Post History

Another approach, suggested by ArtOfCode in chat, is to create a close reason for "graduated" sandbox posts.  When defining a close reason you can require a URL (this is what's used for duplicates), so the close notice on the sandbox post would include a link to the actual challenge and people wouldn't need to edit it in or dig around in comments looking for it.

As a practical matter, Challenges and Sandbox (and Q&A) currently all use the same tag set.  A category has a single tag set, and tag sets can't include other tag sets, so to add special tags to the sandbox only, we would have to break that connection among the categories.  Giving the sandbox its own tag set would have the following effects:

- you could add special "meta" tags (advantage)
- you would have to create other tags (like code-golf and math) separately in the sandbox -- they're not the same tags as the other categories even though they'd have the same names (disadvantage)
- a tag search (for, say, math) in Challenges would not return hits from Sandbox and vice-versa (this might be an advantage or a disadvantage)