Tech Report: Add experimental soft navigation Core Web Vitals metrics #1372

Overview

Starting with the September 2026 release of the Chrome User Experience Report (CrUX) (announcement on web.dev), new experimental Core Web Vitals metrics that include soft navigations for Single-Page Applications (SPAs) are now available in BigQuery (country_summary and device_summary).

This tracking issue covers extending the HTTP Archive Technology Report end-to-end to support these new metrics using the CrUX-aligned _sn suffix convention.

Metrics Added

• experimental_largest_contentful_paint_with_softnavs (LCP_sn / fast_lcp_sn, p75_lcp_sn)
• experimental_cumulative_layout_shift_with_softnavs (CLS_sn / fast_cls_sn, p75_cls_sn)
• experimental_interaction_to_next_paint_with_softnavs (INP_sn / fast_inp_sn, p75_inp_sn)
• Good Core Web Vitals (with soft navs) (overall_sn / origins_with_good_cwv_sn)

End-to-End Pipeline Scope

1. BigQuery (Dataform):
   • Ingest soft nav fields (fast_lcp_sn, fast_cls_sn, fast_inp_sn, etc.) in reports.tech_crux.
   • Calculate origin-level passing rates for each soft nav metric and overall CWV (soft navs): origins_with_good_*_sn, origins_with_any_*_sn, origins_eligible_for_cwv_sn, pct_eligible_origins_with_good_cwv_sn.
   • Update reports.tech_report_core_web_vitals and GET_VITALS mapping to include overall_sn, LCP_sn, CLS_sn, and INP_sn.
2. BigQuery Export & Firestore:
   • Stream updated vitals documents into Firestore (core_web_vitals collection).
3. API (tech-report-apis):
   • Serve new vitals metrics via /v1/cwv.
   • Update /v1/cwv-distribution with lcp_sn_origins, inp_sn_origins, and cls_sn_origins origin counts from p75_*_sn.
4. Tech Report Frontend (httparchive.org):
   • Update techreport.json with metric definitions, thresholds, dropdown options, and labels using _sn identifiers.
   • Support soft nav metrics across Drilldown and Comparison timeseries charts/tables, Geographic Breakdown, and Histograms (cwvDistribution.js, geoBreakdown.js).

Related PRs

• Dataform: feat(reports): add experimental soft navigation Core Web Vitals metrics dataform#365
• API (tech-report-apis): feat(report-api): add soft navigation metrics to CWV distribution query tech-report-apis#168
• Frontend (httparchive.org): feat(techreport): add experimental soft navigation Core Web Vitals #1373