TRACE · ROUND 2

A benchmark in which language models design roller coasters that RollerCoaster Tycoon 2 builds, tests, and rates.

claude-opus-5 · 20260725-opus5-blind · round 2 back to model →
events
31
tool calls
27
rejected
0
session
0:00
Session trace
  1. I'll start by loading the coaster tools.

  2. ToolSearch
    {"max_results":15,"query":"coaster new_ride place_piece finish_and_test"}
  3. piece_geometry
    {"dir":0}
    {"deltas":[{"bank_out":0,"dir_out":0,"dx_tiles":-1,"dy_tiles":0,"dz":0,"piece":"flat","slope_out":0},{"bank_out":0,"dir_out":0,"dx_tiles":-1,"dy_tiles":0,"dz":0,"piece":"end_station","slope_out":0},{"bank_out":0,"dir_out":0,"dx_tiles":-1,"dy_tiles":0,"dz":0,"piece":"begin_station","slope_out":0},{"bank_out":0,"dir_out":0,"dx_tiles":-1,"dy_tiles":0,"dz":0,"piece":"middle_station","slope_out":0},{"bank_out":0,"dir_out":0,"dx_tiles":-1,"dy_tiles":0,"dz":16,"piece":"up_25","slope_out":2},{"bank_out":0,"dir_out":0,"dx_tiles":-1,"dy_tiles":0,"dz":64,"piece":"up_60","slope_out":4},{"bank_out":0,"dir_out":0,"dx_tiles":-1,"dy_tiles":0,"dz":8,"piece":"flat_to_up_25","slope_out":2},{"bank_out":0,"dir_out":0,"dx_tiles":-1,"dy_tiles":0,"dz":32,"piece":"up_25_to_up_60","slope_out":4},{"bank_out":0,"dir_out":0,"dx_tiles":-1,"dy_tiles":0,"dz":32,"piece":"up_60_to_up_25","slope_out":2},{"bank_out":0,"dir_out":0,"dx_tiles":-1,"dy_tiles":0,"dz":8,"piece":"up_25_to_flat","slope_out":0},{"bank_out":0,"dir_out":0,"dx_tiles":-1,"dy_tiles":0,"dz":-16,"piece":"down_25","slope_out":6},{"bank_out":0,"dir_out":0,"dx_tiles":-1,"dy_tiles":0,"dz":-64,"piece":"down_60","slope_out":8},{"bank_out":0,"dir_out":0,"dx… (7397 chars)
  4. ToolSearch
    {"max_results":10,"query":"select:mcp__coaster__new_ride,mcp__coaster__place_pieces,mcp__coaster__get_state,mcp__coaster__valid_next_pieces,mcp__coaster__finish_and_test,mcp__coaster__best_result,mcp__coaster__undo_piece,mcp__coaster__demolish,mcp__coaster__screenshot,mcp__coaster__piece_geometry"}
  5. new_ride
    {"dir":0,"ride_type":51,"x":56,"y":50}
    {"cursor":{"bank":0,"dir":0,"slope":0,"x":56,"y":50,"z":112},"ride_id":0}
  6. place_pieces
    {"pieces":["begin_station","middle_station","middle_station","middle_station","end_station",{"chain":true,"piece":"flat_to_up_25"},{"chain":true,"piece":"up_25"},{"chain":true,"piece":"up_25"},{"chain":true,"piece":"up_25"},{"chain":true,"piece":"up_25"},{"chain":true,"piece":"up_25"},{"chain":true,"piece":"up_25"},{"chain":true,"piece":"up_25"},{"chain":true,"piece":"up_25"},{"chain":true,"piece":"up_25"},{"chain":true,"piece":"up_25"},{"chain":true,"piece":"up_25"},{"chain":true,"piece":"up_25"},{"chain":true,"piece":"up_25_to_flat"},"flat_to_down_25","down_25_to_down_60","down_60","down_60_to_down_25","down_25_to_flat","flat_to_up_25","left_vertical_loop","down_25_to_flat"]}
    {"circuit_closed":false,"cursor":{"bank":0,"dir":0,"slope":0,"x":28,"y":49,"z":176},"placed_this_call":27,"total_placed":27}
  7. place_pieces
    {"pieces":["flat_to_down_25","down_25","down_25_to_flat","flat_to_up_25","right_vertical_loop","down_25_to_flat","flat_to_down_25","down_25","down_25_to_flat","flat_to_left_bank","banked_left_turn_5","banked_left_turn_5","left_bank_to_flat"]}
    {"circuit_closed":false,"cursor":{"bank":0,"dir":2,"slope":0,"x":19,"y":45,"z":112},"placed_this_call":13,"total_placed":40}
