BUG Type 3
This deduction assumes the puzzle has exactly one solution and that all earlier candidate removals were sound. BUG Type 3 begins with a verified BUG candidate structure and combines its guardian alternatives with other cells in a shared sector to make a subset-style restriction. The guardian alternatives act as a virtual slot; they are not ordinary independent subset cells.
What is BUG Type 3?
First identify the guardian candidate group whose complete removal would create the BUG state. In a shared sector, combine that guaranteed group with N−1 real cells so that the relevant candidate union has N digits. Count every actual cell once and keep the guardian cells distinct from ordinary subset members.
Type 3 combines the guaranteed guardian alternatives with a subset restriction in a shared sector. The alternatives together occupy one virtual slot; they are not ordinary independent subset cells. Add the required number of separate companion cells, count the candidate union exactly, and eliminate only from other eligible cells in that sector.
How to spot it
Verify the underlying BUG counts, identify the guardian alternatives, and then count the companion cells and digit union in their shared sector. Do not call three ordinary cells a Naked Pair or eliminate from a guardian cell using the ordinary outside-subset rule.
The logic
Uniqueness guarantees that at least one guardian alternative is true, so the group occupies one virtual slot in the combined restriction. The companion cells occupy the remaining slots. Candidates in the resulting digit union can be removed only from other eligible cells in the shared sector.