{"abstract":"The final in-window context token is omitted.","category":"Autoregressive target shifting","checks":6,"contract":"For tokens and stop, pair indexes 0 through min(stop,len(tokens)-1)-1 with their successors.","contract_signature":"tokens, stop","evaluation_group":"w3-ars-context_window","failed_approach":"Making the upper bound inclusive also introduces a pair beyond the sequence end.","family":"w3-autoregressive-target-shifting-causal-window-endpoint","id":"FA-98286","implementations":{"attempt":{"sha256":"b6096891f2318591fde8c953171e0d3125a1c585d4879a8f5be13cd4cbc9be33","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(tokens, stop):\n    return [[tokens[i],tokens[i+1]] for i in range(max(0,min(stop+1,len(tokens)-1)))]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('last allowed context',solve([0,1,2,3],3),[[0,1],[1,2],[2,3]])\ncheck('one context',solve([4,5],1),[[4,5]])\ncheck('zero context',solve([4,5],0),[])\ncheck('oversized stop',solve([1,2,3],20),[[1,2],[2,3]])\ncheck('empty',solve([],3),[])\ncheck('singleton',solve([1],1),[])\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":"f72ad2fe12c4dfde9d5f81276c8f9f1258b9fc1cbcef53a1956d5ffb7243c2c1","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(tokens, stop):\n    return [[tokens[i],tokens[i+1]] for i in range(max(0,min(stop-1,len(tokens)-1)))]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('last allowed context',solve([0,1,2,3],3),[[0,1],[1,2],[2,3]])\ncheck('one context',solve([4,5],1),[[4,5]])\ncheck('zero context',solve([4,5],0),[])\ncheck('oversized stop',solve([1,2,3],20),[[1,2],[2,3]])\ncheck('empty',solve([],3),[])\ncheck('singleton',solve([1],1),[])\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-causal-window-endpoint","generated_at":"2026-09-30T16:48:11.500126+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 upper bound is derived from the truncated input window rather than its target lookahead.","sha256":"7ed3263a4b3e95dbce3f66235427b9925fb8627a01a4b2cacc12b132d669976f","title":"The final in-window context token is omitted · 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":28.776,"exit_code":1,"observations":[{"actual":[[0,1],[1,2],[2,3]],"check":"last allowed context","expected":[[0,1],[1,2],[2,3]],"passed":true},{"actual":[[4,5]],"check":"one context","expected":[[4,5]],"passed":true},{"actual":[[4,5]],"check":"zero context","expected":[],"passed":false},{"actual":[[1,2],[2,3]],"check":"oversized stop","expected":[[1,2],[2,3]],"passed":true},{"actual":[],"check":"empty","expected":[],"passed":true},{"actual":[],"check":"singleton","expected":[],"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"last allowed context\", \"actual\": [[0, 1], [1, 2], [2, 3]], \"expected\": [[0, 1], [1, 2], [2, 3]], \"passed\": true}, {\"check\": \"one context\", \"actual\": [[4, 5]], \"expected\": [[4, 5]], \"passed\": true}, {\"check\": \"zero context\", \"actual\": [[4, 5]], \"expected\": [], \"passed\": false}, {\"check\": \"oversized stop\", \"actual\": [[1, 2], [2, 3]], \"expected\": [[1, 2], [2, 3]], \"passed\": true}, {\"check\": \"empty\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"singleton\", \"actual\": [], \"expected\": [], \"passed\": true}], \"passed\": false}\n"},"broken":{"elapsed_ms":28.122,"exit_code":1,"observations":[{"actual":[[0,1],[1,2]],"check":"last allowed context","expected":[[0,1],[1,2],[2,3]],"passed":false},{"actual":[],"check":"one context","expected":[[4,5]],"passed":false},{"actual":[],"check":"zero context","expected":[],"passed":true},{"actual":[[1,2],[2,3]],"check":"oversized stop","expected":[[1,2],[2,3]],"passed":true},{"actual":[],"check":"empty","expected":[],"passed":true},{"actual":[],"check":"singleton","expected":[],"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"last allowed context\", \"actual\": [[0, 1], [1, 2]], \"expected\": [[0, 1], [1, 2], [2, 3]], \"passed\": false}, {\"check\": \"one context\", \"actual\": [], \"expected\": [[4, 5]], \"passed\": false}, {\"check\": \"zero context\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"oversized stop\", \"actual\": [[1, 2], [2, 3]], \"expected\": [[1, 2], [2, 3]], \"passed\": true}, {\"check\": \"empty\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"singleton\", \"actual\": [], \"expected\": [], \"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."}}