livenerf pins CLI version, freezes prompts, and runs 90-sample panels daily to statistically measure whether Claude Opus 5.5 drifts post-launch—detecting ~7.5 point accuracy changes per 10-day window.
Summary
Developers have had no objective baseline to verify whether model behavior changes after deployment. This append-only benchmark replaces anecdotal reports with timestamped statistical evidence, useful for anyone relying on consistent model performance in production.
Why it matters
Developers have had no objective baseline to verify whether model behavior changes after deployment. This append-only benchmark replaces anecdotal reports with timestamped statistical evidence, useful for anyone relying on consistent model performance in production.
Implementation verdict
Not a drop-in replacement for your evals—it's infrastructure for long-term monitoring of a specific model. Requires Max subscription, Claude Code CLI, Python 3.11+, and 30 days to collect baseline. Worth running now if you depend on Opus 5.5 and need to distinguish actual regressions from noise, but the first actionable results land after day 20.
Sources
Dev Signal
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