This is somewhat the opposite of #87187 and the acknowledgement that computing additional text edits for all items upfront is too demanding. This issue is only about additionalTextEdits and the goal is a pragmatic solution, similar to the one that we have for format on type. Idea

• accept an unresolved completion
• proceed with insertion as usual
• set up a content change listener
• resolve the items
• once resolved check if additional edits overlap with "concurrent" changes. when they overlap, do nothing otherwise proceed