{"abstract":"Read-ahead respects both stream credit and remaining range bytes.","category":"HTTP ranges","checks":6,"contract":"Return the next permitted read size min(credit,remaining,block), all nonnegative.","evaluation_group":"s3-http_ranges-stream-transfer","failed_approach":"The partial repair uses return min(credit,block), which still violates the stated contract.","family":"s3-http_ranges-stream-credit-backpressure","id":"FA-26546","implementations":{"attempt":{"sha256":"4df796570e880002c6a8c630a5c32f7aad72f22216e217966880476e69df531c","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(credit, remaining, block):\n    return min(credit,block)\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('stream-credit-backpressure fixture 0', solve(N,3*N,2*N), N)\ncheck('stream-credit-backpressure fixture 1', solve(3*N,N,2*N), N)\ncheck('stream-credit-backpressure fixture 2', solve(3*N,3*N,N), N)\ncheck('stream-credit-backpressure fixture 3', solve(0,N,N), 0)\ncheck('stream-credit-backpressure fixture 4', solve(N,0,N), 0)\ncheck('stream-credit-backpressure fixture 5', solve(N,N,0), 0)\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":"96ecf23cff8166c2e4ba7c9b24f8811a955be4f56dac9341721bca1d7f008e57","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(credit, remaining, block):\n    return min(remaining,block)\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('stream-credit-backpressure fixture 0', solve(N,3*N,2*N), N)\ncheck('stream-credit-backpressure fixture 1', solve(3*N,N,2*N), N)\ncheck('stream-credit-backpressure fixture 2', solve(3*N,3*N,N), N)\ncheck('stream-credit-backpressure fixture 3', solve(0,N,N), 0)\ncheck('stream-credit-backpressure fixture 4', solve(N,0,N), 0)\ncheck('stream-credit-backpressure fixture 5', solve(N,N,0), 0)\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"},"fixed":{"sha256":"aac95db9276c126a0af01a12671d5066fa354d4840c30b5c698a5457a7338ab1","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(credit, remaining, block):\n    return min(credit,remaining,block)\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('stream-credit-backpressure fixture 0', solve(N,3*N,2*N), N)\ncheck('stream-credit-backpressure fixture 1', solve(3*N,N,2*N), N)\ncheck('stream-credit-backpressure fixture 2', solve(3*N,3*N,N), N)\ncheck('stream-credit-backpressure fixture 3', solve(0,N,N), 0)\ncheck('stream-credit-backpressure fixture 4', solve(N,0,N), 0)\ncheck('stream-credit-backpressure fixture 5', solve(N,N,0), 0)\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":"Deterministic simplified range service, with stipulated local policies and already parsed trusted inputs; not a complete HTTP implementation. 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":"s3-http_ranges-stream-credit-backpressure","generated_at":"2026-09-29T14:41:16.933155+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"Range responses combine representation identity, conditional requests, framing, and partial-object state.","repair":"Apply the bounded decision exactly: return min(credit,remaining,block)","root_cause":"The stream-credit-backpressure decision uses return min(remaining,block).","sha256":"51e03d29d174928f3ad7168adf3be07e4e066d1c832dec4e3d29b5f7d9869caa","title":"Read-ahead respects both stream credit and remaining range bytes · case 01","variant":1,"variant_policy":"Five numbered records share a model and may reuse boundary fixtures.","verification":{"attempt":{"elapsed_ms":37.616,"exit_code":1,"observations":[{"actual":1,"check":"stream-credit-backpressure fixture 0","expected":1,"passed":true},{"actual":2,"check":"stream-credit-backpressure fixture 