(This post is part of the Genuinely Approachable Sudoku (GAS) series.)
The sum constraint insanity continues. When, across these Serbian Frames and XxVx Pairs puzzles, can we agree to just put the normal representation of sum values directly on the edges of the added cells? Maybe those comments to simplify Sudoku variations are for another day; enjoy thinking about all the VII and XII values today!

PDF

or solve online (using SudokuPad)

Author/Opus: This is the 67th puzzle from Clover, part of the Genuinely Approachable Sudoku (GAS) team.

Rules: Standard Sudoku rules (insert a number from 1 to 9 into each cell so that no number repeats in any row, column, or bold region). Whenever an XII or VII, reflecting the numbers 12 or 7 in Roman numerals, is placed on the edge between cells, the numbers in the two adjacent cells must sum to exactly 12 or 7. (Pairs of cells without an XII or VII can have any sum value.)

GAS Time Standards (highlight to view): Two party hats (🎩🥳): 7:30; One party hat (🥳): 14:00. All other solvers earn a 🦕: moderate Metriacanthosaurus.

Thomas Hits the GAS (highlight to view): 3:43, with SudokuPad replay file shared as a download for now (requires loading via settings menu with improvements expected before people should use this regularly).

Solution: PDF; solving video with explanation to be added later from GAS team.

Note: Follow this link for other less common variations of Sudoku.

Note 2: Comments on the blog are great! For a more interactive discussion, please also consider using our Daily GAS discussion post on the GMPuzzles Discord. Not a member of the Discord? Click this link for basic access.