a'}, ['q', 0, 5, 'a']), ('empty tree', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': [], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 17, 'c': 11, 'z': 12, 'x': 32, 'q': 5}, 'offset': 3.5, 'viewport': 20, 'active': 'a'}, [None, 0, 0, 'a']), ('bottom clamp', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['r', 'x', 'a', 'b', 'c', 'z'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 17, 'c': 11, 'z': 12, 'x': 32, 'q': 5}, 'offset': 3.5, 'viewport': 60, 'active': 'a'}, ['b', 42, 102, 'a']), ('oversized offset', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['r', 'x', 'a', 'b', 'c', 'z'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 17, 'c': 11, 'z': 12, 'x': 32, 'q': 5}, 'offset': 100, 'viewport': 20, 'active': 'a'}, ['b', 78, 102, 'a']), ('reordered', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['z', 'c', 'b', 'a', 'r'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 17, 'c': 11, 'z': 12, 'x': 32, 'q': 5}, 'offset': 3.5, 'viewport': 20, 'active': 'a'}, ['b', 26.5, 70, 'a'])], 3: [('insert before anchor', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['r', 'x', 'a', 'b', 'c', 'z'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 18, 'c': 11, 'z': 12, 'x': 33, 'q': 5}, 'offset': 3.5, 'viewport': 20, 'active': 'a'}, ['b', 66.5, 104, 'a']), ('deleted anchor', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['r', 'a', 'c', 'z'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 18, 'c': 11, 'z': 12, 'x': 33, 'q': 5}, 'offset': 3.5, 'viewport': 20, 'active': 'a'}, ['c', 30, 53, 'a']), ('previous fallback', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['r', 'a'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 18, 'c': 11, 'z': 12, 'x': 33, 'q': 5}, 'offset': 3.5, 'viewport': 20, 'active': 'a'}, ['a', 10, 30, 'a']), ('new-only tree', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['q'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 18, 'c': 11, 'z': 12, 'x': 33, 'q': 5}, 'offset': 3.5, 'viewport': 20, 'active': 'a'}, ['q', 0, 5, 'a']), ('empty tree', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': [], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 18, 'c': 11, 'z': 12, 'x': 33, 'q': 5}, 'offset': 3.5, 'viewport': 20, 'active': 'a'}, [None, 0, 0, 'a']), ('bottom clamp', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['r', 'x', 'a', 'b', 'c', 'z'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 18, 'c': 11, 'z': 12, 'x': 33, 'q': 5}, 'offset': 3.5, 'viewport': 60, 'active': 'a'}, ['b', 44, 104, 'a']), ('oversized offset', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['r', 'x', 'a', 'b', 'c', 'z'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 18, 'c': 11, 'z': 12, 'x': 33, 'q': 5}, 'offset': 100, 'viewport': 20, 'active': 'a'}, ['b', 80, 104, 'a']), ('reordered', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['z', 'c', 'b', 'a', 'r'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 18, 'c': 11, 'z': 12, 'x': 33, 'q': 5}, 'offset': 3.5, 'viewport': 20, 'active': 'a'}, ['b', 26.5, 71, 'a'])], 4: [('insert before anchor', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['r', 'x', 'a', 'b', 'c', 'z'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 19, 'c': 11, 'z': 12, 'x': 34, 'q': 5}, 'offset': 3.5, 'viewport': 20, 'active': 'a'}, ['b', 67.5, 106, 'a']), ('deleted anchor', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['r', 'a', 'c', 'z'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 19, 'c': 11, 'z': 12, 'x': 34, 'q': 5}, 'offset': 3.5, 'viewport': 20, 'active': 'a'}, ['c', 30, 53, 'a']), ('previous fallback', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['r', 