Epoch AI tests whether models can spot mistakes in IKEA assembly

On 23 September 2026 Epoch AI published “Can AI Spot Mistakes in IKEA Assembly?” by Aiden Ament and Greg Burnham. Its Furniture Assembly Benchmark uses 60 photographs across three IKEA builds, some showing a correct assembly and some showing intentional mistakes.

Models receive the assembly manual and tools to inspect the image, including a zoom tool and a Python interpreter. To score, a model must identify every step that contains a mistake and describe it reasonably; if there is no mistake, it must say so.

Epoch bought three products and rates them with the IKEA Complexity Index, which multiplies the number of steps by the number of pieces: the STÄLL shoe rack scores 4,032, the TONSTAD bed frame 10,878 and the GULLABERG dresser 21,320. Epoch says it has not measured human performance, but expects many mistakes to be hard for someone who does not know the build.

Epoch reports that the best score in November 2025 was 28 percent, from Claude Opus 4.5. In September 2026 GPT-6 Astra leads at 80 percent, ahead of Claude Fable 5.1 at 70 percent and Claude Opus 5 at 61 percent in the initial leaderboard. Astra's median time of 3 minutes a photograph was the fastest Epoch tested, between twice and ten times as fast as previously leading models. Epoch says the leading model has always been closed-weight. Accuracy did not track the complexity index; Epoch suspects mistake subtlety, camera angle and building on past an error mattered more.

An agent may take up to 80 steps, a limit hit in under 5 percent of samples. Once a step is identified, a second model, GPT-5.6 Sol, grades the description and is prompted to be lenient. These are Epoch's measurements on Epoch's photographs, not a claim about IKEA products and not a test of robots assembling furniture.