{"abstract":"A boundary input predicts the first token of the next segment.","category":"Autoregressive target shifting","checks":6,"contract":"Given tokens and [start,end] segments, return adjacent pairs entirely within each segment; malformed empty segments contribute none.","contract_signature":"tokens, segments","evaluation_group":"w3-ars-pair_boundaries","failed_approach":"Dropping every pair touching a boundary also discards valid within-segment predictions.","family":"w3-autoregressive-target-shifting-pair-target-boundary","id":"FA-98321","implementations":{"attempt":{"sha256":"15ade1bef415efc9d5f0e7b9281463e7c64c273e60097e5f4127214ef43babfc","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(tokens, segments):\n    return [[tokens[i],tokens[i+1]] for a,b in segments for i in range(max(0,a+1),min(b-1,len(tokens)-1))]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('two segments',solve([0,1,2,3,4],[[0,2],[2,5]]),[[0,1],[2,3],[3,4]])\ncheck('single segment',solve([1,2,3],[[0,3]]),[[1,2],[2,3]])\ncheck('singleton segment',solve([1,2],[[0,1],[1,2]]),[])\ncheck('empty segments',solve([1],[]),[])\ncheck('clipped end',solve([1,2],[[0,8]]),[[1,2]])\ncheck('offset segment',solve([0,1,2,3],[[2,4]]),[[2,3]])\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":"904a74569f53c16b5b68e3c25b727a5e176bb05542cf1350e5ec51596444c0ee","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(tokens, segments):\n    return [[tokens[i],tokens[i+1]] for i in range(max(0,segments[0][0]),min(segments[-1][1]-1,len(tokens)-1))] if segments else []\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('two segments',solve([0,1,2,3,4],[[0,2],[2,5]]),[[0,1],[2,3],[3,4]])\ncheck('single segment',solve([1,2,3],[[0,3]]),[[1,2],[2,3]])\ncheck('singleton segment',solve([1,2],[[0,1],[1,2]]),[])\ncheck('empty segments',solve([1],[]),[])\ncheck('clipped end',solve([1,2],[[0,8]]),[[1,2]])\ncheck('offset segment',solve([0,1,2,3],[[2,4]]),[[2,3]])\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":"Inputs are toy integer token sequences; this contract says nothing about model quality, batching, sampling, or production training frameworks. 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":"w3-autoregressive-target-shifting-pair-target-boundary","generated_at":"2026-09-30T16:48:11.933724+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"A small deterministic token-stream contract makes next-token alignment errors inspectable.","root_cause":"Adjacent pairs are generated across a declared segment boundary.","sha256":"90f72d32e6799b7fa9a03473f99289c12e386cba2622eb295318e73b734d1e02","title":"A boundary input predicts the first token of the next segment · case 01","variant":1,"variant_policy":"The same explicitly authored fixtures repeat across all five numbered records; runtime N is unused. These records share one mechanism and must remain together in evaluation splits.","verified":true,"visibility":"public","verification":{"attempt":{"elapsed_ms":28.433,"exit_code":1,"observations":[{"actual":[[3,4]],"check":"two segments","expected":[[0,1],[2,3],[3,4]],"passed":false},{"actual":[[2,3]],"check":"single segment","expected":[[1,2],[2,3]],"passed":false},{"actual":[],"check":"singleton segment","expected":[],"passed":true},{"actual":[],"check":"empty segments","expected":[],"passed":true},{"actual":[],"check":"clipped end","expected":[[1,2]],"passed":false},{"actual":[],"check":"offset segment","expected":[[2,3]],"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"two segments\", \"actual\": [[3, 4]], \"expected\": [[0, 1], [2, 3], [3, 4]], \"passed\": false}, {\"check\": \"single segment\", \"actual\": [[2, 3]], \"expected\": [[1, 2], [2, 3]], \"passed\": false}, {\"check\": \"singleton segment\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"empty segments\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"clipped end\", \"actual\": [], \"expected\": [[1, 2]], \"passed\": false}, {\"check\": \"offset segment\", \"actual\": [], \"expected\": [[2, 3]], \"passed\": false}], \"passed\": false}\n"},"broken":{"elapsed_ms":28.21,"exit_code":1,"observations":[{"actual":[[0,1],[1,2],[2,3],[3,4]],"check":"two segments","expected":[[0,1],[2,3],[3,4]],"passed":false},{"actual":[[1,2],[2,3]],"check":"single segment","expected":[[1,2],[2,3]],"passed":true},{"actual":[[1,2]],"check":"singleton segment","expected":[],"passed":false},{"actual":[],"check":"empty segments","expected":[],"passed":true},{"actual":[[1,2]],"check":"clipped end","expected":[[1,2]],"passed":true},{"actual":[[2,3]],"check":"offset segment","expected":[[2,3]],"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"two segments\", \"actual\": [[0, 1], [1, 2], [2, 3], [3, 4]], \"expected\": [[0, 1], [2, 3], [3, 4]], \"passed\": false}, {\"check\": \"single segment\", \"actual\": [[1, 2], [2, 3]], \"expected\": [[1, 2], [2, 3]], \"passed\": true}, {\"check\": \"singleton segment\", \"actual\": [[1, 2]], \"expected\": [], \"passed\": false}, {\"check\": \"empty segments\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"clipped end\", \"actual\": [[1, 2]], \"expected\": [[1, 2]], \"passed\": true}, {\"check\": \"offset segment\", \"actual\": [[2, 3]], \"expected\": [[2, 3]], \"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."}}