Ask HN: What was the last task where only a frontier model could do it?

ive been seeing a recurring claim that open (weight) models 6 months behind the frontier are good enough for the majority of ‘work’. if you've had a concrete task in the last month where GLM/DeepSeek/Kimi/Qwen failed and Opus/Fable/GPT succeeded (or vice versa!), please share

Ill provide a template as ive also frequently seen posters complain about a lack of context: - task (short and specific) - cheap model tried & how it failed - frontier model & did it actually succeed - would frontier-1