Release Announcement for Version 8.6

Racket v8.6

Racket version 8.6 is now available from

As of this release:

* Racket has an "equal-always?" primitive that equates values that will stay
  the same even if mutated. See

* This release uses a new build system, Zuo, which is implemented as a
  little language, in accordance with the ideas of Language Oriented
  Programming (LOP). The implementation has a single C file (plus libraries
  implemented in Zuo), so it compiles easily. The `zuo/build`
  library is modeled on `make` and Shake for tracking dependencies and
  build steps. See and

* Racket supports stencil vectors, which associate a virtual bitmask
  with a vector, enabling certain mask-equipped update operations. See

* Racket supports Arm64 machines running Windows.

* Redex has support for simultaneous substitutions. See

* The Web Server provides control over the maximum number of
  concurrent connections via its "safety limits" construct. See

* The Web Server has improved logging performance and improved
  request parsing performance, reducing tail latencies.

* The Web Server supports logging response status code via
  web-server/dispatchers/dispatch-logresp. See

* The `db` library supports custom types for PostgreSQL connections; see
  `pg-custom-type` for details. See

* The release includes many other repairs and changes!

The following people contributed to this release:

Alex Knauth, Alexander Shopov, Alexis King, Amirouche Amazigh BOUBEKKI,
Andy Keep, Ashish SHUKLA, Bob Burger, Bogdan Popa, Cameron Moy,
Chung-chieh Shan, David K. Storrs, FrankHB, Fred Fu, Gustavo Massaccesi,
helado de brownie, J. Ryan Stinnett, Jack Firth, Jamie Taylor, Jason
Hemann, Jens Axel Søgaard, Jimmy McNutt, Joel Dueck, John Clements, José
Manuel Calderón Trilla, Kevin Tew, Laurent Orseau, Matt Audesse, Matthew
Flatt, Matthias Felleisen, Mike Sperber, naveen srinivasan, Niklas
Larsson, Noah Ma, Oscar Waddell, Pavel Panchekha, Phil Nguyen, Philip
McGrath, Philippe Meunier, rgkirch, Robby Findler, Robert Postill, Ryan
Culpepper, Sam Tobin-Hochstadt, Sergiu Ivanov, Sorawee Porncharoenwase,
Stephen De Gabrielle, Vincent Lee, wackbyte, and Zibing Zhang

Link to package regressions issue for the 8.6 release: