- Elements without a namespace (such as div) are no longer unified with elements with the empty namespace (such as |div). This unification didn't match the results returned by is-superselector(), and was not guaranteed to be valid.
- The Sass logger is now instantiated on a per-thread/per-fiber basis and can now be configured to output to any IO object. This can help services and processes that wrap Sass compilation reliably extract warnings in a concurrent environment.
- Setting the numeric precision by assigning to Sass::Script::Value::Number.precision is now thread safe. To set for all threads, be sure to set the precision on the main thread.
- Sass cache files will now be world and group writable if your umask allows it. Issue #1623
- The supports(...) clause in @import statements now allows bare declarations as per the CSS specification. Issue #1967
- Fix a bug where, under some circumstances, str-slice() would go to the end of the string even if $end-at was set.
- Fix conversions between numbers with dpi, dpcm, and dppx units. Previously these conversions were inverted.
- Support url()s containing quoted strings within unknown directives.