'a'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 19, 'c': 11, 'z': 12, 'x': 34, 'q': 5}, 'offset': 3.5, 'viewport': 20, 'active': 'a'}, ['a', 10, 30, 'a']), ('new-only tree', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['q'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 19, 'c': 11, 'z': 12, 'x': 34, 'q': 5}, 'offset': 3.5, 'viewport': 20, 'active': 'a'}, ['q', 0, 5, 'a']), ('empty tree', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': [], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 19, 'c': 11, 'z': 12, 'x': 34, 'q': 5}, 'offset': 3.5, 'viewport': 20, 'active': 'a'}, [None, 0, 0, 'a']), ('bottom clamp', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['r', 'x', 'a', 'b', 'c', 'z'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 19, 'c': 11, 'z': 12, 'x': 34, 'q': 5}, 'offset': 3.5, 'viewport': 60, 'active': 'a'}, ['b', 46, 106, 'a']), ('oversized offset', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['r', 'x', 'a', 'b', 'c', 'z'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 19, 'c': 11, 'z': 12, 'x': 34, 'q': 5}, 'offset': 100, 'viewport': 20, 'active': 'a'}, ['b', 82, 106, 'a']), ('reordered', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['z', 'c', 'b', 'a', 'r'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 19, 'c': 11, 'z': 12, 'x': 34, 'q': 5}, 'offset': 3.5, 'viewport': 20, 'active': 'a'}, ['b', 26.5, 72, 'a'])], 5: [('insert before anchor', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['r', 'x', 'a', 'b', 'c', 'z'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 20, 'c': 11, 'z': 12, 'x': 35, 'q': 5}, 'offset': 3.5, 'viewport': 20, 'active': 'a'}, ['b', 68.5, 108, 'a']), ('deleted anchor', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['r', 'a', 'c', 'z'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 20, 'c': 11, 'z': 12, 'x': 35, 'q': 5}, 'offset': 3.5, 'viewport': 20, 'active': 'a'}, ['c', 30, 53, 'a']), ('previous fallback', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['r', 'a'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 20, 'c': 11, 'z': 12, 'x': 35, 'q': 5}, 'offset': 3.5, 'viewport': 20, 'active': 'a'}, ['a', 10, 30, 'a']), ('new-only tree', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['q'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 20, 'c': 11, 'z': 12, 'x': 35, 'q': 5}, 'offset': 3.5, 'viewport': 20, 'active': 'a'}, ['q', 0, 5, 'a']), ('empty tree', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': [], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 20, 'c': 11, 'z': 12, 'x': 35, 'q': 5}, 'offset': 3.5, 'viewport': 20, 'active': 'a'}, [None, 0, 0, 'a']), ('bottom clamp', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['r', 'x', 'a', 'b', 'c', 'z'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 20, 'c': 11, 'z': 12, 'x': 35, 'q': 5}, 'offset': 3.5, 'viewport': 60, 'active': 'a'}, ['b', 48, 108, 'a']), ('oversized offset', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['r', 'x', 'a', 'b', 'c', 'z'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 20, 'c': 11, 'z': 12, 'x': 35, 'q': 5}, 'offset': 100, 'viewport': 20, 'active': 'a'}, ['b', 84, 108, 'a']), ('reordered', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['z', 'c', 'b', 'a', 'r'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 20, 'c': 11, 'z': 12, 'x': 35, 'q': 5}, 'offset': 3.5, 'viewport': 20, 'active': 'a'}, ['b', 26.5, 73, 'a'])]}\nfor label, data, expected in cases[N]:\n    check(label, solve(data), expected)\nprint(json.dumps({\"observations\": observations, \"passed\": all(x[\"passed\"] for x in observations)}, ensure_ascii=False))\nraise SystemExit(0 if all(x[\"passed\"] for x in