Proof of Graffiti conjecture 262

Official summary of the Intelligence Index result, with pricing and cache-read changes.

Short proofs for six Graffiti conjectures (198, 219, 252, 254, 584 and 712) written with Opus 5.5 and GPT-6.1 Sol.

Coding tests of Sol released two days after Sonnet 5.5, noting the odd behaviours seen while building with it.

Follow-up head-to-head with the creator reporting a clear winner after repeated trials.