Livenerf: Has Opus 5.5 been nerfed yet?
Livenerf is an open, pre-registered 30-day benchmark designed to test whether Claude Opus 5.5’s performance changes after launch, rather than treating user impressions as proof of a “nerf.”
It pins the prompts, graders, Claude Code CLI version, harness, and raw logs, and uses paired repeated questions plus a control model. The project was only six days into data collection when reviewed, so it has no result yet; its own validation says it can detect only fairly large changes, and it measures Opus through a Claude Code subscription—not the raw API model.
HN commenters pointed to an existing launch-day benchmark and emphasized the distinction between subscription/CLI serving and API access. Others cautioned that perceived regressions may be noise or a honeymoon effect. The authors’ main contribution so far is a transparent measurement protocol, not evidence that a change occurred.