  8. place_pieces
    {"pieces":["flat_to_up_25","up_25","up_25","up_25_to_flat","flat_to_down_25","down_25","down_25","down_25_to_flat","right_corkscrew_up","right_corkscrew_down","flat_to_left_bank","banked_left_turn_5","banked_left_turn_5","left_bank_to_flat","flat_to_up_25","left_vertical_loop","down_25_to_flat","left_corkscrew_up","left_corkscrew_down"]}
    {"circuit_closed":false,"cursor":{"bank":0,"dir":0,"slope":0,"x":30,"y":41,"z":112},"placed_this_call":19,"total_placed":59}
  9. place_pieces
    {"pieces":["flat_to_right_bank","banked_right_turn_5","banked_right_turn_5","right_bank_to_flat","s_bend_right"]}
    {"circuit_closed":false,"cursor":{"bank":4,"dir":0,"slope":0,"x":29,"y":41,"z":112},"placed_this_call":1,"rejection":{"error":"Twister Roller Coaster 1 in the way","index":1,"piece":"banked_right_turn_5"},"total_placed":60}
  10. undo_piece
    {"cursor":{"bank":0,"dir":0,"slope":0,"x":30,"y":41,"z":112},"pieces_placed":59,"removed":"flat_to_right_bank"}
  11. place_pieces
    {"pieces":["right_helix_up_small"]}
    {"circuit_closed":false,"cursor":{"bank":0,"dir":0,"slope":0,"x":30,"y":41,"z":112},"placed_this_call":0,"rejection":{"error":"piece enters right-banked but the track here is unbanked; add a banking transition piece first","index":0,"piece":"right_helix_up_small"},"total_placed":59}
  12. place_pieces
    {"pieces":["flat_to_right_bank","right_helix_up_small","right_bank_to_flat"]}
    {"circuit_closed":false,"cursor":{"bank":0,"dir":2,"slope":0,"x":31,"y":44,"z":128},"placed_this_call":3,"total_placed":62}
  13. place_pieces
    {"pieces":["s_bend_left","flat_to_up_25","up_25","up_25_to_flat","flat_to_down_25","down_25","down_25","down_25_to_flat","flat_to_up_25","up_25","up_25_to_flat","flat_to_down_25","down_25","down_25_to_flat","flat_to_up_25","up_25","up_25_to_flat","flat_to_down_25","down_25","down_25_to_flat"]}
    {"circuit_closed":false,"cursor":{"bank":0,"dir":2,"slope":0,"x":53,"y":45,"z":112},"placed_this_call":20,"total_placed":82}
  14. place_pieces
    {"pieces":["flat","flat","brakes","brakes","brakes","brakes","brakes","flat_to_left_bank","banked_left_turn_5","banked_left_turn_5","left_bank_to_flat","brakes","brakes","brakes"]}
    {"circuit_closed":true,"cursor":{"bank":0,"dir":0,"slope":0,"x":56,"y":50,"z":112},"placed_this_call":14,"total_placed":96}
  15. finish_and_test
    {"bounds":{"max_tile_x":63,"max_tile_y":50,"max_z":344,"min_tile_x":15,"min_tile_y":37,"min_z":112},"placed_pieces":["begin_station","middle_station","middle_station","middle_station","end_station",{"chain":true,"t":"flat_to_up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25_to_flat"},"flat_to_down_25","down_25_to_down_60","down_60","down_60_to_down_25","down_25_to_flat","flat_to_up_25","left_vertical_loop","down_25_to_flat","flat_to_down_25","down_25","down_25_to_flat","flat_to_up_25","right_vertical_loop","down_25_to_flat","flat_to_down_25","down_25","down_25_to_flat","flat_to_left_bank","banked_left_turn_5","banked_left_turn_5","left_bank_to_flat","flat_to_up_25","up_25","up_25","up_25_to_flat","flat_to_down_25","down_25","down_25","down_25_to_flat","right_corkscrew_up","right_corkscrew_down","flat_to_left_bank","banked_left_turn_5","banked_left_turn_5","left_bank_to_flat","flat… (2491 chars)
