{"abstract":"Collapsed breadcrumbs retain old ancestors instead of recent ones.","category":"Client navigation","checks":7,"contract":"Append current after ancestors; optionally hide a distinct root; collapse long paths preserving root and recent tail within budget; only ancestors are links. Budget is at least two.","contract_signature":"ancestors, current, max_items, include_root","evaluation_group":"xi-breadcrumb","failed_approach":"Keeping an extra ancestor exceeds the item budget.","family":"xi-breadcrumb-tail","id":"FA-8646","implementations":{"attempt":{"sha256":"5bf25257982b4e55e19aae5404a51275fbee211885c5c7eb4692bdd6ff49856e","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(ancestors, current, max_items, include_root):\n    chain = list(ancestors) + [current]\n    if not include_root and len(chain) > 1: chain = chain[1:]\n    if len(chain) > max_items:\n        chain = [chain[0], '…'] + chain[-(max_items-1):] if max_items > 2 else chain[-max_items:]\n    return [(x, i != len(chain)-1) for i, x in enumerate(chain)]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('normal', solve(['root','parent'], 'current', 5, True), [('root', True), ('parent', True), ('current', False)])\ncheck('only current', solve([], 'current', 5, False), [('current', False)])\ncheck('hide root', solve(['root','parent'], 'current', 5, False), [('parent', True), ('current', False)])\ncheck('collapsed', solve(['root','a','b','c'], 'current', 4, True), [('root', True), ('…', True), ('c', True), ('current', False)])\ncheck('small budget', solve(['root','a','b'], 'current', 2, True), [('b', True), ('current', False)])\ncheck('parameterized ancestor depth', solve(list(range(N)),N,N+2,True), [(i,i!=N) for i in range(N+1)])\nfor repetition in range(N):\n    check('repeat small budget', solve(['root','a','b'], 'current', 2, True), [('b', True), ('current', False)])\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":"b94f2b37ab4f4f3c9bd76023018ebd4c3a11ddee707204deb0b27036471381d1","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(ancestors, current, max_items, include_root):\n    chain = list(ancestors) + [current]\n    if not include_root and len(chain) > 1: chain = chain[1:]\n    if len(chain) > max_items:\n        chain = [chain[0], '…'] + chain[:max_items-2] if max_items > 2 else chain[-max_items:]\n    return [(x, i != len(chain)-1) for i, x in enumerate(chain)]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('normal', solve(['root','parent'], 'current', 5, True), [('root', True), ('parent', True), ('current', False)])\ncheck('only current', solve([], 'current', 5, False), [('current', False)])\ncheck('hide root', solve(['root','parent'], 'current', 5, False), [('parent', True), ('current', False)])\ncheck('collapsed', solve(['root','a','b','c'], 'current', 4, True), [('root', True), ('…', True), ('c', True), ('current', False)])\ncheck('small budget', solve(['root','a','b'], 'current', 2, True), [('b', True), ('current', False)])\ncheck('parameterized ancestor depth', solve(list(range(N)),N,N+2,True), [(i,i!=N) for i in range(N+1)])\nfor repetition in range(N):\n    check('repeat small budget', solve(['root','a','b'], 'current', 2, True), [('b', True), ('current', False)])\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":" 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":"xi-breadcrumb-tail","generated_at":"2026-09-29T14:38:23.239034+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"A deterministic model of breadcrumb ancestor rendering; this isolates one interface invariant without requiring a browser.","root_cause":"The tail operation uses `chain[:max_items-2]` where the contract requires `chain[-(max_items-2):]`.","sha256":"db99634276837f6c9600efc532737bd4722189b53e34e39e4c9365f64dc66113","title":"Breadcrumb ancestor rendering: Collapsed breadcrumbs retain old ancestors instead of recent ones · case 01","variant":1,"variant_policy":"Five numbered records share a model and may reuse boundary fixtures.","verified":true,"visibility":"public","verification":{"attempt":{"elapsed_ms":36.126,"exit_code":1,"observations":[{"actual":[["root",true],["parent",true],["current",false]],"check":"normal","expected":[["root",true],["parent",true],["current",false]],"passed":true},{"actual":[["current",false]],"check":"only