observations) else 1)\n"},"fixed":{"sha256":"31833c367fd964568637daa88f5075860dde80070967f9d8351262ab7d437a54","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(d):\n    old=d['old']; new=d['new']\n    index=old.index(d['anchor']) if d['anchor'] in old else 0\n    candidates=[d['anchor']]+old[index+1:]+list(reversed(old[:index]))\n    anchor=next((x for x in candidates if x in new),(new[0] if new else None))\n    position=sum(d['heights'][x] for x in new[:new.index(anchor)]) if anchor is not None else 0\n    inside=min(d['offset'],d['heights'][anchor]-1) if anchor==d['anchor'] else 0\n    requested=position+max(0,inside)\n    content=sum(d['heights'][x] for x in new)\n    scroll=max(0,min(requested,content-d['viewport']))\n    active=d['active']\n    return [anchor,scroll,content,active]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncases = {1: [('insert before anchor', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['r', 'x', 'a', 'b', 'c', 'z'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 16, 'c': 11, 'z': 12, 'x': 31, 'q': 5}, 'offset': 3.5, 'viewport': 20, 'active': 'a'}, ['b', 64.5, 100, 'a']), ('deleted anchor', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['r', 'a', 'c', 'z'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 16, 'c': 11, 'z': 12, 'x': 31, 'q': 5}, 'offset': 3.5, 'viewport': 20, 'active': 'a'}, ['c', 30, 53, 'a']), ('previous fallback', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['r', 'a'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 16, 'c': 11, 'z': 12, 'x': 31, 'q': 5}, 'offset': 3.5, 'viewport': 20, 'active': 'a'}, ['a', 10, 30, 'a']), ('new-only tree', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['q'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 16, 'c': 11, 'z': 12, 'x': 31, 'q': 5}, 'offset': 3.5, 'viewport': 20, 'active': 'a'}, ['q', 0, 5, 'a']), ('empty tree', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': [], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 16, 'c': 11, 'z': 12, 'x': 31, 'q': 5}, 'offset': 3.5, 'viewport': 20, 'active': 'a'}, [None, 0, 0, 'a']), ('bottom clamp', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['r', 'x', 'a', 'b', 'c', 'z'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 16, 'c': 11, 'z': 12, 'x': 31, 'q': 5}, 'offset': 3.5, 'viewport': 60, 'active': 'a'}, ['b', 40, 100, 'a']), ('oversized offset', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['r', 'x', 'a', 'b', 'c', 'z'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 16, 'c': 11, 'z': 12, 'x': 31, 'q': 5}, 'offset': 100, 'viewport': 20, 'active': 'a'}, ['b', 76, 100, 'a']), ('reordered', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['z', 'c', 'b', 'a', 'r'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 16, 'c': 11, 'z': 12, 'x': 31, 'q': 5}, 'offset': 3.5, 'viewport': 20, 'active': 'a'}, ['b', 26.5, 69, 'a'])], 2: [('insert before anchor', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['r', 'x', 'a', 'b', 'c', 'z'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 17, 'c': 11, 'z': 12, 'x': 32, 'q': 5}, 'offset': 3.5, 'viewport': 20, 'active': 'a'}, ['b', 65.5, 102, 'a']), ('deleted anchor', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['r', 'a', 'c', 'z'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 17, 'c': 11, 'z': 12, 'x': 32, 'q': 5}, 'offset': 3.5, 'viewport': 20, 'active': 'a'}, ['c', 30, 53, 'a']), ('previous fallback', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['r', 'a'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 17, 'c': 11, 'z': 12, 'x': 32, 'q': 5}, 'offset': 3.5, 'viewport': 20, 'active': 'a'}, ['a', 10, 30, 'a']), ('new-only