Packages can now use the publishConfig.executableFiles field in their manifests to indicate which files should keep the executable flag once packed in the archive. This is important as for portability reasons Yarn strips the executable flag from all files during packing (otherwise yarn pack would yield different outputs when run on Posix vs Windows). Files listed in the bin field are assumed executable by default, so you don't need to explicitly list them in executableFiles.

Requests won't timeout anymore as long as the server is still sending data.
yarn pack will properly include main/module/bin files, even when not explicitly referenced through the files field.
Local git repositories can now be fetched via the git+file: protocol.
The progress bars will be properly styled when using the new Windows terminal on certain days.
Yarn will now avoid using deprecated versions of the dependencies, unless only deprecated versions are available for the requested ranges.
Build keys are now properly computed, which fixes issues where build scripts weren't always triggered when they should have been.
Negated glob patterns in the workspace field will now be processed correctly.
Yarn will now allow relative paths inside the workspace: protocol to start with ./
Yarn will now show the actual error when it fails to resolve a request during yarn add and yarn up
The portable shell will now support calling cd and exit without arguments
Yarn will now show the exit code when a lifecycle script fails
Yarn's portable shell will now also pipe the stderr when using the |& pipeline
Yarn's portable shell will now respect the left associativity of list operators

Yarn will now report an error when run through an incompatible Node version.
yarn add and yarn up will now respect the preferInteractive configuration option.
yarn config set now supports the -H,--home flag, which causes it to update the home configuration instead of the project configuration.

The settings found in the home configuration file won't cause exceptions when consumed by older Yarn versions. Unsupported options will simply be silently ignored. This should improve the user experience when working with multiple projects configured with different Yarn versions.
A new immutablePaths setting allow you to specify paths that must not change when running Yarn with the --immutable flag set. You can use it to detect unforeseen changes to your install artifacts, be it .pnp.js or node_modules files.

Scripts can now use the $RANDOM variable as well as simple calculations using +, -, *, / and () inside $(())
Scripts can now use grouping curly braces ({echo foo}) to execute a command in the context of the current shell (without creating a subshell like in the case of (echo foo)).
Scripts can now end with a semicolon.
PnP linker will not remove lingering node_modules inside folders matching pnpIgnorePatterns

The PnP hook will now display clearer error message when requiring Node builtins from contexts that can't access them out of the box (for example when accessing the fs module from within a Webpack browser bundle).