`modern-web-guidance`: Chrome and Edge team up to stop your agent from coding like it's 2019

`modern-web-guidance` is an Apache 2.0 skill pack co-built by the Google Chrome and Microsoft Edge teams, released at Google I/O 2026, that injects 102 expert-vetted modern web platform recipes into your coding agent. Google's evals show a +37 percentage-point improvement in best-practice adherence for Claude Code; the article covers installation for all 9 supported agents, concrete before/after code comparisons, three documented community wins, and Adrian Roselli's critical test showing real WCAG and Firefox failures — plus clear guidance on when not to use it.