SpaceChem Bench: No Stomach for Lunch

research_3 Hard Bonding & routing Single-reactor Atropos Station · SpaceChem Bench report →

Inputs: α Ethane (C2H6). Output: ψ Ethylene (C2H4) ×10, ω Hydrogen (H2) ×10. Features: Bonders (2).

In SpaceChem Bench, 16 LLMs each had one attempt at this SpaceChem puzzle, with 60 minutes to build a working solution and keep optimizing it, without seeing the community archive. 9 of 16 models solved it. No model found a new Pareto-frontier point beyond the frozen community archive.

9 / 16models solved it
151best LLM cycles (132 community)
0new frontier points

Records

ScoreCommunity bestBest LLMModel
Cycles132151Opus 5.5 · +14%
Reactors11Fable 5.1 Ties record
Symbols1722GPT-6 Astra · +29%

Community records from the community archive when we froze it on October 18, 2026. A point counts only after fresh-game replay and SChem’s precognition check.

Pareto frontier

Pareto explorer

Lower is better ↙
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Community archiveModel frontier pointNew frontier point
Select a point with the mouse or keyboard to inspect its scores and reactor blueprint.

Search over time

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Every model

ModelSolvedBest cyclesBest reactorsBest symbolsNew frontier points
01Opus 5.5Yes151123—
02GPT-6 AstraYes185122—
03Gemini 4 ArgonYes236123—
04Fable 5.1Yes256132—
05Sonnet 5.5Yes262129—
06Kimi K3.1 ProYes263139—
07GPT-6.1 SolYes284122—
08Haiku 5.5Yes287138—
09Gemini 3.8 FlashYes374133—
10DeepSeek V4.1 FlashNo————
11GLM-5.3No————
12GPT-6 LunaNo————
13Grok 4.7No————
14MiMo-V2.6-ProNo————
15Muse Spark 1.3No————
16Muse Wonder 1.0No————

Best scores can come from different solutions. New frontier points are not matched or beaten on all three scores by any community solution.

Best model solutions

These solutions are in SpaceChem Community Edition export format and released under the MIT License. All of this puzzle’s model solutions are on GitHub and Hugging Face.

Opus 5.5 Fewest cyclesFewest reactors

151 cycles · 1 reactor · 24 symbolsresearch_3.151-1-24.txt on GitHub

Layout

α β ψ ω 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 ↓ → ← ↑ ↓ → → ↑ ↓ ← S← S↓ IN α GRAB OUT ψ SYNC DROP B− CCW B+ GRAB B+ SYNC OUT ω DROP B−

Running in the game

Opus 5.5 solution running on research_3 in SpaceChem
SpaceChem Community Edition export (research_3.151-1-24.txt)
SOLUTION:No Stomach for Lunch,Player,0-0-0
COMPONENT:'drag-reduced-reactor',2,0,''
MEMBER:'instr-start',180,0,128,4,0,0,0
MEMBER:'instr-start',90,0,32,5,3,0,0
MEMBER:'feature-bonder',-1,0,1,6,1,0,0
MEMBER:'feature-bonder',-1,0,1,6,2,0,0
MEMBER:'instr-arrow',90,0,64,3,0,0,0
MEMBER:'instr-arrow',0,0,64,3,2,0,0
MEMBER:'instr-arrow',180,0,64,8,0,0,0
MEMBER:'instr-arrow',-90,0,64,8,2,0,0
MEMBER:'instr-input',-1,0,128,3,0,0,0
MEMBER:'instr-grab',-1,1,128,3,1,0,0
MEMBER:'instr-output',-1,0,128,5,0,0,0
MEMBER:'instr-sync',-1,0,128,5,2,0,0
MEMBER:'instr-grab',-1,2,128,6,0,0,0
MEMBER:'instr-bond',-1,1,128,7,2,0,0
MEMBER:'instr-rotate',-1,1,128,8,2,0,0
MEMBER:'instr-arrow',90,0,16,5,2,0,0
MEMBER:'instr-arrow',0,0,16,5,5,0,0
MEMBER:'instr-arrow',0,0,16,6,1,0,0
MEMBER:'instr-arrow',-90,0,16,6,5,0,0
MEMBER:'instr-arrow',90,0,16,7,1,0,0
MEMBER:'instr-arrow',180,0,16,7,2,0,0
MEMBER:'instr-bond',-1,0,32,5,4,0,0
MEMBER:'instr-grab',-1,1,32,6,1,0,0
MEMBER:'instr-bond',-1,0,32,6,2,0,0
MEMBER:'instr-sync',-1,0,32,6,3,0,0
MEMBER:'instr-output',-1,1,32,6,4,0,0
MEMBER:'instr-grab',-1,2,32,6,5,0,0
MEMBER:'instr-bond',-1,1,32,7,1,0,0

GPT-6.1 Sol Fewest symbols

295 cycles · 1 reactor · 22 symbolsresearch_3.295-1-22.txt on GitHub

Layout

α β ψ ω 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 ↓ → ↓ → ← ↑ ← ↑ ↓ ↑ S← S↑ CCW IN α GRAB CW B+ OUT ω B− B+ B− OUT ψ DROP G/D

Running in the game

GPT-6.1 Sol solution running on research_3 in SpaceChem
SpaceChem Community Edition export (research_3.295-1-22.txt)
SOLUTION:No Stomach for Lunch,Player,0-0-0
COMPONENT:'drag-reduced-reactor',2,0,''
MEMBER:'instr-start',180,0,128,2,0,0,0
MEMBER:'instr-start',-90,0,32,6,3,0,0
MEMBER:'feature-bonder',-1,0,1,6,4,0,0
MEMBER:'feature-bonder',-1,0,1,6,5,0,0
MEMBER:'instr-arrow',90,0,64,1,0,0,0
MEMBER:'instr-arrow',0,0,64,1,5,0,0
MEMBER:'instr-arrow',90,0,64,2,3,0,0
MEMBER:'instr-arrow',0,0,64,2,4,0,0
MEMBER:'instr-arrow',180,0,64,5,3,0,0
MEMBER:'instr-arrow',-90,0,64,5,5,0,0
MEMBER:'instr-arrow',180,0,64,6,0,0,0
MEMBER:'instr-arrow',-90,0,64,6,4,0,0
MEMBER:'instr-input',-1,0,128,1,0,0,0
MEMBER:'instr-grab',-1,1,128,1,2,0,0
MEMBER:'instr-rotate',-1,0,128,1,3,0,0
MEMBER:'instr-bond',-1,0,128,2,4,0,0
MEMBER:'instr-output',-1,1,128,3,4,0,0
MEMBER:'instr-bond',-1,1,128,5,3,0,0
MEMBER:'instr-bond',-1,0,128,5,4,0,0
MEMBER:'instr-bond',-1,1,128,5,5,0,0
MEMBER:'instr-output',-1,0,128,6,1,0,0
MEMBER:'instr-grab',-1,2,128,6,2,0,0
MEMBER:'instr-rotate',-1,1,128,6,3,0,0
MEMBER:'instr-arrow',90,0,16,6,1,0,0
MEMBER:'instr-arrow',-90,0,16,6,4,0,0
MEMBER:'instr-grab',-1,0,32,6,4,0,0