{"abstract":"A separator context incorrectly suppresses the following target.","category":"Autoregressive target shifting","checks":6,"contract":"Return adjacent pairs except when the target equals sep; a sep input can predict ordinary content.","contract_signature":"tokens, sep","evaluation_group":"w3-ars-special_token","failed_approach":"Suppressing both input and target occurrences loses the first valid prediction after a separator.","family":"w3-autoregressive-target-shifting-special-token-context","id":"FA-98336","implementations":{"attempt":{"sha256":"337ac8be85fb9dcc240ed35190c3d5f8beb3f6a4ea26daf59751cd5f72e76d28","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(tokens, sep):\n    return [[tokens[i],tokens[i+1]] for i in range(len(tokens)-1) if tokens[i]!=sep and tokens[i+1]!=sep]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('separator context valid',solve([1,9,2],9),[[9,2]])\ncheck('separator target invalid',solve([1,2,9],9),[[1,2]])\ncheck('multiple ordinary',solve([9,2,3],9),[[9,2],[2,3]])\ncheck('consecutive separators',solve([9,9,2],9),[[9,2]])\ncheck('empty',solve([],9),[])\ncheck('one item',solve([9],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":"41ccde2aa63f373c9dedacb18b1f7517a7829dad60c2d6ed61294ac260b6b060","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(tokens, sep):\n    return [[tokens[i],tokens[i+1]] for i in range(len(tokens)-1) if tokens[i]!=sep]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('separator context valid',solve([1,9,2],9),[[9,2]])\ncheck('separator target invalid',solve([1,2,9],9),[[1,2]])\ncheck('multiple ordinary',solve([9,2,3],9),[[9,2],[2,3]])\ncheck('consecutive separators',solve([9,9,2],9),[[9,2]])\ncheck('empty',solve([],9),[])\ncheck('one item',solve([9],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-special-token-context","generated_at":"2026-09-30T16:48:11.932993+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 filter checks the input position, although separator tokens may provide the next segment context.","sha256":"cd5361b1aaa2c19f6059801071b4f69fda56cd1bcb9a8c3ea602513c40da35c0","title":"A separator context incorrectly suppresses the following target · 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":28.918,"exit_code":1,"observations":[{"actual":[],"check":"separator context valid","expected":[[9,2]],"passed":false},{"actual":[[1,2]],"check":"separator target invalid","expected":[[1,2]],"passed":true},{"actual":[[2,3]],"check":"multiple ordinary","expected":[[9,2],[2,3]],"passed":false},{"actual":[],"check":"consecutive separators","expected":[[9,2]],"passed":false},{"actual":[],"check":"empty","expected":[],"passed":true},{"actual":[],"check":"one item","expected":[],"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"separator context valid\", \"actual\": [], \"expected\": [[9, 2]], \"passed\": false}, {\"check\": \"separator target invalid\", \"actual\": [[1, 2]], \"expected\": [[1, 2]], \"passed\": true}, {\"check\": \"multiple ordinary\", \"actual\": [[2, 3]], \"expected\": [[9, 2], [2, 3]], \"passed\": false}, {\"check\": \"consecutive separators\", \"actual\": [], \"expected\": [[9, 2]], \"passed\": false}, {\"check\": \"empty\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"one item\", \"actual\": [], \"expected\": [], \"passed\": true}], \"passed\": false}\n"},"broken":{"elapsed_ms":27.94,"exit_code":1,"observations":[{"actual":[[1,9]],"check":"separator context valid","expected":[[9,2]],"passed":false},{"actual":[[1,2],[2,9]],"check":"separator target invalid","expected":[[1,2]],"passed":false},{"actual":[[2,3]],"check":"multiple ordinary","expected":[[9,2],[2,3]],"passed":false},{"actual":[],"check":"consecutive separators","expected":[[9,2]],"passed":false},{"actual":[],"check":"empty","expected":[],"passed":true},{"actual":[],"check":"one item","expected":[],"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"separator context valid\", \"actual\": [[1, 9]], \"expected\": [[9, 2]], \"passed\": false}, {\"check\": \"separator target invalid\", \"actual\": [[1, 2], [2, 9]], \"expected\": [[1, 2]], \"passed\": false}, {\"check\": \"multiple ordinary\", \"actual\": [[2, 3]], \"expected\": [[9, 2], [2, 3]], \"passed\": false}, {\"check\": \"consecutive separators\", \"actual\": [], \"expected\": [[9, 2]], \"passed\": false}, {\"check\": \"empty\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"one item\", \"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."}}