Hello CYQK,
A rigger whom I respect and trust does not ascend using the halyard on the boat. His solution is to stitch his choice of climbing line to the end of the halyard and pull his trusted line through the turning blocks at the top of the mast. Once the end of his line is in hand at deck level again he ties it off, ties the other part of that line as needed, and climbs entirely on his own line. Of course there will be some differences in the technique depending on the type of climbing equipment you have chosen, but the use of one's own line is the key issue. Once the project is completed he unties his line and pulls it and the original halyard back to the beginning position and removes the stitching to free the end of his line from the halyard.
I have seen this process done, but, sadly, I have none of the pictures that SBO members love!