tree', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['q'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 17, 'c': 11, 'z': 12, 'x': 32, 'q': 5}, 'offset': 3.5, 'viewport': 20, 'active': 'a'}, ['q', 0, 5, 'a']), ('empty tree', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': [], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 17, 'c': 11, 'z': 12, 'x': 32, 'q': 5}, 'offset': 3.5, 'viewport': 20, 'active': 'a'}, [None, 0, 0, 'a']), ('bottom clamp', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['r', 'x', 'a', 'b', 'c', 'z'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 17, 'c': 11, 'z': 12, 'x': 32, 'q': 5}, 'offset': 3.5, 'viewport': 60, 'active': 'a'}, ['b', 42, 102, 'a']), ('oversized offset', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['r', 'x', 'a', 'b', 'c', 'z'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 17, 'c': 11, 'z': 12, 'x': 32, 'q': 5}, 'offset': 100, 'viewport': 20, 'active': 'a'}, ['b', 78, 102, 'a']), ('reordered', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['z', 'c', 'b', 'a', 'r'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 17, 'c': 11, 'z': 12, 'x': 32, 'q': 5}, 'offset': 3.5, 'viewport': 20, 'active': 'a'}, ['b', 26.5, 70, 'a'])], 3: [('insert before anchor', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['r', 'x', 'a', 'b', 'c', 'z'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 18, 'c': 11, 'z': 12, 'x': 33, 'q': 5}, 'offset': 3.5, 'viewport': 20, 'active': 'a'}, ['b', 66.5, 104, 'a']), ('deleted anchor', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['r', 'a', 'c', 'z'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 18, 'c': 11, 'z': 12, 'x': 33, 'q': 5}, 'offset': 3.5, 'viewport': 20, 'active': 'a'}, ['c', 30, 53, 'a']), ('previous fallback', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['r', 'a'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 18, 'c': 11, 'z': 12, 'x': 33, 'q': 5}, 'offset': 3.5, 'viewport': 20, 'active': 'a'}, ['a', 10, 30, 'a']), ('new-only tree', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['q'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 18, 'c': 11, 'z': 12, 'x': 33, 'q': 5}, 'offset': 3.5, 'viewport': 20, 'active': 'a'}, ['q', 0, 5, 'a']), ('empty tree', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': [], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 18, 'c': 11, 'z': 12, 'x': 33, 'q': 5}, 'offset': 3.5, 'viewport': 20, 'active': 'a'}, [None, 0, 0, 'a']), ('bottom clamp', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['r', 'x', 'a', 'b', 'c', 'z'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 18, 'c': 11, 'z': 12, 'x': 33, 'q': 5}, 'offset': 3.5, 'viewport': 60, 'active': 'a'}, ['b', 44, 104, 'a']), ('oversized offset', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['r', 'x', 'a', 'b', 'c', 'z'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 18, 'c': 11, 'z': 12, 'x': 33, 'q': 5}, 'offset': 100, 'viewport': 20, 'active': 'a'}, ['b', 80, 104, 'a']), ('reordered', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['z', 'c', 'b', 'a', 'r'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 18, 'c': 11, 'z': 12, 'x': 33, 'q': 5}, 'offset': 3.5, 'viewport': 20, 'active': 'a'}, ['b', 26.5, 71, 'a'])], 4: [('insert before anchor', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['r', 'x', 'a', 'b', 'c', 'z'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 19, 'c': 11, 'z': 12, 'x': 34, 'q': 5}, 'offset': 3.5, 'viewport': 20, 'active': 'a'}, ['b', 67.5, 106, 'a']), ('deleted anchor', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['r', 'a', 'c', 'z'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 19, 'c': 11, 'z': 12, 'x': 34, 