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A small model solved nearly three in ten ARC-AGI-1 puzzles without writing out its steps
BDH-CQ updates a fixed-size internal memory instead of generating chain-of-thought tokens, and its authors put a single puzzle query at about $0.00070. Two outside researchers say the result does not yet credit the design.
The Scientist · Science desk

What happened
- A small experimental model called BDH-CQ solved nearly three in 10 puzzles on the public ARC-AGI-1 evaluation set when given two attempts, its authors report.
- Rather than keeping the worked examples in front of it, the model folds each one into a fixed-size memory that does not grow as more examples arrive.
- Performance split by task type: the model handled some puzzles that turn or move shapes, and had more trouble with colour changes and certain combinations of rules.
- The paper describing the model was submitted to arXiv.org on August 10 and has not been peer-reviewed.
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Why it matters
- capability If the intermediate work lives in a state of fixed size, the compute a single attempt consumes stops growing with how many words the model produces on the way to the answer.
- contradiction Deng's assessment splits the cost saving from any claim about the design, so the cheap per-query figure leaves open whether the memory or the training did it.
- constraint Because Geiping says the model was built for ARC-style problems, an operator has no like-for-like comparison with a general-purpose system it might replace.
- exposure Teams that debug models by reading the written trace lose that artifact here, and Deng notes the trace was never a guaranteed record of how an answer was reached.
The design point is what happens to the examples. ARC-AGI-1 hands a model a few demonstration pairs, asks it to infer the visual rule, then apply that rule to a new puzzle [5]. BDH-CQ uses each example to update a fixed-size memory, and that memory stays the same size as more examples arrive, so the model does not keep going back through everything it has already seen [4].
Zuzanna Stamirowska, a complexity scientist and CEO of the AI company Pathway, is one of the authors [9]. "Once the query arrives, the model doesn't write out its thinking in words at all," she said [7]. "Nothing in between ever converts into language," she said [8].
The team puts one puzzle query at about $0.00070 and calls that roughly one-eleventh of what GPT-5.6 Luna costs on the same benchmark, while noting that the two costs were calculated differently [10]. Multiply back and the comparison implies about $0.0077 a query for Luna [11]. Since the two figures came from different methods, the eleven-fold gap is an estimate of relative cost, not the same measurement made twice.
Nearly three in 10 solved with two attempts also means roughly seven in 10 puzzles went unsolved [12]. The misses cluster. Colour changes and certain combinations of rules gave the model more trouble than tasks that turned or moved a shape [13]. On harder ordering and nesting puzzles, it did better after it had seen an example of similar difficulty [14].
Yuntian Deng, a computer scientist at the University of Waterloo, called the finding "an interesting efficiency result" and said it does not show that BDH-CQ's underlying architecture is better than other approaches [15]. Deng said specialized small models like BDH-CQ are a promising route to efficient reasoning, adding that more testing is needed to separate the effects of the model's design from how it was trained [16]. That separation is the whole question behind the cheap per-query figure, and one benchmark run with two attempts does not perform it.
Jonas Geiping, a machine learning researcher at the ELLIS Institute Tuebingen and the Max Planck Institute for Intelligent Systems, said BDH-CQ was built specifically for ARC-style problems, which makes it hard to compare directly with general-purpose systems [18]. He called the approach "neat" and noted that it can take on test problems without retraining [18].
Deng also flagged the inspection cost. Without written-out reasoning the model is harder to examine, he said, though he added that even a written chain of thought may not faithfully show how a model reached its answer [17]. "Human language is useful for communicating reasoning, but it need not be the most efficient representation for every intermediate computation," Deng said [19].
What to watch
- An ablation that separates the fixed-size memory from the training recipe, the test Deng says is still needed.
- A replication on the private ARC-AGI-1 evaluation set, and peer review of the arXiv paper.
- A cost comparison in which BDH-CQ's and a general-purpose model's per-query figures are computed the same way.