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What's new in 0.59

Hedron 0.59 is the modern CSS platform release. It keeps the 0.58 public markers and responsive defaults while adding explicit, opt-in capabilities for component-width layouts, theme variants, typed control attributes, logical overlay placement, print, and preference-aware presentation.

Highlights

  • CSS compiler format 2 with v1 manifest readers and stable v1 symbol hashing.
  • Grammar-aware nesting, conditional rules, local imports/assets, deterministic cascade layers, source maps, and diagnostic rejection of unsafe or ambiguous CSS.
  • Explicit Container(query="inline-size", name=...) boundaries and named markers.
  • Intrinsic and dynamic viewport sizing, logical layout, RTL/writing-mode paths, and Progressive subgrid alignment with Grid/FormGrid fallbacks.
  • Theme variants through StyleScope(variant=...), with additive output and validation.
  • Modern absolute-color parsing with canonical sRGB fallback, typography/content roles, and Progressive light-dark() / selected @property enhancements.
  • Typed Button / LinkButton size and width contracts plus safe ARIA/data/HTMX attributes.
  • Bounded popover placement/collision markers and CSS anchor-positioning enhancement hooks.
  • Native top-layer semantics, Progressive entry/exit and View Transitions, and Experimental decorative scroll-driven animation kept outside semantic state.
  • Print, dynamic viewport, safe-area, reduced-motion, contrast, forced-colors, transparency, hover, and pointer fallbacks in the default stylesheet.
  • Container/viewport-responsive AppShell chrome and provider-neutral pipeline, run-state, log, and operational-history presentation.
  • Static theme check, style explain, style preview, style diff, and zero-application-CSS checks with redacted, reviewable output.
  • Reproducible compiler, browser, performance, package, and Data Mover migration evidence.

Compatibility

Existing 0.58 classes, data-hedron-* markers, default theme behavior, viewport-responsive maps, and default_styles=False remain valid. New container behavior and theme variants are opt-in. Applications should review the upgrade guide and pin the published train with hedron>=0.59.0,<0.60.

The release packet remains truthful about evidence status in release-gate-0.59.toml.