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BrickWright gave coding agents a validator and a Python brick API, and physically valid LEGO builds went from 9% to 100%

AspireAI community · Carnegie Mellon University and Stanford University (arXiv)
Coding agents can already produce convincing 3D models, but the assemblies they invent routinely contain parts that float, collide or never connect. BrickWright, from Carnegie Mellon and Stanford researchers, tests the hypothesis that the fix is tooling rather than a better model: agents write Python against BrickLayer, a brick-assembly API that the authors say halves inference cost versus raw LDraw files, and a validator hands back feedback on physical feasibility until the build passes. On a sample of 512 prompts, baseline agents produced physically valid builds between 9% (GPT-6 Luna) and 69% (GPT-6 Astra) of the time, while BrickWright-guided agents reached 100% validity, and the guided agents also beat specialised text-to-brick models on the task. The limitation is the domain: 100% is measured on LEGO bricks with a validator that knows what a real part is, and it does not establish that the same approach generalises to materials or shapes without a checker.
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