{"abstract":"A segment start loses its first valid target pair.","category":"Autoregressive target shifting","checks":6,"contract":"For each [start,end) segment, include i=start..end-2 when both tokens exist.","contract_signature":"tokens, segments","evaluation_group":"w3-ars-pair_boundaries","failed_approach":"Using inclusive segment ends includes the first token owned by the following segment.","family":"w3-autoregressive-target-shifting-pair-boundary-origin","id":"FA-98326","implementations":{"attempt":{"sha256":"d4549e4b09fb8b1510ee8ce6dca51f936962e070ab5d4cbf27ff060417cae44d","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),min(b,len(tokens)-1))]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('first pair retained',solve([0,1,2,3],[[1,4]]),[[1,2],[2,3]])\ncheck('adjacent segments',solve([0,1,2,3],[[0,2],[2,4]]),[[0,1],[2,3]])\ncheck('length two',solve([5,6],[[0,2]]),[[5,6]])\ncheck('length one',solve([5],[[0,1]]),[])\ncheck('empty',solve([],[[0,0]]),[])\ncheck('end clipped',solve([8,9],[[0,9]]),[[8,9]])\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":"1397d913584661a2227cff638629515b3163eb957cd78d6355f0f9c88c293c86","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('first pair retained',solve([0,1,2,3],[[1,4]]),[[1,2],[2,3]])\ncheck('adjacent segments',solve([0,1,2,3],[[0,2],[2,4]]),[[0,1],[2,3]])\ncheck('length two',solve([5,6],[[0,2]]),[[5,6]])\ncheck('length one',solve([5],[[0,1]]),[])\ncheck('empty',solve([],[[0,0]]),[])\ncheck('end clipped',solve([8,9],[[0,9]]),[[8,9]])\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-boundary-origin","generated_at":"2026-09-30T16:48:11.933252+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":"The segment start is treated as a target index instead of an input index.","sha256":"d6dd66e96df8c2e934903fdb2e9f5bf34ae4f21c1a3640580a29c5880c7ff471","title":"A segment start loses its first valid target pair · 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":28.844,"exit_code":1,"observations":[{"actual":[[1,2],[2,3]],"check":"first pair retained","expected":[[1,2],[2,3]],"passed":true},{"actual":[[0,1],[1,2],[2,3]],"check":"adjacent segments","expected":[[0,1],[2,3]],"passed":false},{"actual":[[5,6]],"check":"length two","expected":[[5,6]],"passed":true},{"actual":[],"check":"length one","expected":[],"passed":true},{"actual":[],"check":"empty","expected":[],"passed":true},{"actual":[[8,9]],"check":"end clipped","expected":[[8,9]],"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"first pair retained\", \"actual\": [[1, 2], [2, 3]], \"expected\": [[1, 2], [2, 3]], \"passed\": true}, {\"check\": \"adjacent segments\", \"actual\": [[0, 1], [1, 2], [2, 3]], \"expected\": [[0, 1], [2, 3]], \"passed\": false}, {\"check\": \"length two\", \"actual\": [[5, 6]], \"expected\": [[5, 6]], \"passed\": true}, {\"check\": \"length one\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"empty\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"end clipped\", \"actual\": [[8, 9]], \"expected\": [[8, 9]], \"passed\": true}], \"passed\": false}\n"},"broken":{"elapsed_ms":27.927,"exit_code":1,"observations":[{"actual":[[2,3]],"check":"first pair retained","expected":[[1,2],[2,3]],"passed":false},{"actual":[],"check":"adjacent segments","expected":[[0,1],[2,3]],"passed":false},{"actual":[],"check":"length two","expected":[[5,6]],"passed":false},{"actual":[],"check":"length one","expected":[],"passed":true},{"actual":[],"check":"empty","expected":[],"passed":true},{"actual":[],"check":"end clipped","expected":[[8,9]],"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"first pair retained\", \"actual\": [[2, 3]], \"expected\": [[1, 2], [2, 3]], \"passed\": false}, {\"check\": \"adjacent segments\", \"actual\": [], \"expected\": [[0, 1], [2, 3]], \"passed\": false}, {\"check\": \"length two\", \"actual\": [], \"expected\": [[5, 6]], \"passed\": false}, {\"check\": \"length one\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"empty\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"end clipped\", \"actual\": [], \"expected\": [[8, 9]], \"passed\": false}], \"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."}}