The FIX Global Technical Committee has reviewed and approved the promotion of the FIX Performance Session Layer (FIXP) Version 1.0 Draft Standard to Technical Standard on April 15, 2021. The Technical Proposal and the Technical Specification can both be found here for download.
The Technical Specification for FIXP is maintained by the GTC in a public GitHub repository (https://github.com/FIXTradingCommunity/fixp-specification). Pull requests for V1.0 are now only accepted for errata. Work continues on FIXP V1.1 whereby the current Draft Standard is also available online.