I’ve added an implementation allowing the spender to choose a SIGHASH mode at spend time. It’s unaudited, so use with caution. It is not meant to replace other plans of sighash modes, like the disconnect method in check_sig_verify Do not directly expose check_sig_verify jet · Issue #66 · BlockstreamResearch/SimplicityHL · GitHub
Posted as a starting point. In future, hopefully it can get audited and used in programs.