COASTERBENCH

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

claude-opus-5 excitement 7.39 intensity 9.18 nausea 4.88 length 744 m drops 15 airtime 116 pieces 107
Each round a model submits a track program. OpenRCT2 builds it, runs a test train, and returns ratings and a screenshot; the reported score is excitement.
model track program build + validate test train ratings + screenshot rejected piece

Pieces are placed through the same validated action path the game uses for player input, so an impossible curve or an open circuit fails as it would in-game. Intensity above 10 suppresses excitement, a crash disqualifies the ride, and designs close to the stock library scale toward zero. Ratings come from the game, not from a model. Modes: design — design mode — models build from scratch. library — library mode — models may search the stock track design library, which measures retrieval and adaptation; copies score zero. open note — a modifier on either mode — the agent is also given the engine source it is scored by, so it can read the ratings code instead of guessing; scores are not comparable with black-box runs.

All runs head to head →track design library →
filters
mode coaster harness model
run setup model score int / nau tokens / cost
best coaster of claude-opus-4-8 in 20260723-v2-library 20260723-v2-library2026-07-23 library · wooden · driver-api 1st claude-opus-4-8 8.43round 6/6 9.87 / 5.97
best coaster of claude-fable-5 in 20260723-v2-library 20260723-v2-library2026-07-23 library · wooden · driver-api 2nd claude-fable-5 7.53round 6/6 9.58 / 5.06
best coaster of claude-opus-5 in 20260725-opus5-opennote 20260725-opus5-opennote2026-07-25 design + open note · steel twister · claude-code 1st claude-opus-5 7.39round 6/6 9.18 / 4.88 286 in / 200k out · $7.91
best coaster of claude-opus-5 in 20260724-opus5-twister 20260724-opus5-twister2026-07-24 design · steel twister · claude-code 1st claude-opus-5 7.13round 4/6 10.17 / 6.24 403 in / 359k out · $12.67
best coaster of claude-opus-5 in 20260725-opus5-bash-probe 20260725-opus5-bash-probe2026-07-25 design · steel twister · claude-code 1st claude-opus-5 7.06round 1/2 10.07 / 6.14 191 in / 150k out · $5.82
best coaster of openrouter_moonshotai_kimi-k3 in 20260724-kimi-k3-twister 20260724-kimi-k3-twister2026-07-24 design · steel twister · opencode 1st openrouter_moonshotai_kimi-k3 7.05round 2/6 9.26 / 4.99 584k in / 321k out · $9.44
best coaster of claude-opus-5 in 20260725-opus5-blind 20260725-opus5-blind2026-07-25 design · steel twister · claude-code 1st claude-opus-5 7.02round 1/6 9.89 / 6.02 414 in / 334k out · $11.81
best coaster of claude-opus-5 in 20260725-opus5-python-probe 20260725-opus5-python-probe2026-07-25 design + open note · steel twister · claude-code 1st claude-opus-5 6.84round 1/2 9.76 / 5.67 165 in / 113k out · $6.55
best coaster of claude-fable-5 in 20260723-v2-design 20260723-v2-design2026-07-23 design · wooden · driver-api 1st claude-fable-5 6.73round 6/6 8.33 / 4.66
best coaster of claude-opus-4-8 in 20260724-opus48-twister 20260724-opus48-twister2026-07-24 design · steel twister · claude-code 1st claude-opus-4-8 6.67round 5/6 7.58 / 4.37 531 in / 382k out · $26.57
best coaster of claude-fable-5 in 20260723-showdown 20260723-showdown2026-07-23 design · wooden · driver-api 1st claude-fable-5 6.59round 6/6 8.22 / 4.55
best coaster of claude-opus-4-8 in 20260723-v2-design 20260723-v2-design2026-07-23 design · wooden · driver-api 2nd claude-opus-4-8 6.38round 6/6 8.79 / 5.01
best coaster of claude-sonnet-5 in 20260723-v2-library 20260723-v2-library2026-07-23 library · wooden · driver-api 3rd claude-sonnet-5 6.30round 6/6 8.29 / 4.62
best coaster of claude-sonnet-5 in 20260723-showdown 20260723-showdown2026-07-23 design · wooden · driver-api 2nd claude-sonnet-5 5.95round 6/6 7.49 / 4.12
best coaster of claude-opus-4-8 in 20260723-showdown 20260723-showdown2026-07-23 design · wooden · driver-api 3rd claude-opus-4-8 5.78round 3/6 7.28 / 4.11
best coaster of claude-sonnet-5 in 20260723-v2-design 20260723-v2-design2026-07-23 design · wooden · driver-api 3rd claude-sonnet-5 5.71round 6/6 7.11 / 3.89
best coaster of openrouter_moonshotai_kimi-k3 in 20260725-codex-kimi 20260725-codex-kimi2026-07-25 design + open note · steel twister · codex 1st openrouter_moonshotai_kimi-k3 0.57round 1/1 0.20 / 0.10 $1.23
best coaster of claude-opus-4-6 in 20260723-v3-twister-design 20260723-v3-twister-design2026-07-23 design · steel twister · driver-api 1st claude-opus-4-6 0.24round 1/6 0.07 / 0.03
best coaster of openrouter_openai_gpt-5-mini in 20260725-opencode-mini-control 20260725-opencode-mini-control2026-07-25 design + open note · steel twister · opencode 1st openrouter_openai_gpt-5-mini no successful coaster 28k in / 8k out · $0.04
best coaster of openrouter_openai_gpt-5-mini in 20260725-codex-smoke2 20260725-codex-smoke22026-07-25 design + open note · steel twister · codex 1st openrouter_openai_gpt-5-mini no successful coaster 2.0M in / 13k out · $0.10
best coaster of openrouter_openai_gpt-5-nano in 20260725-codex-smoke 20260725-codex-smoke2026-07-25 design + open note · steel twister · codex 1st openrouter_openai_gpt-5-nano no successful coaster 134k in / 4k out · $0.00
best coaster of openrouter_openai_gpt-5.1 in 20260725-codex-scored 20260725-codex-scored2026-07-25 design + open note · steel twister · codex 1st openrouter_openai_gpt-5.1 no successful coaster $1.56
best coaster of gpt-5.6-sol in 20260725-codex-oauth-probe 20260725-codex-oauth-probe2026-07-25 design + open note · steel twister · codex 1st gpt-5.6-sol no successful coaster $0.00
best coaster of claude-haiku-4-5 in 20260723-v3-twister-design 20260723-v3-twister-design2026-07-23 design · steel twister · driver-api 2nd claude-haiku-4-5 no successful coaster
best coaster of claude-sonnet-5 in 20260723-v3-twister-design 20260723-v3-twister-design2026-07-23 design · steel twister · driver-api 3rd claude-sonnet-5 no successful coaster
best coaster of claude-opus-4-6 in 20260722-224837 20260722-2248372026-07-22 design · wooden · driver-api 1st claude-opus-4-6 no successful coaster
best coaster of claude-sonnet-5 in 20260722-224837 20260722-2248372026-07-22 design · wooden · driver-api 2nd claude-sonnet-5 no successful coaster

not shown, incomplete or still running: 20260725-kimi-k3-fresh, 20260724-laguna-wooden, 20260723-sub-twister-1, 20260723-library