{"abstract":"A black king on d7 checked from d1 is allowed to step to d8.","category":"Chess move legality","checks":8,"contract":"Input: {\"wk\", \"wq\", \"bk\"} squares, black to move. Return \"checkmate\" if black has no legal king move and is attacked by the queen, \"stalemate\" if it has none and is not attacked, else \"ongoing\". The queen attacks along ranks, files and diagonals and is blocked only by the white king; the black king may capture the queen when it is not adjacent to the white king.","contract_signature":"x","evaluation_group":"w2-chess_move_legality-kqk-terminal-status","failed_approach":"Ignoring every blocker makes the white king transparent to the queen.","family":"w2-chess_move_legality-kqk-terminal-status-escape-square-shield","id":"FA-82781","implementations":{"attempt":{"sha256":"766ae63e279ce7397f441c0d5fba26260490f90f5ebac0aa5e53377249643e32","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(x):\n    def c(q): return ord(q[0])-97,int(q[1])-1\n    wk,wq,bk=c(x['wk']),c(x['wq']),c(x['bk'])\n    def queen_hits(t, occupied):\n        if t==wq: return False\n        df,dr=t[0]-wq[0],t[1]-wq[1]\n        if not (df==0 or dr==0 or abs(df)==abs(dr)): return False\n        sf=(df>0)-(df<0); sr=(dr>0)-(dr<0)\n        f,r=wq[0]+sf,wq[1]+sr\n        while (f,r)!=t:\n            if (f,r) in occupied: return False\n            f+=sf; r+=sr\n        return True\n    def near(a,b2): return max(abs(a[0]-b2[0]),abs(a[1]-b2[1]))<=1\n    in_check=queen_hits(bk,{wk})\n    moves=0\n    for df in (-1,0,1):\n        for dr in (-1,0,1):\n            if not (df or dr): continue\n            t=(bk[0]+df,bk[1]+dr)\n            if not (0<=t[0]<8 and 0<=t[1]<8): continue\n            if near(t,wk): continue\n            if queen_hits(t,{wk,bk}): continue\n            moves+=1\n    if moves: return 'ongoing'\n    return 'checkmate' if in_check else 'stalemate'\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\nfixtures = [[('corner stalemate', {'bk': 'a8', 'wk': 'c6', 'wq': 'b6'}, 'stalemate'),\n  ('queen kiss mate', {'bk': 'a8', 'wk': 'b6', 'wq': 'b7'}, 'checkmate'),\n  ('back rank long mate', {'bk': 'h8', 'wk': 'g6', 'wq': 'a8'}, 'checkmate'),\n  ('capture free queen', {'bk': 'a8', 'wk': 'h1', 'wq': 'b7'}, 'ongoing'),\n  ('queen check escape', {'bk': 'e5', 'wk': 'a1', 'wq': 'e1'}, 'ongoing'),\n  ('queen behind white king', {'bk': 'a1', 'wk': 'b3', 'wq': 'b5'}, 'ongoing'),\n  ('mate with rank retreat', {'bk': 'b1', 'wk': 'a3', 'wq': 'd1'}, 'checkmate'),\n  ('queen kiss far side', {'bk': 'b8', 'wk': 'a6', 'wq': 'd8'}, 'checkmate')],\n [('capture free queen', {'bk': 'a8', 'wk': 'h1', 'wq': 'b7'}, 'ongoing'),\n  ('queen check escape', {'bk': 'e5', 'wk': 'a1', 'wq': 'e1'}, 'ongoing'),\n  ('shielded by king', {'bk': 'e5', 'wk': 'e3', 'wq': 'e1'}, 'ongoing'),\n  ('stalemate h-file', {'bk': 'h8', 'wk': 'f7', 'wq': 'g6'}, 'stalemate'),\n  ('queen behind white king', {'bk': 'a1', 'wk': 'b3', 'wq': 'b5'}, 'ongoing'),\n  ('mate with rank retreat', {'bk': 'b1', 'wk': 'a3', 'wq': 'd1'}, 'checkmate'),\n  ('queen kiss far side', {'bk': 'b8', 'wk': 'a6', 'wq': 'd8'}, 'checkmate'),\n  ('edge mate', {'bk': 'e8', 'wk': 'e6', 'wq': 'e7'}, 'checkmate')],\n [('stalemate h-file', {'bk': 'h8', 'wk': 'f7', 'wq': 'g6'}, 'stalemate'),\n  ('queen behind white king', {'bk': 'a1', 'wk': 'b3', 'wq': 'b5'}, 'ongoing'),\n  ('mate with rank retreat', {'bk': 'b1', 'wk': 'a3', 'wq': 'd1'}, 'checkmate'),\n  ('queen kiss far side', {'bk': 'b8', 'wk': 'a6', 'wq': 'd8'}, 'checkmate'),\n  ('edge mate', {'bk': 