{"abstract":"Neighboring context expands on the wrong side of an anchor.","category":"RAG context assembly","checks":6,"contract":"Given ordered texts, anchor index, and left/right counts, return the inclusive anchor window clipped to list bounds.","contract_signature":"items, anchor, left, right","evaluation_group":"ragctx-anchor-window","failed_approach":"The attempted exclusive upper bound is computed without including the anchor position, dropping the anchor or its last right neighbor.","family":"w3-rag-context-assembly-anchor-window-expansion","id":"FA-99596","implementations":{"attempt":{"sha256":"7366e767cbf5afa0a6c58390cda0d50238a7a5c9810c72bd97caf1f6d9e03b22","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(items, anchor, left, right):\n    lo=max(0,anchor-left); hi=min(len(items),anchor+right)\n    return items[lo:hi]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\nitems=['a','b','c','d','e']\ncheck('centered', solve(items,2,1,2), ['b','c','d','e'])\ncheck('left edge', solve(items,0,2,1), ['a','b'])\ncheck('right edge', solve(items,4,1,2), ['d','e'])\ncheck('single anchor', solve(items,2,0,0), ['c'])\ncheck('empty input', solve([],0,1,1), [])\ncheck('whole window', solve(items,2,9,9), items)\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":"8fa14652e8bc5c9f636e414adeaa67c6f04c97c9233294390b5e1b019fbca046","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(items, anchor, left, right):\n    return items[anchor:anchor+left+right+1]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\nitems=['a','b','c','d','e']\ncheck('centered', solve(items,2,1,2), ['b','c','d','e'])\ncheck('left edge', solve(items,0,2,1), ['a','b'])\ncheck('right edge', solve(items,4,1,2), ['d','e'])\ncheck('single anchor', solve(items,2,0,0), ['c'])\ncheck('empty input', solve([],0,1,1), [])\ncheck('whole window', solve(items,2,9,9), items)\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":"Toy inputs and token counts only; this does not claim compatibility with a tokenizer, prompt format, or production retrieval system. 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-rag-context-assembly-anchor-window-expansion","generated_at":"2026-09-30T16:48:25.834982+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"A small deterministic evidence assembly model makes context budgeting behavior inspectable.","root_cause":"A local evidence window uses a forward offset where the contract defines a centered window.","sha256":"00f6ad798f53c317eadd66c4e0b66eb5fc27be00f5065cfd7fa289a6e362b28e","title":"Neighboring context expands on the wrong side of an anchor · 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":32.276,"exit_code":1,"observations":[{"actual":["b","c","d"],"check":"centered","expected":["b","c","d","e"],"passed":false},{"actual":["a"],"check":"left edge","expected":["a","b"],"passed":false},{"actual":["d","e"],"check":"right edge","expected":["d","e"],"passed":true},{"actual":[],"check":"single anchor","expected":["c"],"passed":false},{"actual":[],"check":"empty input","expected":[],"passed":true},{"actual":["a","b","c","d","e"],"check":"whole window","expected":["a","b","c","d","e"],"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"centered\", \"actual\": [\"b\", \"c\", \"d\"], \"expected\": [\"b\", \"c\", \"d\", \"e\"], \"passed\": false}, {\"check\": \"left edge\", \"actual\": [\"a\"], \"expected\": [\"a\", \"b\"], \"passed\": false}, {\"check\": \"right edge\", \"actual\": [\"d\", \"e\"], \"expected\": [\"d\", \"e\"], \"passed\": true}, {\"check\": \"single anchor\", \"actual\": [], \"expected\": [\"c\"], \"passed\": false}, {\"check\": \"empty input\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"whole window\", \"actual\": [\"a\", \"b\", \"c\", \"d\", \"e\"], \"expected\": [\"a\", \"b\", \"c\", \"d\", \"e\"], \"passed\": true}], \"passed\": false}\n"},"broken":{"elapsed_ms":29.904,"exit_code":1,"observations":[{"actual":["c","d","e"],"check":"centered","expected":["b","c","d","e"],"passed":false},{"actual":["a","b","c","d"],"check":"left edge","expected":["a","b"],"passed":false},{"actual":["e"],"check":"right edge","expected":["d","e"],"passed":false},{"actual":["c"],"check":"single anchor","expected":["c"],"passed":true},{"actual":[],"check":"empty input","expected":[],"passed":true},{"actual":["c","d","e"],"check":"whole window","expected":["a","b","c","d","e"],"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"centered\", \"actual\": [\"c\", \"d\", \"e\"], \"expected\": [\"b\", \"c\", \"d\", \"e\"], \"passed\": false}, {\"check\": \"left edge\", \"actual\": [\"a\", \"b\", \"c\", \"d\"], \"expected\": [\"a\", \"b\"], \"passed\": false}, {\"check\": \"right edge\", \"actual\": [\"e\"], \"expected\": [\"d\", \"e\"], \"passed\": false}, {\"check\": \"single anchor\", \"actual\": [\"c\"], \"expected\": [\"c\"], \"passed\": true}, {\"check\": \"empty input\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"whole window\", \"actual\": [\"c\", \"d\", \"e\"], \"expected\": [\"a\", \"b\", \"c\", \"d\", \"e\"], \"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."}}