BIP 77: Delimit fragment params with - instead of + #1890

1. 
   nothingmuch commented at 12:48 pm on July 5, 2025: contributor

   This PR addresses the concerns raised in #1885 with regards using + as a delimiter, by switching to -. Some URI libraries implement RFC 1866’s (HTML 2.0) “keyword” delimitation in query parameters by decoding + as unconditionally, which necessitates kludgy workarounds.

   Additionally fragment parameters must now ordered lexicographically (instead of reverse), the motivation for a canonical ordering was to reduce implementation fingerprinting concerns, but the reverse lexicographical ordering was specified simply because that was the behavior that was already implemented in PDK. Since that is somewhat surprising and the delimiter change breaks backwards compatibility anyway, the marginal cost in terms of compatibility of reducing the surprisingness of the reversed ordering is arguably zero, so this is also addressed here.

   cc @kumulynja

2. Separate fragment params with `-` instead of `+`

   Since only Bull Bitcoin Mobile and Cake wallet are currently deployed in
   production, both using PDK, and the `+` character is causing some
   friction, this change seems justified to avoid similar issues with
   future implementations.

   7ea6cfe64f
3. Specify lexicographical order for fragment params

   The rationale for this change is that since `-` instead of `+` breaks
   compatibility anyway, the marginal cost of removing this
   unusual/surprising requirement for reverse lexicographical ordering is
   zero.

   315dcc2252

Contributors
nothingmuch