'q': 5}, 'offset': 3.5, 'viewport': 20, 'active': 'a'}, ['c', 30, 53, 'a']), ('previous fallback', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['r', 'a'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 19, 'c': 11, 'z': 12, 'x': 34, 'q': 5}, 'offset': 3.5, 'viewport': 20, 'active': 'a'}, ['a', 10, 30, 'a']), ('new-only tree', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['q'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 19, 'c': 11, 'z': 12, 'x': 34, 'q': 5}, 'offset': 3.5, 'viewport': 20, 'active': 'a'}, ['q', 0, 5, 'a']), ('empty tree', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': [], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 19, 'c': 11, 'z': 12, 'x': 34, 'q': 5}, 'offset': 3.5, 'viewport': 20, 'active': 'a'}, [None, 0, 0, 'a']), ('bottom clamp', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['r', 'x', 'a', 'b', 'c', 'z'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 19, 'c': 11, 'z': 12, 'x': 34, 'q': 5}, 'offset': 3.5, 'viewport': 60, 'active': 'a'}, ['b', 46, 106, 'a']), ('oversized offset', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['r', 'x', 'a', 'b', 'c', 'z'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 19, 'c': 11, 'z': 12, 'x': 34, 'q': 5}, 'offset': 100, 'viewport': 20, 'active': 'a'}, ['b', 82, 106, 'a']), ('reordered', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['z', 'c', 'b', 'a', 'r'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 19, 'c': 11, 'z': 12, 'x': 34, 'q': 5}, 'offset': 3.5, 'viewport': 20, 'active': 'a'}, ['b', 26.5, 72, 'a'])], 5: [('insert before anchor', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['r', 'x', 'a', 'b', 'c', 'z'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 20, 'c': 11, 'z': 12, 'x': 35, 'q': 5}, 'offset': 3.5, 'viewport': 20, 'active': 'a'}, ['b', 68.5, 108, 'a']), ('deleted anchor', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['r', 'a', 'c', 'z'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 20, 'c': 11, 'z': 12, 'x': 35, 'q': 5}, 'offset': 3.5, 'viewport': 20, 'active': 'a'}, ['c', 30, 53, 'a']), ('previous fallback', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['r', 'a'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 20, 'c': 11, 'z': 12, 'x': 35, 'q': 5}, 'offset': 3.5, 'viewport': 20, 'active': 'a'}, ['a', 10, 30, 'a']), ('new-only tree', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['q'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 20, 'c': 11, 'z': 12, 'x': 35, 'q': 5}, 'offset': 3.5, 'viewport': 20, 'active': 'a'}, ['q', 0, 5, 'a']), ('empty tree', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': [], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 20, 'c': 11, 'z': 12, 'x': 35, 'q': 5}, 'offset': 3.5, 'viewport': 20, 'active': 'a'}, [None, 0, 0, 'a']), ('bottom clamp', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['r', 'x', 'a', 'b', 'c', 'z'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 20, 'c': 11, 'z': 12, 'x': 35, 'q': 5}, 'offset': 3.5, 'viewport': 60, 'active': 'a'}, ['b', 48, 108, 'a']), ('oversized offset', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['r', 'x', 'a', 'b', 'c', 'z'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 20, 'c': 11, 'z': 12, 'x': 35, 'q': 5}, 'offset': 100, 'viewport': 20, 'active': 'a'}, ['b', 84, 108, 'a']), ('reordered', {'old': ['r', 'a', 'b', 'c', 'z'], 'new': ['z', 'c', 'b', 'a', 'r'], 'anchor': 'b', 'heights': {'r': 10, 'a': 20, 'b': 20, 'c': 11, 'z': 12, 'x': 35, 'q': 5}, 'offset': 3.5, 'viewport': 20, 'active': 'a'}, ['b', 26.5, 73, 'a'])]}\nfor label, data, expected in cases[N]:\n    