CoasterBench
COASTERBENCH<br>A benchmark in which language models design roller coasters that RollerCoaster Tycoon 2 builds, tests, and rates.
Sevenfold Serpent<br>claude-fable-5<br>excitement 7.94<br>intensity 10.31<br>nausea 6.12<br>length 1369 m<br>drops 21<br>airtime 139<br>pieces 211
Each round a model submits a track program. OpenRCT2 builds it, runs a test train, and<br>returns ratings and a screenshot; the reported score is excitement .
model<br>track program
build<br>+ validate
test train
ratings<br>+ screenshot
rejected piece
Pieces are placed through the same validated action path the game uses for player input, so<br>an impossible curve or an open circuit fails as it would in-game. Intensity above 10 suppresses<br>excitement, a crash disqualifies the ride, and designs close to the stock library scale toward<br>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 — open-note condition — the agent is 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.<br>full protocol →
Filters<br>head to head →track design library →
filters
coaster<br>all<br>steel twister<br>wooden
harness<br>all<br>claude-code<br>codex<br>driver-api<br>opencode
model<br>all<br>claude-fable-5<br>claude-opus-4-8<br>claude-opus-5<br>claude-sonnet-5<br>gpt-5.6-sol<br>openrouter_deepseek_deepseek-v4-flash-0731<br>openrouter_moonshotai_kimi-k3<br>openrouter_thinkingmachines_inkling-small
No run matches those filters.
design — the benchmark
design mode — models build from scratch
steel twister
run<br>setup<br>model<br>score<br>int / nau<br>tokens / cost
20260803-fable5-design-full2026-08-03<br>steel twister · claude-code<br>1st claude-fable-5<br>7.94round 6/6
10.31 /<br>6.12<br>521 in / 395k out · $52.51
20260727-gpt56-sol-design-full2026-07-27<br>steel twister · codex<br>1st gpt-5.6-sol<br>7.81round 6/6
9.99 /<br>7.33<br>14.2M in / 98k out · $0.00
20260731-deepseek-v4-flash-design2026-07-31<br>steel twister · opencode<br>1st openrouter_deepseek_deepseek-v4-flash-0731<br>7.29round 6/6
9.33 /<br>4.89<br>2.4M in / 291k out · $0.41
20260728-kimi-k3-design-rerun2026-07-28<br>steel twister · opencode<br>1st openrouter_moonshotai_kimi-k3<br>7.24round 3/6
8.92 /<br>4.68<br>1.9M in / 300k out · $13.11
20260727-opus5-design-full2026-07-27<br>steel twister · claude-code<br>1st claude-opus-5<br>7.23round 6/6
9.52 /<br>5.11<br>407 in / 298k out · $11.78
20260801-inkling-small-design2026-08-01<br>steel twister · opencode<br>1st openrouter_thinkingmachines_inkling-small<br>no successful coaster<br>179k in / 111k out · $1.51
wooden
run<br>setup<br>model<br>score<br>int / nau<br>tokens / cost
20260723-v2-design2026-07-23<br>wooden · driver-api<br>1st claude-fable-5<br>6.73round 6/6
8.33 /<br>4.66
20260723-showdown2026-07-23<br>wooden · driver-api<br>1st claude-fable-5<br>6.59round 6/6
8.22 /<br>4.55
20260723-v2-design2026-07-23<br>wooden · driver-api<br>2nd claude-opus-4-8<br>6.38round 6/6
8.79 /<br>5.01
20260723-showdown2026-07-23<br>wooden · driver-api<br>2nd claude-sonnet-5<br>5.95round 6/6
7.49 /<br>4.12
20260723-showdown2026-07-23<br>wooden · driver-api<br>3rd claude-opus-4-8<br>5.78round 3/6
7.28 /<br>4.11
20260723-v2-design2026-07-23<br>wooden · driver-api<br>3rd claude-sonnet-5<br>5.71round 6/6
7.11 /<br>3.89
library
library mode — models may search the stock track design library, which measures retrieval and adaptation; copies score zero
steel twister
run<br>setup<br>model<br>score<br>int / nau<br>tokens / cost
20260724-opus5-twister2026-07-24<br>steel twister · claude-code<br>1st claude-opus-5<br>7.13round 4/6
10.17 /<br>6.24<br>403 in / 359k out · $12.67
20260724-kimi-k3-twister2026-07-24<br>steel twister · opencode<br>1st openrouter_moonshotai_kimi-k3<br>7.05round 2/6
9.26 /<br>4.99<br>584k in / 321k out · $9.44
20260725-opus5-blind2026-07-25<br>steel twister · claude-code<br>1st claude-opus-5<br>7.02round 1/6
9.89 /<br>6.02<br>414 in / 334k out · $11.81
20260724-opus48-twister2026-07-24<br>steel twister · claude-code<br>1st claude-opus-4-8<br>6.67round 5/6
7.58 /<br>4.37<br>531 in / 382k out · $26.57
wooden
run<br>setup<br>model<br>score<br>int / nau<br>tokens / cost
20260723-v2-library2026-07-23<br>wooden · driver-api<br>1st claude-opus-4-8<br>8.43round 6/6
9.87 /<br>5.97
20260723-v2-library2026-07-23<br>wooden · driver-api<br>2nd claude-fable-5<br>7.53round 6/6
9.58 /<br>5.06
20260723-v2-library2026-07-23<br>wooden · driver-api<br>3rd claude-sonnet-5<br>6.30round 6/6
8.29 /<br>4.62
library + open note
open-note condition — the agent is 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
run<br>setup<br>model<br>score<br>int / nau<br>tokens / cost
20260725-opus5-opennote2026-07-25<br>steel twister · claude-code<br>1st claude-opus-5<br>7.39round 6/6
9.18 /<br>4.88<br>286 in / 200k out · $7.91