'e8', 'wk': 'e6', 'wq': 'e7'}, 'checkmate'),\n  ('orthogonal free capture', {'bk': 'a8', 'wk': 'h1', 'wq': 'a7'}, 'ongoing'),\n  ('far queen ongoing', {'bk': 'd5', 'wk': 'a1', 'wq': 'h2'}, 'ongoing'),\n  ('king retreat along queen file', {'bk': 'd7', 'wk': 'a1', 'wq': 'd1'}, 'ongoing')],\n [('corner stalemate', {'bk': 'a8', 'wk': 'c6', 'wq': 'b6'}, 'stalemate'),\n  ('queen kiss mate', {'bk': 'a8', 'wk': 'b6', 'wq': 'b7'}, 'checkmate'),\n  ('back rank long mate', {'bk': 'h8', 'wk': 'g6', 'wq': 'a8'}, 'checkmate'),\n  ('queen behind white king', {'bk': 'a1', 'wk': 'b3', 'wq': 'b5'}, 'ongoing'),\n  ('mate with rank retreat', {'bk': 'b1', 'wk': 'a3', 'wq': 'd1'}, 'checkmate'),\n  ('queen kiss far side', {'bk': 'b8', 'wk': 'a6', 'wq': 'd8'}, 'checkmate'),\n  ('far queen ongoing', {'bk': 'd5', 'wk': 'a1', 'wq': 'h2'}, 'ongoing'),\n  ('king retreat along queen file', {'bk': 'd7', 'wk': 'a1', 'wq': 'd1'}, 'ongoing')],\n [('corner stalemate', {'bk': 'a8', 'wk': 'c6', 'wq': 'b6'}, 'stalemate'),\n  ('queen kiss mate', {'bk': 'a8', 'wk': 'b6', 'wq': 'b7'}, 'checkmate'),\n  ('back rank long mate', {'bk': 'h8', 'wk': 'g6', 'wq': 'a8'}, 'checkmate'),\n  ('capture free queen', {'bk': 'a8', 'wk': 'h1', 'wq': 'b7'}, 'ongoing'),\n  ('queen check escape', {'bk': 'e5', 'wk': 'a1', 'wq': 'e1'}, 'ongoing'),\n  ('queen behind white king', {'bk': 'a1', 'wk': 'b3', 'wq': 'b5'}, 'ongoing'),\n  ('mate with rank retreat', {'bk': 'b1', 'wk': 'a3', 'wq': 'd1'}, 'checkmate'),\n  ('queen kiss far side', {'bk': 'b8', 'wk': 'a6', 'wq': 'd8'}, 'checkmate')]]\nfor label, args, expected in fixtures[N-1]:\n    try:\n        actual = solve(args)\n    except Exception as exc:\n        actual = 'error:' + type(exc).__name__\n    check(label, actual, expected)\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":"ab8ea20ef261e392c18fba2dd2e09071759b48188ba3010752cdeae6cd4265ac","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(x):\n    def c(q): return ord(q[0])-97,int(q[1])-1\n    wk,wq,bk=c(x['wk']),c(x['wq']),c(x['bk'])\n    def queen_hits(t, occupied):\n        if t==wq: return False\n        df,dr=t[0]-wq[0],t[1]-wq[1]\n        if not (df==0 or dr==0 or abs(df)==abs(dr)): return False\n        sf=(df>0)-(df<0); sr=(dr>0)-(dr<0)\n        f,r=wq[0]+sf,wq[1]+sr\n        while (f,r)!=t:\n            if (f,r) in occupied: return False\n            f+=sf; r+=sr\n        return True\n    def near(a,b2): return max(abs(a[0]-b2[0]),abs(a[1]-b2[1]))<=1\n    in_check=queen_hits(bk,{wk})\n    moves=0\n    for df in (-1,0,1):\n        for dr in (-1,0,1):\n            if not (df or dr): continue\n            t=(bk[0]+df,bk[1]+dr)\n            if not (0<=t[0]<8 and 0<=t[1]<8): continue\n            if near(t,wk): continue\n            if queen_hits(t,set()): continue\n            moves+=1\n    if moves: return 'ongoing'\n    return 'checkmate' if in_check else 'stalemate'\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\nfixtures = [[('corner stalemate', {'bk': 'a8', 'wk': 'c6', 'wq': 'b6'}, 'stalemate'),\n  ('queen kiss mate', {'bk': 'a8', 'wk': 'b6', 'wq': 'b7'}, 'checkmate'),\n  ('back rank long mate', {'bk': 'h8', 'wk': 'g6', 'wq': 'a8'}, 'checkmate'),\n  ('capture free queen', {'bk': 'a8', 'wk': 'h1', 'wq': 'b7'}, 'ongoing'),\n  ('queen check escape', {'bk': 'e5', 'wk': 'a1', 'wq': 'e1'}, 'ongoing'),\n  ('queen behind white king', {'bk': 'a1', 'wk': 'b3', 'wq': 'b5'}, 'ongoing'),\n  ('mate with rank retreat', {'bk': 'b1', 'wk': 'a3', 'wq': 'd1'}, 'checkmate'),\n  ('queen kiss far side', {'bk': 'b8', 'wk': 