check(label, solve(data), expected)\nprint(json.dumps({\"observations\": observations, \"passed\": all(x[\"passed\"] for x in observations)}, ensure_ascii=False))\nraise SystemExit(0 if all(x[\"passed\"] for x in observations) else 1)\n"}},"limitations":"Synthetic deterministic hierarchical-widget data contract; not an implementation of a browser accessibility tree. This reproducer isolates one failure mechanism. Results cover the supplied fixtures. Variants within a family share a test contract and should remain grouped when constructing evaluation splits. Related mechanisms with a shared evaluation_group must also remain together; these controlled models are not independent production incidents.","method":"Deterministic executable model with adversarial boundary fixtures.","provenance":{"created_by":"Failure Map","dependencies":"Python standard library","family":"s3-tree_accessibility-viewport-anchor-09","generated_at":"2026-09-29T14:43:22.593993+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"Offline executable model of a hierarchical accessibility interaction; inputs are bounded and valid as stipulated. No browser, assistive technology, or normative ARIA conformance is claimed.","repair":"Restore `active=d['active']` at this fault site while retaining the other tree state decisions.","root_cause":"The viewport-anchor contract is violated at `active=d['active']` by replacing it with `active=anchor`.","sha256":"6e8adbdbdca54a2bfeaac64a0944023d0e0cfb2818e6ccbd1d2425cf32005eef","title":"Expanded tree viewport anchor stabilization: Viewport stabilization moves logical tree focus · case 01","variant":1,"variant_policy":"Five numbered records share a model and may reuse boundary fixtures.","verification":{"attempt":{"elapsed_ms":61.331,"exit_code":1,"observations":[{"actual":["b",64.5,100,"r"],"check":"insert before anchor","expected":["b",64.5,100,"a"],"passed":false},{"actual":["c",30,53,"r"],"check":"deleted anchor","expected":["c",30,53,"a"],"passed":false},{"actual":["a",10,30,"r"],"check":"previous fallback","expected":["a",10,30,"a"],"passed":false},{"actual":["q",0,5,"q"],"check":"new-only tree","expected":["q",0,5,"a"],"passed":false},{"actual":[null,0,0,null],"check":"empty tree","expected":[null,0,0,"a"],"passed":false},{"actual":["b",40,100,"r"],"check":"bottom clamp","expected":["b",40,100,"a"],"passed":false},{"actual":["b",76,100,"r"],"check":"oversized offset","expected":["b",76,100,"a"],"passed":false},{"actual":["b",26.5,69,"z"],"check":"reordered","expected":["b",26.5,69,"a"],"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"insert before anchor\", \"actual\": [\"b\", 64.5, 100, \"r\"], \"expected\": [\"b\", 64.5, 100, \"a\"], \"passed\": false}, {\"check\": \"deleted anchor\", \"actual\": [\"c\", 30, 53, \"r\"], \"expected\": [\"c\", 30, 53, \"a\"], \"passed\": false}, {\"check\": \"previous fallback\", \"actual\": [\"a\", 10, 30, \"r\"], \"expected\": [\"a\", 10, 30, \"a\"], \"passed\": false}, {\"check\": \"new-only tree\", \"actual\": [\"q\", 0, 5, \"q\"], \"expected\": [\"q\", 0, 5, \"a\"], \"passed\": false}, {\"check\": \"empty tree\", \"actual\": [null, 0, 0, null], \"expected\": [null, 0, 0, \"a\"], \"passed\": false}, {\"check\": \"bottom clamp\", \"actual\": [\"b\", 40, 100, \"r\"], \"expected\": [\"b\", 40, 100, \"a\"], \"passed\": false}, {\"check\": \"oversized offset\", \"actual\": [\"b\", 76, 100, \"r\"], \"expected\": [\"b\", 76, 100, \"a\"], \"passed\": false}, {\"check\": \"reordered\", \"actual\": [\"b\", 26.5, 69, \"z\"], \"expected\": [\"b\", 26.5, 69, \"a\"], \"passed\": false}], \"passed\": false}\n"},"broken":{"elapsed_ms":51.21,"exit_code":1,"observations":[{"actual":["b",64.5,100,"b"],"check":"insert before