Opus 5 matches Fable 5 on software engineering (SWE-ECI 161) while cutting cost per task 20%

Latent Space (AINews)·high signal

Latent Space's AINews breakdown puts Claude Opus 5 at 159 on the Epoch Capabilities Index versus Fable 5's 161, but at SWE-ECI 161 the two are at parity on software engineering specifically. Artificial Analysis separately reported Opus 5 outperforming Fable 5 by nearly 150 Elo while reducing cost per task by 20%. Users flagged a 'FrontierCode anomaly' where medium reasoning effort beat high effort, hinting at evaluation instability worth watching.