'a6', 'wq': 'd8'}, 'checkmate')],\n [('capture free queen', {'bk': 'a8', 'wk': 'h1', 'wq': 'b7'}, 'ongoing'),\n  ('queen check escape', {'bk': 'e5', 'wk': 'a1', 'wq': 'e1'}, 'ongoing'),\n  ('shielded by king', {'bk': 'e5', 'wk': 'e3', 'wq': 'e1'}, 'ongoing'),\n  ('stalemate h-file', {'bk': 'h8', 'wk': 'f7', 'wq': 'g6'}, 'stalemate'),\n  ('queen behind white king', {'bk': 'a1', 'wk': 'b3', 'wq': 'b5'}, 'ongoing'),\n  ('mate with rank retreat', {'bk': 'b1', 'wk': 'a3', 'wq': 'd1'}, 'checkmate'),\n  ('queen kiss far side', {'bk': 'b8', 'wk': 'a6', 'wq': 'd8'}, 'checkmate'),\n  ('edge mate', {'bk': 'e8', 'wk': 'e6', 'wq': 'e7'}, 'checkmate')],\n [('stalemate h-file', {'bk': 'h8', 'wk': 'f7', 'wq': 'g6'}, 'stalemate'),\n  ('queen behind white king', {'bk': 'a1', 'wk': 'b3', 'wq': 'b5'}, 'ongoing'),\n  ('mate with rank retreat', {'bk': 'b1', 'wk': 'a3', 'wq': 'd1'}, 'checkmate'),\n  ('queen kiss far side', {'bk': 'b8', 'wk': 'a6', 'wq': 'd8'}, 'checkmate'),\n  ('edge mate', {'bk': 'e8', 'wk': 'e6', 'wq': 'e7'}, 'checkmate'),\n  ('orthogonal free capture', {'bk': 'a8', 'wk': 'h1', 'wq': 'a7'}, 'ongoing'),\n  ('far queen ongoing', {'bk': 'd5', 'wk': 'a1', 'wq': 'h2'}, 'ongoing'),\n  ('king retreat along queen file', {'bk': 'd7', 'wk': 'a1', 'wq': 'd1'}, 'ongoing')],\n [('corner stalemate', {'bk': 'a8', 'wk': 'c6', 'wq': 'b6'}, 'stalemate'),\n  ('queen kiss mate', {'bk': 'a8', 'wk': 'b6', 'wq': 'b7'}, 'checkmate'),\n  ('back rank long mate', {'bk': 'h8', 'wk': 'g6', 'wq': 'a8'}, 'checkmate'),\n  ('queen behind white king', {'bk': 'a1', 'wk': 'b3', 'wq': 'b5'}, 'ongoing'),\n  ('mate with rank retreat', {'bk': 'b1', 'wk': 'a3', 'wq': 'd1'}, 'checkmate'),\n  ('queen kiss far side', {'bk': 'b8', 'wk': 'a6', 'wq': 'd8'}, 'checkmate'),\n  ('far queen ongoing', {'bk': 'd5', 'wk': 'a1', 'wq': 'h2'}, 'ongoing'),\n  ('king retreat along queen file', {'bk': 'd7', 'wk': 'a1', 'wq': 'd1'}, 'ongoing')],\n [('corner stalemate', {'bk': 'a8', 'wk': 'c6', 'wq': 'b6'}, 'stalemate'),\n  ('queen kiss mate', {'bk': 'a8', 'wk': 'b6', 'wq': 'b7'}, 'checkmate'),\n  ('back rank long mate', {'bk': 'h8', 'wk': 'g6', 'wq': 'a8'}, 'checkmate'),\n  ('capture free queen', {'bk': 'a8', 'wk': 'h1', 'wq': 'b7'}, 'ongoing'),\n  ('queen check escape', {'bk': 'e5', 'wk': 'a1', 'wq': 'e1'}, 'ongoing'),\n  ('queen behind white king', {'bk': 'a1', 'wk': 'b3', 'wq': 'b5'}, 'ongoing'),\n  ('mate with rank retreat', {'bk': 'b1', 'wk': 'a3', 'wq': 'd1'}, 'checkmate'),\n  ('queen kiss far side', {'bk': 'b8', 'wk': 'a6', 'wq': 'd8'}, 'checkmate')]]\nfor label, args, expected in fixtures[N-1]:\n    try:\n        actual = solve(args)\n    except Exception as exc:\n        actual = 'error:' + type(exc).__name__\n    check(label, actual, expected)\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":"A deterministic toy model with an explicitly stated contract; boards are {square: piece} with white upper-case and black lower-case pieces; no claim of full FIDE Laws conformance. 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":"w2-chess_move_legality-kqk-terminal-status-escape-square-shield","generated_at":"2026-09-29T14:50:15.332768+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"Game-end detection must distinguish mate from stalemate exactly.","root_cause":"The black king's origin square is treated as a shield when testing its own escape squares.","sha256":"49666560b8435d5f9ceafc9bef450a071c18bdf601e23be04f107b49cbfe7014","title":"King may retreat along the queen's line · case 01","variant":1,"variant_policy":"Five