Lantern: Re-evaluate metric coefficients on the 2026 golden trace dataset #17438

Summary

Lantern's static linear combination weights (intercept, optimistic, pessimistic) in FirstContentfulPaint, LargestContentfulPaint, SpeedIndex, and Interactive were originally tuned on the 2018/2019 HTTP/1.1 & HTTP/2 dataset:

• FirstContentfulPaint: intercept: 0, optimistic: 0.5, pessimistic: 0.5
• LargestContentfulPaint: intercept: 0, optimistic: 0.5, pessimistic: 0.5
• SpeedIndex: intercept: 0, optimistic: 1.4, pessimistic: 0.4
• Interactive: intercept: 0, optimistic: 0.45, pessimistic: 0.55

Next Steps

With the 2026 golden trace dataset (#17411), evaluate whether re-tuning these coefficients improves accuracy (MAPE, rank correlation, and bias) for modern HTTP/3 multiplexing and contemporary JS bundle patterns using the analysis tools in core/scripts/lantern/.