GoKawiilNew 'livenerf' benchmark tracks whether Anthropic's Claude Opus 5.5 degrades after launch
An open-source project called livenerf has begun a 30-day daily benchmark of Claude Opus 5.5, which launched September 22, 2026, to test long-standing claims that Anthropic quietly degrades models after release. As of September 29, the project has collected 6 of 10 baseline days using a fixed harness, pinned CLI version, and a panel of 2,336 GPQA Diamond and MMLU-Pro questions, with no missed days so far. The first statistical comparison window won't be possible until around October 24, 2026.