numbered records share a model and may reuse boundary fixtures.","verified":true,"visibility":"public","verification":{"attempt":{"elapsed_ms":44.226,"exit_code":1,"observations":[{"actual":"stalemate","check":"corner stalemate","expected":"stalemate","passed":true},{"actual":"checkmate","check":"queen kiss mate","expected":"checkmate","passed":true},{"actual":"checkmate","check":"back rank long mate","expected":"checkmate","passed":true},{"actual":"ongoing","check":"capture free queen","expected":"ongoing","passed":true},{"actual":"ongoing","check":"queen check escape","expected":"ongoing","passed":true},{"actual":"ongoing","check":"queen behind white king","expected":"ongoing","passed":true},{"actual":"ongoing","check":"mate with rank retreat","expected":"checkmate","passed":false},{"actual":"ongoing","check":"queen kiss far side","expected":"checkmate","passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"corner stalemate\", \"actual\": \"stalemate\", \"expected\": \"stalemate\", \"passed\": true}, {\"check\": \"queen kiss mate\", \"actual\": \"checkmate\", \"expected\": \"checkmate\", \"passed\": true}, {\"check\": \"back rank long mate\", \"actual\": \"checkmate\", \"expected\": \"checkmate\", \"passed\": true}, {\"check\": \"capture free queen\", \"actual\": \"ongoing\", \"expected\": \"ongoing\", \"passed\": true}, {\"check\": \"queen check escape\", \"actual\": \"ongoing\", \"expected\": \"ongoing\", \"passed\": true}, {\"check\": \"queen behind white king\", \"actual\": \"ongoing\", \"expected\": \"ongoing\", \"passed\": true}, {\"check\": \"mate with rank retreat\", \"actual\": \"ongoing\", \"expected\": \"checkmate\", \"passed\": false}, {\"check\": \"queen kiss far side\", \"actual\": \"ongoing\", \"expected\": \"checkmate\", \"passed\": false}], \"passed\": false}\n"},"broken":{"elapsed_ms":41.681,"exit_code":1,"observations":[{"actual":"stalemate","check":"corner stalemate","expected":"stalemate","passed":true},{"actual":"checkmate","check":"queen kiss mate","expected":"checkmate","passed":true},{"actual":"checkmate","check":"back rank long mate","expected":"checkmate","passed":true},{"actual":"ongoing","check":"capture free queen","expected":"ongoing","passed":true},{"actual":"ongoing","check":"queen check escape","expected":"ongoing","passed":true},{"actual":"stalemate","check":"queen behind white king","expected":"ongoing","passed":false},{"actual":"checkmate","check":"mate with rank retreat","expected":"checkmate","passed":true},{"actual":"checkmate","check":"queen kiss far side","expected":"checkmate","passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"corner stalemate\", \"actual\": \"stalemate\", \"expected\": \"stalemate\", \"passed\": true}, {\"check\": \"queen kiss mate\", \"actual\": \"checkmate\", \"expected\": \"checkmate\", \"passed\": true}, {\"check\": \"back rank long mate\", \"actual\": \"checkmate\", \"expected\": \"checkmate\", \"passed\": true}, {\"check\": \"capture free queen\", \"actual\": \"ongoing\", \"expected\": \"ongoing\", \"passed\": true}, {\"check\": \"queen check escape\", \"actual\": \"ongoing\", \"expected\": \"ongoing\", \"passed\": true}, {\"check\": \"queen behind white king\", \"actual\": \"stalemate\", \"expected\": \"ongoing\", \"passed\": false}, {\"check\": \"mate with rank retreat\", \"actual\": \"checkmate\", \"expected\": \"checkmate\", \"passed\": true}, {\"check\": \"queen kiss far side\", \"actual\": \"checkmate\", \"expected\": \"checkmate\", \"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."}}