Comment by surround

Here's a list of browser features the skills will tell your agent to use that are stable in Chrome but not supported by Firefox and Safari:

  CSS @function
  CSS calc-size()
  CSS interpolate-size
  CSS corner-shape
  CSS border-shape
  CSS flex-wrap: balance
  CSS text-fit
  CSS text-decoration-skip-spaces
  CSS scroll-axis-lock
  CSS scroll-target-group
  CSS :target-current
  CSS scroll-initial-target
  CSS container scroll-state queries
  scrollsnapchange event
  scrollsnapchanging event
  HTML focusgroup
  Element.startViewTransition()
  CSS view-transition-scope
  Interest Invokers (interestfor)
  LanguageModel (Prompt API)
  LanguageDetector
  Translator
  Summarizer API
  Window.fetchLater()
  Speculation Rules API
  Long Animation Frames API
  VisibilityStateEntry
  PerformanceSoftNavigation
  InteractionContentfulPaint
  Connection-Allowlist
  CSS url() integrity() modifier
  HTML meta name="text-scale"
  HTML template for
  HTML processing instructions
  PasswordCredential
  Promise-returning scroll methods
  Web App Origin Migration
  Local Network Access permissions
  Request.targetAddressSpace
  beforeinstallprompt event

To be fair, the skills also recommend ~11 features not supported by Chrome itself. And the project does seem concerned with compatibility: "Guiding models to use sensible, lightweight fallbacks."