1","expected":1,"passed":false},{"actual":1,"check":"stream-credit-backpressure fixture 2","expected":1,"passed":true},{"actual":0,"check":"stream-credit-backpressure fixture 3","expected":0,"passed":true},{"actual":1,"check":"stream-credit-backpressure fixture 4","expected":0,"passed":false},{"actual":0,"check":"stream-credit-backpressure fixture 5","expected":0,"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"stream-credit-backpressure fixture 0\", \"actual\": 1, \"expected\": 1, \"passed\": true}, {\"check\": \"stream-credit-backpressure fixture 1\", \"actual\": 2, \"expected\": 1, \"passed\": false}, {\"check\": \"stream-credit-backpressure fixture 2\", \"actual\": 1, \"expected\": 1, \"passed\": true}, {\"check\": \"stream-credit-backpressure fixture 3\", \"actual\": 0, \"expected\": 0, \"passed\": true}, {\"check\": \"stream-credit-backpressure fixture 4\", \"actual\": 1, \"expected\": 0, \"passed\": false}, {\"check\": \"stream-credit-backpressure fixture 5\", \"actual\": 0, \"expected\": 0, \"passed\": true}], \"passed\": false}\n"},"broken":{"elapsed_ms":41.937,"exit_code":1,"observations":[{"actual":2,"check":"stream-credit-backpressure fixture 0","expected":1,"passed":false},{"actual":1,"check":"stream-credit-backpressure fixture 1","expected":1,"passed":true},{"actual":1,"check":"stream-credit-backpressure fixture 2","expected":1,"passed":true},{"actual":1,"check":"stream-credit-backpressure fixture 3","expected":0,"passed":false},{"actual":0,"check":"stream-credit-backpressure fixture 4","expected":0,"passed":true},{"actual":0,"check":"stream-credit-backpressure fixture 5","expected":0,"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"stream-credit-backpressure fixture 0\", \"actual\": 2, \"expected\": 1, \"passed\": false}, {\"check\": \"stream-credit-backpressure fixture 1\", \"actual\": 1, \"expected\": 1, \"passed\": true}, {\"check\": \"stream-credit-backpressure fixture 2\", \"actual\": 1, \"expected\": 1, \"passed\": true}, {\"check\": \"stream-credit-backpressure fixture 3\", \"actual\": 1, \"expected\": 0, \"passed\": false}, {\"check\": \"stream-credit-backpressure fixture 4\", \"actual\": 0, \"expected\": 0, \"passed\": true}, {\"check\": \"stream-credit-backpressure fixture 5\", \"actual\": 0, \"expected\": 0, \"passed\": true}], \"passed\": false}\n"},"fixed":{"elapsed_ms":39.171,"exit_code":0,"observations":[{"actual":1,"check":"stream-credit-backpressure fixture 0","expected":1,"passed":true},{"actual":1,"check":"stream-credit-backpressure fixture 1","expected":1,"passed":true},{"actual":1,"check":"stream-credit-backpressure fixture 2","expected":1,"passed":true},{"actual":0,"check":"stream-credit-backpressure fixture 3","expected":0,"passed":true},{"actual":0,"check":"stream-credit-backpressure fixture 4","expected":0,"passed":true},{"actual":0,"check":"stream-credit-backpressure fixture 5","expected":0,"passed":true}],"passed":true,"stderr":"","stdout":"{\"observations\": [{\"check\": \"stream-credit-backpressure fixture 0\", \"actual\": 1, \"expected\": 1, \"passed\": true}, {\"check\": \"stream-credit-backpressure fixture 1\", \"actual\": 1, \"expected\": 1, \"passed\": true}, {\"check\": \"stream-credit-backpressure fixture 2\", \"actual\": 1, \"expected\": 1, \"passed\": true}, {\"check\": \"stream-credit-backpressure fixture 3\", \"actual\": 0, \"expected\": 0, \"passed\": true}, {\"check\": \"stream-credit-backpressure fixture 4\", \"actual\": 0, \"expected\": 0, \"passed\": true}, {\"check\": \"stream-credit-backpressure fixture 5\", \"actual\": 0, \"expected\": 0, \"passed\": true}], \"passed\": true}\n"}},"verified":true,"visibility":"public"}