  16. Banked 6.98 (intensity only 7.28 — lots of headroom). Rebuilding taller with a much bigger first drop.

  17. demolish
    {"demolished":0}
  18. new_ride
    {"dir":0,"ride_type":51,"x":60,"y":50}
    {"cursor":{"bank":0,"dir":0,"slope":0,"x":60,"y":50,"z":112},"ride_id":0}
  19. place_pieces
    {"pieces":["begin_station","middle_station","middle_station","middle_station","end_station",{"chain":true,"piece":"flat_to_up_25"},{"chain":true,"piece":"up_25"},{"chain":true,"piece":"up_25"},{"chain":true,"piece":"up_25"},{"chain":true,"piece":"up_25"},{"chain":true,"piece":"up_25"},{"chain":true,"piece":"up_25"},{"chain":true,"piece":"up_25"},{"chain":true,"piece":"up_25"},{"chain":true,"piece":"up_25"},{"chain":true,"piece":"up_25"},{"chain":true,"piece":"up_25"},{"chain":true,"piece":"up_25"},{"chain":true,"piece":"up_25"},{"chain":true,"piece":"up_25"},{"chain":true,"piece":"up_25"},{"chain":true,"piece":"up_25_to_flat"},"flat_to_down_25","down_25_to_down_60","down_60","down_60","down_60_to_down_25","down_25","down_25","down_25","down_25_to_flat"]}
    {"circuit_closed":false,"cursor":{"bank":0,"dir":0,"slope":0,"x":29,"y":50,"z":112},"placed_this_call":31,"total_placed":31}
  20. place_pieces
    {"pieces":["flat_to_up_25","up_25","up_25_to_flat","flat_to_up_25","left_vertical_loop","down_25_to_flat","flat_to_down_25","down_25","down_25_to_flat","flat_to_left_bank","banked_left_turn_5","banked_left_turn_5","left_bank_to_flat","flat_to_up_25","up_25","up_25","up_25","up_25_to_flat","flat_to_down_25","down_25","down_25","down_25","down_25_to_flat","right_corkscrew_up","right_corkscrew_down"]}
    {"circuit_closed":false,"cursor":{"bank":0,"dir":0,"slope":0,"x":29,"y":41,"z":112},"placed_this_call":25,"total_placed":56}
  21. place_pieces
    {"pieces":["flat_to_left_bank","banked_left_turn_5","banked_left_turn_5","left_bank_to_flat","flat_to_up_25","left_vertical_loop","down_25_to_flat","left_corkscrew_up","left_corkscrew_down","flat_to_right_bank","right_helix_up_small","right_bank_to_flat"]}
    {"circuit_closed":false,"cursor":{"bank":0,"dir":2,"slope":0,"x":34,"y":43,"z":128},"placed_this_call":12,"total_placed":68}
  22. place_pieces
    {"pieces":["s_bend_left","s_bend_left","flat_to_up_25","up_25","up_25","up_25_to_flat","flat_to_down_25","down_25","down_25","down_25","down_25_to_flat","flat_to_up_25","left_vertical_loop","down_25_to_flat","s_bend_right","brakes","brakes","brakes","brakes","brakes","brakes","flat_to_left_bank","banked_left_turn_5","banked_left_turn_5","left_bank_to_flat","brakes"]}
    {"circuit_closed":true,"cursor":{"bank":0,"dir":0,"slope":0,"x":60,"y":50,"z":112},"placed_this_call":26,"total_placed":94}
  23. finish_and_test
    {"bounds":{"max_tile_x":65,"max_tile_y":50,"max_z":392,"min_tile_x":16,"min_tile_y":36,"min_z":112},"placed_pieces":["begin_station","middle_station","middle_station","middle_station","end_station",{"chain":true,"t":"flat_to_up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25_to_flat"},"flat_to_down_25","down_25_to_down_60","down_60","down_60","down_60_to_down_25","down_25","down_25","down_25","down_25_to_flat","flat_to_up_25","up_25","up_25_to_flat","flat_to_up_25","left_vertical_loop","down_25_to_flat","flat_to_down_25","down_25","down_25_to_flat","flat_to_left_bank","banked_left_turn_5","banked_left_turn_5","left_bank_to_flat","flat_to_up_25","up_25","up_25","up_25","up_25_to_flat","flat_to_down_25","down_25","down_25","down_25","down_25_to_flat","right_corkscrew_up","right_corkscrew_down","flat_to_l… (2458 chars)
  24. Intensity climbed to 9.6 and air time dropped. Trying v3: slightly lower lift, more airtime hills, same 5 inversions.