anchor","expected":["b",64.5,100,"a"],"passed":false},{"actual":["c",30,53,"c"],"check":"deleted anchor","expected":["c",30,53,"a"],"passed":false},{"actual":["a",10,30,"a"],"check":"previous fallback","expected":["a",10,30,"a"],"passed":true},{"actual":["q",0,5,"q"],"check":"new-only tree","expected":["q",0,5,"a"],"passed":false},{"actual":[null,0,0,null],"check":"empty tree","expected":[null,0,0,"a"],"passed":false},{"actual":["b",40,100,"b"],"check":"bottom clamp","expected":["b",40,100,"a"],"passed":false},{"actual":["b",76,100,"b"],"check":"oversized offset","expected":["b",76,100,"a"],"passed":false},{"actual":["b",26.5,69,"b"],"check":"reordered","expected":["b",26.5,69,"a"],"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"insert before anchor\", \"actual\": [\"b\", 64.5, 100, \"b\"], \"expected\": [\"b\", 64.5, 100, \"a\"], \"passed\": false}, {\"check\": \"deleted anchor\", \"actual\": [\"c\", 30, 53, \"c\"], \"expected\": [\"c\", 30, 53, \"a\"], \"passed\": false}, {\"check\": \"previous fallback\", \"actual\": [\"a\", 10, 30, \"a\"], \"expected\": [\"a\", 10, 30, \"a\"], \"passed\": true}, {\"check\": \"new-only tree\", \"actual\": [\"q\", 0, 5, \"q\"], \"expected\": [\"q\", 0, 5, \"a\"], \"passed\": false}, {\"check\": \"empty tree\", \"actual\": [null, 0, 0, null], \"expected\": [null, 0, 0, \"a\"], \"passed\": false}, {\"check\": \"bottom clamp\", \"actual\": [\"b\", 40, 100, \"b\"], \"expected\": [\"b\", 40, 100, \"a\"], \"passed\": false}, {\"check\": \"oversized offset\", \"actual\": [\"b\", 76, 100, \"b\"], \"expected\": [\"b\", 76, 100, \"a\"], \"passed\": false}, {\"check\": \"reordered\", \"actual\": [\"b\", 26.5, 69, \"b\"], \"expected\": [\"b\", 26.5, 69, \"a\"], \"passed\": false}], \"passed\": false}\n"},"fixed":{"elapsed_ms":44.693,"exit_code":0,"observations":[{"actual":["b",64.5,100,"a"],"check":"insert before anchor","expected":["b",64.5,100,"a"],"passed":true},{"actual":["c",30,53,"a"],"check":"deleted anchor","expected":["c",30,53,"a"],"passed":true},{"actual":["a",10,30,"a"],"check":"previous fallback","expected":["a",10,30,"a"],"passed":true},{"actual":["q",0,5,"a"],"check":"new-only tree","expected":["q",0,5,"a"],"passed":true},{"actual":[null,0,0,"a"],"check":"empty tree","expected":[null,0,0,"a"],"passed":true},{"actual":["b",40,100,"a"],"check":"bottom clamp","expected":["b",40,100,"a"],"passed":true},{"actual":["b",76,100,"a"],"check":"oversized offset","expected":["b",76,100,"a"],"passed":true},{"actual":["b",26.5,69,"a"],"check":"reordered","expected":["b",26.5,69,"a"],"passed":true}],"passed":true,"stderr":"","stdout":"{\"observations\": [{\"check\": \"insert before anchor\", \"actual\": [\"b\", 64.5, 100, \"a\"], \"expected\": [\"b\", 64.5, 100, \"a\"], \"passed\": true}, {\"check\": \"deleted anchor\", \"actual\": [\"c\", 30, 53, \"a\"], \"expected\": [\"c\", 30, 53, \"a\"], \"passed\": true}, {\"check\": \"previous fallback\", \"actual\": [\"a\", 10, 30, \"a\"], \"expected\": [\"a\", 10, 30, \"a\"], \"passed\": true}, {\"check\": \"new-only tree\", \"actual\": [\"q\", 0, 5, \"a\"], \"expected\": [\"q\", 0, 5, \"a\"], \"passed\": true}, {\"check\": \"empty tree\", \"actual\": [null, 0, 0, \"a\"], \"expected\": [null, 0, 0, \"a\"], \"passed\": true}, {\"check\": \"bottom clamp\", \"actual\": [\"b\", 40, 100, \"a\"], \"expected\": [\"b\", 40, 100, \"a\"], \"passed\": true}, {\"check\": \"oversized offset\", \"actual\": [\"b\", 76, 100, \"a\"], \"expected\": [\"b\", 76, 100, \"a\"], \"passed\": true}, {\"check\": \"reordered\", \"actual\": [\"b\", 26.5, 69, \"a\"], \"expected\": [\"b\", 26.5, 69, \"a\"], \"passed\": true}], \"passed\": true}\n"}},"verified":true,"visibility":"public"}