Are open models catching up?

Are open models catching up? The best open-weight model vs the best closed model on our internal writing benchmark, by release date. An open model, Kimi K2, briefly took #1 in September 2025. The gap shrank to just 101 Elo in February. Then Claude Opus 5.5 blew it back open to 447. Still, the best open writer today, GLM-5.3, costs 30x less per script.