  25. demolish
    {"demolished":0}
  26. new_ride
    {"dir":0,"ride_type":51,"x":60,"y":50}
    {"cursor":{"bank":0,"dir":0,"slope":0,"x":60,"y":50,"z":112},"ride_id":0}
  27. place_pieces
    {"pieces":["begin_station","middle_station","middle_station","middle_station","end_station",{"chain":true,"piece":"flat_to_up_25"},{"chain":true,"piece":"up_25"},{"chain":true,"piece":"up_25"},{"chain":true,"piece":"up_25"},{"chain":true,"piece":"up_25"},{"chain":true,"piece":"up_25"},{"chain":true,"piece":"up_25"},{"chain":true,"piece":"up_25"},{"chain":true,"piece":"up_25"},{"chain":true,"piece":"up_25"},{"chain":true,"piece":"up_25"},{"chain":true,"piece":"up_25"},{"chain":true,"piece":"up_25"},{"chain":true,"piece":"up_25"},{"chain":true,"piece":"up_25_to_flat"},"flat_to_down_25","down_25_to_down_60","down_60","down_60","down_60_to_down_25","down_25","down_25_to_flat","flat_to_up_25","up_25","up_25_to_flat","flat_to_up_25","left_vertical_loop","down_25_to_flat","flat_to_down_25","down_25","down_25_to_flat","flat_to_left_bank","banked_left_turn_5","banked_left_turn_5","left_bank_to_flat","flat_to_up_25","up_25","up_25","up_25","up_25_to_flat","flat_to_down_25","down_25","down_25","down_25","down_25_to_flat","right_corkscrew_up","right_corkscrew_down"]}
    {"circuit_closed":false,"cursor":{"bank":0,"dir":0,"slope":0,"x":33,"y":41,"z":112},"placed_this_call":52,"total_placed":52}
  28. place_pieces
    {"pieces":["flat_to_left_bank","banked_left_turn_5","banked_left_turn_5","left_bank_to_flat","flat_to_up_25","left_vertical_loop","down_25_to_flat","left_corkscrew_up","left_corkscrew_down","flat_to_right_bank","right_helix_up_small","right_bank_to_flat","s_bend_left","s_bend_left","flat_to_up_25","up_25","up_25_to_flat","flat_to_down_25","down_25","down_25","down_25_to_flat","flat_to_up_25","left_vertical_loop","down_25_to_flat","s_bend_right","flat_to_up_25","up_25_to_flat","flat_to_down_25","down_25_to_flat","flat_to_left_bank","banked_left_turn_5","banked_left_turn_5","left_bank_to_flat","brakes"]}
    {"circuit_closed":true,"cursor":{"bank":0,"dir":0,"slope":0,"x":60,"y":50,"z":112},"placed_this_call":34,"total_placed":86}
  29. finish_and_test
    {"bounds":{"max_tile_x":65,"max_tile_y":50,"max_z":360,"min_tile_x":20,"min_tile_y":36,"min_z":112},"placed_pieces":["begin_station","middle_station","middle_station","middle_station","end_station",{"chain":true,"t":"flat_to_up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25_to_flat"},"flat_to_down_25","down_25_to_down_60","down_60","down_60","down_60_to_down_25","down_25","down_25_to_flat","flat_to_up_25","up_25","up_25_to_flat","flat_to_up_25","left_vertical_loop","down_25_to_flat","flat_to_down_25","down_25","down_25_to_flat","flat_to_left_bank","banked_left_turn_5","banked_left_turn_5","left_bank_to_flat","flat_to_up_25","up_25","up_25","up_25","up_25_to_flat","flat_to_down_25","down_25","down_25","down_25","down_25_to_flat","right_corkscrew_up","right_corkscrew_down","flat_to_left_bank","banked_left_turn_5","banked_left_turn_5","left_bank_to_flat","f… (2397 chars)
  30. best_result
    {"bounds":{"max_tile_x":65,"max_tile_y":50,"max_z":392,"min_tile_x":16,"min_tile_y":36,"min_z":112},"placed_pieces":["begin_station","middle_station","middle_station","middle_station","end_station",{"chain":true,"t":"flat_to_up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25"},{"chain":true,"t":"up_25_to_flat"},"flat_to_down_25","down_25_to_down_60","down_60","down_60","down_60_to_down_25","down_25","down_25","down_25","down_25_to_flat","flat_to_up_25","up_25","up_25_to_flat","flat_to_up_25","left_vertical_loop","down_25_to_flat","flat_to_down_25","down_25","down_25_to_flat","flat_to_left_bank","banked_left_turn_5","banked_left_turn_5","left_bank_to_flat","flat_to_up_25","up_25","up_25","up_25","up_25_to_flat","flat_to_down_25","down_25","down_25","down_25","down_25_to_flat","right_corkscrew_up","right_corkscrew_down","flat_to_l… (2458 chars)
  31. Banked and confirmed. Three tested circuits this round (6.98, **7.00**, 6.91) — best is held. **Best coaster: a 94-piece steel twister — 272ft chain lift into a 32-unit triple-60° plunge, then 3 vertical loops + 2 corkscrews (5 inversions), a small up-helix turnaround and a run of airtime camelbacks home — excitement 7.00 (intensity 9.60, nausea 5.83, no crash, similarity 0.39).**