Just found that a CarpetContext has two extra parameters from a regular Context: source and origin, with source also containing a position.

Is there a difference between the source's position and the origin that makes it necessary to store both, or could it be changed to just store the source?

origin is only used for /script scan and related to interpret what a position is referring to (offsetting from origin parameter) nothing else

TBH, I would deprecate that in favour of always offsetting from 0,0,0, so a position in the script refers to the actual block in the world

After knowing what origin is in CarpetContext, this issue is no longer valid. Closing it, deprecation of origin changing should be tracked in a different issue.