current","expected":[["current",false]],"passed":true},{"actual":[["parent",true],["current",false]],"check":"hide root","expected":[["parent",true],["current",false]],"passed":true},{"actual":[["root",true],["…",true],["b",true],["c",true],["current",false]],"check":"collapsed","expected":[["root",true],["…",true],["c",true],["current",false]],"passed":false},{"actual":[["b",true],["current",false]],"check":"small budget","expected":[["b",true],["current",false]],"passed":true},{"actual":[[0,true],[1,false]],"check":"parameterized ancestor depth","expected":[[0,true],[1,false]],"passed":true},{"actual":[["b",true],["current",false]],"check":"repeat small budget","expected":[["b",true],["current",false]],"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"normal\", \"actual\": [[\"root\", true], [\"parent\", true], [\"current\", false]], \"expected\": [[\"root\", true], [\"parent\", true], [\"current\", false]], \"passed\": true}, {\"check\": \"only current\", \"actual\": [[\"current\", false]], \"expected\": [[\"current\", false]], \"passed\": true}, {\"check\": \"hide root\", \"actual\": [[\"parent\", true], [\"current\", false]], \"expected\": [[\"parent\", true], [\"current\", false]], \"passed\": true}, {\"check\": \"collapsed\", \"actual\": [[\"root\", true], [\"…\", true], [\"b\", true], [\"c\", true], [\"current\", false]], \"expected\": [[\"root\", true], [\"…\", true], [\"c\", true], [\"current\", false]], \"passed\": false}, {\"check\": \"small budget\", \"actual\": [[\"b\", true], [\"current\", false]], \"expected\": [[\"b\", true], [\"current\", false]], \"passed\": true}, {\"check\": \"parameterized ancestor depth\", \"actual\": [[0, true], [1, false]], \"expected\": [[0, true], [1, false]], \"passed\": true}, {\"check\": \"repeat small budget\", \"actual\": [[\"b\", true], [\"current\", false]], \"expected\": [[\"b\", true], [\"current\", false]], \"passed\": true}], \"passed\": false}\n"},"broken":{"elapsed_ms":37.061,"exit_code":1,"observations":[{"actual":[["root",true],["parent",true],["current",false]],"check":"normal","expected":[["root",true],["parent",true],["current",false]],"passed":true},{"actual":[["current",false]],"check":"only current","expected":[["current",false]],"passed":true},{"actual":[["parent",true],["current",false]],"check":"hide root","expected":[["parent",true],["current",false]],"passed":true},{"actual":[["root",true],["…",true],["root",true],["a",false]],"check":"collapsed","expected":[["root",true],["…",true],["c",true],["current",false]],"passed":false},{"actual":[["b",true],["current",false]],"check":"small budget","expected":[["b",true],["current",false]],"passed":true},{"actual":[[0,true],[1,false]],"check":"parameterized ancestor depth","expected":[[0,true],[1,false]],"passed":true},{"actual":[["b",true],["current",false]],"check":"repeat small budget","expected":[["b",true],["current",false]],"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"normal\", \"actual\": [[\"root\", true], [\"parent\", true], [\"current\", false]], \"expected\": [[\"root\", true], [\"parent\", true], [\"current\", false]], \"passed\": true}, {\"check\": \"only current\", \"actual\": [[\"current\", false]], \"expected\": [[\"current\", false]], \"passed\": true}, {\"check\": \"hide root\", \"actual\": [[\"parent\", true], [\"current\", false]], \"expected\": [[\"parent\", true], [\"current\", false]], \"passed\": true}, {\"check\": \"collapsed\", \"actual\": [[\"root\", true], [\"…\", true], [\"root\", true], [\"a\", false]], \"expected\": [[\"root\", true], [\"…\", true], [\"c\", true], [\"current\", false]], \"passed\": false}, {\"check\": \"small budget\", \"actual\": [[\"b\", true], [\"current\", false]], \"expected\": [[\"b\", true], [\"current\", false]], \"passed\": true}, {\"check\": \"parameterized ancestor depth\", \"actual\": [[0, true], [1, false]], \"expected\": [[0, true], [1, false]], \"passed\": true}, {\"check\": \"repeat small budget\", \"actual\": [[\"b\", true], [\"current\", false]], \"expected\": [[\"b\", true], [\"current\", false]], \"passed\": true}], \"passed\": false}\n"}},"member_only":{"stages":["fixed"],"fields":["implementations.fixed","verification.fixed","harness","repair"],"note":"The verified repair, its recorded checks, the repair description, and the scoring harness are available to members."}}